We show that the gluon fusion amplitude in the gauge-Higgs unification scenario is finite in any dimension regardless of its nonrenormalizability. This result is supported by the fact that the local operator describing the gluon fusion process is forbidden by the higher dimensional gauge invariance. We explicitly calculate the gluon fusion amplitude in an arbitrary dimensional gauge-Higgs unification model and indeed obtain the finite result.
We examine the possibility of observing the Kaluza-Klein gluons in gauge-Higgs unification models at the LHC with the energy sqrt{s}=14 TeV. We consider a benchmark model with the gauge symmetry SU(3)_C x SU(3)_W in five-dimensional space-time, where SU(3)_C is the gauge symmetry of the strong interaction and SU(3)_W is that for the electroweak interaction and a Higgs doublet field. It is natural in general to introduce SU(3)_C gauge symmetry in five-dimensional space-time as well as SU(3)_W gauge symmetry in gauge-Higgs unification models. Since the fifth dimension is compactified to S1/Z2 or…
We study the deviation of Higgs production through the gluon fusion process and the decay of Higgs boson to the bottom quark and the tau lepton in gauge-Higgs unification from the Standard Model prediction. We find that the signal strength of $gg \to H \to b\bar{b}, τ\barτ$ is necessarily suppressed comparing to the SM predictions due to the dominant suppression of the Higgs production via gluon fusion.
We present the master integrals relevant for computing the complete set of leading-colour analytic helicity amplitudes for top-quark pair production via gluon fusion at two-loops in QCD. We include corrections due to massive fermion loops which give rise to integrals involving elliptic curves. We also elaborate on the structure of singularities that play an important role in the numerical evaluation of the iterated integrals and their analytic continuation.
We present a complete set of analytic helicity amplitudes for top quark pair production via gluon fusion at two-loops in QCD. For the first time, we include corrections due to massive fermion loops which give rise to integrals over elliptic curves. We present the results of the missing master integrals needed to compute the amplitude and obtain an analytic form for the finite remainders in terms of iterated integrals using rationalised kinematics and finite field sampling. We also study the numerical evaluation of the iterated integrals.
We present a calculation of the helicity amplitudes for the process $gg\toγγ$ in three-loop massless QCD. We employ a recently proposed method to calculate scattering amplitudes in the 't Hooft-Veltman scheme that reduces the amount of spurious non-physical information needed at intermediate stages of the computation. Our analytic results for the three-loop helicity amplitudes are remarkably compact, and can be efficiently evaluated numerically. This calculation provides the last missing building block for the computation of NNLO QCD corrections to diphoton production in gluon fusion.
We calculate the two-loop corrections to heavy-quark pair production in the gluon fusion channel which arise from diagrams involving a closed light-quark loop. The calculation is carried out by keeping the exact dependence on the heavy-quark mass. The analytic results are written in terms of logarithms, classical polylogarithms Li_n (n=2,3,4), and genuine multiple polylogarithms Li_{2,2}. The functional arguments are rational expressions of two independent external invariants and they are chosen in such a way that the functions are real in all the physical phase-space points. Through systemati…
The amplitude of double Higgs boson production by the gluon fusion, $gg \to hh$, is known to be small due to cancellation between the graphs with the boson trilinear coupling and those with the coupling to the top quark. For this reason a study of this process was suggested as a sensitive probe of the Higgs sector nonlinearity. We calculate in a closed analytical form this amplitude at the threshold of the two bosons, where the cancellation is the strongest, and discuss the origin of the small value of the amplitude. We also note that the cancellation in the double boson production is in fact …
We propose a novel method in that quark-gluon tagging of the jets emitted as initial state radiation (ISR) can boost searches of invisible Higgs from gluon fusion processes against irreducible electroweak vector boson productions. While quark ISR typically takes up a dominant portion than gluon in the background processes mainly by frequent quark-gluon initiated hard scatterings at the LHC, gluon ISR portion in the gluon fusion can be significantly larger in the central region of detector. Focusing on invisible Higgs searches using jet substructure variables capturing the new features, we demo…
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
We studied the production of single chargino$\tildeχ_1^{\pm}$ accompanied by $μ^{\mp}$ lepton via gluon-gluon fusion at the LHC. The numerical analysis of their production rates is carried out in the mSUGRA scenario with some typical parameter sets. The results show that the cross sections of the $\tildeχ_1^{\pm}μ^{\mp}$ productions via gluon-gluon collision are in the order of $1 \sim 10^{2}$ femto barn quantitatively at the CERN LHC, and can be competitive with production mechanism via quark-antiquark annihilation process.
