QCD corrections to Higgs-boson production at proton-proton colliders

Abstract

Gluon fusion is the ·main production mechanism for Higgs bosons with masses up to several hundred GeV in pp collisions at LHC and SSC. We present the QCD corrections to the fusion cross section for arbitrary Higgs and top mass valueso gg --+ H(g), gq --+ Hq and qq --+ Hg. The QCD corrections are positive and they increase the cross section cr(pp--+ H) by about a factor 1.5 to 1. 7. The analysis applies to the production of Higgs particles in the Standard Model and also to the production of the C'P-even Higgs particles in extensions of the Higgs sector as required for example by supersymmetric theories.Most of the building blocks of the Stan~d Model have been tested to a very high precision in recent years. However, the Higgs mechanism [1]; one of the cornerstones of this theory, has not yet been proven experimentally to be the basic mechanism for the generation of the fundamental particle masses. To accomodate the well-established electromagnetic and weak phenomena, this mechanism requires the existence of at least one weak isodoublet scalar field of which one degree of freedom manisfests itself as. a real physical particle for small enough masses. The discovery of the Higgs particle is the ezperimentum cntcis for the canonical formulation of the electroweak interactions. For Higgs boson masses up to ~700 GeV the dominant production mechanism in high-energy proton-proton collisions is gluon-gluon fusion (5]. The Higgs bosons couple to gluons through a heavy-quark triaugle loop. In this note we present the QCD corrections to the cross section u(pp--+H+X) of the fusion process, gg --+ H(g) and gq --+ Hq, qq --+ Hg( 1) for arbitrary Higgs boson and (loop] quark masses, Fig.1. This analysis extends previous work of Refs.[6] and (7] in which the Higgs boson mass was assumed to be much smaller than the looPquark mass. The analysis of the next-to-leading order QCD corrections to the Higgs production cross section is required for two reasons: (i) The lowest order prediction ofthe cross section u(pp --+ H) depends strongly on the renormalization and factorization scales. The next-to-leading order stabilizes the prediction and leaves us only with a mild residual dependence on these parameters.(ii) Since the QCD corrections turn out to be positive and large, the calculation is a posteriori also of high experimental significance. The transverse momentum spectra of the Higgs bosons have been considered at various levels of theoretical refinement in Refs.(S].Heavy quarks Q provide the dominant contribution to the coupling of Higgs bosons to gluons. Neglecting finite-width effects, the cross section for the production of Higgs particles in pp collisions is given to lowest order (Fig.1a) by (5,6,7] with <To f(Tq) dCgg <TLo(pp--+ H+X) =<ToTe-d Tgand d£99 / dTg denoting the gluon luminosity. The scaling variables are as usual defined by Tq = m~/4m~ and Tg = m~/s where ..(i is the total c.m. energy ofthe proton collider.The QCD corrections to the lowest order diagram (1a) consist of gluon-quark and Riggsquark vertex correc...

The measurement of the Higgs self-coupling at the LHC: theoretical status

“…[39]. They turn out to be quite large, almost doubling the production cross section at √ s = 14 TeV, in much the same manner as for single Higgs production [40][41][42][43][44][45][46]. In fact, the QCD corrections for single and double Higgs productions are intimately related and one should expect, as in the case of gg → H, a further increase of the total cross section by ≈ 30% once the next-to-next-to-leading (NNLO) corrections are also included [47][48][49].…”

“…[39]. The full LO expressions for F △ , F and G are used wherever they appear in the NLO corrections in order to improve the perturbative results, similar to what has been done in the single Higgs production case where using the exact LO expression reduces the disagreement between the full NLO result and the LET result [19][20][21][22][40][41][42][43][44][45][46].…”

“…They factorize in the Born term and in the NLO correction contributions, meaning that the K-factor is not strongly affected from any finite mass effects. Based on the results for the single Higgs case [40][41][42][43][44][45][46] where the deviation between the exact and asymptotic NLO results amounts to less than 7% for M H < 700 GeV, we estimate the error from applying an effective field theory approach for the calculation of the NLO corrections to 10%.…”

“…The process is known at NLO QCD in an effective field theory (EFT) approximation by applying the low energy theorem (LET) [40][41][42][43][44][45][46][93][94][95] which means that effective couplings of the gluons to the Higgs bosons are obtained by using the infinite quark mass approximation. The hadronic cross section at LO is given by…”

Differential cross section for Higgs boson production including all-orders soft gluon resummation

“…The fully inclusive gluon-gluon fusion subprocess [8,9] gg → hX is the dominant mechanism of production. In this process, production occurs through triangle loops of colored (s)particles that couple to the Higgs boson and to gluons.…”