We study two-body B（c）→Mc（π,K） and semileptonic Bc→Mcl^-v^-1 decays with Mc=（J/φ,Xc^0）,where Xc^0=X^0（3872） is regarded as the tetraquark state ccuu（dd）.With the decay constant fxc^0=（234±52） MeV ...We study two-body B（c）→Mc（π,K） and semileptonic Bc→Mcl^-v^-1 decays with Mc=（J/φ,Xc^0）,where Xc^0=X^0（3872） is regarded as the tetraquark state ccuu（dd）.With the decay constant fxc^0=（234±52） MeV determined from the data,we predict that B（B^-→Xc^0π^-） =（11.5±5.7）×10^-6,B（B^0→Xc^0K^-0）=（2.1±1.0）×10^-4,and B（Bs^0→Xc^0K^0）=（11.4±5.6）×10^-6.With the form factors in QCD models,we calculate that B（Bc^-→Xc^0π^-,Xc^0K^-）=（6.0±2.6）×10^-5 and（4.7±2.0）×10^-6,and B（Bc^-→J/φμ^-vμ^-vμ,Xc^0μ^-v^-μ）=（2.3±0.6）×10^-2 and（1.35±0.18）×10^-3,respectively,and extract the ratio of the fragmentation fractions to be fc/fu=（6.4±1.9）×10^-3.展开更多
The universality of the weak interactions can be tested in semileptonic b→c transitions,and in particular in the ratios R（D＊） ≡ Γ（B → D（＊）τν）/Γ（B → D＊lν）（where 1 = μ or e）.Due to the recent diff...The universality of the weak interactions can be tested in semileptonic b→c transitions,and in particular in the ratios R（D＊） ≡ Γ（B → D（＊）τν）/Γ（B → D＊lν）（where 1 = μ or e）.Due to the recent differences between the experimental measurements of these observables by Ba Bar,Belle and LHCb on the one hand and the Standard Model predicted values on the other hand,we study the predicted ratios R（D＊）=Γ（B→D＊τ＋＂missing＂）/Γ（B→D（＊）lν）in scenarios with an additional sterile heavy neutrino of mass ～1 Ge V.Further,we evaluate the newly defined ratio R（0）≡Γ（B→τ＋＂missing＂）/Γ（B→μν） in such scenarios,in view of the future possibilities of measuring the quantity at Belle-Ⅱ.展开更多
In this paper,we study the B→D^(*) l-l -ι semileptonic decays and calculate the branching ratios B(B→D^(*) l-l -ι) and the ratios R(D^(*)) and R_D^( l,s) by employing the perturbative QCD(pQCD)factorization appro...In this paper,we study the B→D^(*) l-l -ι semileptonic decays and calculate the branching ratios B(B→D^(*) l-l -ι) and the ratios R(D^(*)) and R_D^( l,s) by employing the perturbative QCD(pQCD)factorization approach.We find that(a)for R(D)and R(D*)ratios,the pQCD predictions are R(D)=0.430-0.026?0.021,R(D*)=0.301±0.013 and agree well with BaBar’s measurements of ReD e?T T;(b)for the newly defined R_D^1 and R_D^s ratios,the pQCD predictions are R_D^l=0.450-0.051+0.064 and R_D^s=0.642-0.070+0.081,which may be more sensitive to the QCD dynamics of the considered semileptonic decays than R(D^(*)) and should be tested by experimental measurements.展开更多
By employing the perturbative QCD （pQCD） factorization approach, we calculate the new physics contributions to the four B→Kη（＇） decays in the Standard Model （SM） with a fourth generation of fermions （SM4）, ...By employing the perturbative QCD （pQCD） factorization approach, we calculate the new physics contributions to the four B→Kη（＇） decays in the Standard Model （SM） with a fourth generation of fermions （SM4）, induced by the loop diagrams involving t＇ quark. Within the considered parameter space of the SM4 we find that： （a） the next-to-leading order （NLO） pQCD predictions for the branching ratios and CP-violating asymmetries in both the SM and SM4 generally agree with the data within one standard deviation; （b） for Br（B→Kη）, the inclusion of the fourth generation contributions can improve the agreement between the theoretical predictions and the data effectively; （c） however, for Br（B→Kη＇） the decrease due to t＇ loops is disfavored by the data; and, （d） the new physics corrections to the CP-violating asymmetries of the considered decays are only about 10%.展开更多
Over the last few years LHCb found some discrepancies in b → sl^＋l^-FCNC transitions, including anomalies in the angular observables of B→K^＊μ^＋μ^-, particularly in P′5, in the low dimuon mass region. Recently...Over the last few years LHCb found some discrepancies in b → sl^＋l^-FCNC transitions, including anomalies in the angular observables of B→K^＊μ^＋μ^-, particularly in P′5, in the low dimuon mass region. Recently,these anomalies have been confirmed by Belle, CMS and ATLAS. As direct evidence of physics beyond the Standard Model is absent so far, these anomalies are being interpreted as indirect hints of new physics. In this context, we study the implications of the family non-universal Z′ model for the angular observables P（1,2,3）, P′（4,5,6） and newly proposed lepton flavor universality violation observables, Q（4,5）, in the B → K^＊（→Kπ）μ^＋μ^-decay channel in the low dimuon mass region. To see the variation in the values of these observables from their Standard Model values, we have chosen different scenarios for the Z′ model. It is found that these angular observables are sensitive to the values of the parameters of the Z′ model. We have also found that with the present parametric space of the Z′ model,the P′5-anomaly could be accommodated. However, more statistics on the anomalies in the angular observables are helpful to reveal the status of the considered model and, in general, the nature of new physics.展开更多
