In 2021,the Belle collaboration reported the first observation of a new structure in theψ(2S)γfinal state produced in the two-photon fusion process.In the hadronic molecule picture,this new structure can be associat...In 2021,the Belle collaboration reported the first observation of a new structure in theψ(2S)γfinal state produced in the two-photon fusion process.In the hadronic molecule picture,this new structure can be associatedwith the shallow isoscalar D*D* bound state and as such is an excellent candidate for the spin-2 partner of the X(3872)with the quantum numbers J^(PC)=2^(++)conventionally named X_(2).展开更多
In this paper, I review recent progress in the study of the XYZ particles at Belle. I only focus on studies with charmonium and one or more light mesons in the final states. This covers the X（3872）, X（3915）, Y（4...In this paper, I review recent progress in the study of the XYZ particles at Belle. I only focus on studies with charmonium and one or more light mesons in the final states. This covers the X（3872）, X（3915）, Y（4140）, X（4350）, and the charged Z states.展开更多
We study the masses of Qq^- Q ^- q＇ states with J^PC=0^＋＋,1＋＋ and 2^＋＋ in the chiral SU（3）quark model, where Q is the heavy quark （c or b） and q （q＇） is the light quark （u, d or s）. According to our nu...We study the masses of Qq^- Q ^- q＇ states with J^PC=0^＋＋,1＋＋ and 2^＋＋ in the chiral SU（3）quark model, where Q is the heavy quark （c or b） and q （q＇） is the light quark （u, d or s）. According to our numerical results, it is improbable to make the interpretation of [cn^-C^-n]1＋＋ and [cn^-C^-n]2＋＋ （n = u, d） states as X（3872） and Y（3940）, respectively. However, it is interesting to find the tetraquarks in the bq^-b^-q＇ system.展开更多
The spin is an important property of a particle. Although it is unlikely, there is still a possibility that two particles with different spins share similar masses. In this paper, we propose a method to probe this kin...The spin is an important property of a particle. Although it is unlikely, there is still a possibility that two particles with different spins share similar masses. In this paper, we propose a method to probe this kind of mass degeneracy of particles with different spins. We use the cascade decay B^＋ →X（3872）K^＋, X（3872）→D^＋D^- to illustrate our method. It can be seen that the possible mass degeneracy of X（3872） can lead to interesting behavior in the corresponding cascade decay.展开更多
We revisit the compositeness theorem proposed by Weinberg in an effective field theory （EFT） and explore criteria which are sensitive to the structure of S-wave threshold states. On a general basis, we show that the...We revisit the compositeness theorem proposed by Weinberg in an effective field theory （EFT） and explore criteria which are sensitive to the structure of S-wave threshold states. On a general basis, we show that the wave function renormalization constant Z, which is the probability of finding an elementary component in the wave function of a threshold state, can be explicitly introduced in the description of the threshold state. As an application of this EFT method, we describe the near-threshold line shape of the D＊0D0 invariant mass spectrum in B→D＊0D-0K and determine a nonvanishing value of Z. It suggests that the X（3872） as a candidate of the D＊0D0 molecule may still contain a small cc core. This elementary component, on the one hand, explains its production in the B meson decay via a short-distance mechanism, and on the other hand, is correlated with the D＊0D0 threshold enhancement observed in the D＊0D0 invariant mass distributions. Meanwhile, we also show that if Z is non-zero, the near-threshold enhancement of the D＊0D0 mass spectrum in the B decay will be driven by the short-distance production mechanism.展开更多
We study the fine splitting in the charmomium spectrum in the quark model with the channel coupling effect, including DD, DD＊, D＊D＊ and DsDs, DsDs＊, Ds＊Ds＊ channels. The interaction for channel coupling is const...We study the fine splitting in the charmomium spectrum in the quark model with the channel coupling effect, including DD, DD＊, D＊D＊ and DsDs, DsDs＊, Ds＊Ds＊ channels. The interaction for channel coupling is constructed from the current-current Lagrangian related to the color confinement and the onegluon exchange potentials. By adopting the massive gluon propagator from the lattice cMculation in the nonperturbative region, the coupling interaction is further simplified to four-fermion interaction. The numerical calculation still prefers the assignment 1＋＋ of X（3872）.展开更多
