We obtain the integrand of full-color four-loop three-point form factor of the stress-tensor supermultiplet in N=4 SYM,based on the color-kinematics(CK)duality and generalized unitarity method.Our result not only mani...We obtain the integrand of full-color four-loop three-point form factor of the stress-tensor supermultiplet in N=4 SYM,based on the color-kinematics(CK)duality and generalized unitarity method.Our result not only manifests all dual Jacobi relations via CK duality but also contains 133 free parameters.This suggests the constructibility of the form factor at even higher loops via CK duality.We also find that the planar form factor has a hidden dual conformal symmetry in the lightlike limit of the operator momentum,which is checked up to four loops.展开更多
The periapsis shift of charged test particles in arbitrary static and spherically symmetric charged spacetimes are studied.Two perturbative methods,the near-circular approximation and post-Newtonian methods,are develo...The periapsis shift of charged test particles in arbitrary static and spherically symmetric charged spacetimes are studied.Two perturbative methods,the near-circular approximation and post-Newtonian methods,are developed and shown to be very accurate when the results are determined to high orders.The near-circular approximation method is more precise when eccentricity e of the orbit is small,whereas the post-Newtonian method is more effective when orbit semilatus rectum p is large.Results from these two methods are shown to agree when both e is small and p is large.These results are then applied to the Reissner-Nordström spacetime,the Einstein-Maxwell-dilation gravity,and a charged wormhole spacetime.The effects of various parameters on the periapsis shift,particularly that of the electrostatic interaction,are carefully studied.The periapsis shift data of the solar-Mercury are then used to constrain the charges of the Sun and Mercury,and the data of the Sgr A^(*)-S2 periapsis shift are used to determine,for the first time using this method,the constraints of the charges of Sgr A^(*)and S2.展开更多
The principle of maximum conformality(PMC)provides a systematic approach to solve the conventional renormalization scheme and scale ambiguities.Scale-fixed predictions of physical observables using the PMC are indepen...The principle of maximum conformality(PMC)provides a systematic approach to solve the conventional renormalization scheme and scale ambiguities.Scale-fixed predictions of physical observables using the PMC are independent of the choice of renormalization scheme–a key requirement for renormalization group invariance.In this paper,we derive new degeneracy relations based on the renormalization group equations that involve both the usualβ-function and the quark mass anomalous dimensionγm-function.These new degeneracy relations enable improved PMC scale-setting procedures for correct magnitudes of the strong coupling constant and MS¯-running quark mass to be determined simultaneously.By using these improved PMC scale-setting procedures,the renormalization scale dependence of the MS¯-on-shell quark mass relation can be eliminated systematically.Consequently,the top-quark on-shell(or MS¯)mass can be determined without conventional renormalization scale ambiguity.Taking the top-quark MS¯mass m¯t(m¯t)=162.5+2.1−1.5 GeV as the input,we obtain Mt≃172.41+2.21−1.57 GeV.Here,the uncertainties arise from errors combined with those fromΔαs(MZ)and the approximate uncertainty resulting from the uncalculated five-loop terms predicted through the Padéapproximation approach.展开更多
In this paper,the proton structure function F_(2)^(p)(x,Q^(2))at small-x is investigated using an analytical solution to the Balitsky–Kovchegov(BK)equation.In the context of the color dipole description of deep inela...In this paper,the proton structure function F_(2)^(p)(x,Q^(2))at small-x is investigated using an analytical solution to the Balitsky–Kovchegov(BK)equation.In the context of the color dipole description of deep inelastic scattering(DIS),the structure function F_(2)^(p)(x,Q^(2))is computed by applying the analytical expression for the scattering amplitude N(k,Y)derived from the BK solution.At transverse momentum k and total rapidity Y,the scattering amplitude N(k,Y)represents the propagation of the quark-antiquark dipole in the color dipole description of DIS.Using the BK solution we extracted the integrated gluon density xg(x,Q^(2))and then compared our theoretical estimation with the LHAPDF global data fits,NNPDF3.1sx and CT18.Finally,we have investigated the behavior of F_(2)^(p)(x,Q^(2))in the kinematic region of 10^(-5)≤x≤10^(-2)and 2.5 GeV^(2)≤Q^(2)≤60 GeV^(2).Our predicted results for F_(2)^(p)(x,Q^(2))within the specified kinematic region are in good agreement with the recent high-precision data for F_(2)^(p)(x,Q^(2))from HERA(H1 Collaboration)and the LHAPDF global parametrization group NNPDF3.1sx.展开更多
