Higgs Boson Production Cross Section Research Articles

Reconstruction of Higgs bosons in the di-tau channel via 3-prong decay

Abstract We propose a method for reconstructing the mass of a particle, such as the Higgs boson, decaying into a pair of τ leptons, of which one subsequently undergoes a 3-prong decay. The kinematics is solved using information from the visible decay products, the missing transverse momentum, and the 3-prong τ decay vertex, with the detector resolution taken into account using a likelihood method. The method is shown to give good discrimination between a 125 GeV Higgs boson signal and the dominant backgrounds, such as Z 0 decays to ττ and W ± plus jets production. As a result, we find an improvement, compared to existing methods for this channel, in the discovery potential, as well as in measurements of the Higgs boson mass and production cross section times branching ratio.

Prospects for the measurement of the Higgs Yukawa couplings to b and c quarks, and muons at CLIC

AbstractThe investigation of the properties of the Higgs boson, especially a test of the predicted linear dependence of the branching ratios on the mass of the final state is going to be an integral part of the physics program at colliders at the energy frontier for the foreseeable future. The large Higgs boson production cross section at a 3 TeV CLIC machine allows for a precision measurement of the Higgs branching ratios. The cross section times branching ratio of the decays $\mathrm {H}\to \mathrm {b}\overline {\mathrm {b}}$, $\mathrm {H}\to \mathrm {c}\overline {\mathrm {c}}$ and H→μ+μ− of a Standard Model Higgs boson with a mass of 120 GeV can be measured with a statistical uncertainty of 0.23 %, 3.1 % and 15 %, respectively, assuming an integrated luminosity of 2 ab−1.

Search for a SM Higgs boson in dilepton plus missing transverse energy final state with the DØ detector at ${\sqrt s}{=}{1.96}$ TeV

A search is presented for the Standard Model (SM) Higgs boson optimized in the decay channel H→W + W −, where both W bosons decay leptonically. The final state considered contains dileptons and missing transverse energy from the neutrinos. A multivariate analysis is used to suppress the background. No significant excess above the SM background has been observed and limits set on the Higgs boson production cross-section ∗ the branching ratio for mH = 115–200 GeV are computed. Results using 8.1 fb−1 of data are presented.

Search for the Higgs boson in the [formula omitted] decay channel at [formula omitted] with the ATLAS detector

A search for the Standard Model Higgs boson has been performed in the H→WW→ℓνjj channel using 4.7 fb−1 of pp collision data recorded at a centre-of-mass energy of s=7 TeV with the ATLAS detector at the Large Hadron Collider. Higgs boson candidates produced in association with zero, one or two jets are included in the analysis to maximize the acceptance for both gluon fusion and weak boson fusion Higgs boson production processes. No significant excess of events is observed over the expected background and limits on the Higgs boson production cross section are derived for a Higgs boson mass in the range 300 GeV<mH<600 GeV. The best sensitivity is reached for mH=400 GeV, where the observed (expected) 95% confidence level upper bound on the cross section for H→WW produced in association with zero or one jet is 2.2 pb (1.9 pb), corresponding to 1.9 (1.6) times the Standard Model prediction. In the Higgs boson plus two jets channel, which is more sensitive to the weak boson fusion process, the observed (expected) 95% confidence level upper bound on the cross section for H→WW production with mH=400 GeV is 0.7 pb (0.6 pb), corresponding to 7.9 (6.5) times the Standard Model prediction.

Search for Standard Model Higgs boson in the decay channel ${\bf \textit{H}}\rightarrow {\bf \textit{ZZ}}\rightarrow {\bf \textit{l}}^{{\bf +}}{\bf \textit{l}}^{{\bf -}} q\boldsymbol{\bar{q}}$ at CMS

A search for the Standard Model Higgs boson decaying to two Z bosons with a subsequent decay to a final state with two leptons and two quark jets, \(H\rightarrow ZZ\rightarrow l^{+}l^{-} q\bar{q}\), is presented. Data corresponding to an integrated luminosity of 1.6 fb − 1 of LHC proton–proton collisions at the centre-of-mass energy of 7 TeV were collected and analysed by the CMS experiment. The selection to discriminate between signal and background events is based on kinematic and topological quantities, which include the angular spin correlations of the decay products. The events are classified according to the probability of the jets to originate from quarks of light or heavy flavour or from gluons. No evidence for a Higgs boson is found and upper limits on the Higgs boson production cross-section are set in the range of masses between 226 and 600 GeV/c2.