We have performed a dynamical calculation of the bound state problem of D0D*0 by considering the pion and sigma meson exchange potential. Our preliminary analysis disfavors the molecular interpretation of X(3872) if w...We have performed a dynamical calculation of the bound state problem of D0D*0 by considering the pion and sigma meson exchange potential. Our preliminary analysis disfavors the molecular interpretation of X(3872) if we use the experimental D*Dπ coupling constant g=0.59 and a reasonable cutoff around 1 GeV,which is the typical hadronic scale. In contrast,there probably exists a loosely bound S-wave BB* molecular state. Such a molecular state would be rather stable since its dominant decay mode is the radiative decay through B*→Bγ.展开更多
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
For a system of current interest（composed of charm, anticharm and a pair of light quarks）, we show trends in phenomenological implications of QCD-based improvements to a simple quark model treatment. We employ a res...For a system of current interest（composed of charm, anticharm and a pair of light quarks）, we show trends in phenomenological implications of QCD-based improvements to a simple quark model treatment. We employ a resonating group method to render this difficult four-body problem manageable. We use a quadratic confinement so as to be able to improve beyond the Born approximation. We report the position of the pole corresponding to the D^0D^0＊ molecule for the best fit of a model parameter to the relevant QCD simulations. We point out the interesting possibility that the pole can be shifted to 3872 Me V by introducing another parameter I0 that changes the strength of the interaction in this one component of X（3872）. The revised value of this second parameter can guide future trends in modeling of the full exotic meson X（3872）. We also report the changes with I_0 in the S-wave spin averaged cross sections for D^0D^0＊-→ωJ/ψ and D^0D^0＊-→ρJ/ψ. These cross sections are important regarding the study of QGP（quark gluon plasma）.展开更多
The production of the X（3872） as a hadronic molecule in hadron colliders is clarified. We show that the conclusion of Bignamini et al., Phys. Rev. Lett. 103（2009） 162001, that the production of the X（3872） at hi...The production of the X（3872） as a hadronic molecule in hadron colliders is clarified. We show that the conclusion of Bignamini et al., Phys. Rev. Lett. 103（2009） 162001, that the production of the X（3872） at high pT implies a non-molecular structure, does not hold. In particular, using the well understood properties of the deuteron wave function as an example, we identify the relevant scales in the production process.展开更多
We study the Bc,u,d→X(3872)P decays in the perturbative QCD(PQCD)approach,involving the puzzling resonance X(3872),where P represents a light pseudoscalar meson(K orπ).Assuming X(3872)to be a 1++charmonium state,we ...We study the Bc,u,d→X(3872)P decays in the perturbative QCD(PQCD)approach,involving the puzzling resonance X(3872),where P represents a light pseudoscalar meson(K orπ).Assuming X(3872)to be a 1++charmonium state,we obtain the following results.(a)The branching ratios of the Bc+→X(3872)π+and Bc+→X(3872)K+decays are consistent with the results predicted by the covariant light-front approach within errors;however,they are larger than those given by the generalized factorization approach.(b)The branching ratio of the B+→X(3872)K+decay is predicted as(3.8-1.0+1.1)×10-4,which is smaller than the previous PQCD calculation result but still slightly larger than the upper limits set by Belle and BaBar.Hence,we suggest that the B0,+→X(3872)K0,+decays should be precisely measured by the LHCb and Belle II experiments to help probe the inner structure of X(3872).(c)Compared with the Bu,d→X(3872)K decays,the Bu,d→X(3872)πdecays have significantly smaller branching ratios,which drop to values as low as 10-6.(d)The direct CP violations of these considered decays are small(10-3~10-2)because the penguin contributions are loop suppressed compared to the tree contributions.The mixing-induced CP violation of the B→X(3872)K0S decay is highly consistent with the current world average value sin 2β=(69.9±1.7)%.Experimentally testing the results for the branching ratios and CP violations,including the implicit SU(3)and isospin symmetries of these decays,helps probe the nature of X(3872).展开更多
