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Longitudinal parity-violating asymmetry in hadronic decays of weak bosons in polarized proton collisions
Berger, Edmond L.;Nadolsky, Pavel M.
High Energy Physics - Phenomenology , 2008, DOI: 10.1103/PhysRevD.78.114010
Abstract: We investigate the possible measurement of parity-violating spin asymmetries in jet pair production in proton-proton collisions at the Brookhaven Relativistic Heavy Ion Collider (RHIC), with the goal to constrain longitudinally polarized quark and antiquark distribution functions. A measurable asymmetry could be observed in the vicinity of the massive weak W boson resonance, where the parity-violating signal appears above the parity-conserving background and is enhanced by interference of the strong and electroweak production amplitudes. We discuss the potential for such measurements, perhaps the first opportunity to measure a parity-violating asymmetry in proton-proton collisions at RHIC. Sensitivity of this measurement to the polarization of down-type antiquarks is demonstrated.
Parity Violating Electron Scattering in the Relativistic Eikonal Approximation

DONG Tie-Kuang,REN Zhong-Zhou,

中国物理快报 , 2008,
Abstract: The parity violating electron scattering is investigated in the relativistic Eikonal approximation. The parity violating asymmetry parameters for many isotopes are calculated. In calculations the proton and neutron densities are obtained from the relativistic mean-field theory. We take Ni isotopes as examples to analyse the behaviour of the parity violating asymmetry parameters. The results show that the parity violating asymmetry parameter is sensitive to the difference between the proton and neutron densities. The amplitude of the parity violating asymmetry parameter increases with the distance between the minima of proton and neutron form factors. Our results are useful for future parity violating electron scattering experiments. By comparing our results with experimental data one can test the validity of the relativistic mean-field theory in calculating the neutron densities of nuclei.
Gluon Contributions to Parity-Violating Asymmetries in Polarized Proton-Proton Scattering  [PDF]
John Ellis,Stefano Moretti,Douglas Ross
Physics , 2001, DOI: 10.1088/1126-6708/2001/06/043
Abstract: We report on a calculation of one-loop weak corrections to polarized quark-gluon scattering and the corresponding crossed channels. Such contributions are suppressed formally by one power of alpha_s relative to W- or Z-mediated quark-quark scattering, but would enable the spin asymmetry of the gluon distribution to contribute to parity-violating asymmetries that will soon be investigated in polarized proton-proton scattering experiments at RHIC. In certain kinematic regions, gluon contributions to parity-violating asymmetries can be as large as 10% of the tree-level W- and Z-exchanges in quark-quark scattering, but usually only where the parity-violating asymmetries are already small.
Structure of Proton  [PDF]
Physics , 2003,
Abstract: Electron--proton scattering in elastic and highly inelastic region is reviewed in a unified approach. The importance of parity--violating scattering due to electro--weak interference in probing the structure of proton is emphasized. The importance of longitudnal spin--spin asymmetry as well as parity violating longitudnal asymmetry to extract the structure functions of proton in both regions are discussed. The recoil polarization of proton in the elastic scattering is also discussed.
Parity Violation in gamma proton Compton Scattering  [PDF]
Paulo F. Bedaque,Martin J. Savage
Physics , 1999, DOI: 10.1103/PhysRevC.62.018501
Abstract: A measurement of parity-violating spin-dependent gamma proton Compton scattering will provide a theoretically clean determination of the parity-violating pion-nucleon coupling constant $h_{\pi NN}^{(1)}$. We calculate the leading parity-violating amplitude arising from one-loop pion graphs in chiral perturbation theory. An asymmetry of ~5 10^{-8} is estimated for Compton scattering of 100 MeV photons.
Partonic calculation of $γZ$ Exchange Corrections to Parity-Violating Elastic Electron-Proton Scattering  [PDF]
Yu Chun Chen,Chung Wen Kao,Marc Vanderhaeghen
Physics , 2009,
Abstract: We calculate $\gamma Z$ exchange corrections to the parity-violating asymmetry of the elastic electron-proton scattering in a parton model using the formalism of generalized parton distributions(GPDs). We also examine the validity of the zero-momentum-transfer approximation adopted in the literatures and find that it overestimates the $\gamma Z$ exchange effect significantly at the forward scattering angles.
