Can the DAMA annual modulation be explained byDark Matter?
Thomas Schwetz-Mangold
MPIK, Heidelberg
based on M. Fairbairn and T. Schwetz, arXiv:0808.0704
T. Schwetz, MPIK, 24 Nov 2008 – p. 1
Outline
• Introduction• Review on DM direct detection phenomenology• recent DAMA/LIBRA results• DAMA vs XENON/CDMS for
spin-independent elastic DM scattering• Non-standard DM halos• Beyond SI elastic DM scattering• Summary
T. Schwetz, MPIK, 24 Nov 2008 – p. 2
The CDM paradigm
a popular candidate for DM is a
Weakly Interacting Massive Particle
T. Schwetz, MPIK, 24 Nov 2008 – p. 5
The CDM paradigm
a popular candidate for DM is a
Weakly Interacting Massive Particle
in the following I will try to be as model independentas possible:
I just assume that there is an unknown particlearound in our galaxy with some mass mχ andinteraction cross section σ, and consider thephenomenology for direct detection experiments
no constraints from collider searches will beconsidered
T. Schwetz, MPIK, 24 Nov 2008 – p. 5
DM direct detection
Look for recoil of DM-nucleus scattering:
χ + N → χ + N
cnts / kg-detector mass / keV recoil energy ER:
dN
dER
(t) =ρχ
mχ
σ(q)
2µ2χ
∫
v>vmin
d3vf⊕(~v, t)
v︸ ︷︷ ︸
≡η(ER,t)
ρχ DM energy density, default: 0.3 GeV cm−3
q =√
2MER momentum transfer
µχ = mχM/(mχ + M) reduced DM/nucleus mass
η(ER, t) integral over DM velocity distribution in lab frameT. Schwetz, MPIK, 24 Nov 2008 – p. 7
Cross section
in general there is a spin-independent andspin-dependent contribution to the DM-nucleonscattering cross section:
σ(q) = σSI(q) + σSD(q)
T. Schwetz, MPIK, 24 Nov 2008 – p. 8
Cross section
spin-independent:
σSI(q) = σ0 |F (q)|2 , F (q) : nuclear form factor, (norm.: F (0) = 1)
σ0 =2µ2
χ
π[Zfp + (A − Z)fn]2 ≈ σp
µ2χ
µ2p
A2 for fp ≈ fn
spin-dependent:
σSD =32µ2
χG2F
2J + 1
[a2
pSpp(q) + apanSpn(q) + a2nSnn(q)
]
ap, an: couplings to proton and neutron
Spp(q), Spn(q), Snn(q): nuclear structure functions
T. Schwetz, MPIK, 24 Nov 2008 – p. 9
Cross section
spin-independent:
σSI(q) = σ0 |F (q)|2 , F (q) : nuclear form factor, (norm.: F (0) = 1)
σ0 =2µ2
χ
π[Zfp + (A − Z)fn]2 ≈ σp
µ2χ
µ2p
A2 for fp ≈ fn
spin-dependent:
σSD =32µ2
χG2F
2J + 1
[a2
pSpp(q) + apanSpn(q) + a2nSnn(q)
]
ap, an: couplings to proton and neutron
Spp(q), Spn(q), Snn(q): nuclear structure functions
A2-enhancement of SI cross sectionT. Schwetz, MPIK, 24 Nov 2008 – p. 9
Cross section
spin-independent:
σSI(q) = σ0 |F (q)|2 , F (q) : nuclear form factor, (norm.: F (0) = 1)
σ0 =2µ2
χ
π[Zfp + (A − Z)fn]2 ≈ σp
µ2χ
µ2p
A2 for fp ≈ fn
consider first only SI contribution:
⇒ dN
dER
(t) =ρχ
mχ
σp|F (q)|2A2
2µ2p
η(ER, t)
T. Schwetz, MPIK, 24 Nov 2008 – p. 10
Velocity distribution
η(ER, t) =
∫
v>vmin(ER)
d3vf⊕(~v, t)
v
v = |~v| : DM velocity in detector rest framevmin : minimal DM velocity required to produce recoil energy ER
vmin =
√
MER
2µ2χ
