Recent Developments in Dark Matter Detection

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Recent Developments in Dark Matter Detection

Ayan Mitra

M.Sc. Cosmology

Since 1930s there has been enormous speculations in the physics society on the presence

of dark matter and various projects have been undertaken one after other with the aim to

get some experimental verification and proof on the presence of dark matter. We aim topresent here a brief outline of the developments and the results of the projects undergone

and still going on with the aim of finding some dark matter evidence.

Dark matter(DM) can be classified into two broad

categories: 1. Baryonic 2. Non Baryonic. The latercan be subdivided into:1.Hot DM(HDM) 2.Cold

DM(CDM), of which the search for CDM is most

ongoing in the process of trying to detect theWeakly Interacting massive Particles(WIMPs).

There are direct ways and indirect ways of detection

which are used on ground based or satellite based

set ups. The recent developments in detectingWIMPs are as follows: I)Satellite based:

a) PAMELA-launched in 2006-Payload forAntimatter Exploration & Light nucleiAstrophysics.

1) Expected to detect evidence for DM

annihilation.2) Preliminary data indicate an excess of

positrons in the energy range of 10~60

GeV: thought to be a sign of DM

annihilation.3) Results however not fully convincing,as

there are possibilities that mission was

confusing positrons with far largenumbers of protons reaching its

detectors.

b) Fermi Gamma Ray Telescope-Launched in2008

1) One of the primary missions being,probe

DM by looking for an excess of gammarays from the center of the Milky Way.

2) The team working with Fermis maininstrument Large Area Telescope(LAT)

found positrons with energies upto 200GeV implying highly massive DM

particles.

Outlooks: the results very much rule out the

DM interpretation of the high energeticpositrons.No way to distinguish between

sources of positrons whether from DM or

pulsars.If positrons of even higher energiescontinue to pop in then the pulsar

explanation will also become strained.

II) Ground Based :a) LHC: indirect method of measurement.

1) The Compact Muon Solenoid ( CMSresults in relation to SUSY show that on

collisions of proton-proton pair rarely

sparticles may be produced, the lightest

of which is a dark matter candidate as itis stable.

2) Till January 2011, some 3 trillion p-p

collisions were examined and 13 SUSYlike ones were found of them. Although

no evidence of sparticles were found this

measurement narrows down the area forDM research significantly.

b) PICASSO- Project in Canada to Search fo

Susy Objects- a direct detection experiment.

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1) Looking for most favorable candidate

for cold DM namely,neutralino(WIMPs)

2) As of July 2009 no DM signal has beenfound.

c) DAMA/LIBRA & DAMA NaI( Italy)

1) Direct detection using scintillations2) DM particle investigation in galactic

halo by exploiting DM annual

modulation signature.3) Flash rates of scintillations highest in

June and lowest in December,implying

detection evidence of DM.

4) Results of this group though is notwidely accepted in the community.

d) CDMS-The Cryogenic DM

Search( Minnesota) .

1) Direct measurement of DM (WIMPScatter)

2) Data set of 2003 has not yielded in anyevidence of WIMPS

3) From 2008-09 data set processed using

blinding method show 2 events with

characteristics consistent for those ofWIMPS.

4) However it can be that both events are

due to background particles.e) DRIFT-Directional Recoil Identification

From Tracks.

1) Attempt to utilize WIMP wind byusing directionality sensitive DM

detector.

2) No significant results as of now.f) Super Kamiokande ( Japan)-

1) Detection of high energy neutrino

signals resulting from WIMP

annihilation in earth, the sun, galacticcenters.

2) Work mainly on Hot DM.

Baryonic DM:

III) MACHO: Massive Astrophysical

Condensed Halo Objects.

a) EROS1) EROS I (1990-95)- No halo

microlensing event found.

2) EROS 2(1996-03) From microlensing

analysis of small magellanic cloud

,stringent limits are put on the amount

of galactic DM made of compact

objects.Mass between 2 x 10(exp -7)solar mass and 1 solar mass can

account for more than 25% of the mass

ofstandard,spherical,isothermal,isotropic,

galactic halo of 4 x 10(exp 11) solar

mass with 50 KPc radius volume.b) The MACHO project(1992-99) ( USA &

Australia)

1) Results inferred that less than 1% halo

mass is red dwarf.2) This missing mass problem is no

solved by MACHO.

Conclusion:

While some of the projects are still runningyet not many of them has given anything

concrete as yet,but specially the results ofLHC are being eagerly awaited for by the

physics community for any breakthroughs

in DM frontier.i

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i References:

1) Retrieved from www.wikipedia.org

2) Retrieved from http://www.universetoday.com/82864/hunt-for-dark-matter-closes-in-at-the-lhc/

3) Retrieved from http://www.oglethorpe.edu/faculty/~m_rulison/Astronomy/Group/Spring%2099/dark_matter.htm

4) Retrieved from https://news.slac.stanford.edu/features/fermi-gamma-ray-space-telescope-confirms-

puzzling-preponderance-positrons5) Retrieved from http://eros.in2p3.fr/publications.html

6)Bergstrom, L. (2010, february 09). http://arxiv.org/abs/1007.0595.

6)Retrieved from http://arxiv.org/: http://arxiv.org/abs/1007.0595

7)Debtosh Chowdhury, C. J. (2009, september 07). Results from PAMELA, ATIC and FERMI :

Pulsars or Dark Matter ?8)Fermi LAT Collaboration: M. Ackermann, M. A. (2011, september 09).

http://arxiv.org/abs/1109.0521. Retrieved from http://arxiv.org/abs/1109.0521

9)Marco Farina, M. K. (18 Apr 2011). Implications of XENON100 and LHC results for Dark Mattermodels.

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Recent Developments in Dark Matter Detection