Minimal Standard Model Higgs Boson Research Articles

Search for minimal supersymmetric standard model Higgs Bosons H/A and for a [Formula: see text] boson in the [Formula: see text] final state produced in pp collisions at [Formula: see text] TeV with the ATLAS detector.

A search for neutral Higgs bosons of the minimal supersymmetric standard model (MSSM) and for a heavneutral Z^{prime } boson is performed using a data sample corresponding to an integrated luminosity of 3.2 fb^{-1} from proton–proton collisions at sqrt{s} = 13 {mathrm {TeV}} recorded by the ATLAS detector at the LHC. The heavy resonance is assumed to decay to a tau ^+ tau ^- pair with at least one tau lepton decaying to final states with hadrons and a neutrino. The search is performed in the mass range of 0.2–1.2 {mathrm {TeV}} for the MSSM neutral Higgs bosons and 0.5–2.5 {mathrm {TeV}} for the heavy neutral Z^{prime } boson. The data are in good agreement with the background predicted by the Standard Model. The results are interpreted in MSSM and Z^{prime } benchmark scenarios. The most stringent constraints on the MSSM m_A–tan beta space exclude at 95 % confidence level (CL) tan beta > 7.6 for m_A = 200 text {GeV} in the m_{h}^{text {mod+}} MSSM scenario. For the Sequential Standard Model, a Z^{prime }_mathrm {SSM} mass up to 1.90 {mathrm {TeV}} is excluded at 95 % CL and masses up to 1.82–2.17 {mathrm {TeV}} are excluded for a Z^{prime }_{mathrm {SFM}} of the strong flavour model.

Criteria for natural hierarchies

With the discovery of a particle that seems rather consistent with the minimal Standard Model Higgs boson, attention turns to questions of naturalness, fine-tuning, and what they imply for physics beyond the Standard Model and its discovery prospects at run II of the LHC. In this article we revisit the issue of naturalness, discussing some implicit assumptions that underly some of the most common statements, which tend to assign physical significance to certain regularization procedures. Vague arguments concerning fine-tuning can lead to conclusions that are too strong and perhaps not as generic as one would hope. Instead, we explore a more pragmatic definition of the hierarchy problem that does not rely on peeking beyond the murky boundaries of quantum field theory: we investigate the fine-tuning of the electroweak scale associated with thresholds from heavy particles, which is both calculable and dependent on the nature of the would-be ultraviolet completion of the Standard Model. We discuss different manifestations of new high-energy scales that are favored by experimental hints for new physics with an eye toward making use of fine-tuning in order to determine natural regions of the new physics parameter spaces.

Hadronic production of a MSSM Higgs boson with a pair of stops at the LHC

We present the next-to-leading order supersymmetric-QCD corrections to the production of a light neutral minimal supersymmetric standard model Higgs boson with a pair of supersymmetric scalar partners of the top quark at next-to-leading order at the LHC. We study the dependence of the lowest order total cross section on both the renormalization/factorization scale and the Higgs mass in the framework of minimal supergravity, taking the point SPS1a as a benchmark, for the numerical calculations. The renormalization/factorization scale dependence of the lowest order total cross section is strong. Including the next-to-leading order supersymmetric-QCD corrections significantly reduces and stabilizes the dependence of the lowest order total cross section on the renormalization/factorization scale.

Higgs physics with ATLAS

The discovery potential of the ATLAS experiment at the CERN Large Hadron Collider (LHC) also includes the Higgs boson. Several channels important for the discovery or exclusion of the Standard Model (SM) and the Minimal Supersymmetric Standard Model Higgs boson(s) are reviewed. Measurements of the properties of a Higgs-like particle are also briefly discussed.

Light Minimal Supersymmetric Standard Model Higgs Boson Scenario and its Test at Hadron Colliders

We show that, in the minimal supersymmetric standard model, the possibility for the lightest CP-even Higgs boson to be lighter than Z boson (as low as about 60 GeV) is, contrary to the usual belief, not yet excluded by the CERN LEP2 Higgs search nor any direct searches for supersymmetric particles at high energy colliders. The characteristic of the light Higgs boson scenario (LHS) is that the ZZh coupling and the decay branching ratio Br(h/A-->bb) are simultaneously suppressed as a result of generic supersymmetric loop corrections. Consequently, the W(+/-)H(-/+)h coupling has to be large due to the sum rule of Higgs couplings to weak gauge bosons. We discuss the potential of the Fermilab Tevatron and B factories to test the LHS, and show that the associated neutral and charged Higgs boson production process, pp-->H(+/-)h(A), can completely probe the LHS at the CERN Large Hadron Collider.