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 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.
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 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.
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.
We use chiral perturbation theory to show that pseudo-Goldstone boson scattering and gluon fusion probe different aspects of electroweak symmetry breaking at hadron colliders. In particular, the physics responsible for unitarizing the lowest-order pseudo-Goldstone boson scattering amplitudes need not significantly affect the gluon fusion process. We first show this within the context of strict chiral perturbation theory, and then discuss it using the language of resonances.
In the models with large extra-dimensions, we examine the production of a vector boson (γ/ Z) in association with the Kaluza-Klein (KK) modes of the graviton via gluon fusion. At the leading order, the process takes place through quark-loop box and triangle diagrams and it is ultraviolate finite. We report the results for the LHC. We also discuss the issues of anomaly and decoupling of heavy quarks in the amplitude.
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.
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…
Threshold resummation for gluon fusion $ZH$ production at the LHC
RWTH Aachen University（亚琛工业大学）；Indian Institute of Technology Kanpur（坎普尔印度理工学院）；Physical Research Laboratory（物理研究实验室）；Indian Institute of Technology Guwahati（古瓦哈提印度理工学院）；Durham University（杜伦大学）
We study the production of $η'$ from hadronizing thermal gluons using recently proposed $η'-g-g$ effective vertex. The $η'$ yield is found to be sensitive to the initial condition. At RHIC and LHC, the enhancement is large enough to be easily detected.
We have calculated one-loop amplitudes for the production of Higgs boson in association with two electroweak bosons ($H,γ,Z$) via gluon-gluon fusion. We present preliminary results for the total cross section at 8, 13 and 100 TeV center-of-mass energies at $pp$ colliders. We study the interference effect and, also comment on the effect of new physics in terms of anomalous couplings of the Higgs boson in these processes.
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 compute the contribution of third generation quarks ($t,\ b$) to the two-loop amplitude for on-shell $W$ boson pair production in gluon fusion $gg \to WW$. We present plots for the amplitude across partonic phase space as well as reference values for two kinematic points. The master integrals are efficiently evaluated by numerically solving a system of ordinary differential equations.
We compute the top quark contribution to the two-loop amplitude for on-shell $Z$ boson pair production in gluon fusion, $gg \to ZZ$. Exact dependence on the top quark mass is retained. For each phase space point the integral reduction is performed numerically and the master integrals are evaluated using the auxiliary mass flow method, allowing fast computation of the amplitude with very high precision.
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.
The amplitude for production of a single photon associated with quark pair in the fusion of two off-shell gluons is calculated. The matrix element found is applied to the inclusive prompt photon hadroproduction at high energies in the framework of kt-factorization QCD approach. The total and differential cross sections are calculated in both central and forward pseudo-rapidity regions. The conservative error analisys is performed. We used the unintegrated gluon distributions in a proton which were obtained from the full CCFM evolution equation as well as from the Kimber-Martin-Ryskin prescript…
Heavy charged lepton productions via gluon fusion at the LHC are revisited. Full loop calculations are adopted with an updated parton distribution function and electroweak data. Including contribution from new generation quarks in the loop, pair production of the sequential heavy lepton via gluon fusion at the LHC dominates over that via the Drell-Yan mechanism in some heavy lepton mass range. Exotic lepton single production of vector-like lepton extended models is also calculated. In the later case, the gluon fusion mechanism via the Higgs exchange is emphasized. Our numerical results for bot…
In this letter we present the three-loop virtual corrections to the Higgs boson production in the gluon fusion channel where finite top quark mass effects are taken into account. We perform an asymptotic expansion and manage to evaluate five terms in the expansion parameter $M_H^2/M_t^2$. A good convergence is observed almost until $M_H\approx 2M_t$.
