1. No category

MeV photons and Dark Matter searches
Yann Mambrini
Laboratoire de Physiaue Théorique, Université Paris Saclay.
http://www.ymambrini.com/My_World/Physics.html
ERC Higgs@LHC
Talk at the second ASTROGAM workshop
LPNHE, Paris, 27th of March 2015
time since the signal appeared
(years)
keV
indirect detection
γ
MeV
I
N
T
E
G
R
A
L
15
10
indirect detection
(other)
TeV
GeV
direct detection
PeV
DAMA
PAMELA
FERMI GC
5
COGENT
CDMS
1
X
M
M
F
E
R
M
I
AMS
Icecube
Energy
keV
MeV
GeV
TeV
PeV
time since the signal appeared
(years)
keV
I
N
T
E
G
R
A
L
15
10
indirect detection
γ
indirect detection
(other)
TeV
MeV
GeV
ASTROGAM
DAMA
direct detection
PeV
5
1
X
M
M
N
oc
an
di
da
tes
(y
et!
)
PAMELA
FERMI GC
COGENT
CDMS
F
E
R
M
I
AMS
Icecube
Energy
keV
MeV
GeV
TeV
PeV
Direct detection summary
No hope to reach the MeV scale
(F. Ruppin, J. Billard, E. Figueroa-Feliciano, L. Stigari; 1408.3581)
SM SM !
A
S
T
R
O
G
A
M
(Td ) = n(Td ) ⇥ h viTd = H(Td )
Why this 0.1-100 MeV region was absent from theoretical dark matter studies?
The Cowsik-Mc Clelland and Lee Weinberg bounds
⇢⌫ 2
n⌫ m⌫
m⌫
⌦⌫ h = c h =
'
5
3
⇢0
10 GeV cm
92 eV
2
td
ho
Ων h =
2
k
ar
Ων h 2 ∝< σ ann v > −1
91.5 eV
COLD
HOT
ter
at
does not work
m
ter
3 – 7 GeV
mat
30 eV
dark
•Σmv<0.66 eV
(WMAP+LSS+SN)
•LEP:
Nν=2.994±0.012
→ mν≥45 GeV
→ Ωνh2 ≤ 10-3
•DM searches
exclude:
10
GeV ≤ mν≤ 4.7 TeV
(similar constraints
for sneutrinos and
KK-neutrinos)
∑ mν
cold
Neutrino
) m⌫ . 9 eV
mix with sterile component
(both for neutrinos and sneutrinos)
h vi = G2F m2 > 10
9
GeV
2
) m > 2 GeV
Why this 0.1-100 MeV region was absent from theoretical dark matter studies?
The Cowsik-Mc Clelland and Lee Weinberg bounds
⇢⌫ 2
n⌫ m⌫
m⌫
⌦⌫ h = c h =
'
5
3
⇢0
10 GeV cm
92 eV
2
td
ho
Ων h =
2
k
ar
Ων h 2 ∝< σ ann v > −1
91.5 eV
COLD
HOT
ter
at
does not work
m
3 – 7 GeV
ter
ASTROGAM
mat
30 eV
dark
•Σmv<0.66 eV
(WMAP+LSS+SN)
•LEP:
Nν=2.994±0.012
→ mν≥45 GeV
→ Ωνh2 ≤ 10-3
•DM searches
exclude:
10
GeV ≤ mν≤ 4.7 TeV
(similar constraints
for sneutrinos and
KK-neutrinos)
∑ mν
cold
Neutrino
) m⌫ . 9 eV
mix with sterile component
(both for neutrinos and sneutrinos)
h vi = G2F m2 > 10
9
GeV
2
) m > 2 GeV
Why this 0.1-100 MeV region was absent from theoretical dark matter studies?
The Cowsik-Mc Clelland and Lee Weinberg bounds
⇢⌫ 2
n⌫ m⌫
m⌫
⌦⌫ h = c h =
'
5
3
⇢0
10 GeV cm
92 eV
2
td
ho
Ων h =
2
k
ar
91.5 eV
COLD
ter
does not work
Ων h 2 ∝< σ ann v > −1
HOT
at
3 – 7 GeV
ter
ASTROGAM
mat
30 eV
dark
g2
GF / 2
MZ
•LEP:
02=2.994±0.012
N
g
ν
0
! GF / →2 m ≥45 GeV
MZ 0 ν
→ Ωνh2 ≤ 10-3
•DM searches
exclude:
10
GeV ≤ mν≤ 4.7 TeV
(similar constraints
for sneutrinos and
KK-neutrinos)
m
Solution:
not standard model interaction
•Σmv<0.66 eV
(Z’, H’, A, supersymmetry..)
