A. De Simone: The Quest for Dark Matter: Update and News

The Quest for Dark Matter:
update and news
Andrea De Simone
Balkan Workshop - 26 Apr 2013

A. De Simone 1
Outline
Status of Dark Matter Searches
Interpretation of New AMS-02 Data
Correlations and Predictions

A. De Simone 2
Dark Matter is Real
Evidences for DM
CMB+LSS
rotation curves of galaxies
gravitational lensing
[millennium]
[wmap]

A. De Simone 3
Candidates
WIMP
axion
gravitino
axino
sterile neutrino
techni-baryon,
Q-balls
...
(an incomplete list)
neutralino
minimal DM
heavy neutrino
inert Higgs doublet
LKP
LTP
...
non-WIMP

A. De Simone 4
Search Strategies
COLLIDER
INDIRECT DETECTION
AMS-02, Pamela, Fermi, HESS
ATIC, Fermi
GAPS, AMS-02
IceCube, Antares, Km3Net
γ
e+
, ¯p
¯d
ν
LHC
DIRECT DETECTION
Xenon, CDMS, CRESST,
CoGeNT, Edelweiss...
p p → DM + X
DM DM → e+
e−
, . . .
DM Nucleus → DM Nucleus

A. De Simone 5
Direct Detection
positive hints (signals)
DAMA/Libra
(NaI)
2-4 keV
Time (day)
Residuals(cpd/kg/keV)
DAMA/NaI (0.29 ton!yr)
(target mass = 87.3 kg)
DAMA/LIBRA (0.53 ton!yr)
2-5 keV
Time (day)
Residuals(cpd/kg/keV)
2-6 keV
(cpd/kg/keV)
[DAMA Coll - 0804.2741]
8σ observation of
annual modulation
CoGeNT
(Ge)
2.7σ annual
modulation
Direct Detection: hints
Annual modulation seen ( ):8σ
DAMA Coll., 0804.2741, 2008
DAMA/Libra CoGeNT
‘irreducible excess of bulk
events below 3 KeVee’
CoGeNT coll., 1106.0650
G
FIG. 4: Rate vs. time in several energy regions (the last
spans 8 days). A dotted line denotes the best-ﬁt modulat
A solid line indicates a prediction for a 7 GeV/c2
WIM
[CoGeNT Coll - 1106.0650]

