Study On The Indirect Production Mechanism Of The Doubly Heavy Hadrons At The High Energy Colliders

In particle physics,the high energy collider is one of the effective ways to explore and search for the 'new physics' mechanism beyond the standard model.The high energy colliders can provide experimental evidences to understand the micro world.Quarks exist as hadrons due to the quark confinement and the fractional charge of quarks in strong interactions.Many hadronic states have been found experimentally so far,especially the doubly charm baryons discovered by the LHCb experimental group of China in 2017.The abundant physical information of doubly heavy hadrons makes them one of the main topics in the study of QCD.Since other doubly heavy baryons,i.e.,?bc and ?bb,predicted by the quark model have not been found till now,this paper is devoted to study the production mechanisms of doubly heavy baryons and to analyzed the produced events at the high energy colliders.In addition,the discovery of heavy quarkonium is relatively early and its research is comprehensive,we try to start with the heavy quarkonium and seek for possible new physics with the help of the golden platform of flavor change neutral currents(FCNC).In the present paper,we analyzed some physics processes for the indirectly production of doubly heavy baryons at the high energy colliders in the framework of NRQCD.Firstly,we introduce two different methods:fixed-order calculation and fragmentation function,and then present the theoretical results for the production of doubly heavy hadrons,including the decay widths and differential distributions.Then we discussed the theoretical uncertainties caused by the heavy quark masses,the renormalization scale,and the transition matrix elements.This paper includes the following three research work:?We investigate the production of doubly heavy baryons via the process of top quark decays t ?bQ,+(?)'+W+,where Q' stands for the heavy quark c or b.It can be seen that the results at leading order obtained by the fixed-order calculation and the fragmentation function method are consistent with each other.Thus,the fragmentation function method is also an effective and feasible method to deal with the production of doubly heavy baryons.Moreover,in the fragmentation function method,a resummation has been done by using the DGLAP equation,which can evolve the factorization scale at the same time.This evolution resums the high order logarithmic contributions to obtain more precise behaviors for the energy fraction differential distributions.The decay width for the production of doubly heavy baryons through top quark decays a is relatively large,so enough events of doubly heavy baryons can be produced at the high energy colliders to be analyzed in future experiments.?We present the correlated process of Higgs boson decays through four main Higgs decay channels,H0?b(?),c(?),Z0Z0 and gg.These Higgs decay channels play an important role in Higgs physics.We did a relatively complete analysis for the production of doubly heavy baryons ?cc,?bc?and ?bb.The contributions from the intermediate diquark states,<cc>[1S0]6,<cc>[3S1](?),<bc>[3S1](?)/6,<bc>[1S0](?)/6,<bb>[1S0]6 and<bb>[3S1](?),have been taken into consideration.We can see that at the high energy colliders,there would be enough events of doubly heavy baryons produced through Higgs boson decays,which would be a good platform to investigate the production of doubly heavy baryons.?The rare decay of top quark has been discussed via the processes involving FCNC.We calculate the decay widths,invariant mass and angular differential distributions for the production of heavy charmonium(?c,J/?)and(c(?))-quarkonium(Bc,Bc*).In addition,we analyzed the background of this process with the same initial and final states,but without FCNC.The corresponding results of this background process are about 105?6 larger than the expected FCNC signal.Thus,it is difficult to detect FCNC effect in standard model through this process in future experiments,and a more rigorous events selection scheme is needed.Finally,we estimated the new physics effects in some new physical models.