CEvNS Detection with Ricochet
Joe Johnston
MIT
October 11, 2018
Joe Johnston (MIT) Ricochet AAP 2018 October 11, 2018 1 / 23
Outline
1 RicochetSuperconducting BolometersTemperature ReadoutExperimental SiteCurrent Status
2 BSM Searches at ReactorsNeutrino Magnetic MomentNSI CouplingsMassive Mediators
3 Summary
Joe Johnston (MIT) Ricochet AAP 2018 October 11, 2018 2 / 23
Ricochet Introduction
Ricochet
Coherent Elastic Neutrino Nucleus Scattering (CEvNS)
≈ N2 scaling gives large cross section
Requires low energy recoil detection (hundreds of eV)
Ricochet will achieve this via:
Zn (superconducting) and Ge bolometers
Phase 1: 100 eV threshold, 1 kg
Phase 2: 10 eV threshold, 10 kg
Joe Johnston (MIT) Ricochet AAP 2018 October 11, 2018 3 / 23
Ricochet Superconducting Bolometers
Bolometric Detectors
Heat capacity dominated by lattice contributions at ultra-lowtemperatures
Figure from J Formaggio
Used in direct detection of dark matterJoe Johnston (MIT) Ricochet AAP 2018 October 11, 2018 4 / 23
Ricochet Superconducting Bolometers
Superconducting BolometersEnergy deposited via quasiparticles or phononsEM events will create more quasiparticlesQuasiparticles have long recombination times
Simulation of three years of Ricochet dataFigure from J Billard
Joe Johnston (MIT) Ricochet AAP 2018 October 11, 2018 5 / 23
Ricochet Temperature Readout
Multiplexing TES Readouts
Thermalize a transition edge sensor (TES) to each detector
RF SQUID inductance depends on external flux
Each detector readout is tuned to a specific frequency
GHz input allows scanning over frequencies
Slide from J Formaggio
Joe Johnston (MIT) Ricochet AAP 2018 October 11, 2018 6 / 23
Ricochet Experimental Site
Ricochet will likely be at the Chooz Reactor Complex
Two cores
8.5 GW power combined
Both cores on 60% of the time, one core 40%
Near Site (NS): 400 m from cores, 120 m.w.e
Very Near Site (VNS): 80 m from cores, ≈ 10 m.w.e expected
Joe Johnston (MIT) Ricochet AAP 2018 October 11, 2018 7 / 23
Ricochet Experimental Site
Near Site Backgrounds
Recoil energy [keV]3−10 2−10 1−10 1 10 210
Eve
nt r
ate
[evt
s/kg
/keV
/day
]
2−10
1−10
1
10
210CEvNS
-eνComptonTritiumPb-206BetasNeutrons
Neutron rate from simulationInternal backgrounds from EDELWEISS
1.5 evts/kg/day background, 0.5 evts/kg/day signal (0.1-1 keV ROI)Joe Johnston (MIT) Ricochet AAP 2018 October 11, 2018 8 / 23
Ricochet Current Status
Currently have several Zncrystals
Initial calibration pulses takenat IPNL Lyon
Future crystals will be cubesfor easier polishing
Joe Johnston (MIT) Ricochet AAP 2018 October 11, 2018 9 / 23
BSM Searches at Reactors
1 RicochetSuperconducting BolometersTemperature ReadoutExperimental SiteCurrent Status
2 BSM Searches at ReactorsNeutrino Magnetic MomentNSI CouplingsMassive Mediators
3 Summary
(J. Billard, J. Johnston, B. Kavanagh. arxiv:1805.01798 [hep-ph].Under review by JCAP.)
Joe Johnston (MIT) Ricochet AAP 2018 October 11, 2018 10 / 23
BSM Searches at Reactors Assumptions
Reactor detection probes lower energy neutrinos (3 vs 30 MeV)
Assumptions:
Isotopes Si, Ge, Zn, CaWO4, and Al2O3 (Sapphire).
