We consider one-loop amplitudes of a Higgs boson coupled to gluons in the limit of a large top quark mass. We treat the Higgs as the real part of a complex field phi that couples to the self-dual field strengths and compute the one-loop corrections to the phi-NMHV amplitude, which contains one gluon of positive helicity whilst the remaining three have negative helicity. We use four-dimensional unitarity to construct the cut-containing contributions and a hybrid of Feynman diagram and recursive based techniques to determine the rational piece. Knowledge of the phi-NMHV contribution completes the analytic calculation of the Higgs plus four gluon amplitude. For completeness we also include expressions for the remaining helicity configurations which have been calculated elsewhere. These amplitudes are relevant for Higgs plus jet production via gluon fusion in the limit where the top quark is large compared to all other scales in the problem.
We compute the next-to-leading order (NLO) QCD corrections to the gluon-fusion subprocess of diphoton-plus-jet production at the LHC. We compute fully differential distributions by combining two-loop virtual corrections with one-loop real radiation using antenna subtraction to cancel infrared divergences. We observe significant corrections at NLO which demonstrate the importance of combining these corrections with the quark-induced diphoton-plus-jet channel at next-to-next-to-leading order (NNLO).
We present the full color two-loop six-point all-plus Yang-Mills amplitude in compact analytic form. The computation uses four dimensional unitarity and augmented recursion.
We investigate the effects of an all order QCD resummation of soft gluon emissions for Higgs boson production in association with two hard jets. We consider both the gluon-gluon fusion and weak boson fusion processes and show how to resum a large part of the leading logarithms in the jet veto scale. Our resummation improves on previous analyses which also aim to include the effects of multiple soft gluon radiation. In addition we calculate the interference between weak boson fusion and gluon-gluon fusion and find that it is small.
We present analytic results for one-loop Higgs boson + $n$-gluon amplitudes for $n\le 5$ in the full theory including all dependence on the (top) quark mass. In this paper we consider only the case where the gluons all have the same helicity. The amplitudes are expressed in simple formula and display similar structure. Their limiting behaviour in small Higgs momentum and large top mass is studied.
Pair production processes of neutral Higgs particles will allow us to study the trilinear Higgs couplings at future high--energy colliders. Several mechanisms give rise to multi--Higgs final states in hadron interactions. In the present paper we investigate Higgs pair production in gluon--gluon collisions. After recapitulating pair production in the Standard Model, the analysis of the cross sections is carried out in detail for the neutral Higgs particles in the minimal supersymmetric extension.
The search for charged Higgs bosons, which are predicted in supersymmetric theories, is difficult at hadron colliders if the mass is large. In this paper we present the theoretical set-up for the production of charged Higgs boson pairs at the LHC in gluon-gluon collisions: $pp -> gg -> H^+ H^-$. When established experimentally, the trilinear couplings between charged and neutral CP-even Higgs bosons, $H^+ H^- h^0$ and $H^+ H^- H^0$, can be measured.
Antenna functions describe the infrared singular behaviour of colour-ordered QCD matrix elements due to the emission of unresolved partons inside an antenna formed by two hard partons. In this paper, we show that antenna functions for hard gluon-gluon pairs can be systematically derived from the effective Lagrangian describing Higgs boson decay into gluons, and compute the the infrared structure of the colour-ordered Higgs boson decay matrix elements at NLO and NNLO.
Real emission corrections to Higgs production via gluon fusion, at order alpha_s^4, lead to a Higgs plus two-jet final state. We present the calculation of these scattering amplitudes, as induced by top-quark triangle-, box- and pentagon-loop diagrams. These diagrams are evaluated analytically for arbitrary top mass m_t. We study the renormalization and factorization scale-dependence of the resulting H + 2 jet cross section, and discuss phenomenologically important distributions at the LHC. The gluon fusion results are compared to expectations for weak-boson fusion cross sections.
We study the effects of a set of dimension six flavor changing effective operators on several processes of production of top quarks at the LHC. Namely, top anti-top production and associated production of a top and a gauge or Higgs boson. Analytical expressions for the cross sections of these processes are derived and presented.
