1. science
2. physics

High-resolution, vacuum-ultraviolet absorption spectrum of boron trifluoride
Patrick P. Hughes,1 Amy Beasten,2 Jacob C. McComb,2 Michael A. Coplan,3 Mohamad Al-Sheikhly,2 Alan K.
Thompson,1 Robert E. Vest,1 Matthew K. Sprague,1 Karl K. Irikura,1 and Charles W. Clark1, 3, 4
1)
National Institute of Standards and Technology, Gaithersburg, Maryland, 20899, USA
Nuclear Engineering Program, University of Maryland, College Park, Maryland, 20742, USA
3)
Institute for Physical Science and Technology, University of Maryland, College Park, Maryland, 20742, USA
4)
Joint Quantum Institute, National Institute of Standards and Technology and University of Maryland,
Gaithersburg, Maryland, 20899, USA
2)
arXiv:1410.4737v1 [physics.atom-ph] 17 Oct 2014
(Dated: 20 October 2014)
In the course of investigations of thermal neutron detection based on mixtures of 10 BF3 with other gases,
knowledge was required of the photoabsorption cross sections of 10 BF3 for wavelengths between 135 and
205 nm. Large discrepancies in the values reported in existing literature led to the absolute measurements
reported in this communication. The measurements were made at the SURF III synchrotron radiation facility
at the National Institute of Standards and Technology. The measured absorption cross sections vary from
10−20 cm2 at 135 nm to less than 10−21 cm2 in the region from 165 to 205 nm. Three previously unreported
absorption features with resolvable structure were found in the regions 135 to 145 nm, 150 to 165 nm and 190
to 205 nm. Quantum mechanical calculations, using the TD-B3LYP/aug-cc-pVDZ variant of time-dependent
density functional theory implemented in Gaussian 09, suggest that the observed absorption features arise
from symmetry-changing adiabatic transitions.
I.
INTRODUCTION
Boron-10 trifluouride, 10 BF3 , was first used in a neutron detector by Amaldi et al.,1,2 and for many years,
until the availability of 3 He, it was commonly used in
gaseous proportional counters to detect thermal neutrons. The advantage of 10 BF3 as a neutron detection
medium is based on its relatively large thermal neutron
capture cross-section, σth = 3840 b (3.84 × 10−21 cm2 ),
for the reactions:
10
B + n → 7 Li + α + 2.792 MeV,
10
B + n → 7 Li∗ + α + 2.310 MeV,
7 ∗
Li → 7 Li + γ (0.482 MeV)
(1)
(2)
(3)
Eq. (2) describes the major reaction branch with a
branching ratio of 94%.3,4 It is followed by prompt
gamma emission according to Eq. (3)
In traditional BF3 proportional counters, the energetic
products of the reactions in Eqs. (1) and (2) precipitate
a cascade of gas ionization in applied electric fields of
approximately 100 kV/m. The charged particles are then
collected as a current pulse. In contrast, we aim to build
a detector similar to that described in Hughes et al.,5
in which 3 He was mixed with various noble gases and
irradiated with cold neutrons to produce the reaction:
3
He + n →3 H + p + 0.765 MeV.
(4)
As the reaction products in Eq. 4 deposit energy in the
surrounding noble gas, excimers are produced. The excimers are loosely bound noble gas diatomic molecules
that exist only in excited electronic states. Noble gas excimers decay by emission of vacuum ultraviolet (VUV)
radiation that can be detected as a signature of neutron
absorption. Hughes et al.5 found that tens of thousands
of excimer VUV photons were generated per absorbed
neutron, and in some cases approximately 30 % of the net
nuclear reaction energy was channeled into VUV emissions by this process. McComb et al.6 found that around
ten thousand VUV excimer photons could be generated
per absorbed neutron for neutrons incident upon a thin
film of boron in a noble gas near atmospheric pressure.
The success of these experiments was contingent upon the
transparency of the heavy noble gases to their own excimer radiation. The measurements described here were
motivated by concerns about VUV absorption by BF3 ,
which if sufficiently strong would disqualify BF3 as a substitute for 3 He in the arrangement described in Ref. 5.
II.
MEASUREMENTS
Measurements of the absolute photoabsorption cross
section of BF3 were performed on beamline 4 (BL-4)7
of the Synchrotron Ultraviolet Radiation Facility (SURF
III) at the National Institute of Standards and Technology (NIST). The the gas handling system is shown in Fig.
2 and optical system used to perform these measurements
is shown in Fig. 2.
A.
Handling of the BF3 sample
Due to the hazards of the sample gas, several remarks
are in order. Boron has two stable isotopes, of mass
number 10 and 11, with relative terrestrial abundances
of approximately 19.9 % and 80.1 %, respectively.8 Only
10
B absorbs low energy neutrons, thus BF3 gas enriched
in 10 B to 99.60±0.01 % by weight was used for these measurements. This sample had miscellaneous impurities of
approximately 0.01 %, according to the supplier’s assay.9
BF3 is non-flammable; has a pungent, suffocating odor;
and is a major inhalation and contact hazard with a toxicity threshold of 0.0001 %. It reacts with most metals
Latest results of MEG and status of MEG-II
Francesco Renga1 [for the MEG Collaboration]
1
INFN - Sez. di Roma, P.le A. Moro 2, 00185 Roma, Italy
arXiv:1410.4705v1 [hep-ex] 17 Oct 2014
DOI: will be assigned
Within the Standard Model, in spite of neutrino oscillations, the flavor of charged leptons
is conserved in very good approximation, and therefore charged Lepton Flavor Violation
is expected to be unobservable. On the other hand, most new physics models predict
charged Lepton Flavor Violation within the experimental reach, and processes like the
µ → eγ decay became standard probes for physics beyond the Standard model. The MEG
experiment, at the Paul Scherrer Institute (Switzerland), searches for the µ → eγ decay,
down to a Branching Ratio of about 5 × 10−13 , exploiting the most intense continuous
muon beam in the world and innovative detectors. In this talk I will present the latest
results from MEG, and the status of its upgrade (MEG-II), aiming at an improvement of
the sensitivity by one order of magnitude within this decade.
1
Introduction
Charged lepton flavor conservation is an accidental symmetry in the standard model (SM),
not related to the gauge structure of the theory, but following from the particle content of
the model. As a consequence, this conservation is naturally violated in most of the extensions
of the standard model. Indeed, LFV in the charged lepton sector (cLFV) is expected in the
SM due to neutrino oscillations, but the expected branching ratios for LFV decays (< 10−40 )
are predicted to be well below the current experimental sensitivities. Hence, an observation of
cLFV would be an unambiguous evidence of new physics (NP) beyond the SM.
Among the NP models predicting cLFV at observable levels, Supersymmetry (SUSY) is of
particular interest: even if the theory is developed to be flavor blind at the high energy scale,
cLFV arises at the electroweak scale through renormalization group equations, and hence it is
essentially unavoidable. Moreover, many SUSY models predict a strong correlation between
cLFV and the possible deviation of the muon g − 2 from its SM prediction. Anyway, the
expected branching ratios strongly depend on the specific flavor structure of the model. Recent
limits on µ → eγ already rule out several scenarios still allowed by direct searches at LHC but
nonetheless, even within the same models, a different flavor structure can predict rates not yet
explored, and within the reach of the next generation of cLFV experiments (see [1] for a specific
model with flavored gauge mediation).
I will report here the latest results for the search of µ → eγ with the MEG experiment, and
the status of its upgrade MEG-II.
PANIC14
1
Introducing TAXI: a Transportable Array for eXtremely
large area Instrumentation studies
T. Karg∗ , A. Haungs† , M. Kleifges∗∗ , R. Nahnhauer∗ and K.-H. Sulanke∗
arXiv:1410.4685v1 [astro-ph.IM] 17 Oct 2014
∗
DESY, Zeuthen, Germany
Karlsruhe Institute of Technology, Institut für Kernphysik, Karlsruhe, Germany
∗∗
Karlsruhe Institute of Technology, Institut für Prozessdatenverarbeitung und Elektronik, Karlsruhe, Germany
†
Abstract. A common challenge in many experiments in high-energy astroparticle physics is the need for sparse instrumentation in areas of 100 km2 and above, often in remote and harsh environments. All these arrays have similar requirements for
read-out and communication, power generation and distribution, and synchronization. Within the TAXI project we are developing a transportable, modular four-station test-array that allows us to study different approaches to solve the aforementioned
problems in the laboratory and in the field. Well-defined interfaces will provide easy interchange of the components to be
tested and easy transport and setup will allow in-situ testing at different sites. Every station consists of three well-understood
1 m2 scintillation detectors with nanosecond time resolution, which provide an air shower trigger. An additional sensor, currently a radio antenna for air shower detection in the 100 MHz band, is connected for testing and calibration purposes. We
introduce the TAXI project and report the status and performance of the first TAXI station deployed at the Zeuthen site of
DESY.
