Recent Ideas for (Light) Detection

Yonit Hochberg

YH @ DESY Theory Forum, 2020 The is Dark

Dark energy

Dark matter

Atoms u c t g ?? What is it? d s b γ ?? How does it interact? H e µ τ W ??

ν ν# ν $ " Z YH @ DESY Theory Forum, 2020 Past 40 years

YH @ DESY Theory Forum, 2020 WIMP, glorious WIMP*

*Also , of course also axions :-) YH @ DESY Theory Forum, 2020 The WIMP

Correct thermal relic abundance:

For weak coupling, weak scale emerges.

The dominant paradigm for ~40 years.

DM SM

DM SM annihilation

YH @ DESY Theory Forum, 2020 Searching for WIMPs

Direct production Direct detection Indirect detection

Experiments getting increasingly sensitive

Haven’t yet detected dark matter

YH @ DESY Theory Forum, 2020 Great opportunity for new ideas!

YH @ DESY Theory Forum, 2020 Beyond the WIMP

Dark matter mass

[GeV]

Hitoshi @ BCTP, Tahoe 2015

YH @ DESY Theory Forum, 2020 Beyond the WIMP

Dark matter mass

[GeV]

Lots of activity inHitoshi recent @ BCTP, years: Tahoe 2015

Theory & Experiment

YH @ DESY Theory Forum, 2020 New Theory Ideas • …… • Weakly coupled WIMPs [Pospelov, Ritz, Voloshin 2007; Feng, Kumar 2008] • Asymmetric dark matter [Kaplan, Luty, Zurek, 2009] • Freeze-in dark matter [Hall, Jedamzik, March-Russell, West, 2009] • SIMPs [YH, Kuflik, Volansky, Wacker, 2014; YH, Kuflik, Murayama, Volansky, Wacker, 2015] • ELDERs [Kuflik, Perelstein, Rey-Le Lorier, Tsai, 2016 & 2017] • Forbidden dark matter [Griest, Seckall, 1991; D’Agnolo, Ruderman, 2015] • Co-decaying dark matter [Dror, Kuflik, Ng, 2016] • Co-scattering dark matter [D’Agnolo, Pappadopulo, Ruderman, 2017] • …… … Are abundant By no means a comprehensive list

YH @ DESY Theory Forum, 2020 How to detect?

YH @ DESY Theory Forum, 2020 Detection Blueprints

Dark matter particle comes in Hits a target in the lab System reacts Measure the reaction

DM before after DM

e ?? target target* Direct Detection

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What’s going on? [website: supercdms.slac.stanford.edu/

YH @ DESY Theory Forum, 2020 dark-matter-limit-plotter] Current Experiments

Looking for nuclear recoils: think billiard balls DM DM

N

N momentum transfer

2 2 q (mDMv) ENR = = & Ethreshold keV 2mN 2mN ⇠

YH @ DESY Theory Forum, 2020 Current Experiments

Looking for nuclear recoils: think billiard balls

DM DM

N

N doesn’t have enough punch to kick the heavy nuclei

Lose sensitivity @ O(GeV) masses

YH @ DESY Theory Forum, 2020 New Avenues

Light dark matter: scatter off electrons!

DM DM

e

e

light dark matter can give enough punch to kick the light electrons

YH @ DESY Theory Forum, 2020 Energy guideline

2 6 m v 10 m Dark matter scattering: kinetic energy DM ⇠ DM

keV MeV GeV mass (scattering) meV eV keV Edeposit

DM DM

Edeposit

e e

YH @ DESY Theory Forum, 2020 New proposals

semiconductors superconductors atomic ionization Dirac materials (w/ electrons) scintillators

meV eV 2D targets keV Edeposit

superfluid helium color centers (w/ nuclei)

Polar materials

Explosion of interest and ideas in recent times

YH @ DESY Theory Forum, 2020 Ex. #1: First ideas

Atomic ionization Semiconductors

E conduction DM

valence k

Xenon: ~12 eV Ge, Si, Diamond, SiC: ~eV

mDM & 10 MeV mDM & MeV

[Essig , Mardon, Volansky, 2012; [Essig, Mardon, Volansky, 2012] Graham, Kaplan, Rajendran, Walters, 2012; Kurinsky, Yu, YH, Blas, 2019; YH @ DESY Theory Forum, 2020 Griffin, YH, et al, 2020] Ex. #1: First ideas

Atomic ionization Semiconductors

E conduction DM

valence k

Xenon10/100/1T SuperCDMS, SENSEI

mDM & 10 MeV mDM & MeV Are being experimentally realized [Essig , Mardon, Volansky, 2012; [Essig, Mardon, Volansky, 2012] Graham, Kaplan, Rajendran, Walters, 2012; [Essig et al, 2012] Kurinsky, Yu, YH, Blas, 2019; [Xenon100, 2016 & Xenon1T 2020]YH @ DESY Theory Forum, 2020 Griffin, YH, et al, 2020] [SuperCDMS 2020 & SENSEI 2020] Ex. #1: First ideas

Atomic ionization Semiconductors

E conduction DM

valence k

Xenon10/100/1T SuperCDMS, SENSEI

mDM & 10 MeV mDM & MeV

Smaller masses?