Supersymmetric QCD corrections to associated Higgs boson-bottom quark production

The associated production of a Higgs boson with a b quark is a discovery mode for a minimal supersymmetric standard model (MSSM) Higgs boson at large tan{beta}. We compute the SUSY QCD corrections from gluino and squark loops to this process and combine them with the O({alpha}{sub s}{sup 2}) next-to-leading order (NLO) QCD corrections to obtain reliable predictions for the rate. Finally, we compare our results with an effective Lagrangian approximation which includes only the low energy corrections from squark and gluino loops to the bb Higgs vertices.

Study of charged and neutral minimal supersymmetric standard model Higgs boson decays and measurement of tan β at the compact linear collider

The minimal supersymmetric extension of the standard model (MSSM) predicts the existence of new charged and neutral Higgs bosons. The pair creation of these new particles at the multi-TeV e + e − compact linear collider (CLIC), followed by decays into standard model particles, were simulated along with the corresponding background. High-energy beam-beam effects such as ISR, beamstrahlung and hadronic background were included. We have investigated the possibility of using the ratio between the number of events found in various decay channels to determine the MSSM parameter tan β and we have derived the corresponding statistical error from the uncertainties on the measured cross-sections and Higgs boson masses.

Charged and neutral minimal supersymmetric standard model Higgs boson decays and measurement of tan β at the compact linear collider

Charged and neutral minimal supersymmetric standard model Higgs boson decays and measurement of tan β at the compact linear collider

Determining supersymmetric parameters with dark matter experiments

In this paper, we explore the ability of direct and indirect dark matter experimentsto not only detect neutralino dark matter, but to constrain and measure theparameters of supersymmetry. In particular, we explore the relationship betweenthe phenomenological quantities relevant to dark matter experiments, suchas the neutralino annihilation and elastic scattering cross sections, and theunderlying characteristics of the supersymmetric model, such as the values ofμ (and the composition of the lightest neutralino),mA and tanβ. We explore a broad range of supersymmetric models and then focus on a smaller set of benchmarkmodels. We find that by combining astrophysical observations with collider measurements,μ could plausibly be constrained more tightly than it can be fromLarge Hadron Collider (LHC) data alone. In models in theA-funnel region of parameter space, we find that dark matter experiments could potentially determinemA toroughly ± 100 GeV, even when heavy neutral minimal supersymmetric standard model (MSSM) Higgs bosons(A,H1) cannot be observed at the LHC. The information provided by astrophysicalexperiments is often highly complementary to the information most easily ascertained atcolliders.

Implications of Direct Dark Matter Constraints for Minimal Supersymmetric Standard Model Higgs Boson Searches at the Tevatron

In regions of large tanbeta and small mAlpha, searches for heavy neutral minimal supersymmetric standard model (MSSM) Higgs bosons at the Tevatron are promising. At the same time, rates in direct dark matter experiments, such as CDMS, are enhanced in the case of large tanbeta and small mAlpha. As a result, there is a natural interplay between the heavy, neutral Higgs searches at the Tevatron and the region of parameter space explored by CDMS. We show that if the lightest neutralino makes up the dark matter of our universe, current limits from CDMS strongly constrain the prospects of heavy, neutral MSSM Higgs discovery at the Tevatron unless |mu| greater or approximately 400 GeV. The limits of CDMS projected for 2007 will increase this constraint to |mu| greater or approximately 800 GeV. If CDMS does observe neutralinos in the near future, however, it will make the discovery of Higgs bosons at the Tevatron far more likely.

SUSY Higgs boson flavor-changing neutral currents at the LHC

We compute and analyze the Flavor-Changing Neutral Current (FCNC) interactions of Minimal Supersymmetric Standard Model Higgs bosons (h = h0, H0, A0) with heavy quarks (top and bottom), focusing on the strongly-interacting sector. We correlate the Higgs bosons production cross-section at the LHC with the FCNC decay branching ratios and find the maximum allowed values of the production rates, sigma(pp -> h -> qq') = sigma(pp -> h) x B(h -> qq') (qq'= tc or bs) after taking into account limits from low energy data on flavor-changing interactions. We single out the top channel, with a maximum production rate of sigma^max(pp -> h -> tc) =~ 10^-3 - 10^-2 pb, as the most promising FCNC channel to be detected at the LHC.

