Neutrino Signals at Dark Matter Direct Detection Experiments

Jocelyn Monroe, Royal Holloway, University of London

XXIX International Conference on Neutrino Physics and Astrophysics

June 30, 2020

Dark Matter Direct Detection

γγ

Backgrounds: γ e- ➙ γ e- N ➙ NN ➙ N’ + α, e-

ν N ➙ ν N

experimental requirements: particle ID for recoil N, e-, alpha, n (multiple) final states

Jocelyn Monroe June 30, 2020 / p. 2

Signal: N ➙ N or e- ➙ e-

ν

Backgrounds: γ e- ➙ γ e- N ➙ NN ➙ N’ + α, e-

N ➙ N?

very similar requirements! (and ideally also measure direction) ν

ν

Dark Matter Direct Neutrino Detection

νSignal: ν N ➙ ν N or ν e- ➙ ν e-

Jocelyn Monroe June 30, 2020 / p. 3

2008: Neutrino Backgrounds to Dark Matter Searches and Directionality

Jocelyn Monroe May 30, 2008

2008 2020: Neutrino Backgrounds Signals in Dark Matter Searches (and Directionality)

Jocelyn Monroe May 30, 2008

ν Cross Sections

Z

N

ν ν

N

O(tens) of events/ton-year = ~ 10-46 cm2 limit

An irreducible background, without direction measurement!

JM, P. Fisher, Phys. Rev. D 76:033007 (2007)

ν-N coherent scattering: ~ A2 x (Eν/MeV)2 x 10-44 cm2 recoils are O(10 keV) … neutrino floor in DM searches

Φ(solar B8 ν) = 5.86 x 106 cm-2 s-1

JM, P

. Fis

her,

Phys

. Rev

. D76

(20

07)

J. Dobson, UCLA DM 2018

LZ Projected Nuclear Recoil Backgrounds

circa 2008

Aprile et al., PhysRevLett 123 (2019)

circa 2019

Jocelyn Monroe June 30, 2020 / p. 3

ν Cross Sections

Z

e

ν ν

e

ν-N coherent scattering: ~ A2 x (Eν/MeV)2 x 10-44 cm2 recoils are O(10 keV) … neutrino floor in DM searches

J. Dobson, UCLA DM 2018

LZ Projected Nuclear Recoil Backgrounds

ν-e elastic scattering: smaller by ~ (me / Eν) but recoils are “high” energy ~ Eν and directional!

LZ Projected Electronic Recoil Backgrounds

J. Dobson, UCLA DM 2018

Jocelyn Monroe June 30, 2020 / p. 7

J. D

obso

n, U

CLA

DM

’18

What ν signals can future dark matter detectors see?

https://masterclass.icecube.wisc.edu/en/learn/detecting-neutrinos Jocelyn Monroe June 30, 2020 / p. 8

What ν signals can future dark matter detectors see?

https://masterclass.icecube.wisc.edu/en/learn/detecting-neutrinos Jocelyn Monroe June 30, 2020 / p. 8

Future Large-Mass Dark Matter Detectors

https://lz.slac.stanford.edu/our-research/lz-research

Goal: zeptobarn -> yoctobarn sensitivity to dark matter!

Detector Technology: dual-phase Time Projection Chambers with 4-50 tonne liquid Xe, Ar targets

read out primary scintillation: “S1” + proportional gas scintillation from drifted electrons: “S2” • x-y resolution ~cm • z resolution ~mm

Jocelyn Monroe June 30, 2020 / p. 9

Jocelyn Monroe Jan. 23, 2019

XENON-nT: 6 t LXe (active), following XENON-1T (LNGS), from 2020.

PandaX-4: 4 t LXe (active), following PandaX (JinPing), from 2020.

LZ: 7 t LXe (active), following LUX (SURF), from 2020.

DarkSide-20k: 50 t LAr (LNGS), ArDM+DEAP+DS50+MiniCLEAN, from 2023.

DARWIN: 40 t LXe (LNGS), following XENON-nT.

ARGO: 400 t LAr (SNOLAB?), following DarkSide-20k.

2-Phase TPCs: Near(ish) Future

10

5 cm x 5 cm tiled SiPM

Gamma ray interactions: electron recoil final states rate ~ Ne x (gamma flux), O(1E7) events/(kg day) mis-identified electrons mimic nuclear recoils … part-per-billion level particle ID!

Neutrons: Nuclear recoil final state. (alpha,n), U, Th fission, cosmogenic spallation

n

μ μ

NN*γ

D. Malling, UCLA DM’16

Contamination: 238U and 232Th decays, recoiling progeny and mis-identified alphas, betas mimic nuclear recoils

Jocelyn Monroe June 30, 2020 / p. 11

D. Malling, UCLA DM’16

pp solar neutrinos

20092019

DEAP, +PSD

modified from Malling, UCLA DM’16

N

Backgrounds

Ajaj et al, Phys.Rev..D100 (2019)

Gamma ray interactions: electron recoil final states rate ~ Ne x (gamma flux), O(1E7) events/(kg day) mis-identified electrons mimic nuclear recoils … part-per-billion level particle ID!