In this paper,we calculated the branching ratios and direct CP violation of the four B→Kπ decays with the inclusion of all currently known next-to-leading order（NLO） contributions by employing the perturbative QCD...In this paper,we calculated the branching ratios and direct CP violation of the four B→Kπ decays with the inclusion of all currently known next-to-leading order（NLO） contributions by employing the perturbative QCD（pQCD） factorization approach.We found that（a） Besides the 10%enhancement from the NLO vertex corrections,the quark-loops and magnetic penguins,the NLO contributions to the form factors can provide an additional^15%enhancement to the branching ratios,and lead to a very good agreement with the data;（b） The NLO pQCD predictions are A_（CP）^（dir）（B^0→K~＋π~0）=（-6.5±3.1）%and A_（CP）^（dir）（B~＋→K~＋π~0）=（2.2±2.0）%,become well consistent with the data due to the inclusion of the NLO contributions.展开更多
We know that our Universe is composed of only - 4.5% ＂known＂ matter; therefore, our understanding is incomplete. This can be seen directly in the case of neutrino oscillations （without even considering potential ot...We know that our Universe is composed of only - 4.5% ＂known＂ matter; therefore, our understanding is incomplete. This can be seen directly in the case of neutrino oscillations （without even considering potential other universes）. Charm quarks have had considerable impact on our under- standing of known matter, and quantum chromodynamics （QCD） is the only local quantum field theory to describe strong forces. It is possible to learn novel lessons concerning strong dynamics by measuring rates around the thresholds of [Q^-Q] states with Q = b, c. Furthermore, these states provide us with gateways towards new dynamics （ND）, where we must transition from ＂accuracy＂ to ＂precision＂ eras. Finally, we can make connections with τ transitions and, perhaps, with dark matter. Charm dynamics acts as a bridge between the worlds of light- and heavy-flavor hadrons （namely, beauty hadrons）, and finding regional asymmetries in many-body final states may prove to be a ＂game changer＂. There are several different approaches to achieving these goals： for exam- ple, experiments such as the Super Tau-Charm Factory, Super Beauty Factory, and the Super Z~ Factory act as gatekeepers - and deeper thinking regarding symmetries.展开更多
基金Supported in part by National Center for Theoretical Sciences,National Science Council(NSC-101-2112-M-007-006-MY3)MoST(Mo ST-104-2112-M-007-003-MY3)National Science Foundation of China(11675030)
文摘We study two-body B（c）→Mc（π,K） and semileptonic Bc→Mcl^-v^-1 decays with Mc=（J/φ,Xc^0）,where Xc^0=X^0（3872） is regarded as the tetraquark state ccuu（dd）.With the decay constant fxc^0=（234±52） MeV determined from the data,we predict that B（B^-→Xc^0π^-） =（11.5±5.7）×10^-6,B（B^0→Xc^0K^-0）=（2.1±1.0）×10^-4,and B（Bs^0→Xc^0K^0）=（11.4±5.6）×10^-6.With the form factors in QCD models,we calculate that B（Bc^-→Xc^0π^-,Xc^0K^-）=（6.0±2.6）×10^-5 and（4.7±2.0）×10^-6,and B（Bc^-→J/φμ^-vμ^-vμ,Xc^0μ^-v^-μ）=（2.3±0.6）×10^-2 and（1.35±0.18）×10^-3,respectively,and extract the ratio of the fragmentation fractions to be fc/fu=（6.4±1.9）×10^-3.
基金support by FONDECYT(Chile)(1130599)supported in part by the NRF grant funded by the Korean government of the MEST(2016R1D1A1A02936965)
文摘The universality of the weak interactions can be tested in semileptonic b→c transitions,and in particular in the ratios R（D＊） ≡ Γ（B → D（＊）τν）/Γ（B → D＊lν）（where 1 = μ or e）.Due to the recent differences between the experimental measurements of these observables by Ba Bar,Belle and LHCb on the one hand and the Standard Model predicted values on the other hand,we study the predicted ratios R（D＊）=Γ（B→D＊τ＋＂missing＂）/Γ（B→D（＊）lν）in scenarios with an additional sterile heavy neutrino of mass ～1 Ge V.Further,we evaluate the newly defined ratio R（0）≡Γ（B→τ＋＂missing＂）/Γ（B→μν） in such scenarios,in view of the future possibilities of measuring the quantity at Belle-Ⅱ.