Within the framework of nonrelativistic-QCD factorization,we calculate both the next-to-leading-order relativistic and QCD corrections to prompt J/ψpair production,with feed-down fromψ(2S)mesons,via photon-photon co...Within the framework of nonrelativistic-QCD factorization,we calculate both the next-to-leading-order relativistic and QCD corrections to prompt J/ψpair production,with feed-down fromψ(2S)mesons,via photon-photon collisions at future e^(+)e^(−)colliders,including the Future Circular Lepton Collider(FCC-ee),the Circular Electron Positron Collider(CEPC),and the Compact Linear Collider(CLIC).We present total cross sections and distributions in single J/ψtransverse momentum and rapidity,as well as in J/ψpair invariant mass.The relativistic and QCD corrections both turn out to be large and negative.However,the production rates are large enough for useful experimental studies.展开更多
The annihilation type diagrams are difficult to calculate in any kind of model or method. Encouraged by the successful calculation of pure annihilation type B decays in the perturbative QCD factorization approach, we ...The annihilation type diagrams are difficult to calculate in any kind of model or method. Encouraged by the successful calculation of pure annihilation type B decays in the perturbative QCD factorization approach, we calculate the pure annihilation type D→ PP(V) decays in the perturbative QCD approach based on the kw factorization. Although the expansion parameter 1lind is not very small, our leading order numerical results agree with the existing experimental data for most channels. We expect more accurate observation from experiments, which can help us learn about the dynamics of D meson weak decays.展开更多
Analogous to the quarkyonic matter at high baryon density in which the quark Fermi seas and the baryonic excitations coexist, it is argued that a "quarksonic matter" phase appears at high isospin density where the q...Analogous to the quarkyonic matter at high baryon density in which the quark Fermi seas and the baryonic excitations coexist, it is argued that a "quarksonic matter" phase appears at high isospin density where the quark (antiquark) Fermi seas and the mesonic excitations coexist. We explore this phase in detail in both large Nc and asymptotically free limits. In the large Nc limit, we sketch a phase diagram for the quarksonic matter. In the asymptotically free limit, we study the pion superfluidity and thermodynamics of the quarksonic matter by using both perturbative calculations and an effective model.展开更多
The accurate equilibrium structures of S_3 and S_3^- are determined by the coupled-cluster method with single, double excitation and perturbative triple excitation(CCSD(T)) with basis sets of aug-cc-pV(n+d)Z(n = T, Q,...The accurate equilibrium structures of S_3 and S_3^- are determined by the coupled-cluster method with single, double excitation and perturbative triple excitation(CCSD(T)) with basis sets of aug-cc-pV(n+d)Z(n = T, Q, 5, or 6), complete basis set extrapolation functions with two-parameters and three-parameters, together with considering the contributions due to the core-valence electron correlation, scalar relativistic effects, spin–orbit coupling, and zero-point vibrational corrections. Our calculations show that both the neutral S_3 and anion S_3^- have open forms with C_(2r) vsymmetry. On the basis of the stable geometries, the adiabatic electron affinity of S_3 is determined to be 19041(11) cm^(-1), which is in excellent agreement with the experimental data(19059(7) cm^(-1)). The dependence of geometries and electron affinity on the computation level and physical corrections is discussed. The present computational results are helpful to the experimental molecular spectroscopy and bonding of S_3.展开更多
We investigate the impact of so-called kinematic constraint on gluon evolution at small x.Implanting the constraint on the real emission term of the gluon ladder diagram,we obtain an integro-differential form of the B...We investigate the impact of so-called kinematic constraint on gluon evolution at small x.Implanting the constraint on the real emission term of the gluon ladder diagram,we obtain an integro-differential form of the Balitsky-Fadin-Kuraev-Lipatov(BFKL)equation.Later we solve the equation analytically using the method of characteristics.We sketch the Bjorken x and transverse momentum kt2 dependence of our solution of unintegrated gluon distributions f(x,kt2)in the kinematic constraint supplemented BFKL equation and contrasted the same with the original BFKL equation.Then we extract the integrated gluon density xg(x,Q2)from unintegrated gluon distributions f(x,kt2)and compared our theoretical prediction with that of global data fits,namely NNPDF3.1 sx and CT14.Finally we illustrate the phenomenological implication of our solution for unintegrated gluon distribution f(x,kT2)towards exploring high precision HERA DIS data by the theoretical prediction of proton structure functions(F2 and FL).展开更多
The Bu→ψM decays are studied with the perturbative QCD approach, where the psion ψ=ψ(2S), ψ(3770), ψ(4040) and ψ(4160), and the light meson M = π, K, ρ and K^*. The factorizable and non-factorizable ...The Bu→ψM decays are studied with the perturbative QCD approach, where the psion ψ=ψ(2S), ψ(3770), ψ(4040) and ψ(4160), and the light meson M = π, K, ρ and K^*. The factorizable and non-factorizable contributions, and the S-D wave mixing effects on the psions, are considered in the calculation. With appropriate inputs, the branching ratios for the Bu→ψM decays are generally coincident with the experimental data within errors. However, due to the large theoretical and experimental errors, it is impossible for the moment to give a severe constraint on the S-D wave mixing angles.展开更多
