Higgs Production Research Articles

A Study of QCD Radiation in VBF Higgs Production with Vincia and Pythia

We discuss and illustrate the properties of several parton-shower algorithms available in Pythia and Vincia, in the context of Higgs production via vector boson fusion (VBF). In particular, the distinctive colour topology of VBF processes allows to define observables sensitive to the coherent radiation pattern of additional jets. We study a set of such observables, using the Vincia sector-antenna shower as our main reference, and contrast it to Pythia's transverse-momentum-ordered DGLAP shower as well as Pythia's dipole-improved shower. We then investigate the robustness of these predictions as successive levels of higher-order perturbative matrix elements are incorporated, including next-to-leading-order matched and tree-level merged calculations, using Powheg Box and Sherpa respectively to generate the hard events.

Fiducial cross sections for the lepton-pair-plus-photon decay mode in Higgs production up to NNLO QCD

The rare three-body decay of a Higgs boson to a lepton-antilepton pair and a photon is starting to become experimentally accessible at the LHC. We investigate how higher-order QCD corrections to the dominant gluon-fusion production process impact on the fiducial cross sections in this specific Higgs decay mode for electrons and muons. Corrections up to NNLO QCD are found to be sizeable. They are generally uniform in kinematical variables related to the Higgs boson, but display several distinctive features in the kinematics of its individual decay products.

Higgs production in association with a dark-Z at future electron positron colliders

In recent years there have been many proposals for new electron–positron colliders, such as the circular electron–positron collider, the international linear collider, and the future circular collider in electron–positron mode. Much of the motivation for these colliders is precision measurements of the Higgs boson and searches for new electroweak states. Hence, many of these studies are focused on energies above the hZ threshold. However, there are proposals to run these colliders at the lower W W threshold and Z-pole energies. In this paper, we study a new search for Higgs physics accessible at lower energies: e + e − → hZ d, where Z d is a new light gauge boson such as a dark photon or dark-Z. Such searches can be conducted at the W W threshold, i.e. energies below the hZ threshold where exotic Higgs decays can be searched for in earnest. Additionally, due to very good angular and energy resolution at future electron–positron colliders, these searches will be sensitive to Z d masses below 1 GeV, which is lower than the current direct LHC searches. We will show that at GeV with 10 ab−1, a search for e + e − → hZ d is sensitive to h − Z − Z d couplings of δ ∼ 9 × 10−3 and cross sections of ab for Z d masses below 1 GeV. The results are similar at GeV with 5 ab−1. These limits are better than those expected from limits on the HL-LHC limits on Higgs branching ratio into generic non-standard model final states and comparable to meson decay limits.

Sensitivity to BSM effects in the Higgs pT spectrum within SMEFT

The study of Higgs boson production at large transverse momentum is one of the new frontiers for the LHC Higgs physics programme. This paper considers boosted Higgs production in the Standard Model Effective Field Theory (SMEFT). We focus on the gluon fusion and t overline{t} H production processes and study the effects of three dimension-6 operators: the top Yukawa operator, the gluon-Higgs effective coupling and the chromomagnetic dipole operator of the top quark. We perform a detailed study of the sensitivity of current and future LHC data to the corresponding Wilson coefficients, consistently accounting for their renormalisation group evolution. We compare the sensitivities obtained with only linear and linear + quadratic terms in the SMEFT by using the spectrum shape and the addition of the Higgs signal yields. We also consider fits of pT spectra in models with heavy-top partners and in MSSM scenarios with a light scalar top and study the validity of the SMEFT assumptions as a function of the new-particle masses and the Higgs pT range. Finally, we extract constraints on the Wilson coefficients for gluon fusion from a simultaneous fit to the ATLAS and CMS data and compare our results with those obtained in global SMEFT analyses.

