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

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

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æ

æ

æ

æ

æ

æ

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

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æ

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æ

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æ

æ

æ

æ

æ

æ

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æ

æ

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

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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

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

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æ

0 100 200 300 4000

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4

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days since 1 1 2010

1.— 1.5 keV

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æ æ

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0 100 200 300 4000

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days since 1 1 2010

1.5— 2. keV

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0 100 200 300 4000

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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 = 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

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æ

æ

æ

0 100 200 300 4000

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4

6

8

days since 1 1 2010

1.— 1.5 keV

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æ

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æ æ

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0 100 200 300 4000

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days since 1 1 2010

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0 100 200 300 4000

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days since 1 1 2010

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æ æ

æ

0 100 200 300 4000

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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

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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

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0 100 200 300 4000

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4

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8

days since 1 1 2010

1.— 1.5 keV

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æ æ

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0 100 200 300 4000

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4

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8

days since 1 1 2010

1.5— 2. keV

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0 100 200 300 4000

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4

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days since 1 1 2010

2.— 2.5 keV

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0 100 200 300 4000

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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