1. Search of Dark Matter Candidate
Oldest living city on the planet!
Search of Dark Matter Candidate
Venktesh Singh
Institute of Science, Banaras Hindu University
@ WAPP – 2016 on Dec. 24, 2016

3. TEXONO [since 1997] : TEXONO Collaboration
 Neutrino Physics at Kuo-Sheng Reactor Neutrino Laboratory (KSNL)
Taiwan (AS, INER, KSNPS)
India (BHU)
Turkey (METU,DEU)
Taiwan EXperiment On NeutrinO
Research Program: Low Energy Neutrino and Dark Matter Physics

4. Kuo-Sheng Reactor Neutrino Laboratory
28 m from 2.9 GW
Shallow site : ~30 mwe overburden
~10 m below ground level
 = ~6.35 x 1012cm-2s-1 4 4

5. Kuo-Sheng Reactor Neutrino Laboratory
Front View (cosmic vetoes, shielding, control room …..)
Configuration: Modest yet Unique
Flexible Design: Allows different detectors conf. for different physics 5
Inner Target Volume 5

6. Neutrino Properties & Interactions at Reactor
mass
quality
Detector requirements
Threshold ~ 100 eV
Observable Spectra with Reactor Neutrino “Beam”
[3]
[1]
1 counts / kg-keV-day
SM & NSI/BSM ne Scattering [PRD10,PRD10,PRD12]
 200 kg CsI(Tl)
[2]
nN Coherent Scattering
sub-keV O(kg) Ge
Dark Matter KSNL [PRD09;PRL13,AP14]
[PRD13,PRD14, arXiV: ]
Magnetic Moments [PRL03,PRD05,PRD07]
 1 kg HPGe

7. Sub-keV Germanium Detector
4X5g ULEGe
900g PCGe
500g PCGe

8. Neutrino – Nucleus Coherent Scattering
 Standard Model allowed and predicted processes :
n (c)
Neutral current process (same for all n-flavor)
s  N2 @ En < 50 MeV
“Coherent” [probe “sees” the whole nucleus]
Sensitive probe for BSM; interest in reactor monitoring
Important process in stellar collapse & supernova explosion
Analogous interaction used in dark matter detection
Ge at QF~0.2 : cut-off ~ 300 eV; Rate ~10 kg-1 day-1 \
@ threshold~100 eV

9. Standard Model Cross – Section at KSNL
[ with Quenching Function for Ge for nuclear recoils ]
Needs Background < 10 cpkkd, Target 1 cpkkd
Current Focus !!
Needs Threshold < 200 eVee, Target  100 eVee

10. Origin of the Dark Matter Concept
Virial theorem：In the stationary gravitational system, the potential energy is twice the kinetic energy!
In 1933，Prof. Zwicky at Caltech studied the kinetic energy of the Coma cluster, he found that the kinetic energy is far bigger than the potential energy created by luminous mass. He proposed the concept of “dark matter”
According to his calculation, the mass of the dark matter must be as much as 300 times of the ordinary matter. 10

11. How do we know dark matter exists?
Velocity curves of spinning galaxies
In the 1970’s Vera Rubin, measured the speed of stars in rotating
galaxies accurately enough to convince the scientific community.
She observed that stars in spinning galaxies were all rotating at roughly the same velocity, no matter their distance to the galactic centre.
This is in contradiction with Kepler’s law that describes the rotation of planets around the Sun.
A planet located farther from the Sun rotates slower (A).
Vera Rubin showed that stars in a spinning galaxy followed curve (B).
This was as if the stars were not rotating around the visible centre of the galaxy but around many unknown centres, all providing additional gravitational attraction.
This could only happen if huge amounts of invisible matter filled the entire galaxy and beyond.

12. Evidences for Dark Matter IT MEANS DARK MATTER IS PRESENT.
If there were no dark matter:
Galaxy clusters would not have formed
Hot gas surrounding most galaxy clusters would have escaped
Galaxy collisions would look different
Most stars would have escaped from galaxies
There would be much less structure in the universe!
Unless Newton’s Gravitation Law is wrong!
IT MEANS DARK MATTER IS PRESENT.

13. Astrophysical Evidences
CMB Fluctuation
Dark matter has already been discovered through
Galaxy clusters
Galactic rotation curves
Weak lensing
Strong lensing
Hot gas in clusters
Bullet Cluster
Supernovae
CMB
We have entered in the regime of dark matter identification

14. Milky Way’s Dark Halo
Fig. from L.Baudis; Klypin, Zhao and Somerville 2002
Cold dark matter is present at all scales including galactic halos (rotation curves), including ours (revolution speed of Magellanic Clouds, etc.)
If dark matter particles do not have weak
interaction, no hope to detect them, if they
do are called WIMPs NB. Not necessarily only one type
1010 (GeV/m) WIMP’s passing through us per cm2 per second ! 14

15. Energy Budget of Universe
” We know less than nothing ! “
Dark Matter: Obeys known Laws of Gravitation.
Dark Energy does NOT !
Know nothing ! But perhaps have better guesses.

