WIMP dark matter searches bymeasuring X rays and  rays

Hiro Ejiri
RCNP Osaka
For ICRR Seminar in March 7thThanks Prof. Moriyama.

1. Search for WIMPs
2. X ray measurements
3. Gamma ray measurements
4. Concluding remarks

A view from the Ejiri-weekend house

DM WIMP’s••

Dark energy 70%, DM 30 %, Baryonic matter 5 %.

DM : mainly of cold DM WIMP’s
LSP Lightest SUSY Particle. Neutralino

DM WIMP’s detection• Detection of WIMP’s is extremely hard.
•• A. Cross sections & fluxes are small <10-43cm2•
SI Spin Independent (coherent) = A2•
SD Spin dependent (coherent) = 1
B. Energy signals of recoil nuclei are
low and smooth as BG/noise.
•Recoil E ~ 50 keV.
•Detected E ~ 2 keV with quenching.

Event properties for WIMPs and DBD
DM WIMP 100 GeV

DBD  30 meV M=1.5

 Xe

p 10-45 cm2
Low luminosity

Rate (>Eth)170 (40)/ t y

2.5 /t yE(Quenched)

0-50 keV(1-2keV)*

2500 keVSpectrumContinuum*

PeakSolar  BG

1 /t y0.6/t y if E=50 keVBG required< 10/t y at a few KeV

0.5 / t y at a few MeV

 10-73 cm2High Luminosity

New points: non-quenched & discrete peakNoble methods to study low and rare WIMPs••* Annular modulation of E-spectra :Small ( % order) and subject to annular BG modulation* Direction of recoil: Ton-scale detectors are hard：(Emulsion).

• * Present; X – rays from inelastic/elastic scatterings
•
•
• .
•

Non-quenched and descrete line spectrum

A: Atomic electrons & X-rays with nuclear recoils
following WIMP/LSP nuclear interaction
H. Ejiri, Ch. C. Moustakidis, J.D. Vergados, PL. B639, 06, 218,
The role of ionization electrons in direct neutralino detection.
J.D. Vergados and H. Ejiri, PL B606 (2005) 305.

B: Nuclear inelastic  SD Spin dependent WIMPs
H.Ejiri, K. Fushimi, H. Ohsumi, Phys. Lette. B317 1993 14
J. Vergados, H. Ejiri , K.G. Savvidy Nucl. Phys. B 877 2013 36

2. X ray measurements

A sun rise view from the Ejiri-YokohamaX ray opens a new experimental window
K, L X rays

K ElectronWMP Nuclear recoilTT is a function of k, thus Eq.1. gives a relation of q and k for given
T and P of initial DM. Then one get k and T as a function of qUnique featuresof X rays
RecoilK -X

1. Descrete line,

Quenched

non-quenched ,at E(X) ~ 30 keV.
2. Well above E(threshold)~1-2 keV.
3. Peak yield is much larger than the continuum one spread over .
4. Production depends only on the WIMP recoil/momentum,
not on the nuclear structure and WIMP properties of SI/SD.
5. Exclusive coincidence studies with recoil to be free from BG

Cross section ratios in case of 1 electron and Z=54 e in
Xe for L/M/H=30 GeV, 100 GeV, and 300 GeV

Large number of inner-shell holes/X-rays, K=2 and L=6 .
K X rays if K hole is not 0 and 2s-2p electrons are not 0.

Sum of 4 K X-rays after fluorescence ratio of 89 %are
0.025 for 30 GeV and 0.22 for 300 GeV

WMP K, L X rays are summed up
in inclusive measurement
Nuclear recoil

Experiment inclusive
B. Recoil and K shell ionization 5-20 % for 50-300 GeV
E=Er + Ek,
Ek=K shell binding energy ~30 keV
Measured E=QEr+Ek Q=Quenching factor= Q(E-Ek) +Ek = QE + Ek(1-Q) shift

Quenched

RecoilK -X

Experiment (exclusive)
B. Recoil and K shell ionization
E=Er + Ek,
Ek=K shell binding energy
E=QEr and Ek Q=Quenching factor Er is small by Ek
Emulsion, Tracking chamber, Plastic fiber, ets

RecoilQuenched

RecoilK -X

BG consideration
1. Solar  : Same, but more for lighter DM with smller recoils.
Solar  recoil + K X ray
2. Neutrons: Same , but fast neutrons are by active PL shield
Neutron recoil + K Xray
3. RI continuum: No sharp rise at E(K)Solar Vergados EjiriNucl. Phys. B804 2008 144

Gamma rays from inelastic WIMP scatteringII. Nuclear inelastic  rays
H.Ejiri, K. Fushimi, H. Ohsumi, Phys. Lette. B317 1993 14
J. Vergados, H. Ejiri , K.G. Savvidy Nucl. Phys. B 877 2013 36

1. Larger signals~ 50 keV than quenched recoil signals
2. Sharp peak at E=58 keV and 40 keV in case of 127I and 129Xe.
3. Incoherent much smaller (10-5) cross-section for spin-coupled DM

100 %

Inelastic NMEｓ：Toivanen Kotelainen Suhonen
Int. J. mod. Phys. E 14 (2005) 751

26.4 %

x4x4×0.4

Exclusive study of X rays in coincidence withnuclear recoil

LSP

X ray Photo electronThin(~300)
scintillator

Atomic electron

Nuclear recoil

Long flight pass, K: 0.1 gr, L: 0.01 gr.
Exclusive coincidence measurements of X-rays and nuclear
recoils.

Muliti-layers of thin NaI plates Fushimi et al Tokushima Osak••••••NaI 500 m x 50 mm x 50 mm
LG 500 m x 60 mm x 60 mm
16 modules (phase 1 present)
256 modules (phase 2)
Sensitivity ~ 1 GeV /cc
one order improvement.

57 keV  efficiency at n+1 th NaI when recoil at n th NaIConcluding Remarks.

1. E-spectrum of nuclear recoils from WIMPs (LSP) is of low-E
continuum like BG, being hardly identified by inclusive studies.
2. Atomic electron ionization in WIMP nuclear interactions
provides noble methods for high-sensitive WIMP studies.
The ionized electrons with E ~ keV can be studied in TPC.
3. K X-rays with 30 keV in I-Xe detectors are measured
exclusively in coincidence with nuclear recoils by a multi-layer
thin (~300 m ) NaI array.
4. The inclusive measurement of the E-shifted sharp-rise
spectrum is a new high sensitivity WIMP search.
5.
Exclusive and inclusive measurements of  following inelastic
scattering of WIMPs are very sensitive for SI.
6. MOON (Multi-later NaI-scitillators Observatory Of Neutralinos)
MOON( Multi-layer PL-scintillator Observatory Of Neutrinos) fThank you for youｒ attention

Ejiri-weekend house at Shounan