=mχ + M
mχ
√
ER
2M
T. Schwetz, MPIK, 24 Nov 2008 – p. 11
Velocity distribution
η(ER, t) =
∫
v>vmin(ER)
d3vf⊕(~v, t)
v
v = |~v| : DM velocity in detector rest framevmin : minimal DM velocity required to produce recoil energy ER
vmin =
√
MER
2µ2χ
=mχ + M
mχ
√
ER
2M
obtain velocity distribution in Earth rest frame f⊕ fromdistribution in galaxy rest frame fgal:
f⊕(~v, t) = fgal(~v + ~v⊙ + ~v⊕(t))T. Schwetz, MPIK, 24 Nov 2008 – p. 11
Velocity distribution
f⊕(~v, t) = fgal(~v + ~v⊙ + ~v⊕(t))
“standard halo model”: Maxwellian velocity distribution
fgal(~v) =
N [exp (−v2/v2) − exp (−v2esc/v
2)] v < vesc
0 v > vesc
with v = 220 km/s and vesc = 650 km/s
T. Schwetz, MPIK, 24 Nov 2008 – p. 12
Velocity distribution
f⊕(~v, t) = fgal(~v + ~v⊙ + ~v⊕(t))
sun velocity: ~v⊙ = (0, 220, 0) + (10, 13, 7) km/searth velocity: ~v⊕(t) with v⊕ ≈ 30 km/s
T. Schwetz, MPIK, 24 Nov 2008 – p. 12
Velocity distribution integral
-600 -400 -200 0 200 400 600 800 1000v
y [km/s]
-600
-400
-200
0
200
400
600
800
1000
v z[k
m/s
]
center of galaxy: x-axis
vmin
for M = 118 GeV(127
I), m = 10 GeV
E R = 10 keV
5 keV3 keV
∫
v>vmin
d3vf⊕(~v, t)
v
vmin =
√
MER
2µ2χ
T. Schwetz, MPIK, 24 Nov 2008 – p. 13
Velocity distribution integral
-600 -400 -200 0 200 400 600 800 1000v
y [km/s]
-600
-400
-200
0
200
400
600
800
1000
v z[k
m/s
]
center of galaxy: x-axis
vmin
for M = 118 GeV(127
I), m = 10 GeV, Erec
= 3 keV
June 2nd
Dec 2nd
∫
v>vmin
d3vf⊕(~v, t)
v
T. Schwetz, MPIK, 24 Nov 2008 – p. 13
Velocity distribution integral
η(ER, t) ∝ 1
vobs(t)
∫ ∞
vmin(ER)
dv
[
e−
“
v−vobs(t)
v
”2
− e−
“
v+vobs(t)
v
”2]
0 200 400 600 800v [km/s]
velo
city
dis
trib
utio
n [a
rb. u
nits
]
0 200 400 600 8001
10
100
DM
mas
s [G
eV]
vmin
June 2nd
Dec. 2nd
M = 21.4 GeV (Na), Erec = 3 keV
M = 67.5 GeV (Ge), Erec = 10 keVM = 118 GeV (I), E
rec = 3 keV
vm
ean
vmin =
s
MER
2µ2χ
vobs(t) = |~v⊙ + ~v⊕(t)|
T. Schwetz, MPIK, 24 Nov 2008 – p. 14
The DAMA experiment
search for a scinitillation signal in NaI crystals
DAMA/NaI ∼ 87.3 kg 7 yr 0.29 t yrDAMA/LIBRA ∼ 232.8 kg 4 yr 0.53 t yrtotal exposure: 0.82 t yr
DAMA/LIBRA consists of 25 detectors,9.70 kg each 10.2 × 10.2 × 25.4 cm2
T. Schwetz, MPIK, 24 Nov 2008 – p. 16
The DAMA experiment
search for a scinitillation signal in NaI crystals
DAMA/NaI ∼ 87.3 kg 7 yr 0.29 t yrDAMA/LIBRA ∼ 232.8 kg 4 yr 0.53 t yrtotal exposure: 0.82 t yr
total single-hit scintillation signal in DAMA/LIBRA:
0
2
4
6
8
10
2 4 6 8 10 Energy (keV)
Rat
e (c
pd/k
g/ke
V)
∼ 1 cnts/d/kg/keV → ∼ 2 × 105 events/keV in DAMA/LIBRAT. Schwetz, MPIK, 24 Nov 2008 – p. 16
The DAMA annual modulation signal
evidence for an annual modulation of the count rate:Bernabei et al., 0804.2741
2-6 keV
Time (day)
Res
idua
ls (
cpd/
kg/k
eV) DAMA/NaI (0.29 ton×yr)
(target mass = 87.3 kg)DAMA/LIBRA (0.53 ton×yr)
(target mass = 232.8 kg)
T. Schwetz, MPIK, 24 Nov 2008 – p. 17