(WMAP+LSS+SN)
∑ mν
cold
Neutrino
) m⌫ . 9 eV
mix with sterile component
(both for neutrinos and sneutrinos)
h vi = G2F m2 > 10
9
GeV
2
) m > 2 GeV
illustrated
in section
V. sight
In theviable
latter results.
case, m
˜ is
expecte
Both
cases give
at first
One
can
to be at easily
most of
theitsame
of microscopic
magnitude than
m
derstand
why
is soorder
in the
appro
since it gets
from operators
the vev of approach
a field =ofv Eq.
+
compared
to its
thevalue
e↵ective
e χ2 /d.o.f. Line position
Flux
∆χ2
after spontaneous
symmetry breaking.
Furthermore th
2
[keV] Lucien
10−6
cts/sec/cm
Indeed,
as recently
FIG.
2. Dudas,
Microscopic
diagram
for
annihilation
Emilian
Heurtier
and dark
Yann matter
Mambrini:
«Generating X-ray lines
from annihilating
darkemphasized
matter » (2014)by the authors of [40]
is what
beofmore
generally
expected
if m
˜ is ope
gen
97.8/74 3.53 ± 0.025
4.9+1.6
13.0
the
LHC would
analysis
mono
jet events,
the
e↵ective
XMM
Newton
−1.3
erated
by whatever
mechanism
involving on(
107.8/75 3.53 ± 0.03
< 1.8 (2σ)
...
tors
approach
ceasesdynamical
to be valid
once the ultraviolet
and the light field S. The mass scale ⇤ is related t
72.7/68 3.50+0.044
7.0+2.6
9.1
−0.036
−2.6
croscopic)
theory contains some light mediators, whic
+3.1
the
mass
of heavy particles integrated in the loop. I
62.6/62 3.46 ± 0.04
9.2−3.1
8.0
exactly
our
case. This comes from two powers less i
+2.2
a
perturbative
set up with N charged fermions runnin
191.5/142 3.518+0.019
8.6
(
Perseus
)
25.9
−0.022
−2.3
2
in
the
computation
of observables:
heavier
states beco
4⇡
m+1.4
(
M31
)
(3
dof)
in
the
loop
⇤
⇠
M
,
where
h
is
the
Yukawa
cou
m2s 2 4.6
−1.4 2
2
µ⌫
Nh ↵
FIG.
3.
(m ,m)
˜ heavy
parameter
space allowed
byresult
the flux
mea
now
reasonably
compared
to
the
Eq.(10
L33.1/33
S
m
˜
S
+
F
F
.
(11)
ef f
µ⌫
3.53 ± 0.03
< 0.7 (2σ)
...
pling in
of the to
the
fermions
of mass
. Usin
2
2
⇤
ments
case
of acharged
heavy mediator
(Case
A), forM
di↵erent
v
We
thatGeV
experimental
li
the⇤.will
constraint
M &region
500
fromwhere
collider
an
of
Thesee
redhowever
shaded
indicates
m
˜bounds
issearches
higheron
than
his paper. Second column denotes the sum of exposures of individual observascalar
particle interactions
with
electromagnetic
perturbativity
one finds that
thethe
minimum
natural va
f. (position
and the
flux ofparameter
the line) are added.
energies
for Perseus
arescale
quoted paWe
assume
m
˜ The
to be
a free
mass3450-3600-keV
uesare
forstrongly
⇤ are ⇤ ⇠
50 500 TeV, whereas ⇤ ⇠ 5 TeV ca
tor
restrictive.
ameter. However such coupling can be explicitely generonly
obtained
in a strongly
coupled hidden
sector.
ted by symmetry
breaking in renormalizable models, as
In be
order
to fix ideas,
and anticipating
results
of sec
0.36
ustrated 0.34
in section V. In the latter case, m
˜ is expected
V,
weaindicated
red in
the region
Such
lagrangianingives
forthe
thefigure
annihilation
crosswhere
sectiom
0.32
2
2
m
o be at most
of
the
same
order
of
magnitude
than
m
m
.
