The next decade in theDirect Detection ofsub-GeV Dark MatterRouven Essig
Yang Institute for Theoretical Physics

Cosmic Controversies, Chicago, Oct 7, 2019

Traditional Direct Detection strategy:
look for nuclear recoils fromelastic WIMP-nucleus scattering

DMDM

e-

lightphonons
electric charge

enucleus

nucleusConstraints & projections from elastic
nuclear recoils
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taking data soon
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large regions ofunexploredparameter space!

Several Well-Motivated Hidden-sector DM Candidates
Can obtain relicabundancefrom���
freeze-out, an initial���
asymmetry, freeze-in,���SIMP, ELDER…

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SMSM

need to probe
nuclear and electroninteractions

Probing sub-GeV DM w/ elastic nuclear recoils
XeSiHe~1
signalsfromrecoiling
nucleus0heat/phononseVelectronic
excitations

keVER• will soon have phonon detectors w/O(1 eV) sensitivity

Dark Matter Mass [MeV]probe 20-50 MeV DM
e.g. M. Pyle et.al. (DoE BRN report)
Hertel, Biekert, Lin,Velan, McKinsey (Superfluid 4He)

Probing sub-GeV DM w/ elastic nuclear recoils
XeSiHe~1signalsfromrecoiling
nucleus0

heat/phononseVelectronic
excitations

keV

ER

• will soon have phonon detectors w/O(1 eV) sensitivity

Dark Matter Mass [MeV]probe 20-50 MeV DM• ultimate sensitivity, to a single~1 meV phonon, probes 1 MeV DMProbing sub-GeV DM w/ elastic nuclear recoils
XeSiHeBut note:

Dark Matter Mass [MeV]To probe DM GeV, look for signals
from “inelastic” processes• Can transfer O(1) of Ekin
• A detector sensitive to:• 1 eV, probes ~500 keV DM(already demonstrated!)

Dark Matter Mass [MeV]To probe DM GeV, look for signals
from “inelastic” processes• Can transfer O(1) of Ekin
• A detector sensitive to:• 1 eV, probes ~500 keV DM(already demonstrated!)• ultimate sensitivity, to a single~1 meV phonon, probes 1 keV DM

Dark Matter Mass [MeV]2
Some Inelastic Processes giving Emax ∼ (1/2)mχ vχ

Electron excitation/ionization in e.g. noble-liquids orsemiconductors (DM-electron scattering)RE, Mardon,Volansky
conduction

bandgap

valencesee also:
Graham, Kaplan, Rajendran, Walters
RE, Manalaysay, Mardon, Sorensen,Volansky
RE, Fernandez-Serra, Mardon, Soto,Volansky,Yu
Derenzo, RE, Massari, Soto,Yu
RE,Volansky,Yu
RE, Sholarpurkar,Yu
Emken, RE, Kouvaris, Sholarpurkar
Derenzo, Bourret, Hanrahan, Bizarri
Lee, Lisanti, Mishra-Sharma, Safdi

noble liquids

semiconductors

Ebinding~10 eV
mthreshold~5 MeV

Ebinding~1 eVmthreshold~500 keV

Typically produces a signal of only one to a few electrons

2
Some Inelastic Processes giving Emax ∼ (1/2)mχ vχ

Electron excitation/ionization in e.g. noble-liquids orsemiconductors (DM-electron scattering)RE, Mardon,Volansky

Measuring small ionization signals is already demonstrated!

two-phase TPCs
(XENON10/100/1T, DarkSide-50)

LBECA

Skipper-CCDs (SENSEI)TES (SuperCDMS)
DEPFET (DANAE)

Planned experiments include
SENSEI (100 g)
DAMIC-M (1 kg)
10 kg Skipper-CCD detector

2Some Inelastic Processes giving Emax ∼ (1/2)mχ vχ

Electron excitation/ionization in e.g. noble-liquids orsemiconductors (DM-electron scattering)RE, Mardon,Volansky

Measuring small ionization signals is already demonstrated!

two-phase TPCs
(XENON10/100/1T, DarkSide-50)

LBECA

Skipper-CCDs (SENSEI)TES (SuperCDMS)
DEPFET (DANAE)

Planned experiments include
SENSEI (100 g)
DAMIC-M (1 kg)
10 kg Skipper-CCD detector

2Some Inelastic Processes giving Emax ∼ (1/2)mχ vχ

Electrons from Migdal effect (DM-nucleus scattering)e.g.Vergados, Ejiri 2004;
Ibe, Nakano, Shoji, Suzuki 2017
Fig. credit: Dolan, Kahlhoefer, McCabe
RE, Pradler, Sholapurkar,Yu
Baxter, Kahn, Krnjaic

A detector sensitive to small ionization signals will besensitive to both DM-e and DM-N interactions(w/ same mass threshold)2Some Inelastic Processes giving Emax ∼ (1/2)mχ vχ

Molecular Excitations (DM-nucleus scattering)
RE, Perez-Rios, Ramani, Slone (2019)

