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At least 919 records · Page 51
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DOE OSTI2010

Combined upper limit on standard model higgs boson production at D0 in $p \bar{p}$ collisions at $\sqrt{s} = 1.96-TeV

The latest searches for the Standard Model Higgs boson at a centre-of-mass energy of {radical}s = 1.96 TeV with the D0 and the CDF detectors at the Fermilab Tevatron collider are presented. For the first time since the LEP experiments the sensitivity for a Standard Model Higgs boson has been reached at a Higgs boson mass of 170 GeV/c{sup 2}.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Search for a low mass Standard Model Higgs boson in the $\tau-\tau$ decay channel in $p\bar{p}$ collisions at $\sqrt{s}$ = 1.96 TeV

We report on a search for the standard model Higgs boson decaying into pairs of {tau} leptons in p{bar p} collisions produced by the Tevatron at {radical}s = 1.96 TeV. The analyzed data sample was recorded by the CDFII detector and corresponds to an integrated luminosity of 6.0 fb{sup -1}. The search is performed in the final state with one {tau} decaying leptonically and the second one identified through its semi-hadronic decay. Since no significant excess is observed, a 95% credibility level upper limit on the production cross section times branching ratio to the {tau}{tau} final state is set for hypothetical Higgs boson masses between 100 and 150 GeV/c{sup 2}. For a Higgs boson of 120 GeV/c{sup 2} the observed (expected) limit is 14.6 (15.3) the predicted value.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

Search for a Low-Mass Higgs Boson (A0) at BaBar

The BABAR Collaboration has performed three searches for a light Higgs boson, A{sup 0}, in radiative Upsilon ({Upsilon}) decays: {Upsilon}(3S) {yields} {gamma}A{sup 0}, A{sup 0} {yields} {tau}{sup +}{tau}{sup -}; {Upsilon}(nS) {yields} {gamma}A{sup 0}, A{sup 0} {yields} {mu}{sup +}{mu}{sup -} (n = 2,3); and {Upsilon}(3S) {yields} {gamma}A{sup 0}, A{sup 0} {yields} invisible. Such a Higgs boson (A{sup 0}) appears in the Next-to-Minimal Supersymmetric extensions of the Standard Model, where a light CP-odd Higgs boson couples strongly to b-quarks. The searches are based on data samples that consist of 122 x 10{sup 6} {Upsilon}(3S) and 99 x 10{sup 6} {Upsilon}(2S) decays, collected by the BABAR detector at the SLAC National Accelerator Laboratory. The searches reveal no evidence for an A{sup 0}, and product of branching fractions upper limits, at 90% C.L., of (1.5-16) x 10{sup -5}, (0.44-44) x 10{sup -6}, and (0.7-31) x 10{sup -6} were obtained for these searches, respectively. Also, we set the upper limits {Beta}({eta}{sub b} {yields} {tau}{sup +}{tau}{sup -}) < 8% and {Beta}({eta}{sub b} {yields} {mu}{sup +}{mu}{sup -}) < 0.9%.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

Search for the Standard Model Higgs boson in the decay channel H -> ZZ((*)) -> 4l with 4.8 fb(-1) of pp collision data at root s=7 TeV with ATLAS

This Letter presents a search for the Standard Model Higgs boson in the decay channel H {yields} ZZ{sup (*)} {yields} {ell}{sup +}{ell}{sup -}{ell}{prime}{sup +}{ell}{prime}{sup -}, where {ell}, {ell}{prime} = e or {mu}, using proton-proton collisions at {radical}s = 7 TeV recorded with the ATLAS detector and corresponding to an integrated luminosity of 4.8 fb{sup -1}. The four-lepton invariant mass distribution is compared with Standard Model background expectations to derive upper limits on the cross section of a Standard Model Higgs boson with a mass between 110 GeV and 600 GeV. The mass ranges 134-156 GeV, 182-233 GeV, 256-265 GeV and 268-415 GeV are excluded at the 95% confidence level. The largest upward deviations from the background-only hypothesis are observed for Higgs boson masses of 125 GeV, 244 GeV and 500 GeV with local significances of 2.1, 2.2 and 2.1 standard deviations, respectively. Once the look-elsewhere effect is considered, none of these excesses are significant.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Ian Hinchliffe Answers Your Higgs Boson Questions