The DAMA annual modulation signal
fitting count rate with S0 + A cos ω(t − t0):
expectation for DM: T = 1 yr, t0 = 152 (2nd June)
T. Schwetz, MPIK, 24 Nov 2008 – p. 18
The DAMA annual modulation signal
fitting count rate with S0 + A cos ω(t − t0):
expectation for DM: T = 1 yr, t0 = 152 (2nd June)
8.2σ evidence for annual modulationT. Schwetz, MPIK, 24 Nov 2008 – p. 18
Energy dependence of the modulation signal
Energy (keV)
S m (
cpd/
kg/k
eV)
-0.05
-0.025
0
0.025
0.05
0 2 4 6 8 10 12 14 16 18 20
Sm (cpd/kg/keV)
Zm
(cp
d/kg
/keV
)
2-6 keV
6-14 keV
2σ contours
-0.03
-0.02
-0.01
0
0.01
0.02
0.03
-0.03 -0.02 -0.01 0 0.01 0.02 0.03
modulation signal at 2 − 6 keVabove 6 keV no modulation
fitting:
S0 + Sm cos ω(t − t0) + Zm sin ω(t − t0)
with t0 = 152, T = 1 yr
T. Schwetz, MPIK, 24 Nov 2008 – p. 19
Can this be explained by DM?
• Yes, the DAMA signal can be explained,• but it is difficult to reconcile it with constraints from
other experiments.
T. Schwetz, MPIK, 24 Nov 2008 – p. 20
Quenching
DAMA measures energy in“electron equivalent” (keVee)
only a fraction q of nuclear recoil energy ER isobservable as scintillation signal in DAMA:
Eobs = q × ER
with qNa = 0.3, qI = 0.09
⇒ the energy threshold of 2 keVee implies athreshold in ER of 6.7 keV for Na and 22 keV for I.
T. Schwetz, MPIK, 24 Nov 2008 – p. 22
Channeling
Drobyshevski, 0706.3095; Bernabei et al., 0710.0288
with a certain probability a recoiling nucleus will not interact withthe crystal but loose its energy only electro-magnetically
for such “channeled” events q ≈ 1T. Schwetz, MPIK, 24 Nov 2008 – p. 23
Channeling
fraction of nuclear recoil events with q ≈ 1
ER (keV)
frac
tion
Iodine recoils
Sodium recoils
10-3
10-2
10-1
1
0 10 20 30 40 50 60
Bernabei et al., 0710.0288
channeling is important for low energy recoils
T. Schwetz, MPIK, 24 Nov 2008 – p. 24
Channeling and DAMA
there are four types of events in the NaI of DAMA:
RDAMA(E) =
∑
x=Na,I
Mx
MNa + MI
{[1 − fx(E/qx)]Rx(E/qx)︸ ︷︷ ︸
quenched
+ fx(E)Rx(E)︸ ︷︷ ︸
channeled
}
T. Schwetz, MPIK, 24 Nov 2008 – p. 25
Channeling and DAMA
there are four types of events in the NaI of DAMA:
★
★
★
★
1 10 100mχ [GeV]
10-42
10-41
10-40
10-39
10-38
σ p [cm
2 ]
1 10 100
Na quench
90%, 99.73% CL (2 dof)
I channel I quench
Na channel fitting DAMA requires
vmin =mχ + M
mχ
√
ER
2M
≈ 400 km/s
⇒
T. Schwetz, MPIK, 24 Nov 2008 – p. 26
Fitting DAMA
★
1 10 100mχ [GeV]
10-42
10-41
10-40
10-39
σ p [cm
2 ]
1 10 100
best fit: mχ = 12 GeV
χ2
min = 36.8 / 34 dof
local minimum: mχ = 51 GeV
χ2
min = 47.9 / 34 dof (∆χ2
= 11.1)
90%, 99.73% CL (2 dof)
T. Schwetz, MPIK, 24 Nov 2008 – p. 27
Fitting DAMA
★
1 10 100mχ [GeV]
10-42
10-41
10-40
10-39
σ p [cm
2 ]
1 10 100
best fit: mχ = 12 GeV
χ2
min = 36.8 / 34 dof
local minimum: mχ = 51 GeV
χ2
min = 47.9 / 34 dof (∆χ2
= 11.1)
90%, 99.73% CL (2 dof)