We present recent developments concerning Higgs production in bottom quark annihilation and gluon fusion. For bottom quark annihilation, we show the transverse momentum distribution of the associated jets. Furthermore, we discuss the distribution of events into n-jet bins for n=0 and n>0 at NNLO and NLO, respectively. For gluon fusion, the quality of the heavy-top limit for differential quantities at O(α_s^4) is studied by taking into account higher order terms in the 1/m_{top} expansion.
We present a computation of the cross section for inclusive Higgs production in gluon-gluon fusion for finite values of the top mass in perturbative QCD to all orders in the limit of high partonic center-of-mass energy. We show that at NLO the high energy contribution accounts for most of the difference between the result found with finite top mass and that obtained in the limit of infinite top mass. We use our result to improve the known NNLO order result obtained with infinite top mass. We estimate the effect of the high energy NNLO top mass dependence on the K factor to be of the order of a…
The cross section for inclusive production of $f_2(1270)$ meson is calculated. We include both the mechanism of gluon-gluon fusion as well as the $ππ$ final-state rescattering. The contribution of the gluon-gluon fusion is calculated within the $k_t$-factorization approach with modern unintegrated gluon distribution functions (UGDFs). Some parameters for the $g^* g^* \to f_2$ vertex are extracted from the $γγ\to f_2(1270) \to ππ$ reactions. The results strongly depend on the parametrization of the $g^* g^* \to f_2(1270)$ form factor. Results of our model are compared to the ALICE preliminary d…
We analyze soft and collinear gluon resummation effects at the N$^3$LL level for Standard Model Higgs boson production via gluon fusion $gg\to H$ and the neutral scalar and pseudoscalar Higgs bosons of the minimal supersymmetric extension at the N$^3$LL and NNLL level, respectively. We introduce refinements in the treatment of quark mass effects and subleading collinear gluon effects within the resummation. Soft and collinear gluon resummation effects amount to up to about 5% beyond the fixed-order results for scalar and pseudoscalar Higgs boson production.
The possibility of distinguishing between two higgs production mechanisms, W fusion and gluon fusion, is investigated using the Monte Carlo event generator PYTHIA. It is shown that, considering the designed CM energy and luminosity for the LHC, it is not possible to distinguish between the two higgs production processes as, for a given integrated luminosity, they lead to the same number of events containing a rapidity gap.
We compute fully differential next-to-leading order QCD cross-sections for Higgs boson production via gluon fusion in the Standard Model. We maintain the full dependence of the cross-sections on the top and bottom quark mass. We find that finite quark mass effects are important given the achieved precision of QCD predictions for gluon fusion. Our Monte-Carlo program, HPro, can correct existing NNLO fully differential calculations, which employ the approximation of an infinitely heavy top and a vanishing bottom quark Yukawa coupling, for heavy quark finite mass effects through NLO.
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 discuss the recent derivation of the three-loop ${\cal O}(αα_s)$ contribution to the Higgs boson production cross section via gluon fusion arising from diagrams with light quarks, using an effective theory approach. We show results for the updated prediction of this process accounting for all the new theoretical calculations and the newest MSTW PDFs.
We derive the three loop soft function for inclusive Higgs production in gluon fusion, and use it to perform the resummation of the Higgs cross section at N$^3$LL$^\prime$ in SCET. We improve the accuracy of the resummation by including contributions of collinear origin. We include finite top, bottom and charm mass effect where available. These results are available through the public code ResHiggs.
