Xenophobic Dark Matter - Dakota State University

Xenophobic Dark Matter

David Sanford

Caltech

CETUP 2013 – Monday, June 24 2013

With Jonathan Feng, Jason Kumar, Danny Marfatia (Phys.Lett. B703 (2011) 124-127)
With Jason Kumar, Louis Strigari (Phys.Rev. D85 (2012) 081301)
With Jonathan Feng, Jason Kumar (hep-ph/1306.2315)

Current Status of Light Dark Matter

10-3 f n / fp= 1 Major inconsistencies
10-4 between experimental
10-5 DAMA 90% results
10-6
DAMA 3σ DAMA reports ∼ 9σ
signal but severely
σp (pb) CDMS-Ge ExclusioCnRESST-II CoGeNT constrained by other
(CoCllaDr-MFSie-lGdse) Edelweiss experiments

CDMS-Si CoGeNT reports
possible signal,
10-7 LUXCoPnrosejercvtaetdive recently shifted from
10-8 6 LUXRPeraoljiesctitced better understanding of
XENON100 surface events

8 10 12 14 16 18 20 Kelso, Hooper, Buckley (2012)

mχ CRESST reports a
possible viable region
not fully consistent with
either

Current Status of Light Dark Matter

10-3 f n / fp= 1 Major inconsistencies
10-4 between experimental
10-5 DAMA 90% results
10-6
DAMA 3σ CDMS and Edelweiss
report significant
σp (pb) CDMS-Ge ExclusioCnRESST-II CoGeNT bounds in moderate
(CoCllaDr-MFSie-lGdse) Edelweiss tension with CoGeNT
. . . but an independent
CDMS-Si analysis of CDMS data
shows the possibility of
10-7 LUXCoPnrosejercvtaetdive consistency
10-8 6 LUXRPeraoljiesctitced
XENON100 Collar and Fields (2012)

8 10 12 14 16 18 20 CDMS reports 3 event
in silicon detectors
mχ XENON100 heavily
constrains all positive
results
LUX is expecte to
improve sensitivity

Possible Ways to Address Discrepancies

Many approaches exist to address have been put forward to
resolve various discrepancies

Inelastic dark matter

Tucker-Smith and Weiner (2001)

Details of Leff in liquid xenon at low recoil energy

Collar and McKinsey (2010)

Channeling in NaI at DAMA

Bernabei et. al. [DAMA] (2007); Bozorgnia, Gelmini, Gondolo (2010)

Uncertainties in dark matter velocity distribution

Here the assumption of isospin conservation is rescinded

Unfounded theoretical assumption outside of purely
Higgs-mediated scattering
Ex: Z-mediated, dark photon with kinetic mixing, new
scalar or fermionic mediators

Focus on minimizing xenon cross-section

Isospin Conservation and Violation

DM-nucleus scattering is Dark Matter Compton Wavelength
coherent Nucleus

The single atom SI
scattering cross-section is

σA ∝ [fpZ + fn(A − Z )]2 Z : atomic number
∝ fp2A2 (fp = fn) A: number of nucleons
fp: coupling to protons
Well-known A2 fn: coupling to neutrons
enhancement for (fp = fn)

For fp = fn, this result must be altered

In fact, for fn/fp = − Z , σA vanishes from completely
A−Z

destructive interference

Z decreases for higher Z isotopes
A−Z

Dark Matter Experiments and Proton/Neutron Ratio

Z decreases for higher Z
A−Z

100 CoGeNT, Z=N
Edelweiss (Ge)

80

60

XENON10/100
LUX (Xe)

40

DAMA (NaI)

20 CDMS (Ge,Si)
CRESST (Ca, O, W)

N
Z 20 40 60 80 100

National Nuclear Data Center

Effects of Multiple Isotopes

Stable isotopes of Xenon (Z = 54):

A 128 129 130 131 132 134 136
Abundance (%) [ηi ] 1.9 26.4 4.1 21.2 26.9 10.4 8.9
-0.73 -0.72 -0.71 -0.70 -0.69 -0.675 -0.66
σA = 0 at fn/fp =

