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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 37 records · Page 2
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DOE OSTI2011

b' search at the LHC

We consider the production and detection of a sequential, down type quark via the mode pp{yields}b'b-bar'{yields}W{sup +}W{sup -}tt-bar{yields}l{nu}{sub l}8j at the LHC, with the collision energy {radical}(s)=10 TeV and the total integrated luminosity around 1 fb{sup -1}. We assume m{sub b'}=m{sub t'}=600 GeV. A full reconstruction is employed and the signal and background discrimination is studied within a neural network approach. Our results show that this mode can make a useful contribution to the b' search.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Associated Higgs-W-Boson Production at Hadron Colliders: A Fully Exclusive QCD Calculation at NNLO

We consider QCD radiative corrections to standard model Higgs-boson production in association with a W boson in hadron collisions. We present a fully exclusive calculation up to next-to-next-to-leading order (NNLO) in QCD perturbation theory. To perform this NNLO computation, we use a recently proposed version of the subtraction formalism. Our calculation includes finite-width effects, the leptonic decay of the W boson with its spin correlations, and the decay of the Higgs boson into a bb pair. We present selected numerical results at the Tevatron and the LHC.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Search for the Higgs Boson in the H{yields}WW{yields}l{nu}jj Decay Channel in pp Collisions at {radical}(s)=7 TeV with the ATLAS Detector

A search for a Higgs boson has been performed in the H{yields}WW{yields}l{nu}jj channel in 1.04 fb{sup -1} of pp collision data at {radical}(s)=7 TeV recorded with the ATLAS detector at the Large Hadron Collider. 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 240 GeV<m{sub H}<600 GeV. The best sensitivity is reached for m{sub H}=400 GeV, where the 95% confidence level upper bound on the cross section for H{yields}WW production is 3.1 pb, or 2.7 times the standard model prediction.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Dijet invariant mass distribution in top quark hadronic decay with QCD corrections

The dijet invariant mass distributions from the hadronic decay of unpolarized top quark (t{yields}bW{sup +} followed by W{sup +}{yields}ud) are calculated, including the next-to-leading order QCD radiative corrections. We treat the top decay in the complex mass scheme due to the existence of the intermediate state W boson. Our analytical expressions are also available in different dimensional regularization schemes and {gamma}{sub 5} strategies. Finally, in order to construct the jets, we use different jet algorithms to compare their influences on our results. The obtained dijet mass distributions from the top quark decay are useful to distinguish these dijets from those produced via other sources and to clarify the issue about the recent CDF Collaboration's Wjj anomaly.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Mixed dark matter in left-right symmetric models

Motivated by the recently reported diboson and dijet excesses in Run 1 data at ATLAS and CMS, we explore models of mixed dark matter in left-right symmetric theories. In this study, we calculate the relic abundance and the elastic scattering cross section with nuclei for a number of dark matter candidates that appear within the fermionic multiplets of left-right symmetric models. In contrast to the case of pure multiplets, WIMP-nucleon scattering proceeds at tree-level, and hence the projected reach of future direct detection experiments such as LUX-ZEPLIN and XENON1T will cover large regions of parameter space for TeV-scale thermal dark matter. Decays of the heavy charged W{sup ′} boson to particles in the dark sector can potentially shift the right-handed gauge coupling to larger values when fixed to the rate of the Run 1 excesses, moving towards the theoretically attractive scenario, g{sub R}=g{sub L}. This region of parameter space may be probed by future collider searches for new Higgs bosons or electroweak fermions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Dark forces in the sky: signals from Z{sup ′} and the dark Higgs

We consider the indirect detection signals for a self-consistent hidden U(1) model containing a Majorana dark matter candidate, χ, a dark gauge boson, Z{sup ′}, and a dark Higgs, s. Compared with a model containing only a dark matter candidate and Z{sup ′} mediator, the addition of the scalar provides a mass generation mechanism for the dark sector particles and is required in order to avoid unitarity violation at high energies. We find that the inclusion of the two mediators opens up a new two-body s-wave annihilation channel, χχ→sZ{sup ′}. This new process, which is missed in the usual single-mediator simplified model approach, can be the dominant annihilation channel. This provides rich phenomenology for indirect detection searches, allows indirect searches to explore regions of parameter space not accessible with other commonly considered s-wave annihilation processes, and enables both the Z{sup ′} and scalar couplings to be probed. We examine the phenomenology of the sector with a focus on this new process, and determine the limits on the model parameter space from Fermi data on dwarf spheriodal galaxies and other relevant experiments.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

