Study Of The P-wave B_c Meson Production At LHeC

In this thesis we have studied the production of the P-wave excited Bc**states(1P1 and 3PJ with J = 0,1,2)via photoproduction mechanism within the framework of non-relativistic QCD(NRQCD)at the Large Hadron Electron Collider(LHeC)and Future Circular Collider-based electron-proton collider(FCC-ep).The LHeC and the FCC-ep are the newly proposed electron-proton colliders,which combine the advantages of hadron colliders and lepton colliders,i.e.,powerful colliding energy,high luminosity and clean background.Thus these colliders can be good plantforms to study the Bc meson properties.The doubly heavy mesons are helpful for studying both the perturbative and non-perturbative features of quark-antiquark bound states.The heavy constituent quarks move nonrelativistically in those systems,which can be well understood within the framework of NRQCD.Among the doubly heavy mesons,the B,meson,being a(cb)-quarkonium state,is unique.It decays mainly via weak interaction and has a relatively long lifetime,thus provides a fruitful laboratory for testing the QCD potential model and understanding the weak-decay mechanism of heavy flavors.The Bc meson was first observed by CDF collaboration in 1998,and many exper-imental studies,especially at the Large Hadron Collider(LHC),have resulted in series of achievements in the last decade.At the same time,theoretical predictions have also been updated.There are many works on the production of the Bc meson and its excited states at hadron colliders either directly via the dominant gluon-gluon fusion and etc.,or indirectly via the top-quark,Higgs and W-boson decays.The Bc meson production at a high luminosity e+e-collider running around the Z0-boson threshold(the so-called su-per Z factory)or at the proposed International Linear Collider(ILC)via photon-photon fusion have been analyzed.Those studies indicate that sizable Bc meson events can be generated on various platforms.At present,the hadron colliders have accumulated enough Bc meson events for its discovery,but we still need more data for a better understanding of its detailed proper-ties.It is interesting to show whether there are any other kind of colliders which also have the ability to generate sizable Bc meson events.In addition to the hadron collid-ers,the lepton-hadron collider may also be an important machine to probe the Bc meson properties.The Hadron-Electron Ring Accelerator(HERA)is the first such kind of machine,at which the electrons of 27.5 GeV colliding with the protons of energy up to 0.92 TeV.Analyses of the elastic and proton dissociative photoproduction and the inelastic photoproduction of the J/? meson were reported by the H1 Collaboration.However,no Bc-meson event was reported there,which is mainly due to its low luminosity L?1031 cm-2s-1 and low colliding energy.Recently,a new lepton-proton collider,namely the LHeC(or its successor FCC-ep),has been proposed.It is designed to use a newly built electron beam of 60 GeV(to possibly 140 GeV)to collide with the intense 7 TeV protons at the LHC.We inves-tigate the production of the P-wave excited Bc**states(1P1 and 3PJ with J = 0,1,2)via photoproduction mechanism within the framework of NRQCD at the LHeC.Gen-erally,the e + P ?? + g? Bc**+ b + c process is considered as the main pro-duction mechanism at an electron-proton collider due to the large luminosity of the gluon.However,according to the results on the S-waveBc(*)meson production at the LHeC,the extrinsic production mechanism,i.e.,e-+ P??+c ?Bc**+ b and e-+P?+ b?Bc**+ c,could also provide dominating contributions at low pT region.A careful treatment between these channels is performed and the results on total and differential cross sections,together with main uncertainties are discussed.Taking the quark masses mb ? 4.90 ± 0.40 GeV and mc = 1.50 ± 0.20 GeV into account and summing up all the production channels,we expect to accumulate(?)and(?)(?)events at the(?)TeV LHeC in one operation year with luminosity(?).With such sizable events,it is worth to study the properties of excited P-wave Bc**states at the LHeC.The main innovation in this thesis is:· We give a systematic study of the P-wave Bc**production at the LHeC within the framwork of NRQCD for the first time.We find that the production of P-wave Bc**can contribute about 20%to S-wave Bc production at the LHeC and FCC-ep,which could not be negelcted.Moveover,sizable Bc**events which can be producted indicate that people may directly measure the P-wave states at the LHeC or FCC-ep,and thus it is helpful in understanding the mass spectrum of(cb)bound states and testing the potential model.