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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 1,513 records · Page 84
All sourcesNASA NTRSDOE OSTI
DOE OSTI2012

High Multiplicity Searches at the LHC Using Jet Masses

This article introduces a new class of searches for physics beyond the Standard Model that improves the sensitivity to signals with high jet multiplicity. The proposed searches gain access to high multiplicity signals by reclustering events into large-radius, or 'fat', jets and by requiring that each event has multiple massive jets. This technique is applied to supersymmetric scenarios in which gluinos are pair-produced and then subsequently decay to final states with either moderate quantities of missing energy or final states without missing energy. In each of these scenarios, the use of jet mass improves the estimated reach in gluino mass by 20% to 50% over current LHC searches.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Correlated, precision measurements of θ 23 and δ using only the electron neutrino appearance experiments

Precision measurement of the leptonic CP violating phase δ will suffer from the, then surviving, large uncertainty of sin 2 θ 23 of 10–20% in the experimentally interesting region near maximal mixing of θ 23 . We advocate a new method for determination of both θ 23 and δ at the same time using only the ν e and ν̄ e appearance channels and show that sin 2 θ 23 can be determined automatically with much higher accuracy, approximately a factor of six, than sinδ. In this method, we identify a new degeneracy for the simultaneous determination of θ 23 and δ, the θ 23 intrinsic degeneracy, which must be resolved in order to achieve precision measurement of these two parameters. Spectral information around the vacuum oscillation maxima is shown to be the best way to resolve this degeneracy.

Minakata, Hisakazu↗
DOE OSTI2013

Search for microscopic black holes in a like-sign dimuon final state using large track multiplicity with the ATLAS detector

A search is presented for microscopic black holes in a like-sign dimuon final state in proton-proton collisions at $ \sqrt{s}$=8 TeV. The data were collected with the ATLAS detector at the Large Hadron Collider in 2012 and correspond to an integrated luminosity of 20.3 fb -1 . Using a high track multiplicity requirement, 0.6±0.2 background events from Standard Model processes are predicted and none observed. This result is interpreted in the context of low-scale gravity models and 95% C.L. lower limits on microscopic black hole masses are set for different model assumptions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Measurement of D 0 - D ¯ 0 mixing and search for indirect C P violation using D 0 → K S 0 π + π - decays

Here, we report a measurement of D 0 - D ¯ 0 mixing parameters and a search for indirect C P violation through a time-dependent amplitude analysis of D 0 → K S 0 π + π - decays. The results are based on 921 fb - 1 of data accumulated with the Belle detector at the KEKB asymmetric-energy e + e - collider. Assuming C P conservation, we measure the mixing parameters x = ( 0.56 ± 0.19 - 0.09 - 0.09 + 0.03 + 0.06 ) % and y = ( 0.30 ± 0.15 - 0.05 - 0.06 + 0.04 + 0.03 ) % , where the errors are statistical, experimental systematic, and systematic due to the amplitude model, respectively. Lastly, with C P violation allowed, the parameters | q / p | = 0.90 - 0.15 - 0.04 - 0.05 + 0.16 + 0.05 + 0.06 and arg ( q / p ) = ( - 6 ± 11 ± 3 - 4 + 3 ) ° are found to be consistent with conservation of C P symmetry in mixing and in the interference between mixing and decay, respectively.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Usefulness of effective field theory for boosted Higgs production

The Higgs + jet channel at the LHC is sensitive to the effects of new physics both in the total rate and in the transverse momentum distribution at high pT . We examine the production process using an effective field theory (EFT) language and discussing the possibility of determining the nature of the underlying high-scale physics from boosted Higgs production. The effects of heavy color triplet scalars and top partner fermions with TeV scale masses are considered as examples and Higgs-gluon couplings of dimension-5 and dimension-7 are included in the EFT. As a byproduct of our study, we examine the region of validity of the EFT. Dimension-7 contributions in realistic new physics models give effects in the high pT tail of the Higgs signal which are so tiny that they are likely to be unobservable.

