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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 829 records · Page 46
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DOE OSTI2011

Search for Chargino-Neutralino Associated Production in Dilepton Final States with Tau Leptons

We present a search for chargino and neutralino supersymmetric particles yielding same signed dilepton final states including one hadronically decaying tau lepton using 6.0 fb{sup -1} of data collected by the the CDF II detector. This signature is important in SUSY models where, at high tan {beta}, the branching ratio of charginos and neutralinos to tau leptons becomes dominant. We study event acceptance, lepton identification cuts, and efficiencies. We set limits on the production cross section as a function of SUSY particle mass for certain generic models.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Heavy Flavor Baryons at the Tevatron

The Tevatron experiments CDF and D0 have filled many empty spots in the spectrum of heavy baryons over the last few years. The most recent results are described in this article: The first direct observation of the {Xi}{sub b}{sup 0}, improved measurements of {Sigma}{sub b} properties, a new measurement of the {Lambda}{sub b} {yields} J/{psi}{Lambda} branching ratio, and a high-statistics study of charm baryons.

43 PARTICLE ACCELERATORS↗
DOE OSTI2011

Measurement of the Cross Section for Prompt Isolated Diphoton Production in $p\bar{p}$ Collisions at \sqrt s = 1.96 TeV

This article reports a measurement of the cross section of prompt isolated photon pair production in p{bar p} collisions at a total energy {radical}s = 1.96 TeV using data of 5.36 fb{sup -1} integrated luminosity collected with the CDF II detector at the Fermilab Tevatron. The measured cross section, differential in basic kinematic variables, is compared with three perturbative QCD predictions, a leading order (LO) parton shower calculation and two next-to-leading order (NLO) calculations. The NLO calculations reproduce most aspects of the data. By including photon radiation from quarks before and after hard scattering, the parton shower prediction becomes competitive with the NLO predictions.

43 PARTICLE ACCELERATORS↗
DOE OSTI2011

B Physics at the TeVatron

The CDF and D0 experiments at the Tevatron p{bar p} collider established that extensive and detailed exploration of the b-quark dynamics is possible in hadron collisions, with results competitive and supplementary to those from e{sup +}e{sup -} colliders. This provides a rich, and highly rewarding program that is currently reaching full maturity. I report a few recent world-leading results on rare decays, CP-violation in B{sub s}{sup 0} mixing, b {yields} s penguin decays, and charm physics.

43 PARTICLE ACCELERATORS↗
DOE OSTI2011

Electroweak and QCD Results from the Tevatron

The Tevatron collider has been remarkably successful and has so far delivered more than 11 fb{sup -1} of data to both the CDF and D0 experiments. Though the LHC has replaced the Tevatron as the world's most powerful collider, years of detector calibration, the huge size of the dataset and the nature of pp collisions will keep the Tevatron competitive in many selected topics in the near future. More than 10 fb{sup -1} of data has been collected by each experiment. Good understanding of the detector performance has been demonstrated by the high precision W boson mass ({Delta}M{sub W} = 31 MeV) and top quark mass ({Delta}M{sub t} = 1.06 GeV) measurements. We report the latest electroweak and QCD results from both experiments. Most analyses presented here used 4-6 fb{sup -1} of data.

43 PARTICLE ACCELERATORS↗
DOE OSTI2011

Rare B meson decays at the Tevatron

Rare B meson decays are an excellent probe for beyond the Standard Model physics. Two very sensitive processes are the B{sub s,d}{sup 0} {yields} {mu}{sup +}{mu}{sup -} and b {yields} s{mu}{sup +}{mu}{sup -} decays. We report recent results at a center of mass energy of {radical}s = 1.96 TeV from the CDF II and D0 collaborations using between 3.7 fb{sup -1} and 6.9 fb{sup -1} taken during Run II of the Fermilab Tevatron Collider.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Top Quark Production at the Tevatron

The top quark is the most recently discovered of the standard model quarks, and because of its very large mass, studies of the top quark and its interactions are important both as tests of the standard model and searches for new phenomena. In this document, recent results of analyses of top quark production, via both the electroweak and strong interactions, from the CDF and D0 experiments are presented. The results included here utilize a dataset corresponding to up to 6 fb{sup -1} of integrated luminosity, slightly more than half of the dataset recorded by each experiment before the Tevatron was shutdown in September 2011.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Search for the Standard Model Higgs boson in final states with $b$ quarks at the Tevatron

