Direct detection of light dark matter
Joachim Kopp
IDM 2012, Chicago
Fermilab
Joachim Kopp Direct detection of light dark matter 1
Outline
1 Why light WIMPs?
2 Experimental techniques for direct detection of light dark matter
3 Theoretical interpretation of direct detection dataMaterial-dependent scattering cross sectionsDependence on the WIMP velocity distributionLight WIMPs and annual modulationNeutrinos as WIMP impostors
4 Conclusions
Joachim Kopp Direct detection of light dark matter 2
Outline
1 Why light WIMPs?
2 Experimental techniques for direct detection of light dark matter
3 Theoretical interpretation of direct detection dataMaterial-dependent scattering cross sectionsDependence on the WIMP velocity distributionLight WIMPs and annual modulationNeutrinos as WIMP impostors
4 Conclusions
Joachim Kopp Direct detection of light dark matter 3
Hints for light dark matter
On the Earth . . .Plot based on JK Schwetz Zupan 1110.2721
104 6 8 20 30 40 50 607010-43
10-42
10-41
10-40
10- 39
WIMP mass m Χ @GeV D
WIM
P-
nu
cleo
ncr
oss
sect
ion
ΣSI
@cm
2D
í
Limits : 90 %
Countours : 90 %, 3 Σ
v0 = 220 km svesc = 550 km s
CRESST
CD
MS
Xe-
100H
2012L
Xe-
10H
lowthr
.L
DAMA H q ± 10 %L
CoGeNT Hno surface BGL
CoGeNT Hsmall surface BGL
CoGeNTH large surface BGL
Several intriguing directdetection signalsBut severe tension with nullresults
. . . and in the skies
An tentative γ ray excess fromthe Galactic CenterHooper Goodenough 0912.2998, 1010.2752, 1201.1303
I Morphology 6= point source
Radio filamentsLinden Hooper Yusef-Zadeh 1106.5493
Isotropic radio backgroundHooper Belikov Jeltema Linden Profumo Slatyer 1203.3547
Joachim Kopp Direct detection of light dark matter 4
Hints for light dark matter
On the Earth . . .Plot based on JK Schwetz Zupan 1110.2721
104 6 8 20 30 40 50 607010-43
10-42
10-41
10-40
10- 39
WIMP mass m Χ @GeV D
WIM
P-
nu
cleo
ncr
oss
sect
ion
ΣSI
@cm
2D
í
Limits : 90 %
Countours : 90 %, 3 Σ
v0 = 220 km svesc = 550 km s
CRESST
CD
MS
Xe-
100H
2012L
Xe-
10H
lowthr
.L
DAMA H q ± 10 %L
CoGeNT Hno surface BGL
CoGeNT Hsmall surface BGL
CoGeNTH large surface BGL
Several intriguing directdetection signalsBut severe tension with nullresults
. . . and in the skies
An tentative γ ray excess fromthe Galactic CenterHooper Goodenough 0912.2998, 1010.2752, 1201.1303
I Morphology 6= point source
Radio filamentsLinden Hooper Yusef-Zadeh 1106.5493
Isotropic radio backgroundHooper Belikov Jeltema Linden Profumo Slatyer 1203.3547
Joachim Kopp Direct detection of light dark matter 4
Theoretical motivation for light DMConventional DM paradigm: DM has electroweak scale mass,weak scale couplings→ Thermal production→ The WIMP MiracleBut note: Thermal production also possible for lighter DM
An interesting alternative: Asymmetric dark matterI Based on the observation that ΩDM ' 5× ΩbaryonI Suggests related production mechanismsI Baryon abundance determined by matter–antimatter asymmetry
I If DM carries baryon number and mDM ∼ 10mp , the observed ΩDM
could be explained.I Many model-building and phenomenology papers related to this idea:
Kaplan Luty Zurek 0901.4117, Cai Luty Kaplan 0909.5499, Frandsen Sarkar Schmidt-Hober 1103.4350, Frandsen Sarkar 1003.4505,Feldstein Fitzpatrick 1003.5662, An Chen Mohapatra Nussinov Zhang 1004.3296, Cohen Phalen Pierce Zurek 1005.1655, Shelton Zurek
1008.1997, Haba Matsumoto 1008.2487, Davoudiasl Morrissey Sigurdson Tulin 1008.2399, Buckley Randall 1009.0270, Chun1009.0983, Gu Lindner Sarkar Zhang 1009.2690, Blennow Dasgupta Fernandez-Martinez Rius 1009.3159, McDonald 1009.3227, HallMarch-Russell West 1010.0245, Allahverdi Dutta Sinha 1011.1286, Dutta Kumar 1012.1341, Kouvaris Tinyakov 1012.2039, Falkowski
Ruderman Volansky 1101.4936, Graesser Shoemaker Vecchi 1103.2771, McDermott Yu Zurek 1103.5472, Kouvaris Tinyakov 1104.0382,Buckley 1104.1429, Iminniyaz Drees Chen 1104.5548, Bell Petraki Shoemaker Volkas 1105.3730, Chang Goodenough 1105.3976,
Cheung Zurek 1105.4612, Del Nobile Kouvaris Sannino 1105.5431, Masina Sannino 1106.3353, March-Russell McCullough 1106.4319,Davoudiasl Morrissey Sigurdson Tulin 1106.4320, Profumo Ubaldi 1106.4568, Cui Randall Shuve 1106.4834, Graesser Shoemaker
Vecchi 1107.2666, Arina Sahu 1108.3967, Kane Shao Watson Yu 1108.5178, Buckley Profumo 1109.2164, Lewis Pica Sannino1109.3513, Cirelli Panci Servant Zaharijas 1110.3809, Zentner Hearin 1110.5919, Lin Yu Zurek 1111.0293, Cui Randall Shuve1112.2704, Kamada Yamaguchi 1201.2636, Tulin Yu Zurek 1202.0283, Walker 1202.2348, Davoudiasl Mohapatra 1203.1247,
March-Russell Unwin West 1203.4854, Fan Yang Chang 1204.2564, Ellwanger Mitropoulos 1205.0673, Masina Panci Sannino1205.5918, Okada Seto 1205.2844, Blennov Fernandez-Martinez Mena Redondo Serra 1203.5803, . . .
