19 research outputs found
Effective Theories of Gamma-ray Lines from Dark Matter Annihilation
We explore theories of dark matter in which dark matter annihilations produce
mono-energetic gamma rays ("lines") in the context of effective field theory,
which captures the physics for cases in which the particles mediating the
interaction are somewhat heavier than the dark matter particle itself. Building
on earlier work, we explore the generic signature resulting from SU(2)xU(1)
gauge invariance that two (or more) lines are generically expected, and
determine the expected relative intensities, including the possibility of
interference between operators.Comment: 11 pages, 0 figure
Higgs Boson Decays to Dark Photons through the Vectorized Lepton Portal
Vector-like fermions charged under both the Standard Model and a new dark
gauge group arise in many theories of new physics. If these fermions include an
electroweak doublet and singlet with equal dark charges, they can potentially
connect to the Higgs field through a Yukawa coupling in analogy to the standard
neutrino portal. With such a coupling, fermion loops generate exotic decays of
the Higgs boson to one or more dark vector bosons. In this work we study a
minimal realization of this scenario with an Abelian dark group. We investigate
the potential new Higgs decays modes, we compute their rates, and we study the
prospects for observing them at the Large Hadron Collider and beyond given the
other experimental constraints on the theory. We also discuss extensions of the
theory to non-Abelian dark groups.Comment: 32 pages, 5 figures, updated to match JHEP versio
Particle Physics Implications and Constraints on Dark Matter Interpretations of the CDMS Signal
Recently the CDMS collaboration has reported an excess of events in the
signal region of a search for dark matter scattering with Silicon nuclei. Three
events on an expected background of 0.4 have a significance of about 2 sigma,
and it is premature to conclude that this is a signal of dark matter.
Nonetheless, it is important to examine the space of particle theories capable
of explaining this excess, to see what theories are capable of explaining it,
and how one might exclude it or find corroborating evidence in other channels.
We examine a simplified model containing a scalar mediator particle, and find
regions consistent with the CDMS observations. Bounds from colliders put
important restrictions on the theory, but viable points, including points
leading to the observed thermal relic density, survive.Comment: 16 pages, 6 figure
Power Corrections to the Universal Heavy WIMP-Nucleon Cross Section
WIMP-nucleon scattering is analyzed at order in Heavy WIMP Effective
Theory. The power corrections, where is the WIMP mass,
distinguish between different underlying UV models with the same universal
limit and their impact on direct detection rates can be enhanced relative to
naive expectations due to generic amplitude-level cancellations at leading
order. The necessary one- and two-loop matching calculations onto the
low-energy effective theory for WIMP interactions with Standard Model quarks
and gluons are performed for the case of an electroweak SU(2) triplet WIMP,
considering both the cases of elementary fermions and composite scalars. The
low-velocity WIMP-nucleon scattering cross section is evaluated and compared
with current experimental limits and projected future sensitivities. Our
results provide the most robust prediction for electroweak triplet Majorana
fermion dark matter direct detection rates; for this case, a cancellation
between two sources of power corrections yields a small total correction,
and a total cross section close to the universal limit for . For the SU(2) composite scalar, the corrections
introduce dependence on underlying strong dynamics. Using a leading chiral
logarithm evaluation, the total correction has a larger magnitude and
uncertainty than in the fermionic case, with a sign that further suppresses the
total cross section. These examples provide definite targets for future direct
detection experiments and motivate large scale detectors capable of probing to
the neutrino floor in the TeV mass regime.Comment: 12 pages, 4 figures; references added, XENONnT projection included,
version to appear in Physics Letters
Compatibility of theta13 and the Type I Seesaw Model with A4 Symmetry
We derive formulae for neutrino masses and mixing angles in a type I seesaw
framework with an underlying A4 flavor symmetry. In particular, the Majorana
neutrino mass matrix includes contributions from an A4 triplet, 1, 1', and 1"
flavon fields. Using these formulae, we constrain the general A4 parameter
space using the updated global fits on neutrino mixing angles and mass squared
differences, including results from the Daya Bay and RENO experiments, and we
find predictive relations among the mixing parameters for certain choices of
the triplet vacuum expectation value. In the normal hierarchy case, sizable
deviation from maximal atmospheric mixing is predicted, and such deviation is
strongly correlated with the value of theta13 in the range of ~ (8-10) degrees.
