Boson Mass Range Research Articles

Search for neutral Higgs bosons in events with multiple bottom quarks at the Tevatron

The combination of searches performed by the CDF and D0 collaborations at the Fermilab Tevatron Collider for neutral Higgs bosons produced in association with b quarks is reported. The data, corresponding to 2.6 fb-1 of integrated luminosity at CDF and 5.2 fb-1 at D0, have been collected in final states containing three or more b jets. Upper limits are set on the cross section multiplied by the branching ratio varying between 44 pb and 0.7 pb in the Higgs boson mass range 90 to 300 GeV, assuming production of a narrow scalar boson. Significant enhancements to the production of Higgs bosons can be found in theories beyond the standard model, for example in supersymmetry. The results are interpreted as upper limits in the parameter space of the minimal supersymmetric standard model in a benchmark scenario favoring this decay mode.

Search for the Standard Model Higgs boson in the H → τ + τ − decay mode in $ \sqrt {s} = 7\,{\mathrm{TeV}} $ pp collisions with ATLAS

Abstract A search for the Standard Model Higgs boson decaying into a pair of τ leptons is reported. The analysis is based on a data sample of proton-proton collisions collected by the ATLAS experiment at the LHC and corresponding to an integrated luminosity of 4.7 fb−1. No significant excess over the expected background is observed in the Higgs boson mass range of 100–150 GeV. The observed (expected) upper limits on the cross section times the branching ratio for H → τ + τ − are found to be between 2.9 (3.4) and 11.7 (8.2) times the Standard Model prediction for this mass range.

Search for a fermiophobic Higgs boson in pp collisions at $ \sqrt {s} = 7 $ TeV

AbstractCombined results are reported from searches for a fermiophobic Higgs boson in the γγ, WW, and ZZ decay modes in proton-proton collisions at$ \sqrt {s} = 7 $TeV. The explored Higgs boson mass range is 110–300 GeV. The data sample corresponds to an integrated luminosity of 4.9–5.1 fb−1. A fermiophobic Higgs boson is excluded at 95% confidence level in the mass range 110–194 GeV, and at 99% confidence level in the mass ranges 110–124.5 GeV, 127–147.5 GeV, and 155–180 GeV.

Search for the standard model Higgs boson produced in association with aW±boson with7.5 fb−1integrated luminosity at CDF

We present a search for the standard model Higgs boson produced in association with a $W^{\pm}$ boson. This search uses data corresponding to an integrated luminosity of 7.5 fb$^{-1}$ collected by the CDF detector at the Tevatron. We select $WH \to \ell\nu b \bar{b}$ candidate events with two jets, large missing transverse energy, and exactly one charged lepton. We further require that at least one jet be identified to originate from a bottom quark. Discrimination between the signal and the large background is achieved through the use of a Bayesian artificial neural network. The number of tagged events and their distributions are consistent with the standard model expectations. We observe no evidence for a Higgs boson signal and set 95% C.L. upper limits on the $WH$ production cross section times the branching ratio to decay to $b\bar b$ pairs, $\sigma(p\bar p \rightarrow W^{\pm} H) \times {\cal B}(H\rightarrow b\bar b)$, relative to the rate predicted by the standard model. For the Higgs boson mass range of 100 GeV/c$^2$ to 150 GeV/c$^2$ we set observed (expected) upper limits from 1.34 (1.83) to 38.8 (23.4). For 115 GeV/c$^2$ the upper limit is 3.64 (2.78). The combination of the present search with an independent analysis that selects events with three jets yields more stringent limits ranging from 1.12 (1.79) to 34.4 (21.6) in the same mass range. For 115 GeV/c$^2$ the upper limit is 2.65 (2.60).

Search for Higgs boson production in oppositely charged dilepton and missing energy events inpp¯collisions ats=1.96 TeV

We present a search for the standard model Higgs boson using events with two oppositely charged leptons and large missing transverse energy as expected in $H\rightarrow WW$ decays. The events are selected from data corresponding to 8.6 \ifb\ of integrated luminosity in $p \bar{p}$ collisions at $\sqrt{s}=1.96$ TeV collected with the D0 detector at the Fermilab Tevatron Collider. No significant excess above the standard model background expectation in the Higgs boson mass range this search is sensitive to is observed, and upper limits on the Higgs boson production cross section are derived.

Combined search for the Standard Model Higgs boson inppcollisions ats=7 TeVwith the ATLAS detector

A combined search for the Standard Model Higgs boson with the ATLAS detector at the LHC is presented. The datasets used correspond to integrated luminosities from 4.6 fb^-1 to 4.9 fb^-1 of proton-proton collisions collected at sqrt(s) = 7 TeV in 2011. The Higgs boson mass ranges of 111.4 GeV to 116.6 GeV, 119.4 GeV to 122.1 GeV, and 129.2 GeV to 541 GeV are excluded at the 95% confidence level, while the range 120 GeV to 560 GeV is expected to be excluded in the absence of a signal. An excess of events is observed at Higgs boson mass hypotheses around 126 GeV with a local significance of 2.9 standard deviations (sigma). The global probability for the background to produce an excess at least as significant anywhere in the entire explored Higgs boson mass range of 110-600 GeV is estimated to be ~15%, corresponding to a significance of approximately one sigma.

