Higgs Boson Production Processes Research Articles

Higgs Boson Searches at the LHC Beyond the Standard Model

The latest results of Higgs boson searches beyond the Standard Model from the ATLAS and CMS experiments are reviewed. This includes searches for additional neutral, charged, and double charged Higgs-like bosons, searches for dark matter produced in association with a Higgs boson, and searches for new physics in Higgs boson production and decay processes. Interpretations are given within the hMSSM, a special parameterization of the Minimal Supersymmetric extension of the Standard Model, in which the mass of the lightest Higgs boson is set to the value of 125 GeV measured at the LHC.

Exploring nonstandard Hbb¯ interactions at future electron-proton colliders

In this paper, we use the charged-current Higgs boson production process at future electron-proton colliders, e−p→Hjνe, with the subsequent decay of the Higgs boson into a bb¯ pair, to probe the Standard Model effective field theory with dimension-six operators involving the Higgs boson and the bottom quark. The study is performed for two proposed future high-energy electron-proton colliders, the Large Hadron Electron Collider (LHeC) and the Future Circular Collider (FCC-he) at the center-of-mass energies of 1.3 TeV and 3.46 TeV, respectively. Constraints on the CP-even and CP-odd Hbb¯ couplings are derived by analyzing the simulated signal and background samples. A realistic detector simulation is performed and a multivariate technique using the gradient boosted decision trees algorithm is employed to discriminate the signal from background. Expected limits are obtained at 95% confidence level for the LHeC and FCC-he assuming the integrated luminosities of 1, 2 and 10 ab−1. We find that using 1 ab−1 of data, the CP-even and CP-odd Hbb¯ couplings can be constrained with accuracies of the order of 10−3 and 10−2, respectively, and a significant region of the unprobed parameter space becomes accessible. Published by the American Physical Society 2024

Refining the GENEVA method for Higgs boson production via gluon fusion

We describe a number of improvements to the Geneva method for matching NNLO calculations to parton shower programs. In particular, we detail changes to the resummed calculation used in the matching procedure, including disentangling the cross section dependence on factorisation and beam scales, and an improved treatment of timelike logarithms. We also discuss modifications in the implementation of the splitting functions which serve to make the resummed calculation differential in the higher multiplicity phase space. These changes improve the stability of the numerical cancellation of the nonsingular term at small values of the resolution parameter. As a case study, we consider the gluon-initiated Higgs boson production process gg → H. We validate the NNLO accuracy of our predictions against independent calculations, and compare our showered and hadronised results with recent data taken at the ATLAS and CMS experiments in the diphoton decay channel, finding good agreement.

Гипотеза о контракции калибровочной группы Стандартной модели и экспериментальные данные БАК

Within the framework of the contraction hypothesis of the
 gauge group of the Standard Model, the behavior of the amplitude
 of the dominant Higgs boson production process in the
 four-lepton decay with an increasing temperature T is analyzed.
 It is shown that the modified process breaks down into
 a number of channels depending on the contribution of the
 color components in the loop of virtual quarks, leading to the
 creation of the Higgs boson. The dependence on T of the cross
 section of each channel is found. Comparison with LHC data
 on Higgs boson creation cross sections at energies (temperatures)
 of 7, 8, 13, and 14 TeV showed that the hypothesis about
 the contraction of the gauge group of the Standard Model does
 not contradict these data.

Full electroweak 𝒪(α) corrections to Higgs-boson production processes with beam polarization at the International Linear Collider

Abstract We present the full ${{\cal O}}(\alpha )$ electroweak radiative corrections to the production of nine Higgs bosons with beam polarization at the International Linear Collider (ILC). The computation is performed with the help of GRACE-Loop. We compare the full ${{\cal O}}(\alpha )$ electroweak radiative corrections with the factorized initial-state radiation (ISR) effects to estimate the pure weak corrections. This reveals that the pure weak corrections are not negligible and should be taken into account for precision measurements of the Higgs-boson property at the ILC experiments.

Higgs triplet extension of GRACE

Much theoretical effort and automatization are required to confront new physics models with experimental data for many types of particle reactions at future colliders. In this context, we extend Grace, an automatic calculation system for invariant amplitudes, to incorporate particles and interactions in the Georgi–Machacek model. With the extended Grace system, we study fermiophobic Higgs boson production processes at e^+ e^- and e^- e^- colliders in the model. The results show some advantages of e^- e^- colliders over e^+ e^- colliders for new physics search and thus its complementary role.