Joachim Kopp Direct detection of light dark matter 5
Theoretical motivation for light DMConventional DM paradigm: DM has electroweak scale mass,weak scale couplings→ Thermal production→ The WIMP MiracleBut note: Thermal production also possible for lighter DMAn interesting alternative: Asymmetric dark matter
I Based on the observation that ΩDM ' 5× ΩbaryonI Suggests related production mechanismsI Baryon abundance determined by matter–antimatter asymmetry
I If DM carries baryon number and mDM ∼ 10mp , the observed ΩDM
could be explained.I Many model-building and phenomenology papers related to this idea:
Kaplan Luty Zurek 0901.4117, Cai Luty Kaplan 0909.5499, Frandsen Sarkar Schmidt-Hober 1103.4350, Frandsen Sarkar 1003.4505,Feldstein Fitzpatrick 1003.5662, An Chen Mohapatra Nussinov Zhang 1004.3296, Cohen Phalen Pierce Zurek 1005.1655, Shelton Zurek
1008.1997, Haba Matsumoto 1008.2487, Davoudiasl Morrissey Sigurdson Tulin 1008.2399, Buckley Randall 1009.0270, Chun1009.0983, Gu Lindner Sarkar Zhang 1009.2690, Blennow Dasgupta Fernandez-Martinez Rius 1009.3159, McDonald 1009.3227, HallMarch-Russell West 1010.0245, Allahverdi Dutta Sinha 1011.1286, Dutta Kumar 1012.1341, Kouvaris Tinyakov 1012.2039, Falkowski
Ruderman Volansky 1101.4936, Graesser Shoemaker Vecchi 1103.2771, McDermott Yu Zurek 1103.5472, Kouvaris Tinyakov 1104.0382,Buckley 1104.1429, Iminniyaz Drees Chen 1104.5548, Bell Petraki Shoemaker Volkas 1105.3730, Chang Goodenough 1105.3976,
Cheung Zurek 1105.4612, Del Nobile Kouvaris Sannino 1105.5431, Masina Sannino 1106.3353, March-Russell McCullough 1106.4319,Davoudiasl Morrissey Sigurdson Tulin 1106.4320, Profumo Ubaldi 1106.4568, Cui Randall Shuve 1106.4834, Graesser Shoemaker
Vecchi 1107.2666, Arina Sahu 1108.3967, Kane Shao Watson Yu 1108.5178, Buckley Profumo 1109.2164, Lewis Pica Sannino1109.3513, Cirelli Panci Servant Zaharijas 1110.3809, Zentner Hearin 1110.5919, Lin Yu Zurek 1111.0293, Cui Randall Shuve1112.2704, Kamada Yamaguchi 1201.2636, Tulin Yu Zurek 1202.0283, Walker 1202.2348, Davoudiasl Mohapatra 1203.1247,
March-Russell Unwin West 1203.4854, Fan Yang Chang 1204.2564, Ellwanger Mitropoulos 1205.0673, Masina Panci Sannino1205.5918, Okada Seto 1205.2844, Blennov Fernandez-Martinez Mena Redondo Serra 1203.5803, . . .
Joachim Kopp Direct detection of light dark matter 5
Outline
1 Why light WIMPs?
2 Experimental techniques for direct detection of light dark matter
3 Theoretical interpretation of direct detection dataMaterial-dependent scattering cross sectionsDependence on the WIMP velocity distributionLight WIMPs and annual modulationNeutrinos as WIMP impostors
4 Conclusions
Joachim Kopp Direct detection of light dark matter 6
Semiconductor detectorsBinding energy of electrons in semiconductor detectors is very small(3 eV in Ge)
I Already a very feeble nuclear recoil leads to excitation
Practical limitation: Electronic noisePossible solution: Reduce capacitance of the device
I Make them smaller — for instance CCDs (DAMIC)DAMIC collaboration 1105.5191
I Change the electrode geometry→ Point-contact detectors (CoGeNT)Luke Goulding. Madden Pehl IEEE Trans. Nucl. Sci. 36 (1989) 926
Barbeau Collar Tench nucl-ex/0701012
↔
CoGeNT Super-CDMS
Joachim Kopp Direct detection of light dark matter 7
Ionization (S2) signals in liquid XenonIonization energy in LXe: O(12 eV)
Actual experimental energy threshold depends on kinematics:I Threshold energy for WIMP–nucleus scattering depends on Leff
F Difficult to measure (requires experiments with low-E neutrons)F Difficult to calculate (interactions of primary recoil nucleus with other Xe atoms
requires complicated many-body dynamics)Brenot et al. Phys. Rev. A 11 (1975) 1245; Ovchinnikov et al. Phys. Rept. 389 (2004) 119
I WIMP–electron scattering very inefficient for O(100 GeV) dark matterJK Niro Schwetz Zupan 0907.3159
I ... but an ideal process for MeV–GeV DMEssig Mardon Volansky 1108.5383, Essig Manalaysay Mardon Sorensen Volansky 1206.2644
1 10 100 10310-39
10-38
10-37
10-36
10-35
10-34
Dark Matter Mass @MeVD
Σe
@cm2
D
Excluded byXENON10 data
1 electron
2 electrons
3 electrons
Hidden-
Photon models
Joachim Kopp Direct detection of light dark matter 8
Ionization (S2) signals in liquid XenonIonization energy in LXe: O(12 eV)Actual experimental energy threshold depends on kinematics:
I Threshold energy for WIMP–nucleus scattering depends on LeffF Difficult to measure (requires experiments with low-E neutrons)F Difficult to calculate (interactions of primary recoil nucleus with other Xe atoms
requires complicated many-body dynamics)Brenot et al. Phys. Rev. A 11 (1975) 1245; Ovchinnikov et al. Phys. Rept. 389 (2004) 119
Primary recoil ion hitsXe atom at rest
Outer electrons rearrangethemselves under the influ-ence of both nuclei.
