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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 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Recent progress in basis light-front quantization

Basis Light-front Quantization (BLFQ) is a nonperturbative approach to quantum field theory. Here, in this paper, we report our recent progress in applying BLFQ to the positronium system in QED and to the meson and the baryon system in QCD. We present preliminary results on the mass spectrum, light-front wave functions and other observables of these systems, where one dynamical gauge boson is retained for the positronium and meson systems.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Comparison of HORACE and PHOTOS Algorithms for Multi-Photon Emission in the Context of the W Boson Mass Measurement

W boson mass measurement is sensitive to QED radiative corrections due to virtual photon loops and real photon emission. The largest shift in the measured mass, which depends on the transverse momentum spectrum of the charged lepton from the boson decay, is caused by the emission of real photons from the final-state lepton. There are a number of calculations and codes available to model the final-state photon emission. We perform a detailed study, comparing the results from HORACE and PHOTOS implementations of the final-state multiphoton emission in the context of a direct measurement ofW boson mass at Tevatron. Mass fits are performed using a simulation of the CDF II detector.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

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

CERN-LHC. Measurements of cross sections for final states containing a W boson and hadronic jets in proton-proton collisions at a centre-of-mass energy of 7 TeV. The data is from the full 2010 sample with a total integrated luminosity of 36 pb^{-1}. Cross sections are measured in both the electron and muon decay modes of the W and are presented as a function of inclusive jet multiplicity up to five jets. For each multiplicity, cross sections are determined as a function of (1) each jet PT, (2) the scalar sum (HT) of the PT of the charged lepton, missing PT and all jets, (3) the invariant mass of the jets and (4) rapidity distributions of various combinations of leptons and jets. The results are corrected for all detector effects and all known backgrounds. Comparative results are also shown for particle-level predicitions from ALPGEN, SHERPA and BLACKHAT-SHERPA. A separate link gives the Non-Perturbative and QED correction for each table.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Measurement of the production cross section for Z/gamma* in association with jets in p p collisions at s = 7 TeV with the ATLAS detector

CERN-LHC. Measurements of cross sections for Z0/GAMMA* production plus jets in proton-proton collisions at a centre-of-mass energy of 7 TeV. The analysis includes the full 2010 data set, collected at low rate of collisions, with a total integrated luminosity of 36 pb^{-1}. Data are presented for Jet PT>30 GeV and |y|<4.4 with cross sections in both the individual electron and muon decay modes of the Z0/GAMMA* as well as combined after correction to a common lepton fiducial region of |y|<2.5 and PT>20 GeV and for QED radiation effects.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Measurement of angular correlations in Drell-Yan lepton pairs to probe Z/gamma* boson transverse momentum at sqrt(s)=7 TeV with the ATLAS detector

CERN-LHC. Measurements of the PHI* distributions of di-electron and di-muon Drell-Yan pairs produced in proton-proton collisions at a centre-of-mass energy of 7 TeV. The data sample has an integrated luminosity of 4.6 fb-1. Normalised differential PHI* distributions are presented within the fiducial region of the leptons corrected to three levels, Born, dressed and bare, for QED FSR. The data are presented for di-electron and di-muons separately as well as combined, and also in three regions of rapidity as well as overall. For details of the variables see the text of the article. UPDATE (05 JAN 2015): corrected columns 2,3,4 of Tables 2,3,5,6 due to a bug fixed for bare and dressed cross sections in y-ranges; Table 4, value of the very last bin of the born dimuon, y>1.6, phi*=2.522-3.277 corrected (typo error).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Measurement of the forward-backward asymmetry of electron and muon pair-production in p p collisions at s = 7 TeV with the ATLAS detector

The Observable is calculated as a function of the di-lepton invariant mass. The forward backward asymmetry has been calculated at detector level and then corrected with an unfolding technique. Two corrections are applied: detector resolution and QED radiative corrections (namely mass bin migration), dilution. The results are presented for the cases when only the mass bin migration correction has been applied and when both the mass bin migration and dilution corrections have been applied.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Measurement of the inclusive cross-section for the production of jets in association with a Z boson in proton-proton collisions at 8 TeV using the ATLAS detector