Model-dependence of the $γZ$ dispersion correction to the parity-violating asymmetry in elastic $ep$ scattering  [PDF]
Mikhail Gorchtein,C. J. Horowitz,Michael J. Ramsey-Musolf
Physics , 2011, DOI: 10.1103/PhysRevC.84.015502
Abstract: We analyze the dispersion correction to elastic parity violating electron-proton scattering due to $\gamma Z$ exchange. In particular, we explore the theoretical uncertainties associated with modeling contributions of hadronic intermediate states. Taking into account constraints from low- and high-energy, parity-conserving electroproduction measurements, choosing different models for contributions from the non-resonant processes, and performing the corresponding flavor rotations to obtain the electroweak amplitude, we arrive at an estimate of the uncertainty in the total contribution to the parity-violating asymmetry. At the kinematics of the Q-Weak experiment, we obtain a correction to the asymmetry equivalent to a shift in the proton weak charge of $(0.0054\pm0.0020)$. This should be compared to the value of the proton's weak charge of $\qwp=0.0713\pm0.0008$ that includes SM contributions at tree level and one-loop radiative corrections. Therefore, we obtain a new Standard Model prediction for the parity-violating asymmetry in the kinematics of the Q-Weak experiment of $(0.0767\pm0.0008\pm0.0020_{\gamma Z})$. The latter error leads to a relative uncertainty of 2.8% in the determination of the proton's weak charge, and is dominated by the uncertainty in the isospin structure of the inclusive cross section. We argue that future parity-violating inelastic $ep$ asymmetry measurements at low-to-moderate $Q^2$ and $W^2$ could be exploited to reduce the uncertainty associated with the dispersion correction. Because the corresponding shift and error bar decrease monotonically with decreasing beam energy, a determination of the proton's weak charge with a lower-energy experiment or measurements of "isotope ratios" in atomic parity-violation could provide a useful cross check on any implications for physics beyond the Standard Model derived from the Q-Weak measurement.
Two-Photon-Exchange Correction to Parity-Violating Elastic Electron-Proton Scattering  [PDF]
Andrei V. Afanasev,Carl E. Carlson
Physics , 2005, DOI: 10.1103/PhysRevLett.94.212301
Abstract: Higher-order QED effects play an important role in precision measurements of nucleon elastic form factors in electron scattering. Here we introduce a two-photon exchange QED correction to the parity-violating polarization asymmetry of elastic electron-proton scattering. We calculate this correction in the parton model using the formalism of generalized parton distributions, and demonstrate that it can reach several per cent in certain kinematics, becoming comparable in size with existing experimental measurements of strange-quark effects in the proton neutral weak current.
Parity-Violating Interaction Effects I: the Longitudinal Asymmetry in pp Elastic Scattering  [PDF]
J. Carlson,R. Schiavilla,V. R. Brown,B. F. Gibson
Physics , 2001, DOI: 10.1103/PhysRevC.65.035502
Abstract: The proton-proton parity-violating longitudinal asymmetry is calculated in the lab-energy range 0--350 MeV, using a number of different, latest-generation strong-interaction potentials--Argonne V18, Bonn-2000, and Nijmegen-I--in combination with a weak-interaction potential consisting of rho- and omega-meson exchanges--the model known as DDH. The complete scattering problem in the presence of parity-conserving, including Coulomb, and parity-violating potentials is solved in both configuration- and momentum-space. The predicted parity-violating asymmetries are found to be only weakly dependent upon the input strong-interaction potential adopted in the calculation. Values for the rho- and omega-meson weak coupling constants $h^{pp}_\rho$ and $h^{pp}_\omega$ are determined by reproducing the measured asymmetries at 13.6 MeV, 45 MeV, and 221 MeV.
The Two-Boson-Exchange Correction to Parity-Violating Elastic Electron-Proton Scattering  [PDF]
Shin Nan Yang,Keitaro Nagata,Hai Qing Zhou,Chung Wen Kao
Physics , 2009,
Abstract: We calculate the two-boson-exchange (TBE) corrections to the parity-violating asymmetry of the elastic electron-proton scattering in a simple hadronic model including the nucleon and the $\Delta(1232)$ intermediate states. We find that $\Delta$ contribution $\delta_\Delta$ is, in general, comparable with the nucleon contribution $\delta_N$ and the current experimental measurements of strange-quark effects in the proton neutral weak current. The total TBE corrections to the current extracted values of $G^{s}_{E}+\beta G^{s}_{M}$ in recent experiments are found to lie in the range of $-7\sim +7%$.
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