Keywords: TAXI, large area instrumentation, data acquisition, air shower detection
PACS: 07.50.-e, 95.45.+
INTRODUCTION
The measurement of charged cosmic rays and astrophysical neutrinos at the highest energies requires extremely large
instrumented areas due to the low flux levels. Ultra-high energy cosmic rays (UHECR) and neutrinos are correlated
due to the fact that the interaction of these protons with the cosmic microwave background radiation will produce
a guaranteed flux of cosmogenic neutrinos [1]. Hence, the detection of those neutrinos will open a new window to
astrophysics, cosmology, and neutrino physics at high center-of-mass energies. UHECR detectors operating today, the
surface detectors of the Pierre Auger Observatory [2] and of the Telescope Array experiment [3], already instrument
areas of the order of thousands of km2 . Next-generation detectors with sizes larger than 10 000 km2 are under study
[4]. Recently, a 100 km2 low-threshold air shower detector at the South Pole has been proposed [5] as an atmospheric
muon veto for the IceCube Neutrino Observatory. Two 100 km2 experiments aiming at the detection of cosmogenic
neutrinos using radio techniques in ice are currently under construction: ARA [6] and ARIANNA [7]; large-area hybrid
detectors combining optical, radio, and acoustic detection channels have been proposed [8].
All these detectors have the need for communication between detection units, low maintenance, decentralized power
generation, clock distribution and trigger generation in common. They are built in harsh environments, from Antarctic
climate to deserts with large daily temperature variations. Further, for site selection campaigns, long-term background
measurements and signal propagation / detection studies have to be performed in-situ at different candidate sites. One
project dedicated to study power generation in the field, mainly in Antarctica, but also at other locations is the ARA
autonomous renewable power station [9]. We aim to generalize the approach of separating the physics detector from
the underlying infrastructure requirements even further in the TAXI project: a Transportable Array for eXtremely large
area Instrumentation studies.
THE TAXI CONCEPT
The goal of the TAXI project is to design and build a modular, autonomous detection station using well-understood
reference air shower detectors and the possibility to connect any new type of sensor with waveform readout up to
180 MHz sampling rate. Possible options for the sensor include radio antennas for air shower or neutrino detection,
EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH (CERN)
CERN-PH-EP/2014-235
2014/10/20
CMS-HIN-13-004
arXiv:1410.4825v1 [nucl-ex] 17 Oct 2014
Study of Z production in PbPb and pp collisions at
√
sNN = 2.76 TeV in the dimuon and dielectron decay
channels
The CMS Collaboration∗
Abstract
The production of Z bosons is studied in the dimuon and dielectron decay channels
√
in PbPb and pp collisions at sNN = 2.76 TeV, using data collected by the CMS experiment at the LHC. The PbPb data sample corresponds to an integrated luminosity
of about 150 µb−1 , while the pp data sample collected in 2013 at the same nucleonnucleon centre-of-mass energy has an integrated luminosity of 5.4 pb−1 . The Z boson yield is measured as a function of rapidity, transverse momentum, and collision
centrality. The ratio of PbPb to pp yields, scaled by the number of inelastic nucleonnucleon collisions, is found to be 1.06 ± 0.05 (stat) ± 0.08 (syst) in the dimuon channel
and 1.02 ± 0.08 (stat) ± 0.15 (syst) in the dielectron channel, for centrality-integrated Z
boson production. This binary collision scaling is seen to hold in the entire kinematic
region studied, as expected for a colourless probe that is unaffected by the hot and
dense QCD medium produced in heavy ion collisions.
Submitted to the Journal of High Energy Physics
c 2014 CERN for the benefit of the CMS Collaboration. CC-BY-3.0 license
∗ See
Appendix A for the list of collaboration members
Nuclear Physics B
Proceedings
Supplement
Nuclear Physics B Proceedings Supplement 00 (2014) 1–6
Uncertainties on the determination of the strong coupling αs
from the energy evolution of jet fragmentation functions at low z
David d’Enterria1 and Redamy P´erez-Ramos2
arXiv:1410.4818v1 [hep-ph] 17 Oct 2014
2
1 CERN, PH Department, CH-1211 Geneva 23, Switzerland
Department of Physics, Univ. of Jyv¨askyl¨a, P.O. Box 35, F-40014 Jyv¨askyl¨a, Finland
Abstract
The QCD coupling αs is determined at NLO*+NMLLA accuracy from the comparison of experimental jet data to
theoretical predictions of the energy-evolution of the parton-to-hadron fragmentation function moments (multiplicity,
peak, width, skewness) at low fractional hadron momentum z. From the existing e+ e− and e± p jet data, we obtain
αs (m2Z ) = 0.1195±0.0021(exp)+0.0015
(scale) at the Z mass. The uncertainties of the extracted αs value are discussed.
−0.0
Keywords: strong coupling, pQCD, jets, parton fragmentation functions, e+ e− annihilation, deep-inelastic scattering
1. Introduction
In the chiral (massless quark) limit, the theory of the
strong interaction –quantum chromodynamics (QCD)–
has a single fundamental parameter: its coupling αs
which decreases logarithmically with increasing energy
scale Q, i.e. αs ∝ ln(Q2 /Λ2QCD ), starting from a value
ΛQCD ≈ 0.2 GeV where the perturbatively-defined coupling diverges. The running coupling αs enters in the
perturbative expansion of theoretical cross section for
any hard process involving quarks and gluons, and the
uncertainty in its value is a key (sometimes dominant)
component of the theoretical error in all perturbative
QCD (pQCD) predictions for any collision process
involving hadrons. Many precision fits of the Standard
Model as well as searches for new physics depend on
αs , whose value needs, thus, to be determined with
good accuracy and precision.
The determination of αs relies on the comparison of
theoretical predictions for various observables, obtained
perturbatively at a given level of accuracy (next-to-nextto-leading order, NNLO, in most cases), with the corresponding experimental measurements. The extracted
αs values at different energy scales are then compared
to each other by translating the result in terms of the
value at the Z mass pole: αs (m2Z ). The current value
of αs (m2Z ) = 0.1185±0.0006, has been obtained from
a combination of measurements at e+ e− , deep-inelastic
scattering (DIS) e,ν-p, and hadron-hadron colliders [1]:
(i) hadronic τ decays (N3 LO), (ii) hadronic W,Z decays (N3 LO), (iii) radiative heavy-quarkonia decays (NLO), and (iv) event shapes and jet rates
(NNLO), in e+ e− collisions;
(v) scaling violations in parton distribution functions
(NNLO), and jet cross sections (NLO), in e,ν-p
DIS;
(vi) jet cross sections and angular correlations (NLO),
and top-quark cross sections (NNLO), in p-p,p-¯p
collisions.
In addition, comparisons of the predictions for different
short-distance observables computed through lattice
and pQCD methods provide extra “data points” for the
determination of the αs (m2Z ) world-average, although
the low systematic uncertainty assigned to such an
approach has been questioned [2]. The current αs
uncertainty is of order ±0.5%, although a more conservative estimate sets it at the ±1% level [2], making
FERMILAB-PUB-14-396-T, LPT-Orsay-14-76, nuhep-th/14-06
Technical Note for 8D Likelihood Effective Higgs
Couplings Extraction Framework in h → 4`
Part I: From Generator Level to Detector Level
Yi Chen a , Emanuele Di Marco a , Joe Lykken b ,
Maria Spiropulu a , Roberto Vega-Morales b,c,d , Si Xie a
arXiv:1410.4817v1 [hep-ph] 17 Oct 2014
a Lauritsen
Laboratory for High Energy Physics,
California Institute of Technology, Pasadena, CA, 92115, USA
b Theoretical Physics Department, Fermilab, P.O. Box 500, Batavia, IL 60510, USA
c Laboratoire de Physique Th´
eorique, CNRS - UMR 8627, Universit´e Paris-Sud, Orsay, France
d Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208, USA
Abstract
In this technical note we present technical details on various aspects of the framework
introduced in [1] aimed at extracting effective Higgs couplings in the h → 4` ‘golden
channel’. Since it is the primary feature of the framework, we focus in particular on
the convolution integral which takes us from ‘truth’ level to ‘detector’ level and the
numerical and analytic techniques used to obtain it. We also briefly discuss other
aspects of the framework.