Phase 1 Phase 2Target Eth [eV] Mass [g] Eth [eV] Mass [g]
Zn 50 500 10 5000Ge 50 500 10 5000Si 50 500 10 5000CaWO4 20 6.84 7 68.4Al2O3 20 4.41 4 44.1
Backgrounds:
Compton: 10−3 discrimination power
Neutrons: 0.1 discrimination power in CaWO4 and Al2O3
Joe Johnston (MIT) Ricochet AAP 2018 October 11, 2018 11 / 23
BSM Searches at Reactors Neutrino Magnetic Moment
Neutrino Magnetic Moment
Minimal SM extensions allow up to µν ≈ 10−15µB
A Majorana Neutrino could allow µν ≈ 10−12µB or higher
dσCoherentν−N
dER=
dσSM CEvNSν−N
dER+
dσmag.ν−N
dER
dσmag.ν−N
dER=πα2µ2
νZ2
m2e
(1
ER− 1
Eν+
ER
4E 2ν
)F 2(ER)
10-3 10-2 10-1 100 101
Recoil energy, ER [keV]
10-2
10-1
100
101
102
103
dRνN/dER [
eve
nts
/kg
/keV
/day] Phase 2 Phase 1
CEνNS on a CaWO4 target (Near Site)
BG after rejectionStandard Model CEνNS
µν = 2. 2× 10−12 µB
µν = 2. 9× 10−11 µB
µν = 3. 0× 10−10 µB
Joe Johnston (MIT) Ricochet AAP 2018 October 11, 2018 12 / 23
BSM Searches at Reactors Neutrino Magnetic Moment
Competitive with terrestrial bounds around several years
Joe Johnston (MIT) Ricochet AAP 2018 October 11, 2018 13 / 23
BSM Searches at Reactors NSI Couplings
Focus on vector couplings to quarks, εqVee = εqLee + εqRee , q = u, d :
Q2W → Q2
NSI = 4[N
(−1
2+ εuVee + 2εdVee
)+ Z
(1
2− 2 sin2 θW + 2εuVee + εdVee
)]2
+ 4[N(εuVeτ + 2εdVeτ ) + Z (2εuVeτ + εdVeτ )
]2
u, d, e
νe, νµ, ντ
u, d, e
νe, νµ, ντ
εuVeµ constrained by µ→ e conversionin nuclei
εuVαβ/εdVαβ degeneracy broken bycombining different N/Z ratios
Breaking εuVαβ / εdVαβ degeneracy isimportant for DUNE(P. Coloma and T. Schwetz, Phys. Rev. D 95, 079903 (2017))
Joe Johnston (MIT) Ricochet AAP 2018 October 11, 2018 14 / 23
BSM Searches at Reactors NSI Couplings
Focus on vector couplings to quarks, εqVee = εqLee + εqRee , q = u, d :
Q2W → Q2
NSI = 4[N
(−1
2+ εuVee + 2εdVee
)+ Z
(1
2− 2 sin2 θW + 2εuVee + εdVee
)]2
+4[N(εuVeτ + 2εdVeτ ) + Z (2εuVeτ + εdVeτ )
]2
u, d, e
νe, νµ, ντ
u, d, e
νe, νµ, ντ
εuVeµ constrained by µ→ e conversionin nuclei
εuVαβ/εdVαβ degeneracy broken bycombining different N/Z ratios
Breaking εuVαβ / εdVαβ degeneracy isimportant for DUNE(P. Coloma and T. Schwetz, Phys. Rev. D 95, 079903 (2017))
Joe Johnston (MIT) Ricochet AAP 2018 October 11, 2018 14 / 23
BSM Searches at Reactors NSI Couplings
Flavor Conserving Ge+Si:
1.0 0.5 0.0 0.5 1.0
εdVee
1.0
0.5
0.0
0.5
1.0
εuVee
CHARM
LHC monojet
COH
ERENT
95% CL allowed regions - Very Near Site - Phase 1
Ge
Si
Ge + Si
N/Z values: Ge=1.27, Zn=1.18, Si=1.01, Al=1.08, O=1.00, W=1.48Joe Johnston (MIT) Ricochet AAP 2018 October 11, 2018 15 / 23
BSM Searches at Reactors NSI Couplings
Flavor Conserving All:
1.0 0.5 0.0 0.5 1.0
εdVee
1.0
0.5
0.0
0.5
1.0
εuVee
CHARM
LHC monojet
COH
ERENT
95% CL allowed regions - Very Near Site - Phase 1
Ge
Zn
SiCaWO4
Al2O3
All