Search for the Higgs boson in the H→WW→ℓνjj decay channel in pp collisions at ${\sqrt{{s}}}$ = 7 TeV with the ATLAS detector

A search for a Higgs boson has been performed in the H→WW→lνjj channel using 1.04 fb − 1 of pp collision data at $\sqrt{s} = 7~{\rm TeV}$ recorded with the ATLAS detector at the Large Hadron Collider. No significant excess of events is observed over the expected Standard Model (SM) background and limits on the Higgs boson production cross-section are derived for a Higgs boson mass in the range 240 GeV < m H < 600 GeV. The best sensitivity is obtained for m H = 400 GeV, where the 95% confidence level upper bound on the cross-section for H→WW production is 3.1 pb, or 2.7 times the Standard Model prediction.

Search for the Standard Model Higgs Boson in AssociatedWHProduction in9.7 fb−1ofpp¯Collisions with the D0 Detector

We present a search for the standard model Higgs boson in final states with a charged lepton (electron or muon), missing transverse energy, and two or three jets, at least one of which is identified as a $b$-quark jet. The search is primarily sensitive to $WH\to\ell\nu b\bar{b}$ production and uses data corresponding to 9.7 fb$^{-1}$ of integrated luminosity collected with the D0 detector at the Fermilab Tevatron $p\bar{p}$ Collider at $\sqrt{s}=1.96$ TeV. We observe agreement between data and the expected background. For a Higgs boson mass of 125 GeV, we set a 95% C.L. upper limit on the production of a standard model Higgs boson of 5.2$\times\sigma_{\rm SM}$, where $\sigma_{\rm SM}$ is the standard model Higgs boson production cross section, while the expected limit is 4.7$\times\sigma_{\rm SM}$.

Search for a standard model Higgs boson in the [formula omitted] decay channel using [formula omitted] of [formula omitted] data with the ATLAS detector

A search for a Standard Model Higgs boson decaying via H→ZZ→ℓ+ℓ−νν¯, where ℓ represents electrons or muons, is presented. It is based on proton–proton collision data at s=7 TeV, collected by the ATLAS experiment at the LHC during 2011 and corresponding to an integrated luminosity of 4.7 fb−1. The data agree with the expected Standard Model backgrounds. Upper limits on the Higgs boson production cross section are derived for Higgs boson masses between 200 GeV and 600 GeV and the production of a Standard Model Higgs boson with a mass in the range 319–558 GeV is excluded at the 95% confidence level.

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.

Search for the Standard Model Higgs boson in the [formula omitted] decay mode with [formula omitted] of ATLAS data at [formula omitted

A search for the Standard Model Higgs boson in the H→WW(⋆)→ℓνℓν (ℓ=e,μ) decay mode is presented. The search is performed using proton–proton collision data corresponding to an integrated luminosity of 4.7 fb−1 at a centre-of-mass energy of 7 TeV collected during 2011 with the ATLAS detector at the Large Hadron Collider. No significant excess of events over the expected background is observed. An upper bound is placed on the Higgs boson production cross section as a function of its mass. A Standard Model Higgs boson with mass in the range between 133 GeV and 261 GeV is excluded at 95% confidence level, while the expected exclusion range is from 127 GeV to 233 GeV.

Higgs production in a warped extra dimension

Abstract Measurements of the Higgs-boson production cross section at the LHC are an important tool for studying electroweak symmetry breaking at the quantum level, since the main production mechanism gg → h is loop-suppressed in the Standard Model (SM). Higgs production in extra-dimensional extensions of the SM is sensitive to the Kaluza-Klein (KK) excitations of the quarks, which can be exchanged as virtual particles in the loop. In the context of the minimal Randall-Sundrum (RS) model with bulk fields and a brane-localized Higgs sector, we derive closed analytical expressions for the gluon-gluon fusion process, finding that the effect of the infinite tower of virtual KK states can be described in terms of a simple function of the fundamental (5D) Yukawa matrices. Given a specific RS model, this will allow one to easily constrain the parameter space, once a Higgs signal has been established. We explain that discrepancies between existing calculations of Higgs production in RS models are related to the non-commutativity of two limits: taking the number of KK states to infinity and removing the regulator on the Higgs-boson profile, which is required in an intermediate step to make the relevant overlap integrals well defined. Even though the one-loop gg → h amplitude is finite in RS scenarios with a brane-localized Higgs sector, it is important to introduce a consistent ultraviolet regulator in order to obtain the correct result.