1
Introduction
It is well known that the h → 4` (4` = 2e2µ, 4e, 4µ) ‘golden channel’ is a powerful means of studying the Higgs couplings to neutral electroweak gauge bosons and various methods have long been
proposed for studying it [2–6] and more recently [7–36]. Though ‘truth’ level (or generator) studies
of the golden channel give a good approximate estimate of the expected sensitivity to the Higgs
ZZ, Zγ, and γγ couplings [36], when analyzing data obtained at the LHC (or future colliders) a
detector level likelihood which accounts for the various detector effects is necessary. Since generally
detector level likelihoods are obtained via the use of Monte Carlo methods, it becomes difficult
to obtain the full multi-dimensional likelihood for the 4` final state. Typically one needs to fill
large multi-dimensional templates that require an impractical amount of computing time. There
are also potential collateral binning and ‘smoothing’ side-effects often associated with these methods. In the case of the golden channel this necessitates the use of kinematic discriminants which
‘collapse’ the fully multi-dimensional likelihood into two or perhaps three detector level observables [31]. This approach is normally taken to facilitate the inclusion of detector effects, but is not
optimal when fitting to a large number of parameters simultaneously [16, 37]. This is unfortunate
in the case of the golden channel where in principle there are twelve observables which can be
used to extract a large number of parameters at once, including their correlations. It would be
satisfying and useful to have a framework which is free of these issues and capable of utilizing all
available information in the four lepton final state at detector level.
This is accomplished in our framework [1] by performing an explicit convolution of the generator (‘truth’) level probability density, formed out of analytic expressions for the signal and
1
Eur. Phys. J. C manuscript No.
(will be inserted by the editor)
On the excess in the inclusive W + W − → l+ l− ν ν¯ cross section
Pier Francesco Monnia,1 , Giulia Zanderighib,1,2
1 Rudolf
arXiv:1410.4745v1 [hep-ph] 17 Oct 2014
2 CERN,
Peierls Centre for Theoretical Physics,University of Oxford,1 Keble Road, Oxford OX1 3RH, UK
Theory Division, CH-1211 Geneva 23, Switzerland
Abstract In this note we analyse the excess in the W + W − inclusive cross section recently measured at the LHC.
We point out that in fact for the ATLAS fiducial cross sections there is no excess in the measurements compared
to the NLO QCD predictions. We also argue that higher order effects to the fiducial cross section are small, and
tend to cancel each other, hence the inclusion of NNLO and NNLL corrections will not modify this agreement
significantly. We find that at 8 TeV a substantial part of the disagreement with the NLO prediction for the total
cross section observed by ATLAS is due to the extrapolation carried out with POWHEG.
1 Introduction
The inclusive W + W − cross section at 7 and 8 TeV has been measured recently by both the ATLAS [1,2] and CMS
collaborations [3, 4]. All measurements show a systematic tension when compared to next-to-leading order (NLO)
QCD calculations. The disagreement was first observed in the 7 TeV data, and then it increased at 8 TeV, where
the tension with the NLO predictions reaches the 2 − 2.5 σ level. The small uncertainties quoted for the NLO
calculations suggest that higher-order QCD corrections can not change this pattern. This triggered a lot of interest
and a number of models were suggested to explain this excess in terms of new light states, see e.g. refs. [5–9].
However, before discussing any hint for New Physics, one needs to fully control the uncertainty associated with
the Standard Model prediction.
One issue that arises, is that refs. [1–4] quote the inclusive cross section, obtained by extrapolating the measured
fiducial cross section through data driven Monte Carlo (MC) acceptances. One reason for quoting the inclusive
cross-section is that it is independent of the experimental setup, hence it is possible to make statements about
whether two measurements by ATLAS and CMS are in agreement, while fiducial cross-sections are different for the
two experiments. Nevertheless, the extrapolation from the fiducial to the inclusive phase space relies on a Monte
Carlo simulation, and thus obviously it depends on the generator used. For instance, a generator that systematically
underestimates the fiducial cross-section would lead to an overestimation of the resulting ”measured” inclusive cross
section. Hence, a comparison to theory should be made first in the fiducial region, for which experimental data
is available, before extrapolating the result to the fully inclusive phase space. A possible way to compare the
measurements of both experiments avoiding a big extrapolation to the total inclusive phase space would be to
extrapolate the ATLAS fiducial measurement from the CMS one, and vice versa. This extrapolation would still
depend on the Monte Carlo generator used, but it would involve two cross sections that are typically of the same
order of magnitude.
In this note we compare the measured fiducial cross sections to the NLO predictions and find that there is no
sizable tension between the two (at the 1-σ level). We then study the effect of the extrapolation from the fiducial
region to the inclusive one. We find that the Monte Carlo acceptance computed with POWHEG overestimates the
reduction due to the fiducial phase space cuts, leading to a larger total cross section when the extrapolation from
the fiducial to the inclusive phase space is carried out. We study the source of the reduction in the Monte Carlo
prediction, and discuss the possible impact of higher-order corrections. At the moment, only ATLAS published the
measured fiducial cross sections at 7 and 8 TeV. Since the larger disagreement is observed in the 8 TeV data, we
focus on the latter measurement for the three leptonic channels, e+ e− , µ+ µ− and e+ µ− + e− µ+ .
2 Comparison to Next to Leading Order prediction
We present here theory predictions for the fiducial cross section as defined by the ATLAS experiment at a centreof-mass energy of 8 TeV [2]. The relative fiducial cuts are summarized in Table 1. Our analysis equally applies to
the 7 TeV case, for which we find similar conclusions.
It is instructive to first compare the fiducial measurements to the next-to-leading order results from MCFM
6.6 [11], including the formally next-to-next-to-leading order (NNLO) contribution due to gg → W + W − [12]. We
a pier.monni@physics.ox.ac.uk
b giulia.zanderighi@cern.ch
Prepared for submission to JHEP
LPSC-14-220, LTH 1015, MS-TP-14-23
arXiv:1410.4692v1 [hep-ph] 17 Oct 2014
NLO+NLL limits on W 0 and Z 0 gauge boson masses
in general extensions of the Standard Model
Tom´
aˇs Jeˇ
zo,a Michael Klasen,b David R. Lamprea,b Florian Lyonnet,c Ingo
Schienbeinc
a
Department of Mathematical Sciences, University of Liverpool, Liverpool L69 3BX, United Kingdom
b
Institut f¨
ur Theoretische Physik, Westf¨
alische Wilhelms-Universit¨
at M¨
unster, Wilhelm-KlemmStraße 9, D-48149 M¨
unster, Germany
c
Laboratoire de Physique Subatomique et de Cosmologie, Universit´e Joseph Fourier/CNRS-IN2P3/
INPG, 53 Avenue des Martyrs, F-38026 Grenoble, France
E-mail: jezo@lpsc.in2p3.fr, michael.klasen@uni-muenster.de,
david.lamprea@uni-muenster.de, florian.lyonnet@lpsc.in2p3.fr,
schien@lpsc.in2p3.fr
Abstract: QCD resummation predictions for the production of charged (W 0 ) and neutral
(Z 0 ) heavy gauge bosons decaying leptonically are presented. The results of our resummation code at next-to-leading order and next-to-leading logarithmic (NLO+NLL) accuracy
are compared to Monte Carlo predictions obtained with PYTHIA at leading order (LO)
supplemented with parton showers (PS) and FEWZ at NLO and next-to-next-to-leading
order (NNLO) for the pT -differential and total cross sections in the Sequential Standard
Model (SSM) and general SU(2)×SU(2)×U(1) models. The LO+PS Monte Carlo and
NNLO fixed-order predictions are shown to agree approximately with those at NLO+NLL
at small and intermediate pT , respectively, and the importance of resummation for total
cross sections is shown to increase with the gauge boson mass. The theoretical uncertainties are estimated by variations of the renormalisation/factorisation scales and of the
parton densities, the former being significantly reduced by the resummation procedure.