Cannot have completely destructive interference for more

than one isotope of an element

Experiments report the “normalized to nucleon

cross-section”

σNZ = σp i ηi µAi 2 [Z + (Ai − Z )fn/fp]2
i ηi µAi 2Ai2

σp: DM-proton cross-section
ηi : Relative abundance of an isotope
µAi : Reduced nucleon-DM mass for an isotope

Minimum for xenon found at fn/fp ≈ −0.70

Status of the Xenophobic Region

Maximal suppression of xenon sensitivity for fn/fp ≈ −0.70

10-1 Edelweiss f n / fp = -0.70 10-1 Edelweiss f n / fp = -0.64
10-2 10-2
CEDxMcSlu-sGioen 10-3 CEDxMcSlu-sGioen
10-4
DAMA 90%

C(CDoMllaSr--GFieelds) DAMA 3σ DAMA 90%

CoGeNT DAMA 3σ
σp (pb)
σp (pb) (CollCaDr-FMieSl-dGse) CoGeNT
10-3 CRESST-II
10-4 CRESST-II
10-5 6 CDMS-SXi ENON100
XENON100 CDMS-Si
CoLnUsXerPvraotijveected
LUX PRroejaelcistteicd LUCXoPnrsoejervcatetidve
8 10 12 14 16 18 20 LUXRPeraoljiesctitced

mX 10-5 6 8 10 12 14 16 18 20

mX

Better agreement of CDMS-Si and CoGeNT/CDMS-Ge
(Collar-Fields) for fn/fp ≈ −0.64

Enhancement/Suppression Relative to True σp

103 mDM = 8 GeV

Xe Ar Definitionally σNZ = σp at
σZN / σp102Si W fn/fp = 1
f n / fp= -0.7Ge O, N, He Definitionally σNZ /σp → ∞
f n / fp= -0.64Na C for fp → 0 (coupling only
f n / fp = 110to neutrons)

1H General suppression for
fn/fp ∼ −1
10-1 Point of maximum
suppression depends on
10-2 relative proton/neutron
content of nuclei
10-3

10-4

10--50.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5

tan-1[ fn / fp ] / π

Enhancement/Suppression Relative to True σp

10-1 Elements with only one
naturally abundant
10-2 isotope (O, N, He, Na, Ar)
are have cross-sections
σZN / σp10-3 completely suppressed at
10-4 one point
10-5-1 Xe
Si Elements with multiple
Ge isotopoes have a
Na maximum suppression
Ar ∼ 3 × 10−5 − 5 × 10−4
W
O, N, He Xe has a maximal
C suppression of 10−4
-0.9 -0.8 -0.7 -0.6 -0.5
Mass dependence very
fn / fp week

mDM = 8 GeV

Enhancement/Suppression Relative to True σn

Similar behavior for σNZ vs. σn

103 Xe Ar 10-1
Si W 10-2
σZN / σn102Ge O, N, He 10-3
f n / fp= -0.7Na C 10-4
f n / fp= -0.64 10-5-1
f n / fp= 110

σZN / σn
1H

10-1

10-2 Xe
Si
10-3 Ge
Na
10-4 Ar
W
10--50.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5 O, N, He
C
tan-1[ fn / fp ] / π
-0.9 -0.8 -0.7 -0.6 -0.5

fn / fp

mDM = 8 GeV

σp for general fn/fp

Can examine fn/fp 102
dependence at fixed mass
Displayed are slices of σp (pb)10
90% CL regions (unless f n / fp= -0.7
specified) for mX = 8 GeV f n / fp= -0.641
All other bounds are f n / fp= 1
above CoGeNT region 10-1
Overlap of CoGeNT,
CDMS-Ge (Collar-Fields), 10-2
CDMS-Si results occurs
for a large range of fn/fp 10-3
Evades XENON100
bounds only for a narrow 10-4 XECCDNCoMGSODe-GNDMNeT(AC1SoMl0la-r0SA-Fiie3ldsσ)
range of fn/fp 10-5

10--60.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5

tan-1[ fn / fp ] / π

σp for general fn/fp (cont.)

