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 prop...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.展开更多
The spectroscopic parameters and decay channels of the axial-vector tetraquark Tho(in what follows,TAV)are explored using the quantum chromodynamics(QCD)sum rule method.The mass and coupling of this state are calculat...The spectroscopic parameters and decay channels of the axial-vector tetraquark Tho(in what follows,TAV)are explored using the quantum chromodynamics(QCD)sum rule method.The mass and coupling of this state are calculated using two-point sum rules by taking into account various vacuum condensates,up to 10 dimensions.Our prediction for the mass of this state m=(10215±250)MeV confirms that it is stable with respect to strong and electromagnetic decays and can dissociate to conventional mesons only via weak transformations.We investigate the dominant semileptonic■and nonleptonic T AV b:s^-→v10 b:s^-M decays of T AV b:s^-.In these processes,Z-b:s^-is a scalar tetraquark[be][us^-]built of a colo-triplet diquark and an antidiquark,whereas M is one of the vector mesonsρ^-,K^*(892),D^*(2010)^-,and D^*s-.To caleulate the partial w idths of these decays,we use the QCD three-point sum rule approach and evaluate the weak transition form factors Gi(i=0,1,2,3),which govem these processes.The full widthΓfull=(12.9±2.1)×10^-8 MeV and the mean lifetimeτ=5.1+0.99-0.71 fs of the tetraquark TAV are computed us-ing the aforementioned weak decays.The obtained information about the parametersof TAY and Zh,is useful for experimental investigations of these double-heavy exotic mesons.展开更多
We present an analysis of the newly observed pentaquark P(4312)+to shed light on its quantum num-bers.To do that,the QCD sum rules approach is used.The measured mass of this particle is close to the∑++cD-threshold an...We present an analysis of the newly observed pentaquark P(4312)+to shed light on its quantum num-bers.To do that,the QCD sum rules approach is used.The measured mass of this particle is close to the∑++cD-threshold and has a small width,which supports the possibility of its being a molecular state.We consider an inter-polating current in a molecular form and analyze both the positive and negative parity states with spin-1/2.We also consider the bottom counterpart of the state with similar molecular form.Our mass result for the charm pentaquark state supports that the quantum numbers of the observed state are consistent with J^(P)=1/2^(-).展开更多
The strong coupling constants are basic quantities that carry information on the strong interactions among the baryon and meson multiplets as well as information on the nature and internal structures of the involved h...The strong coupling constants are basic quantities that carry information on the strong interactions among the baryon and meson multiplets as well as information on the nature and internal structures of the involved hadrons.These parameters are introduced in the transition matrix elements of various decays as main inputs and play key roles in analyses of experimental data including various hadrons.We derive the strong coupling constants among the doubly heavy spin-baryons,and,and light pseudoscalar mesons,π,K,andη,using the light-cone QCD.The values obtained for these constants under study may be used to construct the strong potentials among the doubly heavy spin-3/2 baryons and light pseudoscalar mesons.展开更多
The strong coupling constants of hadronic multiplets are fundamental parameters which carry information about the strong interactions among participating particles.These parameters can help us construct the hadron-had...The strong coupling constants of hadronic multiplets are fundamental parameters which carry information about the strong interactions among participating particles.These parameters can help us construct the hadron-hadron strong potential and gain information about the structure of the involved hadrons.Motivated by the recent observation of the doubly charmed cc state by LHCb,we determine the strong coupling constants among the doubly heavy spin-1/2 baryons, Ξ_(QQ′)/(′),Ω_(QQ′)/(′) and light pseudoscalar mesons,π,κ,η and η′within the framework of the light cone QCD sum rules.The obtained results may help experimental groups in analysis of the related data at hadron colliders.展开更多
文摘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.
基金The work of K.A.B.B..and H.S was Supported in part by the TUBITAK(119F050)。
文摘The spectroscopic parameters and decay channels of the axial-vector tetraquark Tho(in what follows,TAV)are explored using the quantum chromodynamics(QCD)sum rule method.The mass and coupling of this state are calculated using two-point sum rules by taking into account various vacuum condensates,up to 10 dimensions.Our prediction for the mass of this state m=(10215±250)MeV confirms that it is stable with respect to strong and electromagnetic decays and can dissociate to conventional mesons only via weak transformations.We investigate the dominant semileptonic■and nonleptonic T AV b:s^-→v10 b:s^-M decays of T AV b:s^-.In these processes,Z-b:s^-is a scalar tetraquark[be][us^-]built of a colo-triplet diquark and an antidiquark,whereas M is one of the vector mesonsρ^-,K^*(892),D^*(2010)^-,and D^*s-.To caleulate the partial w idths of these decays,we use the QCD three-point sum rule approach and evaluate the weak transition form factors Gi(i=0,1,2,3),which govem these processes.The full widthΓfull=(12.9±2.1)×10^-8 MeV and the mean lifetimeτ=5.1+0.99-0.71 fs of the tetraquark TAV are computed us-ing the aforementioned weak decays.The obtained information about the parametersof TAY and Zh,is useful for experimental investigations of these double-heavy exotic mesons.
文摘We present an analysis of the newly observed pentaquark P(4312)+to shed light on its quantum num-bers.To do that,the QCD sum rules approach is used.The measured mass of this particle is close to the∑++cD-threshold and has a small width,which supports the possibility of its being a molecular state.We consider an inter-polating current in a molecular form and analyze both the positive and negative parity states with spin-1/2.We also consider the bottom counterpart of the state with similar molecular form.Our mass result for the charm pentaquark state supports that the quantum numbers of the observed state are consistent with J^(P)=1/2^(-).
文摘The strong coupling constants are basic quantities that carry information on the strong interactions among the baryon and meson multiplets as well as information on the nature and internal structures of the involved hadrons.These parameters are introduced in the transition matrix elements of various decays as main inputs and play key roles in analyses of experimental data including various hadrons.We derive the strong coupling constants among the doubly heavy spin-baryons,and,and light pseudoscalar mesons,π,K,andη,using the light-cone QCD.The values obtained for these constants under study may be used to construct the strong potentials among the doubly heavy spin-3/2 baryons and light pseudoscalar mesons.
文摘The strong coupling constants of hadronic multiplets are fundamental parameters which carry information about the strong interactions among participating particles.These parameters can help us construct the hadron-hadron strong potential and gain information about the structure of the involved hadrons.Motivated by the recent observation of the doubly charmed cc state by LHCb,we determine the strong coupling constants among the doubly heavy spin-1/2 baryons, Ξ_(QQ′)/(′),Ω_(QQ′)/(′) and light pseudoscalar mesons,π,κ,η and η′within the framework of the light cone QCD sum rules.The obtained results may help experimental groups in analysis of the related data at hadron colliders.