Anomalous couplings in associated VH production with Higgs boson decay to massive b quarks at NNLO in QCD

We combine the NNLO QCD description of Higgs boson production in association with an electroweak vector boson $V = W~{\rm or}~Z$ with a similarly-precise description of Higgs boson decays into a pair of massive $b$ quarks and with the anomalous couplings that modify interactions of the Higgs and electroweak vector bosons. The resulting numerical code provides the most advanced theoretical tool to investigate such anomalous couplings in the associated Higgs boson production process. We study the impact of anomalous couplings on fiducial cross sections and differential distributions and argue that, with increased QCD precision, smaller anomalous couplings become accessible in kinematic regions where the effects of higher-dimensional operators in the Standard Model Effective Field Theory remain small and the EFT expansion is under control.

Double Higgs boson production at e+e− colliders in the two-Higgs-doublet model

We study the double Higgs boson production processes $e^+e^- \to hh f\bar{f}$ ($f\neq t$) with $h$ being the 125 GeV Higgs boson in the two-Higgs-doublet model with a softly-broken $Z_2$ symmetry. The cross section can be significantly enhanced, typically a few hundreds percent, as compared to the standard model prediction due to resonant effects of heavy neutral Higgs bosons, which becomes important in the case without the alignment limit. We find a strong correlation between the enhancement factor of the cross section and the scaling factor of the $hf\bar{f}$ couplings under constraints from perturbative unitarity, vacuum stability and current experimental data at the LHC as well as the electroweak precision data.

Renormalization of mixing angles

We discuss the renormalization of mixing angles for theories with extended scalar sectors. Motivated by shortcomings of existing schemes for mixing angles, we review existing renormalization schemes and introduce new ones based on on-shell conditions or symmetry requirements such as rigid or background-field gauge invariance. Considering in particular the renormalization of the mixing angles in the Two-Higgs-Doublet Model and the Higgs-Singlet Extension of the Standard Model, we compare electroweak corrections within these models for a selection of renormalization schemes. As specific examples, we present next-to-leading-order results on the four-fermion decays of heavy and light CP-even Higgs bosons, H1/H2 → WW/ZZ → 4f , and on electroweak Higgs-boson production processes, i.e. Higgs-strahlung and vector-boson fusion. We find that our new proposals for on-shell and symmetry-based renormalization conditions are well-behaved for the considered benchmark scenarios in both models.

Measurements of Higgs boson properties in the diphoton decay channel with 36 fb−1 of pp collision data at s=13 TeV with the ATLAS detector

Properties of the Higgs boson are measured in the two-photon final state using 36.1 fb$^{-1}$ of proton-proton collision data recorded at $\sqrt{s} = 13$ TeV by the ATLAS experiment at the Large Hadron Collider. Cross-section measurements for the production of a Higgs boson through gluon-gluon fusion, vector-boson fusion, and in association with a vector bosonor a top-quark pair are reported. The signal strength, defined as the ratio of the observed to the expected signal yield, is measured for each of these production processes as well as inclusively. The global signal strength measurement of $0.99 \pm 0.14$ improves on the precision of the ATLAS measurement at $\sqrt{s} = 7$ and 8 TeV by a factor of two. Measurements of gluon-gluon fusion and vector-boson fusion productions yield signal strengths compatible with the Standard Model prediction. Measurements of simplified template cross sections, designed to quantify the different Higgs boson production processes in specific regions of phase space, are reported. The cross section for the production of the Higgs boson decaying to two isolated photons in a fiducial region closely matching the experimental selection of the photons is measured to be $55 \pm 10$ fb, which is in good agreement with the Standard Model prediction of $64 \pm 2$ fb. Furthermore, cross sections in fiducial regions enriched in Higgs boson production in vector-boson fusion or in association with large missing transverse momentum, leptons or top-quark pairs are reported. Differential and double-differential measurements are performed for several variables related to the diphoton kinematics as well as the kinematics and multiplicity of the jets produced in association with a Higgs boson. No significant deviations from a wide array of Standard Model predictions are observed.