On the other hand, such deviation is negligible and insensitive to theta13 in
the inverted mass hierarchy case. We also show expectations for the Dirac CP
phase resulting from the parameter scan. Future refined measurements of
neutrino mixing angles will test these predicted correlations and potentially
show evidence for particular triplet vev patterns.Comment: 22 Pages, 3 Figures; v2: version to appear in JHE
Power Corrections to the Universal Heavy WIMP-Nucleon Cross Section
WIMP-nucleon scattering is analyzed at order 1/M in Heavy WIMP Effective Theory. The 1/M power corrections, where M ≫ mW is the WIMP mass, distinguish between different underlying UV models with the same universal limit and their impact on direct detection rates can be enhanced relative to naive expectations due to generic amplitude-level cancellations at leading order. The necessary one- and two-loop matching calculations onto the low-energy effective theory for WIMP interactions with Standard Model quarks and gluons are performed for the case of an electroweak SU(2) triplet WIMP, considering both the cases of elementary fermions and composite scalars. The low-velocity WIMP-nucleon scattering cross section is evaluated and compared with current experimental limits and projected future sensitivities. Our results provide the most robust prediction for electroweak triplet Majorana fermion dark matter direct detection rates; for this case, a cancellation between two sources of power corrections yields a small total 1/M correction, and a total cross section close to the universal limit for M ≳ few x 100 GeV. For the SU(2) composite scalar, the 1/M corrections introduce dependence on underlying strong dynamics. Using a leading chiral logarithm evaluation, the total 1/M correction has a larger magnitude and uncertainty than in the fermionic case, with a sign that further suppresses the total cross section. These examples provide definite targets for future direct detection experiments and motivate large scale detectors capable of probing to the neutrino floor in the TeV mass regime
LHC Bounds on Interactions of Dark Matter
We derive limits on the interactions of dark matter with quarks from ATLAS
null searches for jets + missing energy based on ~1 fb^-1 of integrated
luminosity, using a model-insensitive effective theory framework. We find that
the new limits from the LHC significantly extend limits previously derived from
CDF data at the Tevatron. Translated into the parameter space of direct
searches, these limits are particularly effective for ~GeV mass WIMPs. Our
limits indicate tension with isospin violating models satisfying minimal flavor
violation which attempt to reconcile the purported CoGeNT excess with
Xenon-100, indicating that either a light mediator or nontrivial flavor
structure for the dark sector is necessary for a viable reconciliation of
CoGeNT with Xenon.Comment: 20 pages, 11 figure
Power corrections to the universal heavy WIMP-nucleon cross section
WIMP-nucleon scattering is analyzed at order 1/M in Heavy WIMP Effective Theory. The 1/M power corrections, where M ≫ m_W is the WIMP mass, distinguish between different underlying UV models with the same universal limit and their impact on direct detection rates can be enhanced relative to naive expectations due to generic amplitude-level cancellations at leading order. The necessary one- and two-loop matching calculations onto the low-energy effective theory for WIMP interactions with Standard Model quarks and gluons are performed for the case of an electroweak SU(2) triplet WIMP, considering both the cases of elementary fermions and composite scalars. The low-velocity WIMP-nucleon scattering cross section is evaluated and compared with current experimental limits and projected future sensitivities. Our results provide the most robust prediction for electroweak triplet Majorana fermion dark matter direct detection rates; for this case, a cancellation between two sources of power corrections yields a small total 1/M correction, and a total cross section close to the universal limit for M ≳ few x 100 GeV. For the SU(2) composite scalar, the 1/M corrections introduce dependence on underlying strong dynamics. Using a leading chiral logarithm evaluation, the total 1/M correction has a larger magnitude and uncertainty than in the fermionic case, with a sign that further suppresses the total cross section. These examples provide definite targets for future direct detection experiments and motivate large scale detectors capable of probing to the neutrino floor in the TeV mass regime
Dark Matter in the Coming Decade: Complementary Paths to Discovery and Beyond
In this report we summarize the many dark matter searches currently being
pursued through four complementary approaches: direct detection, indirect
detection, collider experiments, and astrophysical probes. The essential
features of broad classes of experiments are described, each with their own
strengths and weaknesses. The complementarity of the different dark matter
searches is discussed qualitatively and illustrated quantitatively in two
simple theoretical frameworks. Our primary conclusion is that the diversity of
possible dark matter candidates requires a balanced program drawing from all
four approaches.Comment: Report prepared for the Community Summer Study (Snowmass) 2013, on
behalf of Cosmic Frontier Working Groups 1-4 (CF1: WIMP Dark Matter Direct
Detection, CF2: WIMP Dark Matter Indirect Detection, CF3: Non-WIMP Dark
Matter, and CF4: Dark Matter Complementarity); published versio