The Higgs-boson lineshape

The heavy Higgs searches at LHC are carried out in gg→H→WW→lνlν, gg→H→ZZ→llll,llνν,llqq channels. The current searches for a heavy Higgs boson assume on-shell (stable) Higgs-boson production. The Higgs-boson production cross-section is then sampled with a Breit–Wigner distribution (with fixed-width or running-width) and implemented in Monte Carlo simulations. Therefore the question remains of what is the limitation of the narrow Higgs-width approximation. The main focus of this work is on the description of the Standard Model Higgs-boson lineshape in the heavy Higgs region, typically MH above 600 GeV. The framework discussed in this paper is general enough and can be used for all processes and for all kinematical regions. Numerical results are shown for the gluon-fusion process. Issues of gauge invariance and residual theoretical uncertainties are also discussed. Limitations due to a breakdown of the perturbative expansion are comprehensively discussed, including a discussion of the equivalence theorem for (off-shell) virtual vector-bosons. Analytic continuation in a theory with unstable particles is thoroughly discussed.

Factorization and NNLL Resummation for Higgs production with a jet veto

Using methods of effective field theory, we derive the first all-order factorization theorem for the Higgs-boson production cross section with a jet veto, imposed by means of a standard sequential recombination jet algorithm. Like in the case of small-q_T resummation in Drell-Yan and Higgs production, the factorization is affected by a collinear anomaly. Our analysis provides the basis for a systematic resummation of large logarithms log(m_H/p_T^veto) beyond leading-logarithmic order. Specifically, we present predictions for the resummed jet-veto cross section and efficiency at next-to-next-to-leading logarithmic order. Our results have important implications for Higgs-boson searches at the LHC, where a jet veto is required to suppress background events.

Search for charged Higgs bosons in e+e- collisions at [Formula: see text

A search is made for charged Higgs bosons predicted by Two-Higgs-Doublet extensions of the Standard Model (2HDM) using electron-positron collision data collected by the OPAL experiment at sqrt{s}=189mbox{--}209 mbox{GeV}, corresponding to an integrated luminosity of approximately 600 pb−1. Charged Higgs bosons are assumed to be pair-produced and to decay into mathrm{q} bar{mathrm{q}}, τντ or AW±. No signal is observed. Model-independent limits on the charged Higgs-boson production cross section are derived by combining these results with previous searches at lower energies. Under the assumption mathrm{BR} (mathrm{H}^{pm} to taunu_{tau}) + mathrm{BR} (mathrm{H}^{pm} to mathrm{q} bar{mathrm{q}}) = 1, motivated by general 2HDM type II models, excluded areas on the [m_{mathrm{H}^{pm}} , mathrm{BR} (mathrm {H}^{pm} to taunu_{tau})] plane are presented and charged Higgs bosons are excluded up to a mass of 76.3 GeV at 95 % confidence level, independent of the branching ratio BR(H±→τντ). A scan of the 2HDM type I model parameter space is performed and limits on the Higgs-boson masses m_{mathrm{H}^{pm}} and mA are presented for different choices of tanβ.

Search for neutral Higgs bosons decaying to tau pairs in pp collisions at [formula omitted

A search for neutral Higgs bosons decaying to tau pairs at a center-of-mass energy of 7 TeV is performed using a dataset corresponding to an integrated luminosity of 4.6 fb−1 recorded by the CMS experiment at the LHC. The search is sensitive to both the standard model Higgs boson and to the neutral Higgs bosons predicted by the minimal supersymmetric extension of the standard model (MSSM). No excess of events is observed in the tau-pair invariant-mass spectrum. For a standard model Higgs boson in the mass range of 110–145 GeV upper limits at 95% confidence level (CL) on the production cross section are determined. We exclude a Higgs boson with mH=115 GeV with a production cross section 3.2 times of that predicted by the standard model. In the MSSM, upper limits on the neutral Higgs boson production cross section times branching fraction to tau pairs, as a function of the pseudoscalar Higgs boson mass, mA, sets stringent new bounds in the parameter space, excluding at 95% CL values of tanβ as low as 7.1 at mA=160 GeV in the mhmax benchmark scenario.