In search of elementary spin 0 particles

The Standard Model of strong and electroweak interactions uses point-like spin 1/2 particles as the building bricks of matter and point-like spin 1 particles as the force carriers. One of the most important questions to be answered by the present and future particle physics experiments is whether the elementary spin 0 particles exist, and if they do, what are their interactions with the spin 1/2 and spin 1 particles. Spin 0 particles have been searched extensively over the last decades. Several initial claims of their discoveries were finally disproved in the final experimental scrutiny process. The recent observation of the excess of events at the LHC in the final states involving a pair of vector bosons, or photons, is commonly interpreted as the discovery of the first elementary scalar particle, the Higgs boson. In this paper we recall examples of claims and subsequent disillusions in precedent searches spin 0 particles. We address the question if the LHC Higgs discovery can already be taken for granted, or, as it turned out important in the past, whether it requires a further experimental scrutiny before the existence of the first ever found elementary scalar particle is proven beyond any doubt. An example of the Double Drell–Yan process for which such a scrutiny is indispensable is discussed in some detail. - Highlights: • We present a short history of searches of spin 0 particles. • We construct a model of the Double Drell–Yan Process (DDYP) at the LHC. • We investigate the contribution of the DDYP to the Higgs searches background.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2013

Effective field theory: A modern approach to anomalous couplings

We advocate an effective field theory approach to anomalous couplings. The effective field theory approach is the natural way to extend the standard model such that the gauge symmetries are respected. It is general enough to capture any physics beyond the standard model, yet also provides guidance as to the most likely place to see the effects of new physics. The effective field theory approach also clarifies that one need not be concerned with the violation of unitarity in scattering processes at high energy. We apply these ideas to pair production of electroweak vector bosons. -- Highlights: •We discuss the advantages of effective field theories compared to anomalous couplings. •We show that one need not be concerned with unitarity violation at high energy. •We discuss the application of effective field theory to weak boson physics.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Physical Degrees of Freedom for Gauge Fields and the Issue of Spin

The conflict between the physical degrees of freedom of gauge bosons and the Lorentz group irreps naturally used to describe their couplings to matter fields are illustrated and discussed, and applied to issues of linear and angular momentum.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Heavy photon search experiment at JLAB

The Heavy Photon Search (HPS) experiment in Hall-B at Jefferson Lab will search for new heavy vector boson(s), aka 'heavy photons', in the mass range of 20 MeV/c{sup 2} to 1000 MeV/c{sup 2} using the scattering of high energy, high intensity electron beams off a high Z target. The proposed measurements will cover the region of parameter space favored by the muon g-2 anomaly, and will explore a significant region of parameter space, not only at large couplings (α′/α > 10{sup −7}), but also in the regions of small couplings, down to α′/α∼10{sup −10}. The excellent vertexing capability of the Si-tracker uniquely enables HPS to cover the small coupling region. Also, HPS will search for heavy photons in an alternative to the e{sup +}e{sup −} decay mode, in the heavy photon's decay to μ{sup +}μ−.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

APEX: An electron fixed-target experiment to search for a new vector boson A′ Decaying to e{sup +}e{sup −}

The A' EXperiment (APEX) is designed to search for new vector bosons that have small couplings to charged particles. Such vectors can arise naturally from a small kinetic mixing of a new 'dark photon' (A') with the photon - one of the very few ways in which new forces can couple to the Standard Model - and have received considerable attention as an explanation of various dark matter related anomalies. A' bosons are produced by radiation off an electron beam, and could appear as narrow resonances with small production cross-section in the QED e{sup +}e{sup −} spectrum. We plan to search for an A' using the CEBAF electron beam at energies of 1-4 GeV incident on 0.5-10% radiation length multi-foil tungsten targets, and measure the resulting e{sup +}e{sup −} pairs using the High Resolution Spectrometers and a septum magnet in Hall A at Jefferson Lab. With a 33-day run, APEX will explore the region 50 MeV < m{sub A′} < 550 MeV with couplings alpha'/alpha down to 10{sup −7}. This proceeding summarizes the experiment, test run results, and comments on future plans.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Higgs gravitational interaction, weak boson scattering, and Higgs inflation in Jordan and Einstein frames

