Study Of Exotic States And Search For ?'?Z' Invisible Decay At Bes?

Quantum Chromodynamics,the generally accepted theory for the strong interactions,describes the interactions between quarks and gluons.Due to the symptotic freedom,there are no rigorous,first-principle methods to derive the spectrum in the nonperturbative region.Instead,the lattice QCD and many "QCD inspired" phenomenological models are proposed.In the past twenty years,many exotic states,non-standard quark model prediction,are observed experimentally in the light,charm,and bottom quark energy regions.And they are the good candidates of multiquark states and quark-gluon hybrid states.What is certain is that,the spectroscopy of all but simplest hadrons is not yet fully understood.At present,BESIII has collected large data samples in charmonium energy region,exotic states,and conventional hadron states can be produced via e+e-collision directly and indirectly.BESIII can provide important experimental information for the understanding of the nature of the hadron state and hadron spectrum by searching and studying these hadron states.Furthremore,the discovery of the Higgs boson completes the last piece of the Standard Model,and also started a new era of particle physics.With more theoretical motivations and unexpected observations from astronomy and high-energy colliders,the existence of new physics beyond the Standard Model has been well recognized.To search for new physics signals or constrain new physical models,BESIII can use the high-statistic data in the charmonium energy region to indirectly search through the precise measurement of rare decays,or directly by searching for the possible decays of new physical particles.The e+e-???cJ(J=0,1,2)processes are studied at center-of-mass energies ranging from 3.773 to 4.600 GeV,using a total integrated luminosity of 19.3 fb-1 e+eannihilation data.We observe for the first time e+e-???c1,c2 signals at(?)?4.1 80 GeV with statistical significances of 7.6? and 6.0?,respectively.The production cross section of e+e-???c1,c2 at each center-of-mass energy is also measured.We find that the line shape of die e+e-???c1 cross section can be described with conventional charmonium states ?(3686),?(3770),?(4040),?(4160).Compared with this,for the e+e-???c2 channel,one more additional resonance is added to describe the cross section line shape.Its mass and width are measured to be M=4371.7±7.5±1.8 MeV/c2 and ?tot=51.1±17.6±1.9 MeV,where the first uncertainties are statistical and the second systematic.The significance of this resonance is estimated to be 5.8?,and its parameters agree with the Y(4360)resonance previously reported in e+e-??+?-?(3686),and the Y(4390)in e+e-??+?-hc within uncertainties.No significant signal for the e+e????c0 process is observed,and the upper limits of Born cross sections ?B(e+e-???c0)at 90%confidence level are reported.Based on 10 billion J/? events,the pp threshold structure has been studied in J/?radiative decays using the partial wave analysis method.There are a totally 1.3M clean J/???pp ypp events after background suppression.Based on the pp final state interaction effect used in the previous work,the partial wave analysis shows that the pp threshold structure has two resonance states,and the two resonance states assumption is better than only one resonance state with the significance of 19.6?.On the assumption that one of the resonance states is X(1835),the measured parameters of another resonance are consistent with the parameters of X(1870),which is observed in the process of J/????+?-?'.This conclusion supports the existence of pp bound state in the pp threshold structure.However,since the current statistics need to estimate the uncertainty of the final state interaction effect carefully,this conclusion needs to be further studied.We report a search for invisible decays of the dark photon using a 14.9 fb-1 data sample taken at center-of-mass energies from 4.13 GeV to 4.60 GeV.In this work,the signal process only has one final photon with large missing energy taken by dark photon.Considering the trigger efficiency and saturation effect of electromagnetic calorimeter electronics,the dark photon is searched with masses between 1.5?2.9 GeV.There is no obvious signal of dark photon candidate,and the upper limit of the mixing parameter are measured within 1.6-5.7×10-3 at the 90%confidence level.Based on 10 billion J/? event,Z'0,l invisible decay is searched in the J/???+?-Z'0,1,Z'0,1? invisible process.The Z'0,1 particle is a new physical particle proposed to explain the long-standing difference between theory and experiment about g-2 anomaly.Under 10%J/? data,we performed a semi-blind analysis to search for Z'0,1 in the range of M(Z'0,1)<1.8 GeV.No obvious excess is observed in the data.Finally,the upper limits of the coupling constant are given at the 90%confidence level.This upper limit is about 2 orders of magnitude lower than the previous results from Belle ?.