232 research outputs found
Connecting anomalies to enhanced rare nonleptonic decays in model
The present data on a number of observables in processes
manifest some tensions with the standard model (SM). Assuming that these
anomalies have a new physics origin, we consider the possibility that a
boson is responsible for them. We further assume that its interactions with
quarks also affect rare nonleptonic decays of the meson which are
purely isospin-violating and tend to be dominated by electroweak-penguin
contributions, namely . Most of
these decays are not yet observed, and their rates are expected to be
relatively small in the SM. Taking into account constraints from various
measurements, including the evidence for recently
seen by LHCb, we find that the effects on
can make their rates bigger than the SM predictions by up to an order of
magnitude. For , the enhancement
factors are at most a few. Since the contributions to the different
channels depend on different combinations of its couplings, observations of
more of these decays in future experiments, along with improved data, will probe this scenario more thoroughly.Comment: 17 pages, 4 figures, somewhat revised, comments & references added,
matches publicatio
Flavor-Changing Higgs Decays in Grand Unification with Minimal Flavor Violation
We consider the flavor-changing decays of the Higgs boson in a grand unified
theory framework which is based on the SU(5) gauge group and implements the
principle of minimal flavor violation. This allows us to explore the
possibility of connecting the tentative hint of the Higgs decay
recently reported in the CMS experiment to potential new physics in the quark
sector. We look at different simple scenarios with minimal flavor violation in
this context and how they are subject to various empirical restrictions. In one
specific case, the relative strengths of the flavor-changing leptonic Higgs
couplings are determined mainly by the known quark mixing parameters and
masses, and a branching fraction is achievable
without the couplings being incompatible with the relevant constraints.
Upcoming data on the Higgs leptonic decays and searches for the decay with improved precision can offer further tests on this
scenario.Comment: 18 pages, 2 figures, somewhat expanded, references added, main
conclusions unchanged, matches published versio
Minimal Lepton Flavor Violation Implications of the Anomalies
The latest measurements of rare decays in the LHCb experiment have
led to results in tension with the predictions of the standard model (SM),
including a tentative indication of the violation of lepton flavor
universality. Assuming that this situation will persist because of new physics,
we explore some of the potential consequences in the context of the SM extended
with the seesaw mechanism involving right-handed neutrinos plus effective
dimension-six lepton-quark operators under the framework of minimal flavor
violation. We focus on a couple of such operators which can accommodate the
LHCb anomalies and conform to the minimal flavor violation hypothesis in both
their lepton and quark parts. We examine specifically the
lepton-flavor-violating decays , ,
, and , as well as
and , induced by such operators. The estimated branching
fractions of some of these decay modes with in the final states are
allowed by the pertinent experimental constraints to reach a few times
if other operators do not yield competitive effects. We also look at
the implications for and , finding that
their rates can be a few times larger than their SM values. These results are
testable in future experiments.Comment: 16 pages, no figures, clarifying comments added, references updated,
matches journal versio
Constraints on a New Light Spin-One Particle from Rare b -> s Transitions
The anomalously large like-sign dimuon charge asymmetry in semileptonic
b-hadron decays recently measured by the D0 Collaboration may be hinting at the
presence of CP-violating new physics in the mixing of B_s mesons. It has been
suggested that the effect of a nonstandard spin-1 particle lighter than the b
quark with flavor-changing couplings to b and s quarks can reproduce the D0
result within its one-sigma range. Here we explore the possibility that the new
particle also couples to charged leptons l=e,mu and thus contributes to rare b
-> s processes involving the leptons. We consider in particular constraints on
its couplings from existing experimental data on the inclusive B -> X_s l^+ l^-
and exclusive B -> K^{(*)} l^+ l^- decays, as well as the anomalous magnetic
moments of the leptons. We find that there is parameter space of the particle
that is allowed by the current data. Future measurements of these B transitions
and rare decays of the B_s meson, such as B_s -> (phi,eta,eta') l^+ l^- and B_s
-> l^+ l^-, at LHCb and next-generation B factories can probe its presence or
couplings more stringently.Comment: 19 pages, 5 figure
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