Neutrino Physics with Future Dark Matter Detectors
Jocelyn Monroe, Royal Holloway, University of London
XVIII International Workshop on Neutrino Telescopes Venice, IT March 21, 2019 Dark Matter Direct Detection
Signal:χN ➙χN χ χ
Backgrounds: γ e- ➙ γ e- n N ➙ n N N ➙ N’ + α, e- ν N ➙ ν N
experimental requirements: particle ID for recoil N, e-, alpha, n (multiple)γ final states γ Jocelyn Monroe March 21, 2019 / p. 2 Dark Matter Direct Neutrino Detection
Signal: ν N ➙ ν N or ν e- ➙ ν e- ν ν
Backgrounds: γ e- ➙ γ e- n N ➙ n N N ➙ N’ + α, e- χN ➙ χN?
very similar requirements! ν (and ideally also measure direction) ν Jocelyn Monroe March 21, 2019 / p. 3 Neutrino Backgrounds to Dark Matter Searches and Directionality
Jocelyn Monroe, MIT
Jocelyn Monroe May 30, 2008 ν Cross Sections: ν-N Coherent Scattering Cross sections are coherently 2 2 -44 2 enhanced, ~ A x (Eν/MeV) x 10 cm recoils are O(10 KeV) D. Z. Freedman, Phys. Rev. D9. 1389 (1974) ν ν
Z 2 Φ(solar B8 ν) = 2En Tmax = 5.86 x 106 cm-2 s-1 mnucleus + 2En N N
Aprile et al., JCAP04 (2016) 027
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)
Jocelyn Monroe May 30, 2008 What ν physics can future dark matter detectors do?
https://masterclass.icecube.wisc.edu/en/learn/detecting-neutrinos Jocelyn Monroe March 21, 2019 / p. 6 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 March 21, 2019 / p. 7 2-Phase TPCs: Near(ish) Future
XENON-nT: 6 t LXe (active), following XENON-1T (LNGS), from 2019. PandaX-4: 4 t LXe (active), following PandaX (JinPing), from 2019. LZ: 7 t LXe (active), following LUX (SURF), from 2020.
DarkSide-20k: 50 t LAr (LNGS), ArDM+DEAP+DS50+MiniCLEAN, from 2022.
DARWIN: 50 t LXe (LNGS), following XENON-nT. ARGO: 500 t LAr (SNOLAB?), following DarkSide-20k.
5 cm x 5 cm tiled SiPM
Jocelyn Monroe 8 Jan. 23, 2019 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
Contamination: 238U and 232Th decays, recoiling progeny and mis-identified alphas, betas mimic nuclear recoils
Neutrons: Nuclear recoil final state. (alpha,n), U, Th fission, cosmogenic spallation μ μ γ N* N n D. Malling, UCLA DM’16 + discrimination between e- vs. N
Jocelyn Monroe March 21, 2019 / p. 9 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
Contamination: 238U and 232Th decays, recoiling progeny and mis-identified alphas, betas mimic nuclear recoils
Neutrons: Nuclear recoil final state. (alpha,n), U, Th fission, cosmogenic spallation μ μ γ N* N n D. Malling, UCLA DM’16 - Amaudruz, JM et al, Phys.Rev.Lett. 121 (2018) no.7, 071801 + discrimination between e vs. N
Jocelyn Monroe March 21, 2019 / p. 10 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
Contamination: 238U and 232Th decays, recoiling progeny and D.-M. Mei, A. Hime, PRD73:053004 (2006) mis-identified alphas, betas mimic nuclear recoils
Neutrons: Nuclear recoil final state. (alpha,n), U, Th fission, cosmogenic spallation μ μ γ N* N n + discrimination between e- vs. N
Jocelyn Monroe + large, active neutron shielding March 21, 2019 / p. 11 What ν physics can future dark matter detectors do?
