arXiv subjects

Zuo-tang Liang

Publications and source records attributed to Zuo-tang Liang.

61 records · Page 4Linked to original sources

arXiv2001

Spin alignment of vector meson in e+e- annihilation at Z0 pole

We calculate the spin density matrix of the vector meson produced in e+e- annihilation at Z^0 pole. We show that the data imply a significant polarization for the antiquark which is created in the fragmentation process of the polarized initial quark and combines with the fragmenting quark to form the vector meson. The direction of polarization is opposite to that of the fragmenting quark and the magnitude is of the order of 0.5. A qualitative explanation of this result based on the LUND string fragmentation model is given.

hep-ph↗

arXiv2001

Energy Dependence of the Contribution of Pion Exchange to Large-Rapidity-Gap Events in Deep Inelastic Scattering

We study the energy dependence of the contribution of pion exchange to large-rapidity-gap events in deep inelastic scattering. The results show that this contribution can be quite significant at low energy and that the LRG events observed by E665 collaboration in μXe and μD interactions at 490 $GeV$ can be reasonably well described in terms of meson exchange. We also show that the distribution of the maximum rapidity for all hadrons is quite different from that for charged hadrons only and that the former exhibits also shoulder-like structure for events at 490 $GeV$ similar to that at HERA.

hep-ph↗

arXiv2000

Lambda polarization in pp -> pΛK^+ π^+π^-π^+π^-

We show that there is a correlation between the invariant mass of the produced ΛK^+, ΛK^+π^+π^- or ΛK^+ π^+π^-π^+π^- system in the exclusive reaction pp\to pΛK^+π^+π^-π^+π^- and the longitudinal or transverse momentum of $Λ$. Together with the longitudinal and transverse momentum dependence of Lambda polarization observed in inclusive reactions, such a correlation implies a dependence of Lambda polarization on these invariant masses. The qualitative features of this dependence are consistent with the recent observation by E766 collaboration at BNL. A quantitative estimation has been made using an event generator for $pp$ collisions. A detailed comparison with the data is made.

hep-ph↗

arXiv2000

Spin structure and longitudinal polarization of hyperon in e+e- annihilation at high energies

Longitudinal polarizations of different kinds of hyperons produced in e+e- annihilation at LEP I and LEP II energies in different event samples are calculated using two different pictures for the spin structure of hyperon: that drawn from polarized deep inelastic lepton-nucleon scattering data or that using SU(6) symmetric wave functions. The result shows that measurements of such polarizations should provide useful information to the question of which picture is more suitable in describing the spin effects in the fragmentation processes.

hep-ph↗

arXiv2000

Lambda polarization and single-spin left-right asymmetry in diffractive hadron-hadron collisions

We discuss Lambda polarization and single-spin left-right asymmetry in diffractive hadron-hadron scattering at high energies. We show that the physical picture proposed in a recent Letter is consistent with the experimental observation that $Λ$ polarization in the diffractive process, $pp\to ΛK^+p$, is much higher than that in the inclusive reaction, $pp\to ΛX$. We make predictions for the left-right asymmetry, A_N, and for the spin transfer, $D_{NN}^Λ$, in the single-spin process $p(\uparrow)p\to ΛK^+p$ and suggest further experimental tests of the proposed picture.

hep-ph↗

arXiv2000

Single spin asymmetries in inclusive high energy hadron-hadron collision processes

It has been realized for quite a long time that single-spin experiments, in which one of the colliding objects is transversely polarized, can be helpful in studying the properties of strong interaction in general and in testing Quantum Chromodynamics (QCD) in particular. Striking effects have been observed in the past few years which deviate drastically from the expectation of the perturbative QCD parton model. These effects have received much attention. New experiments of the similar type are underway and/or planned. Different theoretical attempts have been made to understand these effects. In this review, the special role played by singly polarized high-energy hadron-hadron collisions in High Energy Spin Physics is emphasized. Characteristics of the available data for inclusive hadron productions are briefly summarized. Different theoretical approaches for such processes are reviewed with special attention to a non-perturbative model which explicitly takes the orbital motion of the valence quarks and hadronic surface effects into account. The connection between such asymmetries and hyperon polarization in unpolarized reactions is discussed. An example of the possible application of such experimental results in other processes is given.

hep-ph↗

arXiv1996

Single Spin Asymmetries in Inclusive High Energy Hadron-Hadron Collision Processes

Characteristics of the available data are briefly summarized. Different theoretical approaches are reviewed with special attention to a non-perturbative model which explicitly takes the orbital motion of the valence quarks into account. The connection between such asymmetries and hyperon polarization in unpolarized reactions is discussed.

hep-ph↗