This
shows
clearly,
that
m & 300 keV
m
(process
depicted
in
Fig.(2)
)2 imposing
C.
Experimental
Bounds
s
2
0.30
Lef f
S
m
˜ S 2 + Fµ⌫ F µ⌫
nce it gets
=v +
an upper limit for
approximately
0.28its value from the vev of a field
2 ⇤, giving
2
⇤
0.26
ter spontaneous
symmetry breaking. Furthermore this
0.24
2 2
As we just mentioned
above, interactions
of a light sca
4mTeV
˜ .
what would
be more generally expected if m
˜ is gensm
micro⇤ . 1000
0.22
h particle
vi
=
.
(12
1⋅10
2 )2visible
2
2
or
axion-like
(ALP)
with
the
secto
⇡⇤
(4m
m
ated by 8⋅10
whatever dynamical mechanism involving only
s
very
much
constrained
by
collider
data
(LEP)
and as
Furthermore,
the
lower
limit
⇤
&
5 TeV
mentione
6⋅10
and the4⋅10light field S. The mass scale ⇤ is related to
physics.
Indeed
bounds
on pseudoscalar
in
section III
A – still
acceptable
if there isparticles
some stro
he mass 2⋅10
of heavy particles integrated in the loop. In
0⋅10
acting
with
photons
(see
[46]) have
been
studied,
coupled
hidden
sector
generating
the
e↵ective
massuss
perturbative
set
up
with
N
charged
fermions
running
keV
γγ
observation
-2⋅10
ure 2. Morphology 4⇡
of 8 plasma emission lines including the 3.5 keV band
surrounding
theALEPH,
LEP
data
from
OPAL,
and DELPHI,
⇤
–
imposes
an
upper
on line
theL3mediator
mass, m
-4⋅10
B. limit
X-ray
the
loop
⇤
⇠
M
,
where
h
is
the
Yukawa
cou8.0
3.0
3.2
3.4
3.6
3.8
4.0
actic center regionNafter
h ↵ subtracting o↵ the best-fit (ML) contribution from 5 continuum
6
Energy [keV]
shown
that
the coupling
of expect
the pseudoscalar
with p
50
MeV
. One
would thus
from this model
ds.
normalizeof
maps
to the
of each template. The band
ingFor
of illustrative
to the purposes,
chargedwefermions
mass
M variance
. Using
1
4
the
mediator
mass
lies
in
the
region
tons
cannot
exceed
a
value
of
2.6
⇥
10
GeV
fo
m
3.45-3.6
keV isM
shown
in the
center-right
panel.
A on
black
‘+’ indicates
the
location
of
he
constraint
500region
GeV
from
collider
searches
r the
MOS spectrum
ofalso
the &
central
of M31.
Statistical
Y-errorbars
theand
Depending on the hierarchy between the masses of th
E. Bulbul,
M. Markevitch,
A.
Foster,
R. K. Smith, M.
Loewenstein,
S. W.
mediator
of mass
m . 50 MeV, which means, in te
A*
while
the
outer
shell
of
the
supernova
remnant
Sgr
A
East
is
approximately
bounded
bythe
V
is
not
added,
hence
the
group
of
positive
residuals.
Right:
zoom
onto
the
line
erturbativity one finds that
the minimum natural valmediator
and
dark.matter
particle
S, the
conditio
Randall;
300
keV
m
.
50
MeV
.
ellipse shown, from Ref.http://arxiv.org/abs/1402.2301
[26].
of(7)
our
mass scale
leads to two kinds of constraints :
es for ⇤ are ⇤ ⇠ 50 500 TeV, whereas ⇤ ⇠ 5 TeV can
nly be obtained in a strongly coupled hidden sector.
⇤ & 3 TeV
[m . 50 MeV] .
(
The case of XMM Newton signal (2014)
3
M31 ON-center
No line at 3.5 keV
[cts/sec/keV]
Normalized count rate
M31 (02/14)
-2
[cts/sec/keV]
Data - model
-3
No line at 3.5 keV
Line at 3.5 keV
-3
-3
-3
0
-3
-3
obs
5
2
1
5.2 ⇥ 10
photons
cm
sDM
at should
3.55
keVprouch
gives
forofthe
annihilation
cross
s de- a lagrangian
The'
observed
brightness
a decaying
line
! besection
dification
of
Eq.
