Physics Commons^™

Extraction Of The Neutron Electric Form Factor From Measurements Of Inclusive Double Spin Asymmetries, V. Sulkosky, G. Jin, E. Long, Y. -W. Zhang, M. Mihovilovic, A. Kelleher, B. Anderson, D. W. Higinbotham, S. Širca, K. Allada, J. R. M. Annand, T. Averett, W. Bertozzi, W. Boeglin, P. Bradshaw, A. Camsonne, M. Canan, G. D. Cates, C. Chen, J. -P. Chen, E. Chudakov, R. De Leo, X. Deng, A. Deur, C. Dutta, L. El Fassi, D. Flay, S. Frullani, F. Garibaldi, Wolfgang Korsch

Physics and Astronomy Faculty Publications

Background: Measurements of the neutron charge form factor, Gⁿ_E, are challenging because the neutron has no net charge. In addition, measurements of the neutron form factors must use nuclear targets which require accurately accounting for nuclear effects. Extracting Gⁿ_E with different targets and techniques provides an important test of our handling of these effects.

Purpose: The goal of the measurement was to use an inclusive asymmetry measurement technique to extract the neutron charge form factor at a four-momentum transfer of 1 (GeV/c)². This technique has very different systematic uncertainties …

Sea Quarks Contribution To The Nucleon Magnetic Moment And Charge Radius At The Physical Point, Raza Sabbir Sufian, Yi-Bo Yang, Jian Liang, Terrence Draper, Keh-Fei Liu

Physics and Astronomy Faculty Publications

We report a comprehensive analysis of the light and strange disconnected-sea quarks contribution to the nucleon magnetic moment, charge radius, and the electric and magnetic form factors. The lattice QCD calculation includes ensembles across several lattice volumes and lattice spacings with one of the ensembles at the physical pion mass. We adopt a model-independent extrapolation of the nucleon magnetic moment and the charge radius. We have performed a simultaneous chiral, infinite volume, and continuum extrapolation in a global fit to calculate results in the continuum limit. We find that the combined light and strange disconnected-sea quarks contribution to the nucleon …

First Exclusive Measurement Of Deeply Virtual Compton Scattering Off 4He: Toward The 3d Tomography Of Nuclei, M. Hattawy, N. A. Baltzell, R. Dupré, K. Hafidi, S. Stepanyan, S. Bültmann, R. De Vita, A. El Alaoui, L. El Fassi, H. Egiyan, F. X. Girod, M. Guidal, D. Jenkins, S. Liuti, Y. Perrin, B. Torayev, E. Voutier, K. P. Adhikari, S. Adhikari, D. Adikaram, Z. Akbar, M. J. Amaryan, S. Anefalos Pereira, Whitney R. Armstrong, H. Avakian, J. Ball, M. Bashkanov, M. Battaglieri, V. Batourine, I. Bedlinskiy, Wesley P. Gohn

Physics and Astronomy Faculty Publications

We report on the first measurement of the beam-spin asymmetry in the exclusive process of coherent deeply virtual Compton scattering off a nucleus. The experiment uses the 6 GeV electron beam from the Continuous Electron Beam Accelerator Facility (CEBAF) accelerator at Jefferson Lab incident on a pressurized ⁴He gaseous target placed in front of the CEBAF Large Acceptance Spectrometer (CLAS). The scattered electron is detected by CLAS and the photon by a dedicated electromagnetic calorimeter at forward angles. To ensure the exclusivity of the process, a specially designed radial time projection chamber is used to detect the recoiling ^{4 …}

Coherent Diffractive Photoproduction Of Ρ0 Mesons On Gold Nuclei At 200 Gev/Nucleon-Pair At The Relativistic Heavy Ion Collider, L. Adamczyk, 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, 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, A. V. Brandin, D. Brown, Renee H. Fatemi, Suvarna Ramachandran

Physics and Astronomy Faculty Publications

The STAR Collaboration reports on the photoproduction of π⁺π⁻ pairs in gold-gold collisions at a center-of-mass energy of 200 GeV/nucleon-pair. These pion pairs are produced when a nearly real photon emitted by one ion scatters from the other ion.