16. What we know about DM? Nothing about Dark Energy !!!
Know something !
All we know is that dark matter reacts to gravitation but not to electromagnetism since it does not emit any light i.e. electric charge =0 and colourless
It should be massive
Very long lived or absolutely Stable
Very Weak in nature
Hot or warm or cold, prefer cold dark matter
Mass, spin NOT known
May be it interacts with ordinary matter through the weak nuclear force, the one responsible for radioactive decays.
Dark matter would then be made of weakly interacting particles.
Nothing about Dark Energy !!!

17. Properties of Good Dark Matter Candidates
No charge, no colour (weakly interacting)
Stable: because of their non-interacting nature it must exist today and therefore long lifetime.
Cold, non-relativistic (mass >> kinetic energy)
Motivated by theory

18. Standard Model of Particles18

19. DM Candidates in Particle Physics
Phys. Rev. D 75, (2007) 19

20. Non-WIMP Dark Matter 20

21. Dark Matter Candidates

22. WIMP

26. The World Wide WIMP Search
Kuo Sheng
TEXONO
INO
DINO
Many experiments are collecting more data and new ones are being built. With theorists and experimentalists being hard at work, hopefully there will soon be a breakthrough.

27. Point Contact ULE-HPGe Detector
Exploring Ge detector technologies
The first are novel point-contact, p-type (P-PC) detectors
☻ excellent interaction separation capability
☻ superior energy resolution
☻ and low energy threshold
This is due to the point contact’s small capacitance (<1pF) and the rapidly changing electrical weighting field in the vicinity of the readout contact.
Advantages
very effective active background separation by pulse-shape analysis with only one readout channel and therefore minimum amount of potentially radioactive materials, particularly close to the detector.

28. Point Contact ULE-HPGe Detector
Pulse shape from closed-end coaxial p-type Ge detector. The P-PC Ge detector implementation
P. S. Barbeau et al, J. Cosmology and Astroparticle Phys.09, 009 (2007)

29. ULE-HP-PC-Ge Detector
A demonstration of the improved energy resolution and threshold for P-PC detectors versus a typical coaxial HPGe detector.

30. ULE-HP-PC-Ge Detector
Pulse shape analysis of a P-PC Ge detector showing the efficiency of rejecting multi-site events (high-energy  rays) and accepting single-site events (a double escape peak).

31. Dark Matter Searches
Sensitivity reach of the same configuration at different detector threshold, showing the relative improvement in cross-section as a function of m.
Measurable recoil spectra for WIMP-Ge interactions at a cross-section of cm2, at various values of m. The lower bounds of m as a function of physics threshold is also shown, assuming 1 kg-yr of data and a background level of 1 kg-1keVee-1 day-1. Quenching effects of nuclear recoils are taken into account.

32. Energy Measurement: Energy Calibration
Reset Preamp
PCGe
SA: Shaping time 0.5 ms to fit in one frame ; Typical operation in 6-12 ms
Typical SA6 pulse at 6 s shaping time. The various key parameters for analysis and calibration purposes are shown.

33. Bulk and Surface event Identification

34. Bulk and Surface event selection efficiency

35. Bulk and Surface event selection efficiency

36. Energy Measurement: Energy Calibration
The ULEGe is an n-type detector and with thin surface layer. It is also equipped with a thin cryostat window which allows detection of external X-rays lines.
Typical ULEGe, pPCGe and nPCGe spectra showing X-ray peaks and noise-edge. The lines in all cases are used in energy calibration. The peaks are due to electron capture of cosmogenic activated isotopes producing X-rays inside the detectors. The noise-edge is defined as the energy when physics events would take over from the self-trigger electronic noise spectra.

37. Summary table of Ge detector performance

38. Light WIMP Searches with Ge @ KSNL
[PRL13,AP14] :
500 eV threshold
devised schemes for B/S separation & efficiencies
probed and excluded some light WIMP allowed regions
Indicated: leakage of “Surface” background to “Bulk” samples can give false positive signals.
Learn & Establish Techniques
Catalyze CJPL
Produce Physics Results !

39. Light WIMP Searches Sensitivity
L. Baudis, arXiv:
Limits are getting better and better ….
So be positive and wait for positive claim….