A. De Simone 6
Direct Detection
[CDMS - 1304.4279]
CDMS
(Si)
3 events,
<3σ
10 100 1000
WIMP mass [GeV]
10
-9
10
-8
10
-7
10
-6
10
-5
10
-4
10
-3
WIMP-nucleoncrosssection[pb]
CRESST 1σ
CRESST 2σ
CRESST 2009
EDELWEISS-II
CDMS-II
XENON100
DAMA chan.
DAMA
CoGeNT
M2
M1
[CRESST - 1109.0702]
CRESST
(CaWO4)
gloher et al.: Results from 730 kg days of the CRESST-II Dark Matter Search 9
d information of the individual
r to clarify the contributions of
ources to the total background.
t the result is compatible with
e limiting cases given here.
of the neutron background con-
ecoil energy spectrum. Within
rgy range, the energy spectra
s of neutron events are found
rding to the calibration data
ctrum can be parametrized by
n/dE ∝ exp (−E/Edec). We
Edec from a fit to the spec-
Be neutron calibration run. In
n 12 keV to 40 keV we obtain
pectra induced by neutrons from
rces (in agreement with Monte
how the Pb/Cu shielding sur-
ill moderate an incoming neu-
rigin. The primary spectrum of
t by inelastic scatterings in the
pports our use of the results of
o estimate the effects of a gen-
The only exception to this ar-
on-producing contamination in
tors. In this case, we would ex-
aching to much higher energies
ven number of coincidences. In
of our above calibration results
e neutron background estimate.
und
l background from 210
Po decay,
et of a different detector mod-
Fig. 8. (Color online) The data of detector module Ch51,
shown in the light yield vs. recoil energy plane. Again, the
shaded areas indicate the bands, where alpha (yellow), oxygen
(violet), and tungsten (gray) recoil events are expected. Ad-
ditionally highlighted are the acceptance region (orange), the
region where lead recoils with energies between 40 and 90 keV
are expected (green), and the events observed in these regions.
The highlighted lead recoil region (green) serves as a reference
region for estimating the 206
Pb recoil background.
module nPb
ref
Ch05 17
Ch20 6
Ch29 14
Ch33 6
Ch43 12
Ch45 15
Ch47 7
Ch51 12
total 89
ion seen ( ):8σ
DAMA Coll., 0804.2741, 2008
CRESST-II CaWO4
CRESST-II Coll., 1109.0702
67 events seen on Oxygen,
twice the exp’d background
tungsten
oxygen
alpha
signal
region
too energetic, cannot be recoil
PTED
MANUSCRIPT
ACCEPTED MANUSCRIPT
composite target like CaWO4, the total scattering rate is dominated by recoils of tungsten. However,
in a real experiment with a finite energy threshold other nuclei can be relevant, as tungsten recoils
may not be energetic enough to be detected. Fig. 1 shows the contribution of the three types of nuclei
in CaWO4 to a recoil spectrum measured in the energy interval from 10 to 40 keV. WIMPs with a
mass below 10 GeV would not be able to produce visible tungsten recoils above threshold, most of the
observable recoils would be on oxygen and some on Ca. For a small range of WIMP masses above 10
GeV, Ca is most important while for WIMP masses above 20 GeV tungsten recoils dominate.
Figure 1: Relative contribution of the three types of recoil nuclei in CaWO4 as a function of the WIMP
mass. The calculation assumes that recoils above 10 keV can be measured.
2 Detection Principle and Setup
The low-temperature calorimeters consist of a target crystal with a superconducting phase transition
thermometer on its surface. The thermometer is made of a tungsten film evaporated onto the target
crystal. Its temperature is stabilized within the transition from the superconducting to the normal
conducting state, which occurs at temperatures of about 10 mK. A typical width of the transition is
about 1 mK. A small temperature rise, e.g. from a WIMP–nucleus scattering event, of typically some
µK, leads to an increase of resistance of some µΩ, which is measured with a SQUID (Superconducting
Quantum Interference Device). A weak thermal coupling of the thermometer to the heat bath restores
the equilibrium temperature again after an interaction. In CRESST-II, 300 g scintillating CaWO4
crystals are used as target. In these crystals a particle interaction creates mostly phonons which are
67 events, ~4σ
PS: CDMS-Si 2013
CDMS
3 events seen on Si,
with 0.41 exp’d background
(a bit less than 3!)
Si
4
timing that are transformed so that the WIMP accep-
tance regions of all detectors coincide.
After unblinding, extensive checks of the three candi-
date events revealed no data quality or analysis issues
that would invalidate them as WIMP candidates. The
signal-to-noise on the ionization channel for the three
events (ordered in increasing recoil energy) was measured
to be 6.7σ, 4.9σ, and 5.1σ, while the charge threshold
had been set at 4.5σ from the noise. A study on pos-
sible leakage into the signal band due to 206
Pb recoils
from 210
Po decays found the expected leakage to be neg-
ligible with an upper limit of < 0.08 events at the 90%
confidence level. The energy distribution of the 206
Pb
background was constructed using events in which a co-
incident α was detected in a detector adjacent to one
of the 8 Si detectors used in this analysis. Further-
more, as in the Ge analysis, we developed a Bayesian
estimate of the rate of misidentified surface events based
upon the performance of the phonon timing cut mea-
sured using events near the WIMP-search signal region
[22]. Classical confidence intervals provided similar esti-
mates [23]. Multiple-scatter events below the electron-
recoil ionization-yield region from both 133
Ba calibration
FIG. 4. Experimental upper limits (90% confidence level) for
the WIMP-nucleon spin-independent cross section as a func-
CoGeNT
Xenon100
positive hints (signals)

A. De Simone 7
Direct Detection
null experiments: Xenon, CDMS (Ge), Edelweiss
puzzling situation: maybe it is telling us something about the
WIMP-nuclei interactions or the structure of the DM halo
4
sformed so that the WIMP accep-
etectors coincide.
extensive checks of the three candi-
no data quality or analysis issues
e them as WIMP candidates. The
e ionization channel for the three
reasing recoil energy) was measured
d 5.1σ, while the charge threshold
from the noise. A study on pos-
e signal band due to 206
Pb recoils
und the expected leakage to be neg-
limit of < 0.08 events at the 90%
e energy distribution of the 206
Pb
tructed using events in which a co-
cted in a detector adjacent to one
s used in this analysis. Further-
analysis, we developed a Bayesian
f misidentified surface events based
ce of the phonon timing cut mea-
ear the WIMP-search signal region
ence intervals provided similar esti-
-scatter events below the electron-
region from both 133
Ba calibration
ta were used as inputs to this model.
icts an updated surface-event leak-
+0.20
−0.08(stat.)+0.28
−0.24(syst.) misidentified
eight Si detectors.
ains the available parameter space
er models. We compute upper lim-
cleon scattering cross section using
FIG. 4. Experimental upper limits (90% confidence level) for
the WIMP-nucleon spin-independent cross section as a func-
tion of WIMP mass. We show the limit obtained from the ex-
posure analyzed in this work alone (black dots), and combined
with the CDMS II Si data set reported in [22] (blue solid line).
Also shown are limits from the CDMS II Ge standard [11] and
low-threshold [27] analysis (dark and light dashed red), EDEL-
WEISS low-threshold [28] (orange diamonds), XENON10 S2-
only [29] (light dash-dotted green), and XENON100 [30] (dark
CoGeNT
Xenon100
[CDMS - 1304.4279]
CRESST
DAMA
CDMS (Ge)
Edelweiss