We study the effect of explicit CP violation in the Higgs sectors of the MSSM in the di-photon decay of the lightest CP-mixed Higgs state. Further it is shown that the gluon fusion production mechanism along with the di-photon decay enhances CP-violating effects for a large set of suitably chosen parameter values.
We calculate next-to-leading order (NLO) QCD corrections to electroweak Higgs plus three jet production. Both vector boson fusion (VBF) and Higgs-strahlung type contributions are included along with all interferences. The calculation is implemented within the Matchbox NLO framework of the Herwig++ event generator.
We studied the pair production rate of charged Higgs bosons via gluon-gluon collisions in the general two-Higgs-doublet model. The analysis of its production are made with possible parameter values of Higgs sectors in this model. We find that the production cross sections may be 4 to 41 fermi-bar in the future LHC pp collider with these parameters. The calculation also shows that this pair production process is not sensitive to the neutral Higgs masses, therefore its measurment could not give more imformations about the neutral Higgs bosons.
Standard-Model Higgs bosons are dominantly produced via the gluon-fusion mechanism $gg \to H$ at the LHC, i.e. in a loop-mediated process with top loops providing the dominant contribution. For the measured Higgs boson mass of $\sim 125$ GeV the limit of heavy top quarks provides a reliable approximation as long as the relative QCD corrections are scaled with the full mass-dependent LO cross section. In this limit the Higgs coupling to gluons can be described by an effective Lagrangian. The same approach can also be applied to the coupling of more than one Higgs boson to gluons. We will derive…
Transport processes are considered for their abilities to generate flow in a mixed-phase system of hadrons plus quark-gluon plasma exhibiting temperature and density gradients. Diffusive mechanisms are found to be the leading sources. Even after overcoming viscous effects, conductive and diffusive forces generate flow velocities for pions in a model using kinetic theory to within fifteen percent of light speed. Since such flow is not observed, this could possibly rule out the mixed phase in the evolution of high energy heavy ion collisions.
One and two-jet observables of dimension-7 Higgs-gluon coupling operators are studied as probes of possible deviations from the top-loop induced gluon-Higgs coupling. We discuss the case of both a scalar as well as a pseudo-scalar Higgs boson and show that higher order operators can give visible deviations from Standard Model distribution shapes.
The gluon-gluon-higgs amplitude is investigated in the context of 5D models of gauge-higgs unification. A simple algorithm allows to include, in a fully analytical way, the contribution of the whole Kaluza-Klein tower of a 5D quark to the amplitude. This algorithm is applied to realistic models based on SO(5) symmetry. Within the studied classes of models, the higgs production cross section is always suppressed.
We demonstrate that CP violation in the Higgs sector, \eg\ of a multi-doublet model, can be directly probed using gluon-gluon collisions at the SSC. % requires phyzzx.tex macro package
In this paper, the soft gluon resummation effect in the Higgs boson plus two-jet production at the LHC is studied. By applying the transverse momentum dependent factorization formalism, the large logarithms introduced by the small total transverse momentum of the Higgs boson plus two-jet final state system, are resummed to all orders in the expansion of the strong interaction coupling at the accuracy of Next-to-Leading Logarithm. We also compare our result with the prediction of the Monte Carlo event generator Pythia8, and found noticeable difference in the distributions of the total transvers…
Higgs production in association with three jets via gluon fusion (GF) is an important channel for the measurement of the CP-properties of the Higgs particle at the LHC. In this letter, we go beyond the heavy top effective theory approximation and include at LO the full mass dependence of the top- and bottom-quark contributions. We consider the dominant sub-channel gg -> H ggg which involves the manipulation of massive rank-5 hexagon integrals. Furthermore, we present results for several differential distributions and show deviations from the effective theory as large as 100% at high pT for lig…
The decay of the standard model Higgs boson into a single photon and a vector unparticle through a one-loop process is studied. For an intermediate mass Higgs boson, this single photon plus unparticle mode can have a branching ratio comparable with the two-photon discovery mode. The emitted photon has a continuous energy spectrum encoding the nature of the recoil unparticle. It can be measured in precision studies of the Higgs boson after its discovery.