We present the result of searches for a low mass Standard Model Higgs boson produced in association with a W or a Z boson at a center-of-mass energy of {radical}s = 1.96 TeV with the CDF and D0 detectors at the Fermilab Tevatron collider. The search is performed in events containing one or two b tagged jets in association with either two leptons, or one lepton and an imbalance in transverse energy, or simply a large imbalance in transverse energy. Datasets corresponding to up to 8.5 fb{sup -1} of integrated luminosity are considered in the analyses. These are the most powerful channels in the search for a low mass Higgs boson at the Tevatron. Recent sensitivity improvements are discussed. For a Higgs mass of 115 GeV/c{sup 2}, the expected sensitivity for the most sensitive individual analyses reaches 2.3 times the SM prediction at 95% confidence level (C.L.), with all limits below 5 times the SM. Additionally, a WZ/ZZ cross-section measurement is performed to validate the analysis techniques deployed for searching for the Higgs.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

QCD measurements at the Tevatron

Selected quantum chromodynamics (QCD) measurements performed at the Fermilab Run II Tevatron p{bar p} collider running at {radical}s = 1.96 TeV by CDF and D0 Collaborations are presented. The inclusive jet, dijet production and three-jet cross section measurements are used to test perturbative QCD calculations, constrain parton distribution function (PDF) determinations, and extract a precise value of the strong coupling constant, {alpha}{sub s}(m{sub Z}) = 0.1161{sub -0.0048}{sup +0.0041}. Inclusive photon production cross-section measurements reveal an inability of next-to-leading-order (NLO) perturbative QCD (pQCD) calculations to describe low-energy photons arising directly in the hard scatter. The diphoton production cross-sections check the validity of the NLO pQCD predictions, soft-gluon resummation methods implemented in theoretical calculations, and contributions from the parton-to-photon fragmentation diagrams. Events with W/Z+jets productions are used to measure many kinematic distributions allowing extensive tests and tunes of predictions from pQCD NLO and Monte-Carlo (MC) event generators. The charged-particle transverse momenta (p{sub T}) and multiplicity distributions in the inclusive minimum bias events are used to tune non-perturbative QCD models, including those describing the multiple parton interactions (MPI). Events with inclusive production of {gamma} and 2 or 3 jets are used to study increasingly important MPI phenomenon at high p{sub T}, measure an effective interaction cross section, {sigma}{sub eff} = 16.4 {+-} 2.3 mb, and limit existing MPI models.

43 PARTICLE ACCELERATORS↗
DOE OSTI2010

Top quark production at the Tevatron

The Fermilab Tevatron has, until recently, been the only accelerator with sufficient energy to produce top quarks. The CDF and D0 experiments have collected large samples of top quarks. We report on recent top quark production measurements of the single top and t{bar t} production cross sections, as well as studies of the t{bar t} invariant mass distribution and a search for highly boosted top quarks.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Achievements and Lessons from Tevatron

For almost a quarter of a century, the Tevatron proton-antiproton collider was the centerpiece of the world's high energy physics program - beginning operation in December of 1985 until it was overtaken by LHC in 2011. The aim of the this unique scientific instrument was to explore the elementary particle physics reactions with center of mass collision energies of up to 1.96 TeV. The initial design luminosity of the Tevatron was 10{sup 30} cm{sup -2}s{sup -1}, however as a result of two decades of upgrades, the accelerator has been able to deliver 430 times higher luminosities to each of two high luminosity experiments, CDF and D0. Tevatron will be shut off September 30, 2011. The collider was arguably one of the most complex research instruments ever to reach the operation stage and is widely recognized for many technological breakthroughs and numerous physics discoveries. Below we briefly present the history of the Tevatron, major advances in accelerator physics, and technology implemented during the long quest for better and better performance. We also discuss some lessons learned from our experience.

43 PARTICLE ACCELERATORS↗
DOE OSTI2011

$B$ and $D$ Physics from the Tevatron

The CDF and D0 experiments at the Tevatron pp collider established that extensive and detailed exploration of the b-quark dynamics is possible in hadron collisions, with results competitive and supplementary to B-factories. In this paper we review the current state of Tevatron's heavy flavor measurements considering two main categories: searches for non standard model physics (results on rare decays and CP-violation) and determinations of standard model parameters (annihilation in B {yields} h{sup +}h{sup -} decays and {gamma} angle measurement through B {yields} DK modes).