A. De Simone 8
Collider Searches
Difficult search, unless correlating MET with other handles
(displaced vertex, ISR jets, ISR photons...)
• 2#$3'4#5"$'.$),0%1)-':+*"7';+77+-:'<$#-7*"$7"'"-"$:='84
• @&)<)-7'8)$'A"<7'($);'#':60)-9'%#-'B"'$#,+#<",'($);'C0#$3
8)$';)-)A"<9'.607'4>?4
q
¯q
Figure 1: Dark matter production in association
3.1. Comparing Various M
Dark matter pair production through a diagram
for dark matter searches at hadron colliders [3, 4]. T
of jets plus missing energy (j + /ET ) events over the S
mainly of (Z → νν) + j and (W → invν) + j final stat
lost, as indicated by the superscript “inv”. Experimen
performed by CDF [22], CMS [23] and ATLAS [24, 25]
Our analysis will, for the most part, be based on th
jets in 1 fb−1 of data, although we will also compare t
36 pb−1 of integrated luminosity. The ATLAS search
successively harder pT cuts, the major selection crite
analysis are given below.3
LowPT Selection requires /ET 120 GeV, one jet with
are vetoed if they contain a second jet with pT (
HighPT Selection requires /ET 220 GeV, one jet wit
are vetoed if there is a second jet with |η(j2)|
∆φ(j2, /ET ) 0.5. Any further jets with |η(j2)|
veryHighPT Selection requires /ET 300 GeV, one j
events are vetoed if there is a second jet with |η
4
q
¯q
χ
¯χ
Figure 1: Dark matter production in association with a single jet in a hadron collider.
3.1. Comparing Various Mono-Jet Analyses
Dark matter pair production through a diagram like figure 1 is one of the leading channels
for dark matter searches at hadron colliders [3, 4]. The signal would manifest itself as an excess
of jets plus missing energy (j + /ET ) events over the Standard Model background, which consists
mainly of (Z → νν) + j and (W → invν) + j final states. In the latter case the charged lepton is
lost, as indicated by the superscript “inv”. Experimental studies of j + /ET final states have been
performed by CDF [22], CMS [23] and ATLAS [24, 25], mostly in the context of Extra Dimensions.
Our analysis will, for the most part, be based on the ATLAS search [25] which looked for mono-
jets in 1 fb−1 of data, although we will also compare to the earlier CMS analysis [23], which used
36 pb−1 of integrated luminosity. The ATLAS search contains three separate analyses based on
successively harder pT cuts, the major selection criteria from each analysis that we apply in our
LowPT Selection requires /ET 120 GeV, one jet with pT (j1) 120 GeV, |η(j1)| 2, and events
are vetoed if they contain a second jet with pT (j2) 30 GeV and |η(j2)| 4.5.
HighPT Selection requires /ET 220 GeV, one jet with pT (j1) 250 GeV, |η(j1)| 2, and events
are vetoed if there is a second jet with |η(j2)| 4.5 and with either pT (j2) 60 GeV or
∆φ(j2, /ET ) 0.5. Any further jets with |η(j2)| 4.5 must have pT (j3) 30 GeV.
veryHighPT Selection requires /ET 300 GeV, one jet with pT (j1) 350 GeV, |η(j1)| 2, and
events are vetoed if there is a second jet with |η(j2)| 4.5 and with either pT (j2) 60 GeV
Direct Detection (t-channel) Collider Searches (s
Monophoton + MET Monojet + ME
• 2#$3'4#5$'.$),0%1)-':+*7';+77+-:'$#-7*$7'-$:='84?9
• @))-7'8)$'A7'($);'#':60)-9'%#-'B'$#,+#,'($);'C0#$37D':+*+-:
8)$';)-)A9'.607'4?4
q
¯q
χ
¯χ
Figure 1: Dark matter production in association with a single
3.1. Comparing Various Mono-Jet An
Dark matter pair production through a diagram like figure 1
for dark matter searches at hadron colliders [3, 4]. The signal wo
of jets plus missing energy (j + /ET ) events over the Standard Mo
mainly of (Z → νν) + j and (W → invν) + j final states. In the la
lost, as indicated by the superscript “inv”. Experimental studies
performed by CDF [22], CMS [23] and ATLAS [24, 25], mostly in t
