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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2011

Measurement of the Properties of the top Quark at D{\O}

Different measurements of the properties of the top quark using up to 5.4 fb{sup -1} collected with the D0 detector at the Fermilab Tevatron collider are presented. The top mass is obtained from a study of dilepton and lepton+jets final states, while the width is obtained from a combination of the measurements of the single top production via t-channel exchange and the determination of the t {yields} Wb branching ratio. Furthermore the measurement of the helicity of the W boson from top quark decays, a measurement of t{bar t} spin correlations and a measurement of the jet pull (color flow) in t{bar t} events are presented. A wealth of measurements of properties of the top quark at D0 have been discussed showing the great performance of the Tevatron and the D0 detector. All results are consistent with the standard model expectations. The final D0 data sample will have 2-3 times the presented statistics allowing for new & more precise results in the future.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

Study of jets produced in association with a W boson in pp collisions at root s=7 TeV with the ATLAS detector

We report a study of final states containing a W boson and hadronic jets, produced in proton-proton collisions at a center-of-mass energy of 7 TeV. The data were collected with the ATLAS detector at the CERN LHC and comprise the full 2010 data sample of 36 pb{sup -1}. Cross sections are determined using both the electron and muon decay modes of the W boson and are presented as a function of inclusive jet multiplicity, N{sub jet}, for up to five jets. At each multiplicity, cross sections are presented as a function of jet transverse momentum, the scalar sum of the transverse momenta of the charged lepton, missing transverse momentum, and all jets, the invariant mass spectra of jets, and the rapidity distributions of various combinations of leptons and final-state jets. The results, corrected for all detector effects and for all backgrounds such as diboson and top quark pair production, are compared with particle-level predictions from perturbative QCD. Leading-order multiparton event generators, normalized to the next-to-next-to-leading-order total cross section for inclusive W-boson production, describe the data reasonably well for all measured inclusive jet multiplicities. Next-to-leading-order calculations from MCFM, studied here for N{sub jet} {le} 2, and BlackHat-Sherpa, studied here for N{sub jet} {le} 4, are found to be mostly in good agreement with the data.

43 PARTICLE ACCELERATORS↗
DOE OSTI2013

Lepton production at the LHC from singly- and doubly-charged bilepton

Some extensions of the standard model predict the existence of particles having two units of leptonic charge, known as bileptons. One of such models is based on the SU(3){sub c} Multiplication-Sign SU(3){sub L} Multiplication-Sign U(1){sub X} symmetry group (3-3-1). Our search uses the minimal version of this model, having exotic charges for the quarks and gauge bosons. It predicts the existence of bileptons as vector particles having one unit of electric charge (V{sup {+-}}) or two units of electric charge (Y{sup {+-}{+-}}). Our aim is to establish the signatures for the production of four fermions in pp collisions at the LHC for 7 TeV center of mass energy. We present the total cross section and we show the leptons invariant mass and transverse momentum distributions. We conclude that LHC collider can show a clear signature for a process induced by bileptons as a signal of new physics.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Measurement of the W W cross section in root s=7 TeV pp collisions with the ATLAS detector and limits on anomalous gauge couplings

This Letter reports a measurement of the WW production cross section in {radical}s = 7 TeV pp collisions using data corresponding to an integrated luminosity of 1.02 fb{sup -1} collected with the ATLAS detector. Using leptonic decays of oppositely charged W bosons, the total measured cross section is {sigma}(pp {yields} WW) = 54.4 {+-} 4.0 (stat.) {+-} 3.9 (syst.) {+-} 2.0 (lumi.) pb, consistent with the Standard Model prediction of {sigma}(pp {yields} WW) = 44.4 {+-} 2.8 pb. Limits on anomalous electroweak triple-gauge couplings are extracted from a fit to the transverse-momentum distribution of the leading charged lepton in the event.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1992

Higgs-Boson Production in Nucleus-Nucleus Collisions

Cross section calculations are presented for the production of intermediate-mass Higgs bosons produced in ultrarelativistic nucleus-nucleus collisions via two photon fusion. The calculations are performed in position space using Baur's method for folding together the Weizsacker-Williams virtual-photon spectra of the two colliding nuclei. It is found that two photon fusion in nucleus-nucleus collisions is a plausible way of finding intermediate-mass Higgs bosons at the Superconducting Super Collider or the CERN Large Hadron Collider.

Norbury, John W.↗
DOE OSTI2012

Weak-triplet, color-octet scalars and the CDF dijet excess

We extend the standard model to include a weak-triplet and color-octet scalar. This 'octo-triplet' field consists of three particles, two charged and one neutral, whose masses and renormalizable interactions depend only on two new parameters. The charged octo-triplet decay into a W boson and a gluon is suppressed by a loop factor and an accidental cancellation. Thus, the main decays of the charged octo-triplet may occur through higher-dimensional operators, mediated by a heavy vectorlike fermion, into quark pairs. For an octo-triplet mass below the tb¯ threshold, the decay into Wb b¯ through an off-shell top quark has a width comparable to that into cs¯ or cb¯. Pair production with one octo-triplet decaying to two jets and the other decaying to a W and two soft b jets may explain the dijet-plus-W excess reported by the CDF Collaboration. The same higher-dimensional operators lead to CP violation in B s -B¯ s mixing.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Search for Pair Production of a Heavy Up-Type Quark Decaying to a W Boson and a b Quark in the lepton plus jets Channel with the ATLAS Detector

