Physical Sciences and Mathematics | Open Access Articles

First Observation Of P-Odd Γ Asymmetry In Polarized Neutron Capture On Hydrogen, D. Blyth, J. Fry, N. Fomin, R. Alarcon, L. Alonzi, E. Askanazi, S. Baeßler, S. Balascuta, L. Barrón-Palos, A. Barzilov, J. D. Bowman, N. Birge, J. R. Calarco, T. E. Chupp, V. Cianciolo, C. E. Coppola, Chrisopher B. Crawford, K. Craycraft, D. Evans, C. Fieseler, E. Frlež, I. Garishvili, M. T. W. Gericke, R. C. Gillis, K. B. Grammer, G. L. Greene, J. Hall, J. Hamblen, C. Hayes, E. B. Iverson, Md Latiful Kabir, Mark Mccrea, R. Milburn, F. Simmons, Aaron P. Sprow, E. Tang

Physics and Astronomy Faculty Publications

We report the first observation of the parity-violating gamma-ray asymmetry A^np_γ in neutron-proton capture using polarized cold neutrons incident on a liquid parahydrogen target at the Spallation Neutron Source at Oak Ridge National Laboratory. A^np_γ isolates the ΔI = 1, ³S₁ → ³P₁ component of the weak nucleon-nucleon interaction, which is dominated by pion exchange and can be directly related to a single coupling constant in either the DDH meson exchange model or pionless effective field theory. We measured A^np_γ = [−3.0 ± 1.4(stat )± 0.2(syst)] × 10^{−8 …}

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Measurement Of Unpolarized And Polarized Cross Sections For Deeply Virtual Compton Scattering On The Proton At Jefferson Laboratory With Clas, N. Hirlinger Saylor, B. Guegan, V. D. Burkert, L. Elouadrhiri, M. Garçon, F. X. Girod, M. Guidal, H. S. Jo, V. Kubarovsky, S. Niccolai, P. Stoler, K. P. Adhikari, S. Adhikari, Z. Akbar, M. J. Amaryan, S. Anefalos Pereira, J. Ball, I. Balossino, N. A. Baltzell, L. Barion, M. Battaglieri, V. Batourine, I. Bedlinskiy, A. S. Biselli, S. Boiarinov, W. J. Briscoe, W. K. Brooks, S. Bültmann, F. Cao, S. Carman, Wesley P. Gohn

Physics and Astronomy Faculty Publications

This paper reports the measurement of polarized and unpolarized cross sections for the ep → e′ p′ γ reaction, which is composed of deeply virtual Compton scattering (DVCS) and Bethe-Heitler (BH) processes, at an electron beam energy of 5.88 GeV at the Thomas Jefferson National Accelerator Facility using the Large Acceptance Spectrometer CLAS. The unpolarized cross sections and polarized cross section differences have been measured over broad kinematics, 0.10 < x_B < 0.58, 1.0 < Q² < 4.8GeV², and 0.09 < −t < 2.00GeV². The results are found to be consistent with previous CLAS data, and these new data are discussed in …

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Exclusive Photoproduction Of Π0 Up To Large Values Of Mandlestam Variables S, T, And U With Clas, M. C. Kunkel, M. J. Amaryan, I. I. Strakovsky, J. Ritman, G. R. Goldstein, K. P. Adhikari, S. Adhikari, H. Avakian, J. Ball, I. Balossino, L. Barion, M. Battaglieri, V. Batourine, I. Bedlinskiy, A. S. Biselli, S. Boiarinov, W. J. Briscoe, W. K. Brooks, S. Bültmann, V. D. Burkert, F. Cao, D. S. Carman, A. Celentano, G. Charles, T. Chetry, G. Ciullo, L. Clark, P. L. Cole, M. Contalbrigo, O. Cortes, Wesley P. Gohn

Physics and Astronomy Faculty Publications

Exclusive photoproduction cross sections have been measured for the process γp → pπ⁰[e⁺e⁻(γ)] with the Dalitz decay final state using tagged photon energies in the range of E_γ = 1.275–5.425 GeV. The complete angular distribution of the final state π⁰, for the entire photon energy range up to large values of t and u, has been measured for the first time. The data obtained show that the cross section dσ/dt, at mid to large angles, decreases with energy as s^{−6.89±0.26}. This is …

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Measurement Of The 3ΛH Lifetime In Au+Au Collisions At The Bnl Relativistic Heavy Ion Collider, L. Adamczyk, J. R. Adams, James K. Adkins, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, N. N. Ajitanand, I. Alekseev, J. Alford, 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, Renee H. Fatemi, Suvarna Ramachandran

Physics and Astronomy Faculty Publications

An improved measurement of the ³_ΛH lifetime is presented. In this paper, the mesonic decay modes ³_ΛH → ³He + π⁻ and ³_ΛH → d + p + π⁻ are used to reconstruct the ³_ΛH from Au+Au collision data collected by the STAR collaboration at Relativistic Heavy Ion Collider (RHIC). A minimum χ² estimation is used to determine the lifetime of τ = 142⁺²⁴₋₂₁(stat.) ± 29(syst.) ps. This lifetime is about 50% shorter than the lifetime τ = 263 ± 2 ps of a free …

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Phenomenology Of Neutron-Antineutron Conversion, Susan Gardner, Xinshuai Yan

Physics and Astronomy Faculty Publications

We consider the possibility of neutron-antineutron (n−n¯) conversion, in which the change of a neutron into an antineutron is mediated by an external source, as can occur in a scattering process. We develop the connections between n−n¯ conversion and n−n¯ oscillation, in which a neutron spontaneously transforms into an antineutron, noting that if n−n¯ oscillation occurs in a theory with baryon number minus lepton number (B-L) violation, then n−n¯ conversion can occur also. We show how an experimental limit on n−n¯ …

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Azimuthal Transverse Single-Spin Asymmetries Of Inclusive Jets And Charged Pions Within Jets From Polarized-Proton Collisions At √S = 500 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

We report the first measurements of transverse single-spin asymmetries for inclusive jet and jet + π^± production at midrapidity from transversely polarized proton-proton collisions at √s = 500 GeV. The data were collected in 2011 with the STAR detector sampled from 23 pb⁻¹ integrated luminosity with an average beam polarization of 53%. Asymmetries are reported for jets with transverse momenta 6 < p_T < 55 GeV/c and pseudorapidity |η| < 1. Presented are measurements of the inclusive-jet azimuthal transverse single-spin asymmetry, sensitive to twist-3 initial-state quark-gluon correlators; the Collins asymmetry, sensitive to quark transversity coupled to the polarized Collins fragmentation function; and the first measurement of the “Collins-like” asymmetry, sensitive to linearly polarized gluons. Within the present statistical precision, inclusive-jet and Collins-like asymmetries are small, with the latter allowing the first experimental constraints on gluon linear polarization in a polarized proton. At higher values of jet transverse momenta, we observe the first nonzero Collins asymmetries in polarized-proton collisions, with a statistical significance of greater than 5σ. The results span a range of x similar to results from semi-inclusive deep-inelastic scattering but at much higher Q². The Collins results enable tests of …

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Physics and Astronomy Faculty Publications

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Physics and Astronomy Faculty Publications

Physics and Astronomy Faculty Publications

Phenomenology Of Neutron-Antineutron Conversion, Susan Gardner, Xinshuai Yan

Physics and Astronomy Faculty Publications

Physics and Astronomy Faculty Publications