Our analysis will, for the most part, be based on the ATLAS se
jets in 1 fb−1 of data, although we will also compare to the earlie
36 pb−1 of integrated luminosity. The ATLAS search contains th
successively harder pT cuts, the major selection criteria from eac
LowPT Selection requires /ET 120 GeV, one jet with pT (j1) 1
are vetoed if they contain a second jet with pT (j2) 30 Ge
HighPT Selection requires /ET 220 GeV, one jet with pT (j1) 2
are vetoed if there is a second jet with |η(j2)| 4.5 and w
∆φ(j2, /ET ) 0.5. Any further jets with |η(j2)| 4.5 must
veryHighPT Selection requires /ET 300 GeV, one jet with pT (j
events are vetoed if there is a second jet with |η(j2)| 4.5 a
4
q
¯q
χ
¯χ
Figure 1: Dark matter production in association with a single jet in a hadron collider.
3.1. Comparing Various Mono-Jet Analyses
Dark matter pair production through a diagram like figure 1 is one of the leading channels
for dark matter searches at hadron colliders [3, 4]. The signal would manifest itself as an excess
of jets plus missing energy (j + /ET ) events over the Standard Model background, which consists
mainly of (Z → νν) + j and (W → invν) + j final states. In the latter case the charged lepton is
lost, as indicated by the superscript “inv”. Experimental studies of j + /ET final states have been
performed by CDF [22], CMS [23] and ATLAS [24, 25], mostly in the context of Extra Dimensions.
Our analysis will, for the most part, be based on the ATLAS search [25] which looked for mono-
jets in 1 fb−1 of data, although we will also compare to the earlier CMS analysis [23], which used
36 pb−1 of integrated luminosity. The ATLAS search contains three separate analyses based on
successively harder pT cuts, the major selection criteria from each analysis that we apply in our
LowPT Selection requires /ET 120 GeV, one jet with pT (j1) 120 GeV, |η(j1)| 2, and events
are vetoed if they contain a second jet with pT (j2) 30 GeV and |η(j2)| 4.5.
HighPT Selection requires /ET 220 GeV, one jet with pT (j1) 250 GeV, |η(j1)| 2, and events
are vetoed if there is a second jet with |η(j2)| 4.5 and with either pT (j2) 60 GeV or
∆φ(j2, /ET ) 0.5. Any further jets with |η(j2)| 4.5 must have pT (j3) 30 GeV.
veryHighPT Selection requires /ET 300 GeV, one jet with pT (j1) 350 GeV, |η(j1)| 2, and
events are vetoed if there is a second jet with |η(j2)| 4.5 and with either pT (j2) 60 GeV
Direct Detection (t-channel) Collider Searches (s-channe
Monophoton + MET Monojet + MET
14 References
]2
[GeV/c!M
1 10
2
10
3
10
]2
-NucleonCrossSection[cm!
-46
10
-44
10
-42
10
-40
10
-38
10
-36
10
-34
10
-32
10
-30
10
-28
10
-27
10
CMS 2012 Axial Vector
CMS 2011 Axial Vector
CDF 2012
SIMPLE 2012
CDMSII 2011
COUPP 2012
-
W
+
Super-K W
-
W+
IceCube W
CMS Preliminary
= 8 TeVs
-1
L dt = 19.5 fb
Spin Dependent
2
#
q)
5
$
µ
$q)(!
5
$
µ
$!(
]2
[GeV/c!M
1 10
2
10
3
10
]2
-NucleonCrossSection[cm!
-46
10
-44
10
-42
10
-40
10
-38
10
-36
10
-34
10
-32
10
-30
10
-28
10
-27
10
CMS 2012 Vector
CMS 2011 Vector
CDF 2012
XENON100 2012
COUPP 2012
SIMPLE 2012
CoGeNT 2011
CDMSII 2011
CDMSII 2010
CMS Preliminary
= 8 TeVs
Spin Independent
-1
L dt = 19.5 fb
2
#
q)
µ
$q)(!
µ
$!(
Figure 7: Comparison of CMS 90% CL upper limits on the dark matter-nucleon cross section
versus dark matter mass for the vector operator with CDF [54], SIMPLE [55], CDMS [21],
COUPP [56], Super-K [26] and IceCube [25] and for the axial-vector operator with CDF [54],
[CMS PAS EXO-12-048]
in LHC we trust...
constrain DM-quarks interactions
and translate into limits on
scattering cross-section
complementary/
competitive with
direct detection.
no astrophysical
uncertainty.