energy shape of the mod-ulation is importantChang, Pierce, Weiner, 0808.0196Fairbairn, TS, 0808.0704
not included e.g., inGondolo, Gelmini, hep-ph/0504010Petriello, Zurek, 0806.3989
(only two bins: 2-6 keV and 6-14 keV)
T. Schwetz, MPIK, 24 Nov 2008 – p. 27
Energy spectrum of the modulation
0 4 8 12 16 20E [keVee]
-0.01
0
0.01
0.02
0.03
0.04
coun
ts /
kg /
day
/ keV
ee
12 GeV, 1.3e-41 cm2
51 GeV, 7.8e-42 cm2
6 GeV, 2.8e-41 cm2
⇒T. Schwetz, MPIK, 24 Nov 2008 – p. 28
Fitting DAMA
★
1 10 100mχ [GeV]
10-42
10-41
10-40
10-39
σ p [cm
2 ]
1 10 100
best fit: mχ = 12 GeV
χ2
min = 36.8 / 34 dof
local minimum: mχ = 51 GeV
χ2
min = 47.9 / 34 dof (∆χ2
= 11.1)
90%, 99.73% CL (2 dof)
prediction for total ratemust not exceed the ob-served number of eventsChang, Pierce, Weiner, 0808.0196Fairbairn, TS, 0808.0704
T. Schwetz, MPIK, 24 Nov 2008 – p. 29
Prediction for total rate
2 3 4 5 6 7 8 9 10E [keVee]
0
0.5
1
1.5
coun
ts /
kg /
day
/ keV
ee
12 GeV, 1.3e-41 cm2
51 GeV, 7.8e-42 cm2
R(ER) = B(ER) + RDM(ER;mχ, σp) + A(ER;mχ, σp) cos ω(t − t0)
in a given model RDM and A are not independentT. Schwetz, MPIK, 24 Nov 2008 – p. 30
Constraints from other experiments
• CDMS:
exposure threshold M
CDMS-Si (2005) 12 kg day 7 keV 26 GeV
CDMS-Ge (2008) 121.3 kg day 10 keV 67 GeV
both CDMS-Si and CDMS-Ge observe zero events
• XENON10:
7 bins from 4.6 to 26.9 keV, 316 kg day exposure
10 candidate events: (1, 0, 0, 0, 3, 2, 4)
T. Schwetz, MPIK, 24 Nov 2008 – p. 31
DAMA vs CDMS/XENON
★
1 10 100mχ [GeV]
10-42
10-41
10-40
10-39
σ p [cm
2 ]
1 10 100
CD
MS-G
eX
EN
ON
90%, 99.73% CL (2 dof)
DAMA
CDMS-Si
CoGeNT
DAMA 90% CL regionexcluded by 90% CLXENON, CDMS bounds
DAMA and XENONregions touch each otherat 3σ (∆χ2 = 11.2)
χ2min,glob = 62.9/(45 − 2)
(P ≈ 2%)
PPG = 2 × 10−6
T. Schwetz, MPIK, 24 Nov 2008 – p. 32
DAMA vs CDMS/XENON
★
★
1 10 100mχ [GeV]
10-42
10-41
10-40
10-39
σ p [cm
2 ]
1 10 100
CD
MS-G
eX
EN
ON
90%, 99.73% CL (2 dof)
DAMA
CDMS-Si
CoGeNT
DAMAno channeling
DAMA 90% CL regionexcluded by 90% CLXENON, CDMS bounds
DAMA and XENONregions touch each otherat 3σ (∆χ2 = 11.2)
χ2min,glob = 62.9/(45 − 2)
(P ≈ 2%)
PPG = 2 × 10−6
T. Schwetz, MPIK, 24 Nov 2008 – p. 32
Via Lactea
N -body DM halo simulation (234 million particles)Diemand, Kuhlen, Madau, astro-ph/0611370
T. Schwetz, MPIK, 24 Nov 2008 – p. 34
Via Lactea
N -body DM halo simulation (234 million particles)Diemand, Kuhlen, Madau, astro-ph/0611370
0 2 4 6 8 10r [ kpc ]
0.25
0.5
0.75
1
1.25
α
αR
αT
0 2 4 6 8 10r [ kpc ]
0
0.2
0.4
0.6
0.8
f
fR
fT
fitting radial and transvers distribution of Via Lactea data:
1
NRexp
[
−(
v2R
f 2R
)αR]
,2πvT
NTexp
[
−(
v2T
f 2T
)αT]
T. Schwetz, MPIK, 24 Nov 2008 – p. 34
Via Lactea
★
10 100mχ [GeV]
10-42
10-41
10-40
σ p [cm
2 ]
10 100
CD
MS-G
eX
EN
ON
90%, 99.73% CL (2 dof)
DAMA
CDMS-Si
Via Lactea
(a)
χ2min,glob = 62.3/(45 − 2)
(P ≈ 2%)
PPG = 10−6