A multi-target experiment can place very strong boundsJoe Johnston (MIT) Ricochet AAP 2018 October 11, 2018 16 / 23
BSM Searches at Reactors NSI Couplings
Focus on vector couplings to quarks, εqVee = εqLee + εqRee , q = u, d :
Q2W → Q2
NSI = 4[N
(−1
2+εuVee + 2εdVee
)+ Z
(1
2− 2 sin2 θW +2εuVee + εdVee
)]2
+ 4[N(εuVeτ + 2εdVeτ ) + Z (2εuVeτ + εdVeτ )
]2
u, d, e
νe, νµ, ντ
u, d, e
νe, νµ, ντ
εuVeµ constrained by µ→ e conversionin nuclei
εuVαβ/εdVαβ degeneracy broken bycombining different N/Z ratios
Breaking εuVαβ / εdVαβ degeneracy isimportant for DUNE(P. Coloma and T. Schwetz, Phys. Rev. D 95, 079903 (2017))
Joe Johnston (MIT) Ricochet AAP 2018 October 11, 2018 17 / 23
BSM Searches at Reactors NSI Couplings
Flavor Changing Constraints:
1.0 0.5 0.0 0.5 1.0
εdVeτ
1.0
0.5
0.0
0.5
1.0
εuVeτ
CHARM
LHC monojet
COH
ERENT
95% CL allowed regions - Very Near Site - Phase 1
Ge
Si
Ge + Si
1.0 0.5 0.0 0.5 1.0
εdVeτ
1.0
0.5
0.0
0.5
1.0
εuVeτ
CHARM
LHC monojet
COH
ERENT
95% CL allowed regions - Very Near Site - Phase 1
Ge
Zn
SiCaWO4
Al2O3
All
Joe Johnston (MIT) Ricochet AAP 2018 October 11, 2018 18 / 23
BSM Searches at Reactors Massive Mediators
A massive scalar mediator adds a term to SM CEvNS
dσφdER
=(gν)2Q2
φ
4π
ERm2N
E 2ν (q2 + m2
φ)2F 2(ER)
Qφ ≈ (15.1Z + 14N)gq
10-3 10-2 10-1 100 101
Recoil energy, ER [keV]
10-2
10-1
100
101
102
103
dRνN/dER [
eve
nts
/kg
/keV
/day] Phase 2 Phase 1
CEνNS on a CaWO4 target (Near Site)
BG after rejectionStandard Model CEνNS
mφ = 1 keV; gφ = 10−6
mφ = 1 MeV; gφ = 10−6
mφ = 100 GeV; gφ = 5× 10−2
Joe Johnston (MIT) Ricochet AAP 2018 October 11, 2018 19 / 23
BSM Searches at Reactors Massive Mediators
Lower mediator masses are better probed at low neutrino energiesJoe Johnston (MIT) Ricochet AAP 2018 October 11, 2018 20 / 23
BSM Searches at Reactors Massive Mediators
A vector mediator interferes with SM CEvNS
QW → QSM+NP = QW −√
2
GF
QZ ′
q2 + m2Z ′
10-3 10-2 10-1 100 101
Recoil energy, ER [keV]
10-2
10-1
100
101
102
103
dRνN/dER [
eve
nts
/kg
/keV
/day] Phase 2 Phase 1
CEνNS on a CaWO4 target (Near Site)
BG after rejectionStandard Model CEνNS
+ mZ ′ = 10 keV; gZ ′ = 4× 10−6
+ mZ ′ = 1 MeV; gZ ′ = 10−5
+ mZ ′ = 100 GeV; gZ ′ = 10−1
10-2 10-1 100 101 102 103 104
mZ ′ [MeV]
10-7
10-6
10-5
10-4
10-3
10-2
10-1
100
Med
ian
90%
Up
per
Lim
it o
n gZ′
COHERENT (2017)
Z ′−model, gν = gu = gd ≡ gZ ′Ge (DC, Phase 1)
Zn
SiCaWO4
Al2O3
All
Joe Johnston (MIT) Ricochet AAP 2018 October 11, 2018 21 / 23
Summary
1 RicochetSuperconducting BolometersTemperature ReadoutExperimental SiteCurrent Status
2 BSM Searches at ReactorsNeutrino Magnetic MomentNSI CouplingsMassive Mediators
3 Summary
Joe Johnston (MIT) Ricochet AAP 2018 October 11, 2018 22 / 23
Summary
Ricochet:
Superconducting Zn bolometers for background rejection