Some of them may end up inexcited or unbound states
I WIMP–electron scattering very inefficient for O(100 GeV) dark matterJK Niro Schwetz Zupan 0907.3159
I ... but an ideal process for MeV–GeV DMEssig Mardon Volansky 1108.5383, Essig Manalaysay Mardon Sorensen Volansky 1206.2644
1 10 100 10310-39
10-38
10-37
10-36
10-35
10-34
Dark Matter Mass @MeVD
Σe
@cm2
D
Excluded byXENON10 data
1 electron
2 electrons
3 electrons
Hidden-
Photon models
Joachim Kopp Direct detection of light dark matter 8
Ionization (S2) signals in liquid XenonIonization energy in LXe: O(12 eV)Actual experimental energy threshold depends on kinematics:
I Threshold energy for WIMP–nucleus scattering depends on LeffF Difficult to measure (requires experiments with low-E neutrons)F Difficult to calculate (interactions of primary recoil nucleus with other Xe atoms
requires complicated many-body dynamics)Brenot et al. Phys. Rev. A 11 (1975) 1245; Ovchinnikov et al. Phys. Rept. 389 (2004) 119
mχ [GeV]
σn
[cm
2]
DAMA
CoGeNT
!
!
" #$ #" %$
#$!&%
#$!&#
#$!&$
#$!'(
This workRef. [11]Ref. [12]Ref. [26]Ref. [26]
Xenon-10 1104.3088
I WIMP–electron scattering very inefficient for O(100 GeV) dark matterJK Niro Schwetz Zupan 0907.3159
I ... but an ideal process for MeV–GeV DMEssig Mardon Volansky 1108.5383, Essig Manalaysay Mardon Sorensen Volansky 1206.2644
1 10 100 10310-39
10-38
10-37
10-36
10-35
10-34
Dark Matter Mass @MeVD
Σe
@cm2
D
Excluded byXENON10 data
1 electron
2 electrons
3 electrons
Hidden-
Photon models
Joachim Kopp Direct detection of light dark matter 8
Ionization (S2) signals in liquid XenonIonization energy in LXe: O(12 eV)Actual experimental energy threshold depends on kinematics:
I Threshold energy for WIMP–nucleus scattering depends on LeffF Difficult to measure (requires experiments with low-E neutrons)F Difficult to calculate (interactions of primary recoil nucleus with other Xe atoms
requires complicated many-body dynamics)Brenot et al. Phys. Rev. A 11 (1975) 1245; Ovchinnikov et al. Phys. Rept. 389 (2004) 119
I WIMP–electron scattering very inefficient for O(100 GeV) dark matterJK Niro Schwetz Zupan 0907.3159
I ... but an ideal process for MeV–GeV DMEssig Mardon Volansky 1108.5383, Essig Manalaysay Mardon Sorensen Volansky 1206.2644
1 10 100 10310-39
10-38
10-37
10-36
10-35
10-34
Dark Matter Mass @MeVD
Σe
@cm2
D
Excluded byXENON10 data
1 electron
2 electrons
3 electrons
Hidden-
Photon models
Joachim Kopp Direct detection of light dark matter 8
Ionization (S2) signals in liquid XenonIonization energy in LXe: O(12 eV)Actual experimental energy threshold depends on kinematics:
I Threshold energy for WIMP–nucleus scattering depends on LeffF Difficult to measure (requires experiments with low-E neutrons)F Difficult to calculate (interactions of primary recoil nucleus with other Xe atoms
requires complicated many-body dynamics)Brenot et al. Phys. Rev. A 11 (1975) 1245; Ovchinnikov et al. Phys. Rept. 389 (2004) 119
I WIMP–electron scattering very inefficient for O(100 GeV) dark matterJK Niro Schwetz Zupan 0907.3159
I ... but an ideal process for MeV–GeV DMEssig Mardon Volansky 1108.5383, Essig Manalaysay Mardon Sorensen Volansky 1206.2644
1 10 100 10310-39
10-38
10-37
10-36
10-35
10-34
Dark Matter Mass @MeVD
Σe
@cm2
D
Excluded byXENON10 data
1 electron
2 electrons
3 electrons
Hidden-
Photon models
Joachim Kopp Direct detection of light dark matter 8
Outline
1 Why light WIMPs?
2 Experimental techniques for direct detection of light dark matter
3 Theoretical interpretation of direct detection dataMaterial-dependent scattering cross sectionsDependence on the WIMP velocity distributionLight WIMPs and annual modulationNeutrinos as WIMP impostors
4 Conclusions
Joachim Kopp Direct detection of light dark matter 9
Outline
1 Why light WIMPs?
2 Experimental techniques for direct detection of light dark matter
3 Theoretical interpretation of direct detection dataMaterial-dependent scattering cross sectionsDependence on the WIMP velocity distributionLight WIMPs and annual modulationNeutrinos as WIMP impostors
4 Conclusions
Joachim Kopp Direct detection of light dark matter 10
Material-dependent scattering cross sectionsHow can the tension in the global data set — when interpreted in terms ofdark matter scattering — be resolved?