Neutrons: Nuclear recoil final state. (alpha,n), U, Th fission, cosmogenic spallation

n

μ μ

NN*γ

D. Malling, UCLA DM’16

Contamination: 238U and 232Th decays, recoiling progeny and mis-identified alphas, betas mimic nuclear recoils

Jocelyn Monroe June 30, 2020 / p. 11

D. Malling, UCLA DM’16

pp solar neutrinos

20092019

DEAP, +PSD

modified from Malling, UCLA DM’16

N

Amaudruz et al, Phys.Rev.Lett. 121 (2018) no.7, 071801

Backgrounds

Ajaj et al, Phys.Rev..D100 (2019)

Gamma ray interactions: electron recoil final states rate ~ Ne x (gamma flux), O(1E7) events/(kg day) mis-identified electrons mimic nuclear recoils … part-per-billion level particle ID!

Neutrons: Nuclear recoil final state. (alpha,n), U, Th fission, cosmogenic spallation

n

μ μ

NN*γ

D. Malling, UCLA DM’16

Contamination: 238U and 232Th decays, recoiling progeny and mis-identified alphas, betas mimic nuclear recoils

Jocelyn Monroe June 30, 2020 / p. 11

D. Malling, UCLA DM’16

pp solar neutrinos

20092019

DEAP, +PSD

modified from Malling, UCLA DM’16

N

Backgrounds

Ajaj et al, Phys.Rev..D100 (2019)

Gamma ray interactions: electron recoil final states rate ~ Ne x (gamma flux), O(1E7) events/(kg day) mis-identified electrons mimic nuclear recoils … part-per-billion level particle ID!

Neutrons: Nuclear recoil final state. (alpha,n), U, Th fission, cosmogenic spallation

n

μ μ

NN*γ

D. Malling, UCLA DM’16

Contamination: 238U and 232Th decays, recoiling progeny and mis-identified alphas, betas mimic nuclear recoils

Jocelyn Monroe June 30, 2020 / p. 11

D. Malling, UCLA DM’16

pp solar neutrinos

20092019

DEAP, +PSD

modified from Malling, UCLA DM’16

N

Backgrounds

Ajaj et al, Phys.Rev..D100 (2019)

+ large, active veto detectors

https://masterclass.icecube.wisc.edu/en/learn/detecting-neutrinos

Neutrino Energy (MeV)-110 1 10

)-1

bin

-1 s

-2 F

lux

(cm

νSo

lar

210

310

410

510

610

710

810

910

1010

1110

1210ppBe7

N13

O15

F17

B8hep

Jocelyn Monroe June 30, 2020 / p. 12

What ν signals can future dark matter detectors see?

Prospects for Solar ν-N Coherent Scattering

Jocelyn Monroe June 30, 2020 / p. 13

DarkSide-20k ESPP 2019

European Strategy for Particle Physics, Physics Briefing Book (2019)

Solar ν-e Event Rates

Jocelyn Monroe June 30, 2020 / p. 14

Neutrino Energy (MeV)-110 1 10

)-1

bin

-1 s

-2 F

lux

(cm

νSo

lar

210

310

410

510

610

710

810

910

1010

1110

1210ppBe7

N13

O15

F17

B8hep

example event rates of solar neutrino-electron elastic scattering at LNGS, per tonne-year of CF4

Z, W

e e

ν ν

e.g. for Ar target: DarkSide-20k estimates 10k solar neutrino- electron elastic scatters above threshold per 100 tonne-yrs

Aalseth, et al. Eur.Phys.J.Plus 133 (2018)

Solar ν-e Event Rates

Jocelyn Monroe June 30, 2020 / p. 15

example event rates of solar neutrino-electron elastic scattering at LNGS, per tonne-year of CF4

Z, W

e e

ν ν

e.g. for Ar target: DarkSide-20k estimates 10k solar neutrino- electron elastic scatters above threshold per 100 tonne-yrs

Aalseth, et al. Eur.Phys.J.Plus 133 (2018)

Statistics even allow solar oscillation physics!

Aalbers, et al. arXiv:2006.03114

Solar ν-e Event Rates

Jocelyn Monroe June 30, 2020 / p. 15

example event rates of solar neutrino-electron elastic scattering at LNGS, per tonne-year of CF4

Z, W

e e

ν ν

e.g. for Ar target: DarkSide-20k estimates 10k solar neutrino- electron elastic scatters above threshold per 100 tonne-yrs

Aalseth, et al. Eur.Phys.J.Plus 133 (2018)

Statistics even allow solar oscillation physics!