A comparative study of Higgs boson production from vector-boson fusion

The data taken in Run II at the Large Hadron Collider have started to probe Higgs boson production at high transverse momentum. Future data will provide a large sample of events with boosted Higgs boson topologies, allowing for a detailed understanding of electroweak Higgs boson plus two-jet production, and in particular the vector-boson fusion mode (VBF). We perform a detailed comparison of precision calculations for Higgs boson production in this channel, with particular emphasis on large Higgs boson transverse momenta, and on the jet radius dependence of the cross section. We study fixed-order predictions at next-to-leading order and next-to-next-to-leading order QCD, and compare the results to NLO plus parton shower (NLOPS) matched calculations. The impact of the NNLO corrections on the central predictions is mild, with inclusive scale uncertainties of the order of a few percent, which can increase with the imposition of kinematic cuts. We find good agreement between the fixed-order and matched calculations in non-Sudakov regions, and the various NLOPS predictions also agree well in the Sudakov regime. We analyze backgrounds to VBF Higgs boson production stemming from associated production, and from gluon-gluon fusion. At high Higgs boson transverse momenta, the ∆yjj and/or mjj cuts typically used to enhance the VBF signal over background lead to a reduced efficiency. We examine this effect as a function of the jet radius and using different definitions of the tagging jets. QCD radiative corrections increase for all Higgs production modes with increasing Higgs boson pT, but the proportionately larger increase in the gluon fusion channel results in a decrease of the gluon-gluon fusion background to electroweak Higgs plus two jet production upon requiring exclusive two-jet topologies. We study this effect in detail and contrast in particular a central jet veto with a global jet multiplicity requirement.

Exact Top-Quark Mass Dependence in Hadronic Higgs Production.

The impact of the finite top-quark mass on the inclusive Higgs production cross section at higher perturbative orders has been an open question for almost three decades. In this Letter, we report on the computation of this effect at next-to-next-to-leading order QCD. For the purely gluonic channel, it amounts to +0.62% relative to the result obtained in the Higgs effective field theory approximation. The formally subleading partonic channels overcompensate this shift, leading to an overall effect of -0.26% at a pp collider energy of 13TeV, and -0.1% at 8TeV. This result eliminates one of the main theoretical uncertainties to inclusive Higgs production cross section at the LHC.

Thermal and hard scales in transverse momentum distributions, fluctuations, and entanglement

We analyze the transverse momentum distributions of pp, pPb, XeXe and PbPb collisions at different RHIC and LHC energies and centralities as well as the corresponding distributions for Higgs production decaying into $\gamma\gamma$ and 4l. A simple linear relation is found between the effective thermal temperature and the hard scale, approximately valid for all processes and mainly determined by the hard scale fluctuations. In order to go further, it is shown that the whole spectrum of pp collisions can be described by a single function showing that the thermal temperature is determined solely by the hard scale and its fluctuations. The possible relation between the multiplicities of the soft and hard scales is explored.

Polynomial inflation and dark matter

We present a minimal UV complete framework to embed inflation and dark matter by extending the standard model with a singlet real scalar field (the inflaton) and a singlet fermionic field acting as dark matter. The inflaton features the most general renormalizable polynomial up to quartic order, which is flat due to the existence of a perturbed inflection-point, comfortably fitting CMB measurements. We also analyze (p)reheating by considering the Higgs production via inflaton decay. In the early universe, dark matter can be generated by the mediation of gravitons or inflatons. However, the production via the direct decay of the inflatons dominates, making viable a large range of dark matter masses, from {mathcal {O}}(10^{-5}) GeV to {mathcal {O}}(10^{11}) GeV.

Physics potential for the Hrightarrow hbox {ZZ}^{*} decay at the CEPC

The precision of the yield measurement of the Higgs boson decaying into a pair of Z bosons process at the Circular Electron Positron Collider is evaluated. Including the recoil Z boson associated with the Higgs production (Higgsstrahlung) a total of three Z bosons are involved for this channel, from which final states characterized by the presence of a pair of leptons, quarks, and neutrinos are chosen for the signal. Two analysis approaches are compared and the final statistical precision of {sigma }_{mathrm {ZH}}{cdot }BR(H rightarrow ZZ^{*}) is estimated to be 6.9% using a multivariate analysis technique, based on boosted decision trees. The relative precision of the Higgs boson width, using this H rightarrow ZZ^{*} decay topology, is estimated by combining the obtained result with the precision of the inclusive ZH cross section measurement.

