Physics Commons^™

Parton Distribution Functions From Ioffe Time Pseudodistributions From Lattice Calculations: Approaching The Physical Point, Bálint Joó, Joseph Karpie, Kostas Orginos, Anatoly V. Radyushkin, David G. Richards, Savvas Zafeiropoulos

Physics Faculty Publications

We present results for the unpolarized parton distribution function of the nucleon computed in lattice QCD at the physical pion mass. This is the first study of its kind employing the method of Ioffe time pseudodistributions. Beyond the reconstruction of the Bjorken-x dependence, we also extract the lowest moments of the distribution function using the small Ioffe time expansion of the Ioffe time pseudodistribution. We compare our findings with the pertinent phenomenological determinations.

Multi-Metallic Conduction Cooled Superconducting Radio-Frequency Cavity With High Thermal Stability, Gianluigi Ciovati, Gary Cheng, Uttar Pudasaini, Robert A. Rimmer

Physics Faculty Publications

Superconducting radio-frequency cavities are commonly used in modern particle accelerators for applied and fundamental research. Such cavities are typically made of high-purity, bulk Nb and with cooling by a liquid helium bath at a temperature of ∼2 K. The size, cost and complexity of operating a particle accelerator with a liquid helium refrigerator make the current cavity technology not favorable for use in industrial-type accelerators. We have developed a multi-metallic 1.495 GHz elliptical cavity conductively cooled by a cryocooler. The cavity has a ∼2 μm thick layer of Nb₃Sn on the inner surface, exposed to the rf field, …

Characterizing Plasma With Emission Tomography-Feasibility Study On Synthetic And Experimental Data, M. Nikolić, A. Samolov, A. Godunov, L. Vušković,, S. Popović

Physics Faculty Publications

We present a feasibility study on different tomographic algorithms to overcome the issues of finite sets of projection data, limited viewing angles, and noisy data, which cause the tomographic reconstruction to be an ill-posed inversion problem. We investigated three approaches: single angle Abel inversion, two angle approach, and multiple angle 2D plasma tomography. These methods were tested on symmetric and asymmetric sample functions and on experimental results from a supersonic flowing argon microwave plasma sustained in a cylindrical quartz cavity. The analysis focused on the afterglow region of the microwave flow where a plasmoid-like formation was observed. We investigated the …

Consistency Checks For Two-Body Finite-Volume Matrix Elements. Ii. Perturbative Systems, Raúl A. Briceño, Maxwell T. Hansen, Andrew W. Jackura

Physics Faculty Publications

Using the general formalism presented in [Phys. Rev. D 94, 013008 (2016); Phys. Rev. D 100, 034511 (2019)], we study the finite-volume effects for the 2 þ J → 2 matrix element of an external current coupled to a two-particle state of identical scalars with perturbative interactions. Working in a finite cubic volume with periodicity L, we derive a 1=L expansion of the matrix element through O(1=L⁵) and find that it is governed by two universal current-dependent parameters, the scalar charge and the threshold two particle form factor. We confirm the result through a numerical study of the …

The Clas12 Software Framework And Event Reconstruction, V. Ziegler, N. A. Baltzell, F. Bossù, D. S. Carman, P. Chatanon, M. Contalbrigo, J. Newton, M. Ungaro

Physics Faculty Publications

We describe offline event reconstruction for the CEBAF Large Acceptance Spectrometer at 12 GeV (CLAS12), including an overview of the offline reconstruction framework and software tools, a description of the algorithms developed for the individual detector subsystems, and the overall approach for charged and neutral particle identification. We also present the scheme for data processing and the code management procedures.

Heavy Quark Expansion For Heavy-Light Light-Cone Operators, Shuai Zhao

Physics Faculty Publications

We generalize the celebrated heavy quark expansion to nonlocal QCD operators. By taking nonlocal heavy-light current on the light-cone as an example, we confirm that the collinear singularities are common between QCD operator and the corresponding operator in heavy quark effective theory (HQET), at the leading power of 1/M expansion. Based on a perturbative calculation in operator form at one-loop level, a factorization formula linking QCD and HQET operators is investigated and the matching coefficient is determined. The matching between QCD and HQET light-cone distribution amplitudes (LCDAs) as well as other momentum distributions of hadron can be derived as …

Solutions For Fermi Questions, January 2020: Question 1: Car Flip; Question 2: A Mole Of People, Larry Weinstein