New limits at NLO+NLL on W 0 and Z 0 boson masses are obtained by reinterpreting the
latest ATLAS and CMS results in general extensions of the Standard Model.
Keywords: W 0 /Z 0 bosons, LHC, resummation
Dispersive analysis of the pion transition form factor
M. Hoferichter1,2,3 , B. Kubis4 , S. Leupold5 , F. Niecknig4 , S. P. Schneider4
1 Institut
f¨
ur Kernphysik, Technische Universit¨
at Darmstadt, D–64289 Darmstadt, Germany
Matter Institute EMMI, GSI Helmholtzzentrum f¨
ur Schwerionenforschung GmbH, D–64291 Darmstadt, Germany
3 Albert Einstein Center for Fundamental Physics, Institute for Theoretical Physics, University of Bern, Sidlerstrasse 5,
CH–3012 Bern, Switzerland
4 Helmholtz-Institut f¨
ur Strahlen- und Kernphysik (Theorie) and Bethe Center for Theoretical Physics, Universit¨
at Bonn,
D–53115 Bonn, Germany
5 Institutionen f¨
or fysik och astronomi, Uppsala Universitet, Box 516, S–75120 Uppsala, Sweden
arXiv:1410.4691v1 [hep-ph] 17 Oct 2014
2 ExtreMe
Abstract We analyze the pion transition form factor
using dispersion theory. We calculate the singly-virtual
form factor in the time-like region based on data for the
e+ e− → 3π cross section, generalizing previous studies
on ω, φ → 3π decays and γπ → ππ scattering, and
verify our result by comparing to e+ e− → π 0 γ data.
We perform the analytic continuation to the spacelike region, predicting the poorly-constrained space-like
transition form factor below 1 GeV, and extract the
slope of the form factor at vanishing momentum transfer aπ = (30.7 ± 0.6) × 10−3 . We derive the dispersive
formalism necessary for the extension of these results
to the doubly-virtual case, as required for the pion-pole
contribution to hadronic light-by-light scattering in the
anomalous magnetic moment of the muon.
Keywords Dispersion relations · Meson–meson
interactions · Chiral Symmetries · Electric and
magnetic moments
PACS 11.55.Fv · 13.75.Lb · 11.30.Rd · 13.40.Em
1 Introduction
One of the biggest challenges of contemporary particle physics is the unambiguous identification of signs of
beyond-the-standard-model physics. While high-energy
experiments are mainly devoted to the search for new
particles, high-statistics low-energy experiments can
provide such a high precision that standard-model predictions can be seriously scrutinized. A particularly
promising candidate for such an enterprise is the gyromagnetic ratio of the muon, for a review see [1]. Since
the muon is an elementary spin-1/2 fermion, the decisive quantity is the deviation of its gyro-magnetic ratio
g from its classical value. This difference, caused by
quantum effects, is denoted by (g − 2)µ .
From the theory side the potential to isolate effects
of physics beyond the standard model is limited by the
accuracy of the standard-model prediction. Typically
the limiting factor is our incomplete understanding of
the non-perturbative sector of the standard model, i.e.
the low-energy sector of the strong interaction, which is
governed by hadrons as the relevant degrees of freedom
instead of the elementary quarks and gluons. In fact,
for (g − 2)µ the hadronic contributions by far dominate the uncertainties for the standard-model prediction. The largest hadronic contribution, hadronic vacuum polarization (HVP), enters at order α2 in the finestructure constant α = e2 /(4π) and can be directly
related to one observable quantity, the cross section
of the reaction e+ e− → hadrons, by means of dispersion theory. In that way a reliable error estimate of
HVP emerges from the knowledge of the experimental
uncertainties in the measured cross section. At order
α3 there are next-to-leading-order iterations of HVP as
well as a new topology, hadronic light-by-light scattering (HLbL) [2]. It was recently shown in [3] that even
next-to-next-to-leading-order iterations of HVP are not
negligible at the level of accuracy required for the next
round of (g − 2)µ experiments planned at FNAL [4] and
J-PARC [5], while an estimate of next-to-leading-order
HLbL scattering indicated a larger suppression [6].
With the increasing accuracy of the cross-section
measurement for e+ e− → hadrons that can be expected
in the near future [7], the largest uncertainty for (g−2)µ
will then reside in the HLbL contribution. The key
quantity here is the coupling of two (real or virtual)
photons to any hadronic single- or many-body state.
This quantity is not directly related to a single observable. However, it is conceivable to build up the hadronic
states starting with the ones most dominant at low energies, in particular the light one- and two-body intermediate states. Based on a dispersive description of the
Production of the spin partner of the X(3872) in e+e− collisions
Feng-Kun Guo a,∗, Ulf-G. Meißner a,b,†, Zhi Yang a,‡
arXiv:1410.4674v1 [hep-ph] 17 Oct 2014
a
Helmholtz-Institut f¨ur Strahlen- und Kernphysik and Bethe Center for Theoretical Physics,
Universit¨at Bonn, D-53115 Bonn, Germany
b
Institut f¨ur Kernphysik, Institute for Advanced Simulation, and J¨ulich Center for Hadron Physics,
Forschungszentrum J¨ulich, D-52425 J¨ulich, Germany
October 20, 2014
Abstract
¯ ∗ bound state with
We study the production of the spin partner of the X(3872), which is a D∗ D
PC
++
quantum numbers J
= 2
and named X2 (4012) here, with the associated emission of a
photon in electron–positron collisions. The results show that the ideal energy regions to observe
the X2 (4012) in e+ e− annihilations are around 4.43 GeV and 4.47 GeV, due to the presence of
¯ ∗ D1 (2420) and D
¯ ∗ D2 (2460) thresholds, respectively. We also point out that it will
the S-wave D
be difficult to observe the γX(4012) at the e+ e− center-of-mass energy around 4.26 GeV.
∗
E-mail address: fkguo@hiskp.uni-bonn.de
E-mail address: meissner@hiskp.uni-bonn.de
‡
E-mail address: zhiyang@hiskp.uni-bonn.de
†
1
Proceedings of the Second Annual LHCP
October 20, 2014
arXiv:1410.4714v1 [hep-ex] 17 Oct 2014
ATLAS measurements of multi-boson production
Christopher Hays
On behalf of the ATLAS Collaboration,
Department of Physics
Oxford University, Oxford OX1 3RH, UK
ABSTRACT
√
Measurements of electroweak gauge-boson pair-production in s = 7 and 8 TeV
pp collisions at the LHC probe self-couplings and interference effects to an
accuracy of O(10%) or better. ATLAS measurements of ZZ and W Z production
√ at both center of mass energies, and of W W , Zγ and W γ production at
s = 7 TeV, are presented. Total, fiducial, and differential cross sections are
given, along with limits on anomalous triple-gauge couplings.
PRESENTED AT
The Second Annual Conference
on Large Hadron Collider Physics
Columbia University, New York, U.S.A
June 2-7, 2014
October 2014
IPMU 14-0319
SISSA 15/2014/FISI
Dynamical D-Terms in Supergravity
arXiv:1410.4641v1 [hep-th] 17 Oct 2014
Valerie Domckea , Kai Schmitzb , Tsutomu T. Yanagidab
a
b
SISSA/INFN, 34100 Trieste, Italy
Kavli IPMU (WPI), University of Tokyo, Kashiwa 277-8583, Japan
Abstract
Most phenomenological models of supersymmetry breaking rely on nonzero F-terms rather
than nonzero D-terms. An important reason why D-terms are often neglected is that it
turns out to be very challenging to realize D-terms at energies parametrically smaller than
the Planck scale in supergravity. As we demonstrate in this paper, all conventional difficulties
may, however, be overcome if the generation of the D-term is based on strong dynamics. To
illustrate our idea, we focus on a certain class of vector-like SUSY breaking models that enjoy
a minimal particle content and which may be easily embedded into more complete scenarios.