A. De Simone 9
Indirect Detection
Key observable: ﬂuxes of stable particles ( )
from DM annihilations/decay in galactic halo or center
γ, ν, ¯p, e+
8 kpc
20 kpc

A. De Simone 10
Indirect Detection
DM
DM
−
, ¯q, W−
, Z, γ, . . .
+
, q, W+
, Z, γ, . . .
e±
, γ, ν, ¯ν, p, ¯p, . . .
primary
channels
stable
species
SM
evolution
astrophysical
propagation
fluxes
at detection
e±
, γ, ν, ¯ν, p, ¯p, . . .
DM annihilations in
galactic halo/center

A. De Simone 10
Indirect Detection
DM
DM
−
, ¯q, W−
, Z, γ, . . .
+
, q, W+
, Z, γ, . . .
e±
, γ, ν, ¯ν, p, ¯p, . . .
primary
channels
stable
species
SM
evolution
particle physics
radiation/hadronization/decay
(QCD, QED, EW)
model for DM interactions
(L)
fluxes
at detection
astrophysical
propagation
e±
, γ, ν, ¯ν, p, ¯p, . . .
DM annihilations in
galactic halo/center

A. De Simone 11
Indirect Detection “Anomalies”
“Anomalies” in gamma rays
Fermi 135 GeV line
Fermi ”bubbles”
“Anomaly” in charged cosmic rays (positron fraction e+/(e++e-) )
see Zaharijasʼ talk later
What if a signal of DM is already hidden
in Fermi diffuse data?γ
Figure 4. Upper sub-panels: the measured events with statistical errors are plotted in black. The
horizontal bars show the best-fit models with (red) and without DM (green), the blue dotted line
indicates the corresponding line flux alone. In the lower sub-panel we show residuals after subtracting
the model with line contribution. Note that we rebinned the data to fewer bins after performing the
Figure 1. Left panel: The black lines show the target regions that are used in the pr
case of the SOURCE event class (the ULTRACLEAN regions are very similar). Fro
they are respectively optimized for the cored isothermal, the NFW (with α = 1), the
contracted (with α = 1.15, 1.3) DM profiles. The colors indicate the signal-to-backg
arbitrary but common normalization; in Reg2 to Reg5 they are respectively down
(1.6, 3.0, 4.3, 18.8) for better visibility.
Right panel: From top to bottom, the panels show the 20–300 GeV gamma-ray
spectra as observed in Reg1 to Reg5 with statistical error bars. The SOURCE and
events are shown in black and magenta, respectively. Dotted lines show power-laws w
slopes; dashed lines show the EGBG + residual CRs. The vertical gray line indicates
Ch. Wen
1204.2
3
Fermi 80 E 100 GeV
180 90 0 -90 -18000
-90
-45
0
45
90
00
0.0
0.5
1.0
1.5
2.0
2.5
0.0
0.5
1.0
1.5
2.0
2.5
keVcm-2
s-1
sr-1
Fermi 100 E 120 GeV
180 90 0 -90 -18000
-90
-45
0
45
90
00
0.0
0.5
1.0
1.5
2.0
2.5
0.0
0.5
1.0
1.5
2.0
2.5
keVcm-2
s-1
sr-1
Fermi 120 E 140 GeV
180 90 0 -90 -18000
-90
-45
0
45
90
00
0.0
0.5
1.0
1.5
2.0
2.5
0.0
0.5
1.0
1.5
2.0
2.5
keVcm-2
s-1
sr-1
Fermi 140 E 160 GeV
180 90 0 -90 -18000
-90
-45
0
45
90
00
0.0
0.5
1.0
1.5
2.0
2.5
0.0
0.5
1.0
1.5
2.0
2.5
keVcm-2
s-1
sr-1
Fermi 160 E 180 GeV
180 90 0 -90 -18000
-90
-45
0
45
90
00
0.0
0.5
1.0
1.5
2.0
2.5
0.0
0.5
1.0
1.5
2.0
2.5
keVcm-2
s-1
sr-1
Residual map
180 90 0 -90 -18000
-90
-45
0
45
90
00
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
keVcm-2
s-1
sr-1
Fig. 3.— All-sky CLEAN 3.7 year maps in 5 energy bins, and a residual map (lower right). The residual map is the 120 − 140 GeV map
minus a background estimate, taken to be the average of the other 4 maps where the average is computed in E2dN/dE units. This simple
background estimate is sufficient to remove the Galactic plane and most of the large-scale diffuse structures and even bright point sources.
A cuspy structure toward the Galactic center is revealed as the only significant structure in the residual gamma-ray map. All of the maps
are smoothed with a Gaussian kernel of FWHM = 10◦ without source subtraction.
are available on the Internet, and it is from these files
that we build our maps.
The point spread function (PSF) is about 0.8◦
for 68%
the Fermi Cicerone5
. We also exclude some time in-
tervals, primarily while Fermi passes through the South
Atlantic Anomaly.
Su,Finkbeiner,1206.1616
The excess is only in the GC
(actually, a bit off-set)
Figure 1. Map at 120-140 GeV showing regions with positive and negative excesses around the background.
Three most significant regions from [2] are shown with white circles, the remaining regions from [2] are
shown with green circles.
Region Power law parameters χ2 Prominent Significance
Features σ
REG 1 Γ = 3.4 ± 0.4; N100 = 4.3 ± 0.6 0.98 Line at 115 GeV 3.86
REG 2(overall) Γ = 2.2 ± 0.2; N100 = 7.1 ± 0.6 0.94 –
REG 2(60–110 GeV) Γ = 1.4 ± 0.8; N100 = 8.0 ± 2.0 2.12 Dip at 95 GeV -4.7
REG 2(110–200 GeV) Γ = 2.7 ± 0.5; N100 = 7.8 ± 1.4 0.29 –
REG 3 Γ = 3.6 ± 0.5; N100 = 2.3 ± 0.4 0.79 Line at 80 GeV 2.86
Table 1. Continuum fits for regions REG 1, REG 3, REG 2. We fit the background at overall (60-200 GeV)
or specified energy band using the power law (N(E) = N100(E/100 GeV−Γ
) and show the most prominent
feature above this background together with its formal significance.
Similar excesses found elsewhere
(fluctuation?)
Boyarsky,Malyshev,
Ruchayskyi,1205.4700
4.6σ (3.3σ w
σvχχ→γγ
1.3 · 10−27
c
(large!)
And there might b
111 GeV, 129
Simulation: GALPROP Template Fitting
bubbles
Residual map (ellipse region excluded
from fit)
Bubble template obtained fr
Residual map after including bubble
template in all sky fit
Different GALPROP model used in fit than in simulation
Spectra |b|10deg