We use the constituent quark model to extract polarized parton distributions and finally polarized nucleon structure function.Due to limited experimental data which do not cover whole (x,Q 2 ) plane and to increase ...We use the constituent quark model to extract polarized parton distributions and finally polarized nucleon structure function.Due to limited experimental data which do not cover whole (x,Q 2 ) plane and to increase the reliability of the fitting,we employ the Jacobi orthogonal polynomials expansion.It will be possible to extract the polarized structure functions for Helium,using the convolution of the nucleon polarized structure functions with the light cone moment distribution.The results are in good agreement with available experimental data and some theoretical models.展开更多
We present a phenomenological analysis of the space- and time-like charged kaon electromagnetic form factors in factorized perturbative QCD (pQCD) by employing an analytic model for αs (Q2 ) and an infrared (IR...We present a phenomenological analysis of the space- and time-like charged kaon electromagnetic form factors in factorized perturbative QCD (pQCD) by employing an analytic model for αs (Q2 ) and an infrared (IR) finite gluon propagator. In the space-like region, due to the lack of available experimental data above Q2 ~ 0.2 GeV2 , we only give our results for intermediate energies and make no comparison. In the time-like region, our results agree reasonably well with the available experimental data at moderate energies, including the CLEO data and the J/ψ result.展开更多
We investigate cold nuclear matter(CNM) effects on the productions of isolated prompt photons and +jet in proton-lead collisions at 8.16 TeV under next-to-leading order perturbative quantum chromodynamics calculations...We investigate cold nuclear matter(CNM) effects on the productions of isolated prompt photons and +jet in proton-lead collisions at 8.16 TeV under next-to-leading order perturbative quantum chromodynamics calculations with four parameterizations for nuclear parton distribution functions(nPDFs), i.e., DSSZ, EPPS16, nCTEQ15, and nIMParton. Our theoretical calculations provide good descriptions of the pp baseline in the ATLAS collaboration and make predictions for future experimental results at p+Pb collisions. We calculate the dependence of the nuclear modification factor of isolated prompt photons on transverse momentum pу/T and pseudo-rapidity η~у at very forward and backward rapidity regions, and we demonstrate that the forward-to-backward yield asymmetries Yasym/pPb as a function of pу/T with different nPDF parameterizations have diverse behaviors. Furthermore, the nuclear modification factor of isolated-у+jet RуJet/pPb as a function of у+jet's pseudo-rapidity η_(уJet)=1/2(η_у+η_(Jet)) at different average transverse momenta pavg/T=1/2(pу/T+pJet/T) has been discussed. This can facilitate a tomographic study of CNM effects with precis locations in a rather wide kinematic region by varying the transverse momenta and rapidities of both isolated photons and jets in p+A collisions.展开更多
In this paper,we calculated the B →(J/ψ,ηc) K decays in the perturbative QCD(pQCD) factorization approach with the inclusion of the partial next-to-leading order(NLO) contributions. With the inclusion of the ...In this paper,we calculated the B →(J/ψ,ηc) K decays in the perturbative QCD(pQCD) factorization approach with the inclusion of the partial next-to-leading order(NLO) contributions. With the inclusion of the significant enhancement from the NLO vertex corrections,the NLO pQCD predictions for the branching ratios agree with the data within 2σ errors:Br(B0 → J/ψK0) = 5.2-+32..58×10-4,Br(B+ → J/ψK+) = 5.6-+32..79×10-4,Br(B0 →ηcK0) = 5.5-+22..30 × 10-4,Br(B+ →ηcK+) = 5.9-+22..51 × 10-4.展开更多
The exclusive decay of the Higgs boson to a vector meson (J/φ or γ(1S)) and Z boson is studied in this work. The decay amplitudes are separated into two parts in a gauge invariant manner. The first part comes fr...The exclusive decay of the Higgs boson to a vector meson (J/φ or γ(1S)) and Z boson is studied in this work. The decay amplitudes are separated into two parts in a gauge invariant manner. The first part comes from the direct coupling of the Higgs boson to the charm (bottom) quark and the other from the HZZ* or the loop-induced HZγ* vertexes in the standard model. While the branching ratios from the direct channel are much smaller than those of the indirect channel, their interference terms give nontrivial contributions. We further calculate the QCD radiative corrections to both channels, which reduce the total branching ratios by around 20% for both J/φ and γ(1S) production. Our results provide a possible chance to check the SM predictions of the Hcc(Hbb) coupling and to seek for hints of new physics at the High Luminosity LHC or future hadron colliders.展开更多