104 6 8 20 30 40 50 607010-43
10-42
10-41
10-40
10- 39
WIMP mass m Χ @GeV D
WIM
P-
nu
cleo
ncr
oss
sect
ion
ΣSI
@cm
2D
í
Limits : 90 %
Countours : 90 %, 3 Σ
v0 = 220 km svesc = 550 km s
CRESST
CD
MS
Xe-
100H
2012L
Xe-
10H
lowthr
.L
DAMA H q ± 10 %L
CoGeNT Hno surface BGL
CoGeNT Hsmall surface BGL
CoGeNTH large surface BGL
Plot based on JK Schwetz Zupan 1110.2721
Isospin-violating DM Feng Kumar MarfatiaSanford 1102.4331
Different couplings to protons andneutrons→ “switch off” xenon
Plot: JK Schwetz Zupan 1110.2721
Inelastic DM Tucker-Smith Weiner hep-ph/0101138
Inelastic scattering→ prefers heavy targets (CRESST!)
30 40 5010-41
10-40
10-39
10-38
10-37
mΧ @GeVD
WIM
P-nu
cleo
ncr
oss
sect
ion
ΣSI
@cm2 D
iDM, ∆=90keV
Limits: 90%
Contours: 90%, 3Σ
v0 = 220 kms, vesc = 550 kms
Xenon
-100
KIM
S
CRESST-II
DAMA
CR
ESST
comm
. run
Plot: JK Schwetz Zupan 1110.2721
Joachim Kopp Direct detection of light dark matter 11
Material-dependent scattering cross sectionsHow can the tension in the global data set — when interpreted in terms ofdark matter scattering — be resolved?
Isospin-violating DM Feng Kumar MarfatiaSanford 1102.4331
Different couplings to protons andneutrons→ “switch off” xenon
-1.2 -1 -0.8 -0.6fn / f
p
10-4
10-3
10-2
10-1
A2 ef
f / A
2
-1.2 -1 -0.8 -0.6
Si / Ca /
O
Na
Ge
I
Xe
W
Plot: JK Schwetz Zupan 1110.2721
Inelastic DM Tucker-Smith Weiner hep-ph/0101138
Inelastic scattering→ prefers heavy targets (CRESST!)
30 40 5010-41
10-40
10-39
10-38
10-37
mΧ @GeVD
WIM
P-nu
cleo
ncr
oss
sect
ion
ΣSI
@cm2 D
iDM, ∆=90keV
Limits: 90%
Contours: 90%, 3Σ
v0 = 220 kms, vesc = 550 kms
Xenon
-100
KIM
S
CRESST-II
DAMA
CR
ESST
comm
. run
Plot: JK Schwetz Zupan 1110.2721
Joachim Kopp Direct detection of light dark matter 11
Material-dependent scattering cross sectionsHow can the tension in the global data set — when interpreted in terms ofdark matter scattering — be resolved?
Isospin-violating DM Feng Kumar MarfatiaSanford 1102.4331
Different couplings to protons andneutrons→ “switch off” xenon
101 102 103
10-41
10-40
10-39
10-38
10-37
mΧ @GeVD
WIM
P-nu
cleo
ncr
oss
sect
ion
Σef
f@cm
2 D
IVDM, fn fp=-0.7
Limits: 90%
Contours: 90%, 3Σ
v0 = 220 kms, vesc = 550 kms
CDMS-SiCDMS low-thr
Xenon-100
KIMS
CRESST-II
DAMA
CRESST comm. run
CDMS
Plot: JK Schwetz Zupan 1110.2721
Inelastic DM Tucker-Smith Weiner hep-ph/0101138
Inelastic scattering→ prefers heavy targets (CRESST!)
30 40 5010-41
10-40
10-39
10-38
10-37
mΧ @GeVD
WIM
P-nu
cleo
ncr
oss
sect
ion
ΣSI
@cm2 D
iDM, ∆=90keV
Limits: 90%
Contours: 90%, 3Σ
v0 = 220 kms, vesc = 550 kms
Xenon
-100
KIM
S
CRESST-II
DAMA
CR
ESST
comm
. run
Plot: JK Schwetz Zupan 1110.2721
Joachim Kopp Direct detection of light dark matter 11
Material-dependent scattering cross sectionsHow can the tension in the global data set — when interpreted in terms ofdark matter scattering — be resolved?
Isospin-violating DM Feng Kumar MarfatiaSanford 1102.4331
Different couplings to protons andneutrons→ “switch off” xenon
101 102 103
10-41
10-40
10-39
10-38
10-37
mΧ @GeVD
WIM
P-nu
cleo
ncr
oss
sect
ion
Σef
f@cm
2 D
IVDM, fn fp=-0.7
Limits: 90%
Contours: 90%, 3Σ
v0 = 220 kms, vesc = 550 kms
CDMS-SiCDMS low-thr
Xenon-100
KIMS
CRESST-II
DAMA
CRESST comm. run
CDMS
Plot: JK Schwetz Zupan 1110.2721
Inelastic DM Tucker-Smith Weiner hep-ph/0101138
Inelastic scattering→ prefers heavy targets (CRESST!)