Multiplexing TES readout will allow necessary scaling
Experimental site at Chooz reactor complex
Zn crystals fabricated and in testing
Proposed experiments will be able to place bounds on new physics:
Probe nuetrino magnetic moment
Multiple targets tightly contrain NSI
Low energy neutrinos better constrain simple mediator models
Joe Johnston (MIT) Ricochet AAP 2018 October 11, 2018 23 / 23
Backup Slides
Backup Slides
Joe Johnston (MIT) Ricochet AAP 2018 October 11, 2018 24 / 23
Backup Slides
ν-cleus
Strauss et al. arXiv:1704.04320v2 [physics.ins-det] 9 Aug 2017. (Labels added)
Joe Johnston (MIT) Ricochet AAP 2018 October 11, 2018 25 / 23
Backup Slides
ν-cleus
Initially 11 g, 110 g at a later phase
Threshold O(≤10 eV)
Strauss et al. arXiv:1704.04320v2 [physics.ins-det] 9 Aug 2017
Joe Johnston (MIT) Ricochet AAP 2018 October 11, 2018 26 / 23
Backup Slides
Background Assumptions
Compton Background:
100 events/kg/day in Ge
Factor 10−3 discrimination power
Neutron Background:
10 times larger at VNS
Factor of 0.1 discrimination power for CaWO4 and Al2O3
No reactor correlation
All other backgrounds negligible
Joe Johnston (MIT) Ricochet AAP 2018 October 11, 2018 27 / 23
Backup Slides
Recoil energy [keV]3−10 2−10 1−10 1 10
Eve
nt r
ate
[evt
s/kg
/keV
/day
]
2−10
1−10
1
10
210
310
GammasLeadBetasNeutronsTotal background (before rejection)Total background (after rejection)CENNS (NS: 8.5 GW, 400 m)CENNS (VNS: 8.5 GW, 80 m)
10% background normalization uncertainty
5% CEvNS normalizations uncertainty
Joe Johnston (MIT) Ricochet AAP 2018 October 11, 2018 28 / 23
Backup Slides
Likelihood:
L(D|θ,ψ) = L(ψ)×Nbins∏
i
P(N
(i)obs
∣∣∣ N (i)sig(θ) + N
(i)bg (ψ)
).
θ is our parameter of interest
γ is nuisance parameters, for example constraining thebackgrounds.
A 10% uncertainty is assumed on all background normalizations
A 5% uncertainty is assumed on the CEvNS signal
Use profile likelihood ratio test to determine most bounds
An asimov data set is used to determine bounds on NSI(G. Cowan, K. Cranmer, E. Gross and O. Vitells, Asymptotic formulae for likelihood-based tests of new physics, Eur.
Phys. J. C71 (2011) 1554,[1007.1727]
Joe Johnston (MIT) Ricochet AAP 2018 October 11, 2018 29 / 23
Backup Slides
Introduce a 4-fermion coupling (α,β=e,µ,τ , f =e,u,d , P = L,R)
LNSI = −εfPαβ2√
2GF (ναγρLνβ)(f γρPf )
u, d, e
νe, νµ, ντ
u, d, e
νe, νµ, ντ
Joe Johnston (MIT) Ricochet AAP 2018 October 11, 2018 30 / 23
Backup Slides
sin2(θW ) and APV constraints
It is very difficult to place bounds on new physics withoutassuming some constraint on sin2(θW )We fix sin2(θW ), but multiply all CEvNS signals by a 5%envelope to account for all systematic uncertainties
Joe Johnston (MIT) Ricochet AAP 2018 October 11, 2018 31 / 23
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