We calculate the next-to-leading-order cross section for the inclusive production ofΛ(b )baryons in pp collisions in the general-mass variable-flavor-number scheme.We use realistic evolved non-perturbative fragment...We calculate the next-to-leading-order cross section for the inclusive production ofΛ(b )baryons in pp collisions in the general-mass variable-flavor-number scheme.We use realistic evolved non-perturbative fragmentation functions obtained from fits to B-meson production in e^+e^-annihilation and compare our results for transversemomentum and rapidity distributions with recent experimental data from the CMS and the LHCb collaborations at the CERN LHC.We find satisfactory agreement in general,with some indication for the need to modify the available fragmentation functions at larger values of the scale variable.展开更多
We present a detailed study on the properties of the free energy density at high temperature by applying the principle of maximum conformality(PMC)scale-setting method within effective field theory.The PMC utilizes ...We present a detailed study on the properties of the free energy density at high temperature by applying the principle of maximum conformality(PMC)scale-setting method within effective field theory.The PMC utilizes the renormalization group equation recursively to identify the occurrence and pattern of the non-conformal{βi}-terms,and determines the optimal renormalization scale at each order.Our analysis shows that a more accurate free energy density up to gs^5-order level without renormalization scale dependence can be achieved by applying the PMC.We also observe that by using a smaller factorization scale around the effective parameter m E,the PMC prediction is consistent with the lattice QCD prediction derived at low temperature.展开更多
An extrapolation to the physical limit for the lattice data of Λ_b →Λ_c form factors computed in the nonphysical region is made in this work through a class of fitting functions proposed by us with nonlinear depend...An extrapolation to the physical limit for the lattice data of Λ_b →Λ_c form factors computed in the nonphysical region is made in this work through a class of fitting functions proposed by us with nonlinear dependence on m2/π derived in the chiral perturbative theory(ChPT) and the heavy quark effective theory(HQET) framework. Then the results are applied to calculate the differential and integrated Λ_b →Λ_c semileptonic decay rates. Meanwhile, a comparison between our results and those obtained through the extrapolation functions with naive linear dependenceon m2/π is made.It is shown that the difference between the extrapolated central values of these two cases is about 5%.The total uncertainties(depending on the momentum transfer q^2) in the linear case are about 5% ~10%(caused by the uncertainties of lattice data) and those in the nonlinear case are about 10% ~ 20%(caused by the uncertainties of both lattice data and input parameters in Ch PT and HQET). More accurate lattice data and parameters in ChPT and HQET are needed to reduce the uncertainties of the extrapolated results.展开更多
Based on the assumption of two-quark structure of the scalar meson K0^*(1430), we calculate the CP-averaged branching ratios for B→K0^*(1430)η(') decays in the framework of the perturbative QCD (pQCD) app...Based on the assumption of two-quark structure of the scalar meson K0^*(1430), we calculate the CP-averaged branching ratios for B→K0^*(1430)η(') decays in the framework of the perturbative QCD (pQCD) approach here. We perform the evaluations in two scenarios for the scalar meson spectrum. We find that: (a) the pQCD predictions for Br(B→K0^*(1430)η(')) which are about 10^-5 10^-6, basically agree with the data within large theoretical uncertainty; (b) the agreement between the pQCD predictions and the data in Scenario Ⅰ is better than that in Scenario Ⅱ, which can be tested by the forthcoming LHC experiments; (c) the annihilation contributions play an important role for these considered decays.展开更多
A systematization for the manipulations and calculations involving divergent (or not) Feynman integrals, typical of the one loop perturbative solutions of Quantum Field Theory, is proposed. A previous work on the same...A systematization for the manipulations and calculations involving divergent (or not) Feynman integrals, typical of the one loop perturbative solutions of Quantum Field Theory, is proposed. A previous work on the same issue is generalized to treat theories and models having different species of massive fields. An improvement on the strategy is adopted so that no regularization needs to be used. The final results produced, however, can be converted into the ones of reasonable regularizations, especially those belonging to the dimensional regularization (in situations where the method applies). Through an adequate interpretation of the Feynman rules and a convenient representation for involved propagators, the finite and divergent parts are separated before the introduction of the integration in the loop momentum. Only the finite integrals obtained are in fact integrated. The divergent content of the amplitudes are written as a combination of standard mathematical object which are never really integrated. Only very general scale properties of such objects are used. The finite parts, on the other hand, are written in terms of basic functions conveniently introduced. The scale properties of such functions relate them to a well defined way to the basic divergent objects providing simple