Search for standard model Higgs boson production in association with aW boson using a matrix element technique at CDF inpp¯collisions ats=1.96 TeV

This paper presents a search for standard model Higgs boson production in association with a $W$ boson using events recorded by the CDF experiment in a dataset corresponding to an integrated luminosity of 5.6 fb-1. The search is performed using a matrix element technique in which the signal and background hypotheses are used to create a powerful discriminator. The discriminant output distributions for signal and background are fit to the observed events using a binned likelihood approach to search for the Higgs boson signal. We find no evidence for a Higgs boson, and 95% confidence level (C.L.) upper limits are set on the Higgs boson production rate. The observed limits range from 3.5 to 37.6 relative to the standard model expectation for Higgs boson masses between 100 and 150 GeV. The 95% C.L. expected limit is estimated from the median of an ensemble of simulated experiments and varies between 2.9 and 32.7 relative to the production rate predicted by the standard model over the Higgs boson mass range studied.

Combined results of searches for the standard model Higgs boson in pp collisions at [formula omitted

Combined results are reported from searches for the standard model Higgs boson in proton–proton collisions at s=7 TeV in five Higgs boson decay modes: γγ, bb, ττ, WW, and ZZ. The explored Higgs boson mass range is 110–600 GeV. The analysed data correspond to an integrated luminosity of 4.6–4.8 fb−1. The expected excluded mass range in the absence of the standard model Higgs boson is 118–543 GeV at 95% CL. The observed results exclude the standard model Higgs boson in the mass range 127–600 GeV at 95% CL, and in the mass range 129–525 GeV at 99% CL. An excess of events above the expected standard model background is observed at the low end of the explored mass range making the observed limits weaker than expected in the absence of a signal. The largest excess, with a local significance of 3.1σ, is observed for a Higgs boson mass hypothesis of 124 GeV. The global significance of observing an excess with a local significance ⩾3.1σ anywhere in the search range 110–600 (110–145) GeV is estimated to be 1.5σ(2.1σ). More data are required to ascertain the origin of the observed excess.

Combined search for the Standard Model Higgs boson using up to 4.9 fb−1 of pp collision data at [formula omitted] with the ATLAS detector at the LHC

A combined search for the Standard Model Higgs boson with the ATLAS experiment at the LHC using datasets corresponding to integrated luminosities from 1.04 fb−1 to 4.9 fb−1 of pp collisions collected at s=7 TeV is presented. The Higgs boson mass ranges 112.9–115.5 GeV, 131–238 GeV and 251–466 GeV are excluded at the 95% confidence level (CL), while the range 124–519 GeV is expected to be excluded in the absence of a signal. An excess of events is observed around mH∼126 GeV with a local significance of 3.5 standard deviations (σ). The local significances of H→γγ, H→ZZ(⁎)→ℓ+ℓ−ℓ′+ℓ′− and H→WW(⁎)→ℓ+νℓ′−ν¯, the three most sensitive channels in this mass range, are 2.8σ, 2.1σ and 1.4σ, respectively. The global probability for the background to produce such a fluctuation anywhere in the explored Higgs boson mass range 110–600 GeV is estimated to be ∼1.4% or, equivalently, 2.2σ.

Search for Neutral Minimal Supersymmetric Standard Model Higgs Bosons Decaying to Tau Pairs Produced in Association withbQuarks inpp¯Collisions ats=1.96 TeV

We report results from a search for neutral Higgs bosons produced in association with b quarks using data recorded by the D0 experiment at the Fermilab Tevatron Collider and corresponding to an integrated luminosity of 7.3 fb(-1). This production mode can be enhanced in several extensions of the standard model (SM) such as in its minimal supersymmetric extension (MSSM) at high tanβ. We search for Higgs bosons decaying to tau pairs with one tau decaying to a muon and neutrinos and the other to hadrons. The data are found to be consistent with SM expectations, and we set upper limits on the cross section times branching ratio in the Higgs boson mass range from 90 to 320 GeV/c(2). We interpret our result in the MSSM parameter space, excluding tanβ values down to 25 for Higgs boson masses below 170 GeV/c(2).

Search for neutral Higgs bosons in the multi-b-jet topology in [formula omitted] of [formula omitted] collisions at [formula omitted

Data recorded by the D0 experiment at the Fermilab Tevatron Collider are analyzed to search for neutral Higgs bosons produced in association with b quarks. The search is performed in the three-b-quark channel using multijet-triggered events corresponding to an integrated luminosity of 5.2 fb−1. In the absence of any significant excess above background, limits are set on the cross section multiplied by the branching ratio in the Higgs boson mass range 90 to 300 GeV, extending the excluded regions in the parameter space of the minimal supersymmetric standard model.