Can there be a heavy sbottom hidden in three-jet data at CERN LEP?

A low-energy supersymmetry scenario with a light gluino of mass 12--16 GeV and light sbottom $({b}_{1})$ of mass 2--6 GeV has been used to explain the apparent overproduction of b quarks at the fermilab Tevatron. In this scenario the other mass eigenstate of the sbottom, i.e., ${b}_{2},$ is favored to be lighter than 180 GeV due to constraints from electroweak precision data. We survey its decay modes in this scenario and show that decay into a b quark and gluino should be dominant. Associated sbottom production at CERN LEP via ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{Z}^{*}\ensuremath{\rightarrow}{b}_{1}{b}_{2}^{*}+{b}_{1}^{*}{b}_{2}$ is studied and we show that it is naturally a three-jet process with a small cross section, increasingly obscured by a large standard model background for heavier ${b}_{2}.$ However we find that direct observation of a ${b}_{2}$ at the $5\ensuremath{\sigma}$ level is possible if it is lighter than 110--129 GeV, depending on the sbottom mixing angle $|\mathrm{cos}{\ensuremath{\theta}}_{b}|=0.30--0.45.$ We also show that ${b}_{2}$-pair production can be mistaken for production of neutral minimal supersymmetric standard model Higgs bosons in the channel ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{h}^{0}{A}^{0}\ensuremath{\rightarrow}b\overline{b}b\overline{b}.$ Using searches for the latter we place a lower mass limit of 90 GeV on ${b}_{2}.$

Higgs physics at LHC

The large hadron collider (LHC) and its detectors, ATLAS and CMS, are being built to study TeV scale physics, and to fully understand the electroweak symmetry breaking mechanism. The Monte-Carlo simulation results for the standard model and minimal super symmetric standard model Higgs boson searches and parameter measurements are discussed. Emphasis is placed on recent investigations of Higgs produced in association with top quarks and in vector boson fusion channels. These results indicate that Higgs sector can be explored in many channels within a couple of years of LHC operation, i.e.,L = 30 fb−1. Complete coverage including measurements of Higgs parameters can be carried out with full LHC program.

Self-interactions of the lightest minimal supersymmetric standard model Higgs boson in the large pseudoscalar-mass limit

We investigate the decoupling properties of the Higgs-sector-induced one-loop corrections in the lightest Higgs-boson self-couplings, in the framework of the Minimal Supersymmetric Standard Model (MSSM). The renormalized n-point vertex functions with external Higgs particles in the MSSM and in the SM are derived to the one-loop level and compared in the MA >> MZ limit. The computation has been done in a general R_{xi} gauge and the on-shell renormalization scheme is chosen. By a comparison of the renormalized lightest Higgs-boson h^0 vertex functions with respect to the corresponding SM ones, we find that the differences between the predictions of both models are summarized in the lightest Higgs-boson mass correction Delta Mh. Consequently, the radiative corrections are absorbed in the Higgs-boson mass, and the trilinear and quartic h^0 self-couplings acquire the same structure as the couplings of the SM Higgs-boson. Therefore, decoupling of the heavy MSSM Higgs bosons occurs and the MSSM h^0 self-interactions converge to the SM ones in the MA >> MZ limit.

Minimal supersymmetric standard model Higgs bosons in the intense-coupling regime

We perform a comprehensive study of the Higgs sector of the Minimal Supersymmetric extension of the Standard Model in the case where all Higgs bosons are rather light, with masses of ${\cal O}(100 GeV)$, and couple maximally to electroweak gauge bosons and strongly to standard third generation fermions, i.e. for large values of the ratio of the vacuum expectation values of the two Higgs doublet fields, $\tan \beta$. We first summarize the main phenomenological features of this "intense-coupling" scenario and discuss the available constraints from direct searches of Higgs bosons at LEP2 and the Tevatron as well as the indirect constraints from precision measurements such as the $\rho$ parameter, the $Zb\bar{b}$ vertex, the muon $(g-2)$ and the decay $b\to s \gamma$. We then analyze the decay branching fractions of the neutral Higgs particles in this regime and their production cross sections at the upcoming colliders, the Tevatron Run II, the LHC, a 500 GeV $e^+e^-$ linear collider (in the $e^+e^-$ and $\gamma \gamma$ options) as well as at a $\mu^+ \mu^-$ collider.