40. Future Prospect: Spherical Drift Chamber
2.0 cm Poly
Gas outlet
0.5 cm Cu
0.5 cm Poly
50 cm
+HV out put
Proposed Plan
0.25 cm Anode
0.5cm Gas Inlet
+ HV BNC
0.25cm Poly Insulator

41. One step forward: Spherical Drift Chamber
Working on pressure test and limit
Electrode design
Input power and signal circuit
Many more things !

42. Future Prospect: Spherical Drift Chamber

43. UNDER MOUNTAIN DISADVANTAGE ADVANTAGE Long time to build Costly
Vertical muon intensity vs depth (1 km .w. e. = 105 g cm-2 of std. rock). The experimental data are from: :the compilations of Crouch, : Baskan, : LVD, : MACRO, : Frejus. The shaded area at large depths represents neutrino-induced muons of energy above 2 GeV. The upper line is for horizontal neutrino-induced muons, the lower one for vertically upward muons.
DISADVANTAGE
Long time to build
Costly
Various issues to clear
Rock composition is not well known
Height is not flat
Density and water contents is not homogeneous
Uncertainty in muon flux calculation
Neutron backscattering through Cavern walls
Many more
ADVANTAGE
Stable, long term active lab
Easy access, installation and maintenance
Easy supply of water and electricity
Live laboratory

44. Future Prospect: Deep Sea with Press.Vessel
ADVANTAGES
Less time
Cost effective
Plane surface
Well understood composition
Good Neutron absorber
No backscattering
DISADVANTAGES
Not convenient for each type of detector
No human access
Require very long power supply cables
Limited access

45. BACKGROUND FOR DARK MATTER
Shielding 0.5 cm copper, followed by 8.6 cm polyethylene, 22.5 cm lead, and 40 cm of polyethylene as the outer neutron shield.
Shielding, interchanged the thick polyethylene and lead shield positions.
A reduction in background by about a factor of 2 is observed.
The muon-induced background is dominated by elastic scattering of neutrons depositing visible energy in a 10 to 100 keV region. Uncertainties reflect those present due to uncertainties in the rock composition and in generating the muon-induced fast neutron flux.
The WIMP searches requires above 5 km. w. e. depth.

46. Depth can be achieved with the help of proper layering of minimum required shielding.
Depth can be achieved by the usage of cosmic-ray, neutron and anti-Compton veto detectors.

47. New Idea for Dark Matter Search
Place Array of P+ PCGe detector with sub-detectors
Ultra High Pressure Vessel
Under deep sea water
Supply HV only thru cable
Access Remotely

48. New Idea for Dark Matter Search
HPGe Detector LN2 Cooled
HPGe Detector Mechanically Cooled
HPGe detectors of ORTEC X-Cooler II at deep underwater laboratory.
The typical rate of LN2 evaporation at room temperature is 0.36 Lt/day.
Temperature at the depth of 3000 m is in between 2-4oC.
Therefore, with a 100 Lt dewar an experiment can survive up 275 days without any interruption and this period is enough to settle-down the cosmogenic bkg.

49. Future Prospect: Deep Sea with Press.Vessel
Shorter is Better
Suitable Location
Longer than 40 km, single high voltage & signal cables are in experimental use (ANTARIS).
Each 3500m depth of seawater will give >100 m extra over burden of freshwater.
Deeper is Better
BHU Proposed Plan
Goal: To establish multidisciplinary live laboratory under deep sea water

50. Challenges
Ventilation of LN2
Pressure vessel

51. Possible sites around the WORLD

52. World’s the Best Site
The Mariana Trench is located at 11o21'N & 142o12'E near Japan is in Pacific Ocean is the deepest location of earth itself with a depth of meters.

53. The World’s Best Site

54. Conclusions
Mounting evidence that non-baryonic Dark Matter and Dark Energy exist
Immediately imply physics beyond the SM
Dark Matter likely to be TeV-scale physics
Search for Dark Matter via
Collider experiment
Direct Search (e.g., CDMS-II)
Indirect Search (e.g., ICECUBE)
We are moving forward in establishing DM-lab in India

55. A New Window : “ don’t know what to expect & what are expected ”
OUR GOALS: To open new detection channel and detector window for neutrino and dark matter physics that can surprise the WORLD.
A New Window : “ don’t know what to expect & what are expected ”
Thank you !!

56. Dark Matter rediscovered
Origin of the Dark Matter Concept
Dark Matter rediscovered
In 1970’s Vera Rubin found that the rotation curves of galaxies ARE FLAT!
Dark Matter dominates in galaxies e.g. in NGC3198
We are going to concentrate on the DM in the Dark Halo of our own galaxy