CMS detector sensitivity to the Standard Model Higgs boson in H → ZZ (∗) → 4leptons decay channel

The search for the Higgs boson is one of the most important tasks of the CMS experiment at pp LHC collider. The most recent results on the Standard Model Higgs boson discovery potential are presented, obtained using the most recent full simulation and reconstruction software as well as with detailed treatment of systematic uncertainties. Results show that the whole Standard Model Higgs boson mass range will be covered with about ∼ 10 f b −1 .

Comparison of Higgs boson mass and width determination of the LHC and a linear collider

Two important properties of a Higgs boson are its mass and width. They may distinguish the Standard Model (SM) Higgs boson from Higgs bosons of extended models. We show results from a direct mass and width reconstruction for a Higgs boson mass range from 120 to 340 GeV/c2. The mass and width have been reconstructed from the H → ZZ* → µ+µ−µ+µ− reaction in an LHC simulation of the CMS detector. The determined mass accuracy has been compared with that obtained from studies for a linear collider (LC). The mass precision from the latter studies are derived by scaling previous LC simulation results according to the expected event rates. For the Higgs boson width we compare a direct determination with indirect methods and find good complementarity.

Radiative corrections toZbb¯production

We report on QCD radiative corrections to the process $p\overline{p}\ensuremath{\rightarrow}\mathrm{Zb}\overline{b}$ in the approximation in which the b quark is considered massless. The implementation of this process in the general purpose Monte Carlo program MCFM is discussed in some detail. These results are used to investigate backgrounds to Higgs boson production in the $\mathrm{ZH}$ channel. We investigate the Higgs boson mass range $(100 \mathrm{GeV}l{m}_{H}l130 \mathrm{GeV})$ for the Fermilab Tevatron running at $\sqrt{s}=2 \mathrm{TeV}.$

Higgs boson discovery potential of LHC in the channel pp→γγ+jet

We discuss the SM Higgs discovery potential of LHC in the reaction $pp\to H+ jet\to\gamma\gamma+jet$ when the jet is observed at sufficiently high $E_t$ to be reliably identified. We conclude that this channel gives promising discovery possibilities for the Higgs boson mass range 100-140 GeV, during LHC operation at a low luminosity. With 30 fb$^{-1}$ of accumulated data and for $M_H=120$ GeV about 100 signal events could be observed with the number of background events larger by a factor of 2 only, showing a signal significance $S/\sqrt{B}\sim 7$. We use the difference of distributions in the partonic subprocess energy $\sqrt{\hat s}$ for the signal and background for a better separation of the signal.

Sphaleron effects near the critical temperature.

We discuss one-loop radiative corrections to the sphaleron-induced baryon-number-violating transition rate near the electroweak phase transition in the standard model. We emphasize that in the case of a first-order transition a rearrangement of the loop expansion is required close to the transition temperature. The corresponding expansion parameter, the effective three-dimensional gauge coupling, approaches a finite \ensuremath{\lambda}-dependent value at the critical temperature. The \ensuremath{\lambda} (Higgs boson mass) dependence of the one-loop radiative corrections is discussed in the framework of the heat kernel method. Radiative corrections are small compared to the leading sphaleron contribution as long as the Higgs boson mass is small compared to the W mass. To one-loop accuracy, there is no Higgs boson mass range compatible with experimental limits where washing out of a B+L asymmetry could be avoided for the minimal standard model with one Higgs doublet.

ρ PARAMETER IN THE VECTOR CONDENSATE MODEL OF ELECTROWEAK INTERACTIONS

In the standard model of electroweak interactions the Higgs doublet is replaced by a doublet of vector bosons and the gauge symmetry is broken dynamically. This generates masses for the gauge bosons and fermions as well as it fixes the interactions in the model. The model has a low momentum scale. In this note we show that the model survives the test of the ρ parameter, and to each momentum scale ρ chooses a possible range of vector boson masses.

Updated analysis of high precision LEP data

The precision electroweak data presented by the LEP Collaborations at La Thuile and Moriond Conferences in March 1993 are analyzed in a multiparameter framework that allows inclusion of a large category of extensions of the minimal SU(2) L×U(1) Standard Model. The main conclusion are: 1. (i) The data agree well with the Minimal Standard Model (MSM); 2. (ii) The best fit to the top quark and Higgs boson masses in the MSM is M t =143± 18 19 GeV, M H =73± 13 178 GeV. The positive error on M H is gaussian in log ( M H ). The data favor somewhat the lighter Higgs boson mass range but still agrees with M H =1000 GeV within less than two standard deviations. 3. (iii) The new results on Γ b / Γ had now play a fundamental role in deriving a Δϱ and M H -independent top quark mass limit from the Z→b b vertex correction. So far this limit was mostly obtained from R had and was intimately dependent on the value chosen for the strong coupling constant. With all data we find, for α s ( M Z 2)=0.117 ± 0.005, M t <185 GeV at 95% CL, Δϱ and M H independent. As a consequence of this new precision on Γ b / Γ had, it is possible to derive from electroweak measuremnts a value of α s ( M Z 2), even with all the electroweak parameters left free outside the MSM range: α s ( M Z 2)=0.111±0.015.