4,382 research outputs found
Revisiting B\to\pi K, \pi K^{\ast} and \rho K decays: CP violations and implication for New Physics
Combining the up-to-date experimental information on and decays, we revisit the decay rates and CP asymmetries of
these decays within the framework of QCD factorization. Using an infrared
finite gluon propagator of Cornwall prescription, we find that the time-like
annihilation amplitude could contribute a large strong phase, while the
space-like hard spectator scattering amplitude is real. Numerically, we find
that all the branching ratios and most of the direct CP violations, except
, agree with the current experimental data
with an effective gluon mass . Taking the unmatched
difference in direct CP violations between and
decays as a hint of new physics, we perform a
model-independent analysis of new physics contributions with a set of
(q=u,d) operators. Detail
analyses of the relative impacts of the operators are presented in five cases.
Fitting the twelve decay modes, parameter spaces are found generally with
nontrivial weak phases. Our results may indicate that both strong phase from
annihilation amplitude and new weak phase from new physics are needed to
resolve the puzzle. To further test the new physics hypothesis, the
mixing-induced CP violations in and are
discussed and good agreements with the recent experimental data are found.Comment: Version published in JHE
decay in scalar and vector leptoquark scenarios
It has been shown that the anomalies observed in and decays can be
resolved by adding a single scalar or vector leptoquark to the Standard Model,
while constraints from other precision measurements in the flavour sector can
be satisfied without fine-tuning. To further explore these two interesting
scenarios, in this paper, we study their effects in the semi-leptonic
decay. Using the best-fit solutions for
the operator coefficients allowed by the current data of mesonic decays, we
find that (i) the two scenarios give similar amounts of enhancements to the
branching fraction and the
ratio , (ii) the
two best-fit solutions in each of these two scenarios are also
indistinguishable from each other, (iii) both scenarios give nearly the same
predictions as those of the Standard Model for the longitudinal polarizations
of and as well as the lepton-side forward-backward
asymmetry. With future measurements of these observables in
decay at the LHCb, the two leptoquark
scenarios could be further tested, and even differentiated from the other NP
explanations for the anomalies. We also discuss the
feasibility for the measurements of these observables at the LHC and the future
colliders.Comment: 29 pages, 4 tables and 2 figures; More references and the feasibility
for the measurements of the observables in these decays at the LHC and the
future colliders added, final version published in the journa
Transitions in the Standard Model Effective Field Theory
The anomalies observed in decays
have attracted much attention in recent years. In this paper, we study the
, , , , and decays, all
being mediated by the same quark-level transition, in the
Standard Model Effective Field Theory. The most relevant dimension-six
operators for these processes are , , ,
and in the Warsaw basis. Evolution of the corresponding Wilson
coefficients from the new physics scale ~TeV down to the
characteristic scale is performed at three-loop in QCD and
one-loop in EW/QED. It is found that, after taking into account the constraint
, a single
or
can still be used to resolve the
anomalies at , while a single
is already ruled out by the
measured at more than . By minimizing the
function constructed based on the current data on ,
, , , and , we obtain eleven most
trustworthy scenarios, each of which can provide a good explanation of the
anomalies at . To further discriminate these different
scenarios, we predict thirty-one observables associated with the processes
considered under each NP scenario. It is found that most of the scenarios can
be differentiated from each other by using these observables and their
correlations.Comment: 43 pages, 3 figures and 5 tables; references updated and more
discussions added, final version to be published in the journa
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