95 research outputs found
Contributions of flavor violating couplings of a Higgs boson to
We study contributions to in models with a new Higgs boson, , and a
neutral lepton, , with couplings and
through the process . Contrary to naive expectations, we find
that contributions to can be very large while satisfying constraints
from standard and searches. Even the excess
observed by ATLAS in , if taken at face value, can be easily
accommodated. The various kinematic distributions fit nicely the experimentally
determined ones. This scenario can arise for example in a two Higgs doublet
model with vectorlike leptons.Comment: 16 pages, 5 figure
Dark Matter "Collider" from Inelastic Boosted Dark Matter
We propose a novel dark matter (DM) detection strategy for the models with
non-minimal dark sector. The main ingredients in the underlying DM scenario are
a boosted DM particle and a heavier dark sector state. The relativistic DM
impinged on target material scatters off inelastically to the heavier state
which subsequently decays into DM along with lighter states including visible
(Standard Model) particles. The expected signal event, therefore, accompanies a
visible signature by the secondary cascade process associated with a recoiling
of the target particle, differing from the typical neutrino signal not
involving the secondary signature. We then discuss various kinematic features
followed by DM detection prospects at large volume neutrino detectors with a
model framework where a dark gauge boson is the mediator between the Standard
Model particles and DM.Comment: 6 pages, 4 figures, 2 table
Searching for Boosted Dark Matter via Dark-Strahlung
We propose a new search channel for boosted dark matter (BDM) signals coming
from the present universe, which are distinct from simple neutrino signals
including those coming from the decay or pair-annihilation of dark matter. The
signal process is initiated by the scattering of high-energetic BDM off either
an electron or a nucleon. If the dark matter is dark-sector U(1)-charged, the
scattered BDM may radiate a dark gauge boson (called "dark-strahlung") which
subsequently decays to a Standard Model fermion pair. We point out that the
existence of this channel may allow for the interpretation that the associated
signal stems from BDM, not from the dark-matter-origin neutrinos. Although the
dark-strahlung process is generally subleading compared to the lowest-order
simple elastic scattering of BDM, we find that the BDM with a significant boost
factor may induce an O(10-20%) event rate in the parameter regions unreachable
by typical beam-produced dark-matter. We further find that the dark-strahlung
channel may even outperform the leading-order channel in the search for BDM,
especially when the latter is plagued by substantial background contamination.
We argue that cosmogenic BDM searches readily fall in such a case, hence taking
full advantage of dark-strahlung. As a practical application, experimental
sensitivities expected in the leading-order and dark-strahlung channels are
contrasted in dark gauge boson parameter space, under the environment of DUNE
far-detectors, revealing usefulness of dark-strahlung.Comment: 9 pages, 4 figures, Journal-submitted versio
D0 dimuon charge asymmetry from B_s system with Z' couplings and the recent LHCb result
The D0 collaboration has announced the observation of the like-sign dimuon
charge asymmetry since 2010, which has more than 3\sigma deviation from the
Standard Model prediction. One of the promising explanation is considering the
existence of flavor changing Z' couplings to the b and s quarks which can
contribute to the off-diagonal decay width in the B_s - \bar{B}_s mixing. Model
construction is highly constrained by the recent LHCb data of 1fb^{-1}
integrated luminosity . In this paper, we analyze the experimental constraints
in constructing new physics models to explain the dimuon charge asymmetry from
the CP violation of the B_s system. We present limits on Z' couplings and show
that it is impossible to obtain the 1\sigma range of the dimuon charge
asymmetry without the new contribution in the B_d system. Even with arbitrary
contribution in the B_d system, the new couplings must be in the fine tuned
region.Comment: 34 pages, 12 figures, Additional analyses and references are updated.
(Conclusion unchanged.
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