We investigate the decays of B^(0)→K^(0)X(3872)and B^(+)→K^(+)X(3872)based on the picture where the X(3872)resonance is strongly coupled to the DD*+c.c.channel.In addition to the decay mechanism where the X(3872)res...We investigate the decays of B^(0)→K^(0)X(3872)and B^(+)→K^(+)X(3872)based on the picture where the X(3872)resonance is strongly coupled to the DD*+c.c.channel.In addition to the decay mechanism where the X(3872)resonance is formed from the DD*pair hadronization with the short-distance interaction,we have also considered the DD*rescattering diagrams in the long-distance scale,where D andD*are formed from c andDD*separately.Because of the difference of the mass thresholds of charged and neutralDD*channels,and the rather narrow width of the X(3872)resonance,at the X(3872)mass,the loop functions ofD^(0)D*^(0)andD^(+)D*^(-)are much different.Taking this difference into account,the ratio of B[B^(0)→K^(0)X(3872)]/B[B+→K+X(3872)]■0.5 can be naturally obtained.Based on this result,we also evaluate the decay widths of B_s^(0)→η(η′)X(3872).It is expected that future experimental measurements of these decays can be used to elucidate the nature of the X(3872)resonance.展开更多
In this article, we test the nature of X（3872）, which is assumed to be a P-wave [cq]-scalar-diquark [cq]- axial-vector-antidiquark tetraquark state with JP = 2^-. The interpolating current representing the JP = 2^- ...In this article, we test the nature of X（3872）, which is assumed to be a P-wave [cq]-scalar-diquark [cq]- axial-vector-antidiquark tetraquark state with JP = 2^-. The interpolating current representing the JP = 2^- state is proposed. Technically, contributions of the operators up to dimension six are included in the operator product expansion. The mass obtained for such state is m2- = （4.38±0.15） GeV. We conclude that it is impossible to describe the X（3872） structure as JV = 2^- tetraauark state.展开更多
基金supported in part by the National Natural Science Foundation of China(Grant Nos.12070131001,12125507,11835015,and 12047503)the Deutsche Forschungsgemeinschaft(DFG)through the funds provided to the Sino-German Collaborative Research Center TRR110“Symmetries and the Emergence of Structure in QCD”(Project-ID 196253076)+4 种基金the Chinese Academy of Sciences(CAS)(Grant Nos.YSBR-101 and XDB34030000)the EU STRONG-2020 project under the program H2020-INFRAIA-2018-1(Grant No.824093)the Generalitat valenciana(GVA)for the project with ref.CIDEGENT/2019/015supported by the Slovenian Research Agency(research core Funding No.P1-0035)by CAS President’s International Fellowship Initiative(PIFI)(Grant No.2024PVA0004)。
文摘In 2021,the Belle collaboration reported the first observation of a new structure in theψ(2S)γfinal state produced in the two-photon fusion process.In the hadronic molecule picture,this new structure can be associatedwith the shallow isoscalar D*D* bound state and as such is an excellent candidate for the spin-2 partner of the X(3872)with the quantum numbers J^(PC)=2^(++)conventionally named X_(2).
基金Supported by National Natural Science Foundation of China (10825524,10935008)Department of Energy (DE-FG02-04ER41291) (U Hawaii)
文摘In this paper, I review recent progress in the study of the XYZ particles at Belle. I only focus on studies with charmonium and one or more light mesons in the final states. This covers the X（3872）, X（3915）, Y（4140）, X（4350）, and the charged Z states.
基金Supported by the National Natural Science Foundation of China under Grant No 10475087.
文摘We study the masses of Qq^- Q ^- q＇ states with J^PC=0^＋＋,1＋＋ and 2^＋＋ in the chiral SU（3）quark model, where Q is the heavy quark （c or b） and q （q＇） is the light quark （u, d or s）. According to our numerical results, it is improbable to make the interpretation of [cn^-C^-n]1＋＋ and [cn^-C^-n]2＋＋ （n = u, d） states as X（3872） and Y（3940）, respectively. However, it is interesting to find the tetraquarks in the bq^-b^-q＇ system.
基金Supported by National Natural Science Foundation of China(11347124,11147003,U1204115)Doctoral Scientific Research Foundation of USC,and Innovation Team of Nuclear and Particle Physics of USC
文摘The spin is an important property of a particle. Although it is unlikely, there is still a possibility that two particles with different spins share similar masses. In this paper, we propose a method to probe this kind of mass degeneracy of particles with different spins. We use the cascade decay B^＋ →X（3872）K^＋, X（3872）→D^＋D^- to illustrate our method. It can be seen that the possible mass degeneracy of X（3872） can lead to interesting behavior in the corresponding cascade decay.