The observational consequences of certain broken symmetries in a thermalised quark gluon plasma are elucidated. The signature under study is the spectrum of dileptons radiating from the plasma, through gluon fusion. Being a pure medium effect, this channel is non-vanishing only in plasmas with explicitly broken charge conjugation invariance. The emission rates are also sensitive to rotational invariance through the constraints imposed by Yang's theorem. This theorem is interpreted in the medium via the destructive interference between various multiple scattering diagrams obtained in the specta…
We discuss flavor mixing and resulting Flavor Changing Neutral Current (FCNC) in the SU(3) \otimes SU(3)_color gauge-Higgs unification. As the FCNC process we calculate the rate of D^0-\bar D^0 mixing due to the exchange of non-zero Kaluza-Klein gluons at the tree level. Flavor mixing is argued to be realized by the fact that the bulk mass term and brane localized mass term is not diagonalized simultaneously unless bulk masses are degenerate. It is shown that automatic suppression mechanism is operative for the FCNC processes of light quarks. We therefore obtain a lower bound on the compactifi…
Recently, ATLAS and CMS collaboration reported an excess in the diphoton events, which can be explained by a new resonance with mass around 750 GeV. In this work, we explored the possibility of identifying if the hypothetical new resonance is produced through gluon-gluon fusion or quark-antiquark annihilation, or tagging the beam. Three different observables for beam tagging, namely the rapidity and transverse momentum distribution of the diphoton, and one tagged bottom-jet cross section, are proposed. Combining the information gained from these observables, a clear distinction of the producti…
The gluon-gluon induced terms for Higgs production through weak boson fusion (WBF) are computed. Formally, these are of NNLO in the strong coupling constant. This is the lowest order at which non-zero color exchange occurs between the scattering quarks, leading to a color field and thus additional hadronic activity between the outgoing jets. Using a minimal set of cuts, the numerical impact of these terms is at the percent level with respect to the NLO rate for weak boson fusion. Applying the so-called WBF cuts leads to an even stronger suppression, so that we do not expect a significant deter…
We consider Higgs + 2 jet production via gluon fusion in the limit where either one of the Higgs-jet or the dijet invariant masses become much larger than the typical momentum transfers in the scattering. These limits also occur naturally in Higgs production via weak-boson fusion. We show that the scattering amplitudes factorize in the high energy limit, and we obtain the relevant effective vertices.
The resummed transverse momentum distribution of supersymmetric Higgs bosons produced through gluon fusion at NLO+NLL is presented, including the exact quark and squark mass dependences. Considering various MSSM scenarios, we compare our results to previous ones within the POWHEG approach. We analyze the impact of the bottom loop which becomes the dominant contribution to the gluon fusion cross section for a wide range of the parameter space for the pseudo-scalar and heavy Higgs.
The amplitude for scalar Higgs boson production in a fusion of two off-shell gluons is calculated including finite (not infinite) masses of quarks in the triangle loop. In comparison to the effective Lagrangian approach, we have found a new term in the amplitude. The matrix element found can be used in the kt-factorization approach to the Higgs boson production. The results are compared with the calculations for on-shell gluons. Small deviations from the cos(phi)^2-dependence are predicted. The off-shell effects found are practically negligible.
The production of pairs of charged Higgs bosons as predicted by the minimal supersymmetric standard model (MSSM) via the gluon fusion mechanism is investigated. The amplitudes at the leading one-loop order for the parton process gg -> H+ H- are calculated with the complete set of MSSM particles. Numerical results are presented for the cross section of the inclusive hadron process p p -> gg -> H+ H- + X at the LHC.