A. De Simone 12
Positron Fraction “anomaly”
AMS-02 has recently released data of positron fraction up to
energies of ~350 GeV.
Excess over “known” bkg, conﬁrming previous PAMELA and
Fermi-LAT measurements.
e+/(e++e-)
[AMS-02 Coll - PRL 110,
141102 (2013)]

.
A. De Simone 13
the Dark Matter explanation of the excess is already strongly
constrained by other measurements (e.g. gamma-rays)
so the astrophysical explanations look very likely
.
where can positrons
come from?
.
local astrophysical sources
(e.g. pulsars)
Dark Matter
annihilations/decay

local astrophysical sources
(e.g. pulsars).
A. De Simone 13
the Dark Matter explanation of the excess is already strongly
constrained by other measurements (e.g. gamma-rays)
so the astrophysical explanations look very likely
I want to insist on the DM interpretation and
see how far we can get
.
where can positrons
come from?
.
Dark Matter
annihilations/decay

A. De Simone 14
Electroweak Corrections
e+
e-
DM
DM
[Ciafaloni, Cirelli, Comelli, DS, Riotto, Urbano - 1104.2996]
[Ciafaloni, Comelli, DS, Riotto, Urbano - 1202.0692]
[DS, Monin, Thamm, Urbano - 1301.1486]
[Ciafaloni, Comelli, Riotto, Sala, Strumia, Urbano, 1009.0224]

A. De Simone 14
Electroweak Corrections
p
π0
π+
e+
µ+
Z
γ
γ
e+
e-
DM
DM
νµ
¯νµ
νe
The final state of DM annihilations can
radiate γ,Z,W.
It is a SM effect, affecting the final
fluxes importantly.
EW interactions connect all SM particles
all species will be present in the final state 104
103
102
101 1
104
103
102
101
1
x Ekin MDM
dNdlnx
DM DM Μ
Μ
, MDM 1000 GeV
p
Γ
e

A. De Simone 15
Correlations among DM signals
ﬁt
signal
DM
DM
e+
, γ, ν, ¯p, . . .
EW corrections
e+
, γ, ν, ¯p, . . .
predictions
assume DM
interpretation

A. De Simone 15
ﬁt
signal
DM
DM
e+
, γ, ν, ¯p, . . .
EW corrections
correlated
fluxes
e+
, γ, ν, ¯p, . . .
predictions
.
test with
current/future data
assume DM
interpretation
verify/reject
initial
hypothesis

A. De Simone 15
ﬁt
signal
DM
DM
e+
, γ, ν, ¯p, . . .
EW corrections
correlated
fluxes
e+
, γ, ν, ¯p, . . .
predictions
.
test with
current/future data
assume DM
interpretation
verify/reject
initial
hypothesis
✓ robust
✓ timely

A. De Simone 15
ﬁt
signal
DM
DM
EW corrections
correlated
fluxes
predictions
.
test with
current/future AMS data
assume DM
interpretation
verify/reject
initial
hypothesis
e+
¯p

