Signals at 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

Signal: N ➙ N or e- ➙ e-

Backgrounds: γ e- ➙γe- N ➙ N N ➙N’ + α, e- νN ➙νN

experimental requirements: particle ID for recoil N, e-, alpha, n (multiple)γ final states γ June 30, 2020 / p. 2 Dark Matter Direct Neutrino Detection

Signal: ν N ➙ ν N or ν e- ➙ ν e- ν ν

Backgrounds: γ e- ➙γe- N ➙ N N ➙N’ + α, e- N ➙N?

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

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

Z

Φ(solar B8 ν) = 5.86 x 106 cm-2 s-1 N N Aprile et al., PhysRevLett 123 (2019) LZ Projected Nuclear Recoil Backgrounds J. Dobson, UCLA DM 2018 circa O(tens) of events/ton-year = 2008 ~ 10-46 cm2 limit

JM, P. Fisher, Phys. Rev. D76 (2007) Rev. Phys. Fisher, JM, P. circa An irreducible background,2019 without direction measurement! JM, P. Fisher, Phys. Rev. D 76:033007 (2007)

Jocelyn Monroe June 30, 2020 / p. 3 ν Cross Sections

2 2 -44 2 ν-N coherent scattering: ~ A x (Eν/MeV) x 10 cm recoils are O(10 keV) … neutrino floor in DM searches ν ν-e elastic scattering: smaller by ~ (me / Eν) ν but recoils are “high” energy ~ Eν Z and directional!

e e LZ Projected Electronic Recoil Backgrounds

LZ Projected Nuclear Recoil Backgrounds J. Dobson, UCLA DM 2018

J. Dobson, UCLA DM 2018 J. Dobson, UCLA DM’18

Jocelyn Monroe June 30, 2020 / p. 7 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

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

Goal: zeptobarn -> yoctobarn sensitivity to dark matter! https://lz.slac.stanford.edu/our-research/lz-research

Jocelyn Monroe June 30, 2020 / p. 9 2-Phase TPCs: Near(ish) Future

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.

5 cm x 5 cm tiled SiPM

Jocelyn Monroe 10 Jan. 23, 2019 Backgrounds N 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! Ajaj et al, Phys.Rev..D100 (2019)

Contamination: modified from Malling, UCLA DM’16 238U and 232Th decays, recoiling progeny and 2009 mis-identified alphas, betas mimic nuclear recoils

Neutrons: 2019 Nuclear recoil final state. (alpha,n), U, Th fission, DEAP, +PSD

cosmogenic spallation pp solar neutrinos μ μ γ N* N D. Malling, UCLA DM’16 n D. Malling, UCLA DM’16

Jocelyn Monroe June 30, 2020 / p. 11 Backgrounds N 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! Ajaj et al, Phys.Rev..D100 (2019)

Contamination: modified from Malling, UCLA DM’16 238U and 232Th decays, recoiling progeny and 2009 mis-identified alphas, betas mimic nuclear recoils

Neutrons: 2019 Nuclear recoil final state. (alpha,n), U, Th fission, DEAP, +PSD

cosmogenic spallation pp solar neutrinos μ μ γ N* N D. Malling, UCLA DM’16 n D. Malling, UCLA DM’16 Amaudruz et al, Phys.Rev.Lett. 121 (2018) no.7, 071801

Jocelyn Monroe June 30, 2020 / p. 11 Backgrounds N 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! Ajaj et al, Phys.Rev..D100 (2019)

Contamination: modified from Malling, UCLA DM’16 238U and 232Th decays, recoiling progeny and 2009 mis-identified alphas, betas mimic nuclear recoils

Neutrons: 2019 Nuclear recoil final state. (alpha,n), U, Th fission, DEAP, +PSD

cosmogenic spallation pp solar neutrinos μ μ γ N* N D. Malling, UCLA DM’16 n D. Malling, UCLA DM’16

Jocelyn Monroe June 30, 2020 / p. 11 Backgrounds N 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! Ajaj et al, Phys.Rev..D100 (2019)