https://masterclass.icecube.wisc.edu/en/learn/detecting-neutrinos Jocelyn Monroe March 21, 2019 / p. 12 12 ) 10 -1 11 pp 10 7 What ν physics can bin Be -1 10 13 s 10 N -2 future dark matter detectors do? 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 March 21, 2019 / p. 13 Prospects for Solar ν-N Coherent Scattering
−37 10 CRESST-III 2017 10−38 CDMSLite 2017 ] 2 10−39 10−40 [cm
SI −41 DarkSide-50 2018 σ 10 ATLAS 2018 (Vector Z', 95% CL) 10−42 DEAP-3600 2017 −43 10 SuperCDMS Ge HV proj. LUX 2017 −44 10 PANDAX-II 2017 DarkSide-LM proj. DarkSide-50 2018 DEAP-3600 proj. −45 10 XENON1T 2018 LZ proj.
−46 proj. 10 XENONnT proj. t yr yr proj. −47 DARWIN 200t 10 yr proj. r 3k t ecto det −48 ARGO 10 nne Dark Matter-Nucleon DarkSide-20k o200 00-t re 3 −49 Futu 10 Neutrino floor on xenon 10−50 −3 −2 −1 2 10 10 10 2 1 10 10 DarkSide-20k ESPP 2019 Mχ [TeV/c ]
Jocelyn Monroe March 21, 2019 / p. 14 Solar ν-N Coherent Scattering (= Neutrino Bound)
• sensitivity scales with sqrt(time) instead of linearly in time (with zero background) • background systematics become crucial PDFs in (energy, angle, time) of event for coherent solar neutrino background vs. background + dark matter signal are different! (includes angular resolution)
Grothaus, Fairbairn, JM, Phys.ReV.D90 (2014) 055018
• annual modulation still contains information to differentiate dark matter vs. neutrinos
• directionality gains 10x in sensitivity 6 GeV 30 GeV in the presence of backgrounds 1000 GeV solid = with direction no neutrino bound for directional detectors dotted = without direction • dashed = neutrino bound from simulation with Phys.Rev. D89, 023524 (2014)
Jocelyn Monroe May 3, 2018 / p. 22 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 solar neutrino-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 March 21, 2019 / p. 15 Solar ν-Electron Scattering
Via neutrino-electron elastic scattering, LAr dark matter experiments can observe the unmeasured CNO solar neutrino flux! (via spectral deformation) +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 opportunity: distinguish exclusion betweendetection high vs. low metallicity.
big challenges: Rn background suppression and uncertainty on cosmogenics *Xe-136 background makes LXe CNO challenging Baudis et al., JCAP 1401 (2014) 044,
Jocelyn Monroe March 21, 2019 / p. 16 (P. Agnes, JM in preparation) What about Electron Directionality? potential increase in sensitivity / reduction in exposure to discovery from electron recoil direction
• 1 mm sampling pitch in drift direction makes direction reconstruction of ~cm length electron tracks feasible in 1D • directional dark matter detection studies show 1D direction reconstruction gains 10x over non-directional measurements in the presence of backgrounds Mayet, JM et al., Phys.Rept. 627 (2016)
0.45 zenith θ 0.4 1.75 MeV ) /
zenith 0.35 1.5 MeV θ 0.3 1.0 MeV (cos σ 0.25
0.2
0.15
0.1 exclusion detection
0.05
0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 θzenith (radians)
Jocelyn Monroe March 21, 2019 / p. 17 What neutrino physics can (if lucky!) future dark matter detectors do? for a supernova at 10 kPc, expect 300-500 ν-N events in DarkSide-20k, XENON-nT, LZ, up to few k in DARWIN. Lang et al., Phys. Rev. D 94 (2016) • measure all flavors via NC 40 - 40 • measure νe Ar e K* • multi-messenger observation: sub-eV mass ordering? Arnaud et al., Phys.Rev.D.65.033010
https://masterclass.icecube.wisc.edu/en/learn/detecting-neutrinos Jocelyn Monroe May 3, 2018 / p. 7 ) -1 105 s 238
What neutrino physics can -2 U 104 235U future dark matter detectors do? 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 March 21, 2019 / p. 18 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 March 21, 2019 / p. 2 Geo ν-Electron Scattering
PLR analysis of energy, time, and direction shows sensitivity at 95% CL to measure K-40 geo-neutrino 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…. Leyton, Dye, JM, Nature Commun. 8 (2017) 15989 Jocelyn Monroe March 21, 2019 / p. 20 What neutrino physics can future dark matter detectors do?