Measuring Higgs boson self-couplings with 2 \u2192 3 VBS processes

We study the measurement of Higgs boson self-couplings through 2 → 3 vector boson scattering (VBS) processes in the framework of Standard Model effective field theory (SMEFT) at both proton and lepton colliders. The SMEFT contribution to the amplitude of the 2 → 3 VBS processes, taking WLWL → WLWLh and WLWL → hhh as examples, exhibits enhancement with the energy frac{{mathcal{A}}^{mathrm{BSM}}}{{mathcal{A}}^{mathrm{SM}}}sim frac{E^2}{Lambda^2} , which indicates the sensitivity of these processes to the related dimension-six operators in SMEFT. Simulation of the full processes at both hadron and lepton colliders with a variety of collision energies are performed to estimate the allowed region on c6 and {c}_{Phi_1} . Especially we find that, with the help of exclusively choosing longitudinal polarizations in the final states and suitable pT cuts, WWh process is as important as the more widely studied triple Higgs production (hhh) in the measurement of Higgs self-couplings. Our analysis indicates that these processes can play important roles in the measurement of Higgs self-couplings at future 100 TeV pp colliders and muon colliders. However, their cross sections are generally tiny at low energy machines, which makes them much more challenging to explore.

Fiducial Higgs and Drell-Yan distributions at N3LL\u2032+NNLO with RadISH

We present state-of-the-art predictions for transverse observables relevant to colour-singlet production at the LHC, in particular the transverse momentum of the colour singlet in gluon-fusion Higgs production and in neutral Drell-Yan lepton-pair production, as well as the {phi}_{eta}^{ast } observable in Drell Yan. We perform a next-to-next-to-next-to-leading logarithmic (N3LL) resummation of such observables in momentum space according to the RadISH formalism, consistently including in our prediction all constant terms of relative order {alpha}_s^3 with respect to the Born, thereby achieving N3LL′ accuracy. The calculation is fully exclusive with respect to the Born kinematics, which allows the application of arbitrary fiducial selection cuts on the decay products of the colour singlet. We supplement our results with a transverse-recoil prescription, accounting for dominant classes of subleading-power corrections in a fiducial setup. The resummed predictions are matched with fixed-order differential spectra at next-to-next-to-leading order (NNLO) accuracy. A phenomenological comparison is carried out with 13 TeV LHC data relevant to the Higgs to di-photon channel, as well as to neutral Drell-Yan lepton-pair production. Overall, the inclusion of mathcal{O} ( {alpha}_s^3 ) constant terms, and to a lesser extent of transverse-recoil effects, proves beneficial for the comparison of theoretical predictions to data, leaving a residual theoretical uncertainty in the resummation region at the 2–5% level for Drell-Yan observables, and 5–7% in Higgs production.

Mixed QCD-EW corrections for Higgs leptonic decay via HW+W\u2212 vertex

We consider the two-loop corrections to the HW+W− vertex at order ααs. We construct a canonical basis for the two-loop integrals using the Baikov representation and the intersection theory. By solving the ϵ-form differential equations, we obtain fully analytic expressions for the master integrals in terms of multiple polylogarithms, which allow fast and accurate numeric evaluation for arbitrary configurations of external momenta. We apply our analytic results to the decay process H → νeeW, and study both the integrated and differential decay rates. Our results can also be applied to the Higgs production process via W boson fusion.

Searching for exotic production of Higgs boson + X to map out new physics

We propose leveraging our proficiency for detecting Higgs resonances by using the Higgs as a tagging object for new heavy physics. In particular, we argue that searches for exotic Higgs production from decays of color-singlet fields with electroweak charges could beat current searches at the LHC which look for their decays to vectors. As an example, we study the production and decay of vector-like leptons which admit Yukawa couplings with SM leptons. We find that bounds from Run 2 searches are consistent with anywhere from hundreds to many thousands of Higgses having been produced in their decays over the same period, depending on the representation. Dedicated searches for these signatures may thus be able to significantly improve our reach at the electroweak energy frontier.

