BABAR has measured with unprecedented accuracy the e^＋e^- → pp and e^＋e^- →∧∧ cross sections by means of the initial state radiation technique, which has the advantages of good efficiency, good energy resolution...BABAR has measured with unprecedented accuracy the e^＋e^- → pp and e^＋e^- →∧∧ cross sections by means of the initial state radiation technique, which has the advantages of good efficiency, good energy resolution and full angular acceptance, even exactly at threshold. A peculiar feature of these cross sections is their non-vanishing values at threshold. In the case of charged baryons, this phenomenon is expected according to the Coulomb interaction between the outgoing baryon and antibaryon. Once this Coulomb enhancement factor is taken into account, the striking result is achieved that the proton form factor at threshold is ｜GP（4Mp^2）｜ = 1, that is what is expected for pointlike fermion pairs, in spite of the proton structure. However a Coulomb enhancement factor is not expected for neutral fermions, likely in contradiction with the BABAR data. Qualitatively this behaviour is consistent with Coulomb interactions at the valence quark level.展开更多
The cross sections for e^＋e^- →π^＋ π^-J/ψ, π^＋π^-ψ（2S）, K^＋K^-J/ψ, DD1D^0D1-π^＋ ＋c.c., D^＊D＋c.c., and D^＊D^＊ are measured using data sample collected on or near the T（4S） resonance with the Bell...The cross sections for e^＋e^- →π^＋ π^-J/ψ, π^＋π^-ψ（2S）, K^＋K^-J/ψ, DD1D^0D1-π^＋ ＋c.c., D^＊D＋c.c., and D^＊D^＊ are measured using data sample collected on or near the T（4S） resonance with the Belle detector at KEKB. A peak near 4.25 GeV/c^2, corresponding to the so called Y（4260）, is observed in π^＋π^-J/ψ final state. In addition, there is another cluster of events at around 4.05 GeV/c^2. Two resonant structures are observed in the π^＋π^-ψ（2S） invariant mass distribution, one at 4361±9±9 MeV/c^2 with a width of 74±15±10 MeV/c2, and another at 4664 ±11±5 MeV/c2 with a width of 48±15±3 MeV/c^2. The rich structures observed in all these final states indicate that our understanding of the vector charmonium states above the open charm threshold is still poor, let alone the other possible dynamics such as charmonium hybrids or final state re-scattering and so on.展开更多
The paper reports an analytical formula for the production cross section of e^(+)e^(−)annihilation to hadrons in the vicinity of a narrow resonance,particularly in theτ-charm region,while considering initial state ra...The paper reports an analytical formula for the production cross section of e^(+)e^(−)annihilation to hadrons in the vicinity of a narrow resonance,particularly in theτ-charm region,while considering initial state radiation.Despite some approximations in its derivation,comparison between the analytical formula and direct integration of ISR shows good accuracy,indicating that the analytical formula meets current experimental requirements.Furthermore,this paper presents a comparison of the cross section between the analytical formula and calculations using the ConExc Monte Carlo generator.The efficiency of the analytical formula in significantly reducing computing time makes it a favorable choice for the regression procedure to extract the parameters of narrow charmonium resonances in experiments.展开更多
Initial State Radiation(ISR)plays an important role in e+e−collision experiments such as the BESIII.To correct the ISR effects in measurements of hadronic cross-sections of e+e−annihilation,an iterative method that we...Initial State Radiation(ISR)plays an important role in e+e−collision experiments such as the BESIII.To correct the ISR effects in measurements of hadronic cross-sections of e+e−annihilation,an iterative method that weights simulated ISR events is proposed here to assess the efficiency of event selection and the ISR correction factor for the observed cross-section.The simulated ISR events were generated only once,and the obtained cross-sectional line shape was used iteratively to weigh the same simulated ISR events to evaluate the efficiency and corrections until the results converge.Compared with the method of generating ISR events iteratively,the proposed weighting method provides consistent results,and reduces the computational time and disk space required by a factor of five or more,thus speeding-up e+e−hadronic cross-section measurements.展开更多