Physics Faculty Publications

At what speed will a car flip over when it slides side-ways into a curb? The angular momentum of the car will depend on its initial speed, the height of the curb, and the height of the center-of-mass (CM) of the car. If we approximate the car as having all its mass located at its CM, then its initial angular momentum relative to the top of the curb is. [Extracted from the article]

Probing The Deuteron At Very Large Internal Momenta, C. Yero, D. Abrams, Z Ahmed, F. Hauenstein, S.A. Wood, J. Zhang, Et Al., Hall C. Collaboration

Physics Faculty Publications

We measure ²H(e,e′p)n cross sections at 4-momentum transfers of Q² = 4.5 ± 0.5   (GeV/c)² over a range of neutron recoil momenta pr, reaching up to ∼1.0  GeV/c. We obtain data at fixed neutron recoil angles θ_nq = 35°, 45°, and 75° with respect to the 3-momentum transfer ^→q. The new data agree well with previous data, which reached p_r ∼ 500  MeV/c. At θ_nq = 35° and 45°, final state interactions, meson exchange currents, and isobar currents are suppressed and the plane wave impulse approximation provides the dominant cross section contribution. …

Flux Expulsion In Niobium Superconducting Radio-Frequency Cavities Of Different Purity And Essential Contributions To The Flux Sensitivity, P. Dhakal, Gianluigi Ciovati, Alex Gurevich

Physics Faculty Publications

Magnetic flux trapped during the cooldown of superconducting radio-frequency cavities through the transition temperature due to incomplete Meissner state is known to be a significant source of radio-frequency losses. The sensitivity of flux trapping depends on the distribution and the type of defects and impurities which pin vortices, as well as the cooldown dynamics when the cavity transitions from a normal to superconducting state. Here we present the results of measurements of the flux trapping sensitivity on 1.3 GHz elliptical cavities made from large-grain niobium with different purity for different cooldown dynamics and surface treatments. The results show that lower …

Probing Few-Body Nuclear Dynamics Via ³H And ³He (E E'P) Pn Cross-Section Measurements, R. Cruz-Torres, F. Hauenstein, D. Bulumulla, C. Hyde, M. Khachatryan, M.N.H. Rashad, L.B. Weinstein, Et. Al., Jefferson Lab Hall A. Tritium Collaboration

Physics Faculty Publications

We report the first measurement of the (e, e'p) three-body breakup reaction cross sections in helium-3 (³He) and tritium (³H) at large momentum transfer [< Q²> ≈ 1.9 (GeV/c)²] and x_B> 1 kinematics, where the cross section should be sensitive to quasielastic (QE) scattering from single nucleons. The data cover missing momenta 40 ≤ p_miss ≤ 500 MeV/c that, in the QE limit with no rescattering, equals the initial momentum of the probed nucleon. The measured cross sections are compared with state-of-the-art ab initio calculations. Overall …

Question 1: Coffee Consumption; Question 2: Active Volcanoes, Lawrence Weinstein

Physics Faculty Publications

This article presents questions related to Fermi which include how much coffee U.S. scientists consume daily, and how many active volcanoes there are in the world.

Extraction Of Beam-Spin Asymmetries From The Hard Exclusive Π⁺ Channel Off Protons In A Wide Range Of Kinematics, M.J. Amaryan, D. Bulumulla, M. Hattawy, M. Khachatryan, S.E. Kuhn, Z. W. Zhao, Et Al., The Clas Collaboration

Physics Faculty Publications

We have measured beam-spin asymmetries to extract the sinϕ moment A_LU^sinϕ from the hard exclusive e^→p → e'nπ⁺ reaction above the resonance region, for the first time with nearly full coverage from forward to backward angles in the center of mass. The A_LU^sinϕ moment has been measured up to 6.6  GeV² in -t, covering the kinematic regimes of generalized parton distributions (GPD) and baryon-to-meson transition distribution amplitudes (TDA) at the same time. The experimental results in very forward kinematics demonstrate the sensitivity to chiral-odd and chiral-even GPDs. In very backward kinematics where …

Improving Inverse Compton Sources By Avoiding Non-Linearities, B. Terzić, G. A. Krafft, V. Petrillo, I. Drebot, M. Ruijter

Physics Faculty Publications

We present a new, more nuanced understanding of non-linear effects in inverse Compton sources. Deleterious non-linear effects can arise even at low laser intensities, a regime previously viewed as linear. After laying out a survey of non-linear phenomena which degrade the effectiveness of inverse Compton sources, we discuss two powerful techniques designed to avoid these non-linearities. Starting with the known technique of non-linear longitudinal chirping of the laser pulse in the high laser field regime, we show that the simple stretching of the laser pulse, while keeping the energy constant, can significantly increase the spectral density of the scattered radiation …

