Higgs Boson Properties Research Articles

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We introduce a phenomenological model for a string-derived Z′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Z^\\prime $$\\end{document} scenario, and study its predictions for the mass of the W boson. In the process, we compare it to collider constraints for both pair-produced particles, Higgs boson properties, and Z′\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Z^\\prime $$\\end{document} searches. We also describe the implementation of new tools in the scanning code BSMArt.

Testing complex singlet scalar cosmology at the Large Hadron Collider

The Standard Model extended with a complex singlet scalar (cxSM) can admit a strong first order electroweak phase transition (SFOEWPT) as needed for electroweak baryogenesis and provide a dark matter (DM) candidate. The presence of both a DM candidate and a singlet-like scalar that mixes with the Standard Model Higgs boson leads to the possibility of a bb¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ b\\overline{b} $$\\end{document} + MET final state in pp collisions. Focusing on this channel, we analyze the prospective reach at the Large Hadron Collider (LHC) for a heavy singlet-like scalar in regions of cxSM parameter space compatible with a SFOEWPT and DM phenomenology. We identify this parameter space while implementing current constraints from electroweak precision observable and Higgs boson property measurements as well as those implied by LHC heavy resonance searches. Implementing a proposed search strategy, we find that the heavy scalar and DM candidate can be probed up to 1 TeV and 450 GeV at 2σ level respectively.

Higgs physics research: yesterday, today, and tomorrow

<sec>This article reviews the discovery of the Higgs boson, discusses the studies of its properties, and introduces the physical prospects of the future Higgs factories.</sec><sec>The greatest goal of particle physics is to understand the fundamental particles of the universe and how they interact with each other (or more generally, how the universe operates). In the Standard Model of particle phyiscs, the Higgs mechanism is proposed to explain the origin of elementary particle mass and predict the existence of the Higgs boson. Higgs physics is one of the most important research areas in particle physics.</sec><sec>The Large Hadron Collider (LHC) at CERN (Geneva, Switzerland) accelerates proton beams to collide at center-of-mass energy of 13 TeV, thus defining the world's energy frontier. The ATLAS and CMS detectors are two general-purpose detectors at the LHC for studying the debris from the collisions.</sec><sec>The Higgs boson was discovered in the ATLAS and CMS experiments in 2012. This discovery completed the fundamental particle spectrum of the Standard Model and was an important milestone for particle physics. Since then, many studies have been conducted on the properties of Higgs boson, including spin, mass and couplings, to deepen our understanding of the Higgs mechanism. In particular, the Higgs bosons coupling to fermions and to themselves present new kinds of fundamental interactions with paramount significance, which have not been fully confirmed. Additionally, the Higgs bosons have become an important tool to search for dark matter, heavy resonance, and other new physical phenomena. So far, there has been no deviation from the predictions of the Standard Model.</sec><sec>Looking forward to the future, it is proposed to use the electron-positron collisions to study the Higgs boson in more depth. Physics studies have shown that these Higgs factories can significantly improve the accuracy of many properties of the Higgs boson, including width and couplings, and provide great physics prospects.</sec>

Precision Measurements of Higgs-boson Properties with the ATLAS Experiment

Precision Measurements of Higgs-boson Properties with the ATLAS Experiment

Conceptual Design of CEPC Detector Magnet

The Circular Electron Positron Collider (CEPC) will measure the Higgs boson properties in great detail. The detector needs a 3 Tesla superconducting solenoid followed by a muon detector embedded in a flux return yoke. This paper introduces the conceptual design of the superconducting solenoid includes two schemes based on LTS and HTS technology. The fundamental parameters and structures of magnets are discussed, and the advancements in electromagnetic design, quench calculation, cryogenic system design, and conductor development are outlined. The conductors used in the two schemes, the aluminum stabilized NbTi/Cu Rutherford cable and the Aluminum stabilized Stacked REBCO Tape Cable (ASTC), are also under development. The viability of the first-ever HTS aluminum stabilized cable proposal is confirmed, and the technology of co-extrusion aluminum coating has been preliminary mastered.