YH @ DESY Theory Forum, 2020 Ex. #2: Superconductors

• Ground state = Cooper pairs; Binding energy (gap) meV m keV ⇠ DM ⇠ • The idea: DM scatters with Cooper pairs, deposits enough energy, breaks Cooper pairs à detect

Excitations Excitation concentration Sensor + target philosophy philosophy

[YH, Zhao, Zurek, PRL 2015; [YH, Charaev, Nam, Verma, Colangelo, YH, Pyle, Zhao, Zurek, JHEP 2015] Berggren, PRL 2019]

YH @ DESY Theory Forum, 2020 Ex. #2: Superconductors

• Ground state = Cooper pairs; Binding energy (gap) meV m keV ⇠ DM ⇠ • The idea: DM scatters with Cooper pairs, deposits enough energy, breaks Cooper pairs à detect

Excitations Excitation concentration Sensor + target philosophy philosophy

[YH, Zhao, Zurek, PRL 2015; [YH, Charaev, Nam, Verma, Colangelo, YH, Pyle, Zhao, Zurek, JHEP 2015] Berggren, PRL 2019]

YH @ DESY Theory Forum, 2020 Ex. #2: Superconductors • Superconducting Nanowire Single Photon Detectors (SNSPDs)

Broadly used in quantum information science • Ram an electron, create a hotspot, electrons diffuse away, resistive region across the nanowire à voltage pulse

energy

[YH, Charaev, Nam, Verma, Colangelo, Berggren, PRL 2019]

YH @ DESY Theory Forum, 2020 Ex. #2: Superconductors

Use as simultaneous target + sensor (& multiplex)

DM DM [Existing prototype]

SNSPD

[YH, Charaev, Nam, Verma, Colangelo, Berggren, PRL 2019]

YH @ DESY Theory Forum, 2020 Directional Info?

Lose directional information Retain directional information if detecting secondaries if observe primary!

DM electron

phonons

secondary electrons DM DM

e.g. semiconductors, 2D targets; bulk superconductors graphene (& SNSPDs)

YH @ DESY Theory Forum, 2020 Ex. #3: Graphene

• 2D material with vanishing bandgap conduction

• To eject electron: Eeject = Eb + eV ⇠ valence

Binding energy Work function, O(eV)

Sensitivity to mDM~ MeV • The idea: DM scatters with valence electrons, deposits enough energy, ejects electron à detect

[YH, Kahn, Lisanti, Tully, Zurek, 2017]

YH @ DESY Theory Forum, 2020 Ex. #3: Graphene Electron follows incoming dark matter direction. Naturally gives forward/backward discrimination (separates signal from background)

Electron detected electron not detected

e DM

substrate substrate

12 hours later DM [YH, Kahn, Lisanti, Tully, Zurek, 2017] YH @ DESY Theory Forum, 2020 Ex. #3: Design Concept • ~0.5 kg graphene = area of Jerusalem old city = billions of cm^2 crystals

• Compact geometry: large mass via many stacks

YH @ DESY Theory Forum, 2020 Implement in PTOLEMY Experiment to detect relic neutrinos via capture on tritium.

[Betts et al, 2013]

Will use tritiated graphene (~0.5 kg).

Borrow pure (un-tritiated) graphene for dark matter experiment!

Bare graphene

YH @ DESY Theory Forum, 2020 PTOLEMY world map

YH @ DESY Theory Forum, 2020 Compute Event Rate

[Events/unit time/unit mass]

1 ⇢DM Rate vDM target properties int / ⇢target ⇥ mDM ⇥ ⇥ ⇥

Target density dark matter flux condensed matter particle physics (astrophysics) physics

YH @ DESY Theory Forum, 2020 Scattering Reach

[a few events in kg-year exposure]

Graphene (directional) Amazing reach!

Superconductors DM-electron scattering xsec @ q = ↵me w/ light mediator [Community report, 2017]

YH @ DESY Theory Forum, 2020 Existing Prototype Device

WSi SNSPD, 4.3 nanogram, 0.8 eV threshold, no dark counts in 10000 seconds (~3 hours)

[YH, Charaev, Nam, Verma, Colangelo, Berggren, PRL 2019]

YH @ DESY Theory Forum, 2020 Scattering Reach Colored curves: ���� ������ ���������� ��� ����� �������� Large array, low ����� ���

threshold, low -�� dark count �� New bound: SNSPDs ����������� ����������� WSi SNSPD prototype ��-��

] 4.3ng in 3 hours � μ�-�� �� ���)� ��� [ ����� (��� � ��-�� σ

���)� �-�� ����� (��� ��-��

�� DM-electron )� ��- (�� ��� [YH, Charaev, Nam, scattering ��-�� ����� Verma, Colangelo, xsec @ ���� ���� � �� ��� Berggren, q = ↵m PRL 2019] e ��� [���] w/ light mediator

YH @ DESY Theory Forum, 2020 Downside?