and transparent connection between both parts in the assintotic regime. All the arbitrariness involved in this type of calculations are preserved in the intermediary steps allowing the identification of universal properties for the divergent integrals, which are required for the maintenance of fundamental symmetries like translational invariance and scale independence in the perturbative amplitudes. Once these consistency relations are imposed no other symmetry is violated in perturbative calculations neither ambiguous terms survive at any theory or model formulated at any space-time dimension including nonrenormalizable cases. Representative examples of perturbative amplitudes involving different species of massive fermions are consid展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.11935013,12175291,11822508,and 12047503)the Chinese Academy Sciences(Grant Nos.YSBR-101,and XDPB15)the support of the HPC Cluster of lnstitute of Theoretical Physics,Chinese Academy of Sciences(ITP-CAS)。
文摘We obtain the integrand of full-color four-loop three-point form factor of the stress-tensor supermultiplet in N=4 SYM,based on the color-kinematics(CK)duality and generalized unitarity method.Our result not only manifests all dual Jacobi relations via CK duality but also contains 133 free parameters.This suggests the constructibility of the form factor at even higher loops via CK duality.We also find that the planar form factor has a hidden dual conformal symmetry in the lightlike limit of the operator momentum,which is checked up to four loops.
基金Supported by the Wuhan University Research Development Fund。
文摘The periapsis shift of charged test particles in arbitrary static and spherically symmetric charged spacetimes are studied.Two perturbative methods,the near-circular approximation and post-Newtonian methods,are developed and shown to be very accurate when the results are determined to high orders.The near-circular approximation method is more precise when eccentricity e of the orbit is small,whereas the post-Newtonian method is more effective when orbit semilatus rectum p is large.Results from these two methods are shown to agree when both e is small and p is large.These results are then applied to the Reissner-Nordström spacetime,the Einstein-Maxwell-dilation gravity,and a charged wormhole spacetime.The effects of various parameters on the periapsis shift,particularly that of the electrostatic interaction,are carefully studied.The periapsis shift data of the solar-Mercury are then used to constrain the charges of the Sun and Mercury,and the data of the Sgr A^(*)-S2 periapsis shift are used to determine,for the first time using this method,the constraints of the charges of Sgr A^(*)and S2.
基金Supported in part by the National Natural Science Foundation of China(12247129,12175025,12347101)the Graduate Research and Innovation Foundation of Chongqing,China(ydstd1912)。
文摘The principle of maximum conformality(PMC)provides a systematic approach to solve the conventional renormalization scheme and scale ambiguities.Scale-fixed predictions of physical observables using the PMC are independent of the choice of renormalization scheme–a key requirement for renormalization group invariance.In this paper,we derive new degeneracy relations based on the renormalization group equations that involve both the usualβ-function and the quark mass anomalous dimensionγm-function.These new degeneracy relations enable improved PMC scale-setting procedures for correct magnitudes of the strong coupling constant and MS¯-running quark mass to be determined simultaneously.By using these improved PMC scale-setting procedures,the renormalization scale dependence of the MS¯-on-shell quark mass relation can be eliminated systematically.Consequently,the top-quark on-shell(or MS¯)mass can be determined without conventional renormalization scale ambiguity.Taking the top-quark MS¯mass m¯t(m¯t)=162.5+2.1−1.5 GeV as the input,we obtain Mt≃172.41+2.21−1.57 GeV.Here,the uncertainties arise from errors combined with those fromΔαs(MZ)and the approximate uncertainty resulting from the uncalculated five-loop terms predicted through the Padéapproximation approach.
文摘In this paper,the proton structure function F_(2)^(p)(x,Q^(2))at small-x is investigated using an analytical solution to the Balitsky–Kovchegov(BK)equation.In the context of the color dipole description of deep inelastic scattering(DIS),the structure function F_(2)^(p)(x,Q^(2))is computed by applying the analytical expression for the scattering amplitude N(k,Y)derived from the BK solution.At transverse momentum k and total rapidity Y,the scattering amplitude N(k,Y)represents the propagation of the quark-antiquark dipole in the color dipole description of DIS.Using the BK solution we extracted the integrated gluon density xg(x,Q^(2))and then compared our theoretical estimation with the LHAPDF global data fits,NNPDF3.1sx and CT18.Finally,we have investigated the behavior of F_(2)^(p)(x,Q^(2))in the kinematic region of 10^(-5)≤x≤10^(-2)and 2.5 GeV^(2)≤Q^(2)≤60 GeV^(2).Our predicted results for F_(2)^(p)(x,Q^(2))within the specified kinematic region are in good agreement with the recent high-precision data for F_(2)^(p)(x,Q^(2))from HERA(H1 Collaboration)and the LHAPDF global parametrization group NNPDF3.1sx.
