Physics Commons^™

Laser Pulsing In Linear Compton Scattering, G. A. Krafft, E. Johnson, K. Deitrick, B. Terzić, R. Kelmar, T. Hodges, J. R. Delayen

Physics Faculty Publications

Previous work on calculating energy spectra from Compton scattering events has either neglected considering the pulsed structure of the incident laser beam, or has calculated these effects in an approximate way subject to criticism. In this paper, this problem has been reconsidered within a linear plane wave model for the incident laser beam. By performing the proper Lorentz transformation of the Klein-Nishina scattering cross section, a spectrum calculation can be created which allows the electron beam energy spread and emittance effects on the spectrum to be accurately calculated, essentially by summing over the emission of each individual electron. Such an …

Measurements Of Dⁿ² And Aⁿ¹: Probing The Neutron Spin Structure, D. Flay, M. Posik, D. S. Parno, K. Allada, M. Canan, C. Hyde, Jefferson Lab Hall A Collaboration

Physics Faculty Publications

We report on the results of the E06-014 experiment performed at Jefferson Lab in Hall A, where a precision measurement of the twist-3 matrix element d₂ of the neutron dⁿ₂ was conducted. The quantity dⁿ₂ represents the average color Lorentz force a struck quark experiences in a deep inelastic electron scattering event off a neutron due to its interaction with the hadronizing remnants. This color force was determined from a linear combination of the third moments of the ³He spin structure functions, g₁ and g₂, after nuclear corrections had been applied to these …

Photoproduction Of Λ And Σº Hyperons Using Linearly Polarized Photons, C. A. Paterson, D. G. Ireland, K. Livingston, B. Mckinnon, D. Adikaram, M. Amaryan, Y. Prok, B. Torayev

Physics Faculty Publications

Background: Measurements of polarization observables for the reactions ^→ᵧp→K+ Λ and ^→ᵧp→ K+Σ⁰ have been performed. This is part of a program of measurements designed to study the spectrum of baryon resonances in particular, and nonperturbative QCD in general.

Purpose: The accurate measurement of several polarization observables provides tight constraints for phenomenological fits, which allow the study of strangeness in nucleon and nuclear systems. Beam-recoil observables for the ^→ᵧp→ K+Σ⁰ reaction have not been reported before now.

Method: Themeasurements were carried out using linearly polarized photon beams incident on a liquid hydrogen target, and the …

Target And Beam Target Spin Asymmetries In Exclusive Π+ And Π- Electroproduction With 1.6 To 5.7 Gev Electrons, P. E. Bosted, S. Careccia, G. Dodge, S. E. Kuhn, Y. Prok, M. J. Amaryan, B. Torayev, L. B. Weinstein, Z. W. Zhao, Clas Collaboration

Physics Faculty Publications

Beam-target double-spin asymmetries and target single-spin asymmetries in exclusive π⁺ and quasiexclusive π^- electroproduction were obtained from scattering of 1.6- to 5.7-GeV longitudinally polarized electrons from longitudinally polarized protons (for π⁺) and deuterons (for π^-) using the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab. The kinematic range covered is 1.1 < W < 2.6 GeV and 0.05 < Q² < 5 GeV², with good angular coverage in the forward hemisphere. The asymmetry results were divided into approximately 40 000 kinematic bins for π⁺ from free protons and 15 000 bins for π^- production from bound nucleons in the deuteron. The …

Gluon Tmd In Particle Production From Low To Moderate X, I. Balitsky, A. Tarasov

Physics Faculty Publications

We study the rapidity evolution of gluon transverse momentum dependent distributions appearing in processes of particle production and show how this evolution changes from small to moderate Bjorken x.

Measurement Of Target And Double-Spin Asymmetries For The Ep → Eπ+(N) Reaction In The Nucleon Resonance Region At Low Q², Clas Collaboration, K. P. Adhikari, S E. Kuhn, D. Adikaram, M. J. Amaryan, S. Bültmann, Gail Dodge, N. Guler, L. B. Weinstein

Physics Faculty Publications

We report measurements of target- and double-spin asymmetries for the exclusive channel ^→e^→p → eπ⁺(n) in the nucleon resonance region at Jefferson Lab using the CEBAF Large Acceptance Spectrometer (CLAS). These asymmetries were extracted from data obtained using a longitudinally polarized NH₃ target and a longitudinally polarized electron beam with energies 1.1, 1.3, 2.0, 2.3, and 3.0 GeV. The new results are consistent with previous CLAS publications but are extended to a low Q² range from 0.0065 to 0.35(GeV/c)². The Q² access was made possible by a custom-built Cherenkov detector …

Iterative Monte Carlo Analysis Of Spin-Dependent Parton Distributions, Nobuo Sato, W. Melnitchouk, S. E. Kuhn, J. J. Ethier, A. Accardi, Jefferson Lab Angular Momentum Collaboration

