19,654 research outputs found
Branching ratios and asymmetries of decays
We investigate the exclusive nonleptonic decays in the conventional perturbative QCD (PQCD) formalism. The
predictions of branching ratios and asymmetries are given in detail. We
compare our results with available experimental data as well as predictions of
other theoretical studies existing in the literature. It seems that the
branching ratios of are more consistent with data
than the earlier analyses. For the Cabibbo-suppressed decay, the
branching ratio can reach the order of , which would be straight
forward for experimental observations. The numerical results show that the
direct asymmetries of the concerned decays are rather small. The
mixing-induced asymmetry in the is very
close to , which suggests that this channel offer an alternative
method for measuring the Cabbibo-Kobayashi-Maskawa (CKM) angle . The
obtained results in the present work could be tested by further experiments in
the LHCb and forthcoming Belle II.Comment: 8 pages, 1 figur
Facility location with double-peaked preference
We study the problem of locating a single facility on a real line based on
the reports of self-interested agents, when agents have double-peaked
preferences, with the peaks being on opposite sides of their locations. We
observe that double-peaked preferences capture real-life scenarios and thus
complement the well-studied notion of single-peaked preferences. We mainly
focus on the case where peaks are equidistant from the agents' locations and
discuss how our results extend to more general settings. We show that most of
the results for single-peaked preferences do not directly apply to this
setting; this makes the problem essentially more challenging. As our main
contribution, we present a simple truthful-in-expectation mechanism that
achieves an approximation ratio of 1+b/c for both the social and the maximum
cost, where b is the distance of the agent from the peak and c is the minimum
cost of an agent. For the latter case, we provide a 3/2 lower bound on the
approximation ratio of any truthful-in-expectation mechanism. We also study
deterministic mechanisms under some natural conditions, proving lower bounds
and approximation guarantees. We prove that among a large class of reasonable
mechanisms, there is no deterministic mechanism that outperforms our
truthful-in-expectation mechanism
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
- β¦