基金Supported by National Natural Science Foundation of China (11147022, 11035006, 11305137)Chinese Academy of Sciences (KJCX2EW-N01)+2 种基金Ministry of Science and Technology of China (2009CB825200)DFG and NSFC (11261130311) through funds provided to the Sino-German CRC 110 "Symmetries and the Emergence of Structure in QCD"Doctor Foundation of Xinjiang University (BS110104)
文摘We revisit the compositeness theorem proposed by Weinberg in an effective field theory （EFT） and explore criteria which are sensitive to the structure of S-wave threshold states. On a general basis, we show that the wave function renormalization constant Z, which is the probability of finding an elementary component in the wave function of a threshold state, can be explicitly introduced in the description of the threshold state. As an application of this EFT method, we describe the near-threshold line shape of the D＊0D0 invariant mass spectrum in B→D＊0D-0K and determine a nonvanishing value of Z. It suggests that the X（3872） as a candidate of the D＊0D0 molecule may still contain a small cc core. This elementary component, on the one hand, explains its production in the B meson decay via a short-distance mechanism, and on the other hand, is correlated with the D＊0D0 threshold enhancement observed in the D＊0D0 invariant mass distributions. Meanwhile, we also show that if Z is non-zero, the near-threshold enhancement of the D＊0D0 mass spectrum in the B decay will be driven by the short-distance production mechanism.
基金Supported by National Natural Science Foundation of China (10675008)
文摘We study the fine splitting in the charmomium spectrum in the quark model with the channel coupling effect, including DD, DD＊, D＊D＊ and DsDs, DsDs＊, Ds＊Ds＊ channels. The interaction for channel coupling is constructed from the current-current Lagrangian related to the color confinement and the onegluon exchange potentials. By adopting the massive gluon propagator from the lattice cMculation in the nonperturbative region, the coupling interaction is further simplified to four-fermion interaction. The numerical calculation still prefers the assignment 1＋＋ of X（3872）.
基金National Natural Science Foundation of China(10625521, 10675008, 10705001, 10775146, 10721063)China Postdoctoral Science Foundation(20070420526)K.C. Wong Education Foundation, Hong Kong
文摘We have performed a dynamical calculation of the bound state problem of D0D*0 by considering the pion and sigma meson exchange potential. Our preliminary analysis disfavors the molecular interpretation of X(3872) if we use the experimental D*Dπ coupling constant g=0.59 and a reasonable cutoff around 1 GeV,which is the typical hadronic scale. In contrast,there probably exists a loosely bound S-wave BB* molecular state. Such a molecular state would be rather stable since its dominant decay mode is the radiative decay through B*→Bγ.
基金This material is based upon work supported in part by the U.S.Department of Energy,Office of Science,Office of Nuclear Physics(DE-AC05-06OR23177)the U.S.Department of Energy,Office of Science,(DE-SC0009919)
文摘We briefly comment on the paper by Albaladejo et al., Chinese Phys. C 41 121001, rejecting its conclusions.
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 of PU research (D/605/Est.I Sr. 20 Project 2014-15, D/34/Est.1 Sr. 109 Project 2013-14)the Higher Education Commission (HEC) of Pakistan for its financial support through (17-5-4(Ps3-128) HEC/Sch/2006)
文摘For a system of current interest（composed of charm, anticharm and a pair of light quarks）, we show trends in phenomenological implications of QCD-based improvements to a simple quark model treatment. We employ a resonating group method to render this difficult four-body problem manageable. We use a quadratic confinement so as to be able to improve beyond the Born approximation. We report the position of the pole corresponding to the D^0D^0＊ molecule for the best fit of a model parameter to the relevant QCD simulations. We point out the interesting possibility that the pole can be shifted to 3872 Me V by introducing another parameter I0 that changes the strength of the interaction in this one component of X（3872）. The revised value of this second parameter can guide future trends in modeling of the full exotic meson X（3872）. We also report the changes with I_0 in the S-wave spin averaged cross sections for D^0D^0＊-→ωJ/ψ and D^0D^0＊-→ρJ/ψ. These cross sections are important regarding the study of QGP（quark gluon plasma）.
