Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 8 of 8
Full-Text Articles in Physics
Form Factors And Two-Photon Exchange In High-Energy Elastic Electron-Proton Scattering, M. E. Christy, T. Gautam, L. Ou, S.L. Allison, D. Bulumulla, F. Hauenstein, C. Hyde, K. Park, M.N.H. Rashad, J. Zhang, Y. X. Zhao, P. Zhu, Et Al.
Form Factors And Two-Photon Exchange In High-Energy Elastic Electron-Proton Scattering, M. E. Christy, T. Gautam, L. Ou, S.L. Allison, D. Bulumulla, F. Hauenstein, C. Hyde, K. Park, M.N.H. Rashad, J. Zhang, Y. X. Zhao, P. Zhu, Et Al.
Physics Faculty Publications
We present new precision measurements of the elastic electron-proton scattering cross section for momentum transfer (Q2) up to 15.75 (GeV/c)2. Combined with existing data, these provide an improved extraction of the proton magnetic form factor at high Q2 and double the range over which a longitudinal or transverse separation of the cross section can be performed. The difference between our results and polarization data agrees with that observed at lower Q2 and attributed to hard two-photon exchange (TPE) effects, extending to 8 (GeV/c)2 the range of Q2 for which a discrepancy …
Deeply Virtual Compton Scattering Cross Section At High Bjorken 𝓍B, F. Georges, M.N.H. Rashad, A. Stefanko, J. Zhang, Y. Zhao, P. Zhu, Et Al.
Deeply Virtual Compton Scattering Cross Section At High Bjorken 𝓍B, F. Georges, M.N.H. Rashad, A. Stefanko, J. Zhang, Y. Zhao, P. Zhu, Et Al.
Physics Faculty Publications
We report high-precision measurements of the deeply virtual Compton scattering (DVCS) cross section at high values of the Bjorken variable 𝓍B. DVCS is sensitive to the generalized parton distributions of the nucleon, which provide a three-dimensional description of its internal constituents. Using the exact analytic expression of the DVCS cross section for all possible polarization states of the initial and final electron and nucleon, and final state photon, we present the first experimental extraction of all four helicity-conserving Compton form factors (CFFs) of the nucleon as a function of 𝓍B, while systematically including helicity flip amplitudes. …
Deeply Learning Deep Inelastic Scattering Kinematics, Markus Diefenthaler, Abdullah Farhat, Andrii Verbytskyi, Yuesheng Xu
Deeply Learning Deep Inelastic Scattering Kinematics, Markus Diefenthaler, Abdullah Farhat, Andrii Verbytskyi, Yuesheng Xu
Mathematics & Statistics Faculty Publications
We study the use of deep learning techniques to reconstruct the kinematics of the neutral current deep inelastic scattering (DIS) process in electron–proton collisions. In particular, we use simulated data from the ZEUS experiment at the HERA accelerator facility, and train deep neural networks to reconstruct the kinematic variables Q2 and x. Our approach is based on the information used in the classical construction methods, the measurements of the scattered lepton, and the hadronic final state in the detector, but is enhanced through correlations and patterns revealed with the simulated data sets. We show that, with the appropriate selection …
Ruling Out Color Transparency In Quasielastic ¹²C(E,E'P) Up To Q² Of 14.2 (Gev/C)², D. Bhetuwal, J. Matter, H. Szumila-Vance, F. Hauenstein, C. Yero, J. Zhang, Et Al., Hall C. Collaboration
Ruling Out Color Transparency In Quasielastic ¹²C(E,E'P) Up To Q² Of 14.2 (Gev/C)², D. Bhetuwal, J. Matter, H. Szumila-Vance, F. Hauenstein, C. Yero, J. Zhang, Et Al., Hall C. Collaboration
Physics Faculty Publications
Quasielastic 12C(e,e'p) scattering was measured at spacelike 4-momentum transfer squared Q2 = 8, 9.4, 11.4, and 14.2 (GeV/c)2, the highest ever achieved to date. Nuclear transparency for this reaction was extracted by comparing the measured yield to that expected from a plane-wave impulse approximation calculation without any final state interactions. The measured transparency was consistent with no Q2 dependence, up to proton momenta of 8.5 GeV/c, ruling out the quantum chromodynamics effect of color transparency at the measured Q2 scales in exclusive (e, e'p) reactions. These results impose strict constraints on models of color …
Unpolarized Gluon Distribution In The Nucleon From Lattice Quantum Chromodynamics, Tanjib Khan, Raza Sabbir Sufian, Joseph Karpie, Christopher J. Monahan, Colin Egerer, Bálint Joó, Wayne Morris, Kostas Orginos, Anatoly Radyushkin, David G. Richards, Eloy Romero, Savvas Zafeiropoulos, On Behalf Of The Hadstruc Collaboration
Unpolarized Gluon Distribution In The Nucleon From Lattice Quantum Chromodynamics, Tanjib Khan, Raza Sabbir Sufian, Joseph Karpie, Christopher J. Monahan, Colin Egerer, Bálint Joó, Wayne Morris, Kostas Orginos, Anatoly Radyushkin, David G. Richards, Eloy Romero, Savvas Zafeiropoulos, On Behalf Of The Hadstruc Collaboration