102 CoGeNT/CDMS-Ge
(Collar-Fields) partially
10 below XENON100 bound
only for
1 −0.72 ≈ fn/fp ≈ −0.63

σp (pb)10-1 CDMS-Si CoGeNT DAMA 3σ CDMS-Si partially below
10-2 CDMS-Ge (Collar-Fields) XENON100 bound for
−0.81 ≈ fn/fp ≈ −0.40
10-3
10-4 XENON100 Best avoidance occurs at
10-5 fn/fp ≈ −0.70, but best
overlap occurs at
10-6-1 -0.95 -0.9 -0.85 -0.8 -0.75 -0.7 -0.65 -0.6 -0.55 -0.5 fn/fp ≈ −0.64

fn / fp

Enhancement Relative to Xenon

106 More rigorously, ratio of
effective cross-sections
105 can be used to rescale
event yields
104

σZN / σXNe103 “If [experiment X] were

102 seeing dark matter,

10 XENON100/LUX/XENON1T/LZ

1 would see N events”

10-1 Rescales to N
σNZ /σNXe
10-2 H Ar
Si W
Ge O, N, He
10-3 Na C Maximum suppression of

10-4-1 -0.95 -0.9 -0.85 -0.8 -0.75 -0.7 -0.65 -0.6 -0.55 -0.5 ∼ 25 relative to

fn / fp germanium and ∼ 200

relative to silicon

Beyond Direct Detection

Limits from astrophysical and collider searches can be applied
to direct detection parameter space

Processes with direct detection signals generically
produce baryons or photons visible in indirect detection
Can also be probed at colliders through monojet (or
mono-photon, mono-W /Z , etc.)

. . . but requires model dependence

Candidate/operator nature defines relative size of various
processes
Large degeneracy of quark couplings for a given {fp, fn/fp}

Second and third generation couplings important but either
irrelevant or isospin-conserving

The most conservative bounds are found for coupling only to
up- and down- quarks

Comparing Results from Separate Regimes

A contact operator approaches provide the easiest method of
comparing results from separate regimes

Results for separate types of experiments are
unambiguous and model dependence is limited
Requires relatively heavy physics to be valid in all regimes

Choose operators which produce both s-wave annihilation and
un-suppressed scattering

If annihilation is p-wave indirect detection limits are too
weak
If scatterings is velocity-suppressed the required couplings
are too strong

Dirac fermion – vector coupling: OD = (1/M∗2)X¯ γµX q¯γµq
Complex scalar – scalar coupling: OS = (1/M∗)φ∗φq¯q
Real scalar – scalar coupling: OS = (1/M∗)φφq¯q

Gamma Ray and Collider Bounds on σp

Consider bounds by Fermi-LAT from dwarf spheroidals and
CMS monojet limits

Fermi-LAT unconstraining 102 CMS Complex Scalar
10
Antiproton bounds f n / fp= 1
similar to Fermi-LAT, 1
but suffer from σp (pb)10-1 Fermi Complex Scalar
significant uncertainty 10-2
in propagation models 10-3 Fermi Dirac
10-4
Jin, Miao, Zhou (2013) 10-5 DAMA 90% DAMA 3σ
10-6
CMS dirac limits are 10-7 CDMS-Ge ExcluCsiRoEnSST-II CMS Dirac
strong even for 10-8 6 (CoCllDarM-FSie-Gldes)
conservative coupling CoGeNT
assumptions
CMS bounds on scalars LUXRPearolijsetcicted XENON100CDMS-Si Edelweiss
are weaker by ∼ 5 orders CLoUnXsePrvroajteivceted
of magnitude
8 10 12 14 16 18 20

mX

Gamma Ray and Collider Bounds: Xenophobic Region

Both Fermi-LAT and CMS bounds become significantly more
constraining in the xenophobic region