Searches for dark matter via charged Higgs pair production in the Inert Doublet Model at a γγ collider * *Supported by the National Natural Science Foundation of China (11205003, 11305001, 11575002, 11935001)

The Inert Doublet Model (IDM) is one of the simplest extensions beyond the Standard Model (SM) with an extended scalar sector, which provides a scalar dark matter particle candidate. In this study, we investigated the double charged Higgs production at a collider. By scanning the whole parameter space, we obtained the parameter points corresponding to the correct relic abundance of dark matter. After applying all theoretical and experimental constraints, the parameter space for the existence of dark matter was extremely restricted. We performed an analysis of the signal of production in the IDM and the SM background, with the optimized selection conditions chosen for the kinematic variables to maximize the signal significance. Comparing the signal with the background, we obtained the parameter points that may be detected in future collider experiments.

Measurements of Higgs properties from CMS

<p indent=0mm>The Large Hadron Collider (LHC) exhibits the highest colliding energy in the world. The compact muon solenoid (CMS) is one of the main experiments conducted on the LHC, and its objective is to discover the Higgs boson and new particles. In this report, the discovery of the Higgs Boson and the measurements of Higgs properties using CMS RUN2 data were briefly presented. Higgs production modes—ggH, VBF, VH, and ttH—were observed using the CMS, and decay modes— ZZ to four leptons, diphotons, WW, ττ, and bb—were discovered using the CMS. Higgs coupling with vector bosons and third-generation fermions t, b, and τ were measured. Moreover, the Higgs mass, width, decay branching ratio, spin and parity, cross-section, and differential cross-section were studied. The results are consistent with those obtained using the standard model within an error range. The results are mainly obtained using 2016 data, and the errors are large. Nevertheless, the results will be improved when all RUN2 data analyses are published.

DiffExp, a Mathematica package for computing Feynman integrals in terms of one-dimensional series expansions

DiffExp is a Mathematica package for integrating families of Feynman integrals order-by-order in the dimensional regulator from their systems of differential equations, in terms of one-dimensional series expansions along lines in phase-space, which are truncated at a given order in the line parameter. DiffExp is based on the series expansion strategies that were explored in recent literature for the computation of families of Feynman integrals relevant for Higgs plus jet production with full heavy quark mass dependence at next-to-leading order. The main contribution of this paper, and its associated package, is to provide a public implementation of these series expansion methods, which works for any family of integrals for which the user provides a set of differential equations and boundary conditions (and for which the program is not computationally constrained). The main functions of the DiffExp package are discussed, and its use is illustrated by applying it to the three loop equal-mass and unequal-mass banana graph families. Program summaryProgram title: DiffExpCPC Library link to program files:https://doi.org/10.17632/j43fkg8vjt.1Developer's repository link:https://gitlab.com/hiddingm/diffexpLicensing provisions: GPLv3Programming language: Mathematica (Wolfram Language)Nature of problem: Obtaining high-precision numerical results for families of Feynman integrals in dimensional regularization, at arbitrary points in phase-space and in an efficient manner, from the system of differential equations satisfied by the integrals and a set of suitable boundary conditions.Solution method: The program provides a public implementation of the integration strategy outlined in Ref. [1]. A line is taken from a given boundary point to a point in phase-space at which numerical results are desired. The line is subdivided into multiple segments, and along each line segment the differential equations are solved in terms of one-dimensional series expansions with a radius of convergence that covers the respective line segment, and up to high order in the line parameter. Boundary conditions are transported by matching results along neighboring line segments. Branch points are crossed by analytically continuing logarithms and square roots that appear in the series expansions. By evaluating the series solutions of the last line segment at the endpoint, the desired numerical results are obtained.Additional comments including restrictions and unusual features: Depending on the complexity of the differential equations of the integrals, the package is limited by CPU speed and/or memory. The prefactors of the Feynman integrals in the basis of master integrals for which the differential equations are given, should only contain rational functions and/or square roots. Fine-tuning of the configuration options may be required for families involving sectors with a large numbers of coupled integrals. Reference[1]F. Moriello, J. High Energy Phys. 2020 (2020) 150. arXiv:1907.13234, https://doi.org/10.1007/JHEP01(2020)150.