Physics Faculty Publications
In this study, we present a determination of the unpolarized gluon Ioffe-time distribution in the nucleon from a first principles lattice quantum chromodynamics calculation. We carry out the lattice calculation on a 323 × 64 ensemble with a pion mass of 358 MeV and lattice spacing of 0.094 fm. We construct the nucleon interpolating fields using the distillation technique, flow the gauge fields using the gradient flow, and solve the summed generalized eigenvalue problem to determine the gluonic matrix elements. Combining these techniques allows us to provide a statistically well-controlled Ioffe-time distribution and unpolarized gluon parton distribution function. We …
Observation Of Beam Spin Asymmetries In The Process Ep → E'Π⁺Π⁻ X With Clas 12, T. B. Hayward, C. Dilks, A. Vossen, Dilini Bulumulla, Mohammad Hattawy, Florian Hauenstein, Mariana Khachatryan, Sebastian E. Kuhn, Yelena Prok, B. Yale, N. Zachariou, J. Zhang, Et Al., Clas Collaboration
Observation Of Beam Spin Asymmetries In The Process Ep → E'Π⁺Π⁻ X With Clas 12, T. B. Hayward, C. Dilks, A. Vossen, Dilini Bulumulla, Mohammad Hattawy, Florian Hauenstein, Mariana Khachatryan, Sebastian E. Kuhn, Yelena Prok, B. Yale, N. Zachariou, J. Zhang, Et Al., Clas Collaboration
Physics Faculty Publications
The observation of beam spin asymmetries in two-pion production in semi-inclusive deep inelastic scattering off an unpolarized proton target is reported. The data presented here were taken in the fall of 2018 with the CLAS12 spectrometer using a 10.6 GeV longitudinally spin-polarized electron beam delivered by CEBAF at JLab. The measured asymmetries provide the first opportunity to extract the parton distribution function e(x), which provides information about the interaction between gluons and quarks, in a collinear framework that offers cleaner access than previous measurements. The asymmetries also constitute the first ever signal sensitive to the helicity-dependent two-pion fragmentation function …
First Measurement Of Near-Threshold J/ᴪ Exclusive Photoproduction Off The Proton, M. Ali, M. Amaryan, E.G. Anassontzis, Q. Zhou, X. Zhou, B. Zihlmann, Gluex Collaboration
First Measurement Of Near-Threshold J/ᴪ Exclusive Photoproduction Off The Proton, M. Ali, M. Amaryan, E.G. Anassontzis, Q. Zhou, X. Zhou, B. Zihlmann, Gluex Collaboration
Physics Faculty Publications
We report on the measurement of the γp -> J/ψp cross section from Eγ = 11.8 GeV down to the threshold at 8.2 GeV using a tagged photon beam with the GlueX experiment. We find that the total cross section falls toward the threshold less steeply than expected from two-gluon exchange models. The differential cross section dσ/dt has an exponential slope of 1.67 ± 0.39 GeV-2 at 10.7 GeV average energy. The LHCb pentaquark candidates P+c can be produced in the s channel of this reaction. We see no evidence for them and set model-dependent upper …
Azimuthal Anisotropy In Cu+Au Collisions At √SNn = 200 Gev, L. Adamczyk, J. R. Adams, James K. Adkins, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, N. N. Ajitanand, I. Alekseev, D. M. Anderson, R. Aoyama, A. Aparin, D. Arkhipkin, E. C. Aschenauer, M. U. Ashraf, A. Attri, G. S. Averichev, X. Bai, V. Bairathi, K. Barish, A. Behera, R. Bellwied, A. Bhasin, A. K. Bhati, P. Bhattarai, J. Bielcik, J. Bielcikova, L. C. Bland, I. G. Bordyuzhin, J. Bouchet, J. D. Brandenburg, Renee H. Fatemi, Suvarna Ramachandran
Azimuthal Anisotropy In Cu+Au Collisions At √SNn = 200 Gev, L. Adamczyk, J. R. Adams, James K. Adkins, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, N. N. Ajitanand, I. Alekseev, D. M. Anderson, R. Aoyama, A. Aparin, D. Arkhipkin, E. C. Aschenauer, M. U. Ashraf, A. Attri, G. S. Averichev, X. Bai, V. Bairathi, K. Barish, A. Behera, R. Bellwied, A. Bhasin, A. K. Bhati, P. Bhattarai, J. Bielcik, J. Bielcikova, L. C. Bland, I. G. Bordyuzhin, J. Bouchet, J. D. Brandenburg, Renee H. Fatemi, Suvarna Ramachandran
Physics and Astronomy Faculty Publications
The azimuthal anisotropic flow of identified and unidentified charged particles has been systematically studied in Cu+Au collisions at √sNN = 200 GeV for harmonics n = 1–4 in the pseudorapidity range |η| < 1. The directed flow in Cu+Au collisions is compared with the rapidity-odd and, for the first time, the rapidity-even components of charged particle directed flow in Au+Au collisions at √sNN = 20 GeV. The slope of the directed flow pseudorapidity dependence in Cu+Au collisions is found to be similar to that in Au+Au collisions, with the intercept shifted toward positive pseudorapidity values, i.e., the Cu-going direction. The mean transverse momentum projected onto the spectator plane ⟨px⟩ in Cu+Au collision also exhibits approximately linear dependence on pseudorapidity with the intercept …