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Liang Zuo-tang

Publications and source records attributed to Liang Zuo-tang.

15 recordsLinked to original sources
arXiv2002

Spin Alignment of Vector Meson in High Energy Reactions

The recent data on the polarization of vector meson at LEP show that the vector mesons favor the helicity zero state. We calculate the helicity density matrix of vector meson which contains a polarized fragmenting quark by adding the spin of the fragmenting quark and that of the antiquark created in the fragmentation. The data at LEP imply a significant polarization for the antiquark in the opposite direction as that of the fragmenting quark. We extend the calculations to other reactions and make predictions for vector mesons in deeply inelastic lepton-nucleon scatterings and polarized $pp$ collisions.

hep-ph↗
arXiv2001

Hadronization mechanisms and spin effects in high energy fragmentation processes

Spin effects in high energy fragmentation processes can provide us with important information on hadronization mechanisms and spin structure of hadrons. It can in particular give new tests to the hadronization models. In this talk, we make a brief introduction to the different topics studied in this connection and a short summary of the available data. After that, we present a short summary of the main theoretical results we obtained in studying these different topics. The talk was mainly based on the publications [4-8] which have been finished in collaboration with C.Boros, Liu Chun-xiu and Xu Qing-hua.

hep-ph↗
arXiv1998

Hadronization mechanisms and longitudinal polarization of Lambda in e+e- annihilation at high energies

We suggested that longitudinal polarization of Lambda produced in e+e- annihilation at LEP energies can provide useful information on hadronization mechanism in general and on testing the validity of different pictures for the spin content of baryon in describing the fragmentation process in particular. We present the results obtained from the calculations based on two very much different pictures.We compare the results with the recent ALEPH data and make suggestions for future measurements.

hep-ph↗
arXiv1998

Hyperon polarization and single-spin asymmetries in different hadronic reactions

We show that the polarization of hyperons observed in high energy collisions using unpolarized hadron beams and unpolarized nucleon or nuclear targets is closely related to the left-right asymmetries observed in single spin inclusive hadron production processes. The relationship is most obvious for the production of the hyperons which have only one common valence quark with the projectile. Further implications of the existence of large polarization for hyperon which has two valence quarks in common with the projectile and their consequences are discussed. A comparison with the available data is made. Further tests are suggested.

hep-ph↗
arXiv1998

Spin content of Lambda and its longitudinal polarization in $e^+e^-$ annihilation at high energies

Longitudinal polarization of Lambda produced in $e^+e^-$ annihilation at LEP energies is calculated in a picture for the spin content of Lambda which is consistent with the polarized deep inelastic lepton-nucleon scattering data and SU(3) flavor symmetry for hyperon decay so that the spin of Lambda is not completely carried by its $s$-valence quark. A comparison with the recent ALEPH data and the results of earlier calculations based on the static quark model in which the spin of Lambda is completely determined by the $s$-quark is given. The result shows that further measurements of such polarization should provide useful information to the question of which picture is more suitable in describing the spin effects in the fragmentation processes.

hep-ph↗
arXiv1997

Hyperon polarization and single spin left-right asymmetry in inclusive production processes at high energies

It is shown that the polarization of hyperons observed in high energy collisions using unpolarized hadron beams and unpolarized nucleon or nuclear targets is closely related to the left-right asymmetries observed in single spin inclusive hadron production processes. The relationship is most obvious for the production of the hyperons which have only one common valence quark with the projectile. Examples of this kind are given. Further implications of the existence of large polarization for hyperon which has two valence quarks in common with the projectile and their consequences are discussed. A comparison with the available data is made. Further tests are suggested.

hep-ph↗
arXiv1997

Probing the exchanged object(s) in diffractive scattering

The reaction mechanisms of the following proton diffractive scattering processes are studied and compared with one another: $γ^* p\to Vp,γ^* p\to Xp, pp\to (ΛK^+)p$ and $pA\to ΛK^+A$ (Here, $γ^*$ stands for the space-like photon in inelastic electron-proton scattering, $V$ for the vector mesons $ρ,ω,ϕ,J/ψ$, and $A$ for a target nucleus.) It is shown that, by taking parity, and C--parity conservation into account, the existing data for these reactions strongly suggest the following: A considerable part of the objects exchanged between projectile and target in the above-mentioned processes are virtual quark-antiquark pairs in color-singlet states with $J^{PC}=0^{-+}$, $I^G=0^+$, where $J$ stands for total angular momentum, $I$ for isospin, $P$, $C$ and $G$ stand for parity, C-parity and G-parity respectively. Such quark-antiquark pairs are created by soft-gluon interactions. New experiments are suggested; and predictions for such experiments are made.

hep-ph↗
arXiv1996

Colorless and colored gluon-clusters in nucleon?

It is suggested that virtual gluon-clusters exist in nucleon, and that such colorless and colored objects manifest themselves in the small $x_B$ region of inelastic lepton-nucleon scattering processes. The relationship between the space-time properties of such clusters and the striking features observed in these scattering processes is discussed. A phase-space model is used to show how quantitative results can be obtained in such an approach. The results of this model-calculation are in reasonable agreement with the existing data. Further experiments are suggested.

hep-ph↗
arXiv1996

Probing dissociation of space-like photons in deep-inelastic lepton-nucleon scattering

It is shown that the hadronic dissociation of space-like $(Q^2>0)$ photons can be directly probed by performing measurements in the fragmentation region of transversely polarized and unpolarized proton beams at the electron-proton collider HERA. Measurements of momentum-distributions in the photon-fragmentation region in normal and in LRG (large rapidity gap) events are also suggested --- especially when the scattered proton or neutron in the proton-beam direction is tagged. It is pointed out that such distributions can yield useful information on the mechanisms of hadronic fragmentation in general, and answer the following questions in particular: Is the well-known hypothesis of limiting fragmentation (HFL) valid in color-exchange, in flavor-exchange, or only in vacuum-quantum-number-exchange processes ?

hep-ph↗
arXiv1995

Hyperon production mechanisms and single-spin asymmetry in high energy hadron-hadron collisions

It is shown that the existence of left-right asymmetry in single-spin inclusive Lambda production, together with the characteristic features of the data, should be considered as another clear signature for the existence of orbiting valence quarks in polarized nucleons. Predictions for other hyperons are made. It is pointed out that measurements of such asymmetries are very helpful not only for probing the spin structure of the nucleons but also for studying the production mechanisms of the hyperons.

hep-ph↗