Contamination: modified from Malling, UCLA DM’16 238U and 232Th decays, recoiling progeny and 2009 mis-identified alphas, betas mimic nuclear recoils

Neutrons: 2019 Nuclear recoil final state. (alpha,n), U, Th fission, DEAP, +PSD

cosmogenic spallation pp solar neutrinos μ μ γ N* N D. Malling, UCLA DM’16 n D. Malling, UCLA DM’16 + large, active veto detectors Jocelyn Monroe June 30, 2020 / p. 11 12 ) 10 -1 11 pp 10 7 What ν signals can bin Be -1 10 13 s 10 N -2 future dark matter detectors see? 109 15O 17 108 F 8B 107

Flux (cm hep ν 106 105 Solar 104 103 102

10-1 1 10 Neutrino Energy (MeV)

https://masterclass.icecube.wisc.edu/en/learn/detecting-neutrinos Jocelyn Monroe June 30, 2020 / p. 12 Prospects for Solar ν-N Coherent Scattering

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

DarkSide-20k ESPP 2019

Jocelyn Monroe June 30, 2020 / p. 13 12 ) 10 -1 Solar ν-e Event Rates 11 pp 10 7 ν bin Be ν -1 10 13 s 10 N example event rates -2 109 15O of -electron Z, W 17 108 F elastic scattering at LNGS, 8B 107 per tonne-year of CF4 Flux (cm hep e e ν 106 105 Solar 104 103 102

10-1 1 10 Neutrino Energy (MeV)

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)

Jocelyn Monroe June 30, 2020 / p. 14 Solar ν-e Event Rates Statistics even allow solar oscillation physics! ν ν example event rates of solar neutrino-electron Z, W elastic scattering at LNGS, per tonne-year of CF4 e e

Aalbers, et al. arXiv:2006.03114

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)

Jocelyn Monroe June 30, 2020 / p. 15 Solar ν-e Event Rates Statistics even allow solar oscillation physics! ν ν example event rates of solar neutrino-electron Z, W elastic scattering at LNGS, per tonne-year of CF4 e e

Aalbers, et al. arXiv:2006.03114

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)

Jocelyn Monroe June 30, 2020 / p. 15 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”. Franco et al., JCAP 1608 (2016) 08 Cerdeno, Davis, Fairbairn, Vincent, JCAP 1804 (2018) 37

big opportunities: 1) distinguish exclusion betweendetection high vs. low metallicity.

*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 C. Boehm et al., 2006.11250 Solar ν-Electron Scattering

Via neutrino-electron elastic scattering, LAr dark matter experiments can measure CNO (via spectral deformation), and CNO vs. Be-7 Xenon1T data +with O(500 t-y), study the “solar metallicity problem”. Franco et al., JCAP 1608 (2016) 08 Cerdeno, Davis, Fairbairn, Vincent, JCAP 1804 (2018) 37

big opportunities: 1) distinguish exclusion betweendetection high vs. low metallicity.

2) study non- standard solar neutrino interactions?

*Xe-136 background makes LXe CNO more challenging Aprile et al., 2006.09721 Baudis et al., JCAP 1401 (2014) 044, Baudis et al., 2006.03114 Boehm et al., 2006.11250

Jocelyn Monroe June 30, 2020 / p. 17 Lang et al., Phys. Rev. D 94 (2016) What neutrino signals can Arnaud et al., Phys.Rev.D.65.033010 future dark matter detectors see? (if lucky!)

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

https://masterclass.icecube.wisc.edu/en/learn/detecting-neutrinos Jocelyn Monroe May 3, 2018 / p. 7 Lang et al., Phys. Rev. D 94 (2016) What neutrino signals can Arnaud et al., Phys.Rev.D.65.033010 future dark matter detectors see? (if lucky!)