The inclusive cross-section for jet production in association with a Z boson decaying into an electron-positron pair is measured as a function of the transverse momentum and the absolute rapidity of jets using 19.9 fb^-1 of sqrt(s) = 8 TeV proton-proton collision data collected with the ATLAS detector at the Large Hadron Collider. The measured Z + jets cross-section is unfolded to the particle level.The cross-section is compared with state-of-the-art Standard Model calculations, including the next-to-leading-order and next-to-next-to-leading-order perturbative QCD calculations, corrected for non-perturbative and QED radiation effects.The results of the measurements cover final-state jets with transverse momenta up to 1 TeV, and show good agreement with fixed-order calculations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Conformal boundary conditions for a 4d scalar field

We construct unitary, stable, and interacting conformal boundary conditions for a free massless scalar in four dimensions by coupling it to edge modes living on a boundary. The boundary theories we consider are bosonic and fermionic QED _3 3 with N_f N f flavors and a Chern-Simons term at level k k , in the large- N_f N f limit with fixed k/N_f k / N f . We find that interacting boundary conditions only exist when k≠ 0 k ≠ 0 . To obtain this result we compute the \beta β functions of the classically marginal couplings at the first non-vanishing order in the large- N_f N f expansion, and to all orders in k/N_f k / N f and in the couplings. To check vacuum stability we also compute the large- N_f N f effective potential. We compare our results with the the known conformal bootstrap bounds.

Di Pietro, Lorenzo (ORCID:0000000174965276)↗
DOE OSTI2021

Bogoliubov quasiparticles in superconducting qubits

Extending the qubit coherence times is a crucial task in building quantum information processing devices. In the three-dimensional cavity implementations of circuit QED, the coherence of superconducting qubits was improved dramatically due to cutting the losses associated with the photon emission. Next frontier in improving the coherence includes the mitigation of the adverse effects of superconducting quasiparticles. In these lectures, we review the basics of the quasiparticles dynamics, their interaction with the qubit degree of freedom, their contribution to the qubit relaxation rates, and approaches to control their effect.

Glazman, Leonid↗
DOE OSTI2022

The photon content of the proton in the CT18 global analysis

Recently, two photon PDF sets based on implementations of the LUX ansatz into the CT18 global analysis were released. In CT18lux, the photon PDF is calculated directly using the LUX master formula for all scales, \mu μ . In an alternative realization, CT18qed, the photon PDF is initialized at the starting scale, \mu_0 μ 0 , using the LUX formulation and evolved to higher scales \mu(>\mu_0) μ ( > μ 0 ) with a combined QED+QCD kernel at \mathcal{O}(\alpha),~\mathcal{O}(\alpha\alpha_s) 𝒪 ( α ) , 𝒪 ( α α s ) and \mathcal{O}(\alpha^2) 𝒪 ( α 2 ) . In the small- x x region, the photon PDF uncertainty is mainly induced by the quark and gluon PDFs, through the perturbative DIS structure functions. In comparison, the large- x x photon uncertainty comes from various low-energy, nonperturbative contributions, including variations of the inelastic structure functions in the resonance and continuum regions, higher-twist and target-mass corrections, and elastic electromagnetic form factors of the proton. We take the production of doubly-charged Higgs pairs, (H^{++}H^{--}) ( H + + H − − ) , as an example of scenarios beyond the Standard Model to illustrate the phenomenological implications of these photon PDFs at the LHC.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Nonperturbative analysis of field theories quantized on the light cone (Final Scientific Report for ER41087)

The primary focus of the work was the development of methods for the nonperturbative solution of quantum chromodynamics (QCD) in a form that yields wave functions for the eigenstates, from which hadronic properties can be computed. The principal approach was to use a light-front Hamiltonian formulation. In light-front coordinates, t+z/c plays the role of time, with t the ordinary time, z a space direction, and c the speed of light. This leads to a relativistic formulation that retains useful characteristics of nonrelativistic treatments. A bound state of many constituents can be represented by wave functions that define probabilities for each possible arrangement of internal momenta. These functions satisfy integral equations that can be approximated numerically to yield a matrix representation. The matrix problem can be solved by iterative methods. The approximate wave functions can then be used to compute properties of the bound state. Methods have been developed for model theories and gauge theories, including quantum electrodynamics and theories that are supersymmetric. The work has required the development of new numerical algorithms and computer codes for singular integral equations and eigenvalue problems. A key aspect of the work is the construction of practical procedures for nonperturbative regularization and renormalization. Two methods of regularization have been studied. One is the addition of heavy Pauli--Villars (PV) particles to the Lagrangian, with their metrics and couplings tuned to provide the necessary cancellations in the regularization. The other method of regularization is the addition of supersymmetric partners, to extend a theory to a supersymmetric form. The supersymmetric theories were solved by the supersymmetric discrete light-cone quantization (SDLCQ) method. The most significant accomplishments of the project were the SDLCQ calculation of direct evidence for a Maldacena duality conjecture, construction of a practical light-front quantization for QED in an arbitrary covariant gauge, and invention of the light-front coupled-cluster method, designed to eliminate the need for Fock-space truncations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Non-Equilibrium Dynamics of Many-Body Quantum Systems: Fundamentals and New Frontiers

