Studies On Production Mechanisms Of Doubly Heavy Hadron Based On The NRQCD Theory

In the present paper, we make theoretical investigations in detailed for the productions of heavy quarkonium and doubly heavy baryon at the high energy colliders, based on the framework of pertrubative Quantum Chromodynamics(p QCD) and non-relativistic Quantum Chromodynamics(NRQCD). Explicitly, the charmonium production at the B and super-Z factory are discussed, and the photoproduction of heavy quarkonium at the International Linear Collider(ILC) are presented. Moreover, several dominant production channels in the hadronicproduction of doubly heavy baryon at the After@LHC are also studied.We make a comparative and comprehensive study on the charmonium exclusive productions at the e e+ - collider with the collision energy either round the 0Z-boson mass for a super Z factory or equals to 10.6 Ge V for the B factories as Belle and BABAR. We study the total cross sections for the charmonium production via the exclusive processes * 01 2e e g/ Z H H+ -® ® + and * 01 e e g/ Z H g+ -® ® +, where 1H and 2H represent the dominant color-singlet S-wave and P-wave charmonium states respectively. Total cross sections versus the e e+ - collision energy s, together with their uncertainties, are presented, which clearly show the relative importance of these channels. At the B factory, the production channels via the virtual *g propagator are dominant over the channels via the 0Z propagator by about four orders. While, at the super Z factory, due to the 0Z-boson resonance effect, the 0Z boson channels shall provide sizable or even dominant contributions in comparison to the channels via the *g propagator. Sizable exclusive charmonium events can be produced at the super Z factory with high luminocity up to 36 2 110 cm s- -, especially for the channel of 01 e e Z H g+ -® ® +. As an important step forward, in the present paper, we present a next-to-leading order(NLO) QCD analysis within the framework of nonrelativistic QCD. Estimations up to NLO level are done under the condition of both the B factories and the super Z factory. We observe that the NLO distributions have the same shapes as those of LO distributions, but their differences are sizable. This indicates that a NLO calculation is necessary and important to achieve a more accurate estimation.We study the photoproduction of the heavy quarkonium at the future International Linear Collider(ILC) within the nonrelativistic QCD theory. We focus on the production channel via the subprocess gg ®| [QQ￠](n)? +Q￠ +Q1, where Q and Q’ stand for heavy c- or b-quark, respectively. | [QQ￠](n)?1 stands for color-single S-wave quarkonium, i.e., 10(| [ ]())chcc S ?1, 31 J y(| [cc]( S)?)1, 10(| [ ]())cB cb S ?1, * 31(| [ ]())cB cb S ?1, 10(| [ ]())bhbb S ?1, and 31?(| [bb]( S)?)1, respectively. To improve the calculation efficiency, we adopt the improved helicity amplitude approach to deal with the difficulty of calculating the expressions for the yields when the quark masses cannot be neglected. Total and differential photoproduction cross sections, together with their uncertainties, have been presented. It is noted that sizable amount of | cc ?-charmonium and | cb ?-quarkonium events can be generated at the ILC. More specifically, we predict 1.0 60.7(2.8) 10ch+-′, 1.9 61.3(5.4) 10 J y+-′, 2.2 41.8(8.3) 10cB+-′, 1.1 5 *0.9(4.3) 10cB+-′, 1.7 31.4(9.0) 10bh+-′, and 4(1.6 ±0.3) ′10 ? events to be generated in one operation year at the ILC under the condition of S =500 Ge V and 36 2 110 cm s- -.Due to the doubly heavy baryon contains two constituent(the same or different flavor) heavy quarks and a light quark(u, d, or s), we’ll encounter more complexity and difficulty in theorital study. Consequently, there are still many puzzles and challenge in theoretical comprehending about the production mechanism and properties of doubly heavy baryon. In the paper, we present a detailed discussion on the cc? production at a fixed-target experiment at the LHC(After@LHC). The doubly charmed baryon cc? is produced via the channel, ccpp ? ? ?X. In estimating its hadroproduction, we discuss three dominant subprocesses, e.g., ccg ?g ? ? ?c ?c, ccg ?c ? ? ?c, and ccc ?c ? ? ?g. Our numerical results indicate that, in addition to SELEX and LHC, the After@LHC shall provide another useful platform for studying the baryon properties. Moreover, we make a detailed study on the doubly heavy baryon photoproduction in the future e e? ? International Linear Collider(ILC). The baryons cc?, bc?, and bb? are produced via the channel QQ??Q Q?? ? ???, where Q and Q’ stand for heavy c or b quark, respectively. According to the non-relativistic QCD theory, four diquark configurations shall provide sizable contributions to the baryon production, e.g., [n] equals 31[ S]3, 10[ S]6, 31[ S]6, or 10[ S]3, respectively. Total and differential cross sections of those channels, as well as the theoretical uncertainties, are presented. We show that sizable amounts of baryon events can be generated at the ILC.