Neutron Valence Structure From Nuclear Deep Inelastic Scattering, E. P. Segarra, A. Schmidt, T. Kutz, D. W. Higinbotham, E. Piasetzky, M. Strikman, L. B. Weinstein, O. Hen

Physics Faculty Publications

Mechanisms of spin-flavor SU(6) symmetry breaking in quantum chromodynamics (QCD) are studied via an extraction of the free neutron structure function from a global analysis of deep inelastic scattering (DIS) data on the proton and on nuclei from A = 2 (deuterium) to 208 (lead). Modification of the structure function of nucleons bound in atomic nuclei (known as the EMC effect) are consistently accounted for within the framework of a universal modification of nucleons in short-range correlated (SRC) pairs. Our extracted neutron-to-proton structure function ratio Fⁿ₂/F^p₂ becomes constant for x_B ≥ 0.6, equaling 0.47 …

Question 1: Car Flip; Question 2: A Mole Of People, Larry Weinstein

Physics Faculty Publications

Consider mass, area, power, and food requirements. For more Fermi questions and answers, see Guesstimation 2.0: Solving Today's Problems on the Back of a Napkin, by Lawrence Weinstein (Princeton University Press, 2012). [Extracted from artcle]

Question 1: Plowing Snow; Question 2: Wasted Food, Larry Weinstein

Physics Faculty Publications

[Extracted from the article] How much snow is shoveled or plowed in the U.S. in a typical winter? How much food is wasted at school cafeterias every year in the U.S.? For more Fermi questions and answers, see Guesstimation 2.0: Solving Today's Problems on the Back of a Napkin, by Lawrence Weinstein (Princeton University Press, 2012).

Optical-Depth Scaling Of Light Scattering From A Dense And Cold Atomic 87Rb Gas, K. J. Kemp, S. J. Roof, M. D. Havey, I. M. Sokolov, D. V. Kupriyanov, W. Guerin

Physics Faculty Publications

We report investigation of near-resonance light scattering from a cold and dense atomic gas of ⁸⁷Rb atoms. Measurements are made for probe frequencies tuned near the F=2→ F'=3 nearly closed hyperfine transition, with particular attention paid to the dependence of the scattered light intensity on detuning from resonance, the number of atoms in the sample, and atomic sample size. We find that, over a wide range of experimental variables, the optical depth of the atomic sample serves as an effective single scaling parameter which describes well all the experimental data.

Electron Tunneling And X-Ray Photoelectron Spectoscopy Studies Of The Superconductiong Properties Of Nitrogen-Doped Niobium Resonator Cavities, Eric M. Lechner, Basu Dev Oli, Junki Makita, Gianluigi Ciovati, Alex Gurevich, Maria Iavarone

Physics Faculty Publications

We use scanning tunneling microscopy (STM) and spectroscopy (STS), and x-ray photoelectron spectroscopy (XPS) to investigate the effect of nitrogen doping on the surface electronic and chemical structures of cutouts from superconducting Nb radio-frequency cavities. The goal of this work is to get insights into the fundamental physics and materials mechanisms behind the striking decrease of the surface resistance with the radio-frequency magnetic field, which has been observed on N-doped Nb cavities. Our XPS measurements reveal significantly more oxidized Nb 3d states and a thinner metallic suboxide layer on the N-doped Nb surfaces, which is also confirmed by tunneling spectroscopy …

Nonlinear Dynamics And Dissipation Of A Curvilinear Vortex Driven By A Strong Time-Dependent Meissner Current, W.P.M.R. Pathirana, A. Gurevich

Physics Faculty Publications

We report numerical simulations of large-amplitude oscillations of a trapped vortex line under a strong ac magnetic field H(t)=H sinωt parallel to the surface. The power dissipated by an oscillating vortex segment driven by the surface ac Meissner currents was calculated by taking into account the nonlinear vortex line tension, vortex mass, and a nonlinear Larkin-Ovchinnikov (LO) viscous drag coefficient η(v). We show that the LO decrease of η(v) with the vortex velocity v can radically change the field dependence of the surface resistance R_i(H) caused by trapped vortices. At low frequencies, …

Quasielastic Lepton Scattering And Back-To-Back Nucleons In The Short-Time Approximation, S. Pastore, J. Carlson, S. Gandolfi, R. Schiavilla, R. B. Wiringa

