Largep T double photon production in hadronic collisions-beyond leading logarithm QCD calculation

Abstract

Abstract. We calculate O(c~s) corrections to large Pr double photon production in hadronic collisions. We find that these corrections to the basic qq ~ 77 subprocess are important, preventing to describe double photon production on the basis of the leading logarithm approximation only. We give a phenomenological discussion of the results obtained at SPS, ISR and SpOS energies. In particular, we investigate how the effect of the intrinsic parton < ~c r) may be disentangled from the perturbative contribution. We also calculate the aplanarity distribution characteristic of 3 jet events.

Photon plus jet cross sections in deep inelastic ep collisions at order O(α2α)

“…This sensitivity is known from similar calculations of dijet cross sections in ep collisions [25] and must be avoided. The same problem was encountered in the calculation of inclusive two-jet cross sections in γp collisions [26], for the production of a prompt photon plus a charm quark in pp collisions [24] and much earlier in NLO calculations of the inclusive cross section for photon-hadron [3] and for two-photon production [27].…”

Maximal unitarity at two loops

“…An example is the gluon fusion to diphoton subprocess, gg → γγ, which is an important background to searches for the Higgs boson at the LHC. Although this subprocess is nominally suppressed by a power of the strong coupling α s , the large gluon parton density at smaller x can compensate for this additional power, giving rise to contributions to cross sections which are comparable to those from tree-level quark-initiated subprocesses [30][31][32]. Other examples include production of electroweak boson pairs, gg → Zγ, ZZ, W + W − .…”

Higgs Production with Large Transverse Momentum in Hadronic Collisions at Next-to-Leading Order

“…This conclusion depends on the value of the K-factor (a conservative value K=1.5 was used) and some plausible assumptions on the size of the background. The calculation of the next-to-leading order (NLO) corrections to the background is not yet complete [3] and the contribution of the NNLO subprocess gg → γγ is large [4]. The complete NNLO analysis is extremely laborious, but appears to be feasible.…”