contingent with the ATLAS experiment at CERN, answers many of your questions about the Higgs boson. Ian invited viewers to send in questions about the Higgs via email, Twitter, Facebook, or YouTube in an "Ask a Scientist" video posted July 3: http://youtu.be/xhuA3wCg06s CERN's July 4 announcement that the ATLAS and CMS experiments at the Large Hadron Collider have discovered a particle "consistent with the Higgs boson" has raised questions about what scientists have found and what still remains to be found -- and what it all means. If you have suggestions for future "Ask a Scientist" videos, post them below or send ideas to askascientist@lbl.gov

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2012

Combined search for the Standard Model Higgs boson using up to 4.9 fb(-1) of pp collision data at root s=7 TeV 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{sup -1} to 4.9 fb{sup -1} of pp collisions collected at {radical}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 m{sub H} {approx} 126 GeV with a local significance of 3.5 standard deviations ({sigma}). The local significances of H {yields} {gamma}{gamma}, H {yields} ZZ{sup (*)} {yields} {ell}{sup +}{ell}{sup -}{ell}{prime}{sup +}{ell}{prime}{sup -} and H {yields} WW{sup (*)} {yields} {ell}{sup +}{nu}{ell}{prime}{sup -}{bar {nu}}, the three most sensitive channels in this mass range, are 2.8{sigma}, 2.1{sigma} and 1.4{sigma}, 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 {approx}1.4% or, equivalently, 2.2{sigma}.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Theoretical Summary Lecture for Higgs Hunting 2012

In this lecture, I review some of the perspectives on the Higgs boson discussed at the Higgs Hunting 2012 Worshop and discuss the short- and long-term aspects of Higgs physics.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Charged Particle Optics in Circular Higgs Factory

Similar to a super B-factory, a circular Higgs factory will require strong focusing systems near the interaction points and a low-emittance lattice in arcs to achieve a factory luminosity. At electron beam energy of 120 GeV, beamstrahlung effects during the collision pose an additional challenge to the collider design. In particular, a large momentum acceptance at 2 percent level is necessary to retain an adequate beam lifetime. This turns out to be the most challenging aspect in the design of circular Higgs factory. In this paper, an example will be provided to illustrate the beam dynamics in circular Higgs factory, emphasizing on the chromatic optics. Basic optical modules and advanced analysis will be presented. Most important, we will show that 2% momentum aperture is achievable

43 PARTICLE ACCELERATORS↗
DOE OSTI2010

Search for the Higgs boson in the $\gamma \gamma$ final state at the Tevatron

We present searches for Higgs bosons decaying to the di-photon final state using up to 5.4 fb{sup -1} of data at a center-of-mass energy of {radical}s = 1.96 TeV at the Fermilab Tevatron collider. Whilst the branching ratio to the di-photon final state is small in the Standard Model, this channel contributes appreciably to the overall Higgs sensitivity at the Tevatron. In parallel, the limit is re-interpreted in fermiophobic models where the di-photon branching ratio is considerably larger. This decay channel will be of major importance in the light mass Standard Model Higgs search at the LHC.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2010

Improved Search for a Higgs Boson Produced in Association with Z->l+l- in proton antiproton Collisions at sqrt(s) = 1.96 TeV