Physics Faculty Publications

Understanding quasielastic electron and neutrino scattering from nuclei has taken on new urgency with current and planned neutrino oscillation experiments, and with electron scattering experiments measuring specific final states, such as those involving nucleon pairs in "back-to-back" configurations. Accurate many-body methods are available for calculating the response of light (A <= 12) nuclei to electromagnetic and weak probes, but they are computationally intensive and only applicable to the inclusive response. In the present work we introduce a novel approach, based on realistic models of nuclear interactions and currents, to evaluate the short-time (high-energy) inclusive and exclusive response of nuclei. The approach accounts reliably for crucial two-nucleon dynamics, including correlations and currents, and provides information on back-to-back nucleons observed in electron and neutrino scattering experiments. We demonstrate that in the quasielastic regime and at moderate momentum transfers both initial- and final-state correlations and two-nucleon currents are important for a quantitatively successful description of the inclusive response and final-state nucleons. Finally, the approach can be extended to include relativistic-kinematical and dynamical-effects, at least approximately in the two-nucleon sector, and to describe the response in the resonance-excitation region.

B-Meson Light-Cone Distribution Amplitude From Euclidean Quantities, Wei Wang, Yu-Ming Wang, Ji Xu, Shuai Zhao

Physics Faculty Publications

A new method for the model-independent determination of the light-cone distribution amplitude of the B-meson in heavy quark effective theory (HQET) is proposed by combining the large momentum effective theory and the numerical simulation technique on the Euclidean lattice. We demonstrate the autonomous scale dependence of the nonlocal quasi-HQET operator with the aid of the auxiliary field approach, and further determine the perturbative matching coefficient entering the hard-collinear factorization formula for the B-meson quasidistribution amplitude at the one-loop accuracy. These results will be crucial to explore the partonic structure of heavy-quark hadrons in the static limit and to …

Collision Of Li2+ With Li(2s) And Li(2p): Differential And Total Ionization; Discrete Excitations; Elastic Scattering, And Total Cross Section, H.R.J. Walters, Colm T. Whelan

Physics Faculty Publications

The coupled pseudostate approximation (McGovern et al 2009 Phys. Rev. A 79 042707) has been applied to Li²⁺ + Li(2s, 2p_0,±₁) collisions at 16 MeV with emphasis on studying the fully differential ionization measurements of Ghanbari-Adivi et al in the azimuthal plane (2017 J. Phys. B: At. Mol. Opt. Phys. 50 215202). The states of the valence electron in the Li target are calculated using the model potential of Stein (1993 J. Phys. B: At. Mol. Opt. Phys. 26 2087). Altogether 164 states with angular momenta l = 0 to 9 are employed in …

Measurement Of The ³He Spin-Structure Functions And Of Neutron (³He) Spin-Dependent Sum Rules At 0 .035≤Q²≤0 .24 Gev², V. Sulkosky, D. Hayes, C. E. Hyde, P. E. Ulmer, X. Zheng, L. Zhu, Et Al., Jefferson Lab E97-110 Collaboration

Physics Faculty Publications

The spin-structure functions g₁ and g₂, and the spin-dependent partial cross-section σπ have been extracted from the polarized cross-sections differences,

Δσ∥ (ν, Q²) and Δσ⊥ (ν,Q²) measured for the 3^→He(^→e, e')X reaction, in the E97-110 experiment at Jefferson Lab. Polarized electrons with energies from 1.147 to 4.404GeV were scattered at angles of 6^◦and 9^◦ from a longitudinally or transversely polarized ³He target. The data cover the kinematic regions of the quasi-elastic, …

Generalized Contact Formalism Analysis Of The ⁴He(E,E′Pn) Reaction, J.R. Pybus, I. Korover, R. Weiss, A. Schmidt, N. Barnea, D.W. Higinbotham, E. Piasetzky, M. Strikman, L. B. Weinstein, O. Hen

Physics Faculty Publications

Measurements of short-range correlations in exclusive ⁴He (e , e ′ p N) reactions are analyzed using the Generalized Contact Formalism (GCF). We consider both instant-form and light-cone formulations with both the AV18 and local N2LO(1.0) nucleon-nucleon (NN) potentials. We find that kinematic distributions, such as the reconstructed pair opening angle, recoil neutron momentum distribution, and pair center of mass motion, as well as the measured missing energy, missing mass distributions, are all well reproduced by GCF calculations. The missing momentum dependence of the measured ⁴He (e , e ′ p N) /⁴He (e , e …

Gluon Pseudo-Distributions At Short Distances: Forward Case, Ian Balitsky, Wayne Morris, Anatoly Radyushkin