43 PARTICLE ACCELERATORS↗
DOE OSTI2011

$W/Z$ and Diboson Properties

Most recent measurements of properties of W and Z gauge bosons at hadron colliders are presented. The measurements were performed by ATLAS, CMS, and LHCb collaborations with proton-proton collisions at the LHC and by CDF and D0 collaborations with proton-antiproton collisions at the Tevatron. Center-of-mass energy was 7 TeV and 1.96 TeV at the LHC and Tevatron respectively. Integrated luminosity ranges from 35 pb{sup -1} to 1.02 pb{sup -1} for LHC and from 0.2 fb{sup -1} to 7.1 fb{sup -1} for Tevatron.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Searches for diboson production at the Tevatron in final states containing heavy-flavor jets

Recent searches performed by the CDF and D0 collaborations at the Tevatron for diboson production in final states containing heavy-flavor jets are reported. The searches for WZ and ZZ can be regarded as the ultimate benchmark for the corresponding searches for a low-mass Higgs boson in the WH and ZH final states. Using the exact same techniques as for those Higgs boson searches, the D0 collaboration measured a cross section for WZ/ZZ production of 1.13 {+-} 0.36 times its expectation in the standard model, with a diboson signal significance of 3.3 standard deviations (2.9 expected).

43 PARTICLE ACCELERATORS↗
DOE OSTI2011

An additional study of multi-muon events produced in $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV

We present one additional study of multi-muon events produced at the Fermilab Tevatron collider and recorded by the CDF II detector. We use a data set acquired with a dedicated dimuon trigger and corresponding to an integrated luminosity of 3.9 fb{sup -1}. We investigate the distribution of the azimuthal angle between the two trigger muons in events containing at least four additional muon candidates to test the compatibility of these events with originating from known QCD processes. We find that this distribution is markedly different from what is expected from such QCD processes and this observation strongly disfavours the possibility that multi-muon events result from an underestimate of the rate of misidentified muons in ordinary QCD events.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

Rare B Meson Decays at the Tevatron

Rare B meson decays are an excellent probe for beyond the Standard Model physics. Two very sensitive processes are the b {yields} s{mu}{sup +}{mu}{sup -} and B{sub s,d}{sup 0} {yields} {mu}{sup +}{mu}{sup -} decays. We report recent results at a center of mass energy of {radical}s = 1.96 TeV from CDF II using 7 fb{sup -1} at the Fermilab Tevatron Collider.

36 MATERIALS SCIENCE↗
DOE OSTI2011

Study of the dijet invariant mass in w + 2 jet events

The D0 Collaboration presents a study of the dijet invariant mass spectrum, M{sub jj}, in events with two jets produced in association with a W {yields} {ell}{nu} boson. The goal is to verify a claim from the CDF Collaboration about the possible existence of an anomalous dijet resonance at M{sub jj} {approx} 145 GeV. Thus, we investigate the 110 GeV < M{sub jj} < 170 GeV mass range and report our results.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Search for WH associated production at D{\o} Tevatron

The Higgs mechanism introduced in 1964 gives a satisfactory solution to a major problem of the standard model of elementary particles: the origin of the mass. It predicts the existence of the Higgs scalar boson, which has not been discovered experimentally yet. The Tevatron, a hadron accelerator based at Fermi National Accelerator Laboratory near Chicago, has delivered data to its two multi-purpose detectors CDF and DZERO since 1983 up to september 2011. Leaving us about 11 fb{sup -1} of data per experiment to analyze. Associated production of a Higgs boson and a vector gauge boson W or Z is the main search channel for a light standard Higgs boson (i.e. below 135 GeV/c{sup 2}). Using data collected by DZERO, we are looking for this production mode taking advantage of sophisticated techniques to improve the signal sensitivity such as b-jet identification and multivariate discriminants. In the end, a statistical approach allows us to set an upper limit on the ratio between the observed (resp. expected) Higgs production cross section and its theoretical cross section. The latest result obtained in the WH channel using 8.5 fb{sup -1} at DZERO is 4.6 (resp. 3.5) for a 115 GeV/c{sup 2} Higgs boson.

43 PARTICLE ACCELERATORS↗