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

https://masterclass.icecube.wisc.edu/en/learn/detecting-neutrinos Jocelyn Monroe May 3, 2018 / p. 7 ) -1 105 s 238

What neutrino signals can -2 U 104 235U future dark matter detectors see? 3 10 232Th

Flux (cm 40 ν 102 K

Geo 10

1

10-1

10-2

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

https://masterclass.icecube.wisc.edu/en/learn/detecting-neutrinos Jocelyn Monroe June 30, 2020 / p. 19 in a 10n T-year exposure…

Contribution from geo-neutrinos is non- to ν-e scattering rate: ~few% low E dominated by the (not-yet- study with 500 neutrino background events measured) K-40 (Q = 1.3 MeV).

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

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

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

Jocelyn Monroe June 30, 2020 / p. 2 in a 10n T-year exposure…

Contribution from geo-neutrinos is non- to ν-e scattering rate: ~few% low E dominated by the (not-yet- study with 500 neutrino background events measured) K-40 (Q = 1.3 MeV).

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

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

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

Jocelyn Monroe June 30, 2020 / p. 2 What about Electron Directionality? potential increase in sensitivity / reduction in exposure to discovery from electron recoil direction

• 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…

exclusion detection Aalseth et al., JINST 12 (2017)

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

Jocelyn Monroe June 30, 2020 / p. 21 Geo ν-Electron Scattering Leyton, Dye, JM, Nature Commun. 8 (2017) 15989

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

study with 500 neutrino background events

example: geo-, solar-, reactor-ν -induced electron recoil directions, at LNGS. challenge: measure the direction of ~1 MeV e- recoils … potentially opens up measurement of crust vs. mantle flux Jocelyn Monroe June 30, 2020 / p. 22 What neutrino signals can future dark matter detectors see?

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

Albers et al., JCAP 1611 (2016)

Aprile et al., JCAP04 (2016) 027

https://masterclass.icecube.wisc.edu/en/learn/detecting-neutrinos Jocelyn Monroe May 3, 2018 / p. 7 ) -1

s ν

-2 µ What neutrino signals can 10-2 anti-νµ future dark matter detectors see? ν_e

Flux (cm -3 ν 10 anti-ν_e

10-4 Atmospheric

10-5

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

https://masterclass.icecube.wisc.edu/en/learn/detecting-neutrinos Jocelyn Monroe June 30, 2020 / p. 24 Prospects for Atmospheric ν-N Coherent Scattering A ν background paradigm…

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

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

Jocelyn Monroe June 30, 2020 / p. 25 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?

Jocelyn Monroe May 3, 2018 / p. 13 ν-less Double

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

P. Bras, IDPASC 2018

example: projected big opportunity: sensitivity significant Xe-136 in LZ: target mass (~600 kg)

big challenges: Q-value= exclusion detection 2458 keV Th background, energy resolution, and nuclear matrix element uncertainty

Jocelyn Monroe June 30, 2020 / p. 27 ν-less

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

P. Bras, IDPASC 2018 Thanks to L. Baudis example: Xenon1T energy big opportunity: resolution significant Xe-136 target mass (~600 kg) Q-value= 2458 keV big challenges: exclusion detection Th background, energy resolution, and nuclear matrix element uncertainty

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

Jocelyn Monroe June 30, 2020 / p. 28 2 Direct searches: limits on |Ue4| at 10 keV mass Sterile ν Signatures ~ 0.02 at 90% CL from beta decay measurements Dragoun, Venos, Phys. 3 (2016) 77-113 1) -electron scattering: - - NS e νe e Campos & Rodejohann, Phys.Rev.D 94 (2016)

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

Jocelyn Monroe June 30, 2020 / p. 29 2 Astrophysical limits on |Ue4| at 10 keV mass ~1E=11 2 Astrophysical searches: limits on |Ue4| at 10 keV Sterile ν Signatures are ~1E-11 from x-ray constraints Dragoun, Venos, Phys. 3 (2016) 77-113 1) Sterile neutrino-electron scattering: - - NS e νe e Campos & Rodejohann, Phys.Rev.D 94 (2016)

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

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

Jocelyn Monroe Weinheimer, ESPPU’19 June 30, 2020 / p. 26 2 Astrophysical limits on |Ue4| at 10 keV mass ~1E=11 Conclusions & Outlook

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.

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)

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