Single-spin asymmetry of inclusive neutral-pion production in pp ↑ interactions at 70 GeV in the region −0.4 < x F < −0.1 (original) (raw)
Single-spin asymmetry in pion production in polarized proton proton collisions and odderon
Journal of Physics G: Nuclear and Particle Physics, 2003
Single-spin asymmetry appears due to the interference of single and double gluon exchange between protons. A heavy fermion model is used to describe the jet production in the interaction of gluon with the proton implying the further averaging over its mass. As usually in one-spin correlations, the imaginary part of the double gluon exchange amplitude play the relevant role. The asymmetry in the inclusive setup with the pion tagged in the fragmentation region of the polarized proton does not depend on the center of mass energy in the limits of its large values. The lowest order radiative corrections to the polarized and unpolarized contributions to the differential cross sections are calculated in the leading logarithmical approximation. In general, a coefficient at logarithm of the ratio of cms energy to the pion mass depends on transversal momentum of the pion. This ratio of the lowest order contribution to the asymmetry may be interpreted as the partial contribution to the odderon intercept. The ratio of the relevant contributions in the unpolarized case can be associated with the partial contribution to the pomeron intercept. The numerical results given for the model describe the jet as a heavy fermion decay fragments.
Single spin asymmetry in inclusive pion production
AIP Conference Proceedings, 1995
It is shown how the single spin asymmetry observed in inclusive pion production is related, in the helicity basis, to the imaginary part of the product of two dierent distribution amplitudes, rather than to the usual quark and gluon distribution functions; there is then no reason why it should be zero even in massless perturbative QCD, provided the quark intrinsic motion is taken into account. A simple model is constructed which reproduces the main features of the data.
Beam-spin asymmetries from semi-inclusive pion electroproduction
Physical Review D, 2014
We have measured the moment A sin φ LU corresponding to the polarized electron beam-spin asymmetry in SIDIS. A sin φ LU is a twist-3 quantity providing information about quark-gluon correlations. Data were taken with the CLAS Spectrometer at Jefferson Lab using a 5.498 GeV longitudinally polarized electron beam and an unpolarized liquid hydrogen target. All three pion channels (π + , π 0 and π − ) were measured simultaneously over a large range of kinematics within the virtuality range Q 2 ≈ 1.0-4.5 GeV 2 . The observable was measured with good statistical precision over a large range of z, PT , xB, and Q 2 , which permits comparison with several reaction models. The discussed measurements provide an upgrade in statistics over previous measurements, and serve as the first evidence for the negative sign of the π − sin φ moment.
General properties of the pion production reaction in nuclear matter
Nuclear Physics A, 2004
The pion production reaction π + → π + π ± on 45 Sc was studied at incident pion energies of T π + = 240, 260, 280, 300, and 320 MeV. The experiment was performed using the M 11 pion-channel at TRIUMF, and multiparticle events, (π + , π + π ± ) and (π + , π + π ± p), were detected with the CHAOS spectrometer. Results are reported in the form of both differential and total cross sections, and are compared to theoretical predictions and the reaction phase space. The present investigation of the T-dependence of the π + A → π + π ± A ′ reaction complements earlier examinations of the Adependence of the reaction, which was measured using 2 H, 4 He, 12 C, 16 O, 40 Ca, and 208 P b targets at ∼280 MeV. Some general properties of the pion-induced pion production reaction in nuclear matter will be presented, based on the combined results of the two studies.
Physical Review D, 2001
A single-spin asymmetry in the azimuthal distribution of neutral pions relative to the lepton scattering plane has been measured for the first time in deep-inelastic scattering of positrons off longitudinally polarized protons. The analysing power in the sin(phi) moment of the cross section is 0.019 +/- 0.007(stat.) +/- 0.003(syst.). This result is compared to single-spin asymmetries for charged pion production measured in the same kinematic range. The pi^0 asymmetry is of the same size as the pi^+ asymmetry and shows a similar dependence on the relevant kinematic variables. The asymmetry is described by a phenomenological calculation based on a fragmentation function that represents sensitivity to the transverse polarization of the struck quark.
Single-spin asymmetries for small-angle pion production in high-energy hadron collisions
The European Physical Journal C, 1999
Within the framework of a simple model, we study single-spin asymmetries for pion production in hadron-hadron collisions at highenergies with one hadron polarised. The asymmetries are generated via a mechanism of final (initial) state interactions. For peripheral kinematics, when the pion belongs to the fragmentation region of the polarised proton, we find non-zero asymmetries in the high-energy limit. Numerical results and comparision with existing experimental data are presented. We also discuss the relationship with odderon exchange phenomenology. *
Recent Developments in one and two Pion Production in Elementary Reactions and Few-Body Systems
Few-Body Systems, 1995
In this talk we c o v er several issues concerning pion production. The rst one is the pp pp 0 reaction where an alternative explanation based on the o shell extrapolation of the N amplitude is oered. A recent model for the N N reaction is presented and a new kind of exchange current is constructed from it which allows one to address problems like double photoproduction from the deuteron. Finally the (;) reaction in nuclei is studied and shown to be highly sensitive to the renormalization of the pions in nuclei.
Azimuthal spin asymmetries of pion electroproduction
Physical Review D, 2002
Azimuthal spin asymmetries, both for charged and neutral pion production in semiinclusive deep inelastic scattering of unpolarized charged lepton beams on longitudinally and transversely polarized nucleon targets, are analyzed and calculated. Various assumptions and approximations in the quark distributions and fragmentation functions often used in these calculations are studied in detail. It is found that different approaches to the distribution and fragmentation functions may lead to quite different predictions on the azimuthal asymmetries measured in the HERMES experiments, thus their effects should be taken into account before using the available data as a measurement of quark transversity distributions. It is also found that the unfavored quark to pion fragmentation functions must be taken into account for π − production from a proton target, although they can be neglected for π + and π 0 production. Pion production from a proton target is suitable to study the u quark transversity distribution, whereas a combination of pion production from both proton and neutron targets can measure the flavor structure of quark transversity distributions.