We study gravitational interaction of Higgs boson through the unique dimension-4 operator ξH{sup †}HR, with H the Higgs doublet and R the Ricci scalar curvature. We analyze the effect of this dimensionless nonminimal coupling ξ on weak gauge boson scattering in both Jordan and Einstein frames. We explicitly establish the longitudinal-Goldstone equivalence theorem with nonzero ξ coupling in both frames, and analyze the unitarity constraints. We study the ξ-induced weak boson scattering cross sections at O(1−30) TeV scales, and propose to probe the Higgs-gravity coupling via weak boson scattering experiments at the LHC (14 TeV) and the next generation pp colliders (50-100 TeV). We further extend our study to Higgs inflation, and quantitatively derive the perturbative unitarity bounds via coupled channel analysis, under large field background at the inflation scale. We analyze the unitarity constraints on the parameter space in both the conventional Higgs inflation and the improved models in light of the recent BICEP2 data.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

$W$ and $Z$ Boson Cross Section and $W$ Asymmetry at CMS

We report the measurement of the rates and asymmetries of inclusive and differential production of W and Z vector bosons in pp collisions at {radical}s = 7 TeV. The data consists of 36 pb{sup -1} collected in the Compact Muon Solenoid (CMS) detector at the Large Hadron Collider (LHC). The measured inclusive cross sections are {sigma}(pp {yields} WX) x B(W {yields} {ell}{nu}) = 10.31 {+-} 0.02(stat.){+-}0.09 (syst.){+-}0.10(th.){+-}0.41(lumi.) nb and {sigma}(pp {yields} ZX) x B(Z {yields} {ell}{ell}) = 0.975 {+-} 0.007(stat.){+-}0.007 (syst.){+-}0.018(th.){+-}0.039(lumi.) nb. The measured inclusive cross sections and also its ratio of W to Z or W{sup +} to W{sup -} agree with NNLO QCD cross section calculations and current parton distribution functions (PDFs). The differential production asymmetry of W boson as a function of the lepton pseudorapidity in the final state is also measured and compared with various PDFs.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2012

Search for the standard model Higgs boson in tau lepton final states

We present a search for the standard model Higgs boson in final states with an electron or muon and a hadronically decaying tau lepton in association with zero, one, or two or more jets using data corresponding to an integrated luminosity of up to 7.3 fb{sup -1} collected with the D0 detector at the Fermilab Tevatron collider. The analysis is sensitive to Higgs boson production via gluon gluon fusion, associated vector boson production, and vector boson fusion, and to Higgs boson decays to tau lepton pairs or W boson pairs. Observed (expected) limits are set on the ratio of 95% C.L. upper limits on the cross section times branching ratio, relative to those predicted by the Standard Model, of 14 (22) at a Higgs boson mass of 115 GeV and 7.7 (6.8) at 165 GeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Evidence for $WZ/WW\to \ell \nu$ + Heavy Flavors Vector Boson Production in 7.5 fb$^{-1}$ of CDF Data

This contribution describes a search for the associated production of Standard Model vector bosons WZ where the W boson decays leptonically (W {yields} {ell}{nu}) and the Z boson decays to a heavy flavor quark pair (Z {yields} b{bar b}, c{bar c}). At least one identified ('tagged') heavy flavor jet in the final state is required. Given the small di-jet invariant mass separation between the W and the Z resonances, the production of WW events where one W decays leptonically and the second W decays into an heavy flavor jet (e.i. W{sup + {yields} c{bar s}) contributes to our the signal. This search uses data collected with the CDF II detector at the Tevatron Collider at Fermilab, and corresponding to an integrated luminosity of approximately 7.5 fb{sup -1}. Events consistent with the signature of a charged lepton (electron or muon), large missing transverse energy and exactly two jets, of which at least one is required to contain a secondary vertex displaced from the jet origin, are selected. A multivariate discriminant based on the Support Vector Machine algorithm is used to reduce greatly the multi-jet background contamination. We observe a signal of significance of 3.03{sigma} over the background only hypothesis. A cross section of 1.085{sub -0.40}{sup +0.26} times the expected Standard Model value for the combined WZ/WW production and decay into heavy flavors is measured, consistent with the Standard Model prediction.

43 PARTICLE ACCELERATORS↗