with B. Dutta, D. Kim, S. Liao, S. Shin, L. Strigari & A ...Jong-Chul Park 2020.06.09 4th TAU...
Transcript of with B. Dutta, D. Kim, S. Liao, S. Shin, L. Strigari & A ...Jong-Chul Park 2020.06.09 4th TAU...
Jong-Chul Park
4th TAU Meeting2020.06.09
with B. Dutta, D. Kim, S. Liao, S. Shin, L. Strigari & A. Thompson [PRL (2020) & 2006.XXXXX]
DM SM
SMDM
Interaction
Correct thermal relic abundance:
Ωℎ2~0.1 𝑝𝑏
𝜎𝑣with 𝜎𝑣 ~
𝛼𝑋2𝑚𝜒
2
𝑀4 (M: dark scale/mediator)
Weak coupling naturally weak scale mass:
~1 GeV – 10 TeV mass range favored
weak scale (new) physics
* Axion: another classic solution by CAPP.
annihilation
Freeze-out
Relic abundance
MACHO /Primordial
BHsnon-particle
10-22 eV keV MeV GeV TeV PeV
Superheavy/ Composite
WIMPzillaQ-ball
Dark-quark nugget
non-thermal
WIMPwell-
motivatedextensively
studiedthermal
Lightparticle
DMcan be
thermal
SuperlightWDM
Sterile νmay be thermal
Ultralight Scalar field
(QCD) AxionHidden photon
non-thermal
100𝑀⨀~1068 eV
10-22 eV keV MeV GeV TeV PeV
Lightparticle
DM
For heavy mediator, 𝜎𝑣 ~𝛼𝑋2𝑚𝜒
2
𝑀4
For weak scale physics,
sub-GeV DM overproduction
New mediator < 𝑀𝑊 for freeze-out
or freeze-in, …
100𝑀⨀~1068 eV
New DM relic determination mechanisms:
Assisted Freeze-Out [arXiv:1112.4491]
Cannibal DM [arXiv:1602.04219, 1607.03108]
Co-Decaying [arXiv:1105.1652, 1607.03110]
Semi-Annihilation [arXiv:0811.0172, 1003.5912]
SIMP [arXiv:1402.5143]
… Various light DM/mediator scenarios:
MeV DM for GC 511 keV line observation [astro-ph/0309686]
Secluded MeV DM [arXiv:0711.3528, 0711.4866]
Sommerfeld enhancement for 𝑒+ excess [arXiv:0810.0713]
(𝑔 − 2)𝑒, 𝜇: ~2 − 3𝜎 discrepancy [arXiv:1806.10252]
New ν interactions for the MiniBooNE excess [arXiv:1807.09877]
Solutions of Yukawa coupling hierarchy prob. [arXiv:1905.02692]
…
10-22 eV keV MeV GeV TeV PeV
Lightparticle
DM
𝐸𝑘~𝑚𝑣2< 𝑶(keV) with 𝑣~10−3:
< 𝐸𝑟𝑡ℎ of typical DM direct detectors
for nuclear recoils
100𝑀⨀~1068 eV
Cosmogenic energetic DM searches: COSINE-
100, DUNE/ProtoDUNE, IceCube, SK/HK/KNO, …
GC, Sun, …
Large Vol. detector
New ideas for low 𝐸𝑟𝑡ℎ are required!
Ionization by e-recoils (semiconductor)
[arXiv:1108.5383, 1509.01598]
Ejection of e’s (graphene, C-nanotube)
[arXiv:1606.08849, 1706.02487, 1808.01892]
Evaporation of He by nuclear-recoils
[arXiv:1706.00117]
Gaphene-Josephson-junction (sub-keV~MeV)
D. Kim, JCP, KC Fong, GH Lee [arXiv:2002.07821]
…
Seodong’s Talk
Active searchesPassive searches
Cloud chamber:
𝑒+, 𝜇±, …
Collider: controlled environment
Conventional colliders
Head-on collision of light
SM-sector (stable) particles
to produce heavier SM states
and study resulting pheno.
~5% visible sector
Direct detection: (hopefully) DM?
DM “Production” (e.g. fixed target exp.): controlled environment
Dark matter productions
Dump of SM-sector (stable)
particles onto a target
to produce dark-sector states
and study resulting pheno.
~25% dark sector
A new strategy to search for DM signals in ν experiments:
we can efficiently isolate DM signals from the SM ν BGs
using timing & energy spectra at (certain kinds of) neutrino experiments
with low-E & pulsed-beam, “CEνNS”.
Application: the measured CsI data of the COHERENT experiment
Result: mild (𝟐. 𝟒 − 𝟑𝝈) excess beyond known backgrounds!
The excess can be explained by light DM arising from dark gauge boson decay.