We are then able to show that, upon gauging a global flavor symmetry, an appropriate choice
of Yukawa couplings readily allows to dynamically generate a D-term at an almost arbitrary
energy scale. This includes in particular the natural and consistent realization of D-terms
around, above and below the scale of grand unification in supergravity, without the need for
fine-tuning of any model parameters. Our construction might therefore bear the potential to
open up a new direction for model building in supersymmetry and early universe cosmology.
Vacuum energy sequestering and cosmic dynamics
P.P. Avelino∗
arXiv:1410.4555v1 [gr-qc] 16 Oct 2014
Instituto de Astrof´ısica e Ciˆencias do Espa¸co, Universidade do Porto,
CAUP, Rua das Estrelas, PT4150-762 Porto, Portugal
Centro de Astrof´ısica da Universidade do Porto,
Rua das Estrelas, PT4150-762 Porto, Portugal and
Departamento de F´ısica e Astronomia, Faculdade de Ciˆencias,
Universidade do Porto, Rua do Campo Alegre 687, PT4169-007 Porto, Portugal
(Dated: October 20, 2014)
We explicitly compute the dynamics of closed homogeneous and isotropic universes permeated
by a single perfect fluid with a constant equation of state parameter w in the context of a recent
reformulation of general relativity, proposed in [1], which prevents the vacuum energy from acting
as a gravitational source. This is done using an iterative algorithm, taking as an initial guess the
background cosmological evolution obtained using standard general relativity in the absence of a
cosmological constant. We show that, in general, the impact of the vacuum energy sequestering
mechanism on the dynamics of the universe is significant, except for the w = 1/3 case where the
results are identical to those obtained in the context of general relativity with a null cosmological
constant. We also show that there are well behaved models in general relativity that do not have
a well behaved counterpart in the vacuum energy sequestering paradigm studied in this paper,
highlighting the specific case of a quintessence scalar field with a linear potential.
I.
INTRODUCTION
Solving the cosmological constant problem constitutes
one of the most ambitious challenges of fundamental
physics [2]. The latest constraints [3–7] suggest that
a cosmological constant may be responsible for the observed acceleration of the universe, assuming that gravity
is described by general relativity on cosmological scales.
However, this interpretation of the data faces several
problems: i) why is the vacuum energy density about
120 orders of magnitude smaller than the Planck density? ii) why do we seem to live at a very special epoch
where the fractional contribution of the cosmological constant to the energy density of the universe appears to be
rapidly evolving from 0 in the relatively recent past towards 1 in the not too distant future? The answer to
these questions may lie on dynamical dark energy models [8–11], finite lifetime cosmologies in which the matter
and dark energy densities can be of the same order for
most of the universe lifetime [12–17], and/or anthropic
considerations [17–20].
Another related problem has to do with the fact, unlike the other fundamental interactions, general relativity
is not invariant under the shifting of the Lagrangian by
a constant, implying that the vacuum energy density is
a source for the gravitational field in general relativity.
This has been a matter of debate for many years, with
some authors arguing that a satisfactory solution to the
cosmological constant problem requires a modification
of general relativity (see, for example, [21]). In [1] (see
also [22, 23]) a new mechanism was proposed which prevents the vacuum energy from acting as a gravitational
∗ Electronic
address: pedro.avelino@astro.up.pt
source, thus providing a possible explanation for the huge
discrepancy between the estimation of the vacuum energy density from quantum zero-point fluctuations and
the value inferred from cosmological observations. In the
context of this reformulation of general relativity the universe should be finite in space and time, with the present
epoch of accelerated expansion being a transient stage
before the big crunch.
In the present paper we shall investigate how the cosmological dynamics is affected by the vacuum energy sequestering mechanism. This paper is organized as follows. In Sec. II, some of the key features of the theory
proposed in [1] are outlined. In Sec. III, we use an iterative algorithm to determine the impact of the vacuum energy sequestering mechanism on the dynamics of closed
homogeneous and isotropic universes filled with a perfect fluid with a constant equation of state parameter.
The results are then compared with those obtained in
the context of general relativity with a null cosmological
constant. In this section we also explore the implications
of the vacuum energy mechanism in the context of more
general models, with special emphasis to the case of a
quintessence scalar field with a linear potential. We then
conclude in Sec. IV.
Throughout this paper we use units such that 8πG =
c = 1, where G is the gravitational constant and c is
the value of the speed of light in vacuum. We adopt the
metric signature (−, +, +, +).
II.
THE MODEL
Here we shall consider the action defined in [1] which
yields the following equations of motion for the gravitational field
Gµν = T µν − Λg µν ,
(1)
arXiv:1410.4553v1 [hep-lat] 16 Oct 2014
Hyperon and charmed baryon masses and nucleon
excited states from lattice QCD
Constantia Alexandrou
Department of Physics, University of Cyprus, P.O. Box 20537, 1678 Nicosia, Cyprus
Computation-based Science and Technology Research Center, Cyprus Institute, 20 Kavafi Str.,
Nicosia 2121, Cyprus
NIC, DESY, Platanenallee 6, D-15738 Zeuthen, Germany
E-mail: alexand@ucy.ac.cy
Abstract. We discuss the status of current dynamical lattice QCD simulations in connection
to the emerging results on the strange and charmed baryon spectrum, excited states of the
nucleon and the investigation of the structure of scalar mesons.
1. Introduction
Simulations of lattice QCD are nowadays being performed with dynamical quarks with masses
close to their physical ones. Such simulations with physical pions remove the need for a chiral
extrapolation, thereby eliminating a significant source of a systematic uncertainty that has
proved difficult to quantify in the past. Various fermion discretization schemes are being
employed by various collaborations. MILC has recently presented results on the pseudoscalar
decay constants using Highly Improved Staggered Quark (HISQ) ensembles with the strange
and charm quarks fixed to their physical values and for a range of masses for the two light
quarks (Nf = 2 + 1 + 1) including physical values of the light sea-quark masses [1]. The BMW
collaboration has produced results on the pion sector using Nf = 2 + 1 O(a)-improved Clover
simulations employing HEX smeared links with light quark masses over a range of masses even
below the physical pion mass for four lattice spacings [2]. A number of other collaborations are
using improved Wilson fermions to simulate with physical or near physical values of the two
dynamical light quark masses, in some cases including a dynamical strange quark with mass
fixed to its physical value. Clover gauge configurations have been produced by the QCDSF and
PACS-CS collaborations and pion mass mπ ∼ 150 MeV for Nf = 2 [3] and Nf = 2 + 1 with
re-weighing to reach the physical pion value [4]. The European Twisted Mass Collaboration
(ETMC) has also generated Nf = 2 gauge configurations using twisted mass fermions including
the clover term [5]. Using these ’physical ensembles’ one has now the possibility to study hadron
properties directly.
2. Hadron spectrum
The first quantity that we would like to reproduce from lattice QCD are the masses of the
low-lying hadrons. These are extracted from Euclidean correlation functions
G(~q, ts ) =
X
~
xs
e−i~xs ·~q hJ(~xs , ts )J † (0)i =
X
n=0,··· ,∞
t →∞
An e−En (~q)ts s−→ A0 e−E0 (~q)ts
(1)
Influence of a time-dependent axion field on the London penetration depth of the
Type-I superconductor
Hideto Manjo,∗ Koichiro Kobayashi,† and Kiyoshi Shiraishi‡
arXiv:1407.2024v3 [cond-mat.supr-con] 16 Oct 2014
Yamaguchi University,Yamaguchi-shi,Yamaguchi 753-8512,Japan
(Dated: October 17, 2014)
The effects of the axion field have been widely studied in the theoretical physics, particularly
in the particle physics. The aim of this paper is to estimate a London penetration depth of the
Type-I superconductor using Maxwell’s equations including the time-dependent axion field. The
axion field influences the London penetration depth. There is a slight possibility of detecting this
effect, since the effect becomes more significant on the superconductor with a low carrier density
ns . The differences due to axion models and the axion mass are discussed.
I.
INTRODUCTION
Many authors have proposed the various theory of the
massive photon. In the present paper, the topologically
massive model due to the axion field is studied. An axion electrodynamics is the extension of Maxwell’s electromagnetic theory that includes the dynamical ChernSimon (CS) term, and this additional term is also called
axion term. The presence of the axion field means the
photon becomes topologically massive in the axion electrodynamics.
