$W^{\pm}\pi_t^{\mp}$ Associated Production at Large Hadron Collider

In this paper we calculate the production of a charged top pion in association with a $W$ boson at the CERN Large Hadron Collider (LHC) in the context of the topcolor assisted technicolor model. We find that the cross section of $pp \rightarrow b\bar{b} \rightarrow W^{\pm}\pi_t^{\mp}$ is roughly corresponding to the result of the process $pp \rightarrow b\bar{b} \rightarrow W^{\pm}H^{\mp}$ in the minimal supersymmetric standard model, and for reasonable ranges of the parameters, the cross section can reach a few hundred fb. The $W^{\pm}\pi_t^{\mp}$ signal should be clearly visible at LHC unless $\pi_t^{\pm}$ is very heavy.     

A measurement of $K^{*\pm}$ production in the hyperon beam experiment at CERN

We report on a measurement of the differential cross sections of inclusive production in and neutron beams. A strong leading particle effect was observed for production by . The measured –distributions are compared with calculations based on the Lund model (PYTHIA) and the quark-gluon string model. Received: 6 August 2001 / Revised version: 3 September 2001 / Published online: 5 October 2001     

Pion-induced ${K}^{* }$ production with ${{\rm{\Sigma }}}^{* }$ baryon off proton target

In this work, the reaction ${\pi }^{-}p\to {K}^{* }{{\rm{\Sigma }}}^{* }$ is investigated with an effective Lagrangian approach. The contributions from the Born terms, including the s, t, and u channel, are considered, and the Regge model and the Feynman model are applied to treat the t -channel contribution. The existing experimental data can be reproduced with the best-fitted χ ² being 2.38 and 1.54 for the Feynman and Regge models, respectively. Moreover, it is found that the contribution from the t channel is dominant in the cross-section. The contribution of the u channel is mainly distributed at backward angles, and the contribution from the s channel is small and negligible. In the Feynman model, the contribution of the t -channel K exchange is much larger than the contribution of the ${K}^{* }$ exchange, while in the Regge model the contribution of the t -channel K exchange is comparable to that of the ${K}^{* }$ exchange. Prediction about the differential cross-section of the ${\pi }^{-}p\to {K}^{* }{{\rm{\Sigma }}}^{* }$ reaction is also presented, which is helpful for clarifying the role of the Regge treatment. The current results suggest high-precision experimental measurements which can be performed at J-PARC and COMPASS.     

Interference of Higgs boson resonances in $\mu^ + \mu^- \to\tilde{\chi}^0_i\tilde{\chi}^0_j$ with longitudinal beam polarization

We study the interference of resonant Higgs boson exchange in neutralino production in m⁺ m^-\mu^ + \mu^- annihilation with longitudinally polarized beams. We use the energy distribution of the decay lepton in the process [(c)\tilde]⁰_j ? l^± [(l)\tilde]^-±\tilde{\chi}^0_j \to \ell^{\pm} \tilde{\ell}^\mp to determine the polarization of the neutralinos. In the CP-conserving minimal supersymmetric standard model a non-vanishing asymmetry in the lepton energy spectrum is caused by the interference of Higgs boson exchange channels with different CP-eigenvalues. The contribution of this interference is large if the heavy neutral bosons H and A are nearly degenerate. We show that the asymmetry can be used to determine the couplings of the neutral Higgs bosons to the neutralinos. In particular, the asymmetry allows one to determine the relative phase of the couplings. We find large asymmetries and cross sections for a set of reference scenarios with nearly degenerate neutral Higgs bosons.     

Study Pure Annihilation Decays $B_s^0(\bar B_s^0)\rightarrow D^{\pm}\pi^{\mp}$ in PQCD Approach

The rare decays $B_s^0\rightarrow D^\pm \pi^\mp$ and $\bar B_s^0\rightarrow D^\mp \pi^\pm$ can occur only via annihilation-type diagrams in the standard model. In this paper, we calculate branching ratios of these decays in perturbative QCD approach ignoring soft final state interaction. From our calculation, we find that their branching ratios are at O(10^-6) with large CP asymmetry, which may be measured in LHC-b experiment in the future.     