We present a search for the standard model Higgs boson produced with a Z boson in 4.1 fb{sup -1} of data collected with the CDF II detector at the Tevatron. In events consistent with the decay of the Higgs boson to a bottom-quark pair and the Z boson to electrons or muons, we set 95% credibility level upper limits on the ZH production cross section times the H {yields} b{bar b} branching ratio. Improved analysis methods enhance signal sensitivity by 20% relative to previous searches beyond the gain due to the larger data sample. At a Higgs boson mass of 115 GeV/c{sup 2} we set a limit of 5.9 times the standard model value.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2026

Search for Higgs bosons produced in association with a high-energy photon via vector-boson fusion and decaying to a pair of b -quarks in the ATLAS detector

A search for Standard Model Higgs bosons produced in association with a high-energy photon and decaying to $b\bar{b}$ is performed using 133 fb −1 of $\sqrt{s}$ = 13 TeV pp collision data collected with the ATLAS detector at the Large Hadron Collider at CERN. The photon requirement reduces the multijet background, and the H → $b\bar{b}$ decay is the dominant decay mode. Event selection requirements target events produced by vector-boson fusion, the dominant production mode in this channel. Several improvements enhance the search sensitivity compared to previous measurements. These improvements include better background modelling and characterization, the use of a neural-network classifier, and an updated signal extraction strategy adopting a direct binned-likelihood fit to the classifier output. With these improvements, the Higgs boson signal strength is measured to be 0.2 ± 0.7 relative to the Standard Model prediction. This corresponds to an observed significance of 0.3 standard deviations, compared to an expectation of 1.5 standard deviations assuming the Standard Model.

ATLAS experiment↗
DOE OSTI2015

Search for the $ b\overline{b} $ decay of the Standard Model Higgs boson in associated ( W/Z ) H production with the ATLAS detector

A search for the $ b\overline{b} $ decay of the Standard Model Higgs boson is performed with the ATLAS experiment using the full dataset recorded at the LHC in Run 1. The integrated luminosities used are 4.7 and 20.3 fb -1 from pp collisions at √s = 7 and 8 TeV, respectively. The processes considered are associated (W/Z)H production, where W → eν/μν, Z → ee/μμ and Z → νν. The observed (expected) deviation from the background-only hypothesis corresponds to a significance of 1.4 (2.6) standard deviations and the ratio of the measured signal yield to the Standard Model expectation is found to be μ = 0.52 ± 0.32 (stat.) ± 0.24 (syst.) for a Higgs boson mass of 125.36 GeV. The analysis procedure is validated by a measurement of the yield of (W/Z)Z production with Z → $ b\overline{b} $ in the same final states as for the Higgs boson search, from which the ratio of the observed signal yield to the Standard Model expectation is found to be 0.74 ± 0.09 (stat.) ± 0.14 (syst.).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Higgs self-coupling measurements at a 100 TeV hadron collider

An important physics goal of a possible next-generation high-energy hadron collider will be precision characterisation of the Higgs sector and electroweak symmetry breaking. A crucial part of understanding the nature of electroweak symmetry breaking is measuring the Higgs self-interactions. We study dihiggs production in proton-proton collisions at 100 TeV centre of mass energy in order to estimate the sensitivity such a machine would have to variations in the trilinear Higgs coupling around the Standard Model expectation. We focus on the bb¯γγ final state, including possible enhancements in sensitivity by exploiting dihiggs recoils against a hard jet. In conclusion, we find that it should be possible to measure the trilinear self-coupling with 40% accuracy given 3/ab and 12% with 30/ab of data.

