The lepton number violation(LNV) process can be induced by introducing a fourth generation heavy Majorana neutrino,which is coupled to the charged leptons of the Standard Model(SM). There have been many previous studies on the leptonic number violating decay processes with this mechanism. We follow the trend to study the process: D→Kllπ with the same-sign dilepton final states. We restrict ourselves to certain neutrino mass regions,in which the heavy neutrino could be on-shell and the dominant contribution to the branching fraction comes from the resonance enhanced effect. Applying the narrow width approximation(NWA),we found that the upper limit for the branching fractions for D0→ K-l+l+π-are generally at the order of 10-12 to 10-9,if we take the most stringent upper limit bound currently available in the literature for the mixing matrix elements. We also provide the constraints,which is competitive compared to the LNV B decays,on the mixing matrix element |VeN|2 based on the upper limit of D0→ K-e+e+π-estimated from the Monte-Carlo(MC) study at BESⅢ. Although the constraints are worse than the ones from(0νββ) decay in the literature,the future experiment at the charm factory may yield more stringent constraints.
The number of ψ' events accumulated by the BESⅢ experiment from March 3 through April 14, 2009, is determined by counting inclusive hadronic events. The result is 106.41×(1.00±0.81%)×106 . The error is systematic dominant; the statistical error is negligible.
Data sets were collected with the BES detector at the BEPC collider at the center-of-mass energy of√s=3.650 GeV during May 2009 and at√s=3.773 GeV from January 2010 to May 2011.By analyzing the large angle Bhabha scattering events,the integrated luminosities of the two data sets are measured to be(44.49±0.02±0.44)pb 1and(2916.94±0.18±29.17)pb 1,respectively,where the first error is statistical and the second error is systematic.
Using data samples collected at center-of-mass energies of √s=4.009, 4.230, 4.260, and 4.360 Ge V with the BES detector operating at the BEPC collider, we perform a search for the process e+e-→γχc J(J =0, 1, 2)and find evidence for e+e-→γχc1 and e+e-→γχc2 with statistical significances of 3.0σ and 3.4σ, respectively. The Born cross sections σB(e+e-→γχc J), as well as their upper limits at the 90% confidence level(C.L.) are determined at each center-of-mass energy.
The beam energy measurement system is of great importance for both BEPC-Ⅱ accelerator and BES-III detector. The system is based on measuring the energies of Compton back-scattered photons. In order to meet the requirements of data taking and improve the measurement accuracy, the system has continued to be upgraded, which involves the updating of laser and optics subsystems, replacement of a view-port of the laser to the vacuum insertion subsystem, the use of an electric cooling system for a high purity germanium detector, and improvement of the data acquisition and processing subsystem. The upgrade system guarantees the smooth and efficient measurement of beam energy at BEPC-II and enables accurate offline energy values for further physics analysis at BES-Ⅲ.
The number of J/ψ events collected with the BES detector at the BEPC from June 12 to July 28, 2009 is determined to be (225.3 ± 2.8) × 10 6 using J/ψ→inclusive events, where the uncertainty is the systematic error and the statistical one is negligible.
麦迪娜M. N. AchasovD. J. Ambrose安芬芬安琪安正华白景芝班勇J. BeckerN. BergerM. Bertani边渐鸣E. BogerO. BondarenkoI. BoykoR. A. BriereV. Bytev蔡啸A. Calcaterra曹国富常劲帆G. Chelkov陈刚陈和生陈江川陈玛丽陈申见陈晔陈元柏程和平初元萍D. Cronin-Hennessy代洪亮代建平D. Dedovich邓子艳A. DenigI. DenysenkoM. Destefanis丁伟民丁勇董燎原董明义杜书先方建房双世L. FavaF. Feldbauer封常青R. B. Ferroli傅成栋傅金林高原宁耿聪K. Goetzen龚文煊W. GradlM. Greco顾旻皓顾运厅管颖慧郭爱强郭立波郭玉萍韩艳良郝喜庆F. A. Harris何康林何苗何振亚T. Held衡月昆侯治龙胡海明胡继峰胡涛黄彬黄光明黄金书黄性涛黄燕萍T. Hussain姬长胜纪全季晓斌季筱璐贾卢魁姜丽丽江晓山焦健斌焦铮金大鹏金山景繁凡N. Kalantar-NayestanakiM. KavatsyukW. Kuehn赖蔚J. S. Lange潘振声李春花李澄李翠李德民李飞李刚李海波李家才李康李蕾李宁博李秋菊李绍莉李卫东李卫国李晓玲李小男李学潜李秀荣李志兵梁昊梁勇飞梁羽铁廖广瑞廖小涛刘北江C. L. Liu刘春秀刘春燕刘福虎刘芳刘峰刘虎刘宏邦刘汇慧刘怀民刘红薇刘觉平刘魁勇刘凯刘坤刘佩莲刘树彬刘翔刘晓海刘勇刘豫斌刘振安刘志强刘智青H. Loehner鲁公儒吕海江吕军光
Recently, the LHCb experiment announced 3.5σ evidence for direct CP violation in D0 decay by looking at the difference between A CP (D0 → K+ K- ) and A CP (D0 →π+ π- ). This is the first evidence of CP violation in a charm system, which may indicate new physics beyond the Standard Model. Motivated by this measurement, we review rare processes in charmonium decay, especially, the weak decay, C or P violated decay, and lepton flavor violated decays. In case the new physics appears in charm sector, these rare decays of charmonium states will provide an opportunity to search for significant contributions from physics beyond the Standard Model. With huge J/ψ and ψ(2S) samples in BES experiment, the rare decays may be feasible.
While indirect and direct C P violation(CPV) has been established in the decays of strange and beauty mesons, no CPV has yet been found for baryons. There are different paths to finding C P asymmetry in the decays of strange baryons; they are all highly non-trivial. The Hyper CP Collaboration has probed CPV in the decays of singleΞ and Λ [1]. We discuss future lessons from e^+e^-collisions at BESⅢ/BEPCⅡ: probing decays of pairs of strange baryons, namely Λ, Σ and ■. Realistic goals are to learn about non-perturbative QCD. One can hope to find CPV in the decays of strange baryons; one can also dream of finding the impact of New Dynamics. We point out that an important new era will start with the BESIII/BEPCII data accumulated by the end of 2018. This also supports new ideas to trigger J/ψ→■Λ at the LHCb collaboration.
We study the heavy-light mesons in a relativistic model, which is derived from the Bethe-Salpeter equation by applying the Foldy-Wouthuysen transformation to the heavy quark. The kernel we choose is based on scalar confinement and vector Coulomb potentials. The transverse interaction of the gluon exchange is also taken into account in this model. The spectra and wave functions of D, D_s, B, B_s meson states are obtained. The spectra are calculated up to the order of 1/m Q, and wave functions are treated to leading order.
The beam energy is measured in the e+e-collision by using Compton backscattering. The uncertainty of this measurement process is studied by virtue of analytical formulas, and the special effects of variant energy spread and energy drift on the systematic uncertainty estimation are also studied with the Monte Carlo sampling technique. These quantitative conclusions are especially important for understanding the uncertainty of the beam energy measurement system.
