Searching for Dark Matter
Beyond the Neutrino Floor.
A literature review presentation by
Warren Lynch
Contents
• Introduction:
– Experimental evidence for dark matter
– Theoretical motivation for dark matter
– Direct Detection Methods
– Neutrino Floor
• Dark matter search methods to overcome the neutrino floor:
– Increasing mass time exposure
– Directionality
– Annual modulation
– Target complementarity
– Polarizing Helium-3
• Summary
Experimental Evidence
• Mass/light ratio of galaxy clusters [1]
• Gravitational rotation curves [2]
• Gravitational Lensing [3]
• Cosmic Microwave Background
Figure 1: The Bullet cluster [4]
(CMB) [5]
-Baryonic matter density: 0.0486±0.0010
-Dark matter density: 0.2589±0.0057
• Big Bang Nucleosynthesis [6]
Figure 2: CMB temperature power
spectrum [5]
Theoretical Motivation
• Supersymmetry (R-Parity conservation) – Lightest
supersymmetric particle (LSP) [7]
• Universal Extra Dimension (KK-parity) – Lightest Kaluza-Klein
particle (LKP) [8]
• Little Higgs (T-parity) – Lightest T-odd particle (LTP) [9]
• WIMP Miracle [10]
Direct Detection Methods
• Scintillation
- LUX (lqd), Zeplin (lqd), LZ(lqd), COSINE
(crystal), DAMA/LIBRA (crystal)
Figure 3: LZ
two stage
signal [11]
• Ionisation
- Drift IId (gas), DMTPC (gas), LUX (lqd),
Figure 4:
Crystal
phonon
vibration [12]
Zeplin (lqd), LZ (lgd)
• Phonon vibration
- CDMS/SuperCDMS (crystal),
CRESSTII (crystal), EDELWEISS-II
(cystal)
Figure 5:
Ionisation[13]
• LHC
For an overview of detector techniques see [14]
The Neutrino Floor
Neutrino’s and dark matter
candidates can not be shielded
against.
Only electron-neutrino interactions
have been observed [15].
Figure 6: Current experimental limits (solid
lines), future experimental predications
(dashed lines) and the neutrino floor [16]
Future DM detectors could also
conduct neutrino physics.
The Neutrino Floor
Contributions to the neutrino floor come from [15]:
• Atmospheric neutrinos produced by cosmic ray collisions
with the atmosphere.
• Solar neutrino’s (mostly B8) produced via the pp chain.
• Diffuse Supernova Neutrino Background (DSNB).
Figure 8: PPIII chain.
Figure 7: Cosmic ray interaction with
the atmosphere
Mass Time Exposure
• 1/MT with negligible neutrino
background
• 1/√(MT) as detector becomes
sensitive to neutrino
background
• Constant as neutrino
background begins to saturate
[17]
Figure 9: Discovery limit for a 6 GeV/c2
DM particle against neutrino
background [17]
Annual Modulation
• Method for discriminating a WIMP signal from solar neutrinos.
• Solar neutrino signal peaks around January 4th
• WIMP signal peaks around early June
• Timing difference and compression increases with cross section [18]
Figure 10:
Residual
modulation of
DM only,
neutrinos only
and DM +
neutrinos for two
different cross
sections [18]
Directionality
• Method for discriminating a WIMP • Wimps expected to come from the
signal from solar neutrinos.
• Solar neutrinos come from the
Sun.
Figure 11: Mollweide projection of
the angular differential event rate
for B8 solar neutrinos and for
WIMPs. The events are binned into 3
equal energy regimes between 0-5
keV [19]
constellation Cygnus.
• Directionality gives discrimination
between the two signals.
Target Complementarity
• Similar spectra from WIMPs and neutrinos at each particular WIMP
mass and cross section [20]
• The particular WIMP mass and cross section is target material
dependent [20]
• Comparing spectra for different target material gives discrimination.
Figure 12: The difference in cross
section from the same wimp
interaction for target material of
differing atomic mass number, A.
Shows results for SI, SD-N and SD-P
[20]
Polarised Helium-3
• Polarising the nuclear spin of helium3 in the opposite direction to
incoming neutrinos
•
Can be used to reduce solar neutrino
interactions (98%) [21]
• Can be polarised at high pressures
using Spin Exchange Optical
Pumping (SEOP) [22]
• Can be polarised at low pressures
Figure 13: Differential cross section for He3 neutrino interactions at different angles
between the incoming neutrino direction
and the h-3 spin[21]
• Good WIMP target
using Metastability Exchange Optical • Detector needs to point
Pumping (MEOP) [23]
towards the Sun.
Summary
• If the next generation of dark matter detectors (such as LZ) fails to
find dark matter then future detectors would need to investigate
parameter space populated by neutrinos.
• As dark matter detectors become more and more sensitive they
should start to see electron-neutrino interactions and possibly
neutrino-nuclei interactions for the first time. Future detectors may
conduct both dark matter and neutrino physics.
• Possible techniques for future detectors include: Increasing mass
exposure, annual modulation, directionality, target complementarity,
polarised He3 or some combination of the above.
References
[1] Zwicky Ref: F. Zwicky, Astrophysical Journal, Vol 86, No. 3 (1937)
[2] V. Rubin & W. Kent Ford Jr, Astrophysical Journal, Vol 159, No 2 (1970)
[3] T. Tommaso, P. Marshall, D. Clowe, American Journal of Physics, vol 80, iss 9, 753 (2012)
[4] https://apod.nasa.gov/apod/ap060824.html
[5] Planck Collaboration. Astronomy & Astrophysics manuscript no. planck ‘parameters’ 2015
(2016)
[6] R. Alpher, H. Bethe, G. Gamow, Phys. Rev. Lett. Vol 73. No 7. (1948)
[7] G. Jungman, M. Kamionkowski, K. Griest, Phys. Reports 267, 195-373 (1996)
[8] H-C Cheng, J. Feng, K. Matchev, Phys. Rev. Lett. 89, 211301 (2002)
[9] A. Birkedal et al arXiv:hep-ph/0603077v3 (2012)
[10] https://www.astro.umd.edu/~ssm/darkmatter/WIMPexperiments.html
[11] https://lz.slac.stanford.edu/our-research/lz-research
[12] https://www.slac.stanford.edu/exp/cdms/
[13] http://www.ast.cam.ac.uk/ioa/meetings/dv10/talks/dv10_day2_neil_spooner.pdf
[14] https://indico.cern.ch/event/336103/contributions/786765/attachments
/1205087/1755694/baudis_texas15.pdf
[15] J. Monroe and P. Fisher, Phys. Rev. D 76, 033007 (2007).
[16] http://www.slac.stanford.edu/econf/C1307292/docs/CosmicFrontier/WIMPDirect-24.pdf
[17] J.Billard, E. Figueroa-Feliciano, L. Strigari, Phys. Rev. Lett. D 89. 023524 (2014)
[18] J. Davis, Journal of Cosmology and Astroparticle Physics 03, 012 (2015)
[19] A.Ciaran, J. O’Hare et al Phys. Rev. Lett D 92, 063518 (2015)
[20] F. Ruppin, J. Billard, E. Figueroa-Feliciano, L.Strigari, Phys. Rev. Lett D 90, 083510 (2014)
[21] T. Franarin, M.Fairbairn. Phys. Rev. D 94, 053004 (2016)
[22] T. Walker and W. Happer, Rev. Mod. Phys. 69, 629 (1997)
[23] F. Colegrave, L. Schearer, G. Walters, Phys. Rev. 132, 2561 (1963)