10-1 Edelweiss f n / fp = -0.70 10-1 Edelweiss f n / fp = -0.64
10-2
10-3 CEDxMcSlu-sGioen CEDxMcSlu-sGioen
10-4
10-5 6 DAMA 90% 10-2
10-3
C(CDoMllaSr--GFieelds) DAMA 3σ 10-4 DAMA 90%
10-5 6 DAMA 3σ
CoGeNT
σp (pb) Fermi Complex Scalar
σp (pb)
Fermi Complex Scalar (CollCaDr-FMieSl-dGse) CoGeNT

CRESST-II CRESST-II Fermi Dirac

CDMS-SXi ENON100 Fermi Dirac

XENON100 CDMS-Si

LUX PRroejaelcistteicd CoLnUsXerPvraotijveected LUCXoPnrsoejervcatetidve
LUXRPeraoljiesctitced
CMS Dirac CMS Dirac

8 10 12 14 16 18 20 8 10 12 14 16 18 20

mX mX

∼ 5 − 6 orders of magnitude more constraining!

σp for general fn/fp

Fermi-LAT/CMS bounds become an order of magnitude more
constraining in xenophobic region

102 102

σp (pb)10 10
f n / fp= -0.71 CMS Complex Scalar
f n / fp= -0.64
f n / fp= 1 1

σp (pb)
CMS Complex Scalar

10-1 10-1 CDMS-Si
10-2
10-2 Fermi CompleFxeSrcmalai rDirac 10-3 CoGeNT DAMA 3σ
10-4 CDMS-Ge (Collar-Fields)

Fermi Complex Scalar

10-3 Fermi Dirac

10-4 XECCDNCoMGSODe-GNDMNeT(AC1SoMl0la-r0SA-Fiie3ldsσ) XENON100
10-5
CMS Dirac 10-5 CMS Dirac

10--60.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5 10-6-1 -0.95 -0.9 -0.85 -0.8 -0.75 -0.7 -0.65 -0.6 -0.55 -0.5

tan-1[ fn / fp ] / π fn / fp

Strengthening of relative bounds primarily due to increase in σp

Enhancement Relative to Xenon

Maximal enhancement relative to xenon of ∼ 105

106 H Ar f n / fp= -0.7 106

105 Si W 105
Ge O, N, He
Na C
104 LHC Dirac 104
LHC Scalar 103
103 Fermi Dirac
σZN / σNXe Fermi Scalar σZN / σXNe

102 102

10 10

1 1

10-1 f n / fp= -0.64 10-1 HHNSGSNGLHiiaaeeC/FermOAWCAOWCirr,,SNNc,,aHHlaeer
10-2 LHC/Fermi Dirac
10-2 f n / fp= 1 10-3

10-3

10--40.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5 10-4-1 -0.95 -0.9 -0.85 -0.8 -0.75 -0.7 -0.65 -0.6 -0.55 -0.5

tan-1[ fn / fp ] / π fn / fp

Avoiding Indirect Detection and Collider Bounds

Annihilation can be suppressed for operators with p-wave
annihilation but un-suppressed direct detection cross-sections

Effective operator description breaks down for annihilation and
collider searches at small mediator mass

Suppressed by ∼ (mφ/mX )4 for annihilation
Suppressed by ∼ (mφ/(2mX ))4 for collider searches
Asymmetric dark matter automatically avoids indirect detection

limits

Collider limits depend strongly on operator dimensionality

Conclusion

Significant inconsistencies exist in the realm of light dark
matter
There remains room for justifications related to the
underlying theory (as opposed to
astrophysical/experimental effects)
XENON100 provides significant limits on all other results,
requiring any realistic theory to be xenophobic

Within such xenophobic theories moderate consistency
between CDMS-Si and CoGeNT/CDMS-Ge (Collar-Fields)
can be achieved
Indirect and collider searches can strongly constrain
xenophobic theories
Significant model dependence in comparing results