(2.2)
above
for
the
case
of
annihilation
is trivial.
In our primary
arXiv:1404.1927
Furthermore,
the &
most
restrictive
constraints
e-like
portional
to the
matter )column density SDM = ρDM dℓ –
Caseone
A of
: m
ms (Heavy
Mediator),
process
depicted
indark
Fig.(2)
6
The case of decaying dark matter
Farinaldo Queiroz, Yann Mambrini and Stefano Profumo: «Dark matter and global symmetries » (2015)
MPl
2
( !
)=
2
4⇡MPl
MS3
FIG. 1. Constraints on the lifetime of the
The case of decaying dark matter
Farinaldo Queiroz, Yann Mambrini and Stefano Profumo: «Dark matter and global symmetries » (2015)
ASTROGAM
MPl
2
( !
)=
2
4⇡MPl
MS3
FIG. 1. Constraints on the lifetime of the
Combined ALP limits
Testing Ultra High Energies with ASTROGAM
Giorgio Arcadi and Yann Mambrini: «Axion like particle and UHE neutrinos» (2015)
p
10 MeV = 10
Z 0 /H
10
p
GeV ⇥ 106 GeV = m⌫ ⇥ E⌫cosmic
γ of ~10 MeV
mν = 0.1 eV
ν
f
f˜
γ of ~10 MeV
¯
f
ν
Eν = 106 GeV
⇤
Testing Ultra High Energies with ASTROGAM
Giorgio Arcadi and Yann Mambrini: «Axion like particle and UHE neutrinos» (2015)
p
10 MeV = 10
Z 0 /H
10
p
GeV ⇥ 106 GeV = m⌫ ⇥ E⌫cosmic
γ of ~10 MeV
mν = 0.1 eV
ν
f
f˜
CMB
excluded
γ of ~10 MeV
¯
f
ν
Eν = 106 GeV
10 MeV
⇤
1 GeV
~ Eγ
Mean free path of a UHE neutrino of 1 PeV (106 GeV) hitting a
neutrino from the CνB, resulting in a MeV γ spectrum
Giorgio Arcadi and Yann Mambrini, in preparation
Conclusion
MeV scale largely unexplored from the Dark
Matter point of view
MeV is natural in numerous minimal
extensions of the standard model
Can motivate theoreticians to concentrate
on this new scale for model building
Conclusion
indirect detection
γ
time since the signal appeared
(years)
keV
MeV
I
N
T
E
G
R
A
L
15
10
ASTROGAM
indirect detection
(other)
TeV
GeV
direct detection
PeV
DAMA
5
1
X
M
M
N
oc
an
di
da
tes
(y
et!
)
PAMELA
FERMI GC
COGENT
CDMS F
E
R
M
I
Icecube
Energy
keV
MeV
GeV
TeV
PeV
time since the signal appeared
(years)
keV
MeV
I
N
T
E
G
R
A
15
10
indirect
ASTROGA
indirect
TeV
GeV
direct detection
PeV
DAM
PAMELA
FERMI
1
N
oc
an
di
da
tes
5
COGEN
CDM
X
M
F
E
R
M
Icecube
Energy
keV
MeV
GeV
TeV
PeV
3.53 ± 0.025
4.9+1.6
13.0
−1.3
3.53 ± 0.03
< 1.8 (2σ)
...
3.50+0.044
7.0+2.6
9.1
−0.036
−2.6
3.46 ± 0.04
9.2+3.1
8.0
−3.1
3.518+0.019
8.6+2.2
25.9
−0.022
−2.3 (Perseus)
4.6+1.4
(3 dof)
−1.4 (M31)
33.1/33 3.53 ± 0.03
< 0.7 (2σ)
...
97.8/74
107.8/75
72.7/68
62.6/62
191.5/142
Signal: XMM NEWTON and 3.5 keV line?
XMM Newton
his paper. Second column denotes the sum of exposures of individual observaf. (position and flux of the line) are added. The energies for Perseus are quoted
Clusters of galaxies (02/14)
0.32
[cts/sec/keV]
[cts/sec/keV]
No line at 3.5 keV
0.30
0.28
0.26
0.24
0.22
2⋅10
-2
0
-2
0⋅101⋅10
-1⋅10
3.2
3.4
3.6
3.8
4.0
Energy [keV]
0.90
0.80
-2
1.0⋅10
0.0⋅10
-1.0⋅10
A. Boyarsky, O. Ruchayskiy, D. Iakubovskyi, J. Franse;
3.0
3.5
4.0
4.5
5.0
5.5
http://arxiv.org/abs/1402.4119
spectrum of the central
region of M31. Statistical Y-errorbars on the
the MOS
Energy [keV]
E. Bulbul,
Foster, R.