Future accelerator projects: new physics at the energy frontier

High-energy colliders provide direct access to the energy frontier, allowing to search for new physics at scales as high as the machine’s center-of-mass energy, perform precision measurements of the Standard Model (SM) parameters, including those related to the flavor sector, and determine the Higgs boson properties and their connection to electroweak symmetry breaking. Each proposed future collider option has its own specific science goals and capabilities, depending on the designed running energy (energies) amongst other parameters. In this paper, an overview of the discovery potential of future circular and linear colliders is presented. Results from searches for beyond the Standard Model (BSM) phenomena at proton–proton, proton–electron, electron–positron, and muon–antimuon colliders are summarized.

Observation of electroweak production of two jets and a Z-boson pair

Electroweak symmetry breaking explains the origin of the masses of elementary particles through their interactions with the Higgs field. Besides the measurements of the Higgs boson properties, the study of the scattering of massive vector bosons with spin 1 allows the nature of electroweak symmetry breaking to be probed. Among all processes related to vector-boson scattering, the electroweak production of two jets and a Z-boson pair is a rare and important one. Here we report the observation of this process from proton–proton collision data corresponding to an integrated luminosity of 139 fb−1 recorded at a centre-of-mass energy of 13 TeV with the ATLAS detector at the Large Hadron Collider. We consider two different final states originating from the decays of the Z-boson pair: one containing four charged leptons and another containing two charged leptons and two neutrinos. The hypothesis of no electroweak production is rejected with a statistical significance of 5.7σ, and the measured cross-section for electroweak production is consistent with the Standard Model prediction. In addition, we report cross-sections for inclusive production of a Z-boson pair and two jets for the two final states.

COMPUTER MODELING OF tth(H) HIGGS BOSON PRODUCTION WITH MSSM MODEL

We studied the properties of the MSSM Higgs bosons, h and H through the decay into b-quarks in associated production with a top-quark pair. There was used the tree-level Higgs sector described by two parameters MA and tanβ and found their optimal values according to experimental data of ATLAS detector. Using the restricted parameter space we calculated cross sections of associated tth(H) production at 13 and 14 TeV, the corresponding kinematical cuts, mass distributions and Branching Ratios of h and H decays into bb quark pair.

Some Basic Properties of Higgs Bosons

Known as one of the most hopeful fields to find the new particle—Higgs bosons and become even more important after it is proved by Higgs. Higgs and his colleagues further improve their observation of the Higgs Bosons through the Higgs mechanism. This paper will show the basic properties of the Higgs bosons, and some machines of the Higgs bosons. The spontaneous symmetry breaking, and the Higgs mechanism have also been introduced due to their necessity for the Higgs boson. This paper will be an introduction for anyone who is interested in this field.

Synchrotron radiation from final doublet magnets in CEPC MDI

The Circular Electron Positron Collider (CEPC) is a proposed Higgs factory with center-of-mass energy of 240[Formula: see text]GeV to measure the properties of Higgs boson and test the standard model accurately. Synchrotron radiation (SR) generated from the final doublet (FD) magnets in the interaction region of CEPC double ring scheme is one of the typical issues. SR photons can contribute to the heat load of the beam pipe and cause photon background to the experiments. Furthermore, the radiation dose can damage detector components. In this paper, SR generated from FD magnets is analyzed when beam is with tails and offset. SR from the dipole leakage field of the FD superconducting magnets is also analyzed and the physics limit is given to protect the detector.

Beam loss background with magnet errors and beam–beam effect in CEPC

The Circular Electron Positron Collider (CEPC) is a proposed Higgs factory with center-of-mass energy of 240[Formula: see text]GeV to measure the properties of Higgs boson and test the standard model accurately. Beam loss background in detectors is an important topic at CEPC. During manufacture and installation, magnets are not perfect and with many kinds of errors. Beam–beam interaction in high-energy electron positron collider is the action of external field force, which changes the momentum of each beam bunch. Thus, beam loss background can be affected by the magnet errors and beam–beam effect. In this paper, the beam loss background with magnet errors and beam–beam effect is simulated in CEPC.

