Constraints on the First Generation Scalar Leptoquarks

Inspired by the CMS excess in eejj and evjj channels and possible interpretation using the first generation scalar leptoquarks （SLQs）, we consider their contributions to non-standard neutrino interaction and the pion meson Ieptonic decay π→lv. Compared with the relevant experimental data, the constraints on the first generation SLQs are obtained. Their corrections to the anomalous magnetic moment aμ are further calculated and the numerical results show that it is possible to explain the deviation from its standard model prediction.

Effects of vector leptoquarks onΛb→Λ,lv^-l decay

Experimental data on R(D^(+)).R(K^(+)),and R(J/ψ),provided by different collaborations,show sizable deviations from the standard model predictions.To describe these anomalies,many new physics scenarios have been proposed.One of them is the leptoquark model,which introduces the simultaneous coupling of vector and scalar leptoquarks to quarks and leptons.To look for similar possible anomalies in the baryonic sector,we investigate the effects of a vector leptoquark U3(3,3,2/3)on various physical quantities related to the tree-levelΛb→Λclv^-l decays(l=u,t),which proceed via b→c l v^-l transiti ons at the quark level.We calculate the differential branching ratio,forward-backward asymmetry,and longitudinal polarizations of leptons and Ac baryons at theμandτlepton channels in the leptoquark model and compare their behavior to the predictions of the SM in terms of q^2.In the calculations,we use the form factors calculated in full QCD as the main input and account for all errors coming from the form factors and model parameters.We observe that at theτchanneL the Ra fit solution to data related to the leptoquark model sweeps some regions out of the SM band;nevertheless,the fit has a considerable intersection with the SM predictions.The Rr type solution gives roughly the same results as the SM on DBR(q^2)-q^2.At theμchannel.the leptoquark model gives results that are consistent with the SM predictions and existing experimental data on the behavior of DBR(q^2)with respect to q^2.Concerning the q^2 behavior of the AFB(q^2),the two types of fits forτand the predictions at the“channel in the leptoquark model give exactly the same results as the SM.We also investigate the behavior of the parameter R(q^2)with respect to q^2 and the value of R(Λc)in both the vector leptoquark and SM models.Both fit solutions lead to results that deviate considerably from the SM predictions for R(q^2)-q^2 and R(Ac).Future experimental data on R(q^2)-q^2 and RC made available by measurements of theΛb→Λcτv^-τchannel,will be particularly helpful.Any experimental deviations from the SM predictions in this channel would emphasize the im porta nee of tree-level hadronic weak tran sitions as good probes of new physics effects beyond the SM.

Model dependent analysis of D^(+)_(s)→η^(′)l+v_(l) decays in beyond standard model

Motivated by the recent experimental results of branching fractions for D^(+)_(s)→η^(′)l+v_(l) decays,which deviate from their SM predictions,we hve investigated these decays in W' model and scalar leptoquark model to determine potential signatures of new physics(NP) in semileptonic charm decays induced by c→(s,d)l+v_(l) transitions.Using recent experimental results of branching fractions for semileptonic D meson decays,new coupling parameters are predicted for the aforementioned NP models.Branching fraction,forward-backward asymmetry,and lepton polarization asymmetry are examined by considering the predicted NP coupling parameters.The results of branching fractions in scalar leptoquark model are found very close to the experimental results and exist around the range of 1σ deviation.We presented a comparative study of the NP models to check their sensitivity on these decays.We anticipate that further research on these decays will significantly support our findings.

Results on non-SUSY searches for physics beyond standard model in pp collisions at CMS

In this paper a review of the results on searches for pnysics beyond the standard model in pp collisions with the CMS experiment at √s = 7 and 8 TeV is presented. Aspects of the analyses and their achieved limits on Z′- and W′-bosons, heavy neutrino, 4^th generation, leptoquarks as well as extra dimensions will be covered.

Phenomenology of b→cτ■ decays in a scalar leptoquark model

During the past few years,signs of lepton flavor universality(LFU)violation have been observed in b→cτ■ and b→sl+l-transitions.Recently,the D* and τ polarization fractions P_L^D* and P_L~τ in B→D*τ■decay were likewise measured by the Belle collaboration.Motivated by these intriguing results,we revisit the RD(*)and RK(*) anomalies in a scalar leptoquark(LQ)model,where two scalar LQs,one of which is a S U(2)L singlet and the other a S U(2)L triplet,are introduced simultaneously.We consider five b→ cτ■ mediated decays,B→D(*)τ■,B^c→ηcτ■,Bc→J/ψt■,and ∧_b→∧_cτ■,and focus on the LQ effects on the q^2 distributions of the branching fractions,LFU ratios,and various angular observables in these decays.Under the combined constraints of the available data on RD(*),RJ/ψ,P_L~τ(D*),and pLD*,we perform scans for the LQ couplings and make predictions for a number of observables.Numerically it is found that both the differential branching fractions and LFU ratios are largely enhanced by the LQ effects,with the latter expected to provide testable signatures at the SuperKEKB and High-Luminosity LHC experiments.

Leptoquark and vector-like quark extended model for simultaneous explanation of W boson mass and muon g–2 anomalies

The CDF collaboration recently announced a new measurement result for the W boson mass,and it is in tension with the standard model prediction.In this paper,we explain this anomaly in the vector-like quark(VLQ)(X,T,B)_(L,R)and leptoquark(LQ)S_(3)extended model.In this model,both the VLQ and LQ have positive corrections to the W boson mass.Moreover,it may be a solution to the(g-2)_(μ)anomaly because of the chiral enhancements from top,T,and B quarks.

Scalar leptoquark and vector-like quark extended models as the explanation of the muon g-2 anomaly:bottom partner chiral enhancement case

Leptoquark(LQ)models are well motivated solutions to the(g-2)_(μ)anomaly.In the minimal LQ models,only specific representations can lead to chiral enhancements.For the scalar LQs,R_(2)and S_(1)can lead to the top quark chiral enhancement.For the vector LQs,V_(2)and U_(1)can lead to the bottom quark chiral enhancement.When we consider the LQ and vector-like quark(VLQ)simultaneously,there can be more scenarios.In our previous study,we considered the scalar LQ and VLQ extended models with up-type quark chiral enhancement.Here,we study the scalar LQ and VLQ extended models with down-type quark chiral enhancement.We find two new models with B quark chiral enhancements,which originate from the bottom and bottom partner mixing.Then,we propose new LQ and VLQ search channels under the constraints of(g-2)_(μ).