Yu-Jie Zhang

Yields and polarizations of prompt J/ψ and ψ(2S) production in hadronic collisions

A bstractWe give predictions of J/ψ and ψ(2S) yields and polarizations in prompt production at hadron colliders based on non-relativistic QCD factorization formula. We calculate short-distance coefficients of all important color-octet intermediate channels as well as color-singlet channels up to OαS4

Reduction schemes in cutoff regularization and Higgs decay into two photons

\mathcal{O}\left({\alpha}_S^4\right)

Relativistic correction to J/ψ and \varUpsilon pair production

, i.e. next-to-leading order in αS. For prompt J/ψ production, we also take into account feeddown contributions from χcJ (J=0,1,2) and ψ(2S) decays. Color-singlet long-distance matrix elements (LDMEs) are estimated by using potential model, and color-octet LDMEs are extracted by fitting the Tevatron yield data only. The predictions are satisfactory for both yields and polarizations of prompt J/ψ and prompt ψ(2S) production at the Tevatron and the LHC. In particular, we find our predictions for polarizations of prompt J/ψ production have only a little difference from our previous predictions for polarizations of direct J/ψ production.

ϒ ( n S ) and χ b ( n P ) production at hadron colliders in nonrelativistic QCD

We study Feynman rules for the rational part R of the Standard Model amplitudes at one-loop level in the ’t Hooft-Veltman γ5 scheme. Comparing our results for quantum chromodynamics and electroweak 1-loop amplitudes with that obtained based on the Kreimer-Korner-Schilcher (KKS) γ5 scheme, we find the latter result can be recovered when our γ5 scheme becomes identical (by setting g5s = 1 in our expressions) with the KKS scheme. As an independent check, we also calculate Feynman rules obtained in the KKS scheme, finding our results in complete agreement with formulae presented in the literature. Our results, which are studied in two different γ5 schemes, may be useful for clarifying the γ5 problem in dimensional regularization. They are helpful to eliminate or find ambiguities arising from different dimensional regularization schemes.

Feynman rules for the rational part of one-loop QCD corrections in the MSSM

Abstract: The Higgs boson decay into two photons in the Standard Model is reevaluated in conventional ultraviolet cutoff regularization. In unitary gauge, the same expression as that of R. Gastmans et al. is obtained on condition that the same momenta configuration in the W-boson loop is adopted. Whereas in ’t HooftFeynman gauge, the contribution of the W-boson loop to this process is found to be the same as that obtained in dimensional regularization, and this reconfirms the indication pointed out by M. Shifman et al. that the triangle diagram of W-boson’s Goldstone contributes a term that violates the decoupling theorem. Aside from the W-boson loop, the top-quark loop is also studied and found to give consistent results in cutoff and dimensional regularization. We then reanalyze the Lagrangian in unitary gauge and find the absence of large momentum modes in cutoff regularization may be responsible for the inconsistency in the treatment of R. Gastmans et al.. In doing the complex calculations, we have derived a general recursive relation and implemented it in the Passarino-Veltman reduction formula.A bstractWe present a new systematic method to evaluate one-loop tensor integrals in conventional ultraviolet cutoff regularization. By deriving a new recursive relation that describes the momentum translation variance of ultraviolet integrals, we implement this relation in the Passarino-Veltman reduction method. With this method, we recalculate the Higgs boson decay into two photons at one-loop level in the Standard Model. We reanalyze this process carefully and clarify some issues arisen recently in cutoff regularization.

s v 2 corrections toc andcJ production recoiled with a photon at e + e − colliders

The relativistic corrections to the color-octet

Search for

J/\psi

C=+

hadroproduction at the Tevatron and LHC are calculated up to