In composite Higgs models light fermionic top partners often play an important role in obtaining a 126 GeV Higgs mass. The presence of these top partners implies that coloured vector mesons, or massive gluon partners, most likely exist. Since the coupling between the top partners and gluon partners can be large there are then sizeable two-loop contributions to the composite Higgs mass. We compute the radiative correction to the Higgs mass from a gluon partner in the minimal composite Higgs model and show that the Higgs mass is in fact reduced. This allows the top partner masses to be increased…
We consider the Higgs boson production at high energy hadron colliders in the framework of the $k_T$-factorization approach. The attention is focused on the dominant gluon-gluon fusion subprocess. We show that $k_T$-factorization gives a possibility to investigate the associated Higgs boson and jets production.
Analysis of the 125 GeV Higgs boson decay rates to two photons and Z plus photon in the Inert Doublet Model is presented. We study the constraints on the masses of the scalars (in particular the Dark Matter candidate) and their couplings to the Higgs boson, coming from the h -> γγdata and confront them with the WMAP measurements of the Dark Matter relic density.
We consider gluon-fusion and weak-boson fusion production of Higgs plus two jets in pp collisions at sqrt{s}=14 TeV (LHC) and sqrt{s}=50, 100, 200 TeV (VLHC). We give cross sections for Higgs masses between 115 GeV and 200 GeV, and discuss the experimental cuts that should be applied in order to enhance the weak-boson fusion contribution with respect to the gluon-fusion background.
We study how gluons carrying linear polarization inside an unpolarized hadron contribute to the transverse momentum distribution of Higgs bosons produced in hadronic collisions. They modify the distribution produced by unpolarized gluons in a characteristic way that could be used to determine whether the Higgs boson is a scalar or a pseudoscalar particle.
A simple generalization of the low-energy theorem for the effective Higgs-gluon-gluon coupling for the case of simultaneous decoupling of several heavy quarks
Institute for Nuclear Research of the Russian Academy of Sciences（俄罗斯科学院核物理研究所）
In this talk we consider amplitudes for processes involving a Higgs boson, either scalar or pseudoscalar, plus four light partons. These amplitudes are relevant to the production of a Higgs boson plus two jets in hadronic collisions. They are also relevant to calculating the transverse momentum spectrum for Higgs bosons at next-to-leading order in the strong coupling. We work in the limit that the top quark is much heavier than the Higgs bosons and use effective Lagrangians for the interactions of gluons with the Higgs bosons. We present the amplitudes involving a Higgs boson and: 1) four gluo…
The gluon-gluon induced terms for Higgs production through weak-boson fusion are calculated. They form a finite and gauge-invariant subset of the NNLO corrections in the strong coupling constant. This is also the lowest order with sizeable t-channel colour exchange contributions, leading to additional hadronic activity between the outgoing jets.
We calculate the contributions to the two-loop scattering amplitudes $h \to gg$, $h \to ggg$ and $h \to q \bar q g$ that arise from a modified trilinear Higgs coupling $λ$. Analytic expressions are obtained by performing an asymptotic expansion near the limit of infinitely heavy top quark. The calculated amplitudes are necessary to study the impact of the ${\cal O} (λ)$ corrections to the transverse momentum distributions ($p_{T,h}$) in single-Higgs production at hadron colliders for low and moderate values of $p_{T,h}$.
We study effects from new colored states and the Higgs portal on gluon fusion production. We isolate possible loop contributions from new colored scalars, fermions, and vectors, incorporating effects from Higgs portal-induced scalar mixing, leading to dramatic effects on gluon fusion and branching fractions. Higgs identification must generally allow for these effects, and using our results, possible tensions from fits to the Standard Model expectation can be relieved by inclusion of New Physics effects.