Physics Faculty Publications

We present the results that are necessary in the ongoing lattice calculations of the gluon parton distribution functions (PDFs) within the pseudo-PDF approach. We give a classification of possible two-gluon correlator functions and identify those that contain the invariant amplitude determining the gluon PDF in the light-cone z² → 0 limit. One-loop calculations have been performed in the coordinate representation and in an explicitly gauge-invariant form. We made an effort to separate ultraviolet (UV) and infrared (IR) sources of the ln⁡(−z²)-dependence at short distances z². The UV terms cancel in the reduced Ioffe-time distribution (ITD), …

Klf Analysis Report: Meson Spectroscopy Simulation Studies, Shankar Adhikari, Moskov Amaryan

Physics Faculty Publications

This analysis report is written as a supplemental for the strange meson spectroscopy part of the KLF proposal submitted to the JLab PAC48.

Developing A High Resolution Zdc For The Eic, J. H. Lee, T. Sako, K. Tanida, M. Murray, Q. Wang, N. Nickel, Y. Yamazaki, Y. Itow, H. Menjo, T. Shibata, C. E. Hyde, V. Baturin, Y. Goto, I. Nakagawa, R. Seidl, K. Kawade, A. Deshpande, B. Schmookler, K. Nakano, T. Chujo, Y. Miyachi

Physics Faculty Publications

The Electron Ion Collider offers the opportunity to make un-paralleled multidimen- sional measurements of the spin structure of the proton and nuclei, as well as a study of the onset of partonic saturation at small Bjorken-x [1]. An important requirement of the physics program is the tagging of spectator neutrons and the identification of forward photons. We propose to design and build a Zero Degree Calorimeter, or ZDC, to measure photons and neutrons with excellent energy & position resolution.

Results On Total And Elastic Cross Sections In Proton–Proton Collisions At √S = 200 Gev, J. Adam, L. Adamczyk, J. R. Adams, S. Bueltmann, Z. Zhu, M. Zyzak, Et Al., Star Collaboration

Physics Faculty Publications

We report results on the total and elastic cross sections in proton-proton collisions at √s = 200 GeV obtained with the Roman Pot setup of the STAR experiment at the Relativistic Heavy Ion Collider (RHIC). The elastic differential cross section was measured in the squared four-momentum transfer range 0.045 ≤ −t ≤ 0.135 GeV². The value of the exponential slope parameter B of the elastic differential cross section dσ/dt ∼ e^−Bt in the measured −t range was found to be B = 14.32 ± 0.09 (stat.)^+0.13_−0.28(syst.) GeV⁻². The total cross section σ_tot, obtained from …

Thermal Emittance And Lifetime Of Alkali-Antimonide Photocathodes Grown On Gaas And Molybdenum Substrates Evaluated In A -300 Kv Dc Photogun, Y. Wang, M. A. Mamun, P. Adderley, B. Bullard, J. Grames, J. Hansknecht, C. Hernandez-Garcia, G. A. Krafft, G. Palacios-Serrano, M. Poelker, M. L. Stutzman, R. Suleiman, M. Tiefenback, S. Wijethunga, J. Yoskowitz, S. Zhang

Physics Faculty Publications

Cs_xK_ySb photocathodes grown on GaAs and molybdenum substrates were evaluated using a –300 kV dc high voltage photogun and diagnostic beam line. Photocathodes grown on GaAs substrates, with varying antimony layer thickness (estimated range from < 20 nm to > 1 um), yielded similar thermal emittance per rms laser spot size values (~0.4 mm mrad / mm) but very different operating lifetime. Similar thermal emittance was obtained for a photocathode grown on a molybdenum substrate but with markedly improved lifetime. For this photocathode, no decay in quantum efficiency was measured at 4.5 mA average current and with peak current 0.55 A …

Superconductivity In La₂Ni₂In, Jannis Maiwald, Igor I. Mazin, Alex Gurevich, Meigan Aronson

Physics Faculty Publications

We report here the properties of single crystals of La₂Ni₂In. Electrical resistivity and specific heat measurements concur with the results of density functional theory calculations, finding that La₂Ni₂In is a weakly correlated metal, where the Ni magnetism is almost completely quenched, leaving only a weak Stoner enhancement of the density of states. Superconductivity is observed at temperatures below 0.9 K. A detailed analysis of the field and temperature dependencies of the resistivity, magnetic susceptibility, and specific heat at the lowest temperatures reveals that La₂Ni₂In is a dirty type-II …