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 physics can 10-2 anti-νµ future dark matter detectors do? 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 March 21, 2019 / p. 23 Prospects for Atmospheric ν-N Coherent Scattering
A ν background paradigm…
DarkSide-20k ESPP 2019 10−44 LZ (5σ Discovery, 15 t×yr) DarkSide-20k (5σ Discovery, 200 t×yr) ARGO (5σ Discovery, 3000 t×yr) 10−45
] −46 2 10 [cm -n χ −47 σ 10
10−48
10−49 −2 −1 2 10 10 1 2 10 10 Mχ [TeV/c ] where the ‘neutrino floor’ depends on electron discrimination power
Jocelyn Monroe March 21, 2019 / p. 24 What can future dark matter detectors tell us about the neutrino?
Jocelyn Monroe May 3, 2018 / p. 13 ν-less Double Beta Decay
The liquid Xenon dark matter searches aim for competitive sensitivity to neutrinoless double beta decay, via restricted fiducial volume (inner 1 t) to reduce backgrounds, and projected 1% energy resolution at the 2ν beta decay endpoint in Xe.
P. Bras, IDPASC 2018 example: projected sensitivity big opportunity: in LZ: significant Xe-136 target mass (~600 kg) Q-value= exclusion big challenges:detection 2458 keV Th background suppression, achieving target energy resolution, and nuclear matrix element uncertainty
Jocelyn Monroe March 21, 2019 / p. 26 2 Upper limit on |Ue4| at 10 keV mass ~ 0.02 Sterile ν Signatures at 90% CL from beta decay.
The beta decay energy spectrum is modified Dragoun, Venos, Phys. 3 (2016) 77-113 by neutrino mass and mixing.
2 big opportunity: 10 KeV sterile mass, mixing |Ue4| = 0.02 high Q-value beta decays of backgrounds big challenges: (e.g. Ar-39) with nuclear physics good energy resolution uncertainties on have sensitivity to beta spectrum shape, “shape - 1” = 10-100 keV sterile νs [ fit (w/o, w/ sterile) / understanding energy fit to null hypothesis] - 1 resolution at % level
Jocelyn Monroe March 21, 2019 / p. 27 Conclusions & Outlook
Dark matter direct detection technology is approaching the scale where neutrino physics is within reach. Coherent scattering of solar neutrinos, and CNO neutrinos are the prize, with large exposures. 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! extra Directional Detection
R&D towards recoil direction measurement to correlate a signal with the galactic halo
DMTPC n calibration data, DMTPCMC fit templaten calibration data, 50 keVr charge data, nuclear recoil150 keVr
anode grid
Voltage Many R&D efforts: DRIFT, DMTPC, MIMAC, NEWS, RED etc.
largest are 1m3 (O(100g) target).
Majority use CF4 gas; NEWS uses emulsions. time (s) CYGNUS: global coordination towards a physics-scale directional experiment. Physics Reports 2016, arXiv:1602.03781 DMTPC
huge experimental challenge to measure direction of recoil tracks of O(10 keV): Jocelyn Monroe March 21, 2019 / p. 30 Directional Detection R&D towards recoil direction measurement to correlate a signal with the galactic halo DMTPC n calibration data, DMTPCMC fit templaten calibration data, 50 keVr charge data, nuclear recoil150 keVr anode grid Voltage detectors achieve angular resolution of ~35o at 50 keVr time (s) with current best direction reconstruction, need 200-400 events to measure anisotropy at 3σ significance Phys.Rev.D95 (2017) 122002 Jocelyn Monroe March 21, 2019 / p. 31