The axion term is also called Chern-Simons term from
its origin. Chiral Magnetic Effect (CME) [1–3] is a well
known topologically induced electromagnetic effect in the
presence of time-dependent CS term. The literature [4–
7] reported the effect of CS term. In this connection, it is
probable that the CS term has effects on the properties
of the matter. A number of more detailed studies [8–12]
has addressed the role of the CS term or axion term in
the superconductor.
Recently, it has been reported that the axion mass estimates from resonant Josephson junctions, assuming the
time-dependent axion field [13, 14]. These studies reported that the observed Shapiro step anomalies of all
four experiment consistently point towards an axion mass
of (110 ± 2) µeV. As the author of literature [13] point
out, this result of axion mass also need to be examined
from the another viewpoints or experiments.
Among the various possibilities of the effect of the axion field, we focus on the London penetration depth. The
superconductor has perfect diamagnetism that is called
the Meissner effect. The Meissner effect causes the phenomenon that the magnetic field does not penetrate toward deep inside of the superconductor, and the depth
is called the London penetration depth. The present paper presents the simply classical results of the London
penetration depth of the Type-I superconductor using
the electromagnetism including the time-dependent axion field.
∗
†
‡
s004wa@yamaguchi-u.ac.jp
m004wa@yamaguchi-u.ac.jp
shiraish@yamaguchi-u.ac.jp
II.
AXION ELECTRODYNAMICS
The Lagrangian of axion electrodynamics (MaxwellChern-Simons equations [1, 3, 4]) is written as the sum
of Lagrangian for the classical electromagnetism and axion’s two photon interaction:
LA = LEM + LAγγ
1
gγ e2
= − Fµν F µν + θ
Fµν F˜ µν − j µ Aµ ,
4
16π 2
(1)
where gγ is a model-dependent coupling constant, the
value is gγ = −0.97 for KSVZ axions [15, 16] or gγ = 0.36
for DFSZ axions [17, 18]. θ(x) = φA (x)/fA is the misalignement angle of axion field φA (x), fA is the axion
decay constant. −e is the charge of an electron. The
speed of light and the Coulomb’s constant are defined
1
= 1. The gauge and Lorentz
by c = 1 and k = 4πε
0
invariance cannot rule out a second term including θ(x).
In other words, it is possible to allow slight θ(x) dependency. Moreover, the behavior of this dynamical θ(x) is
worth considering.
It is a straightforward calculation to deduce the equations of motion from the Lagrangian (1):
gγ e2
(∇θ) · B,
(2)
4π 2
gγ e2
[(∂t θ)B − (∇θ) × E] . (3)
∇ × B − ∂t E = j −
4π 2
∇·E= ρ−
The other two expressions in Maxwell’s equation do not
change (∇·B = 0, ∇×E = − ∂B
∂t ). In (2) and (3), granted
that θ depends on only the t coordinate, it can eliminate
the differential term with respect to the space coordinate:
∇θ. Thus, the expression (2) and (3) can be written as
∇ · E = ρ,
(4)
gγ e θ˙
B,
∇ × B − ∂t E = j −
4π 2
2
(5)
where θ˙ ≡ ∂t θ. The second term of the right hand
side in (5) implies the current, and this current is called
jCME (Chiral Magnetic Current) [3]. The purpose of the
present paper is to estimate the effect of this term.
KCL-PH-TH/2014-40, LCTS/2014-40, CERN-PH-TH/2014-195
Exploring CP Violation in the MSSM
arXiv:1410.4824v1 [hep-ph] 17 Oct 2014
A. Arbeya,b J. Ellisc,b , R. M. Godboled and F. Mahmoudia,b,∗
a
Universit´e de Lyon, Universit´e Lyon 1, F-69622 Villeurbanne Cedex, France;
Centre de Recherche Astrophysique de Lyon, Saint-Genis-Laval Cedex, F-69561, France;
CNRS, UMR 5574; Ecole Normale Sup´erieure de Lyon, France
b
c
d
Theory Division, CERN, CH-1211 Geneva 23, Switzerland
Theoretical Particle Physics and Cosmology Group, Department of Physics,
King’s College London, London WC2R 2LS, United Kingdom
Centre for High Energy Physics, Indian Institute of Science, Bangalore,560012, India
ABSTRACT
We explore the prospects for observing CP violation in the minimal supersymmetric extension
of the Standard Model (MSSM) with six CP-violating parameters, three gaugino mass phases
and three phases in trilinear soft supersymmetry-breaking parameters, using the CPsuperH code
combined with a geometric approach to maximize CP-violating observables subject to the experimental upper bounds on electric dipole moments. We also implement CP-conserving constraints
from Higgs physics, flavour physics and the upper limits on the cosmological dark matter density
and spin-independent scattering. We study possible values of observables within the constrained
MSSM (CMSSM), the non-universal Higgs model (NUHM), the CPX scenario and a variant of the
phenomenological MSSM (pMSSM). We find values of the CP-violating asymmetry ACP in b → sγ
decay that may be as large as 3%, so future measurements of ACP may provide independent information about CP violation in the MSSM. We find that CP-violating MSSM contributions to
the Bs meson mass mixing term ∆MBs are in general below the present upper limit, which is
dominated by theoretical uncertainties. If these could be reduced, ∆MBs could also provide an
interesting and complementary constraint on the six CP-violating MSSM phases, enabling them
all to be determined experimentally, in principle. We also find that CP violation in the h2,3 τ + τ −
and h2,3 t¯t couplings can be quite large, and so may offer interesting prospects for future pp, e+ e− ,
µ+ µ− and γγ colliders.
∗
Also Institut Universitaire de France, 103 boulevard Saint-Michel, 75005 Paris, France
1
Of Contact Interactions and Colliders
Sacha Davidson∗
IPNL, Universit´e de Lyon, Universit´e Lyon 1, CNRS/IN2P3,
4 rue E. Fermi 69622 Villeurbanne Cedex, France
S´ebastien Descotes-Genon†
Laboratoire de Physique Th´eorique, CNRS/Univ. Paris-Sud (UMR 8627), 91405 Orsay Cedex, France
Patrice Verdier‡
arXiv:1410.4798v1 [hep-ph] 17 Oct 2014
IPNL, Universit´e de Lyon, Universit´e Lyon 1, CNRS/IN2P3,
4 rue E. Fermi 69622 Villeurbanne cedex, France
The hierarchy of scales which would allow dimension-six contact interactions to parametrise New
Physics may not be verified at colliders. Instead, we explore the feasability and usefulness of
parametrising the high-energy tail of distributions at the LHC using form factors. We focus on the
process pp → ℓℓ¯ in the presence of t (or s)-channel New Physics, guess a form factor from the partonic
cross-section, and attempt to use data to constrain its coefficients, and the coefficients to constrain
models. We find that our choice of form factor decribes t-channel exchange better than a contact
interaction, and the coefficients in a particular model can be obtained from the partonic crosssection. We estimate bounds on the coefficients by fitting the form factors to available data. For
the parametrisation corresponding to the contact interaction approximation, our expected bounds
on the scale Λ are within ∼ 15% of the latest limits from the LHC experiments.
PACS numbers:
I.
INTRODUCTION
Suppose that the LHC does not discover new particles
in direct production. It can nonetheless be sensitive to
new particles just beyond its kinematic reach, from their
effects on the high energy tails of distributions. These
effects are usually parametrised by contact interactions,
which are local, non-renormalisable operators. For instance, the process pp → ℓ+ ℓ− can be sensitive to the
four fermion operator
±
4π X
(qγ α PL q)(ℓγ α PL ℓ)
Λ2
(1)
q=u,d
where ℓ = e, µ. With 20 fb−1 of data at 8 TeV in the
centre-of-mass frame, LHC experiments have set bounds
on some coefficients 4π/Λ2 of order Λ >
∼ 10 − 17 TeV
[1–4]. Various recent papers [5] have explored what can
be learned from contact interaction studies, if the LHC
finds no new particles.
Two difficulties arise in attempting to apply currently
available contact interaction (CI) bounds to specific New
Physics (NP) Models:
1) Experimental limits exist only for a selection of
CIs, among the large collection labelled by the chirality, flavour and gauge charge of participating fermions,
as well as the Lorentz structure of the interaction. Since
∗ Electronic
address: s.davidson@ipnl.in2p3.fr
address: sebastien.descotes-genon@th.u-psud.fr
‡ Electronic address: verdier@ipnl.in2p3.fr
† Electronic
the magnitude and sign of the interference with the Standard Model (SM) depends on these labels, it is improbable that an available limit will be applicable to the interactions induced by a particular model.