K. Smith, M.
Loewenstein,
S. W. the line
V is not added,
henceM.
theMarkevitch,
group ofA.
positive
residuals.
Right:
zoom onto
s de-like
ound
ected
stent
1.00
3.0⋅10
-2⋅10-3
8.0
1.10
-2
A. Boyarsky, O. Ruchayskiy, 2.0⋅10
D. Iakubovskyi,
J. Franse;
http://arxiv.org/abs/1402.4119
-2
-2
2⋅10-3
0
-4⋅10-3 0⋅10
3.0
-2
1.20
0.70
MOS1
MOS2
[cts/sec/keV]
4⋅10-3
No line at 3.5 keV
Line at 3.5 keV
Data - model
6⋅10-33⋅10
[cts/sec/keV]
[cts/sec/keV]
8⋅10-3
Data - model
Data - model
1⋅10-2
GC ON, MOS1
GC ON, MOS2
1.30
[cts/sec/keV]
M31 ON-center
0.34 1.00
1.40
GC ON, MOS1
GC ON, MOS2
Normalized count rate
Normalized count rate
Normalized count rate
0.36
Galactic center (08/14)2
6.0
0
-2
3.0
3.2
3.4
3.6
3.8
4.0
Energy [keV]
Randall;
A. Boyarsky,
O. Ruchayskiy,
Iakubovskyi,
J. Franse
FIG. 1: Left: Folded
count rate for MOS1 (lower curve, red) and MOS2 (upper curve,
blue) and
residualsD.(bottom)
when
thearXiv:1408.2503
line at 3.54 keV
http://arxiv.org/abs/1402.2301
is not added. Right: Zoom at the range 3.0–4.0 keV.
obs
' 5.2 ⇥ 10
5
photons cm
The observed brightness of a decaying DM line should
! be proportional to the dark matter column density SDM = ρDM dℓ –
However,
significance
of this
not sufficient
to conintegral
along
the line of sight
of results
the DM is
density
distribution:
firm theLhypothesis,
⇢P e they can be considered
(RP eonly
)3 as a success=
⇥ (DM ! are")clearly
⇥
2checks.
2 # to preform
ful=sanity
needed
4⇡Dpe
mdmMore results
3(D
P e)
cts
Ω
fov
a convincing
program
described
above. × (1)
FDM ≈ checking
2.0 × 10−6
cm2 · sec 500 arcmin2
"
#
"
#
2
s
1
at 3.55 keV
(Perseus, 78 Mpc)
find that the spectrum has a ∼ 5.7σ line-like excess at expected energy. The simultaneous fitting of GC, Perseus and
⇣m ⌘
M31 provides a ∼ 6.7σ significant
at the same position,
dm
23signal
(DM ! ) ' 10
cm 2 s 1
with the detected fluxes being consistent
keVwith the DM interpretation. The fluxes are also consistent with non-observation
of the signal in the blank-sky and M31 off-center datasets,
arXiv:1408.1699v1 [astro-ph.HE] 7 Aug 2014
arXiv:1409.4143v1
[astro-ph.HE] 15 Sep 201
lines can explain the unidentified emission line found by Bulbul et al. (2014) and also by Boyarsky
et al. (2014a,b). We show that their analysis relies upon incorrect atomic data and inconsistent
spectroscopic modeling. We address these points and summarize in the appendix the correct values
matter searches going bananas:
the relevant
atomic
dataline
from AtomDB.
ontribution of Potassium (andfor
Chlorine)
to the
3.5 keV
Alternative explanation for the 3.5 keV line
eltema1⋆ and Stefano Profumo1†
Jeltema,
Profumo [1408.1699]
INTRODUCTION
Printed 11 August 2014 1.