We investigate the QCD resummation for the Higgs boson plus a high $P_T$ jet production with large rapidity separations in proton-proton collisions at the LHC. The relevant Balitsky-Fadin-Kuraev-Lipatov (BFKL) and Sudakov logs are identified and resummed. In particular, we apply recent developments of the transverse momentum dependent factorization formalism in the impact factors, which provides a systematic framework to incorporate both the BFKL and Sudakov resummations.
The mixing of the Standard Model Higgs boson with a ttbar scalar bound state (arising from a new stronger-than-QCD interaction) can enhance the Higgs boson's coupling to two gluons. It is possible that the two-gluon decay mode of a light Higgs boson may even dominate. This alters the Higgs boson search strategy at Tevatron Run 2 in a significant way. We present a simple model in which such a scenario may be realized. The modifications to the Higgs search signal, as well as further experimental tests of this scenario are also discussed.
The detailed study of the Higgs boson is one of the main tasks of contemporary particle physics. Gluon fusion, the main production channel of Higgs bosons at the LHC, has been successfully modelled in QCD up to $\text{N}^3\text{LO}$. To fully exploit this unprecedented theoretical effort, sub-leading contributions, such as electroweak corrections, must be investigated. I will present the analytic calculations of the gluon- and quark-induced Higgs plus jet amplitudes in mixed QCD-electroweak corrections mediated by light quarks up to order $v α^2 α_S^{3/2}$.
We discuss how the UN2LOPS scheme for matching NNLO calculations to parton showers can be applied to processes with large higher-order perturbative QCD corrections. We focus on Higgs-boson production through gluon fusion as an example. We also present an NNLO fixed-order event generator for this reaction.
We combine soft and collinear matrix elements to define transverse momentum dependent parton distributions (TMDs) for gluons, free from rapidity divergences. We establish a factorization theorem at next-to-leading order for the Higgs boson transverse momentum ($q_T$) spectrum, and use it to derive evolution equations for gluon TMDs. The evolution for all gluon TMDs is driven by a universal kernel, i.e. the same for all polarizations. In the region of intermediate $q_T$ we match the unpolarized, helicity and linearly polarized gluon distributions onto PDFs. We calculate the resummed Higgs trans…
In this talk we discuss the implementation of the full next-to-leading order QCD corrections to electroweak Higgs boson plus three jet production at the LHC within the Matchbox framework of the Herwig++ event generator. We also present numerical results for integrated cross sections and kinematic distributions.
During recent years perturbative fixed order and resummation calculations have decreased uncertainties on predictions for gluon fusion Higgs production cross sections tremendously. Most exciting results have been published just this year. In these proceedings I present an overview of recent and most recent developments of these calculations that allow theory predictions to compete with the experimental precision reached by future collider upgrades.
The observation of double and triple scalar boson production at hadron colliders could provide key information on the Higgs self couplings and the potential. As for single Higgs production the largest rates for multiple Higgs production come from gluon-gluon fusion processes mediated by a top-quark loop. However, at variance with single Higgs production, top-quark mass and width effects from the loops cannot be neglected. Computations including the exact top-quark mass dependence are only available at the leading order, and currently predictions at higher orders are obtained by means of approx…
We investigate the possible role of linearly polarized gluons in Higgs production from unpolarized pp collisions. The transverse momentum distribution of the produced Higgs boson is found to exhibit a modulation with respect to the naive, unpolarized expectation, with the sign depending on the parity of the Higgs boson. The transverse momentum distribution of a scalar Higgs will, therefore, have a shape clearly different from a pseudoscalar Higgs. We suggest that this effect can be used to determine the parity of the Higgs at the LHC, without the need to use challenging angular distributions.
We present results of QCD corrections to Higgs boson production at the CERN Large Hadron Collider. Potentially large logarithmic contributions from multiple soft-gluon emission are summed up to all order in the strong coupling. Various kinematical distributions, including the Higgs transverse momentum, are predicted with O(alpha_s^3) precision. Comparison is made to outputs of the popular Monte Carlo event generator PYTHIA.