In this thesis, we have studied certain gluon fusion processes which proceed via quark loop diagrams at the leading order. The fact that these gluon-gluon channel processes are independent processes, their contributions towards the total/differential hadronic cross sections can be calculated separately. We have considered the production of a pair of electroweak vector bosons in association with a jet via gluon fusion within the standard model. These processes were not accessible at earlier hadron colliders such as the Tevatron. Therefore, observation of these rare processes at the LHC will be …
We consider the production of a generic system of non-strongly interacting particles with a high total invariant mass M in hadron collisions. We examine the transverse-momentum (q_T) distribution of the system in the small-q_T region (q_T << M), and we present a study of the perturbative QCD contributions that are enhanced by powers of large logarithmic terms of the type ln (M^2/q_T^2). These terms can be resummed to all orders in QCD perturbation theory. The partonic production mechanism of the final-state system can be controlled by quark-antiquark (qqbar) annihilation and/or by gluon fusion…
Di-gluon fusion mechanism might account for the large branching ratios of $B\to K η^{\prime}$. But because we know little about the effective $η^{\prime}gg$ vertex, there are large uncertainties in perturbative QCD estimations. In this paper, we try several kinds of $η^{\prime}gg$ form factors and compare the numerical results with the experiment. We find that, though we know little about $η^{\prime}gg$ form factor, if di-gluon fusion mechanism is important in $B\to K η^{\prime}$, the branching ratios of the decays $B\to K^{\ast} η^{\prime}$ would be around $10^{-5}$ which can be tested by fut…
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.
We present a detailed phenomenological analysis of the production of a Standard Model Higgs boson in association with up to three jets. The Higgs is produced via gluon fusion, which is an irreducible background to the vector boson fusion mechanism. We calculate the next-to-leading order corrections in QCD in the limit of an infinitely heavy top quark. Numerical results are presented for a large variety of observables, for different selection cuts, and for different choices of the jet tagging scheme.
We compute the leading corrections to the differential cross section for top-pair production via gluon fusion due to dimension-six operators at leading order in QCD. The Standard Model fields are assumed to couple only weakly to the hypothetical new sector. A systematic approach then suggests treating single insertions of the operator class containing gluon field strength tensors on the same footing as expli\-citly loop suppressed contributions from four-fermion operators. This is in particular the case for the chromomagnetic operator $Q_{(uG)}$ and the purely bosonic operators $Q_{(G)}$ and $…
We present a calculation that allows for an estimation of the NNLO contributions to the Higgs production in the weak boson fusion channel. A possible deterioration of this important channel for the Higgs discoveries at the LHC can be ruled out by this calculation due to the small remaining cross section after the weak boson cuts.
In high energy hadronic collisions, a general CP-violating Higgs boson $Φ$ with accompanying jets can be efficiently produced via gluon fusion, which is mediated by heavy quark loops. In this letter we study the dominant sub-channel $ gg \to Φggg$ of the gluon fusion production process with triple real emission corrections at order $α_s^5$. We go beyond the heavy top limit approximation and include the full mass dependence of the top- and bottom-quark contributions. Furthermore, we show within a toy-model scenario that bottom-quark loop contributions in combination with large values of $\tan β…
We compute the leading logarithmic behaviour of the cross-section for the production of a pseudoscalar Higgs boson in gluon-gluon fusion to all-orders in perturbation theory, in the limit of large partonic centre of mass energy. We also calculate the Higgs rapidity distribution to the same accuracy. We include the contributions of top and bottom quarks, together with their interference. Our results are given in terms of single and double integrals, evaluated explicitly up to next-to next-to leading order (NNLO). We use our results to improve the known NNLO inclusive cross-section computed in t…
We present the two-loop matrix elements for the scattering of two gluons into two photons in QCD. These matrix elements will enter into improved estimates of the QCD background to Higgs production at the LHC when the Higgs decays into two photons. The photon mode is especially important if M_H < 140 GeV. We also give the amplitudes for the crossed process, glue gamma to glue gamma.
We present fully differential next-to-leading order results for Higgs production in association with a $Z$ boson in gluon fusion. Our two-loop virtual contributions are evaluated numerically using sector decomposition, including full top-quark mass effects, and supplemented at high $p_T$ by an analytic high-energy expansion to order ($m_Z^4, m_H^4, m_t^{32}$). Using the expanded results we also present a study of the top-quark mass scheme uncertainty at large $p_T$.