(MN L T
X style file v2.2)
Mon. Not. R. Astron. Soc. 000, 000–000 (0000)
A
E
nt of Physics and Santa Cruz Institute for Particle Physics University of California, Santa Cruz, CA 95064, USA
014
In a recent preprint “Dark matter searches going baChlorine) to
the 3.5 keV line,” Jeltema & Profumo (2014, hereafter
1⋆
1
Tesla Jeltema
and
Stefano that
Profumothe
†
JP)
claim
unidentified E ⇡ 3.55 3.57 keV emisABSTRACT
weemission
detected
galaxy
cluster
We examine thesion
claimedline
excessthat
X-ray line
near 3.5in
keVthe
with stacked
a new analysis
of
XMM-Newton observations
the Milky Wayet
center
with a re-analysis
of theB14)
data on Mand
31 Boyarsky
spectraof (Bulbul
al.and
2014,
hereafter
and clusters. In no case do we find conclusive evidence for an excess. We show that known
et al. (2014a)
detected
in
Perseus
andsatisfactory
M31
(as well as
plasma lines, including in particular
XVIII
at 3.48
and 3.52
We examineKthe
claimed lines
excess X-ray
line emission
near keV,
3.5 keVprovide
with a newaanalysis
of
XMM-Newton observations of the Milky Way center and with a re-analysis of the data on M 31
fit to the XMM data
from the
Galactic
center. We
assess the expected
flux for
the K XVIII
their
more
recent
detection
of the
same
linelines
in the Galacand clusters. In no case do we find conclusive evidence for an excess. We show that known
plasmaflux
lines, including
in particular Kwithin
XVIII lines
at 3.48
and 3.52 keV,range
provide abased
satisfactory
and find that the measured line
falls squarely
the
predicted
on the
tic Center,
(Boyarsky
etWeal.
can
fit to the XMM
data from the Galactic center.
assess2014b))
the expected flux for the
K XVIIIbe
lines accounted for
brightness of other well-measured
lines
in the line
energy
interest.
Werange
then
re-evaluate
and find that
the measured
flux fallsrange
squarelyof
within
the predicted
based
on the
brightness
of other
well-measured
lines
in theincluding
energyLy
range of
interest.
We then
re-evaluateby broadening
the evidence for excess
emission
from
clusters
ofCl
galaxies,
a previously
unaccounted
by an
additional
XVII
line
and
the evidence for excess emission from clusters of galaxies, including a previously unaccounted
for Cl XVII line at 3.51 keV, and
forkeV,systematic
uncertainty
in the
expected
for Cl allowing
XVII line at 3.51
and allowing for
systematic uncertainty
in the
expected fluxflux
from from
the model
uncertainty
for
the
flux
of
the
K XVIII He-like
known plasma
lines
and for additional
uncertainty
due
to potential
variation
inthe
the
abundances
known plasma lines and for additional
uncertainty
due
to
potential
variation
in
abundances
of different elements. We find that no conclusive excess line emission is present within the
triplet.
These
transitions
occur
atre-analyze
⇡
3.51
keV, close to
of different elements.
We find
that no
conclusive
emission
is E
present
systematic
uncertainties
in Perseusexcess
or in otherline
clusters.
Finally, we
XMM within
data for the
M 31 and find no statistically significant line emission near 3.5 keV to a level greater than one
systematic uncertainties in Perseus
or in other clusters. Finally, we re-analyze XMM data for
sigma.
our unidentified
line. In B14, we considered the K line
M 31 and find no statisticallyKey
significant
line emission near 3.5 keV to a level greater than one
words: dark matter – line: identification – Galaxy: centre – X-rays: galaxies – X-rays:
among galaxies:
other
clusters possibilities and concluded that it cannot
sigma.
explain
the
new line.
Here
respond
JP’s concerns,
Key words: dark
matter – line:
identification
– Galaxy:
centrewe
– X-rays:
galaxies to
– X-rays:
galaxies: clustersfocusing on our galaxy cluster analysis.
JP3.48
raise
key Underestimating
points about the
Two lines of potassium Specifically,
KXVIII are at
andthree
3.51 keV.
theiranalysis in B14:
Dark matter searches going bananas:
nanas: the contribution of Potassium (and
the contribution of Potassium (and Chlorine) to the 3.5 keV line
1 Department
of Physics and Santa Cruz Institute for Particle Physics University of California, Santa Cruz, CA 95064, USA
11 August 2014
ABSTRACT
gle θ and of the sterile neutrino mass ms of the form
!
"2 !
"5
The particle nature of the dark matter, comprising most of the
10−4
1 keV
τ ≃ 7.2 × 1029 sec
.