Higgs production and decay with a fourth Standard-Model-like fermion generation

State-of-the-art predictions for the Higgs-boson production cross section via gluon fusion and for all relevant Higgs-boson decay channels are presented in the presence of a fourth Standard-Model-like fermion generation. The qualitative features of the most important differences to the genuine Standard Model are pointed out, and the use of the available tools for the predictions is described. For a generic mass scale of 400−600 GeV in the fourth generation explicit numerical results for the cross section and decay widths are presented, revealing extremely large electroweak radiative corrections, e.g., to the cross section and the Higgs decay into WW or ZZ pairs, where they amount to about −50 % or more. This signals the onset of a non-perturbative regime due to the large Yukawa couplings in the fourth generation. An estimate of the respective large theoretical uncertainties is presented as well.

Search for the Higgs Boson in theH→WW(*)→l+νl−ν¯Decay Channel inppCollisions ats=7 TeVwith the ATLAS Detector

A search for the Higgs boson has been performed in the H->WW->lvlv channel (l=e/mu) with an integrated luminosity of 2.05/fb of pp collisions at sqrt(s) = 7 TeV collected with the ATLAS detector at the Large Hadron Collider. No significant excess of events over the expected background is observed and limits on the Higgs boson production cross section are derived for a Higgs boson mass in the range 110<mH<300 GeV. The observations exclude the presence of a Standard Model Higgs boson with a mass 145<mH<206 GeV at 95% confidence level.

Quantitative constraints on the gluon distribution function in the proton from collider isolated-photon data

The impact of isolated-photon data from proton–(anti)proton collisions at RHIC, Spp¯S, Tevatron and LHC energies, on the parton distribution functions of the proton is studied using a recently developed Bayesian reweighting method. The impact on the gluon density of the 35 existing isolated-γ measurements is quantified using next-to-leading order (NLO) perturbative QCD calculations complemented with the NNPDF2.1 parton densities. The NLO predictions are found to describe well most of the datasets from 200 GeV up to 7 TeV centre-of-mass energies. The isolated-photon spectra recently measured at the LHC are precise enough to constrain the gluon distribution and lead to a moderate reduction (up to 20%) of its uncertainties around fractional momenta x≈0.02. As a particular case, we show that the improved gluon density reduces the PDF uncertainty for the Higgs boson production cross section in the gluon-fusion channel by more than 20% at the LHC. We conclude that present and future isolated-photon measurements constitute an interesting addition to coming global PDF analyses.

Search for the standard model Higgs boson in the H → ZZ → 2ℓ2ν channel in pp collisions at $ \sqrt {\text{s}} = {7}\;{\text{TeV}} $

Abstract A search for the standard model Higgs boson in the H → ZZ → 2ℓ2ν decay channel, where ℓ = e or μ, in pp collisions at a center-of-mass energy of 7 TeV is presented. The data were collected at the LHC, with the CMS detector, and correspond to an integrated luminosity of 4.6 fb−1. No significant excess is observed above the background expectation, and upper limits are set on the Higgs boson production cross section. The presence of the standard model Higgs boson with a mass in the 270-440 GeV range is excluded at 95% confidence level.

Search for the standard model Higgs boson in the H → ZZ → ℓ+ℓ−τ+τ− decay channel in pp collisions at $ \sqrt {s} = {7}\;{\text{TeV}} $

Abstract A search is reported for the standard model Higgs boson in the H → ZZ → ℓ+ℓ−τ +τ − decay mode, where ℓ = μ or e, in proton-proton collisions at $ \sqrt {s} = {7}\;{\text{TeV}} $ , corresponding to an integrated luminosity of 4.7 fb−1 collected with the CMS detector at the LHC. No evidence is found for a significant deviation from the background expectation. An upper limit four to twelve times larger than the predicted value is set at 95% confidence level for the product of the standard model Higgs boson production cross section and decay branching fraction in the mass range 190 &lt; m H &lt; 600 GeV.