118961681
Spin alignments of vector mesons in deeply inelastic lepton-nucleon scattering
We extend the calculations of the spin alignments of vector mesons in $e^+e^-$ annihilation in a recent Rapid Communication to deeply inelastic lepton-nucleon scatterings. We present the results for different mesons in the current fragmentation regions of $\mu^- N$$ \to$$ \mu^- VX$ at high energies and $\nu_\mu N $$\to$$ \mu^- VX$ at both high and low energies. We also present the predictions for $\nu_\mu N$$ \to$$ \mu^- VX$ at NOMAD energies in the target fragmentation region using a valence quark model.
119448015
Probing gluon helicity distribution and quark transversity through hyperon polarization in singly polarized pp collisions
We study the polarization of hyperon in different processes in singly polarized $pp$ collisions, in particular its relation to the polarized parton distributions. We show that by measuring hyperon polarization in particularly chosen processes, one can extract useful information on these parton distributions. We show in particular that, by measuring the $\Sigma^+$ polarization in high $p_T$ direct photon production process, one can extract information on the gluon helicity distribution; and by measuring the transverse polarization of hyeprons with high $p_T$ in singly polarized reactions, one can obtain useful information on the transversity distribution. We present the numerical results obtained for those hyperon polarizations using different models for parton distribution function and those for the spin transfer in fragmentation processes.
120902857
Hyperon polarization in semi-inclusive deeply inelastic lepton-nucleon scattering at high energy
We calculate the polarizations for different octet hyperons produced in the current fragmentation regions of the deeply inelastic lepton-nucleon scatterings $\mu^-N \to \mu^- HX$ and $\nu_{\mu} N \to \mu^- HX$ at high energy using different models for spin transfer in fragmentation processes. The results show that measurements of those hyperon polarizations should provide useful information to distinguish between different models in particular the SU(6) and the DIS pictures used frequently in the literature. We found, in particular, that measuring the polarization of $\Sigma^+$ produced in these processes can give a better test to the validity of the different spin transfer models.
119294651
Antihyperon polarization in high energy p p collisions with polarized beams
We study the longitudinal polarization of the ${\overline{\ensuremath{\Sigma}}}^{\ensuremath{-}}$, ${\overline{\ensuremath{\Sigma}}}^{+}$, ${\overline{\ensuremath{\Xi}}}^{0}$, and ${\overline{\ensuremath{\Xi}}}^{+}$ antihyperons in polarized high-energy $pp$ collisions at large transverse momenta, extending a recent study of the $\overline{\ensuremath{\Lambda}}$ antihyperon. We make predictions by using different parameterizations of the polarized parton densities and models for the polarized fragmentation functions. Similar to the $\overline{\ensuremath{\Lambda}}$ polarization, the ${\overline{\ensuremath{\Xi}}}^{0}$ and ${\overline{\ensuremath{\Xi}}}^{+}$ polarizations are found to be sensitive to the polarized antistrange sea $\ensuremath{\Delta}\overline{s}(x)$ in the nucleon. The ${\overline{\ensuremath{\Sigma}}}^{\ensuremath{-}}$ and ${\overline{\ensuremath{\Sigma}}}^{+}$ polarizations show sensitivity to the light sea quark polarizations $\ensuremath{\Delta}\overline{u}(x)$ and $\ensuremath{\Delta}\overline{d}(x)$, and their asymmetry.
123007697
Contribution of Vector Meson Dominance to the Single-Spin Azimuthal Asymmetry in Semi-inclusive Pion Electro-Production
We calculate the contribution of vector meson dominance to deeply inelastic lepton-nucleon scattering in the kinematic region of the HERMES experiment. The results obtained show that this contribution is quite significant. Together with the fact that there exist very striking left-right asymmetries for hadrons produced in single-spin hadron-hadron collisions, these results imply that the single-spin azimuthal asymmetry observed by HERMES cannot be simply regarded as a pure fragmentation effect.
14189975
Spin alignment of the high p T vector mesons in polarized pp collisions at high energies
Using the same method as that used in $e^+e^-$ annihilation and lepton-nucleon deep-inelastic scattering, we calculate the spin alignment of vector mesons with high transverse momenta in high energy $pp$ collisions with one longitudinally polarized beam. We present the results obtained at RHIC energies. We also study the spin alignment of such vector mesons in the case of a transversely polarized proton beam and present its relation to the transversity distribution in the nucleon. Numerical results obtained using simple models for the transversity distributions are also given. These results show that there exist significant spin alignment in both cases, and they can be measured in experiments such as those at RHIC.
5505221
The rare top decay t → cg in topcolor assisted technicolor models
In the framework of topcolor-assisted technicolor(TC2) models, we calculate the contributions of flavor changing scalar couplings involved the neutral top-pion � 0 and top-Higgs h 0 to the branching ratio Br(t −→ cg). We find that the value of Br(t −→ cg) can reach 1 × 10 3 with reasonable values of the parameters in TC2 models, which may be testable in the future experiments.
17399206
Production and decay of the neutral top pion in high-energy e+ e- colliders
We study the production and decay of the neutral top-pion � 0 predicted by topcolor-assisted technicolor(TC2) theory. Our results show that, except the dominant decay modes b ¯, ¯ and gg, the � 0 t can also decay into and Z modes. It can be significantly produced at high energy e + e collider(LC) experiments via the processes e + e → � 0 and e + e → Z� 0 t. We further calculate the production cross sections of the processes e + e → � 0 → ¯ and e + e → Z� 0 → Z¯ tc. We find that the signatures of the neutral top-pion � 0 can be detected via these processes.