Inclusive cross sections for Higgs boson production in proton-proton collisions are calculated in the formalism of unintegrated gluon distributions (UGDF). Different UGDF from the literature are used. Although they were constructed in order to describe the HERA deep-inelastic scattering $F_2$ data, they lead to surprisingly different results for Higgs production. We present both two-dimensional invariant cross section as a function of Higgs rapidity and transverse momentum, as well as corresponding projections on rapidity or transverse momentum. We quantify the differences between different UG…
In this paper, we investigate the decay of Higgs boson to $h_c$ plus a photon in the NRQCD theoretical framework. Comparing with the Higgs decay to $J/ψ$ plus a photon channel, this process has not indirect contribution, can be used to detect the Yukawa coupling of Higgs and charm quarks. The results show that the decay branch ratio of this process is about $10^{-8}$. If we takes into account the $10^{-3}$ efficiency in the $h_c$ detection, no events will be available even in the case of $30ab^{-1}$ luminosity at FCC-pp with 100 TeV center of mass energy. However, if the detection efficiency o…
We study the influence of two--loop radiative corrections of enhanced electroweak strength on Higgs production at the LHC. We consider Higgs production by the gluon fusion mechanism, with the subsequent decay of the Higgs boson into a pair of Z bosons, and incorporate the resonance shape corrections up to order $(g^2 \, m_H^2 / m_W^2)^2$. We take into account the full $g g \rightarrow Z Z$ process and the $q \bar{q} \rightarrow Z Z$ background, as well as the subsequent decay of the Z pair into leptons. We also discuss the theoretical uncertainty related to the use of the equivalence theorem i…
Higgs boson production in association with two tagging jets will be mediated by electroweak vector boson fusion and by gluon fusion processes at the CERN LHC. The characteristic distributions for the gluon fusion process are analyzed for the $H\to W^+W^-$ signal at $m_H=160$ GeV, with subsequent leptonic decay of the $W$-pair. The dominant backgrounds from top-quark pair production, $WWjj$ production and vector boson fusion processes can be suppressed to a level of $S/B\approx 1/4$, yielding a highly significant gluon fusion signal with 30 fb$^{-1}$. Analysis of the azimuthal angle correlation…
We report on the calculation of the cross section for Higgs boson production in association with three jets via gluon fusion, at next-to-leading-order (NLO) accuracy in QCD, in the infinite top-mass approximation. After including the complete NLO QCD corrections, we observe a strong reduction in the scale dependence of the result, and an increased steepness in the transverse momentum distributions of both the Higgs and the leading jets. The results are obtained with the combined use of GoSam, Sherpa, and the MadDipole/MadEvent framework.
We investigate the gluon distribution functions and their contributions to the Higgs boson production in pp collisions in the transverse momentum dependent factorization formalism. In addition to the usual azimuthal symmetric transverse momentum dependent gluon distribution, we find that the azimuthal correlated gluon distribution also contributes to the Higgs boson production. This explains recent findings on the additional contribution in the transverse momentum resummation for the Higgs boson production as compared to that for electroweak boson production processes. We further examine the s…
In the spirit of the Composite Standard Model (CSM) we look at the effect of $H$, $Z_L$ compositeness on $ZH$ production in gluon-gluon and photon-photon collisions. Because they would perturb the basic cancellations occuring in SM amplitudes, such compositeness effects would lead to spectacular modifications of the energy dependence of the amplitudes and cross sections. We illustrate this fact by introducing $H$, $Z_L$ test form factors and computing the corresponding differential cross section and the fraction of longitudinal $Z_L$ production.