DMDM

e.g. carbon monoxidee.g. carbon monoxideExcited molecule relaxes to ground state emitting
multiple photons of energy O(100-250 meV);detect w/ ultrasensitive photodetectors
probe spin-independent and spin-dependent interactions

2
Some Inelastic Processes giving Emax ∼ (1/2)mχ vχ

Create optical phonons in polar materials,e.g. GaAs, sapphire (DM-phonon scattering)
Knapen, Lin, Pyle, Zurek
Griffin, Knapen, Lin, Zurek

probe sub-MeV DM if have sensitivity to 10’s of meV of phonons

The next decade in sub-GeV DM direct-detection
from DoE High-Energy Physics Basic Research Needs Report����� �)�� ����� ��� �
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regions of parameter space• solid: ready for development• dashed: short-term R&D• dotted: long-term R&D

The next decade in sub-GeV DM direct-detection
from DoE High-Energy Physics Basic Research Needs Report

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• solid: ready for development• dashed: short-term R&D• dotted: long-term R&Dσ� [���]New detection concepts &technological advances enable
exploration of vast new
regions of parameter space

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The next decade in sub-GeV DM direct-detection
from DoE High-Energy Physics Basic Research Needs ReportSome experiments ready soon:(see backup slides)

LBECA (liquid Xe)

SENSEI(silicon Skipper CCDs)

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(see backup slides)σ� [���]Skipper-CCD onballoon/satellite

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���The SENSEI Collaboration“Sub-Electron-Noise Skipper-CCD Experimental Instrument”

Fermilab:•

F. Chierchie, M. Crisler, A. Drlica-Wagner, J. Estrada, G. Fernandez, M. Sofo-Haro,
J. Tiffenberg

Stony Brook:•

N. Bachhawat, L. Chaplinsky, R. Essig, D. Gift, Dawa, S. Munagavalasa, A. Singal

Tel-Aviv:•O. Abramoff, L. Barack, I. Bloch, E. Etzion, A. Orly J. Taenzer, S. Uemura,T. Volansky

U. Oregon:•T.-T. Yu

Fully funded by Heising-Simons Foundation & FermilabDetection Concept
silicon Skipper-CCD~million pixels
developed in collaboration
between FNAL & LBNL
MicroSystems Lab

Detection Concept
silicon Skipper-CCD

DM typically creates only
one or a few electrons per pixel~million pixels

Detection Concept
silicon Skipper-CCD

DM typically creates only
one or a few electrons per pixel~million pixels

Detection Concept
silicon Skipper-CCD

DM typically creates only
one or a few electrons per pixel~million pixels
repeatedly measure charge
to achieve sub-electron
readout noiseDetection Concept
silicon Skipper-CCD

DM typically creates only
one or a few electrons per pixel~million pixels
repeatedly measure charge
to achieve sub-electron
readout noiseDetection Concept
silicon Skipper-CCD

DM typically creates only
one or a few electrons per pixel~million pixels
repeatedly measure charge
to achieve sub-electron
readout noiseDetection Concept
silicon Skipper-CCD

DM typically creates only
one or a few electrons per pixel~million pixels
repeatedly measure charge
to achieve sub-electron
readout noise

Can count individual electrons, w/ ~zero noise
Tiffenberg, Sofo-Haro, Drlica-Wagner, RE, Guardincerri, Holland,Volansky,Yu (1706.00028, PRL)

Si: traditional CCD

Si: Skipper-CCD

electron-hole pairs

electron-hole pairs

rms noise ~3 e-

rms noise ~0.06 e- !

(single measurement)(repeated measurements)

successfully demonstrated by SENSEI in a Fermilab LDRD project

enables a super-sensitive search for DMSENSEI DM constraints from a ~0.1 gram prototype
SENSEI Collaboration,
1804.00088 & 1901.10478, PRL• tiny exposures:surface: ~0.02 gram-days
MINOS: ~0.246 gram-days

SENSEI DM constraints from a ~0.1 gram prototype
SENSEI Collaboration,
1804.00088 & 1901.10478, PRL• tiny exposures:
surface: ~0.02 gram-days
MINOS: ~0.246 gram-days

DAMIC@SNOLAB(w/ ordinary CCDs w/ highquality silicon, 200 gram-days)
1907.12628

SENSEI projection for 100 g of science-grade Skipper-CCDs• orange: “freeze-in DM”
RE, Mardon, Volansky 2011
Chu, Hambye, Tytgat, 2011
RE, Fernandez-Serra, Soto, Mardon, Volansky, Yu 2015
Dvorkin, Lin, Schutz 2019

freeze-in DMSENSEI: 100 g @ SNOLAB(funded, 2020)
new sensors are already being tested[see backup slides for othermodels like SIMP, ELDER,freeze-out, asymmetric]