Distinguishing a minimal supersymmetric standard model Higgs boson from the SM Higgs boson at a linear collider

The decoupling properties of the Higgs sector in the minimal supersymmetric standard model (MSSM) imply that a light CP-even Higgs boson discovered at the Fermilab Tevatron or CERN LHC may closely resemble the standard model (SM) Higgs boson. In this paper, we investigate how precision measurements of Higgs properties at a linear collider (LC) can distinguish between a CP-even Higgs boson of the MSSM and the SM Higgs boson. We review the expected theoretical behavior of the partial widths and branching ratios for decays of the neutral MSSM Higgs bosons with significant couplings to the W and Z bosons, including the leading radiative corrections to the mixing angle \ensuremath{\alpha} and $\mathrm{tan}\ensuremath{\beta}$-enhanced vertex corrections. The general expectation is that the Higgs couplings to ${W}^{+}{W}^{\ensuremath{-}},$ ZZ, $c\overline{c},$ and $t\overline{t}$ should quickly approach their SM values for increasing CP-odd Higgs boson mass ${m}_{A},$ while the couplings to $b\overline{b}$ and ${\ensuremath{\tau}}^{+}{\ensuremath{\tau}}^{\ensuremath{-}}$ do so more slowly. Using the expected experimental and theoretical accuracy in determining SM branching ratios and partial widths, we demonstrate the sensitivity of measurements at the LC to variations in the MSSM parameters, with particular attention to the decoupling limit. For a wide range of MSSM parameters, the LC is sensitive to ${m}_{A}\ensuremath{\sim}600\mathrm{GeV}$ almost independently of $\mathrm{tan}\ensuremath{\beta}.$ For large values of $\mathrm{tan}\ensuremath{\beta}$ and some specific choices of MSSM parameters [e.g., ${A}_{t}\ensuremath{\mu}<0$ and $|{A}_{t}|\ensuremath{\simeq}|\ensuremath{\mu}|\ensuremath{\simeq}\mathcal{O}{(M}_{S})$], one of the CP-even Higgs bosons can be SM-like independent of the value of ${m}_{A}.$ In the case of large deviations from the SM, we present a procedure using Higgs coupling measurements to extract the supersymmetric correction to the relation between the b quark mass and Yukawa coupling.

Detection of charged minimal supersymmetric standard model Higgs bosons at the NLC

Detection of charged minimal supersymmetric standard model Higgs bosons at the NLC

Search for invisible Higgs boson decays in e +e − collisions at centre-of-mass energies up to 184 GeV

In a data sample of 78.3 pb −1 collected in 1996 and 1997 by the ALEPH detector at centre-of-mass energies from 161 to 184 GeV, invisible decays of a Higgs boson have been searched for in the reaction e +e −→hZ, where the Z can decay into e +e −, μ + μ − or q q ̄ . No evidence for a signal is found and limits on the production cross section are derived as a function of the Higgs boson mass. These results are combined with those obtained in an update of the analyses of the ALEPH data taken at LEP 1. For a production cross section equal to that of the minimal standard model Higgs boson, masses below 80 GeV/ c 2 are excluded at 95% C.L.

Non-minimal neutral Higgs bosons at LEP2

We study the phenomenology of the neutral Higgs sector of a non-SUSY non-minimal Standard Model. Models with more than one Higgs doublet are possible, and may contain neutral Higgs scalars with branching ratios significantly different to those of the Minimal Standard Model Higgs boson. We show how these differences may be exploited at LEP2 in order to distinguish the non-minimal Standard Model from the minimal version.

Search for the minimal standard model Higgs boson

A search for the Minimal Standard Model Higgs boson (H 0) has been performed with data from e +e − collisions collected by the OPAL detector at LEP. The search was made for events of the types e + e −→( e + e −,μ +μ − or ν ν) H 0, H 0→ q q ̄ and was based on approximately 78 pb −1 of data taken at center-of-mass energies between 88 and 95 GeV in the years 1990–1993. The present study, combined with previous OPAL publications, excludes the existence of a Minimal Standard Model Higgs boson with mass below 56.9 GeV at the 95% confidence level.