10
2
10
3
10
2
10
1
E
kin
[ GeV ]
e+
/(e+
+e−
)
A. De Simone 16
Interpretation of AMS-02 data
possible interpretation as DM,
without upsetting the anti-p ﬂux
DM DM → τ+
τ−
10
0
10
1
10
2
10
7
10
6
10
5
10
4
10
3
10
2
10
1
Ekin
[ GeV ]
Φ(¯p)[GeV−1
m−2
s−1
sr−1
]
PAMELA
anti-p data
AMS
e+ data
MDM = 1 TeV
σannv = 2.5 × 10−23
cm3
s−1
positron fraction anti-protons
[DS, Riotto, Xue - 1304.1336]

A. De Simone 17
before claiming any signal, bkg should be under control
signal and background ﬂuxes are closely related, because they
propagate from source to detection within the same environment
cosmic-ray propagation is a very complex phenomenon, affected
by several uncertainties
crucial to use consistently the same propagation setup for both
signal and background (and for all particle species)
The Importance of Being Propagated

A. De Simone 18
annihilation channels?
only leptonic annihilation channels are still allowed
MDM [GeV ]
log10(σv/cm3
s−1
)
Einasto
2000 4000 6000 8000 10000
25
24
23
22
21
MDM [GeV ]
log10(σv/cm3
s−1
)
Einasto
2000 4000 6000 8000 10000
25
24
23
22
21
DM DM → b¯b DM DM → W+
W−
ALL channels produce hadrons (due to EW corrections)
can easily upset anti-p data
Interpretation of AMS-02 data: channels
DM DM → q¯q, +
−
, W+
W−
, ZZ, hh, . . .
Ex.
exclusion by
PAMELA anti-p data
Model-independent analysis of AMS-02 data

1.9 0.7
τ+
τ−µ+
µ−
A. De Simone 19
Interpretation of AMS-02 data: Best Fits
use only data with E15 GeV (not affected by solar modulation)
number of dof: 36-6=30
e+e- gives even higher χ2
10
2
10
3
10
4
0
50
100
150
MDM [GeV ]
χ2
µ+
µ−
τ+
τ−
χ2
min/dof
.
only good ﬁt to AMS-02:
DM of ~ 1 TeV
annihilating into taus

A. De Simone 20
positrons-antiprotons Correlations
MDM [GeV ]
log10(σv/cm3
s−1
)
Burkert
500 1000 1500 2000
25
24
23
22
21
MDM [GeV ]
log10(σv/cm3
s−1
)
Einasto
500 1000 1500 2000
25
24
23
22
21
MDM [GeV ]
log10(σv/cm3
s−1
)
NFW
500 1000 1500 2000
25
24
23
22
211 year
3 years
we simulated projected (mock) data for anti-p, consistent with
understanding of detector features from outside the collaboration
3 years of AMS-02 anti-p data would be enough to rule out
almost competely the DM interpretation of the positron rise
3σ best-ﬁt contours for DM DM → τ+
τ−

A. De Simone 21
Constraints from other Data-sets
taking into account Fermi-LAT diffuse gamma-ray constraints
MDM [GeV ]
log10(σv/cm3
s−1
)
Burkert
500 1000 1500 2000
25
24
23
22
21
best-ﬁt regions for other halo proﬁles are mostly excluded
3σ
5σ
[Fermi-LAT Coll.- 1205.6474]

A. De Simone 22
tension with e++e - Fermi-LAT data, showing no drop up to ~1 TeV
8
Dot Dashed: MΧ 2.5 TeV, ΧΧ ΦΦ 2Μ 2Μ
Dashed: MΧ 3.0 TeV, ΧΧ ΦΦ 2Π 2Π
Solid: MΧ 1.6 TeV, ΧΧ ΦΦ 2e , 2Μ , 2Π at 1:1:2
1 5 10 50 100
0.02
0.05
0.10
0.20
0.50
1.00
E GeV
eee
Dot Dashed: MΧ 2.5 TeV, ΧΧ ΦΦ 2Μ 2Μ
Dashed: MΧ 3.0 TeV, ΧΧ ΦΦ 2Π 2Π
Solid: MΧ 1.6 TeV, ΧΧ ΦΦ 2e , 2Μ , 2Π at 1:1:2
1 10 100 1000
1
5
10
50
100
500
1000
E GeV
eeE3
xdiff.fluxGeV2
m2
ssr1
FIG. 6: The same as in Figs. 1, 2, 4 and 5 but for a diﬀusion zone half-width of L = 8 kpc, and for broken power-law spectrum
of electrons injected from cosmic ray sources (dNe− /dEe− ∝ E−2.65
e below 100 GeV and dNe− /dEe− ∝ E−2.3
e above 100
GeV). The cross sections are the same as given in the caption of Fig. 5. With this cosmic ray background, the dark matter
models shown can simultaneously accommodate the measurements of the cosmic ray positron fraction and the overall leptonic
spectrum.
All Milky Way pulsars
Α 1.55, Ec 600 GeV
0.50
1.00
All Milky Way pulsars
Α 1.55, Ec 600 GeV
500
1000
2
ssr1
[Cholis,Hooper - 1304.1840]
need somewhat exotic annihilation channels ( ),
perhaps with a break in the injection spectrum of primary electrons
DM DM → φφ → 2µ+
2µ−
Constraints from other Data-sets
[Cirelli et al. - 0809.2409v2]
positron fraction e++e -