Thermal radiation and entanglement in proton-proton collisions at energies available at the CERN Large Hadron Collider

The origin of the apparent thermalization in high-energy collisions is investigated using the data of the ATLAS and CMS Collaborations at the LHC. For this purpose, we analyze the transverse momentum distributions in the following proton-proton collision processes, all at $\sqrt{s} = 13$ TeV: i) inclusive inelastic $pp$ collisions; ii) single- and double-diffractive Drell-Yan production $pp \to \mu^+ \mu^- X$; and iii) Higgs boson production. We confirm the relation between the effective temperature and the hard scattering scale observed at lower energies, and find that it extends even to the Higgs boson production process. In addition we find that the thermal component disappears in diffractive events (even though many charged hadrons are still produced). We discuss the implications of our study for the mechanism of multi-particle production -- in particular, we test the hypothesis about the link between quantum entanglement and thermalization in high-energy collisions.

Higgs boson production in the littlest Higgs model with T-parity at the ILC

We investigate the Higgs boson production processes [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] in the littlest Higgs model with T-parity (LHT) at the International Linear Collider (ILC). We calculate the LHT model predictions on the production rate of these processes at the ILC in the case of (un)polarized beams and the signal strengths of the production processes [Formula: see text] and [Formula: see text] with Higgs decaying to [Formula: see text]. In the allowed parameter space, we find that the signal strengths [Formula: see text] is most likely approach to the expected precision of the ILC.

125 GeV Higgs boson mass from 5D gauge-Higgs unification

In the context of a simple gauge-Higgs unification (GHU) scenario based on the gauge group SU(3)$\times$U(1)$^\prime$ in a 5-dimensional flat space-time, we investigate a possibility to reproduce the observed Higgs boson mass of around 125 GeV. We introduce bulk fermion multiplets with a bulk mass and a (half) periodic boundary condition. In our analysis, we adopt a low energy effective theoretical approach of the GHU scenario, where the running Higgs quartic coupling is required to vanish at the compactification scale. Under this "gauge-Higgs condition," we investigate the renormalization group evolution of the Higgs quartic coupling and find a relation between the bulk mass and the compactification scale so as to reproduce the 125 GeV Higgs boson mass. Through quantum corrections at the one-loop level, the bulk fermions contribute to the Higgs boson production and decay processes and deviate the Higgs boson signal strengths at the Large Hadron Collider (LHC) experiments from the Standard Model (SM) predictions. Employing the current experimental data which show the the Higgs boson signal strengths for a variety of Higgs decay modes are consistent with the SM predictions, we obtain lower mass bounds on the lightest mode of the bulk fermions.

Monte Carlo simulations of Higgs-boson production at the LHC with the KrkNLO method

We present numerical tests and predictions of the KrkNLO method for matching of NLO QCD corrections to hard processes with LO parton-shower Monte Carlo generators (NLO+PS). This method was described in detail in our previous publications, where it was also compared with other NLO+PS matching approaches (MC@NLO and POWHEG) as well as fixed-order NLO and NNLO calculations. Here we concentrate on presenting some numerical results (cross sections and distributions) for Z/gamma ^* (Drell–Yan) and Higgs-boson production processes at the LHC. The Drell–Yan process is used mainly to validate the KrkNLO implementation in the Herwig 7 program with respect to the previous implementation in Sherpa. We also show predictions for this process with the new, complete, MC-scheme parton distribution functions and compare them with our previously published results. Then we present the first results of the KrkNLO method for Higgs production in gluon–gluon fusion at the LHC and compare them with MC@NLO and POWHEG predictions from Herwig 7, fixed-order results from HNNLO and a resummed calculation from HqT, as well as with experimental data from the ATLAS collaboration.

The use of Higgs boson production process for optimization of hadron calorimeter segmentation

A new approach to the determination of the optimum transverse segmentation of the hadron calorimeter using the Higgs boson production process via the vector boson fusion mechanism is considered. Monte Carlo simulation results are presented for the hadron calorimeter which will be installed after the modernization of 2023 in the Compact Muon Superdetector collaboration at the Large Hadron Collider of the CERN.