T. Schwetz, MPIK, 24 Nov 2008 – p. 34
Non-standard Maxwellian halos
★
10 100mχ [GeV]
10-42
10-41
10-40
σ p [cm
2 ]
10 100
CD
MS-G
eX
EN
ON
90%, 99.73% CL (2 dof)
DAMA
CDMS-Si
Maxwellianv = 110 km/s
global
(b)
★
10 100mχ [GeV]
10-42
10-41
10-40
σ p [cm
2 ]
10 100
CD
MS-G
eX
EN
ON
90%, 99.73% CL (2 dof)
DAMA
CD
MS-Si
global
vR = 142 km/s
vT = 63 km/s
(c)
★
10 100mχ [GeV]
10-42
10-41
10-40
σ p [cm
2 ]
10 100
CD
MS-G
eX
EN
ON
90%, 99.73% CL (2 dof)
DAMA
CDMS-Si
vesc = 450 km/s
(d)
T. Schwetz, MPIK, 24 Nov 2008 – p. 35
Non-standard Maxwellian halos
★
10 100mχ [GeV]
10-42
10-41
10-40
σ p [cm
2 ]
10 100
CD
MS-G
eX
EN
ON
90%, 99.73% CL (2 dof)
DAMA
CDMS-Si
Maxwellianv = 110 km/s
global
(b)
★
10 100mχ [GeV]
10-42
10-41
10-40
σ p [cm
2 ]
10 100
CD
MS-G
eX
EN
ON
90%, 99.73% CL (2 dof)
DAMA
CD
MS-Si
global
vR = 142 km/s
vT = 63 km/s
(c)
★
10 100mχ [GeV]
10-42
10-41
10-40
σ p [cm
2 ]
10 100
CD
MS-G
eX
EN
ON
90%, 99.73% CL (2 dof)
DAMA
CDMS-Si
vesc = 450 km/s
(d)
asymmetric halo with small vel. dispersion gives reasonable fitrather extreme assumptions on halo popertiesT. Schwetz, MPIK, 24 Nov 2008 – p. 35
DM streams
Gondolo, Gelmini, hep-ph/0504010; Chang, Pierce, Weiner, 0808.0196
vstr = 900 km/sσstr = 20 km/saligned with sun’s motion3% of halo DM density
marginal solutions appear atmχ ≈ 2 and 4 GeV
T. Schwetz, MPIK, 24 Nov 2008 – p. 36
Beyond spin-independent elastic DM scattering
• spin-dependent scattering• inelastic scattering• DM scattering only on electrons
T. Schwetz, MPIK, 24 Nov 2008 – p. 37
Spin-dependent scattering
in general there is a spin-independent and spin-dependentcontribution to the DM nucleon scattering cross section:
σ = σSI + σSD
with
σSD =32µ2
χG2F
2J + 1
[a2
pSpp(q) + apanSpn(q) + a2nSnn(q)
]
ap, an: couplings to proton and neutron
Spp(q), Spn(q), Snn(q): nuclear structure functions
remember: σSI ≈ σp(µχ/µp)2 A2 |F (q)|2 → A2-enhancement
T. Schwetz, MPIK, 24 Nov 2008 – p. 38
Spin-dependent scattering
coupling mainly to an un-paired nucleon:
neutron proton2311Na even odd12753 I even odd
12954 Xe, 131
54 Xe odd even7332Ge odd even
coupling with proton looks promising for DAMA
T. Schwetz, MPIK, 24 Nov 2008 – p. 39
Spin-dependent scattering
coupling mainly to an un-paired nucleon:
neutron proton2311Na even odd12753 I even odd
12954 Xe, 131
54 Xe odd even7332Ge odd even
coupling with proton looks promising for DAMA
BUT: strong constraint from Super-Kamiokande bound onneutrinos from DM annihilations in the sunSavage, Gelmini, Gondolo, Freese, 0808.3607Hooper, Petriello, Zurek, Kamionkowski, 0808.2464
T. Schwetz, MPIK, 24 Nov 2008 – p. 39
SD scattering: neutron-only coupling
Savage, Gelmini, Gondolo, Freese, 0808.3607
100 101 102 10310-4
10-3
10-2
10-1
100
101
102
103
104
MWIMP HGeVL
ΣΧ
nHp
bL
spin-dependentHap = 0, neutron onlyL CDMS I Si
CDMS II Ge
XENON 10
CoGeNT