Higgs boson properties and supersymmetry: Constraints and sensitivity from the LHC to ane+e−collider

The study of the Higgs boson properties offers compelling perspectives for testing the effects of physics beyond the Standard Model and has deep implications for the LHC program and future colliders. Accurate determinations of the Higgs boson properties can provide us with a distinctively precise picture of the Higgs sector, set tight bounds, and predict ranges for the values of new physics model parameters. In this paper, we discuss the constraints on supersymmetry that can be derived by a determination of the Higgs boson mass and couplings. We quantify these constraints by using scans of the 19-parameter space of the so-called phenomenological minimal supersymmetric Standard Model. The fraction of scan points that can be excluded by the Higgs measurements is studied for the coupling measurement accuracies obtained in LHC run 2 and expected for the HL-LHC program and ${e}^{+}{e}^{\ensuremath{-}}$ colliders and contrasted with those derived from missing transverse energy searches at the LHC and from dark matter experiments.

The mass-degenerate SM-like Higgs and anomaly of (g − 2)μ in μ-term extended NMSSM

We chose the μ-term extended next-to-minimal supersymmetric standard model (μNMSSM) for this work, and we perform a phenomenological study based on the assumption that the observed Standard Model (SM)-like Higgs is explained by the presence of a double overlapping resonance and in light of the recent (g − 2)μ result. The study also takes into account a variety of experimental results, including Dark Matter (DM) direct detections and results from sparticle searches at the Large Hadron Collider (LHC). We study the properties of DM confronted with the limits from DM direct detections. As a second step, we focus our attention on the properties of the mass-degenerate SM-like Higgs bosons and on explaining the anomaly of (g −2)μ. We conclude that the anomaly of (g −2)μ can be explained in the scenario with two mass-degenerate SM-like Higgs, and there are samples that meet the current constraints and fit 1 − σ anomalies of Higgs data.

On the W mass and new Higgs bosons

We discuss the prediction of the W boson mass in a simple extension of the Standard Model (ΣSM) with a real scalar triplet. A shift in the W mass as reported by the CDF II collaboration can naturally be accommodated by the model without modifying the Standard Model value for the Z mass. We discuss the main implications and the properties of the new Higgs bosons. Namely, the partial decay widths of the new charged Higgs are predicted. Furthermore, the neutral Higgs has suppressed couplings to fermions and decays predominantly into a pair of W gauge bosons.

Constraints on Higgs boson properties using WW^{*}(rightarrow enu mu nu )jj production in 36.1,mathrm{fb}^{-1} of sqrt{s}=13 TeV pp collisions with the ATLAS detector

This article presents the results of two studies of Higgs boson properties using the WW^*(rightarrow enu mu nu )jj final state, based on a dataset corresponding to {36.1}{{mathrm{fb}}^{-1}} of sqrt{s}=13 TeV proton–proton collisions recorded by the ATLAS experiment at the Large Hadron Collider. The first study targets Higgs boson production via gluon–gluon fusion and constrains the CP properties of the effective Higgs–gluon interaction. Using angular distributions and the overall rate, a value of tan (alpha ) = 0.0 pm 0.4 (mathrm {stat.}) pm 0.3 (mathrm {syst.}) is obtained for the tangent of the mixing angle for CP-even and CP-odd contributions. The second study exploits the vector-boson fusion production mechanism to probe the Higgs boson couplings to longitudinally and transversely polarised W and Z bosons in both the production and the decay of the Higgs boson; these couplings have not been directly constrained previously. The polarisation-dependent coupling-strength scale factors are defined as the ratios of the measured polarisation-dependent coupling strengths to those predicted by the Standard Model, and are determined using rate and kinematic information to be a_mathrm {L}=0.91^{+0.10}_{-0.18}(stat.)^{+0.09}_{-0.17}(syst.) and a_{mathrm {T}}=1.2 pm 0.4 (stat.) ^{+0.2}_{-0.3} (syst.). These coupling strengths are translated into pseudo-observables, resulting in kappa _{VV}= 0.91^{+0.10}_{-0.18}(stat.)^{+0.09}_{-0.17}(syst.) and epsilon _{VV} =0.13^{+0.28}_{-0.20} (stat.)^{+0.08}_{-0.10}(syst.). All results are consistent with the Standard Model predictions.