Identification of tagging jets in VBF H→τ−τ+ process with CMS experiment on Large Hadron Collider at large amount of additionally imposed pp-interactions

The procedure of identification of tagging jets in the Higgs boson production process with a following decay of the Higgs boson to τ-leptons (VBF H→τ−τ+) at the endcup region of the upgraded CMS detector at large amount (140) of additionally imposed pp-interactions is given. The efficiency and purity of tagging jets selection at the CMS endcup region are estimated.

Measuring rare and exclusive Higgs boson decays into light resonances

We evaluate the LHC's potential of observing Higgs boson decays into light elementary or composite resonances through their hadronic decay channels. We focus on the Higgs boson production processes with the largest cross sections, $pp\to h$ and $pp\to h+\mathrm{jet}$, with subsequent decays $h \to ZA$ or $h\to Z\,\eta_c$, and comment on the production process $pp\to hZ$. By exploiting track-based jet substructure observables and extrapolating to $3000~\mathrm{fb}^{-1}$ we find ${\cal BR}(h \to ZA) \simeq {\cal BR}(h \to Z \eta_c) \lesssim 0.02$ at 95% CL. We interpret this limit in terms of the 2HDM Type 1. We find that searches for $h\to ZA$ are complementary to existing measurements and can constrain large parts of the currently allowed parameter space.

Comparison of associated Higgs boson-radion and Higgs boson pair production processes

Many models, in particular, the brane-world models with two branes, predict the existence of the scalar radion, whose mass can be somewhat smaller than those of all the Kaluza-Klein modes of the graviton and Standard Model (SM) particles. Due to its origin the radion interacts with the trace of the energy-momentum tensor of the SM. The fermion part of the radion interaction Lagrangian is different from that for the SM Higgs boson due to the presence of additional terms playing a role for off-shell fermions. It was shown previously that for the case of the single radion and single Higgs boson production processes in association with an arbitrary number of SM gauge bosons all the contributions to the perturbative amplitudes appearing due to these additional terms were cancelled out making the processes similar up to a replacement of masses and overall coupling constants. For the case of the associated Higgs boson-radion and the Higgs boson pair production processes involving the SM gauge bosons the similarity property also takes place. However a detailed consideration shows that in this case it is not enough to replace simply the masses and the constants ($m_h \rightarrow m_r$ and $v \rightarrow \Lambda_r$). One should also rescale the triple Higgs coupling by the factor $\xi \equiv 1 + \frac{m_r^2 - m_h^2}{3m_h^2}$.

Higgs boson production in the U(1)B−L model at the ILC

In the framework of the minimal [Formula: see text] extension of the Standard Model, we investigate the Higgs boson production processes [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] at the International Linear Collider (ILC). We present the production cross-sections, the relative corrections and compare our results with the expected experimental accuracies for Higgs decay channel [Formula: see text]. In the allowed parameter space, we find that the effects of the three single Higgs boson production processes might approach the observable threshold of the ILC. But the Higgs signal strengths [Formula: see text] of the two double Higgs boson production processes are all out of the observable threshold so that these effects will be difficult to be observed at the ILC.

Probing CP violation in e + e − production of the Higgs boson and toponia

We study the CP violation in the Higgs boson and toponia production process at the ILC where the toponia are produced near the threshold. With the approximation that the production vertex of the Higgs boson and toponia is contact, and neglecting the P-wave toponia, we analytically calculated the density matrix for the production and decay of the toponia. Under these assumptions, the production spectrum of the toponia is solely determined by the spin quantum number, therefore the toponia can be either singlet or triplet. We find that the production rate of the singlet toponium is highly suppressed, and behaves just like the production of a P-wave toponia. In the case of the triplet toponium, three completely independent CP observables, namely azimuthal angles of lepton and anti-lepton in the toponium rest-frame as well as their sum, are predicted based on our analytical results, and checked by using the tree-level event generator. The non-trivial correlations come from the longitudinal-transverse interferences for the azimuthal angles of leptons, and the transverse-transverse interference for their sum. These three observables are well defined at the ILC, where the rest frame of the toponium can be reconstructed directly. Furthermore, the QCD-strong corrections, which are important near the threshold region, are also studied with the approximation of spin-independent QCD-Coulomb potential. While the total cross section is enhanced, the spin correlations predicted in this paper are not affected.