30 40 5010-41
10-40
10-39
10-38
10-37
mΧ @GeVD
WIM
P-nu
cleo
ncr
oss
sect
ion
ΣSI
@cm2 D
iDM, ∆=90keV
Limits: 90%
Contours: 90%, 3Σ
v0 = 220 kms, vesc = 550 kms
Xenon
-100
KIM
S
CRESST-II
DAMA
CR
ESST
comm
. run
Plot: JK Schwetz Zupan 1110.2721
Joachim Kopp Direct detection of light dark matter 11
Outline
1 Why light WIMPs?
2 Experimental techniques for direct detection of light dark matter
3 Theoretical interpretation of direct detection dataMaterial-dependent scattering cross sectionsDependence on the WIMP velocity distributionLight WIMPs and annual modulationNeutrinos as WIMP impostors
4 Conclusions
Joachim Kopp Direct detection of light dark matter 12
Dependence on the WIMP velocity distributionConventional assumption:
f (v) ∝(
exp[− v2/v2
0]− exp
[− v2
esc/v20])
Θ(vesc − v)
However, N-body simulations predict deviations from this simple form
200 250 300 350 400 450 500 550
0.01
0.050.10
0.501.00
5.00
v kms
v2fv1
03
200 250 300 350 400 4500.01
0.050.10
0.501.00
5.00
v kms
v2fv1
03
200 300 400 500 600
0.01
0.050.10
0.501.00
5.00
v kms
v2fv1
03
200 250 300 350 400 450 500 550
0.01
0.050.10
0.501.00
5.00
v kms
v2fv1
03
Aquariusvesc ~ 565 km/s
GHALOvesc ~ 433 km/s
Ling et al.vesc ~ 520 km/s
0 100 200 300 400 500 6000
1
2
3
4
0 100 200 300 400 500 6000
1
2
3
4
0 100 200 300 400 500
1
2
3
4
5
0 100 200 300 4000
1
2
3
4
5
6
Via Lacteavesc ~ 550 km/s
v2f(v
)×
10−
3v2
f(v
)×
10−
3
v (km/s) v (km/s)
Lisanti Strigari Wacker Wechsler 1010.4300
Also: Streams and debris flow Lisanti Spergel 1105.4166, Kuhlen Lisanti Spergel 1202.0007
Joachim Kopp Direct detection of light dark matter 13
Dependence on the WIMP velocity distribution
4 6 8 10 12 1410-41
10-40
10-39
10-38
MDM in GeV
ΣS
Iin
cm2
DAMA
CR
Xe100Xe10
Xe10
Si
Si
Ge
C Cl F
standard
fp fn = 1
v0 = 270 kms
vesc = 500 kms
qNa=0.3
Χ2 = 242., 50.4
Farina Pappadopulo Strumia Volansky 1107.0715
Joachim Kopp Direct detection of light dark matter 14
Dependence on the WIMP velocity distribution
4 6 8 10 12 1410-41
10-40
10-39
10-38
MDM in GeV
ΣS
Iin
cm2
DAMA
CR
Xe100Xe10
Xe10
SiSi
Ge
C Cl F
standard
fp fn = 1
v0 = 220 kms
vesc = 600 kms
qNa=0.3
Χ2 = 255., 73.2
Farina Pappadopulo Strumia Volansky 1107.0715
Joachim Kopp Direct detection of light dark matter 14
Dependence on the WIMP velocity distribution
4 6 8 10 12 1410-41
10-40
10-39
10-38
MDM in GeV
ΣS
Iin
cm2
DAMA
CR
Xe100Xe10
Xe10
SiSi
Ge
C Cl F
standard
fp fn = 1
v0 = 220 kms
vesc = 500 kms
qNa=0.3
Χ2 = 249., 72.0
Farina Pappadopulo Strumia Volansky 1107.0715
Joachim Kopp Direct detection of light dark matter 14
Dependence on the WIMP velocity distribution
4 6 8 10 12 1410-41
10-40
10-39
10-38
MDM in GeV
ΣS
Iin
cm2
DAMA
CR
Xe100Xe10
Xe10
SiGe
C Cl F
k = 3
fp fn = 1
v0 = 220 kms
vesc = 500 kms
qNa=0.3
Χ2 = 250., 72.3
Farina Pappadopulo Strumia Volansky 1107.0715
Joachim Kopp Direct detection of light dark matter 14
Outline
1 Why light WIMPs?
2 Experimental techniques for direct detection of light dark matter
3 Theoretical interpretation of direct detection dataMaterial-dependent scattering cross sectionsDependence on the WIMP velocity distributionLight WIMPs and annual modulationNeutrinos as WIMP impostors
4 Conclusions
Joachim Kopp Direct detection of light dark matter 15
Light WIMPs and annual modulationFor light WIMPs, detectors are probing the tail of the velocity distribution→ Larger fractional annual modulation expected
Mass (GeV)210 310
)A
vera
ge)/
(2R
Win
ter
-RS
umm
er(R
-0.1
-0.05
0
0.05
0.1
0.15
0.2
0.25
0.310 ton*year Xenon
50 ton*year Argon
XenonArgon
Arisaka et al. 1107.1295
Joachim Kopp Direct detection of light dark matter 16
Light WIMPs and annual modulationFor light WIMPs, detectors are probing the tail of the velocity distribution→ Larger fractional annual modulation expected
What would reduced annual modulation in the new CoGeNT data mean forthe DM interpretation?
Plot based on Fox JK Lisanti Weiner 1107.0717 and JK Schwetz Zupan 1110.2721
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0 100 200 300 4000
2
4
6
8
10
12
14
days since 1 1 2010
Eve
nts
Hke
Vkg
day
L
0.5— 1. keV
SI scattering æ
æ
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æ
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æ
æ
æ
æ
æ
æ
æ
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æ
æ
0 100 200 300 4000
2
4
6
8
days since 1 1 2010
1.— 1.5 keV
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æ
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æ æ
ææ
æ
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æ
0 100 200 300 4000
2
4
6
8
days since 1 1 2010
1.5— 2. keV
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æ
0 100 200 300 4000
2
4
6
8
days since 1 1 2010
2.— 2.5 keV
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æ æ
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ææ
æ æ
æ
0 100 200 300 4000
2
4
6
8
days since 1 1 2010
2.5— 3. keV
Data points: CoGeNT, 1106.0650 (after subtraction of known cosmogenic peaks)Red curve: Prediction (signal + BG @ best fit) for spin-independent scattering
Extra surface BG = 0 keV−1day−1 × exp(− E/0.3keV
)(signal fraction in 0.5–1 keV bin = 73%)
Joachim Kopp Direct detection of light dark matter 16
Light WIMPs and annual modulationFor light WIMPs, detectors are probing the tail of the velocity distribution→ Larger fractional annual modulation expected
What would reduced annual modulation in the new CoGeNT data mean forthe DM interpretation?