We show that the production of a Higgs boson in association with a jet in proton-proton collisions is sensitive to the linear polarization of gluons inside unpolarized protons. We present the analytical expressions, at leading order in perturbative QCD, for various transverse momentum dependent observables, which can be measured at the LHC. Since there are no experimental constraints on the linearly polarized gluon distribution, its effects are studied by adopting two different models. In particular, we find that the $\cos2ϕ$ azimuthal asymmetry is a very promising observable because it could …
We consider QCD corrections to Higgs boson production through gluon--gluon fusion in hadron collisions. We compute the cross section, performing the all-order resummation of multiple soft-gluon emission at next-to-next-to-leading logarithmic level. Known fixed-order results (up to next-to-next-to-leading order) are consistently included in our calculation. We give phenomenological predictions for Higgs boson production at the Tevatron and at the LHC. We estimate the residual theoretical uncertainty from perturbative QCD contributions. We also quantify the differences obtained by using the pres…
The implementation of the full next-to-leading order (NLO) QCD corrections to electroweak Higgs boson plus three jet production at hadron colliders such as the LHC within the Matchbox NLO framework of the Herwig++ event generator is discussed. We present numerical results for integrated cross sections and kinematic distributions.
We have computed the two-loop, electroweak corrections to the production of a light and a heavy neutral, scalar Higgs-boson through the important gluon fusion process in the Two-Higgs-Doublet Model. We provide our results in various renormalization schemes for different scenarios and benchmark points, which will be valuable for experimental studies at the LHC. We describe the technicalities of our two-loop calculation and augment it by a phenomenological discussion. Our results are also applicable to the gluonic neutral, scalar Higgs-boson decays.
The production of charged Higgs boson pairs from gluon-gluon fusion is studied in the minimal supersymmetric model(MSSM) at proton-proton colliders. We find that the contribution of the scalar quark loops to the subprocess production rate is substantial and consequently the production rate in proton-proton colliders is enhanced in the MSSM if there exist scalar quarks with favorable masses. The results show that this cross section may reach a few femptobarn in the future LHC collider with plausible values of the parameters.
The measurement of hadronic Higgs Boson branching ratios H -> bb, H -> gg for a light Standard Model-like Higgs boson produced at 250 GeV centre of mass energy at the International Linear Collider (ILC) is presented. The tools and techniques used for the analysis are briefly discussed.
We consider an extension of the Standard Model with an arbitrary number of heavy quarks having general couplings to the Higgs boson. We construct an effective Lagrangian integrating out quarks that are heavier than half the mass of the Higgs boson and compute the Wilson coefficient for the effective gluon-Higgs vertex through NNLO. We apply our result to a composite Higgs model with vector-like quarks coupling to the third generation quarks. In the heavy quark-mass approximation, we show that the suppression of the leading-order cross section with respect to the Standard Model does not depend …
The CP-violating effects to the subprocess $gg\to H^+H^-$ is studied in the mSUGRA scenario at the CERN LHC, by taking into account the experimental bounds of electron and neutron EDM's. The CP violation effects in this process are related to the complex phases of $μ$ and $A_{f}$ in the mSUGRA scenario. In our calculation we consider small CP phases of $μ$ and $A_{f}$ and neglect the effects of neutral Higgs bosons mixing. In this case the CP effects to the process mainly come from the complex couplings of Higgs-squark-squark. We find a strong dependence of charged Higgs boson pair production …
We study the production of Higgs boson pairs via gluon fusion at the LHC in the Two-Higgs-Doublet Model. We present predictions at NLO accuracy in QCD, matched to parton showers through the MC@NLO method. A dedicated reweighting technique is used to improve the NLO calculation upon the infinite top-mass limit. We perform our calculation within the MadGraph5_aMC@NLO framework, along with the 2HDM implementation based on the NLOCT package. The inclusion of the NLO corrections leads to large K-factors and significantly reduced theoretical uncertainties. We examine the seven 2HDM Higgs pair combin…
Higgs bosons can be produced copiously at the LHC via gluon fusion induced by top and bottom quark loops, and can be enhanced strongly if extra heavy quarks exist. We present results for Higgs +zero-, one- and two-jet production at the LHC, in both the Standard Model and the 4th generation model, by evaluating the corresponding heavy quark triangle, box and pentagon Feynman diagrams. We compare the results by using the effective Higgs-gluon interactions in the limit of heavy quarks with the cross sections including the full mass dependences. NLO effects with full mass dependence are included i…