Enhancement of the double Higgs production via leptoquarks at the LHC

Measurements of single Higgs production and its decays are in good agreement with the Standard Model. There is still room for large modifications in double Higgs production at LHC, though these effects may be correlated with large corrections to other observables, in particular single Higgs production. In this work we address the issue of enhancing double Higgs production in the presence of scalar leptoquarks while satisfying all experimental constraints. We show at leading order that including more than one species of leptoquarks, large cubic interactions with the Higgs can lead to sizable enhancement of di-Higgs production cross section at LHC, while at the same time keeping other Higgs observables and precision measurements under control. For masses above 800 GeV these corrections are in general below 30%, whereas in a viable scenario in which one of the leptoquarks can be light, specifically in the mass range 400 − 600 GeV, we show that it is possible to roughly double the SM cross section for di-Higgs production, implying that possible first hints of it may be probed at the high luminosity LHC at mathcal{L} ∼ 2 ab−1.

Probing the electroweak symmetry breaking with Higgs production at the LHC

The electroweak symmetry breaking (EWSB) mechanism is still an undecided question in particle physics. We propose to utilize the single top quark and Higgs associated production (th), Zh production via gluon fusion at the LHC to probe the couplings between the Higgs and the gauge bosons and further to test the EWSB. We demonstrate that the th and gg→Zh productions are sensitive to the relative sign of couplings (htt¯, hWW) and (htt¯, hZZ), respectively. We find that the relative sign between hWW and hZZ couplings could be fully determined after combining the present measurements from gg→h, tt¯h and the th, Zh channels, as well as tZj and Ztt¯ production at the 13 TeV LHC, and this conclusion is not sensitive to the possible new physics contribution induced by Ztt¯ couplings in the gg→Zh production.

On the interference of ggH and overline{mathrm{c}}mathrm{cH} Higgs production mechanisms and the determination of charm Yukawa coupling at the LHC

Higgs boson production in association with a charm-quark jet proceeds through two different mechanisms — one that involves the charm Yukawa coupling and the other that involves direct Higgs coupling to gluons. The interference of the two contributions requires a helicity flip and, therefore, cannot be computed with massless charm quarks. In this paper, we consider QCD corrections to the interference contribution starting from charm-gluon collisions with massive charm quarks and taking the massless limit, mc→ 0. The behavior of QCD cross sections in that limit differs from expectations based on the canonical QCD factorization. This implies that QCD corrections to the interference term necessarily involve logarithms of the ratio MH/mc whose resummation is currently unknown. Although the explicit next-to-leading order QCD computation does confirm the presence of up to two powers of ln(MH/mc) in the interference contribution, their overall impact on the magnitude of QCD corrections to the interference turns out to be moderate due to a cancellation between double and single logarithmic terms.

Measurements of Higgs bosons decaying to bottom quarks from vector boson fusion production with the ATLAS experiment at sqrt{s}=13,text {TeV}

The paper presents a measurement of the Standard Model Higgs Boson decaying to b-quark pairs in the vector boson fusion (VBF) production mode. A sample corresponding to 126 hbox {fb}^{-1} of sqrt{s} = 13,text {TeV} proton–proton collision data, collected with the ATLAS experiment at the Large Hadron Collider, is analyzed utilizing an adversarial neural network for event classification. The signal strength, defined as the ratio of the measured signal yield to that predicted by the Standard Model for VBF Higgs production, is measured to be 0.95^{+0.38}_{-0.36} , corresponding to an observed (expected) significance of 2.6 (2.8) standard deviations from the background only hypothesis. The results are additionally combined with an analysis of Higgs bosons decaying to b-quarks, produced via VBF in association with a photon.