YH @ DESY Theory Forum, 2020 Metals are shiny In-medium effects are substantial – photon picks up mass. If kinetically-mixed hidden photon mediator: 1 scatter In-medium / (q2 m2 )2(1 ⇧ / q) 2)2 V L | | polarization tensor

DM DM

X Kinetically mixed hidden photon

e e

Superconductors take a hit :-(

YH @ DESY Theory Forum, 2020 Ex. #4: Dirac materials

• Think of as 3D bulk graphene [YH, Kahn, Lisanti, Zurek, Grushin, Ilan, Griffin, Liu, • Complementary to superconductors Weber, Neaton, PRD 2017] • Photon remains massless

YH @ DESY Theory Forum, 2020 Scattering Reach

[a few events in kg-year exposure]

Amazing reach!

[YH, Kahn, Lisanti, Zurek, Kinetically mixed hidden Grushin, Ilan, Griffin,Liu, photon mediator Weber, Neaton, PRD 2017] YH @ DESY Theory Forum, 2020 Scattering Reach

[a few events in kg-year exposure]

Directional detection [Geilhuff et al; Coskuner et al; 2019]

[YH, Kahn, Lisanti, Zurek, Kinetically mixed hidden Grushin, Ilan, Griffin,Liu, photon mediator Weber, Neaton, PRD 2017] YH @ DESY Theory Forum, 2020 Any given target material can go even further.

YH @ DESY Theory Forum, 2020 Absorption vs. Scattering

2 6 m v 10 m Dark matter scattering: kinetic energy DM ⇠ DM

keV MeV GeV mass (scattering) meV eV keV Edeposit

DM DM

Edeposit

e e

YH @ DESY Theory Forum, 2020 Absorption vs. Scattering

Dark matter absorption: all the mass-energy m DM

keV MeV GeV mass (scattering) meV eV keV Edeposit

meV eV keV mass (absorption)

phonons DM

electrons YH @ DESY Theory Forum, 2020 Absorption vs. Scattering

Two (mass ranges) for the price of one :-)

keV MeV GeV mass (scattering) meV eV keV Edeposit

meV eV keV mass (absorption)

YH @ DESY Theory Forum, 2020 Absorption Reach ��-� ������� ����������� ��� �����

��������� [projections New bound: for kg-year] ����� WSi SNSPD ��-�� prototype ��������� 4.3ng in 3 hours �� γ ϵ

 ���� �� [Kurinsky, Yu, YH, Blas, -�� ���� �� �� ����� ��� PRD 2019; ������� ��� YH et al, ��� PRL 2019; ������ ����� Δ=��� ��� Griffin, YH, et al, ��-�� 2020] ����� ����� ����� � �� ��� [�� mass] [eV] Kinetically mixed dark photon

YH @ DESY Theory Forum, 2020 Take aways

YH @ DESY Theory Forum, 2020 Outlook

• Lots of activity for light dark matter

• Different targets/processes/detection methods

• By no means exhausted…

• It’s ok for an idea to seem crazy at first

• The best ideas might still be ahead

YH @ DESY Theory Forum, 2020 Prospects

Dark matter int’

WIMP searches

keV MeV GeV mDM

YH @ DESY Theory Forum, 2020 Prospects

Dark matter semiconductors int’ superconductors atomic ionization Dirac materials WIMP searches 2D targets superfluid helium color centers polar crystals scintillators

keV MeV GeV mDM

Burgeoning field in recent years

YH @ DESY Theory Forum, 2020 Prospects

Dark matter semiconductors int’ superconductors atomic ionization Dirac materials WIMP searches 2D targets superfluid helium color centers polar crystals scintillators

keV MeV GeV mDM

Experimentalists are going after these ideas now!

YH @ DESY Theory Forum, 2020 Prospects

Dark matter semiconductors int’ superconductors atomic ionization Dirac materials WIMP searches 2D targets superfluid helium color centers polar crystals scintillators

keV MeV GeV mDM Interface particle physics/condensed matter physics/ quantum information science/precision measurements

YH @ DESY Theory Forum, 2020 If you have any (crazy) new ideas, please be in touch :-)

YH @ DESY Theory Forum, 2020 Thanks!

YH @ DESY Theory Forum, 2020