(1)
gravitationally bound structures in the universe, is unknown. A
sin(2θ)
ms
far-ranging experimental and observational program is in place
Such a decay mode produces an almost monochromatic photon sigto search for non-gravitational signals that could point to a given
nal at an energy approximately equal to half the sterile neutrino
class of particle dark matter candidates. While weakly interactmass. Cosmological
production
and constraints from
ing massive particles have attracted much attention,
other particle
gle θ and
of the sterile
neutrino mass
mmechanisms
ODUCTION
s of the form
phase-space density restrict the relevant range for the sterile neucandidates remain theoretically robust and observationally viable.
trino
mass
to,
roughly,
0.5
–
100
keV
(Boyarsky
et al."
2009).
!
"
!
Among such candidates, “sterile” neutrinos offer the appealing pos2
5 As a
−4
le nature of the dark matter, comprising
most of the
result, the
from sterile neutrino1two-body
keV decays falls
sibility of tying the dark matter problem to the issue of generating
29expected line10
τ inter≃ 7.2 ×
10X-raysec
.
(1)
in the
range.
a mass foristheunknown.
Standard Model A
“active” neutrinos, provide an
ally bound structures in the universe,
ms the existence of
Earlier this year,sin(2θ)
Bulbul et al. (2014) claimed
esting warm dark matter candidate, and can be potentially associexperimental and observational ated
program
is
in
place
an unidentified emission line at E = (3.55 − 3.57) ± 0.03 keV
with a mechanism to explain the baryon-antibaryon asymmestacked XMM-Newton
observations
of 73 galaxy clusters
with siga decay
produces
an almost
monochromatic
photon
try in thepoint
universeto
(seea Boyarsky
for a recent
review).modefrom
or non-gravitational signals that could
given et al. 2009,Such
redshift ranging between 0.01 and 0.35. The line is observed with
Sterile neutrinos can mix with active neutrinos, and decay,
nal
at
an
energy
approximately
equal
to
half
the
sterile
neutrino
statistical significance greater than 3σ in three separate subsamarticle dark matter candidates. While
weakly
on timescales
muchinteractlonger than the age of the Universe, to the
ples:production
(i) the individualmechanisms
Perseus cluster; (ii)and
combined
data for the from
two-body final state given by an active neutrino
and
a photon.
mass.
Cosmological
constraints
e particles have attracted much attention,
other particle
Coma, Centaurus and Ophiuchus clusters; (iii) all stacked 73 clusThe details of such process depend on the particular extension to
phase-space density
theChandra
relevant
range
for the
sterile
tersrestrict
in the sample.
observations
of Perseus
indicate
a line neuremain theoretically robust and observationally
viable.
the Standard Model that
accommodates the sterile neutrino(s) (see
feature compatible with the XMM results; The line was not, howe.g. Pal & Wolfenstein 1982), but the lifetime
is setmass
by a modeltrino
to,
roughly,
0.5
–
100
keV
(Boyarsky
et
al.
2009).
As a
h candidates, “sterile” neutrinos offer
the appealing posever, observed in the Virgo cluster with Chandra data. Bulbul et al.
independent combination of the sterile-active neutrino mixing anresult,
the
expected
line
from
sterile
neutrino
two-body
decays
falls
(2014)
explored
possible
contaminations
from
metal
lines,
notably
ying the dark matter problem to the issue of generating
from K and Ar, which would require however typical fluxes factors
in
the
X-ray
range.
the Standard Model “active” neutrinos, provide an interof 10-30 larger than predicted.
⋆ tesla@ucsc.edu
afterettheal.