基金Supported in part by the German Research Foundation DFG through Research Unit FOR 2926"Next Generation Perturbative QCD for Hadron Structure:Preparing for the Electron-Ion Collider"(409651613)National Natural Science Foundation of China(12061131006)National Natural Science Foundation of China(U1832160,12075177)。
文摘Within the framework of nonrelativistic-QCD factorization,we calculate both the next-to-leading-order relativistic and QCD corrections to prompt J/ψpair production,with feed-down fromψ(2S)mesons,via photon-photon collisions at future e^(+)e^(−)colliders,including the Future Circular Lepton Collider(FCC-ee),the Circular Electron Positron Collider(CEPC),and the Compact Linear Collider(CLIC).We present total cross sections and distributions in single J/ψtransverse momentum and rapidity,as well as in J/ψpair invariant mass.The relativistic and QCD corrections both turn out to be large and negative.However,the production rates are large enough for useful experimental studies.
基金Supported by National Science Foundation of China(11228512,11235005,11075168)
文摘The annihilation type diagrams are difficult to calculate in any kind of model or method. Encouraged by the successful calculation of pure annihilation type B decays in the perturbative QCD factorization approach, we calculate the pure annihilation type D→ PP(V) decays in the perturbative QCD approach based on the kw factorization. Although the expansion parameter 1lind is not very small, our leading order numerical results agree with the existing experimental data for most channels. We expect more accurate observation from experiments, which can help us learn about the dynamics of D meson weak decays.
基金Supported by Thousand Young Talents Program of China,Shanghai Natural Science Foundation,(14ZR1403000)NSFC(11535012)China Postdoctoral Science Foundation(KLH1512072)
文摘Analogous to the quarkyonic matter at high baryon density in which the quark Fermi seas and the baryonic excitations coexist, it is argued that a "quarksonic matter" phase appears at high isospin density where the quark (antiquark) Fermi seas and the mesonic excitations coexist. We explore this phase in detail in both large Nc and asymptotically free limits. In the large Nc limit, we sketch a phase diagram for the quarksonic matter. In the asymptotically free limit, we study the pion superfluidity and thermodynamics of the quarksonic matter by using both perturbative calculations and an effective model.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11874179,11447194,11574114,and 11874177)the Natural Science Foundation of Jilin Province,China(Grant No.20180101289JC)
文摘The accurate equilibrium structures of S_3 and S_3^- are determined by the coupled-cluster method with single, double excitation and perturbative triple excitation(CCSD(T)) with basis sets of aug-cc-pV(n+d)Z(n = T, Q, 5, or 6), complete basis set extrapolation functions with two-parameters and three-parameters, together with considering the contributions due to the core-valence electron correlation, scalar relativistic effects, spin–orbit coupling, and zero-point vibrational corrections. Our calculations show that both the neutral S_3 and anion S_3^- have open forms with C_(2r) vsymmetry. On the basis of the stable geometries, the adiabatic electron affinity of S_3 is determined to be 19041(11) cm^(-1), which is in excellent agreement with the experimental data(19059(7) cm^(-1)). The dependence of geometries and electron affinity on the computation level and physical corrections is discussed. The present computational results are helpful to the experimental molecular spectroscopy and bonding of S_3.
基金the Department of Science and Technology(DST),India(grant DST/INSPIRE Fellowship/2017/IF160770)the Council of Scientific and Industrial Research(CSIR),New Delhi(grant 09/796(0064)2016-EMR-I)respectively for the financial assistantship.
文摘We investigate the impact of so-called kinematic constraint on gluon evolution at small x.Implanting the constraint on the real emission term of the gluon ladder diagram,we obtain an integro-differential form of the Balitsky-Fadin-Kuraev-Lipatov(BFKL)equation.Later we solve the equation analytically using the method of characteristics.We sketch the Bjorken x and transverse momentum kt2 dependence of our solution of unintegrated gluon distributions f(x,kt2)in the kinematic constraint supplemented BFKL equation and contrasted the same with the original BFKL equation.Then we extract the integrated gluon density xg(x,Q2)from unintegrated gluon distributions f(x,kt2)and compared our theoretical prediction with that of global data fits,namely NNPDF3.1 sx and CT14.Finally we illustrate the phenomenological implication of our solution for unintegrated gluon distribution f(x,kT2)towards exploring high precision HERA DIS data by the theoretical prediction of proton structure functions(F2 and FL).