Learning to increase matching efficiency in identifying additional b-jets in the text {t}bar{text {t}}text {b}bar{text {b}} process

The text {t}bar{text {t}}text {H}(text {b}bar{text {b}}) process is an essential channel in revealing the Higgs boson properties; however, its final state has an irreducible background from the text {t}bar{text {t}}text {b}bar{text {b}} process, which produces a top quark pair in association with a b quark pair. Therefore, understanding the text {t}bar{text {t}}text {b}bar{text {b}} process is crucial for improving the sensitivity of a search for the text {t}bar{text {t}}text {H}(text {b}bar{text {b}}) process. To this end, when measuring the differential cross section of the text {t}bar{text {t}}text {b}bar{text {b}} process, we need to distinguish the b-jets originating from top quark decays and additional b-jets originating from gluon splitting. In this paper, we train deep neural networks that identify the additional b-jets in the {text {t}}{bar{text {t}}}{text {b}}{bar{text {b}}} events under the supervision of a simulated text{t}bar{text{t}}text{b}bar{text{b}} event data set in which true additional b-jets are indicated. By exploiting the special structure of the text {t}bar{text {t}}text {b}bar{text {b}} event data, several loss functions are proposed and minimized to directly increase matching efficiency, i.e., the accuracy of identifying additional b-jets. We show that, via a proof-of-concept experiment using synthetic data, our method can be more advantageous for improving matching efficiency than the deep learning-based binary classification approach presented in [1]. Based on simulated text {t}bar{text {t}}text {b}bar{text {b}} event data in the lepton+jets channel from pp collision at sqrt{s} = 13 TeV, we then verify that our method can identify additional b-jets more accurately: compared with the approach in [1], the matching efficiency improves from 62.1% to 64.5% and from 59.9% to 61.7% for the leading order and the next-to-leading order simulations, respectively.

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.

Theory of Dirac dark matter: Higgs boson decays and EDMs

We discuss a simple theory predicting the existence of a Dirac dark matter candidate from gauge anomaly cancellation. In this theory, the spontaneous breaking of the local baryon number at the low scale can be understood. We show that the constraint from the dark matter relic abundance implies an upper bound on the theory of a few tens of TeV. We study the correlation between the dark matter constraints and the prediction for the electric dipole moment of the electron. We point out the implications for the diphoton decay width of the Standard Model Higgs boson. Furthermore, we study the decays of the new Higgs boson presented in the theory, and we show that the branching ratio into two photons can be large. We also discuss the correlation between the dark matter constraints and the properties of the new Higgs boson decays. This theory could be tested at current or future experiments by combining the results from dark matter, collider, and electric dipole moment experiments.

Curing tachyonic tree-level syndrome in NMSSM light-singlet scenarios

Models with an extended Higgs sector open up the phenomenological possibility of additional scalars, beyond the SM-like boson observed by the LHC, with mass at or below the electroweak scale. Such scenarios are in particular viable in the presence of electroweak-singlet spin-0 fields, as expected for instance in the context of the NMSSM. Given that the size of radiative corrections can substantially affect the Higgs potential, a negative squared mass at the tree level does not necessarily yield a tachyonic spectrum at the physical level, but only indicates a failure of the tree-level description for calculational purposes. We explain how to tackle this technical issue in the example of the NMSSM, in scenarios with light mathcal {CP}-odd or mathcal {CP}-even singlet-dominated states and show how loop corrections to the Higgs masses and decay widths can be derived with the regularized Lagrangian. We further explore how the same flexibility in the definition of tree-level parameters can be exploited to circumvent large deviations of the tree-level spectrum from the kinematical setup in Higgs decays, or to estimate the theoretical uncertainty associated with the discrepancy between tree-level and physical Higgs spectra. The latter is of particular relevance for the properties of the SM-like Higgs boson in supersymmetry-inspired models.

Study of Events with Two Leptons in the Final State to Investigate Properties of the Standard Model Higgs Boson and Search for a Heavy Higgs Boson in the h/H → WW(*) → 𝓁ν𝓁ν Decay in pp Collisions at 13 TeV with the ATLAS Detector at the LHC

Study of Events with Two Leptons in the Final State to Investigate Properties of the Standard Model Higgs Boson and Search for a Heavy Higgs Boson in the h/H → WW(*) → 𝓁ν𝓁ν Decay in pp Collisions at 13 TeV with the ATLAS Detector at the LHC