Physics Faculty Publications

We present a comprehensive new global QCD analysis of polarized inclusive deep-inelastic scattering, including the latest high-precision data on longitudinal and transverse polarization asymmetries from Jefferson Lab and elsewhere. The analysis is performed using a new iterative Monte Carlo fitting technique which generates stable fits to polarized parton distribution functions (PDFs) with statistically rigorous uncertainties. Inclusion of the Jefferson Lab data leads to a reduction in the PDF errors for the valence and sea quarks, as well as in the gluon polarization uncertainty at x ≳ 0.1 . The study also provides the first determination of the flavor-separated twist-3 PDFs …

First Results Of Magnetic Field Penetration Measurements Of Multilayer Sis Structures, O. B. Malyshev, L. Gurran, R. Valizadeh, S. Pattalwar, N. Pattalwar, K. D. Dumbell, A. Gurevich

Physics Faculty Publications

The performance of superconducting RF cavities made of bulk Nb is limited by a breakdown field of B_p ≈200 mT, close to the superheating field for Nb. A potentially promising solution to enhance the breakdown field of the SRF cavities beyond the intrinsic limits of Nb is a multilayer coating suggested in [1]. In the simplest case, such a multilayer may be a superconductor-insulator-superconductor (S-I-S) coating, for example, bulk niobium (S) coated with a thin film of insulator (I) followed by a thin layer of another superconductor (S) which could be e.g. dirty niobium [2]. Here we report the …

High-Fidelity Simulations Of Long-Term Beam-Beam Dynamics On Gpus, B. Terzić, K. Arumugam, M. Aturban, C. Cotnoir, A. Godunov, D. Ranjan, M. Stefani, M. Zubair, F. Lin, V. Morozov, Y. Roblin, H. Zhang

Physics Faculty Publications

Future machines such as the Electron Ion Collider (MEIC), linac-ring machines (eRHIC) or LHeC are particularly sensitive to beam-beam effects. This is the limiting factor for long-term stability and high luminosity reach. The complexity of the non-linear dynamics makes it challenging to perform such simulations typically requiring millions of turns. Until recently, most of the methods have involved using linear approximations and/or tracking for a limited number of turns. We have developed a framework which exploits a massively parallel Graphical Processing Units (GPU) architecture to allow for tracking millions of turns in a sympletic way up to an arbitrary order. …

Rapidity Factorization And Evolution Of Gluon Tmds, Ian Balitsky

Physics Faculty Publications

I discuss how the rapidity evolution of gluon transverse momentum dependent distribution changes from nonlinear evolution at small x « 1 to linear evolution at moderate x ∼ 1.

Relativistic, Model-Independent, Multichannel 2 → 2 Transition Amplitudes In A Finite Volume, Raúl A. Briceño, Maxwell T. Hansen

Physics Faculty Publications

We derive formalism for determining 2+𝓙 → 2 infinite-volume transition amplitudes from finite-volume matrix elements. Specifically, we present a relativistic, model-independent relation between finite-volume matrix elements of external currents and the physically observable infinite-volume matrix elements involving two-particle asymptotic states. The result presented holds for states composed of two scalar bosons. These can be identical or nonidentical and, in the latter case, can be either degenerate or nondegenerate. We further accommodate any number of strongly coupled two-scalar channels. This formalism will, for example, allow future lattice QCD calculations of the ρ-meson form factor, in which the unstable nature of …

Water Vapour Variability In The High-Latitude Upper Troposphere- Part 2: Impact Of Volcanic Eruptions, Christopher E. Sioris, Jason Zou, C. Thomas Mcelroy, Chris D. Boone, Patrick E. Sheese, Peter F. Bernath

Chemistry & Biochemistry Faculty Publications

The impact of volcanic eruptions on water vapour in the high-latitude upper troposphere is studied using deseasonalized time series based on observations by the Atmospheric Chemistry Experiment (ACE) water vapour sensors, namely MAESTRO (Measurements of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation) and the Fourier Transform Spectrometer (ACE-FTS). The two eruptions with the greatest impact on the high-latitude upper troposphere during the time frame of this satellitebased remote sensing mission are chosen. The Puyehue-Cordón Caulle volcanic eruption in June 2011 was the most explosive in the past 24 years and is shown to be able to account …

Comparison Between Electropositive And Electronegative Cold Atmospheric-Pressure Plasmas: A Modelling Study, Ding X. Liu, Jia F. Li, Ai J. Yang, Xiao H. Wang, Ming Z. Rong, Michael G. Kong

Bioelectrics Publications

Cold atmospheric-pressure He + N₂ and He + O₂ plasmas are chosen as the representatives for electropositive and electronegative plasmas, of which the discharge characteristics are studied and then compared to each other by fluid models. As the increase of the impurity (N₂ or O₂) fraction from 0 to 10%, for He + N₂ plasmas the electron density and ion density increase, the spatiotemporal distributions of electron density, ion density, electron temperature and electron generation rate change a little. On contrast, for He + O₂ plasmas the electron density decreases, the ion density …