TEXONO
CRESST I
DAMA H3Σ�90%Lwith channeling
DAMA H7Σ�5ΣLwith channeling
DAMA H3Σ�90%L
DAMA H7Σ�5ΣL
T. Schwetz, MPIK, 24 Nov 2008 – p. 40
SD scattering: proton-only coupling
Savage, Gelmini, Gondolo, Freese, 0808.3607
100 101 102 10310-4
10-3
10-2
10-1
100
101
102
103
104
MWIMP HGeVL
ΣΧ
pHp
bL
spin-dependentHan = 0, proton onlyL CDMS I Si
CDMS II Ge
XENON 10
Super-K
CoGeNT
TEXONO
CRESST I
DAMA H3Σ�90%Lwith channeling
DAMA H7Σ�5ΣLwith channeling
DAMA H3Σ�90%L
DAMA H7Σ�5ΣL
constraint from COUPP: σpSD . 1 pb @ mχ . 10 GeV
T. Schwetz, MPIK, 24 Nov 2008 – p. 41
Inelastic DM scattering
Tucker-Smith, Weiner, hep-ph/0101138, hep-ph/0402065;Chang, Kribs, Tucker-Smith, Weiner, 0807.2250
• in addition to the DM χ there exists an excitedstate χ∗, with a mass splitting
mχ∗ − mχ = δ ≃ 100 keV ∼ 10−6mχ
• elastic scattering χ + N → χ + N is suppressedwith respect to inelastic scattering
χ + N → χ∗ + N
T. Schwetz, MPIK, 24 Nov 2008 – p. 42
Inelastic DM scattering
0 20 40 60 80 100E
R [keV]
0
200
400
600
800
1000
v min
[km
/s]
GeI, Xe
elastic
inelastic
mχ = 120 GeV, δ = 100 keV
vinelmin =
1√2MER
(MER
µχ
+ δ
)
velmin =
√
MER
2
1
µχ
• sampling only high-velocity tail of velocity distribution
• no events at low recoil energies
• targets with high mass are favouredT. Schwetz, MPIK, 24 Nov 2008 – p. 43
Inelastic DM scattering
Chang, Kribs, Tucker-Smith, Weiner, 0807.2250
leads to very different event spectrum as in case ofelastic scattering (exponentially falling)
T. Schwetz, MPIK, 24 Nov 2008 – p. 44
Inelastic DM scattering
Chang, Kribs, Tucker-Smith, Weiner, 0807.2250
XENON, ZEPLIN, and CRESST have seen already DM!T. Schwetz, MPIK, 24 Nov 2008 – p. 46
DM scattering off electrons
DAMA observes just scitillation light, XENON andCDMS require the coincidence of two signals ⇒
If DM interacted only with electrons, it would not showup in XENON/CDMS but could provide the DAMAannual modulation.
T. Schwetz, MPIK, 24 Nov 2008 – p. 47
DM scattering off electrons
To deposit & 2 keV by χ + e− → χ + e− the electron cannot be atrest ⇒ explore scattering on electrons bound to the nucleus.
mχo (GeV)
E+
(keV
)
p = 0.1 MeV/c
p = 1 MeV/c
p = 5 MeV/c
10-1
1
10
10-1
1 10 102
103
in NaI the e− have p & 0.5 MeVwith a probability ∼ 10−4
max. released energy forvχ = (0.001 − 0.002)c and θ = π
Bernabei et al., 0712.0562
T. Schwetz, MPIK, 24 Nov 2008 – p. 48
DM scattering off electrons
To deposit & 2 keV by χ + e− → χ + e− the electron cannot be atrest ⇒ explore scattering on electrons bound to the nucleus.
mχo (GeV)
ξσe0
(pb)
10-3
10-2
10-1
1
10
10 2
500 1000 1500 2000
in NaI the e− have p & 0.5 MeVwith a probability ∼ 10−4
Bernabei et al., 0712.0562
T. Schwetz, MPIK, 24 Nov 2008 – p. 48
Summary
• DAMA observes an annual modulation of theircount rate at a significance of 8.2σ.The phase is in agreement with DM scattering.