Rapid progress in nanotechnology and naofabrication techniques has ushered in a new era of quantum transport experiments. This has in turn heightened the interest in theoretical understanding of nonequilibrium dynamics of strongly correlated quantum systems. This project has advanced the frontiers of understanding in this area along several fronts. For example, we showed that under certain conditions, quantum impurities out of equilibrium can be reformulated in terms of an effective equilibrium theory; this makes it possible to use the gamut of tools available for quantum systems in equilibrium. On a different front, we demonstrated that the elastic power of a transmitted microwave photon in circuit QED systems can exhibit a many-body Kondo resonance. We also showed that under many circumstances, bipartite fluctuations of particle number provide an effective tool for studying many-body physics—particularly the entanglement properties of a many-body system. This implies that it should be possible to measure many-body entanglement in relatively simple and tractable quantum systems. In addition, we studied charge relaxation in quantum RC circuits with a large number of conducting channels, and elucidated its relation to Kondo models in various regimes. We also extended our earlier work on the dynamics of driven and dissipative quantum spin-boson impurity systems, deriving a new formalism that makes it possible to compute the full spin density matrix and spin-spin correlation functions beyond the weak coupling limit. Finally, we provided a comprehensive analysis of the nonequilibrium transport near a quantum phase transition in the case of a spinless dissipative resonant-level model. This project supported the research of two Ph.D. students and two postdoctoral researchers, whose training will allow them to further advance the field in coming years.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Precision Studies of Hadronic and Electro-Weak Interactions for Collider Physics (Final Report)

This project was directed toward developing precision computational tools for proton collisions at the Large Hadron Collider, focusing primarily on electroweak boson production and electroweak radiative corrections. The programs developed under this project carried the name HERWIRI, for High Energy Radiation With Infra-Red Improvements, and are the first steps in an ongoing program to develop a set of hadronic event generators based on combined QCD and QED exponentiation. HERWIRI1 applied these improvements to the hadronic shower, while HERWIRI2 will apply the electroweak corrections from the program KKMC developed for electron-positron scattering to a hadronic event generator, including exponentiated initial and final state radiation together with first-order electroweak corrections to the hard process. Some progress was also made on developing differential reduction techniques for hypergeometric functions, for application to the computation of Feynman diagrams.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Observation of Central Exclusive Diphoton Production at the Tevatron

We have observed exclusive γγ production in proton-antiproton collisions at the Tevatron at √ s = 1.96 TeV. We use data corresponding to 1.11 ± 0.07 fb-1 integrated luminosity taken by the Run II Collider Detector at Fermilab, with a trigger requiring two electromagnetic showers, each with transverse energy ET > 2 GeV, and vetoing on hits in the forward beam shower counters. We select events with two electromagnetic showers, each with transverse energy ET > 2.5 GeV and pseudorapidity |η| < 1.0, with no other particles detected in -7.4 < η < +7.4. The two showers have similar ET and an azimuthal angle separation Δφ ~ π; we find 34 events with exactly two matching charged particle tracks, agreeing with expectations for the QED process p¯p → p+e+e- + ¯p by two photon exchange; and we find 43 events with no tracks. The latter are candidates for the exclusive process p¯p → p + γγ + ¯p by double pomeron exchange. We use the strip and wire chambers at the longitudinal shower maximum position within the calorimeter to measure a possible exclusive background from IP + IP → π0π0, and conclude that it is consistent with zero and is < 15 events at 95% C.L. The measured cross section is σγγ,excl(|η| < 1, ET (γ) > 2.5 GeV) = 2.48 +0.40 -0.35(stat) +0.40 -0.51(syst) pb and in agreement with the theoretical predictions. This process is closely related to exclusive Higgs boson production pp → p + H + p at the Large Hadron Collider. The observation of the exclusive production of diphotons shows that exclusive Higgs production can happen and could be observed with a proper experimental setup.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Pythia Jet Finding Study with Trento Backgrounds