Plot based on Fox JK Lisanti Weiner 1107.0717 and JK Schwetz Zupan 1110.2721
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æ æ
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0 100 200 300 4000
2
4
6
8
10
12
14
days since 1 1 2010
Eve
nts
Hke
Vkg
day
L
0.5— 1. keV
SI scattering æ
æ
æ
æ
æ
æ
æ
æ
æ
æ
æ
æ
æ
æ
æ
0 100 200 300 4000
2
4
6
8
days since 1 1 2010
1.— 1.5 keV
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æ æ
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æ
æ
0 100 200 300 4000
2
4
6
8
days since 1 1 2010
1.5— 2. keV
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0 100 200 300 4000
2
4
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8
days since 1 1 2010
2.— 2.5 keV
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æ æ
æ
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æ
ææ
æ æ
æ
0 100 200 300 4000
2
4
6
8
days since 1 1 2010
2.5— 3. keV
Data points: CoGeNT, 1106.0650 (after subtraction of known cosmogenic peaks)Red curve: Prediction (signal + BG @ best fit) for spin-independent scattering
Extra surface BG = 12 keV−1day−1 × exp(− E/0.3keV
)(signal fraction in 0.5–1 keV bin = 46%)
Joachim Kopp Direct detection of light dark matter 16
Light WIMPs and annual modulationFor light WIMPs, detectors are probing the tail of the velocity distribution→ Larger fractional annual modulation expected
What would reduced annual modulation in the new CoGeNT data mean forthe DM interpretation?
Plot based on Fox JK Lisanti Weiner 1107.0717 and JK Schwetz Zupan 1110.2721
æ
æ
æ
æ
æ
æ
æ
ææ
æ
æ
æ æ
æ
æ
0 100 200 300 4000
2
4
6
8
10
12
14
days since 1 1 2010
Eve
nts
Hke
Vkg
day
L
0.5— 1. keV
SI scattering æ
æ
æ
æ
æ
æ
æ
æ
æ
æ
æ
æ
æ
æ
æ
0 100 200 300 4000
2
4
6
8
days since 1 1 2010
1.— 1.5 keV
æ
æ
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æ æ
ææ
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æ
0 100 200 300 4000
2
4
6
8
days since 1 1 2010
1.5— 2. keV
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0 100 200 300 4000
2
4
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days since 1 1 2010
2.— 2.5 keV
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æ æ
æ
æ
æ
ææ
æ æ
æ
0 100 200 300 4000
2
4
6
8
days since 1 1 2010
2.5— 3. keV
Data points: CoGeNT, 1106.0650 (after subtraction of known cosmogenic peaks)Red curve: Prediction (signal + BG @ best fit) for spin-independent scattering
Extra surface BG = 24 keV−1day−1 × exp(− E/0.3keV
)(signal fraction in 0.5–1 keV bin = 30%)
Joachim Kopp Direct detection of light dark matter 16
Light WIMPs and annual modulationFor light WIMPs, detectors are probing the tail of the velocity distribution→ Larger fractional annual modulation expected
What would reduced annual modulation in the new CoGeNT data mean forthe DM interpretation?
Plot based on Fox JK Lisanti Weiner 1107.0717 and JK Schwetz Zupan 1110.2721
æ
æ
æ
æ
æ
æ
æ
ææ
æ
æ
æ æ
æ
æ
0 100 200 300 4000
2
4
6
8
10
12
14
days since 1 1 2010
Eve
nts
Hke
Vkg
day
L
0.5— 1. keV
SI scattering æ
æ
æ
æ
æ
æ
æ
æ
æ
æ
æ
æ
æ
æ
æ
0 100 200 300 4000
2
4
6
8
days since 1 1 2010
1.— 1.5 keV
æ
æ
æ
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æ
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æ æ
ææ
æ
æ
æ
æ
0 100 200 300 4000
2
4
6
8
days since 1 1 2010
1.5— 2. keV
æ
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0 100 200 300 4000
2
4
6
8
days since 1 1 2010
2.— 2.5 keV
æ
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æ æ
æ
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ææ
æ æ
æ
0 100 200 300 4000
2
4
6
8
days since 1 1 2010
2.5— 3. keV
Data points: CoGeNT, 1106.0650 (after subtraction of known cosmogenic peaks)Red curve: Prediction (signal + BG @ best fit) for spin-independent scattering
When surface backgrounds are accounted for, reduced modulation inCoGeNT would make the data more consistent with a WIMP hypothesis
