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Bross, A

Publications and source records attributed to Bross, A.

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

Combined Search for the Standard Model Higgs Boson Decaying to bb̄ Using the D0 Run II Data Set

We present the results of the combination of searches for the standard model Higgs boson produced in association with a W or Z boson and decaying into bb̄ using the data sample collected with the D0 detector in pp̄ collisions at √s=1.96 TeV at the Fermilab Tevatron Collider. We derive 95% C.L. upper limits on the Higgs boson cross section relative to the standard model prediction in the mass range 100 GeV≤M H ≤150 GeV, and we exclude Higgs bosons with masses smaller than 102 GeV at the 95% C.L. In the mass range 120 GeV≤M H ≤145 GeV, the data exhibit an excess above the background prediction with a global significance of 1.5 standard deviations, consistent with the expectation in the presence of a standard model Higgs boson.

Abazov, V. M.↗
DOE OSTI2012

Search for the standard model Higgs Boson in associated W H production in 9.7 fb – 1 of p p ¯ collisions with the D0 detector

Here, 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$\times\sigma_{\rm SM}$.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Search for Higgs boson production in oppositely charged dilepton and missing energy events in pp̄ collisions at √s=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→WW decays. The events are selected from data corresponding to 8.6 fb⁻¹ of integrated luminosity in pp̄ collisions at √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.

Abazov, V. M.↗
DOE OSTI2012

Observation of a narrow mass state decaying into Υ(1S)+γ in pp̄ collisions at √s=1.96 TeV

Using data corresponding to an integrated luminosity of 1.3 fb⁻¹, we observe a narrow mass state decaying into Υ(1S)+γ, where the Υ(1S) meson is detected by its decay into a pair of oppositely charged muons, and the photon is identified through its conversion into an electron-positron pair. The significance of this observation is 5.6 standard deviations. The mass of the state is centered at 10.551±0.014(stat)±0.017(syst) GeV/c², which is consistent with that of the state recently observed by the ATLAS Collaboration.

Abazov, V. M.↗
DOE OSTI2012

Measurement of the photon plus b-jet production differential cross section in $p\bar{p}$ collisions at $\sqrt{s}$ =1.96 TeV

We present measurements of the differential cross section dσ/dρ γ τ for the inclusive production of a photon in association with a b -quark jet for photons with rapidities |y γ | < 1.0 and 30 < ρ γ τ < 300 GeV , as well as for photons with 1.5 <|y γ | < 2.5 and 30 < ρ γ τ < 200 GeV, where ρ γ τ is the photon transverse momentum. The b -quark jets are required to have p T > 15 GeV and rapidity |y jet | < 1.5. The results are based on data corresponding to an integrated luminosity of 8.7 fb -1 , recorded with the D0 detector at the Fermilab Tevatron $p\bar{p}$ Collider at $\sqrt{s}$ =1.96 TeV. The measured cross sections are compared with next-to-leading order perturbative QCD calculations using different sets of parton distribution functions as well as to predictions based on the kT-factorization QCD approach, and those from the SHERPA and PYTHIA Monte Carlo event generators.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Combination of searches for anomalous top quark couplings with 5.4 fb(-1) of p(p)over-bar collisions

We present measurements of the tWb coupling form factors using information from electroweak single top quark production and from the helicity of W bosons from top quark decays in t{bar t} events. We set upper limits on anomalous tWb coupling form factors using data collected with the D0 detector at the Tevatron p{bar p} collider corresponding to an integrated luminosity of 5.4 fb{sup -1}.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

Beam Profile Measurement in MTA Beam Line for High Pressure RF Cavity Beam Test

Recent High Pressure RF (HPRF) cavity experiment at MuCool Test Area (MTA) has used 400 MeV Linac proton beam to study the beam loading effect. When the energetic proton beam passes through the cavity, it ionizes the inside gas and produces the electrons. These electrons consume RF power inside the cavity. Number of electrons produced per cm inside the cavity (at 950 psi Hydrogen gas) per incident proton is {approx} 1200. The measurement of beam position and profile are necessary. MTA is flammable gas (Hydrogen) hazard zone so we have developed a passive beam diagnostic instrument using Chromox-6 scintillation screen and CCD camera. This paper presents quantitative information about beam position and beam profile. Neutral density filter was used to avoid saturation of CCD camera. Image data is filtered and fitted with Gaussian function to compute the beam size. The beam profile obtained from scintillation screen shall be compared with multi-wire beam profile.