CP-violation in the production of $\tau$-leptons at TESLA with beam polarization

We study the prospects of discovering CP-violation in the production of leptons in the reaction at TESLA, an e ⁺ e ^- linear collider with center-of-mass energies of 500 or even 800 GeV. Non-vanishing expectation values of certain correlations between the momenta of the decay products of the two leptons would signal the presence of CP-violation beyond the standard model. We study how longitudinal beam polarization of the electron and positron beams will enhance these correlations. We find that T-odd and T-even vector correlations are well suited for the measurements of the real and imaginary parts of the electric dipole form factors. We expect measurements of the real part with a precision of roughly 10^-20 e cm and of the imaginary part of 10^-17 Received: 13 June 2002 / Revised version: 17 October 2002 / Published online: 20 December 2002     

Longitudinal $\bar{\Lambda}_0$ polarization in heavy-ion collisions as a probe for QGP formation

We present an analysis of the longitudinal polarization in ultrarelativistic heavy-ion collisions. The polarization of s coming from the decay chain exhibits a very well differentiated behavior depending on the production region of the primordial s. This effect reflects the different values of the ratio in the QGP region, where nucleon-nucleon interactions take place in a hot and dense environment, and the peripherical region, in which ordinary nucleon-nucleon interactions occur. An increase in the longitudinal polarization signals a strangeness enhancement which is thought of as a property of the QGP phase.Received: 21 September 2004, Revised: 25 October 2004, Published online: 17 December 2004     

Annihilation amplitudes and factorization in $B^\pm\to\phi K^{*\pm}$

We study the decay , followed by the decay of the outgoing vector mesons into two pseudoscalars. The analysis of the angular distributions of the decay products is shown to provide useful information about the annihilation contributions and possible tests of factorization. Received: 2 April 2003 / Published online: 2 June 2003     

Universal behaviors of mutual information in one-dimensional ${\sf J}_1-{\sf J}_2$ model

The critical behaviors of the entropy correlation effects in the one dimensional J₁-J₂ Heisenberg model are studied. It is shown that the mutual information or the correlation entropy captures the key features of information about critical fluctuations and can be used to quantify the quantum and finite-temperature phase transitions. At the critical point, the mutual information is power-law decay and the entanglement correlation length is infinite. While far away from the critical point, the mutual information is exponential decay and the entanglement correlation length is finite. A universal property of the mutual information is also found. Based on the critical behaviors of the mutual information, a new method to quantify the infinite order phase transition in the system is proposed.     

Predictions for ${\bar \nu} \nu \gamma$ production at LEP

We study predictions for the reaction . The complete one-loop corrections are taken into account and higher order contributions, in particular those for the observed real photons, are added whenever necessary. The event generator MC, a general-purpose Monte Carlo generator for the process based on the method of exclusive exponentiation, is used as the environment. We extend its applicability to the process ,, where the observation of at least a single is required. The exponentiation is implemented in much the same way as for the s-channel process alone. In particular, all photonic effects present in the case of W exchange, which cannot be included in the s-channel exponentiation scheme, are calculated to a finite order only. The real hard photon matrix element is calculated up to . Leading logarithmic contributions of the two-loop corrections and one-loop photonic corrections accompanying real single-photon emission are included. The electroweak corrections are calculated with the DIZET library of the ZFITTER package. Numerical tests and predictions for typical observables are presented. Received: 30 October 2001 / Revised version: 5 March 2002 / Published online: 22 May 2002     

On PPT States in ${\cal C}^K \otimes {\cal C}^M\otimes {\cal C}^N$ Composite Quantum Systems

We study the general representations of positive partial transpose (PPT) states in ${\cal C}^K \otimes {\cal C}^M \otimes {\cal C}^N$. For the PPT states with rank-N a canonical form is obtained, from which a sufficient separability condition is presented.     

A search for a narrow radial excitation of the $\mathrm{D}^{*\pm}$ Meson

A sample of 3.73 million hadronic Z decays, recorded with the OPAL detector at LEP in the years 1991–95, has been used to search for a narrow resonance corresponding to the decay of the meson into . The mesons are reconstructed in the decay channel with . No evidence for a narrow resonance is found. A limit on the production of narrow in hadronic Z decays is derived: Received: 16 January 2001 / Published online: 28 May 2001