基金Supported by DFG and NSFC through funds provided to the Sino-German CRC 110 “Symmetries and the Emergence of Structure in QCD”(NSFC(11621131001)DFG(TRR110))+4 种基金by NSFC(11647601)by the CAS Key Research Program of Frontier Sciences(QYZDBSSW-SYS013)by the Thousand Talents Plan for Young Professionalsby the CAS President’s International Fellowship Initiative(PIFI)(2017VMA0025)by Spanish Ministerio de Economía y Competitividad and European FEDER under contracts FIS2014-51948-C2-1-P and SEV-2014-0398
文摘The production of the X（3872） as a hadronic molecule in hadron colliders is clarified. We show that the conclusion of Bignamini et al., Phys. Rev. Lett. 103（2009） 162001, that the production of the X（3872） at high pT implies a non-molecular structure, does not hold. In particular, using the well understood properties of the deuteron wave function as an example, we identify the relevant scales in the production process.
基金Supported by the National Natural Science Foundation of China(11347030)the Program of Science and Technology Innovation Talents in Universities of Henan Province(14HASTIT037)。
文摘We study the Bc,u,d→X(3872)P decays in the perturbative QCD(PQCD)approach,involving the puzzling resonance X(3872),where P represents a light pseudoscalar meson(K orπ).Assuming X(3872)to be a 1++charmonium state,we obtain the following results.(a)The branching ratios of the Bc+→X(3872)π+and Bc+→X(3872)K+decays are consistent with the results predicted by the covariant light-front approach within errors;however,they are larger than those given by the generalized factorization approach.(b)The branching ratio of the B+→X(3872)K+decay is predicted as(3.8-1.0+1.1)×10-4,which is smaller than the previous PQCD calculation result but still slightly larger than the upper limits set by Belle and BaBar.Hence,we suggest that the B0,+→X(3872)K0,+decays should be precisely measured by the LHCb and Belle II experiments to help probe the inner structure of X(3872).(c)Compared with the Bu,d→X(3872)K decays,the Bu,d→X(3872)πdecays have significantly smaller branching ratios,which drop to values as low as 10-6.(d)The direct CP violations of these considered decays are small(10-3~10-2)because the penguin contributions are loop suppressed compared to the tree contributions.The mixing-induced CP violation of the B→X(3872)K0S decay is highly consistent with the current world average value sin 2β=(69.9±1.7)%.Experimentally testing the results for the branching ratios and CP violations,including the implicit SU(3)and isospin symmetries of these decays,helps probe the nature of X(3872).
基金the National Natural Science Foundation of China(Grant Nos.12075288,11735003,11961141012,12035007,11975041,and 11961141004)the Youth Innovation Promotion Association CAS,Guangdong Provincial Fund(Grant No.2019QN01×172)+2 种基金the Science and Technology Program of Guangzhou(Grant No.2019050001)supported by the the National Natural Science Foundation of Chinathe Deutsche Forschungsgemeinschaft(DFG,German Research Foundation)through the funds provided to the Sino-German Collaborative Research Center TRR110“Symmetries and the Emergence of Structure in QCD”(Grant Nos.12070131001 and ID 196253076-TRR 110)。
文摘We investigate the decays of B^(0)→K^(0)X(3872)and B^(+)→K^(+)X(3872)based on the picture where the X(3872)resonance is strongly coupled to the DD*+c.c.channel.In addition to the decay mechanism where the X(3872)resonance is formed from the DD*pair hadronization with the short-distance interaction,we have also considered the DD*rescattering diagrams in the long-distance scale,where D andD*are formed from c andDD*separately.Because of the difference of the mass thresholds of charged and neutralDD*channels,and the rather narrow width of the X(3872)resonance,at the X(3872)mass,the loop functions ofD^(0)D*^(0)andD^(+)D*^(-)are much different.Taking this difference into account,the ratio of B[B^(0)→K^(0)X(3872)]/B[B+→K+X(3872)]■0.5 can be naturally obtained.Based on this result,we also evaluate the decay widths of B_s^(0)→η(η′)X(3872).It is expected that future experimental measurements of these decays can be used to elucidate the nature of the X(3872)resonance.
基金Supported by the National Natural Science Foundation of China under Grant Nos. 10975184,11047117,11105222,and 11105223
文摘In this article, we test the nature of X（3872）, which is assumed to be a P-wave [cq]-scalar-diquark [cq]- axial-vector-antidiquark tetraquark state with JP = 2^-. The interpolating current representing the JP = 2^- state is proposed. Technically, contributions of the operators up to dimension six are included in the operator product expansion. The mass obtained for such state is m2- = （4.38±0.15） GeV. We conclude that it is impossible to describe the X（3872） structure as JV = 2^- tetraauark state.
