Proposal for studying N* resonances with the (p)over-barp -> (p)over-barn pi(+) reaction

A theoretical study of the (p) over barp -> (p) over barn pi(+) reaction for antiproton beam energy from 1 to 4 GeV is made by including contributions from various known N* and Delta* resonances. It is found that for the beam energy around 1.5 GeV, the contribution of the Roper resonance N-(1440)* produced by the t-channel sigma exchange dominates over all other contributions. Since such a reaction can be studied in the forthcoming PANDA experiment at the GSI Facility of Antiproton and Ion Research (FAIR), the reaction will be realistically the cleanest place for studying the properties of the Roper resonance and the best place for looking for other "missing" N* resonances with large coupling to N sigma.

Analytical solution of a multidimensional Langevin equation at high friction limits and probability passing over a two-dimensional saddle

The analytical solution of a multidimensional Langevin equation at the overdamping limit is obtained and the probability of particles passing over a two-dimensional saddle point is discussed. These results may break a path for studying further the fusion in superheavy elements synthesis.

B-(*())(B)over-bar(()*()) intermediate states contribution to Gamma(4S, 5S) -> eta(b) + gamma radiative decay

In this work, we investigate the rescattering effects in the radiative decay Gamma(5S) -> eta(b) + gamma , which were suggested to be crucially important for understanding the anomalous largeness of the branching ratios B(Gamma(5S) -> Gamma(1S) + pi pi) and B(Gamma(5S) -> Gamma(1S) + eta). Our calculations show that the rescattering effects may enhance Gamma(Gamma(10860) -> eta(b) +gamma) by four orders, but the tetraquark structure does not. Recently the BABAR and CLEO collaborations have measured the mass of eta(b) and the branching ratios B(Gamma(2S) -> eta(b) +gamma), B(Gamma(3S) -> eta(b) +gamma). We hope that very soon, Gamma(10860) -> eta(b) + gamma) will be measured and it would be an ideal opportunity for testing whether the rescattering or the tetraquark structure is responsible for the anomaly of B(Gamma(5S) -> Gamma(nS) pi(+) pi(-))(n = 1, 2, 3)), i. e., the future measurements on the radiative decays of Gamma(5S) might be a touchstone of the two mechanisms.

Spectra of identified high-p(T) pi(+/-) and p((p)over-bar ) in Cu + Cu collisions at root s(NN)=200 GeV

We report new results on identified (anti) proton and charged pion spectra at large transverse momenta (3 < p(T) < 10 GeV/c) from Cu + Cu collisions at root s(NN) = 200 GeV using the STAR detector at the Relativistic Heavy Ion Collider (RHIC). This study explores the system size dependence of two novel features observed at RHIC with heavy ions: the hadron suppression at high-p(T) and the anomalous baryon to meson enhancement at intermediate transverse momenta. Both phenomena could be attributed to the creation of a new form of QCD matter. The results presented here bridge the system size gap between the available pp and Au + Au data, and allow for a detailed exploration of the onset of the novel features. Comparative analysis of all available 200 GeV data indicates that the system size is a major factor determining both the magnitude of the hadron spectra suppression at large transverse momenta and the relative baryon to meson enhancement.

Contributions of qqqq(q)over-bar Components to Axial Charges of Proton and N(1440)

The axial charges of the proton and N(1440) are studied in the framework of an extended constituent quark model (CQM) including qqqq (q) over bar components. The cancellation between the contributions of qqq components and qqqq (q) over bar components gives a natural explanation to the experimental value of the proton axial charge, which can not be well reproduced in the traditional CQM even after the SU (6) circle times O(3) symmetry breaking is taken into account. The experimental value of axial charge pins down the proportion of the qqqq (q) over bar component in the proton to about 20%, which is consistent with the ones given by the strong decay widths and helicity amplitudes. Besides, an axial charge for N(1440) about 1 is predicted with 30% qqqq (q) over bar component, which is obtained by the strong and electromagnetic decays.

NOx storage-reduction over Pt/Mg-Al-O catalysts with different Mg/Al atomic ratios

A series of Pt/Mg-Al-O catalysts with different Mg/Al atomic ratios were prepared. The NOx storage capacities of these catalysts were measured by isothermal storage at 350 degreesC. It was found that the NOx storage capacity increased with increasing Mg/Al atomic ratios. The catalytic behaviors of Pt/Mg-Al-O and Pt/MgO were studied with storage-reduction cycles at 400 degreesC. Under oxidizing conditions, NOx concentration in the outlet gas gradually increased with time, which indicated the catalysts could store NOx effectively. After a switch from oxidizing conditions to reducing conditions, NOx desorption peak emerged immediately due to the incomplete reduction of stored NOx, which lowered the total NOx conversion. With increasing Mg/Al atomic ratio in the catalysts, NOx conversion increases. Pt/MgO has the highest NOx conversion because of its best activity in the reduction of NOx by C3H6. It seems that with an increasing amount of MgO in the catalysts, the self-poisoning of Pt-sites by adsorbed species during the reaction of NOx with C3H6 may be inhibited effectively.

The reaction route and active site of catalytic decomposition of hydrazine over molybdenum nitride catalyst

The catalytic properties of the passivated, reduced passivated, and fresh bulk molybdenum nitride for hydrazine decomposition were evaluated in a microreactor. The reaction route of hydrazine decomposition over molybdenum nitride catalysts seems to be the same as that of Ir/gamma-Al2O3 catalysts. Below 673 K, the hydrazine decomposes into N-2 and NH3. Above 673 K, the hydrazine decomposes into N-2 and NH3 first, and then the produced NH3 further dissociates into N-2 and H-2. From the in situ FT-IR spectroscopy, hydrazine is adsorbed and decomposes mainly on the Mo site of the Mo2N/gamma-Al2O3 catalyst. (C) 2004 Elsevier Inc. All rights reserved.