SENSEI & other planned Skipper-CCD detectors

freeze-in DM

SENSEI: 100 g @ SNOLAB(funded, 2020)
DAMIC-M: 1 kg @ Modane(funded, 2023)
10 kg Skipper-CCD(R&D funding announced last week by DoE)
J. Estrada, A. Chavarria, RE, B. Loer, P. Privitera;
M. Crisler, M. Fernandez-Serra, R. Saldanha, J. Tiffenberg

SENSEI & LBECA have sensitivity also to Nuclear
Interactions from Migdal effect

SENSXENON10 sets
best limit between
5 to 30 MeV

EILBECASENSEI & LBECA
expected to improveby orders ofmagnitude

RE, Pradler, Sholapurkar, Yu
see also Baxter, Kahn, Krnjaic

Summary• A much wider class of DM models are now actively being
considered compared to ~10 years ago, including several wellmotivated sub-GeV DM candidates• Direct detection of sub-GeV DM is now possible, with several
competing proposals• SENSEI and other experiments have first results and will probevast new regions of uncharted territory in next few years

Thank you!

SENSEI sensitivity to Benchmark Models
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• thermal scalar• asymmetric fermion• SIMP• ELDER

Best current constraints on DM-e- scattering>5 MeV from liquid xenon detectors
RE, Mardon, Volansky, 2011

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RE, Manalaysay, Mardon,Sorensen, Volansky, 2012
RE, Volansky, Yu 2017

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σ� [���]XENON1T, 2019��� ���� -��� � �����

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DarkSide-50, 2018����� ������ ��-� ���

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XENON10: 1104.3088

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XENON100: 1605.06262
DarkSide-50: 1802.06998
XENON1T: 1907.11485

The LBECA Collaboration“Low Background Electron Counting Apparatus”

LBNL:•P. Sorensen

LLNL:
•

A. Bernstein, S. Pereverzev, J. Xu

Purdue•F. M. Clark, A. Kopec, R. Lang

Stony Brook:•R. Essig, M. Fernandez-Serra, C. Zhen

UC San Diego:•

K. Ni, J. Long, J. Ye

R&D partially funded by US DoE

Proposed Experiment: LBECA“Low Background Electron Counting Apparatus”
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Bernstein, Clark, RE, Fernandez-Serra,
Kopec, Lang, Long, Ni, Pereverzev,Sorensen, Xu, Ye, Zhen…

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Goal:

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100 kg liquid xenon detector
w/o backgrounds that haveplagued previous detectors�������
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partially funded by DoE
Detector R&D programDetection Concept~
E

PMT’sSensitive to single
electrons!

Xe/Ar gas

But large backgrounds:• delayed e- extraction
across liquid-gas interface

eXe, Ar liquid

PMT’sDM• photoionization ofnegatively charged
impurities• exposed metal surfaces

LBECA: a ~100 kg detector,
ideally w/o these backgrounds

Current bounds on DM w/ large interactions
Emken, RE, Kouvaris, Sholarpurkar

10-22

10-24

assumes dark photon
mediatorσe [cm2 ]

10-26
10-28
NSEI@
protoSE

10-30

surface

HVeV
SM
DCMINOS@
IESN
0
protoSE XENON10
DS-50
10XENON

10-32
10-34

FDM =(αme /q)210-36
100101m χ [MeV]

102103

Surface data (fromprototypes by SENSEI &CDMS-HV) are mostconstraining at high crosssections

A Skipper-CCD on a satellite or balloon
can probe DM with even larger interactions
Emken, RE, Kouvaris, Sholarpurkar

10-1810km)
004(esatellitkm)
03(nballoo-20

10-22

σe [cm2 ]

10-24
10-26
10-28
10-30

iontcetede)cafr
directusand
dnuorg(under10-32
10-34

FDM =(αme /q)210-36
100101m χ [MeV]

102103

Balloon- & satellite-borne
detector being exploredin collaboration w/
scientists at FNAL & JPLIs there a DM model w/ such large interactions?
Emken, RE, Kouvaris, Sholarpurkar

ultralight dark photon mediator

10XQC

ne
ex utripe norim
en
ts

10-16

COLL-18

SLAC
satellite (400km)

10-22

balloon (30km)

S %RR 0.4=χ

10-20(χ =0.4%)

CMB Neff

10-28

RG&H
B

σe [cm2 ]

10-24
10-26

BBN
Neff

10-32

10-34

10-36ag
mht
EarBCM)
1%=( χ(*)

eff
BBN N(*)

Neff
CMB

SNlingpueco

dctionetedirect4% χ = 0.
% χ = 100% χ = 10dicalmche-38100%)
freeze-in (χ =10-40 -1
10100

10Maybe…
a subdominantcomponent of DM
interacting w/ ultralightdark photon?

ieldfcneti

10-30

satellite
balloon

FDM =(αme /q)2101102m χ [MeV]

103104see also 1908.06986, in which
subdominant millicharged DM
interacts w/ CDM, opening up moreparameter space to explain EDGESLiu, Outmezguine, Redigolo, Volansky