基金Supported by the National Natural Science Foundation of China(11705047,U1632109,11547014,11475055)Open Research Program of Large Research Infrastructures(2017)Chinese Academy of Sciences
文摘The Bu→ψM decays are studied with the perturbative QCD approach, where the psion ψ=ψ(2S), ψ(3770), ψ(4040) and ψ(4160), and the light meson M = π, K, ρ and K^*. The factorizable and non-factorizable contributions, and the S-D wave mixing effects on the psions, are considered in the calculation. With appropriate inputs, the branching ratios for the Bu→ψM decays are generally coincident with the experimental data within errors. However, due to the large theoretical and experimental errors, it is impossible for the moment to give a severe constraint on the S-D wave mixing angles.
文摘We use the constituent quark model to extract polarized parton distributions and finally polarized nucleon structure function.Due to limited experimental data which do not cover whole (x,Q 2 ) plane and to increase the reliability of the fitting,we employ the Jacobi orthogonal polynomials expansion.It will be possible to extract the polarized structure functions for Helium,using the convolution of the nucleon polarized structure functions with the light cone moment distribution.The results are in good agreement with available experimental data and some theoretical models.
基金Supported by National Natural Science Foundation of China (10735080, 11075059)
文摘We present a phenomenological analysis of the space- and time-like charged kaon electromagnetic form factors in factorized perturbative QCD (pQCD) by employing an analytic model for αs (Q2 ) and an infrared (IR) finite gluon propagator. In the space-like region, due to the lack of available experimental data above Q2 ~ 0.2 GeV2 , we only give our results for intermediate energies and make no comparison. In the time-like region, our results agree reasonably well with the available experimental data at moderate energies, including the CLEO data and the J/ψ result.
基金Supported by the NSFC of China(11435004,11322546,11805167)partly Supported by China University of Geosciences(Wuhan)(162301182691)
文摘We investigate cold nuclear matter(CNM) effects on the productions of isolated prompt photons and +jet in proton-lead collisions at 8.16 TeV under next-to-leading order perturbative quantum chromodynamics calculations with four parameterizations for nuclear parton distribution functions(nPDFs), i.e., DSSZ, EPPS16, nCTEQ15, and nIMParton. Our theoretical calculations provide good descriptions of the pp baseline in the ATLAS collaboration and make predictions for future experimental results at p+Pb collisions. We calculate the dependence of the nuclear modification factor of isolated prompt photons on transverse momentum pу/T and pseudo-rapidity η~у at very forward and backward rapidity regions, and we demonstrate that the forward-to-backward yield asymmetries Yasym/pPb as a function of pу/T with different nPDF parameterizations have diverse behaviors. Furthermore, the nuclear modification factor of isolated-у+jet RуJet/pPb as a function of у+jet's pseudo-rapidity η_(уJet)=1/2(η_у+η_(Jet)) at different average transverse momenta pavg/T=1/2(pу/T+pJet/T) has been discussed. This can facilitate a tomographic study of CNM effects with precis locations in a rather wide kinematic region by varying the transverse momenta and rapidities of both isolated photons and jets in p+A collisions.
基金Supported by National Natural Science Foundation of China (10605012,10735080)Project on Graduate Students' Education and Innovation of Jiangsu Province (CX09B 297Z)
文摘In this paper,we calculated the B →(J/ψ,ηc) K decays in the perturbative QCD(pQCD) factorization approach with the inclusion of the partial next-to-leading order(NLO) contributions. With the inclusion of the significant enhancement from the NLO vertex corrections,the NLO pQCD predictions for the branching ratios agree with the data within 2σ errors:Br(B0 → J/ψK0) = 5.2-+32..58×10-4,Br(B+ → J/ψK+) = 5.6-+32..79×10-4,Br(B0 →ηcK0) = 5.5-+22..30 × 10-4,Br(B+ →ηcK+) = 5.9-+22..51 × 10-4.
基金Supported by National Natural Science Foundation of China(11375168)
文摘The exclusive decay of the Higgs boson to a vector meson (J/φ or γ(1S)) and Z boson is studied in this work. The decay amplitudes are separated into two parts in a gauge invariant manner. The first part comes from the direct coupling of the Higgs boson to the charm (bottom) quark and the other from the HZZ* or the loop-induced HZγ* vertexes in the standard model. While the branching ratios from the direct channel are much smaller than those of the indirect channel, their interference terms give nontrivial contributions. We further calculate the QCD radiative corrections to both channels, which reduce the total branching ratios by around 20% for both J/φ and γ(1S) production. Our results provide a possible chance to check the SM predictions of the Hcc(Hbb) coupling and to seek for hints of new physics at the High Luminosity LHC or future hadron colliders.