43 PARTICLE ACCELERATORS↗
DOE OSTI2019

Lattice-friendly gauge completion of a composite Higgs with top partners

We give an explicit example of a composite Higgs model with a pseudo-Nambu-Goldstone Higgs in which the top Yukawa coupling is generated via the partial compositeness mechanism. This mechanism requires composite top partners which are relatively light compared to the typical mass scale of the strongly coupled theory. While most studies of the phenomenology of such models have focused on a bottom-up approach with a minimal effective theory, a top-down approach suggests that that the theory should contain a limit in which an unbroken global chiral symmetry protects the mass of the top partners, and the spectrum of the partners satisfies `t Hooft matching conditions. We therefore consider a model for the UV gauge group which could provide a solution to the matching conditions, and note that the relatively light fermions and pseudo-Goldstone bosons fall into complete multiplets of a large approximate global symmetry. This implies that the spectrum of particles lighter than a few TeV is non-minimal. Our example illustrates likely features of a composite Higgs theory, and also serves as an example of a non-chiral theory with no sign problem and a possible solution to `t Hooft matching conditions. It would therefore be very interesting for a lattice exploration. We find in this example that for some low-energy parameters in the effective theory the top partners can decay into high multiplicity final states, which could be difficult for the Large Hadron Collider (LHC) to constrain. This may potentially allow for the top partners to be lighter than those in more minimal models.

Lattice Quantum Field Theory↗
DOE OSTI2024

Di-Higgs Signatures in Neutral Naturalness

The Higgs boson was the last fundamental piece of the Standard Model to be experimentally confirmed. LHC is embarked in a quest to probe the possibility that this particle provides a portal to new physics. One front of this quest consists in measuring the interactions of the Higgs with itself and with other SM particles to a high precision. In a more exotic front, the LHC is searching for the possibility that a pair of Higgses (HH) is the evidence of a new resonance. Such resonances are predicted in models with extended Higgs sectors, extra dimensions, and in models with exotic bound states. In this paper we show how scalar quirks in Folded Supersymmetry can give rise to HH resonances. We point out a viable sector of the parameter space in which HH is the dominant decay channel for these {\it squirkonium} bound states. We found that future runs of the LHC could discover HH resonances in the range of 0.5 - 1.6 TeV under reasonable assumptions. Furthermore, for a given mass and width of the HH signal, the model predicts the branching ratio of the subsequent decay modes of the heavy resonance. Finding the extra decay modes in the predicted pattern can serve as a smoking gun to confirm the model.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

A 125 GeV SM-like Higgs in the MSSM and the γγ rate

We consider the possibility of a Standard Model (SM)-like Higgs in the context of the Minimal Supersymmetric Standard Model (MSSM), with a mass of about 125 GeV and with a production times decay rate into two photons which is similar or somewhat larger than the SM one. The relatively large value of the SM-like Higgs mass demands stops in the several hundred GeV mass range with somewhat large mixing, or a large hierarchy between the two stop masses in the case that one of the two stops is light. We find that, in general, if the heaviest stop mass is smaller than a few TeV, the rate of gluon fusion production of Higgs bosons decaying into two photons tends to be somewhat suppressed with respect to the SM one in this region of parameters. However, we show that an enhancement of the photon decay rate may be obtained for light third generation sleptons with large mixing, which can be naturally obtained for large values of tan β and sizable values of the Higgsino mass parameter.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

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

A search for the standard model Higgs boson in the H to ZZ to 2&ell; 2nu decay channel, where &ell; = e or mu, 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 inverse femtobarns. 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.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Search for a Higgs boson in the decay channel $H$ to ZZ(*) to $q$ qbar $\ell^-$ l+ in $pp$ collisions at $\sqrt{s}=7$ TeV

A search for the standard model Higgs boson decaying into two Z bosons with subsequent decay into a final state containing two quark jets and two leptons, H to ZZ(*) to q q-bar l-l+ is presented. Results are based on data corresponding to an integrated luminosity of 4.6 inverse femtobarns of proton-proton collisions at sqrt(s)=7 TeV, collected with the CMS detector at the LHC. In order to discriminate between signal and background events, kinematic and topological quantities, including the angular spin correlations of the decay products, are employed. Events are further classified according to the probability of the jets to originate from quarks of light or heavy flavor or from gluons. No evidence for the Higgs boson is found, and upper limits on its production cross section are determined for a Higgs boson of mass between 130 and 600 GeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