Various current/future Coherent Elastic ν-Nucleus Scattering (CEνNS) experiments
Beam-induced ν: CCM, COHERENT, (JSNS2), …
Reactor ν: CONNIE, CONUS, MINER, NEON, Nu-Cleus, ν GEN, RED-100, Ricochet,
TEXONO, …
(JSNS2)NEON
Low E, High luminosity, Pulsed beam
Hyun Su’s Talk
Main goal: direct measurement of coherent
elastic ν-nucleus scattering (CEνNS)
dominant interaction for 𝐸𝜈 ≲ 50 MeV
COHERENT @ Oak Ridge: 1 GeV p beam on Hg target,
600 ns wide pulses & 60 Hz, ~8.8 × 1015 POT/s
(JSNS2) @ J-PARC: 3 GeV p beam on Hg target, 2 × 100 ns
pulses separated by 440 ns & 25 Hz, ~2.1 × 1015 POT/s
CCM @ LANL: 0.8 GeV p beam on W target, 290 ns wide
pulses & 20 Hz, ~5.6 × 1014 POT/s
Gd-LS17 ton
2.6 MeV
COHERENT
JSNS2
𝝁 decay:delayed ν’s
𝝅 decay:prompt ν’s
COHERENT [1803.09183] & JSNS2 [1705.08629]
14.6 kg6.5 keV
24 kg20 keV
185 kg13 keV
10 kg5 keV
Low E, High luminosity, Pulsed beam
Prompt ν’s: 𝑇 < ~1 𝜇s & 𝐸𝜈 = 29.8 MeV
Delayed ν’s: mostly 𝑇 > ~1 𝜇s &
𝐸𝜈 = 0 − 53 MeV
𝜋 decay
𝜇 decay
COHERENT [arXiv:1803.09183 & 1804.09459]
𝝁 decay:delayed ν’s
𝝅 decay:prompt ν’s
𝐸𝜈 = 30 MeV & CsI: 𝐸𝑟,𝑁𝑚𝑎𝑥~15 keV
Low 𝐸𝑡ℎ required, e.g. DM direct detectors!
Meson decays (P1): 𝜋0(𝜂) → 𝛾 + 𝛾/𝑿
𝜋− absorption (capture) process (P2): 𝜋− + 𝑝 → 𝑛 + 𝛾/𝑿 (X: single-valued E)
Charge exchange processes (P3): 𝜋−(+) + 𝑝 𝑛 → 𝑛 𝑝 + 𝜋0 & 𝜋0 → 𝛾 + 𝛾/𝑿
𝑒±-induced cascade (P4): electromagnetic cascade showering & 𝛾 → 𝑿
𝑿
𝜒
𝜒
Proton beam
Target
𝜋0, stopped 𝜋±
𝑝/𝑛 in target
Detector
𝑿𝑓
ҧ𝑓
𝜿𝒇𝑿𝒙𝒇
𝑿𝑿
𝜒
𝜒𝜿𝑫𝑿
GEANT4 (p dump ~ γproduction) + our own code
Nucleus scattering (D1): (small 𝐸𝑟)
Electron scattering (D2): (large 𝐸𝑟)
𝑿
𝜒
𝜒
Proton beam
Target
𝜋0, stopped 𝜋±
𝑝/𝑛 in target
𝜒𝜒
𝑁/𝑒
Detector
𝑁/𝑒𝜒 𝜒
𝑓 𝑓𝜿𝒇𝑽𝒙𝒇
𝑽
𝜿𝑫𝑽
𝐴′
Key specification of benchmark experiments (Low E, High luminosity, Pulsed
beam) & detectors under consideration
The protons-on-target (POT) values are expected spills for 5000-hours operation per year
The mass of the LAr detector in parentheses in COHERENT is for a future upgrade.
COHERENT: 1 GeV p beam, 600 ns wide pulses & 60 Hz
JSNS2: 3 GeV p beam, 2 × 100 ns pulses separated by 440 ns & 25 Hz
CCM: 0.8 GeV p beam, 290 ns wide pulses & 20 Hz
Possible models relevant to the benchmark experiments
Respective coupling constants & gauge charges
Production & detection channels
Various possibilities for a dark 𝐴′
Relativistic (solid) vs. Non-relativistic
(dotted)
Short-lived vs. Long-lived
𝑚χ = 5 MeV
Relativistic: Prompt t-bins,
DM flux maximized for 𝜏 < a few × 10 ns
Non-relativistic: Only for 𝑚𝐴′ ≈ 138 MeV (≈
𝑚𝜋− +𝑚𝑝 −𝑚𝑛), Mostly Prompt t-bins (𝜏 ≲ 0.1𝜇𝑠)
DM flux maximized for 𝜏 < a few ns
𝑚χ: 5 MeV is assumed,
but OK for any values < 𝑚𝐴′/2
𝑝 + 𝑇 → 𝐴′ +⋯𝐴′ → 𝜒 ҧ𝜒
completely
considerablycompletely
considerably
𝐸𝑟 > 14 keV (𝐸𝑟𝑚𝑎𝑥 ≃ 2𝐸𝜈
2/𝑀𝑇 for CsI)
Prompt ν: completed removed
Delayed ν (& DM signal): still remains
𝑇 < 1.5 μs
Delayed ν: considerably removed
DM signal: still remains
for CsI at COHERENT
Expected unit-normalized t-distributions of DM
& ν scattering events
ν events: ν scattering cross sections convolved
and stacked & collectively unit-normalized.