A. De Simone 23
Conclusions
The current situation on DM is very confusing...
Complementarity: robust conclusions on the nature of DM should
come from correlations of different signatures among different expts.
(crucial role played by EW corrections)
Interpretation of AMS-02 recent results on positron fraction
we are on the verge of ruling out, once for all,
the DM origin of the positron excess
.

A. De Simone 23
Conclusions
The current situation on DM is very confusing...
Complementarity: robust conclusions on the nature of DM should
come from correlations of different signatures among different expts.
(crucial role played by EW corrections)
Interpretation of AMS-02 recent results on positron fraction
huge and diverse efforts to detect signals of DM
discovery in 5-10 years, or forget about the WIMPs...
we are on the verge of ruling out, once for all,
the DM origin of the positron excess
.
Golden Age of Dark Matter searches.

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A. De Simone
Fluxes
Fluxes of cosmic rays received at Earth:
where the number density is the solution of the transport eq.:
energy spectrum
of stable particle i
∂ni
∂t
= Q(r, z, p)

source
+∇ ·

D∇ni

diffusion
− Vcni

convection

+
∂
∂p
p2
Dpp
∂
∂p
1
p2
ni
−
∂
∂p

˙pni −
p
3
(∇ · Vc) ni

−
1
τsp
ni

spallation
−
1
τf
ni

fragmentation
halo profile
dΦi/dE ≡ βini/(4π)
ni(r, z, p)
Q(r, z, E) ∝ [ρDM(r, z)]2
σannv
dNi
dE
.
Particle Physics enters into:
energy spectrum
cross section
.
Astrophysics enters into:
propagation parameters;
DM halo profile. σannv
dNi/dE

A. De Simone
Halo Profiles
103
102
101 1 10 102
103
102
101
1
10
102
103
104
r kpc
ΡDMGeVcm3

Burkert
Einasto
NFW r
Ρ
ρ(r) =



ρs

(1 + r/rs)(1 + (r/rs)2
)
−1
, rs = 12.67 kpc, ρs = 0.712 GeV/cm3
, (Burkert)
ρs exp

− 2
0.17

(r/rs)
0.17
− 1

, rs = 28.44 kpc, ρs = 0.033 GeV/cm3
, (Einasto)
ρs(rs/r) (1 + r/rs)
−2
, rs = 24.42 kpc, ρs = 0.184 GeV/cm3
, (NFW)

A. De Simone
Propagation Methods
Method 1
✘ fluxes of different species are treated as uncorrelated;
✓ deal with astrophys. uncert. in a simple and conservative way.
Method 2
then marginalize over A, p parameters.
✘ not generic;
✓ consistent propagation of all species, for both signal and bkg.
Propagate signal and bkg with our own propagation model,
which provides a good fit to several data-sets
(electron+positron, anti-p, Boron-to-Carbon ratio).
(i = e+
, e−
, ¯p)Φbkg
i (E, Ai, pi) = Ai Epi
[Φbkg
i (E)]reference
Signal: propagate with “MED” propagation model
Bkg: reference one with floating normalizations and slopes

A. De Simone
10
0
10
1
10
2
10
3
10
6
10
4
10
2
E
kin
(GeV)
Φ(¯p)[GeV−1
m−2
s−1
sr−1
]
10
0
10
1
10
2
10
4
10
3
E
kin
(GeV)
¯p/p
Propagation Methods
Fits of our reference propagation model to anti-p PAMELA data
solid/dashed = with/without correcting for solar modulation

A. De Simone
Importance of EW corrections
EW corrections to DM annihilations are important in 3 cases:
1. when the low-energy regions of the spectra, which are largely populated
by the decay products of the emitted gauge bosons, are the ones
contributing the most to the observed ﬂuxes;
2. when some species are absent without EW corrections
(e.g. antiprotons from );
3. when σ(2 →3), with soft gauge boson emission, is comparable or even
dominant with respect to σ(2 →2):
DM Majorana fermion/real scalar and SM singlet;
DM Majorana fermion/real scalar in an SU(2)L-multiplet.
χχ → +
−

A. De Simone: The Quest for Dark Matter: Update and News

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