We present results applying the Pythia SlowJet Finder to Pythia generated QCD and QED hard processes in the presence of simulated heavy ion backgrounds. The hard process events are generated with Pythia version 8.219 for √s NN =200 GeV proton-proton collisions and the backgrounds are generated by the Reduced Thickness Event-by-event Nuclear Topology model T R ENTo for Au-Au collisions with a nucleon-nucleon cross-section of 4.23 fm 2 . The T R ENTo model is used to calculate the initial entropy and ellipticity from which the total charged particle multiplicity and elliptic ow are determined. We report results in the form of event displays, total p T distributions, and fragmentation distributions for SlowJet applied to Pythia events with and without the simulated heavy ion backgrounds.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Search for New Physics in Top Quark Production and Upgrade of the CMS Hadron Calorimeter

Our goal is to measure precisely the properties of the heaviest subatomic particle ever discovered, the top quark. In the proton-proton collisions at the LHC, top quarks are produced copiously. The largest set of top quarks recorded by the CMS detector make it an ideal laboratory to measure properties such as its mass and the rate at which pair of top quarks are produced in association with energetic photons. Quantum electrodynamics, or QED, describes the emission of light by charged particles and is the most precise physics theory ever devised. Typically this means light emitted by electrons, but any charged particles will do, such as the top quark. Studies of the light-emitting properties of top quarks help us to refine our current theoretical predictions at the finest level, and provide additional tools to study in more detail the recently discovered Higgs boson particle. However, during this process, the studies may reveal interesting features not yet observed. Deviations from the standard predictions would be a strong sign of something entirely new. These new physics theories are motivated to answer the current big mysteries in the universe such as what is the nature of mass or what is dark matter. As the LHC increases the collision energy and its luminosity, the detectors need to be improved to cope with these high-luminosity scenarios. New sensors will be installed in the hadron calorimeter detectors along with new front and end electronics at the end of 2016. We are testing and calibrating the new front-end readout electronics that will allow us to have more options to reduce the noise on these detectors. In order to do this calibration, we have developed a system that can inject electric charge in the full range of the charge integrator chip, the QIE ASICs.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Semi-classical Electrodynamics: A Short Note

I have previously claimed the key to understanding the numerical value of the fine structure constant is near-field corrections which terminate integrals at low virtual photon energies, thus obverting an infrared divergence common to many QED calculations. I have since switched to a physics-based calculation of the near-field corrections, instead of the previously used educated guess. The relevant equations are presented here.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Possible reason for the numerical value of the fine-structure constant

A simple picture of the electron emerges if there is a cross section of πλ 2 for vacuum virtual photons to stimulate an isolated electron to emit an additional virtual photon. This reaction mechanism leads to the storage of the rest-mass energy in the surrounding cloud of virtual photons. The Lamb shift can be obtained if one out of every 1/α of the stimulated emissions is preceded by the absorption and re-emission of the incident vacuum virtual photon including the corresponding electron recoil. This suggests a “doorway” cross section of απλ 2 plays a key role in some QED processes. Additional support for this suggestion is obtained via a simple semi-classical picture of Compton scattering. Several speculative semi-classical reaction mechanism choices, including near-field effects, give the anomalous magnetic moment of the free electron. These choices are partially justified by their ability to give the magnetic moment of electrons in hydrogen-like atoms as a function of the atomic number of the corresponding nucleus, close to the correct result. The stimulated-emission process used to obtain the rest-mass energy allows for the possibility that stimulated virtual photons can be exchanged between an electron pair. This exchange can be used to estimate a repulsive force between electrons, and thus allows for a calculation of the fine-structure constant. A result near to the experimental value is obtained with minor modifications to the assumptions that give the rest mass, Lamb shift, and anomalous magnetic moment of the electron. Additional studies are required to confirm or negate the suggestions made here.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