T. Schwetz, MPIK, 24 Nov 2008 – p. 50
Summary
• DAMA observes an annual modulation of theircount rate at a significance of 8.2σ.The phase is in agreement with DM scattering.
• An interpretation of this signal in terms of SIelastic DM scattering is in conflict with boundsfrom XENON and CDMS at the level of 3σ.
T. Schwetz, MPIK, 24 Nov 2008 – p. 50
Summary
• DAMA observes an annual modulation of theircount rate at a significance of 8.2σ.The phase is in agreement with DM scattering.
• An interpretation of this signal in terms of SIelastic DM scattering is in conflict with boundsfrom XENON and CDMS at the level of 3σ.
• Reconciling the data seems to require veryextreme assumptions on DM halo properties.
T. Schwetz, MPIK, 24 Nov 2008 – p. 50
Summary
Beyond spin-independent scattering:
• Spin-dependent scattering on protons can evadethe bounds from XENON and CDMS, but thenstrong constraints from Super-Kamiokandeindirect DM searches apply.
T. Schwetz, MPIK, 24 Nov 2008 – p. 51
Summary
Beyond spin-independent scattering:
• Spin-dependent scattering on protons can evadethe bounds from XENON and CDMS, but thenstrong constraints from Super-Kamiokandeindirect DM searches apply.
• Inelastic DM scattering allows an explanation ofthe DAMA signal which is going to be tested soonby the CRESST experiment.
T. Schwetz, MPIK, 24 Nov 2008 – p. 51
Summary
Beyond spin-independent scattering:
• Spin-dependent scattering on protons can evadethe bounds from XENON and CDMS, but thenstrong constraints from Super-Kamiokandeindirect DM searches apply.
• Inelastic DM scattering allows an explanation ofthe DAMA signal which is going to be tested soonby the CRESST experiment.
• DM scattering off electrons seems to be aphenomenologically valid explanation.
T. Schwetz, MPIK, 24 Nov 2008 – p. 51
Dropping the first energy bin
0 4 8 12 16 20E [keVee]
-0.01
0
0.01
0.02
0.03
0.04
coun
ts /
kg /
day
/ keV
ee
12 GeV, 1.3e-41 cm2
51 GeV, 7.8e-42 cm2
6 GeV, 2.8e-41 cm2
★
1 10mχ [GeV]
10-42
10-41
10-40
10-39
10-38
σ p [cm
2 ]1 10
CD
MS-G
eX
EN
ON
90%, 99.73% CL (2 dof)
DAMA
CDMS-Si
without 1st
bin
global
χ2DAMA,min mDAMA
χ,best χ2glob,min GOF χ2
PG PG mglobχ,best
default 36.8 12 62.9 0.02 26.1 2 × 10−6 8.6
w/o 1st bin 30.3 10 40.4 0.50 10.1 6 × 10−3 3.9
T. Schwetz, MPIK, 24 Nov 2008 – p. 54
Exclusion curves depend on energy threshold
ex.: new evaluation of Leff in XENON:“scintillation yield of Xe for nuclear recoils, relative to thezero-field scintillation yield for electron recoils at 122 keVee.”
Sorensen et al., 0807.0459
ER =S1
LyLeff
Se
Sn
Leff ≈ 0.15 instead of 0.19
at low energies moves thethreshold of 4.6 keV toabout 6 keV
T. Schwetz, MPIK, 24 Nov 2008 – p. 55
Exclusion curves depend on energy threshold
ex.: new evaluation of Leff in XENON:“scintillation yield of Xe for nuclear recoils, relative to thezero-field scintillation yield for electron recoils at 122 keVee.”
E. Aprile @ idm2008, Stockholm
ER =S1
LyLeff
Se
Sn
Leff ≈ 0.15 instead of 0.19
at low energies moves thethreshold of 4.6 keV toabout 6 keV
T. Schwetz, MPIK, 24 Nov 2008 – p. 55
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