Aalbers, et al. arXiv:2006.03114

Solar ν-Electron Scattering

Via neutrino-electron elastic scattering, LAr dark matter experiments can measure CNO (via spectral deformation), and CNO vs. Be-7

+with O(500 t-y), study the “solar metallicity problem”.

exclusion detection

Franco et al., JCAP 1608 (2016) 08 Cerdeno, Davis, Fairbairn, Vincent, JCAP 1804 (2018) 37

*Xe-136 background makes LXe CNO more challenging Baudis et al., JCAP 1401 (2014) 044, Baudis et al., 2006.03114

Jocelyn Monroe June 30, 2020 / p. 16

big opportunities:

1) distinguish between high vs. low metallicity.

Solar ν-Electron Scattering

Via neutrino-electron elastic scattering, LAr dark matter experiments can measure CNO (via spectral deformation), and CNO vs. Be-7

+with O(500 t-y), study the “solar metallicity problem”.

exclusion detection

Franco et al., JCAP 1608 (2016) 08 Cerdeno, Davis, Fairbairn, Vincent, JCAP 1804 (2018) 37

*Xe-136 background makes LXe CNO more challenging Baudis et al., JCAP 1401 (2014) 044, Baudis et al., 2006.03114

Jocelyn Monroe June 30, 2020 / p. 17

big opportunities:

1) distinguish between high vs. low metallicity.

2) study non- standard solar neutrino interactions?

Aprile et al., 2006.09721 Boehm et al., 2006.11250

C. Boehm et al., 2006.11250

Xenon1T data

What neutrino signals can future dark matter detectors see?

Jocelyn Monroe May 3, 2018 / p. 7https://masterclass.icecube.wisc.edu/en/learn/detecting-neutrinos

(if lucky!)

for a supernova at 10 kPc, expect 300-500 ν-N events in near-future experiments. • measure all flavors via NC • measure νe 40Ar e- 40K* • multi-messenger observation:

sub-eV mass ordering?

Lang et al., Phys. Rev. D 94 (2016)

Arnaud et al., Phys.Rev.D.65.033010

What neutrino signals can future dark matter detectors see?

Jocelyn Monroe May 3, 2018 / p. 7https://masterclass.icecube.wisc.edu/en/learn/detecting-neutrinos

(if lucky!)

for a supernova at 10 kPc, expect 300-500 ν-N events in near-future experiments. • measure all flavors via NC • measure νe 40Ar e- 40K* • multi-messenger observation:

sub-eV mass ordering?

Lang et al., Phys. Rev. D 94 (2016)

Arnaud et al., Phys.Rev.D.65.033010

What neutrino signals can future dark matter detectors see?

https://masterclass.icecube.wisc.edu/en/learn/detecting-neutrinos

Anti-Neutrino Energy (MeV)0.5 1 1.5 2 2.5 3 3.5 4 4.5

)-1

s-2

Flu

x (c

mν

Geo

-210

-110

1

10

210

310

410

510U238

U235

Th232

K40

Jocelyn Monroe June 30, 2020 / p. 19

Jocelyn Monroe June 30, 2020 / p. 2

in a 10n T-year exposure…

study with 500 neutrino background events

Contribution from geo-neutrinos is non- to ν-e scattering rate: ~few%

Leyton, Dye, JM, Nature Commun. 8 (2017) 15989

ν-N scattering: Gelmini et al, arXiv:1812.05550

low E dominated by the (not-yet-measured) K-40 (Q = 1.3 MeV).

Example: ν-e elastic scatters per kt-yr at LNGS, on CF4

Jocelyn Monroe June 30, 2020 / p. 2

in a 10n T-year exposure…

study with 500 neutrino background events

Contribution from geo-neutrinos is non- to ν-e scattering rate: ~few%

Leyton, Dye, JM, Nature Commun. 8 (2017) 15989

ν-N scattering: Gelmini et al, arXiv:1812.05550

low E dominated by the (not-yet-measured) K-40 (Q = 1.3 MeV).

Example: ν-e elastic scatters per kt-yr at LNGS, on CF4

• directional dark matter detection studies show 1D direction reconstruction for nuclear recoil final states gains 10x over non-directional measurements in the presence of backgrounds

• 1 mm sampling pitch in drift direction makes direction reconstruction of ~cm length electron tracks feasible in 1D, transverse pitch is a potentially tractable challenge with SiPM readout…

potential increase in sensitivity / reduction in exposure to discovery from electron recoil direction

What about Electron Directionality?

exclusion detection

Mayet, et al., Phys.Rept. 627 (2016)

Jocelyn Monroe June 30, 2020 / p. 21

Aal

seth

et a

l., JI

NST

12

(201

7)

Geo ν-Electron Scattering

challenge: measure the direction of ~1 MeV e- recoils

study with 500 neutrino background events

energy, time, and direction analysis shows sensitivity at 95% CL to measure K-40 flux with O(100) t-yr exposure.

example: geo-, solar-, reactor-ν -induced electron recoil directions, at LNGS.