analysis
of Bulbul
et al. (2014),
3.5 keV
Earlier this year, Shortly
Bulbul
(2014)
claimed
the aexistence
of
m dark matter candidate, and can be
potentially associ† profumo@ucsc.edu
line was reported from XMM-Newton observations of both the
1 INTRODUCTION
amplitude (the density of such elements in a galactic environment) could mimic a
1. A possible Cl XVII Ly line at E = 3.51 keV was
dark matter signal. The authors
showed in
that
within
the reasonable abundance
not included
our
model;
(comparing with other more known concentrations like Argon) the « signal » can
2. The plasma temperatures derived from the ratios
easily be below 1σ and mainly
to atomic
Potassium
of due
fluxes
of S rays
XVI,ofCa
XIX and Ca XX lines in the
cluster spectra are inconsistent, thus a much larger
range of temperatures must be allowed in modeling;
S
where ✏ is the emissivity, T is the requested temperature,
Tpeak is the temperature for which the transition’s emissivity is its maximum, and N is the abundance of the
ion. This approximation is intended for quick identification of possible strong lines, as it disregards the change
in line emissivity with temperature, instead accounting
only for the relative change in ion abundance.1
Using these approximate data, we were able to recreate
the values in JP’s Table 3 exactly from the data in Table 2, to identify exactly which lines JP included in their
flux ratio
calculations,
and to explain
line ratios
Bulbul
answers
that the approximation
made bythe
Profumo
et al. ondisthe
cussed in their §3.1. The error due to the use of this
emissivity ascan
function
of thelarge
temperature
is not valid. away
approximation
be very
for temperatures
from the line peak emissivity temperature, as illustrated
in Fig. 1 for our four relevant lines.
1.2. Line Ratios as Temperature Diagnostics
Incorrect atomic data easily lead to incorrect conclusions about the gas temperature structure based on the
observed line ratios. In particular, JP find that the observed ratios of the S XVI, Ca XIX, Ca XX lines (the
used: in
B14 toanalysis
estimate the K XVIII flux) indithe lines
answer
careful
cate very di↵erent plasma temperatures. (Of course, in
feature compatible with the XMM results; The line was not, howof
the
morphology
of
the
is not compatible
ever, observed in the Virgo cluster with Chandra
data. Bulbul
et al.
a signal
single-component
plasma in ionization equilibrium, all
They conclude
that,
accounting
formetal
these
points, no ad(2014) explored
possible
contaminations from
lines, notably
line ratios
correspond
to the same temperature.)
with
classical
DM profiles
in must
the case
of
from Kis
and required
Ar, which would by
requirethe
however
typicaldata.
fluxes factors
ditional line
B14
We address
of 10-30 larger than predicted.
they
conclude that the plasma has to have
these items below.
annihilating
DM or Therefore,
axion-like
transition
Shortly after the analysis of Bulbul et al. (2014),
a 3.5 keV
a very complex temperature structure, and so B14 were
line was reported from XMM-Newton observations of both the
not justified to restrict the temperature range for our es1.1. Atomic Data
3450-3600-keV
timates of the K XVIII flux. We will address the K line
In a study of this nature, using accurate atomic data
[1411.1758]
an Jeltema,
unidentified
line
at E = (3.55
3.57) ± 0.03temperatures,
keV
3. Carlson,
When
usingProfumo
aemission
wider
range
of −possible
from stacked XMM-Newton observations of 73 galaxy clusters with
and redshift
scaling
fluxes
S with
XVI, Ca XIX,
rangingfrom
between the
0.01 and
0.35. Thefor
line isthe
observed
statistical
significance
greater than
3σ B14
in three for
separate
subsamCa XX
lines
reported
by
the
Perseus clusples: (i) the individual Perseus cluster; (ii) combined data for the
ter, Coma,
the Centaurus
total flux
in the
K (iii)
XVIII
and
Cl XVII lines
and Ophiuchus
clusters;
all stacked
73 clusProfumo’s
in the sample.
Chandra
observations
of Perseus indicate
a lineanswer to
can ters
match
that
of the
unidentified
line.
mechanism to explain the baryon-antibaryon asymmec 0000 RAS
⃝
niverse (see Boyarsky et al. 2009, for a recent review).
e neutrinos can mix with active neutrinos, and decay,
les much longer than the age of the Universe, to the
final state given by an active neutrino and a photon.
of such process depend on the particular extension to
d Model that accommodates the sterile neutrino(s) (see
Wolfenstein 1982), but the lifetime is set by a modelnt combination of the sterile-active neutrino mixing an-
c.edu
@ucsc.edu
(Bulbul, Markevitch,
Foster,
Smith, Loewenstein,
Randallbe
[1409.4143]
AtomDB
v2.0.2. In
theory,
these should
the fluxes
from their Table 2, multiplied by the ratio of predicted
K XVIII emissivities to that of the line in question.
We can, however, recreate their Table 3 if we use the
approximate values available in the “strong lines” option
at http://www.atomdb.org/WebGUIDE/webguide.php.
As described on that page, this option uses an approximation
✏(T ) = ✏(Tpeak )N (T )/N (Tpeak )
(1)