Abstract

Abstract: We calculate QED corrections to the semileptonic decays H1 → H2ℓ +ℓ − where ℓ = e, µ and H1,2 are hadrons. The soft and/or collinear divergences are regulated in a gauge-invariant manner and demonstrably cancel, leaving behind a finite residue that depends on the (infrared) momentum cutoff below which a photon is considered to be indistinguishable. On resuming, the said sensitivity reduces drastically, i.e., for the NLL result as compared to the NLO one. The overall correction is negative and its magnitude is larger for a lighter lepton. For B → K(∗) decays, the corrections improve the agreement for the differential distributions, while the behavior is more complicated for Λb → Λ (∗) decays. Rather intriguingly, the corrections serve to regenerate the tension for the lepton flavor universality observables RK and RK∗ .

Abstract

We investigate the possible sizes of all the CP-violating asymmetries offered by the angular distribution of rare decay Λb → Λð→ pπ−Þlþl− in the Standard Model and new physics scenarios motivated by the recent b → slþl− anomalies. We work in a model-independent effective theory framework and discuss the sensitivity of CP asymmetries to new O9;10 operators and their chirality flipped counterparts. We find that the size of many of the CP asymmetries can be at the level of a few percent in new physics scenarios consistent with current b → slþl− data at a level of 1σ. We emphasize that measurements of these CP asymmetries can be used to discriminate different new physics scenarios in b → slþl−.

Abstract

We determine the strange quark mass ( � � ) and quark mixing element | � � � | , and their joint determination from the Cabibbo suppressed hadronic � decays in various perturbative schemes. We improve this analysis compared to the previous analysis based on the optimal renormalization or the renormalization group summed perturbation theory (RGSPT) scheme by replacing the theoretical longitudinal contributions with phenomenological parametrization; the RGSPT coefficients are used for the dimension-4 Adler functions. The improved analysis results in the extraction of � � ( 2     GeV ) = 98 ± 19   MeV and | � � � | = 0.2191 ± 0.0043 from the RGSPT scheme

Abstract

We investigate the possible sizes of all the CP-violating asymmetries offered by the angular distribution of rare decay Λb → Λ(→ pπ−)` +` − in the Standard Model and new physics scenarios motivated by the recent b → s`+` − anomalies. We work in a model-independent effective theory framework and discuss the sensitivity of CP asymmetries to new O9,10 operators and their chirality flipped counterparts. We find that the size of many of the CP asymmetries can be at the level of few percent in new physics scenarios consistent with current b → s`+` − data at level of 1σ. We emphasize that measurements of these CP asymmetries can be used to discriminate different new physics scenarios in b → s`+` −.

Abstract

We discuss the prospects for improving the precision on the hadronic corrections to the anomalous magnetic moment of the muon, and the plans of the Muon g −2 Theory Initiative to update the Standard Model prediction.

Abstract

We study lepton number violating and lepton number conserving semileptonic decays of heavy baryons Λ0 b to three charged leptons and a neutrino. The decays occur through two intermediate quasidegenerate GeV-scale sterile neutrinos of either Majorana or Dirac type that can be on-shell. Interference between the intermediate heavy neutrinos leads to CP violation in the final states. Effect of neutrino oscillations between the heavy states are also considered in observables of interests, i.e., branching ratio, and the CP-asymmetry. Given the present constraints on the heavy-to-light mixing elements jVeNj and jVμNj, CP-averaged branching ratio of Λ0 b → ðΛc; pÞμμeν with intermediate Majorana neutrinos is almost two orders of magnitude larger than for the same with Dirac neutrinos, whereas, CP-averaged branching ratio of Λ0 b → ðΛc; pÞeeμν is of the same order of magnitude for both Majorana and Dirac neutrino induced decays. CP-violation is found to be appreciable when the neutrino mass difference is comparable with the average decay widths.

Abstract

The U1 leptoquark is known to be a suitable candidate for explaining the semileptonic B-decay anomalies. We derive precise limits on its parameter space relevant for the anomalies from the current LHC high-pT dilepton data. We consider an exhaustive list of possible B-anomalies-motivated simple scenarios with one or two new couplings that can also be used as templates for obtaining bounds on more complicated scenarios. To obtain precise limits, we systematically consider all possible U1 production processes that can contribute to the dilepton searches, including the resonant pair and single productions, nonresonant t-channel U1 exchange, as well as its large interference with the Standard Model background. We demonstrate how the inclusion of resonant production contributions in the dilepton signal can lead to appreciably improved exclusion limits. We point out new search channels of U1 that can act as unique tests of the flavour-motivated models. The template scenarios can also be used for future U1 searches at the LHC. We compare the LHC limits with other relevant flavour bounds and find that a TeV-scale U1 can accommodate both RD(∗) and RK(∗) anomalies while satisfying all the bounds.

Abstract

The U1 leptoquark is known to be a suitable candidate for explaining the semileptonic B-decay anomalies. We derive precise limits on its parameter space relevant for the anomalies from the current LHC high-pT dilepton data. We consider an exhaustive list of possible B-anomalies-motivated simple scenarios with one or two new couplings that can also be used as templates for obtaining bounds on more complicated scenarios. To obtain precise limits, we systematically consider all possible U1 production processes that can contribute to the dilepton searches, including the resonant pair and single productions, nonresonant t-channel U1 exchange, as well as its large interference with the Standard Model background. We demonstrate how the inclusion of resonant production contributions in the dilepton signal can lead to appreciably improved exclusion limits. We point out new search channels of U1 that can act as unique tests of the flavor-motivated models. The template scenarios can also be used for future U1 searches at the LHC. We compare the LHC limits with other relevant flavor bounds and find that a TeV-scale U1 can accommodate both RDðÞ and RKðÞ anomalies while satisfying all the bounds.

Abstract

We explore the possibility of CP violation in baryonic Λb → ðΛþ c ; pþÞπþμ−μ− decays which are mediated by two Majorana sterile neutrinos and are jΔLj ¼ 2 lepton-number-violating processes. Appreciable CP asymmetry can be obtained if there are two on-shell Majorana neutrinos that are quasidegenerate in mass with the mass difference of the order of average decay widths. We find that, given the present constraints on the heavy to light mixing element jVμNj, the Λb → pþπþμ−μ− and Λb → Λþ c πþμ−μ− decay rates are suppressed but could be within the experimental reach at the LHC. If searches of the modes are performed, then experimental limits on the rates can be translated to constraints on the Majorana neutrino mass mN and heavy to light mixing element squared jVμNj 2. We show that the constraints on the ðmN; jVμNj 2Þ parameter space coming from the jΔLj ¼ 2 baryonic decays are complementary to the bounds coming from other processes.

Abstract

The recent anomalies in b → slþl− transitions could originate from some new physics beyond the Standard Model. Either to confirm or to rule out this assumption, more tests of b → slþl− transition are needed. Polarized Λb decay to a Λ and a dilepton pair offers a plethora of observables that are suitable to discriminate new physics from the Standard Model. In this paper, we present a full angular analysis of a polarized Λb decay to a Λð→ pπÞlþl− final state. The study is performed in a set of the operator where the Standard Model operator basis is supplemented with its chirality flipped counterparts, and new scalar and pseudoscalar operators. The full angular distribution is calculated by retaining the mass of the final state leptons. At the low hadronic recoil, we use the heavy quark effective theory framework to relate the hadronic form factors which lead to simplified expression of the angular observables where short- and longdistance physics factorize. Using the factorized expressions of the observables, we construct a number of test of short- and long-distance physics including null tests of the Standard Model and its chirality flipped counterparts that can be carried out using experimental data.