We present a search for new charmonium like states in e^＋e^- annihilation using the initial-state radiation and the process e^＋e^- →J/ψ D（^＊）D（^＊）. The analyses are based on a huge data sample recorded near ...We present a search for new charmonium like states in e^＋e^- annihilation using the initial-state radiation and the process e^＋e^- →J/ψ D（^＊）D（^＊）. The analyses are based on a huge data sample recorded near the T（4S） resonance with the Belle detector at the KEKB e^＋e^- asymmetric-energy collider.展开更多
The KLOE experiment at the φ-factory DAФPNE has measured the pion form factor in the range between 0.1 〈 Mππ^2 〈 0.85 GeV^2 using events taken at √s = 1 GeV with a photon emitted at large polar angles in the in...The KLOE experiment at the φ-factory DAФPNE has measured the pion form factor in the range between 0.1 〈 Mππ^2 〈 0.85 GeV^2 using events taken at √s = 1 GeV with a photon emitted at large polar angles in the initial state. This measurement extends the Mππ^2 region covered by KLOE ISR measurements of the pion form factor down to the two pion production threshold. The value obtained in this measurement of the dipion contribution to the muon anomalous magnetic moment of △αμ^ππ= （478.5±2-0stat±4.8syst±2.9theo）·10^-10 further confirms the discrepancy between the Standard Model evaluation for αμ and the experimental value measured by the （g-2） collaboration at BNL.展开更多
A detailed theoretical derivation of the cross sections of e^＋e^-→e^＋e^-and e^＋e^-→μ＋μ-around the J/ψ resonance is reported. The resonance and interference parts of the cross sections, related to J/ψ resonan...A detailed theoretical derivation of the cross sections of e^＋e^-→e^＋e^-and e^＋e^-→μ＋μ-around the J/ψ resonance is reported. The resonance and interference parts of the cross sections, related to J/ψ resonance parameters, are calculated. Higher-order corrections for vacuum polarization and initial-state radiation are considered. An arbitrary upper limit of radiative correction integration is involved. Full and simplified versions of analytic formulae are given with precision at the level of 0.1% and 0.2%, respectively. Moreover, the results obtained in the paper can be applied to the case of the ψ（3686） resonance.展开更多
文摘BABAR has measured with unprecedented accuracy the e^＋e^- → pp and e^＋e^- →∧∧ cross sections by means of the initial state radiation technique, which has the advantages of good efficiency, good energy resolution and full angular acceptance, even exactly at threshold. A peculiar feature of these cross sections is their non-vanishing values at threshold. In the case of charged baryons, this phenomenon is expected according to the Coulomb interaction between the outgoing baryon and antibaryon. Once this Coulomb enhancement factor is taken into account, the striking result is achieved that the proton form factor at threshold is ｜GP（4Mp^2）｜ = 1, that is what is expected for pointlike fermion pairs, in spite of the proton structure. However a Coulomb enhancement factor is not expected for neutral fermions, likely in contradiction with the BABAR data. Qualitatively this behaviour is consistent with Coulomb interactions at the valence quark level.
基金National Natural Science Foundation of China(10775142)and 100 Talents Program of CAS(U-25)
文摘The cross sections for e^＋e^- →π^＋ π^-J/ψ, π^＋π^-ψ（2S）, K^＋K^-J/ψ, DD1D^0D1-π^＋ ＋c.c., D^＊D＋c.c., and D^＊D^＊ are measured using data sample collected on or near the T（4S） resonance with the Belle detector at KEKB. A peak near 4.25 GeV/c^2, corresponding to the so called Y（4260）, is observed in π^＋π^-J/ψ final state. In addition, there is another cluster of events at around 4.05 GeV/c^2. Two resonant structures are observed in the π^＋π^-ψ（2S） invariant mass distribution, one at 4361±9±9 MeV/c^2 with a width of 74±15±10 MeV/c2, and another at 4664 ±11±5 MeV/c2 with a width of 48±15±3 MeV/c^2. The rich structures observed in all these final states indicate that our understanding of the vector charmonium states above the open charm threshold is still poor, let alone the other possible dynamics such as charmonium hybrids or final state re-scattering and so on.