08 HYDROGEN↗
DOE OSTI2012

Measurements of WW and WZ Production in W+jets Final States in pp̄ Collisions

We study WW and WZ production with lνqq (l=e,μ) final states using data collected by the D0 detector at the Fermilab Tevatron Collider corresponding to 4.3 fb⁻¹ of integrated luminosity from pp̄ collisions at √s=1.96 TeV. Assuming the ratio between the production cross sections σ(WW) and σ(WZ) as predicted by the standard model, we measure the total WV (V=W,Z) cross section to be σ(WV)=19.6 +3.2 -3.0 pb and reject the background-only hypothesis at a level of 7.9 standard deviations. We also use b-jet discrimination to separate the WZ component from the dominant WW component. Simultaneously fitting WW and WZ contributions, we measure σ(WW)=15.9 +3.7 -3.2 pb and σ(WZ)=3.3 +4.1 -3.3 pb, which is consistent with the standard model predictions.

Abazov, V. M.↗
DOE OSTI2012

Design Concept for nu-STORM: An Initial Very Low-Energy Neutrino Factory

We present a design concept for a {nu} source from a STORage ring for Muons ({nu}STORM). In this initial design a high-intensity proton beam produces {approx}5 GeV pions that provide muons that are captured using 'stochastic injection' within a 3.6 GeV racetrack storage ring. In 'stochastic injection', the {approx}5 GeV pion beam is transported from the target into the storage ring, dispersion-matched into a long straight section. (Circulating and injection orbits are separated by momentum.) Decays within that straight section provide muons that are within the {approx}3.6 GeV/c ring momentum acceptance and are stored for the muon lifetime of {approx}1000 turns. Muon (and pion) decays in the long straight sections provide neutrino beams of precisely known flux and flavor that can be used for precision measurements of electron and muon neutrino interactions, and neutrino oscillations or disappearance at L/E = {approx}1m/MeV. The facility is described, and variations are discussed.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

Search for Higgs bosons of the minimal supersymmetric standard model in p(p)over-bar collisions at root s=1.96 TeV

We report results from searches for neutral Higgs bosons produced in p{bar p} collisions recorded by the D0 experiment at the Fermilab Tevatron Collider. We study the production of inclusive neutral Higgs boson in the {tau}{tau} final state and in association with a b quark in the b{tau}{tau} and bbb final states. These results are combined to improve the sensitivity to the production of neutral Higgs bosons in the context of the minimal supersymmetric standard model (MSSM). The data are found to be consistent with expectation from background processes. Upper limits on MSSM Higgs boson production are set for Higgs boson masses ranging from 90 to 300 GeV. We exclude tan {beta} > 20-30 for Higgs boson masses below 180 GeV. These are the most stringent constraints on MSSM Higgs boson production in p{bar p} collisions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Search for pair production of the scalar top quark in muon plus tau final states

Here, we present a search for the pair production of scalar top quarks ($\sim\atop{t}$ 1 ), the lightest supersymmetric partners of the top quarks, in $p\bar{p}$ collisions at a center-of-mass energy of 1.96 TeV, using data corresponding to an integrated luminosity of 7.3fb -1 collected with the D0 experiment at the Fermilab Tevatron Collider. Each scalar top quark is assumed to decay into a b quark, a charged lepton, and a scalar neutrino (ν˜). We investigate final states arising from$\sim\atop{t}$ 1 $≂\atop{t}$ 1 →$b\bar{b}$ μτ$\sim\atop{v}$$\sim\atop{v}$ and $\sim\atop{t}$ 1 $≂\atop{t}$ 1 →$b\bar{b}$ ττ$\sim\atop{v}$$\sim\atop{v}$. With no significant excess of events observed above the background expected from the standard model, we set exclusion limits on this production process in the (m$\sim\atop{t}$ 1 , m$\sim\atop{v}$) plane.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Search for Charged Massive Long-Lived Particles

We report on a search for charged massive long-lived particles (CMLLPs), based on 5.2 fb{sup -1} of integrated luminosity collected with the D0 detector at the Fermilab Tevatron p{bar p} collider. We search for events in which one or more particles are reconstructed as muons but have speed and ionization energy loss (dE/dx) inconsistent with muons produced in beam collisions. CMLLPs are predicted in several theories of physics beyond the standard model. We exclude pair-produced long-lived gaugino-like charginos below 267 GeV and Higgsino-like charginos below 217 GeV at 95% C.L., as well as long-lived scalar top quarks with mass below 285 GeV.

43 PARTICLE ACCELERATORS↗