Joachim Kopp Direct detection of light dark matter 16
Outline
1 Why light WIMPs?
2 Experimental techniques for direct detection of light dark matter
3 Theoretical interpretation of direct detection dataMaterial-dependent scattering cross sectionsDependence on the WIMP velocity distributionLight WIMPs and annual modulationNeutrinos as WIMP impostors
4 Conclusions
Joachim Kopp Direct detection of light dark matter 17
Neutrinos as WIMP impostorsSolar neutrinos are a well-known background to future direct DM searches:
see e.g. Gütlein et al. arXiv:1003.5530
dσSM(νN → νN)
dEr=
G2F mNF 2(Er )
2πE2ν
[A2E2
ν + 2AZ (2E2ν (s2
w − 1)− Er mNs2w )
+ 4Z 2(E2ν + s4
w (2E2ν + E2
r − Er (2Eν + mN)) + s2w (Er mN − 2E2
ν ))],
ææ
æ
ææææææææææææææææææææææææææææææææææ
10-1 100 101 102 103 10410-1410-1310-1210-1110-1010-910-810-710-610-510-410-310-210-1100101102
Erec HkeVL
coun
tsN
Ak
eVy
ear
electron recoil
DAMA
Borexino
XENON100 e-
CoGeNT
pp7Be
13N 15Opep
8B17F
hepSM total rateComponents
10-4 10-3 10-2 10-1 100 10110-2
10-1
100
101
102
103
104
105
106
107
108
Erec HkeVL
coun
tsto
nke
Vy
ear
Nuclear recoil - Ge
pp7Be
13N 15Opep
8B
17F
hep
CoGeNT
CDMS-II
SM total rateComponents
Plots from Harnik JK Machado 1202.6073
Joachim Kopp Direct detection of light dark matter 18
Neutrinos as WIMP impostorsSolar neutrinos are a well-known background to future direct DM searches:
see e.g. Gütlein et al. arXiv:1003.5530
dσSM(νN → νN)
dEr=
G2F mNF 2(Er )
2πE2ν
[A2E2
ν + 2AZ (2E2ν (s2
w − 1)− Er mNs2w )
+ 4Z 2(E2ν + s4
w (2E2ν + E2
r − Er (2Eν + mN)) + s2w (Er mN − 2E2
ν ))],
SM signal will only become sizeable in multi-ton detectors
But: New physics can enhance the rate
⇒ New ν physics can be confused with a dark matter signal
⇒ DM detectors can search for new physics in the ν sector
Joachim Kopp Direct detection of light dark matter 18
Enhanced neutrino scattering from BSM physicsHarnik JK Machado 1202.6073
æ
æ
æ
æ æææææææææææææææææææææææææææææææææ
10-1 100 101 102 10310-8
10-7
10-6
10-5
10-4
10-3
10-2
10-1
100
101
102
Erec HkeVeeL
coun
tsN
Ak
eVee
yea
r
electron recoil
DAMA
Borexino
XENON100 e-
CoGeNT
Standard model
B
C
DA
Line MA¢ gegΝ
A ΜΝ = 0.32 ´ 10-10ΜB
B 10 keV 4 ´ 10-12
C 50 keV 4 ´ 10-12
D 250 keV 6 ´ 10-12
A: ν magnetic moment
B, C, D: kinetically mixed A′ + sterile νs :
L ⊃ −14
F ′µνF ′µν −
14
FµνFµν −12
εF ′µνFµν
+ νs i /∂νs + g′νsγµνsA′µ
− (νL)cmνLνL − (νs)cmνs νs − (νL)cmmixνs
Enhanced scattering at low Er for light A′
Negligible compared to SM scattering at energies probed in dedicated neutrino experimentsVarious mechanisms for daily and annual modulation Pospelov 1103.3261, Harnik JK Machado 1202.6073
Joachim Kopp Direct detection of light dark matter 19
Enhanced neutrino scattering from BSM physicsHarnik JK Machado 1202.6073
æ
æ
æ
æ æææææææææææææææææææææææææææææææææ
10-1 100 101 102 10310-8
10-7
10-6
10-5
10-4
10-3
10-2
10-1
100
101
102
Erec HkeVeeL
coun
tsN
Ak
eVee
yea
r
electron recoil
DAMA
Borexino
XENON100 e-
CoGeNT
Standard model
B
C
DA
Line MA¢ gegΝ
A ΜΝ = 0.32 ´ 10-10ΜB
B 10 keV 4 ´ 10-12
C 50 keV 4 ´ 10-12
D 250 keV 6 ´ 10-12
10-4 10-3 10-2 10-1 100 10110-2
10-1
100
101
102
103
104
105
106
107
108
Erec HkeVnrLco
unts
ton
keV
nry
ear
Nuclear recoil –Ge
CoGeNT
CDMS-II
D
C
B
A
Standard model
Line MA¢ gNgΝ sin2Θ24
A ΜΝ = 0.32 ´ 10-10ΜB activeB 100 MeV 9 ´ 10-8 activeC 100 MeV 8 ´ 10-7 0.02D 10 MeV 10-6 0.02
A: ν magnetic moment A: ν magnetic momentB, C, D: kinetically mixed A′ + sterile νs B: U(1)B−L boson
C: kinetically mixed U(1)′ + sterile νD: U(1)B + sterile ν charged under U(1)B
Pospelov 1103.3261, Pospelov Pradler 1203.0545
Enhanced scattering at low Er for light A′
Negligible compared to SM scattering at energies probed in dedicated neutrino experimentsVarious mechanisms for daily and annual modulation Pospelov 1103.3261, Harnik JK Machado 1202.6073
Joachim Kopp Direct detection of light dark matter 19
Outline
1 Why light WIMPs?
2 Experimental techniques for direct detection of light dark matter
3 Theoretical interpretation of direct detection dataMaterial-dependent scattering cross sectionsDependence on the WIMP velocity distributionLight WIMPs and annual modulationNeutrinos as WIMP impostors
4 Conclusions
Joachim Kopp Direct detection of light dark matter 20
Summary and conclusionsSeveral intriguing experimental hints for . 10 GeV DMTheoretical motivation in asymmetric DM scenarios, but can beaccomodated in many popular DM modelsDirect detection of light dark matter requires new experimental techniquesCurrently, data from different experiments contradict each other
I CoGeNT, DAMA, CRESST see unexplained signalsI Strong exclusion from Xenon-100, CDMS, . . . (under standard assumptions)I Note: Reduced modulation removes tension within the CoGeNT data
Ways out:I Material-dependent scattering cross sections?