文摘We calculate the next-to-leading-order cross section for the inclusive production ofΛ(b )baryons in pp collisions in the general-mass variable-flavor-number scheme.We use realistic evolved non-perturbative fragmentation functions obtained from fits to B-meson production in e^+e^-annihilation and compare our results for transversemomentum and rapidity distributions with recent experimental data from the CMS and the LHCb collaborations at the CERN LHC.We find satisfactory agreement in general,with some indication for the need to modify the available fragmentation functions at larger values of the scale variable.
基金Supported by Natural Science Foundation of China(11625520)
文摘We present a detailed study on the properties of the free energy density at high temperature by applying the principle of maximum conformality(PMC)scale-setting method within effective field theory.The PMC utilizes the renormalization group equation recursively to identify the occurrence and pattern of the non-conformal{βi}-terms,and determines the optimal renormalization scale at each order.Our analysis shows that a more accurate free energy density up to gs^5-order level without renormalization scale dependence can be achieved by applying the PMC.We also observe that by using a smaller factorization scale around the effective parameter m E,the PMC prediction is consistent with the lattice QCD prediction derived at low temperature.
基金Supported by National Natural Science Foundation of China under Grant Nos.11775024 and 11575023
文摘An extrapolation to the physical limit for the lattice data of Λ_b →Λ_c form factors computed in the nonphysical region is made in this work through a class of fitting functions proposed by us with nonlinear dependence on m2/π derived in the chiral perturbative theory(ChPT) and the heavy quark effective theory(HQET) framework. Then the results are applied to calculate the differential and integrated Λ_b →Λ_c semileptonic decay rates. Meanwhile, a comparison between our results and those obtained through the extrapolation functions with naive linear dependenceon m2/π is made.It is shown that the difference between the extrapolated central values of these two cases is about 5%.The total uncertainties(depending on the momentum transfer q^2) in the linear case are about 5% ~10%(caused by the uncertainties of lattice data) and those in the nonlinear case are about 10% ~ 20%(caused by the uncertainties of both lattice data and input parameters in Ch PT and HQET). More accurate lattice data and parameters in ChPT and HQET are needed to reduce the uncertainties of the extrapolated results.
基金Supported by National Natural Science Foundation of China (10575052,10605012,10735080)
文摘Based on the assumption of two-quark structure of the scalar meson K0^*(1430), we calculate the CP-averaged branching ratios for B→K0^*(1430)η(') decays in the framework of the perturbative QCD (pQCD) approach here. We perform the evaluations in two scenarios for the scalar meson spectrum. We find that: (a) the pQCD predictions for Br(B→K0^*(1430)η(')) which are about 10^-5 10^-6, basically agree with the data within large theoretical uncertainty; (b) the agreement between the pQCD predictions and the data in Scenario Ⅰ is better than that in Scenario Ⅱ, which can be tested by the forthcoming LHC experiments; (c) the annihilation contributions play an important role for these considered decays.
文摘A systematization for the manipulations and calculations involving divergent (or not) Feynman integrals, typical of the one loop perturbative solutions of Quantum Field Theory, is proposed. A previous work on the same issue is generalized to treat theories and models having different species of massive fields. An improvement on the strategy is adopted so that no regularization needs to be used. The final results produced, however, can be converted into the ones of reasonable regularizations, especially those belonging to the dimensional regularization (in situations where the method applies). Through an adequate interpretation of the Feynman rules and a convenient representation for involved propagators, the finite and divergent parts are separated before the introduction of the integration in the loop momentum. Only the finite integrals obtained are in fact integrated. The divergent content of the amplitudes are written as a combination of standard mathematical object which are never really integrated. Only very general scale properties of such objects are used. The finite parts, on the other hand, are written in terms of basic functions conveniently introduced. The scale properties of such functions relate them to a well defined way to the basic divergent objects providing simple and transparent connection between both parts in the assintotic regime. All the arbitrariness involved in this type of calculations are preserved in the intermediary steps allowing the identification of universal properties for the divergent integrals, which are required for the maintenance of fundamental symmetries like translational invariance and scale independence in the perturbative amplitudes. Once these consistency relations are imposed no other symmetry is violated in perturbative calculations neither ambiguous terms survive at any theory or model formulated at any space-time dimension including nonrenormalizable cases. Representative examples of perturbative amplitudes involving different species of massive fermions are consid