Searching for Low Mass Dark Matter with the SuperCDMS SNOLAB Detectors Bruno ¡Serfass ¡ UC ¡Berkeley ¡ PM2018 - 14th Pisa Meeting on Advanced Detectors
SuperCDMS: Searching for Dark Matter Ø For the past 25 years, the CDMS/SuperCDMS Collaboration has been searching for Dark Matter primarily in the form of WIMPs Ø SuperCDMS detectors were in operation at Soudan, Minnesota, until 2015. New detectors will run deeper, in SNOLAB, Canada (operation starting in 2020). �� - �� �� - � DAMIC ¡ Recent SuperCDMS Limits on ��������� �� � �������� �� � �� - �� ������ - �� �� - � � ���� ������ - ������� σ �� [ �� � ] � ���� ������ - ������� σ �� [ �� ] WIMP-Nucleon cross section: � � � � �� - �� �� - � � � � �� - �� �� - � • Low-Mass Dark Matter Search with CDMSlite. Phys. Rev. D 97 (2018) �� - �� �� - � • �� - �� �� - � Results from the Super Cryogenic Dark Matter Search Experiment LUX ¡ �� - �� �� - � at Soudan Phys.Rev.Lett. 120 (2018) �� - �� �� - � • More results coming soon… �� - �� � � � �� ���� ������ ���� [ ��� / � � ] 2 ¡
SuperCDMS: Searching for Dark Matter WIMPs not the only candidate, many well motivated DM models at light mass ¡ 3 ¡ (“US Cosmic Visions: New Ideas in Dark Matter”: 1707.04591)
SuperCDMS: Searching for Dark Matter • SuperCDMS SNOLAB Science Goals: Search for DM at lower Mass: 300 MeV < M DM < 10GeV • Can we probe for DM at even lower masses with SuperCDMS detector technology? ~keV < M DM < 300 MeV 4 ¡ (“US Cosmic Visions: New Ideas in Dark Matter”: 1707.04591)
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Elastic Nuclear Scattering Searching for dark matter with M DM >300MeV: Nuclear recoils Ø The primary design driver for SuperCDMS and all Light χ 0 ¡ γ ¡ Mass experiments is Energy Sensitivity ¡ 6 ¡
Inelastic Electron Scattering Ø To probe M DM <300MeV, we need to look DM DM for DM interactions with more efficiently hidden ! photon transfer kinetic energy to the target kinetic mixing photon è è Electron recoils e - e - Ø The inelastic electron recoil DM F DM µ 1 ê q 2 scattering rate depends strongly 10 - 32 10 - 33 He the size of the target material's XENON10 ER Ar 10 - 34 band gap Xe 10 - 35 Ge 10 - 36 Freeze - In è è Ge preferable s e @ cm 2 D 10 - 37 10 - 38 10 - 39 Ultra - light Dark Photon 10 - 40 Ø Sensitivity depends on threshold ¡ 10 - 41 10 - 42 è è Design driver: semiconductor 10 - 43 1 10 10 2 10 3 detector with sensitivity to m DM @ MeV D single electron-hole pairs (Essig ¡et ¡al ¡1108.5383) ¡ ¡
Inelastic Electron Scattering Ø To probe M DM <300MeV, we need to look DM DM for DM interactions with more efficiently hidden ! photon transfer kinetic energy to the target kinetic mixing photon è è Electron recoils e - e - Ø The inelastic electron recoil DM scattering rate depends strongly the size of the target material's band gap è è Ge preferable Ø Sensitivity depends on threshold ¡ è è Design driver: semiconductor detector with sensitivity to single electron-hole pairs ¡ (Essig ¡et ¡al ¡ ¡1509.01598) ¡
Dark Photon Absorption Ø Analogous to photoelectric absorption, but with a dark photon A' being absorbed Ø Detected through emission of phonons in semiconductor (ensures momentum conservation) Ø Expected signal: Peak at electron recoil energy corresponding to m A' ¡ Band ¡Diagram ¡for ¡Si ¡ Energy ¡[eV] ¡ Momentum ¡ ¡ ¡ 9 ¡
SuperCDMS SNOLAB Detectors Ø High-purity Ge and Si crystals operated at 10’s of mK Ø Measure athermal phonon signal via transition edge sensor Ø Multiple channels give position information Ø Two types of detectors: • Interleaved Z-dependent Ionization and Phonon (iZIP): higher mass DM, optimized for background rejection • High-Voltage (CDMS-HV): lower mass DM, optimized for low threshold 100 ¡mm ¡ 100 ¡mm ¡ 33 ¡mm ¡ 33 ¡mm ¡ 10 ¡ Ge: 1.39 kg, Si: 0.61 kg
iZIP Detectors • Simultaneously ¡measure ¡charge ¡and ¡phonon ¡ energy ¡from ¡dark ¡maCer ¡interacDons ¡ ¡ ¡ • For an electron recoil in Ge, an e-/h+ pair is produced for every 3.0 eV of recoil energy. Nuclear recoils are less efficient, by a factor of 2 to 10 above 1 keVr è è ER/NR discrimination via yield=Ionization E / Recoil E ¡ • Reject ¡surface ¡events ¡via ¡asymmetric ¡charge ¡ signal ¡from ¡interleaved ¡electrodes ¡ ¡ ¡ ¡ ¡ ¡ 11 ¡ (Soudan iZIP data ) ¡ surface-‑event ¡misidenDcaDon ¡prob. ¡<10 -‑5 ¡
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