Jocelyn Monroe June 30, 2020 / p. 22

Leyton, Dye, JM, Nature Commun. 8 (2017) 15989

… potentially opens up measurement of crust vs. mantle flux

diffuse supernovae back- ground: perhaps within reach in large exposures if could reject neutrino scatters! (requires directional nuclear recoil detection)

Jocelyn Monroe May 3, 2018 / p. 7https://masterclass.icecube.wisc.edu/en/learn/detecting-neutrinos

Aprile et al., JCAP04 (2016) 027

What neutrino signals can future dark matter detectors see?

Albers et al., JCAP 1611 (2016)

What neutrino signals can future dark matter detectors see?

https://masterclass.icecube.wisc.edu/en/learn/detecting-neutrinos

Energy (MeV)500 1000 1500 2000 2500 3000 3500 4000

)-1

s-2

Flu

x (c

mν

Atm

osph

eric

-510

-410

-310

-210µν

µνanti-

_eν

_eνanti-

Jocelyn Monroe June 30, 2020 / p. 24

Prospects for Atmospheric ν-N Coherent Scattering

A ν background paradigm…

where the discovery reach is limited by ν flux and cross section uncertainties!

Jocelyn Monroe June 30, 2020 / p. 25

Roszkowski et al., APPEC Dark Matter Review (2020)

Jocelyn Monroe May 3, 2018 / p. 13

What can future dark matter detectors tell us about the neutrino?

Jocelyn Monroe May 3, 2018 / p. 13

What can future dark matter detectors tell us about the neutrino?

exclusion detection

ν-less Double Beta Decay

Xe dark matter searches aim for competitive sensitivity, via restricted fiducial volume (inner 1 t) to reduce backgrounds, and projected 1% energy resolution at the 2ν beta decay endpoint

big opportunity: significant Xe-136 target mass (~600 kg)

big challenges: Th background, energy resolution, and nuclear matrix element uncertainty

example: projected sensitivity in LZ:

Q-value= 2458 keV

P. Bras, IDPASC 2018

Jocelyn Monroe June 30, 2020 / p. 27

exclusion detection

ν-less Double Beta Decay

Xe dark matter searches aim for competitive sensitivity, via restricted fiducial volume (inner 1 t) to reduce backgrounds, and projected 1% energy resolution at the 2ν beta decay endpoint

big opportunity: significant Xe-136 target mass (~600 kg)

big challenges: Th background, energy resolution, and nuclear matrix element uncertainty

P. Bras, IDPASC 2018

Jocelyn Monroe June 30, 2020 / p. 28

recent demonstration of sensitivity to rare processes in XENON1T: Xe-124 2ν double e- capture XENON Collaboration, Nature 568 (2019)

example: Xenon1T energy resolution

Q-value= 2458 keV

Thanks to L. Baudis

1) Sterile neutrino-electron scattering: NS e- νe e-

Sterile ν Signatures

2) The beta decay energy spectrum of background, e.g. Ar-39, is modified by sterile neutrino mixing.

Direct searches: limits on |Ue4|2 at 10 keV mass ~ 0.02 at 90% CL from beta decay measurements

Jocelyn Monroe June 30, 2020 / p. 29

Dragoun, Venos, Phys. 3 (2016) 77-113

Campos & Rodejohann, Phys.Rev.D 94 (2016)

Astrophysical limits on |Ue4|2 at 10 keV mass ~1E=11

1) Sterile neutrino-electron scattering: NS e- νe e-

Sterile ν Signatures

2) The beta decay energy spectrum of background, e.g. Ar-39, is modified by sterile neutrino mixing.

Astrophysical searches: limits on |Ue4|2 at 10 keV are ~1E-11 from x-ray constraints

Jocelyn Monroe June 30, 2020 / p. 26

Dragoun, Venos, Phys. 3 (2016) 77-113

Campos & Rodejohann, Phys.Rev.D 94 (2016)

Sensitivity estimates in range between direct and astrophysical constraints (10-4-10-5)

Astrophysical limits on |Ue4|2 at 10 keV mass ~1E=11 Weinheimer, ESPPU’19

Conclusions & Outlook

Dark matter experiments aspire to study the nature of the neutrino aiming at neutrino-less double beta decay sensitivity, sterile neutrinos,

… and today’s background may be tomorrow’s signal. (T. Kajita, 2015)

Dark matter direct detection technology is approaching the scale where neutrino physics is within reach:

coherent scattering of solar neutrinos, atmospheric neutrinos with large exposures, and geo-neutrino detection potential with very large exposures.

Future dark matter detectors should develop their electron direction measurement capability, to become neutrino telescopes!