基金supported by the National Natural Science Foundation of China(10975074 and 11235005)
文摘In this paper,we study the B→D^(*) l-l -ι semileptonic decays and calculate the branching ratios B(B→D^(*) l-l -ι) and the ratios R(D^(*)) and R_D^( l,s) by employing the perturbative QCD(pQCD)factorization approach.We find that(a)for R(D)and R(D*)ratios,the pQCD predictions are R(D)=0.430-0.026?0.021,R(D*)=0.301±0.013 and agree well with BaBar’s measurements of ReD e?T T;(b)for the newly defined R_D^1 and R_D^s ratios,the pQCD predictions are R_D^l=0.450-0.051+0.064 and R_D^s=0.642-0.070+0.081,which may be more sensitive to the QCD dynamics of the considered semileptonic decays than R(D^(*)) and should be tested by experimental measurements.
基金Supported by National Natural Science Foundation of China(11235005)Project on Graduate Students Education and Innovation of Jiangsu Province(CXZZ13 0391)
文摘By employing the perturbative QCD （pQCD） factorization approach, we calculate the new physics contributions to the four B→Kη（＇） decays in the Standard Model （SM） with a fourth generation of fermions （SM4）, induced by the loop diagrams involving t＇ quark. Within the considered parameter space of the SM4 we find that： （a） the next-to-leading order （NLO） pQCD predictions for the branching ratios and CP-violating asymmetries in both the SM and SM4 generally agree with the data within one standard deviation; （b） for Br（B→Kη）, the inclusion of the fourth generation contributions can improve the agreement between the theoretical predictions and the data effectively; （c） however, for Br（B→Kη＇） the decrease due to t＇ loops is disfavored by the data; and, （d） the new physics corrections to the CP-violating asymmetries of the considered decays are only about 10%.
文摘Over the last few years LHCb found some discrepancies in b → sl^＋l^-FCNC transitions, including anomalies in the angular observables of B→K^＊μ^＋μ^-, particularly in P′5, in the low dimuon mass region. Recently,these anomalies have been confirmed by Belle, CMS and ATLAS. As direct evidence of physics beyond the Standard Model is absent so far, these anomalies are being interpreted as indirect hints of new physics. In this context, we study the implications of the family non-universal Z′ model for the angular observables P（1,2,3）, P′（4,5,6） and newly proposed lepton flavor universality violation observables, Q（4,5）, in the B → K^＊（→Kπ）μ^＋μ^-decay channel in the low dimuon mass region. To see the variation in the values of these observables from their Standard Model values, we have chosen different scenarios for the Z′ model. It is found that these angular observables are sensitive to the values of the parameters of the Z′ model. We have also found that with the present parametric space of the Z′ model,the P′5-anomaly could be accommodated. However, more statistics on the anomalies in the angular observables are helpful to reveal the status of the considered model and, in general, the nature of new physics.
基金Supported by National Natural Science Foundation of China(10975074,11235005)
文摘In this paper,we calculated the branching ratios and direct CP violation of the four B→Kπ decays with the inclusion of all currently known next-to-leading order（NLO） contributions by employing the perturbative QCD（pQCD） factorization approach.We found that（a） Besides the 10%enhancement from the NLO vertex corrections,the quark-loops and magnetic penguins,the NLO contributions to the form factors can provide an additional^15%enhancement to the branching ratios,and lead to a very good agreement with the data;（b） The NLO pQCD predictions are A_（CP）^（dir）（B^0→K~＋π~0）=（-6.5±3.1）%and A_（CP）^（dir）（B~＋→K~＋π~0）=（2.2±2.0）%,become well consistent with the data due to the inclusion of the NLO contributions.
文摘We know that our Universe is composed of only - 4.5% ＂known＂ matter; therefore, our understanding is incomplete. This can be seen directly in the case of neutrino oscillations （without even considering potential other universes）. Charm quarks have had considerable impact on our under- standing of known matter, and quantum chromodynamics （QCD） is the only local quantum field theory to describe strong forces. It is possible to learn novel lessons concerning strong dynamics by measuring rates around the thresholds of [Q^-Q] states with Q = b, c. Furthermore, these states provide us with gateways towards new dynamics （ND）, where we must transition from ＂accuracy＂ to ＂precision＂ eras. Finally, we can make connections with τ transitions and, perhaps, with dark matter. Charm dynamics acts as a bridge between the worlds of light- and heavy-flavor hadrons （namely, beauty hadrons）, and finding regional asymmetries in many-body final states may prove to be a ＂game changer＂. There are several different approaches to achieving these goals： for exam- ple, experiments such as the Super Tau-Charm Factory, Super Beauty Factory, and the Super Z~ Factory act as gatekeepers - and deeper thinking regarding symmetries.
