Recent Ideas for (Light) Dark Matter Detection Yonit Hochberg YH @ DESY Theory Forum, 2020 The Universe 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 axions, 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 ���������� -�� -� �� ������ ����-� �� ���� ] - ����� ] � -�� �� ������� -� �� �� �� [ �� [ ������ -��� ������ ������ �� �� σ σ -��� � -�� ������ �� �� -� ����� - �� - ��������� �� �� ��� � ������ �� -���� ��� ���� -�� - �������� ������� -�� � -� ������� �� �� - - ��-�� ������� ��-�� ���� ������ ���� ������ ��-�� ��-�� ��-�� � �� ��� ���� ���� ������ ���� [���/��] 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 light dark matter 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 + Φ 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 σint / ⇢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 σscatter 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