HEPPH↗
DOE OSTI2016

Measurement of the correlation between the polar angles of leptons from top quark decays in the helicity basis at $\sqrt{s}$ = 7 TeV using the ATLAS detector

A measurement of the correlations between the polar angles of leptons from the decay of pair-produced t and $\bar{t}$ quarks in the helicity basis is reported, using proton-proton collision data collected by the ATLAS detector at the LHC. The dataset corresponds to an integrated luminosity of 4.6 fb$^{-1}$ at a center-of-mass energy of $\sqrt{s}$ = 7 TeV collected during 2011. Candidate events are selected in the dilepton topology with large missing transverse momentum and at least two jets. The angles θ$_1$ and θ$_2$ between the charged leptons and the direction of motion of the parent quarks in the $t\bar{t}$ rest frame are sensitive to the spin information, and the distribution of cosθ$_1$ ∙ cosθ$_2$ is sensitive to the spin correlation between the t and $\bar{t}$ quarks. The distribution is unfolded to parton level and compared to the next-to-leading order prediction. A good agreement is observed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Search for new phenomena in final states with an energetic jet and large missing transverse momentum in p p collisions at s = 13 TeV using the ATLAS detector

We report results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum. The search uses proton-proton collision data corresponding to an integrated luminosity of 3.2 fb $-$1 at $\sqrt{s}$ = 13 TeV collected in 2015 with the ATLAS detector at the Large Hadron Collider. Events are required to have at least one jet with a transverse momentum above 250 GeV and no leptons. Several signal regions are considered with increasing missing-transverse-momentum requirements between E$miss\atop{T}$ > 250 GeV and E$miss\atop{T}$ > 700 GeV . Good agreement is observed between the number of events in data and Standard Model predictions. The results are translated into exclusion limits in models with large extra spatial dimensions, pair production of weakly interacting dark-matter candidates, and the production of supersymmetric particles in several compressed scenarios.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Improving LHC searches for dark photons using lepton-jet substructure

Collider signals of dark photons are an exciting probe for new gauge forces and are characterized by events with boosted lepton jets. Existing techniques are efficient in searching for muonic lepton jets but due to substantial backgrounds have difficulty constraining lepton jets containing only electrons. This is unfortunate since upcoming intensity frontier experiments are sensitive to dark photon masses which only allow electron decays. Analyzing a recently proposed model of kinetic mixing, with new scalar particles decaying into dark photons, we find that existing techniques for electron jets can be substantially improved. We show that using lepton-jet-substructure variables, in association with a boosted decision tree, improves background rejection, significantly increasing the LHC’s reach for dark photons in this region of parameter space.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Signal of right-handed currents using B → K * ℓ + ℓ - observables at the kinematic endpoint

The decay mode B→K*ℓ + ℓ - is one of the most promising modes to probe physics beyond the standard model (SM), since the angular distribution of the decay products enable measurement of several constraining observables. LHCb has recently measured these observables using 3fb -1 of data as a binned function of q 2 , the dilepton invariant mass squared. We find that LHCb data implies evidence for right-handed currents, which are absent in the SM. These conclusions are derived in the maximum q 2 limit and are free from hadronic corrections. In conclusion, our approach differs from other approaches that probe new physics at low q 2 as it does not require estimates of hadronic parameters but relies instead on heavy quark symmetries that are reliable at the maximum q 2 kinematic endpoint.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Direct observation of the two-plasmon-decay common plasma wave using ultraviolet Thomson scattering

A 263-nm Thomson-scattering beam was used to directly probe two-plasmon-decay (TPD) excited electron plasma waves (EPWs) driven by between two and five 351-nm beams on the OMEGA Laser System. The amplitude of these waves was nearly independent of the number of drive beams at constant overlapped intensity, showing that the observed EPWs are common to the multiple beams. In an experimental configuration where the Thomson-scattering diagnostic was not wave matched to the common TPD EPWs, a broad spectrum of TPD-driven EPWs was observed, indicative of nonlinear effects associated with TPD saturation. Electron plasma waves corresponding to Langmuir decay of TPD EPWs were observed in both Thomson-scattering spectra, suggesting the Langmuir decay instability as a TPD saturation mechanism. Simulated Thomson-scattering spectra from three-dimensional numerical solutions of the extended Zakharov equations of TPD are in excellent agreement with the experimental spectra and verify the presence of the Langmuir decay instability.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