2) In the sensitivity range of colliders, it is unlikely that
the CI approximation (that p2 ≪ m2 for the heavy mediating particle) is satisfied in any but the most strongly
coupled of models.
A non-local, or “form factor” parametrisation of the
distribution tails might address both points: with a judicious choice of functional form, it may include non-local
interactions mediated by propagating particles, and its
coefficients may be simply calculated in many models.
In this paper, we focus on the process q q¯ → ℓ+ ℓ− at the
LHC, and parametrise the pp → ℓ+ ℓ− cross-section as:
sˆ
dσDY
sˆ2
dσ
1+a
, (2)
=
+b
dˆ
s
dˆ
s
1 + cˆ
s
(1 + cˆ
s)2
where a, b, and c are coefficients to be determined, respectively of mass dimension -2, -4, -2, σDY is the DrellYann (DY) cross-section for Z/γ exchange[17], and sˆ is
the invariant mass-squared of the final state leptons.
Section II supports the functional form of eq. (2)
by studying the partonic cross-section for t-channel exchange of a leptoquark with mass just beyond the reach
of the LHC. Then section III argues that for a generic
model, a, b and c can be estimated from the partonic
cross-section with simple approximations to the parton
distribution functions (pdfs). Finally, section IV attempts a least-squares fit of eq. (2) to available data.
Constraints on leptoquarks [6–8] and contact interactions involving two quarks and two leptons have been
widely studied [9], both from precision and collider data.
Prepared for submission to JHEP
arXiv:1410.4791v1 [hep-ph] 17 Oct 2014
Higgs boson mass and electroweak observables in
the MRSSM
Philip Dießner,a,1 Jan Kalinowski,b Wojciech Kotlarskib and Dominik Stöckingera
a
Institut für Kern- und Teilchenphysik, TU Dresden
01069 Dresden, Germany
b
Faculty of Physics, University of Warsaw,
Pasteura 5, 02093 Warsaw, Poland
E-mail: philip.diessner@mailbox.tu-dresden.de,
jan.kalinowski@fuw.edu.pl, wojciech.kotlarski@fuw.edu.pl,
dominik.stoeckinger@tu-dresden.de
Abstract: R-symmetry is a fundamental symmetry which can solve the SUSY flavor
problem and relax the search limits on SUSY masses. Here we provide a complete next-toleading order computation and discussion of the lightest Higgs boson mass, the W boson
mass and muon decay in the minimal R-symmetric SUSY model (MRSSM). This model
contains non-MSSM particles including a Higgs triplet, Dirac gauginos and higgsinos, and
leads to significant new tree-level and one-loop contributions to these observables. We show
that the model can accommodate the measured values of the observables for interesting
regions of parameter space with stop masses of order 1 TeV in spite of the absence of stop
mixing. We characterize these regions and provide typical benchmark points, which are
also checked against further experimental constraints. A detailed exposition of the model,
its mass matrices and its Feynman rules relevant for computations in this paper is also
provided.
1
Corresponding author.
Nuclear Physics B
Proceedings
Supplement
Nuclear Physics B Proceedings Supplement 00 (2014) 1–7
Effective Theories for QCD-like at TeV Scale
Jie Lu1
IFIC, Universitat de Valencia - CSIC, Apt. Correus 22085, E-46071 Valencia, Spain
arXiv:1410.4782v1 [hep-ph] 17 Oct 2014
Johan Bijnens
Department of Astronomy and Theoretical Physics, Lund University, S`olvegatan 14A, SE 223-62 Lund, Sweden
Abstract
We study the Effective Field Theory of three QCD-like theories, which can be classified by having quarks in
a complex, real or pseudo-real representations of the gauge group. The Lagrangians are written in a very similar
way so that the calculations can be done using techniques from Chiral Perturbation Theory (ChPT). We calculated
the vacuum-expectation-value, the mass and the decay constant of pseudo-Goldstone Bosons up to next-to-next-to
leading order (NNLO) [1]. The various channels of general n flavour meson-meson scattering of the three theories
are systematically studied and calculated up to NNLO [2]. We also calculated the vector, axial-vector, scalar, pseudoscalar two-point functions and pseudo-scalar decay constant up NNLO order [3]. The analytic expressions of the
S parameter for the three different QCD-like theories are obtained at TeV scale. Our results are useful for chiral
extrapolation in lattice calculation on theory of strong dynamical and finite baryon density.
Keywords:
Spontaneous Symmetry Breaking, Lattice Gauge Field Theories, chiral extrapolation, Chiral Lagrangian,
Technicolor, Composite Models
1. Introduction
Strong dynamical electroweak symmetry breaking
(EWSB) is one important candidate theory for beyond
Standard Model (SM). Although the SM-like Higgs Boson is discovered at LHC [4, 5], it is still possible that it
is composite, which arises from the pseudo-Goldstone
Boson modes of new strong interaction at TeV scale,
e.g., the Technicolor theory [6, 7] and other composite
Higgs theories [8].
However, it is very difficult to use perturbative
method in the strong interaction region. Lattice simulation is probably the most promising way for this problem. For computing the quantities in Technicolor theory, one has to push the calculation to the chiral limit,
1 Speaker
i.e., the massless quark limit, this is very time consuming and expensive [9]. Therefore one can extrapolate the
numerical data to the chiral limit using the analytic results from ChPT , which is called Chiral extrapolation.
In this proceeding, we introduce the series of works
on Effective Field Theory of three QCD-like theories,
which are distinguished by having the (techni-)quarks
live in a complex, real or pseudo-real representation of
the gauge group. For n flavours of identical quarks,
this corresponds to the symmetry breaking pattern of
S U(n)L × S U(n)R → S U(n)V , S U(2n) → S O(2n) and
S U(2n) → S p(2n) respectively. These theories can
be used to characterize some Technicolor models with
vector-like gauge bosons.
QCD-like theories are also important in the theory
of finite baryon density, where the normal QCD with
chemical potential term suffers the sign problem in Lat-
Nuclear Physics B
Proceedings
Supplement
Nuclear Physics B Proceedings Supplement 00 (2014) 1–6
B0s,d → `+ `− Decays in Two-Higgs Doublet Models
Xin-Qiang Li
arXiv:1410.4775v1 [hep-ph] 17 Oct 2014
Institute of Particle Physics and Key Laboratory of Quark and Lepton Physics (MOE),
Central China Normal University, Wuhan, Hubei 430079, P. R. China
State Key Laboratory of Theoretical Physics, Institute of Theoretical Physics,
Chinese Academy of Sciences, Beijing 100190, P. R. China
Jie Lu1 , Antonio Pich
IFIC, Universitat de Val`encia – CSIC, Apt. Correus 22085, E-46071 Val`encia, Spain
Abstract
We study the rare leptonic decays B0s,d → `+ `− within the general framework of the aligned two-Higgs doublet
model [1]. A complete one-loop calculation of the relevant short-distance Wilson coefficients is presented, with a
detailed technical summary of the results. The phenomenological constraints imposed by present data on the model
parameters are also investigated.
Keywords: Rare decays, two-Higgs doublet model, Wilson coefficients, Z2 symmetry
1. Introduction
The discovery [2, 3] of a Higgs-like boson at the
LHC has placed the last missing piece of the Standard
Model (SM), which is one of the greatest achievements
of modern particle physics. However, it is widely believed that the SM cannot be the fundamental theory
up to the Plank scale, and many theories beyond the
SM (BSM) claim that new physics (NP) should appear
around the TeV scale.
One of the simplest extensions of the SM is the addition of an extra Higgs doublet [4]. Two scalar doublets are present in several BSM theories, for instance in
supersymmetry. Two-Higgs doublet models (2HDMs)
with generic Yukawa couplings give rise to dangerous
tree-level flavour-changing neutral currents (FCNCs)
[5]. This can be avoided imposing discrete Z2 symmetries [6] or, more generally, assuming the alignment in
flavour space of the two Yukawa matrices for each type
of right-handed fermions [7].
