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Register a new userSpin matrix elements for the elastic proton-proton and proton-antiproton collisions
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Motivated by the present extensive RHIC (BNL) spin program and further PAX project at FAIR, we study the possibility of explicit reconstruction of full set of helicity amplitudes by joint consideration of elastic proton-proton and proton-antiproton scattering. Procedure is based on the derivative relations for the helicity amplitudes, explicit parametrization of the leading spin non-flip amplitudes and crossing - symmetry relations. Some preliminary results are presented for the PAX energies to show the expected magnitudes of the spin dependent observables as a functions of invariant Mandelstams variables $s$ and $t$.
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The explicit procedures are described for reconstruction of the full set of helicity amplitudes in proton-proton and proton-antiproton elastic scattering. The procedures are based on the derivative relations for the helicity amplitudes in s-channel, on the explicit parametrization of the leading spin non flip amplitudes and crossing - symmetry relations. Asymptotic theorems are used for definition of free parameters in derivative relations. We also study the Odderon influence on the helicity amplitude reconstruction. Reconstruction procedures are valid at extremely wide energy domain and broad range of momentum transfer. These procedures might be useful in studying the spin phenomena in proton-proton and proton-antiproton elastic scattering.
The analysis of data on hyperon transverse momentum distributions, dN/dPt, that were gathered from various experiments (ISR, STAR, UA1, UA5 and CDF) reveals an important difference in the dynamics of multiparticle production in proton-proton vs. antiproton-proton collisions in the region of transverse momenta 0.3 GeV/c < Pt < 3 GeV/c. Hyperons produced with proton beams display the sharp exponential slope at low Pt, while spectra prodused with antiproton beam dont. Since LHC experiments have proton projectiles, the spectra of baryon production should seem softer in comparison to expectations, because the Monte Carlo simulations were based on the Tevatron antiproton-proton data. From the point of view of Quark-Gluon String Model, the most important contribution into the particle production spectra goes from antidiquark-diquark string fragmentation that exists only in the topological diagram for antiproton-proton collisions and is a very interesting object for investigation even at lower energies. This study may have an impact not only on interpretation of LHC results, but also on the cosmic ray physics and astrophysics, where the baryon contribution into matter-antimatter asymmetry is being studied.
Hadronic matrix elements of proton decay are essential ingredients to bridge the grand unification theory to low energy observables like proton lifetime. In this paper we non-perturbatively calculate the matrix elements, relevant for the process of a nucleon decaying into a pseudoscalar meson and an anti-lepton through generic baryon number violating four-fermi operators. Lattice QCD with 2+1 flavor dynamical domain-wall fermions with the {it direct} method, which is direct measurement of matrix element from three-point function without chiral perturbation theory, are used for this study to have good control over the lattice discretization error, operator renormalization, and chiral extrapolation. The relevant form factors for possible transition process from an initial proton or neutron to a final pion or kaon induced by all types of three quark operators are obtained through three-point functions of (nucleon)-(three-quark operator)-(meson) with physical kinematics. In this study all the relevant systematic uncertainties of the form factors are taken into account for the first time, and the total error is found to be the range 30%-40% for $pi$ and 20%-40% for $K$ final states.
We present an overview of the measurements of the like-sign dimuon charge asymmetry by the DO Collaboration at the Fermilab Tevatron proton-antiproton Collider. The results differ from the Standard Model prediction of CP violation in mixing and interference of B^0 and B^0_s by 3.6 standard deviations.
The spin alignment matrix element rho_{00} for the vector mesons K^{*0} and phi(1020) has been measured in RHIC at central rapidities. These measurements are consistent with the absence of polarization with respect to the reaction plane in mid-central Au + Au collisions whereas, when measured with respect to the production plane in the same reactions and in p + p collisions, a non-vanishing and p_perp-dependent rho_{00} is found. We show that this behavior can be understood in a simple model of vector meson production where the spin of their constituent quarks is oriented during hadronization as the result of Thomas precession.
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