Higgs pair production at the LHC with NLO and parton-shower effects

Abstract

We present predictions for the SM-Higgs-pair production channels of relevance at the LHC: gluon-gluon fusion, VBF, and top-pair, W, Z and single-top associated production. All these results are at the NLO accuracy in QCD, and matched to parton showers by means of the MC@NLO method; hence, they are fully differential. With the exception of the gluon-gluon fusion process, for which a special treatment is needed in order to improve upon the infinite-top-mass limit, our predictions are obtained in a fully automatic way within the publicly available MadGraph5_aMC@NLO framework. We show that for all channels in general, and for gluon-gluon fusion and top-pair associated production in particular, NLO corrections reduce the theoretical uncertainties, and are needed in order to arrive at reliable predictions for total rates as well as for distributions.Comment: 11 pages, 7 figures, version accepted for publication on PL

Self-coupling of the Higgs boson in the processespp→ZHHH+Xandpp→WHHDicus1, Kao2, Repko3 2016Phys. Rev. D12080View full textAdd to dashboardCite

“…For example, the subprocess gg → HH obviously depends on the three Higgs coupling as does gg → ttHH [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. Processes with three Higgs bosons in the final state are necessary to determine κ 4 .…”

Scalar production and decay to top quarks including interference effects at NLO in QCD in an EFT approach

“…Our calculation does not directly apply to the cases in which the loop contribution is dominated by the top quark. However, we show that in such cases our calculation can be improved by adopting a reweighting technique, in which the Born pieces of the calculation are described by the full one-loop amplitudes [29,30]. In absence of a full calculation which is currently out of reach, this approach is expected to provide a reliable estimate for the QCD corrections even in the kinematic region where the EFT approximation is not valid.…”

“…In this work, we aim to follow a more solid approach to the NLO computation of the interference, based on the EFT framework, which in the unresolved case provides accurate results (i.e. without using soft-gluon approximation), and in the resolved case, can be further improved by using reweighting techniques (by Born-reweighting or FTapprox which includes the exact real corrections [29,30]) as we will discuss in the following. These results will then be passed to PS simulation, to obtain more realistic predictions.…”

“…The reweighting leads to the exact result at LO and a Born-improved result at NLO. We note here that with our setup we can also include the exact real emission amplitudes in a fashion similar to what has been done for double Higgs production in [29,30], but we refrain from doing so for simplicity. A discussion of the real emission amplitudes in the interference for this process can be found in [28].…”

Impact of top-Higgs couplings on Di-Higgs production at future colliders

“…Besides, a large deviation in the self-coupling may be a direct evidence for strong first-order electroweak phase transition in the early universe [58,59]. At the LHC, the di-Higgs production is the only way to measure the Higgs self-coupling and is dominated by the gluon-gluon fusion mechanism, which has JHEP01(2015)008 been widely studied in recent years (see examples in SM after 125 GeV Higgs boson [60][61][62][63][64]; see examples in MSSM and NMSSM after 125 GeV Higgs boson, [65][66][67][68][69]; see examples in 2HDM after 125 GeV Higgs boson, [70][71][72][73]; see examples in other models after 125 GeV Higgs boson, [74][75][76][77][78][79][80][81][82][83][84][85]). Among various decay channels, although the 4b final state has the largest fraction, the rare process hh → bbγγ is expected to have the most promising sensitivity due to the low QCD backgrounds at the LHC [86][87][88][89][90][91][92][93].…”