Next-to-leading-order QCD corrections to e + e − → H + γ

Abstract

Within the nonrelativistic QCD (NRQCD) factorization framework, we have computed the O(α 2 s) corrections to the exclusive production of P-wave spin-triplet charmonia χ cJ (J = 0, 1, 2) accompanied with a hard photon at B factory. For the first time, we have explicitly verified the validity of NRQCD factorization for exclusive Pwave quarkonium production to two-loop order. Unlike the χ cJ electromagnetic decays, the O(α 2 s) corrections are found to be smaller than the O(α s) corrections in all three channels e + e − → χ c0,1,2 + γ. In particular, the O(α 2 s) corrections appear moderate for χ c1 + γ case, and marginal for χ c0 + γ. Moreover, the predictions in next-to-next-to-leading order (NNLO) accuracy for the production rates of χ c0,1 + γ are insensitive to the renormalization and factorization scales. All of these features may indicate that perturbative expansion in these two channels exhibits a decent convergence behavior. By contrast, both the O(α s) and O(α 2 s) corrections to the χ c2 + γ production rate are sizable, which reduces the Born order cross section by one order of magnitude after including the NNLO perturbative corrections. Taking the values of the long-distance NRQCD matrix elements from nonrelativistic potential model, our prediction to χ c1 + γ production rate is consistent with the recent Belle measurement. The NNLO predictions to the χ c0,2 + γ production rates are much smaller than that for χ c1 + γ, which seems to naturally explain why the e + e − → χ c0,2 + γ channels have escaped experimental detection to date.

Single Higgs production in association with a photon at electron-positron colliders in extended Higgs models

“…For the ITM we newly implemented the relevant pieces, based on the IDM. We validated our numerical calculations by comparing with the earlier works in the SM [7,9] as well as in the IDM [19], while the results in the ITM and the THDMs are reported for the first time in this article.…”

“…We briefly review the total cross section for e + e − → hγ in the SM [6][7][8][9]. As mentioned in Sec.…”

“…For the hypercharge Y = 1 case, however, most of the parameter space is already excluded by the direct detection experiments due to the Z-mediated tree-level scattering [43,44]. 9 Here, we consider the ITM with Y = 1 as a benchmark model just to describe new physics effects on the e + e − → hγ processes.…”

“…The next-to-leading-order QCD corrections were recently estimated in Ref. [9], which shows negligible impact at lower center-of-mass energies √ s < 300 GeV. On the other hand, new physics effects on the process have not been fully explored yet.…”

Loop induced singlet scalar production through the vector like top quark at future lepton colliders

“…The next-to-leading order QCD corrections to the production of a Higgs boson associated with a photon has been calculated in Ref. [61], where it has been shown that these corrections could increase the production rate up to 20%. Within the simplified model, the e − e + → h 2 γ process proceeds through loop-level Feynman diagrams which include SM fermions and gauge bosons as well as the additional contributions from the vector like top quark.…”