1 Speaker
The leptonic decays B0s,d → `+ `− play a very special
role in testing the SM and probing BSM physics. They
are very sensitive to the mechanism of quark flavour
mixing, and their branching ratios are extremely small
due to the loop suppression and the helicity suppression
factor m` /mb . Since the final state involves only leptons,
the SM theoretical predictions are very clean [8]:
B(B0s → µ+ µ− ) = (3.65 ± 0.23) × 10−9 ,
B(B0d
+ −
→ µ µ ) = (1.06 ± 0.09) × 10
−10
(1)
,
(2)
which include next-to-leading order (NLO) electroweak corrections [9] and next-to-next-to-leading order (NNLO) QCD corrections [10].
The weighted world averages of the CMS [11] and
LHCb [12] measurements [13]
B(B0s → µ+ µ− )exp. = (2.9 ± 0.7) × 10−9 ,
−10
B(B0d → µ+ µ− )exp. = 3.6 +1.6
,
−1.4 × 10
(3)
(4)
are very close to the SM predictions and put stringent
constraints on BSM physics.
Vertex functions of Coulomb gauge Yang–Mills theory
Markus Q. Huber
Institute of Physics, University of Graz, Universit¨
atsplatz 5, 8010 Graz, Austria
Davide R. Campagnari and Hugo Reinhardt
Institut f¨
ur Theoretische Physik, Eberhard-Karls-Universit¨
at T¨
ubingen,
Auf der Morgenstelle 14, 72076 T¨
ubingen, Germany
(Dated: October 20, 2014)
The canonical recursive Dyson–Schwinger equations for the three-gluon and ghost-gluon vertices
are solved numerically. The employed truncation includes several previously neglected diagrams and
includes back-coupling effects. We find an infrared finite ghost-gluon vertex and an infrared diverging
three-gluon vertex. We also compare our results with those obtained in previous calculations, where
bare vertices were used in the loop diagrams.
arXiv:1410.4766v1 [hep-ph] 17 Oct 2014
PACS numbers: 11.10.Ef, 12.38.Aw, 12.38.Lg
Keywords: Hamiltonian approach, ghost-gluon vertex, three-gluon vertex, Coulomb gauge
I.
INTRODUCTION
In recent years many efforts have been undertaken to develop non-perturbative approaches to continuum Quantum
Chromodynamics (QCD). Among these are variational approaches to Yang–Mills theory in Coulomb gauge which use
Gaussian trial ans¨
atze for the Yang–Mills vacuum wave functional [1–3]. The approach of Ref. [3] has given a decent
description of the infrared sector of the theory yielding, among other things, an infrared divergent gluon energy [4],
a perimeter law for the ’t Hooft loop [5] (both are manifestations of confinement), a color dielectric function of the
Yang–Mills vacuum in accord with the dual superconductor picture of the QCD vacuum [6], and a critical temperature
of the deconfinement phase transition in the right ballpark (of about 275 MeV) [7, 8]. Furthermore, the obtained static
gluon propagator is in satisfactory agreement with the lattice data [9], both in the infrared and in the ultraviolet, but
misses some strength in the mid-momentum regime. Preliminary studies of Ref. [10] show that the missing strength
can be attributed to the absence of non-Gaussian terms in the trial Yang–Mills vacuum wave functional ignored in
previous considerations.
In Ref. [10] a general variational approach to quantum field theories was developed, which is capable of using
non-Gaussian trial wave functionals. The crucial point in this approach was to realize that once the vacuum wave
functional is written as the exponential of some action functional given by polynomials of the fields whose coefficients
are treated as variational kernels, one can exploit Dyson–Schwinger equation techniques to express the various vacuum
expectation values of the fields (viz. propagators and vertices) and, in particular, the vacuum expectation value of
the Hamiltonian in terms of the variational kernels. In this way the variational approach can be carried out for
non-Gaussian vacuum wave functionals. In Ref. [10] the approach was worked out for pure Yang–Mills theory using
an ansatz for the vacuum wave functional which contains up to fourth-order polynomials in the gauge field, see
Eqs. (6) and (8) below. In particular, the corresponding Dyson–Schwinger equations for the propagators and leading
vertices were derived. In the present paper we solve the resulting Dyson–Schwinger equations for the ghost-gluon and
three-gluon vertices.
The organization of the paper is as follows: In Sec. 2 we briefly review the essential ingredients of the approach
of Ref. [10]. In Sec. 3 we present the Dyson-Schwinger equations for the ghost-gluon and three-gluon vertices. The
numerical solutions of these equations are presented in Sec. 4. Our conclusions are given in Sec. 5. The Appendix
contains some explicit expressions for the integral kernels.
II.
HAMILTONIAN APPROACH TO YANG–MILLS THEORY
The Hamiltonian approach to Yang–Mills theory rests upon the canonically quantized theory in the temporal (Weyl)
gauge, Aa0 = 0. As a consequence of this gauge, Gauss’s law does not show up in the Heisenberg equations of motion
but has to be imposed as a constraint on the wave functional, which in the absence of matter fields guarantees its
gauge invariance. Furthermore, this gauge does not fix the gauge completely but still leaves invariance with respect
to time-independent gauge transformations. Fixing this residual gauge invariance by imposing the Coulomb gauge
∂i Aai = 0 one can explicitly resolve Gauss’s law for the longitudinal part of the momentum operator. The longitudinal
part of the kinetic energy results then in an extra term in the Hamiltonian, the so-called Coulomb Hamiltonian,
Typeset by REVTEX
UT–14–41
Vetoed jet clustering: The mass-jump algorithm
arXiv:1410.4637v1 [hep-ph] 17 Oct 2014
Martin Stoll
Department of Physics, University of Tokyo, Bunkyo-ku, Tokyo 113–0033, Japan
Abstract
A new class of jet clustering algorithms is introduced. A criterion inspired by successful
mass-drop taggers is applied which prevents the recombination of two hard prongs if they
experience a substantial jump in jet mass. This veto effectively results in jets with variable
radius in dense environments. Differences to existing methods are investigated and it is shown
for boosted top quarks that the new algorithm has beneficial properties which can lead to
improved tagging purity.
Constraining the 6.05 MeV 0+ and 6.13 MeV 3− cascade
transitions in the
12
C(α,γ)16 O reaction using the Asymptotic
Normalization Coefficients
M.L. Avila,1, ∗ G.V. Rogachev,2, † E. Koshchiy,2 L.T. Baby,1 J. Belarge,1 K.W. Kemper,1
A.N. Kuchera,1, ‡ A. M. Mukhamedzhanov,2 D. Santiago-Gonzalez,1, § and E. Uberseder2
arXiv:1410.4592v1 [nucl-ex] 16 Oct 2014
1
Department of Physics, Florida State University, Tallahassee, FL 32306, USA
2
Department of Physics&Astronomy and Cyclotron Institute,
Texas A&M University, College Station, TX 77843, USA
(Dated: October 20, 2014)
Abstract
Background: The 12 C(α, γ)16 O reaction plays a fundamental role in astrophysics because its cross
section near 300 keV in c.m. determines the 12 C/16 O ratio at the end of the helium burning stage of
stellar evolution. The astrophysically desired accuracy of better than 10% has not been achieved.
Cascade γ transitions through the excited states of
16 O
are contributing to the uncertainty.
Purpose: To measure the Asymptotic Normalization Coefficients (ANCs) for the 0+ (6.05 MeV)
and 3− (6.13 MeV) excited states in
16 O
and provide constraints on the cross section for the
corresponding cascade transitions.
Method: The ANCs were measured using the α-transfer reaction
12 C(6 Li,d)16 O
performed at
sub-Coulomb energies for both the entrance and exit channels.
Results: The ANCs for the 0+ (6.05 MeV), 3− (6.13 MeV), 2+ (6.92 MeV) and 1− (7.12 MeV)
states in
16 O
12 C(α, γ)16 O
have been measured. The contribution of the 0+ and 3− cascade transitions to the
reaction S-factor was found to be 1.9±0.3 keV b and 0.5±0.09 keV b respectively.
Conclusions: Significant uncertainties related to the 6.05 MeV 0+ and 6.13 MeV 3− cascade
transitions have been eliminated. The combined contribution of the 0+ and 3− cascade transitions
to the
12 C(α, γ)16 O
reaction cross section at 300 keV does not exceed 2%.
1