Production Of The Heavy-Flavor Hadrons At High-Energy Colliders

The interaction among quarks that are elementary particles of mattter is the strong interaction which is described Quantum Chromodynamics （QCD）. In the high-energy physics, the production and decay of heavy-flavor hadrons are an important window to understand the strong interaction, and they offer a significant platform to study perturbative QCD and non- perturbative QCD. Currently, the study of heavy-flavor hadrons has become one of the most important and interesting research fields of high energy physics, which is attracting wide and growing the concern of theoretical and experimental physicists. In the framework of Perturbative Quantum Chromodynamics （PQCD）, this thesis studies the production of two different types heavy-flavor hadrons B_s meson and doubly heavy baryon （?）_bc at high-energy colliders.We study the hadronic production B_s^（*）within the fixed-flavor-number scheme （FFNS） and the general-mass-variable-flavor-number scheme （GM-VFNS）, respectively. In high-energy hadron collider experiments, light partons （gluons and light quarks） distributions are the predominant inside hadrons within the FFNS, and subprocesses of the hadronic production only include the gluon-gluon fusion mechanism, light quark-antiquark annihilation, etc. However, in addition to light partons, heavy quarks should be considered in the initial state of the hard scattering subprocess in the GM-VFNS. Whether in the FFNS or in the GM-VFNS, it can be found that B_s^（*） hadronic production is dominated by the gluon-gluon fusion mechanism. Firstly, the dominant gluon-gluon fusion mechanism is dealt with by using the completeα_s⁴ approach in the FFNS, and the cross sections of B_s^（*） hadronic production at TEVATRON and LHC are presented. Then under the GM-VFNS, the gluon-gluon fusion mechanism and the heavy-quark mechanisms （mainly the intrinsic b quark） of B_s^（*） hadronic production are investigated, and the double counting problem is properly dealt with between the above two mechanisms. Numerical results show that the cross section of B_s^（*） hadronic production are extremely considerable at TEVATRON and LHC. In addition, we make a comparative study on the hadronic production of B_s^（*）under GM-VFNS and FFNS. The results show that there are large differences between two schemes in the small transverse momentum region, but they are consistent with those derived them in the large p_T region.At the same time, we quantitatively investigate the theoretical uncertainties for the B_s^（*） hadronic production in the hadronic colliders TEVATRON and LHC. Uncertainties of theoretical estimation involve parameters of B_s bound state such as the decay constant f_Bs, the constitute s-quark mass m_s ,the constitute b-quark mass m_b and B_s^（*） meson mass M_Bs; the parton distribution fuction; the QCD running coupling constant; factorization energy scale Q² and so on. Our results show that m_s greatly affects the total cross section, e.g. when it increases by steps of 0.1 GeV, the integrated cross section of B_s^（*） decreases by 80%–100%, and m_b effect is relatively smaller, e.g. when it increases by steps of 0.1 GeV, it only changes by ¹0%. While the uncertainties caused by the parton distribution function （PDF） and the factorization scale （ Q²） vary within the region of 1/5 to 1/3. To be more useful experimentally, considering many possible kinematic cuts on the transverse momentum and the rapidity cuts for the detectors at the TEVATRON and LHC, we present some related differential distribution curves, and also carefully discuss the effects cross section of B_s^（*） hadronic production by various kinematic cuts.On the other hand, taking into account prospects of the doubly heavy baryon （?）_bc of production and observation, we investigate the hadronic production of （?）_bc at the Large Hadron Collider （LHC）, and the cross section and related differential distribution curve of （?）_bc hadronic production are presented for the center-of-mass energy S^1/2=7TeV and S^1/2=14TeV. Numerical results show that under the condition of p^T＞4.0GeV and |y|＜1.5, sizable events （?）_bc about 1.7×10⁷and 3.5×10⁹ per year can be produced for the center-of-mass energy S^1/2=7TeV and S^1/2=14TeV, respectively. To be a valuable reference for the experimental physicist, the cross section of four diquark states （bc）_（3|-）[¹S₀]、（bc）₆[¹S₀]、（bc）₆[³S₁]、（bc）_（3|-）[³S₁] and total are presented and the related curves are drawn for the three main detectors CMS, ATLAS, LHCb under them actual conditions of kinematic cuts, respectively. The main uncertainties for the estimation have been discussed.Based on the above calculation, we make a simple comparison of the hadronic production of （?）_cc, （?）_bc , （?）_bb at the LHC. Numerical results indicate that relations of total cross sections of three baryons areσ（?）_cc＞σ（?）_bc＞σ（?）_bb under the condition of p_T＞4.0GeV and y|y|＜1.5, but the total cross section of （?）_bc is at the same order of that of （?）_cc and the differential cross section of （?）_bc will be dominant over that of （?）_cc when pT＞9.0GeV. From the above calculation and discussion, we can predict that there will be extremely considerable events （?）_bc produced at the LHC, and it is worth further theoretical and experimental study.