文摘The paper reports an analytical formula for the production cross section of e^(+)e^(−)annihilation to hadrons in the vicinity of a narrow resonance,particularly in theτ-charm region,while considering initial state radiation.Despite some approximations in its derivation,comparison between the analytical formula and direct integration of ISR shows good accuracy,indicating that the analytical formula meets current experimental requirements.Furthermore,this paper presents a comparison of the cross section between the analytical formula and calculations using the ConExc Monte Carlo generator.The efficiency of the analytical formula in significantly reducing computing time makes it a favorable choice for the regression procedure to extract the parameters of narrow charmonium resonances in experiments.
基金The material presented in this paper is by the authors alone,and has not been reviewed by the BESIII Collaboration.However,we thank our colleagues for allowing us to make use of the BESIII software environment.This work was supported by the National Natural Science Foundation of China,under Grant Nos.U1732105,U1632106,11947415,and 12047569 and the Research Foundation for Advanced Talents of Nanjing Normal University,under Grant No.2014102XGQ0085.We also appreciate valuable discussions with Dr.Kai Zhu,Dr.Yuping Guo,and Prof.Changzheng Yuan.
文摘Initial State Radiation(ISR)plays an important role in e+e−collision experiments such as the BESIII.To correct the ISR effects in measurements of hadronic cross-sections of e+e−annihilation,an iterative method that weights simulated ISR events is proposed here to assess the efficiency of event selection and the ISR correction factor for the observed cross-section.The simulated ISR events were generated only once,and the obtained cross-sectional line shape was used iteratively to weigh the same simulated ISR events to evaluate the efficiency and corrections until the results converge.Compared with the method of generating ISR events iteratively,the proposed weighting method provides consistent results,and reduces the computational time and disk space required by a factor of five or more,thus speeding-up e+e−hadronic cross-section measurements.
文摘We present a search for new charmonium like states in e^＋e^- annihilation using the initial-state radiation and the process e^＋e^- →J/ψ D（^＊）D（^＊）. The analyses are based on a huge data sample recorded near the T（4S） resonance with the Belle detector at the KEKB e^＋e^- asymmetric-energy collider.
文摘The KLOE experiment at the φ-factory DAФPNE has measured the pion form factor in the range between 0.1 〈 Mππ^2 〈 0.85 GeV^2 using events taken at √s = 1 GeV with a photon emitted at large polar angles in the initial state. This measurement extends the Mππ^2 region covered by KLOE ISR measurements of the pion form factor down to the two pion production threshold. The value obtained in this measurement of the dipion contribution to the muon anomalous magnetic moment of △αμ^ππ= （478.5±2-0stat±4.8syst±2.9theo）·10^-10 further confirms the discrepancy between the Standard Model evaluation for αμ and the experimental value measured by the （g-2） collaboration at BNL.
基金Supported by National Natural Science Foundation of China(11275211)Istituto Nazionale di Fisica Nucleare,Italy
文摘A detailed theoretical derivation of the cross sections of e^＋e^-→e^＋e^-and e^＋e^-→μ＋μ-around the J/ψ resonance is reported. The resonance and interference parts of the cross sections, related to J/ψ resonance parameters, are calculated. Higher-order corrections for vacuum polarization and initial-state radiation are considered. An arbitrary upper limit of radiative correction integration is involved. Full and simplified versions of analytic formulae are given with precision at the level of 0.1% and 0.2%, respectively. Moreover, the results obtained in the paper can be applied to the case of the ψ（3686） resonance.
