Dark Matter Consistent with DAMA
Spencer Chang (UC Davis) work in collaboration with
Dark Matter Mystery
● Dark matter implied by astronomy and cosmology, but
mysterious from
particle physics view
● Many experiments will probe it: collider, direct and indirect
detection experiments
DAMA/NaI and DAMA/LIBRA
● DAMA only experiment focusing on modulation
● Has seen an
excess consistent with expected
behavior of DM
25 NaI detectors w/ 2 PMT's each
Modulation
● Due to earth's (and sun's) orbit, velocity distribution changes seasonally
Dec 2nd
Minimum June 2nd
Maximum
232 km/s
30 km/s
Drukier, Freese, Spergel
Modulation (cont.)
● dR/dER = S0 + Sm cos[2π(t-t0)/T]
● Expect T = 1 year, t0 = June 2nd
(152nd day), Sm
positive (negative) for large (small)
Dec 2nd
June 2nd
=
mN E Rβmin
Data Consistent with DM modulation
Expectations 1 152
●
Modulation Spectra
Most events expected at low energy
Consistent Models vs DAMA
● DAMA/LIBRA data is now detailed
enough to pin down parameter space of dark matter candidates
● Can check if those models are allowed by other data
● Consider spin-independent scattering
– Elastic case, requires light dark matter
– Inelastic dark matter
Elastic DM
DAMA spectra for different masses (GeV)
12
7 2
77
SC, Pierce, Weiner
See also Fairbairn, Schwetz and Freese et.al.
Data points pick out preferred mass regions
Fact that the first few points are “low” drives
the fit
LDM Plots
Spectral information disfavors m < 10 GeV Need nonstandard astrophysics/expt'l issues for consistency
SC, Pierce, Weiner
DAMA 68,90,99%CL
Regions
Envelope is 2 bin DAMA fit
●
Inelastic Dark Matter
● Models where dark matter scatters dominantly inelastically off nuclei
● Adds extra parameter δ, mass splitting to heavier state
● Kinematics produces a few effects
● Originally proposed to reconcile CDMS and DAMA
Smith, Weiner
SC, Kribs, Smith, Weiner
Preference for Heavy Targets
● Threshold velocity in order to excite to higher DM state
● Heavier targets sample lower
velocities, giving enhanced rates
min= 1
2 mN E R
mN NER
threshold=
2NCDMS DAMA
e.g.
m=100 GeV, δ=120 keV
Distinct Spectra
● Low energy recoils require higher
velocities
● Full expt'l spectra is important,
model, constraints depend strongly
on event
min= 1
2 mN E R
mN NER
Enhanced Modulation
● Sampling of higher velocity tail, means more modulation
● Expt: Dates of data taking crucial to
setting limits. Can
search for enhanced modulation
Modulation in observed DAMA range
Preferred Splitting
Benchmark Values
DAMA Spectra Benchmarks
For different dark matter masses, each fit prefers a range for δ, as it shifts the peak
IDM Plots
Constraints CRESST
XENON Data
Analysis region
(< 27 keV) misses most of the IDM recoils
CRESST Data
Seven events observed, lower than we expect, but inconsistent with expected
Conclusions
● DAMA's new data is predictive enough to set up a non-moving target
● Light Dark Matter
– Low threshold expts: CDMS, CoGeNT, and even XENON will probe further
● Inelastic Dark Matter
– Heavy target expts: CRESST, XENON, LUX, KIMS, ZEPLIN should see high
energy events and possibly modulation
Extra Slides
Direct Detection Rates (SI)
Astrophysics
Particle Physics
Experimental
Total convolution must be unraveled to connect to
fundamental physics
Models of IDM
● Sneutrino with lepton number violation
● Pseudo-Dirac Neutrino
∂ Z ⊃ R ∂ I −R ∂ I Z
= Ri I / 2
Z⊃ Z −
=
±=± Mass splitting technicallynatural due to breaking of
U(1) symmetry
Theory of Dark Matter
● Dark matter mass due to ATIC is 800 GeV – 1 TeV
● Attempts to get DAMA by inelastic scattering
– Plots from before rule out m > 250 GeV
● However, the inelastic scattering is
mediated by light vector φ, giving 1/(q2- m 2)2 in rate
Preliminary Results: Pushes to larger δ mφ ~ 8 MeV mφ ~ 80 MeV
CDMS CRESST