We fit the π⁺π⁻ invariant-mass spectrum with a combination of ρ⁰ and ω resonances and a direct π⁺π⁻ continuum. This is the first observation of the ω in ultraperipheral collisions, and the first measurement of ρ−ω interference at energies where photoproduction is dominated by Pomeron exchange. The ω amplitude is consistent …

Measurement Of Two-Photon Exchange Effect By Comparing Elastic E±P Cross Sections, P. Rimal, D. Adikaram, B. A. Raue, L. B. Weinstein, J. Arrington, W. K. Brooks, M. Ungaro, K. P. Adhikari, A. V. Afanasev, Z. Akbar, S. Anefalos Pereira, R. A. Badui, J. Ball, N. A. Baltzell, M. Battaglieri, V. Batourine, I. Bedlinskiy, A. S. Biselli, S. Boiarinov, W. J. Briscoe, S. Bültmann, V. D. Burkert, D. S. Carman, A. Celentano, T. Chetry, G. Ciullo, L. Clark, L. Colaneri, P. L. Cole, N. Compton, Wesley P. Gohn

Physics and Astronomy Faculty Publications

Background: The electromagnetic form factors of the proton measured by unpolarized and polarized electron scattering experiments show a significant disagreement that grows with the squared four-momentum transfer (Q²). Calculations have shown that the two measurements can be largely reconciled by accounting for the contributions of two-photon exchange (TPE). TPE effects are not typically included in the standard set of radiative corrections since theoretical calculations of the TPE effects are highly model dependent, and, until recently, no direct evidence of significant TPE effects has been observed.

Purpose: We measured the ratio of positron-proton to electron-proton elastic-scattering cross sections …

Factorization Breaking Of Adt For Polarized Deuteron Targets In A Relativistic Framework, Sabine Jeschonnek, J. W. Van Orden

Physics Faculty Publications

We discuss the possible factorization of the tensor asymmetry AdT measured for polarized deuteron targets within a relativistic framework. We define a reduced asymmetry and find that factorization holds only in plane wave impulse approximation and if p waves are neglected. Our numerical results show a strong factorization breaking once final state interactions are included. We also compare the d-wave content of the wave functions with the size of the factored, reduced asymmetry and find that there is no systematic relationship of this quantity to the d-wave probability of the various wave functions.

Strange Quark Magnetic Moment Of The Nucleon At The Physical Point, Raza Sabbir Sufian, Yi-Bo Yang, Andrei Alexandru, Terrence Draper, Jian Liang, Keh-Fei Liu

Physics and Astronomy Faculty Publications

We report a lattice QCD calculation of the strange quark contribution to the nucleon’s magnetic moment and charge radius. This analysis presents the first direct determination of strange electromagnetic form factors including at the physical pion mass. We perform a model-independent extraction of the strange magnetic moment and the strange charge radius from the electromagnetic form factors in the momentum transfer range of 0.051  GeV² ≲ Q² ≲ 1.31  GeV². The finite lattice spacing and finite volume corrections are included in a global fit with 24 valence quark masses on four lattices with different lattice spacings, …

Extraction Of The Nuetron Electric Form Factor From Measurements Of Inclusive Double Spin Asymmetries, V. Sulkosky, G. Jin, E. Long, Y.W. Zhang, M. Mihovilovic, A. Kelleher, B. Anderson, D. W. Higinbotham, S. Ŝirca, K. Allada, M. Canan

Physics Faculty Publications

Background: Measurements of the neutron charge form factor, Gⁿ_E , are challenging because the neutron has no net charge. In addition, measurements of the neutron form factors must use nuclear targets which require accurately accounting for nuclear effects. Extracting Gⁿ_E with different targets and techniques provides an important test of our handling of these effects.

Purpose: The goal of the measurement was to use an inclusive asymmetry measurement technique to extract the neutron charge form factor at a four-momentum transfer of 1(GeV/c)² . This technique has very different systematic uncertainties than traditional exclusive …

Coincidence Charged-Current Neutrino-Induced Deuteron Disintegration For 2H216O, J. W. Van Orden, T. W. Donnelly, O. Moreno

Physics Faculty Publications

Semi-inclusive charge-changing neutrino reactions on targets of heavy water are investigated with the goal of determining the relative contributions to the total cross section of deuterium and oxygen in kinematics chosen to emphasize the former. The study is undertaken for conditions where the typical neutrino beam energies are in the few GeV region, and hence relativistic modeling is essential. For this, the previous relativistic approach for the deuteron is employed, together with a spectral function approach for the case of oxygen. Upon optimizing the kinematics of the final-state particles assumed to be detected (typically a muon and a proton) it …

Measurement Of Two-Photon Exchange Effect By Comparing Elastic E ± P Cross Sections, D. Rimal, D. Adikaram, B. A. Raue, L. B. Weinstein, J. Arrington, W. K. Brooks, M. Ungaro, K. P. Adhikari, A. V. Afanasev, Z. Akbar

Physics Faculty Publications

Background: The electromagnetic form factors of the proton measured by unpolarized and polarized electron scattering experiments show a significant disagreement that grows with the squared four-momentum transfer (Q²) . Calculations have shown that the two measurements can be largely reconciled by accounting for the contributions of two-photon exchange (TPE). TPE effects are not typically included in the standard set of radiative corrections since theoretical calculations of the TPE effects are highly model dependent, and, until recently, no direct evidence of significant TPE effects has been observed.

Purpose: We measured the ratio of positron-proton to electron-proton elastic-scattering cross …