With appropriate t-cuts, delayed ν can be
significantly removed while a large portion of
DM events are retained.
Before t-cut After t-cut
t-cuts: delayed ν significantly removed & DM events almost retained.
CsI
LAr
E-cuts: prompt ν (completely) removed & DM events considerably retained.
Before t-cut After t-cut
t-cuts: delayed ν significantly removed & DM events almost retained.
CCM LAr
JSNS2
Gd-LS
E-cuts: prompt ν (completely) removed & DM events considerably retained.
COHERENT & CCM: designed to be sensitive the nucleus recoil [low 𝐸𝑟~𝑂(10 keV)]
JSNS2: a good sensitivity to the electron recoil [high 𝐸𝑟~𝑂(10 MeV)]
COHERENT-CsI: an upper 𝐸𝑟-cut beyond which BG uncertainties are high.
CCM: 50 keV is not the optimized cut, only 𝐸𝑟 > 50 keV data will be available.
CCM: two working points (WP) – a tight cut (the experimental recommendation) & a loose
cut (the t-spectrum of the DM signal)
Data released by COHERENT: CsI detector 14.57 kg×308.1 days [arXiv:1804.09459]
Analysis scheme
Fix the average rms radius of the neutron distribution to 𝑅𝑛 = 4.7 fm
14 keV < 𝐸𝑟 < 28 keV & 𝑇 < 1.5 μs 𝐹𝑁Helm 𝑞2 =
3𝑗1(𝑞𝑅0)
𝑞𝑅0exp(−
𝑞2𝑠2
2)
𝑅𝑛2 = 3𝑅0
2/5 + 3𝑠2
97 : total events
− 49 : classified as steady-state (SS) backgrounds
− 19 : identified as delayed (SM) ν events (due to 𝐸𝑟 & 𝑇-cuts)
− 0 : identified as prompt (SM) ν events (due to 𝐸𝑟-cut)
26 : “Excess!!”
Significance (𝑅𝑛 = 4.7 fm): 𝟐. 𝟒 𝝈
Significance (𝑅𝑛 = 5.5 fm): 𝟑. 𝟎 𝝈Significance =
𝑁obs−𝑁SS−𝑁BRN−𝑁𝜈
2𝑁SS+𝑁BRN+𝑁𝜈[arXiv:1801.05546]
[arXiv:1801.05546]
− 3 : beam-related neutron (BRN) backgrounds
Fits to the data w/ the cuts vs. w/o cuts (=the full data)
1𝜎-credible regions
𝑚𝑉
𝑚𝜒= 3 & 𝛼𝐷 =
𝜅𝐷𝑉 2
4𝜋= 0.5
A best-fit 𝐸𝑟 spectrum after t-cut
(𝑚𝑉 = 138 MeV & 𝑌 = 6.7 × 10−11)
Best-fit values of Y for several choices of 𝑚𝑉
Assuming no excess is observed, we can constrain parameter space.
Projected sensitivity in the single-
mediator scenario: a dark photon
mediator
Data & information about BGs are
available for COHERENT, but not for
CCM &JSNS2
A different curvature of JSNS2: due to
𝑚𝑒 ≪ 𝑚𝑉, but 𝑚𝑁 ≫ 𝑚𝑉 for others
NA64, BaBar: missing 𝐸𝑇
𝑚𝑉
𝑚𝜒= 3 & 𝛼𝐷 =
𝜅𝐷𝑉 2
4𝜋= 0.5
Assuming no excess is observed, we can constrain parameter space.
Projected sensitivity in the double-
mediator scenario: a U(1)B gauge
boson + a dark photon mediator for
illustration
𝜅𝑓𝑋 = 𝑔𝐵 = 2 × 10−3 & 𝜅𝐷
𝑋 = 10−7,
𝜅𝑓𝑉 = 𝜖𝑒, 𝛼𝐷 = 𝜅𝐷
𝑉 2/4𝜋 = 0.5
A different curvature of JSNS2: due to
𝑚𝑒 ≪ 𝑚𝑉, but 𝑚𝑁 ≫ 𝑚𝑉 for others
NA64, BaBar: missing 𝐸𝑇
No firm signal observation at conventional DM searches light dark sector.
A new strategy to search for light DM signals: A combination of T & E-cuts can
efficiently eliminate SM ν BGs at neutrino-beam experiments, e.g., CEνNS.
Application: the measured CsI data of the COHERENT experiment
Result: 𝟐. 𝟒 − 𝟑𝝈 excess!
The excess can be explained by DM arising from dark gauge boson decays.
COHERENT, CCM, JSNS2: capable of probing wide ranges of unexplored
parameter space, getting closer to the thermal DM relic density line via the
“appearance” of produced DM.