A search is presented for production of a heavy up-type quark (t{prime}) together with its antiparticle, assuming subsequent decay to a W boson and a b quark, t{prime}{bar t}{prime} {yields} W{sup +}bW{sup -}{bar b}. The search is based on 1.04 fb{sup -1} of proton-proton collisions at {radical}s = 7 TeV collected by the ATLAS detector at the CERN Large Hadron Collider. Data are analyzed in the lepton+jets final state, characterized by a high transverse momentum isolated electron or muon, high missing transverse momentum, and at least three jets. No significant excess of events above the background expectation is observed. A 95% C.L. lower limit of 404 GeV is set for the mass of the t{prime} quark.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Top-Quark Mass Measurement Using Events with Missing Transverse Energy and Jets at CDF

We present a measurement of the top-quark mass using a sample of tt events in 5.7 fb{sup -1} of integrated luminosity from pp collisions at the Fermilab Tevatron with {radical}(s)=1.96 TeV and collected by the CDF II Detector. We select events having large missing transverse energy, and four, five, or six jets with at least one jet tagged as coming from a b quark, and reject events with identified charged leptons. This analysis considers events from the semileptonic tt decay channel, including events that contain tau leptons. The measurement is based on a multidimensional template method. We fit the data to signal templates of varying top-quark masses and background templates, and measure a top-quark mass of M{sub top}=172.32{+-}2.4(stat){+-}1.0(syst) GeV/c{sup 2}.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at root s=7 TeV with the ATLAS experiment

This paper describes an analysis of the angular distribution of W {yields} e{nu} and W {yields} {mu}{nu} decays, using data from pp collisions at {radical}s = 7 TeV recorded with the ATLAS detector at the LHC in 2010, corresponding to an integrated luminosity of about 35 pb{sup -1}. Using the decay lepton transverse momentum and the missing transverse momentum, the W decay angular distribution projected onto the transverse plane is obtained and analysed in terms of helicity fractions f{sub 0}, f{sub L} and f{sub R} over two ranges of W transverse momentum (p{sub T}{sup W}): 35 < p{sub T}{sup W} < 50 GeV and p{sub T}{sup W} > 50 GeV. Good agreement is found with theoretical predictions. For p{sub T}{sup W} > 50 GeV, the values of f{sub 0} and f{sub L}-f{sub R}, averaged over charge and lepton flavour, are measured to be: f{sub 0} = 0.127 {+-} 0.030 {+-} 0.108 and f{sub L} - f{sub R} = 0.252 {+-} 0.017 {+-} 0.030, where the first uncertainties are statistical, and the second include all systematic effects.

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↗
NASA NTRS1990

Higgs-boson production in nucleus-nucleus collisions

Cross-section calculations are presented for the production of intermediate-mass Higgs bosons produced in ultrarelativistic nucleus-nucleus collisions via two-photon fusion. The calculations are performed in position space using Baur's method for folding together the Weizsacker-Williams virtual-photon spectra of the two colliding nuclei. It is found that two-photon fusion in nucleus-nucleus collisions is a plausible way of finding intermediate-mass Higgs bosons at the Superconducting Super Collider or the CERN Large Hadron Collider.

NASA Discipline Radiation Health↗
DOE OSTI2018

In-medium loop corrections and longitudinally polarized gauge bosons in high-energy showers

The splitting processes of bremsstrahlung and pair production in a medium are coherent over large distances in the very high energy limit, which leads to a suppression known as the Landau-Pomeranchuk-Migdal (LPM) effect. We continue study of the case when the coherence lengths of two consecutive splitting processes overlap (which is important for understanding corrections to standard treatments of the LPM effect in QCD), avoiding soft-emission approximations. In this particular paper, we show (i) how the “instantaneous” interactions of Light-Cone Perturbation Theory must be included in the calculation to account for effects of longitudinally-polarized gauge bosons in intermediate states, and (ii) how to compute virtual corrections to LPM emission rates, which will be necessary in order to make infrared-safe calculations of the characteristics of in-medium QCD showering of high-energy partons. In order to develop these topics in as simple a context as possible, we will focus in the current paper not on QCD but on large-N f QED, where N f is the number of electron flavors.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Wilson Prize article: Reflections on our experiences with developing the theory of intrabeam scattering

We discuss our experiences with developing detailed theoretical descriptions of intrabeam scattering in particle accelerators. We focus on the historical importance of understanding intrabeam scattering for the successful operation of a variety of accelerators around the world. In doing so, we highlight the fact that the theoretical understanding of intrabeam scattering played a crucial role in the discovery of the top quark at Fermilab, intermediate vector bosons W ± , Z and the Higgs particle at CERN, and the perfect liquid quark-gluon plasma at Brookhaven’s Relativistic Heavy Ion Collider. We describe several useful high energy approximations to intrabeam scattering, including those that utilize a Modified Piwinski high energy approximation by Karl Bane that has gained wide usage in applications to electron damping rings and advanced light sources. Finally, we comment on the fact that a detailed understanding of intrabeam scattering at synchrotron-based advanced light sources is empowering many transformational discoveries in a myriad of disciplines.

43 PARTICLE ACCELERATORS↗