(isospin-violating DM, inelastic DM)I New physics in the neutrino sector can fake WIMP signals
Joachim Kopp Direct detection of light dark matter 21
Thank you!
Bonus slides
Example: A model with a 4th neutrinoIntroduce a 4th neutrino νs and a light U(1)′ gauge boson A′ (hidden photon)
Harnik JK Machado 1202.6073related model with gauged U(1)B first discussed by Pospelov 1103.3261
see also Pospelov Pradler 1203.0545
νs charged under U(1)′ → direct coupling to A′
SM particles couple to A′ only through kinetic mixing
L ⊃ −14
F ′µνF ′µν − 1
4FµνFµν − 1
2εF ′
µνFµν + νs i /∂νs + g′νsγµνsA′
µ
− (νL)cmνLνL − (νs)cmνsνs − (νL)cmmixνs
A small fraction of solar neutrinos can oscillate into νs
νs scattering cross section in the detector given by
dσA′(νse → νse)
dEr=
ε2e2g′2me
4πp2ν(M2
A′ + 2Er me)2
[2E2
ν + E2r − 2Er Eν − Er me −m2
ν
]Joachim Kopp Direct detection of light dark matter 24
Temporal modulation of neutrino signalsSignals of new light force mediators and/or sterile neutrinos can showseasonal modulation:
The Earth–Sun distance: Solar neutrino flux peaks in winter.
Active–sterile neutrino oscillations: For oscillation lengths . 1 AU, sterileneutrino appearance depends on the time of year.Sterile neutrino absorption: For strong νs–A′ couplings and not-too-weakA′–SM couplings, sterile neutrino cannot traverse the Earth.→ lower flux at night. And nights are longer in winter.Earth matter effects: An MSW-type resonance can lead to modified fluxof certain neutrino flavors at night. And nights are longer in winter.
Joachim Kopp Direct detection of light dark matter 25
Temporal modulation of neutrino signalsSignals of new light force mediators and/or sterile neutrinos can showseasonal modulation:
The Earth–Sun distance: Solar neutrino flux peaks in winter.Active–sterile neutrino oscillations: For oscillation lengths . 1 AU, sterileneutrino appearance depends on the time of year.
Harnik JK Machado, arXiv:1202.6073
Sterile neutrino absorption: For strong νs–A′ couplings and not-too-weakA′–SM couplings, sterile neutrino cannot traverse the Earth.→ lower flux at night. And nights are longer in winter.Earth matter effects: An MSW-type resonance can lead to modified fluxof certain neutrino flavors at night. And nights are longer in winter.
Joachim Kopp Direct detection of light dark matter 25
Temporal modulation of neutrino signalsSignals of new light force mediators and/or sterile neutrinos can showseasonal modulation:
The Earth–Sun distance: Solar neutrino flux peaks in winter.Active–sterile neutrino oscillations: For oscillation lengths . 1 AU, sterileneutrino appearance depends on the time of year.Sterile neutrino absorption: For strong νs–A′ couplings and not-too-weakA′–SM couplings, sterile neutrino cannot traverse the Earth.→ lower flux at night. And nights are longer in winter.
Earth matter effects: An MSW-type resonance can lead to modified fluxof certain neutrino flavors at night. And nights are longer in winter.
Joachim Kopp Direct detection of light dark matter 25
Temporal modulation of neutrino signalsSignals of new light force mediators and/or sterile neutrinos can showseasonal modulation:
The Earth–Sun distance: Solar neutrino flux peaks in winter.Active–sterile neutrino oscillations: For oscillation lengths . 1 AU, sterileneutrino appearance depends on the time of year.Sterile neutrino absorption: For strong νs–A′ couplings and not-too-weakA′–SM couplings, sterile neutrino cannot traverse the Earth.→ lower flux at night. And nights are longer in winter.Earth matter effects: An MSW-type resonance can lead to modified fluxof certain neutrino flavors at night. And nights are longer in winter.
Joachim Kopp Direct detection of light dark matter 25
Hidden photons
L ⊃ −14
F ′µνF ′µν − 1
4FµνFµν − 1
2εF ′
µνFµν + νs i /∂νs + g′νsγµνsA′
µ
10-24 10-21 10-18 10-15 10-12 10-9 10-6 10-3 110-16
10-14
10-12
10-10
10-8
10-6
10-4
10-210-24 10-21 10-18 10-15 10-12 10-9 10-6 10-3 1
10-16
10-14
10-12
10-10
10-8
10-6
10-4
10-2
Dark Photon Mass MA'HGeVL
Kin
etic
mix
ing
Ε
Fixedtarget
Kinetically Mixed Gauge Boson
Hg-2LΜ
Hg-2Le
U
SN1987A
Atomic PhysicsAtomic Physics
CMB
Glo
bula
rC
lust
ers
SunGlobular Clusters, energy loss via Νs
Hin models with d 10 keV sterile neutrinosL
Sun
A' capture in SunHpartly allowedL
CASTCMB
LSW
gΝ2 sin22Θ=10-4
gΝ2 sin22Θ=10-12
Borexino Hin models with UH1L'-charged sterile ΝL
Constraints from Jaeckel Ringwald 1002.0329, Redondo 0801.1527,Bjorken Essig Schuster Toro 0906.0580, Dent Ferrer Krauss 1201.2683, Harnik JK Machado 1202.6073
Joachim Kopp Direct detection of light dark matter 26