Transverse hadronic energy emission in hard scattering processes

We discuss the distribution of transverse energy associated with soft multigluon emission from incoming quarks in hard processes such as high-mass lepton pair and hadron jet production, with particular emphasis on the dependence on detector angular configuration and the effects of non-leading QCD corrections.     

High energy predictions for ¯pp andpp elastic scattering and total cross sections

Predictions for thes behavior at high energies are made for¯pp andpp: the differential elastic scattering cross section dσ/dt vs.t, the squared 4-momentum transfer; the total elastic cross sectionσ _el; the nuclear slope parameterB; the curvature parameterC; ?, the ratio of the real to the imaginary portion of the forward scattering amplitude; and the total cross sectionσ _tot. A hybrid approach is employed in order to gain reliable predictions. The energy dependence of? andσ _tot is fixed by fittingpp and¯pp experimental data for? andσ _tot from 15 GeV toS¯ppS energies, using analytic amplitudes. The other quantities are found using the Chou-Yang model, where the total, cross section is fixed from the fit.     

On the calculation of scattering cross sections from absorption cross sections

A dispersion-type relation between photon scattering and absorption cross sections is derived. It is shown that the relation gives the correct scattering cross section in the low and high frequency limits, and is consistent with the Kramers-Heisenberg formula in the vicinity of a resonance. The practical application of the relation is illustrated by calculations of the scattering cross section and refractive index of He and Ne at STP and dry air at 1200°K from known absorption cross section data. The method is useful for obtaining scattering cross sections, polarizabilities, and refractive indices at elevated temperatures.     

Next-to-leading order jet cross sections in polarized hadronic collisions

We present a next-to-leading order computation in QCD of one-jet and two-jet cross sections in polarized hadronic collisions. Our results are obtained in the framework of a general formalism that deals with soft and collinear singularities using the subtraction method. We construct a Monte Carlo programme that generates events at the partonic level. We use this code to give phenomenological predictions for pp collisions at √S = 500 GeV, relevant for the spin physics programme at RHIC. The possibility of using jet data to constrain the poorly known polarized parton densities is examined.     

High energy behaviour of total cross sections in weak interactions

We propose a new method for the computation of the high energy limit of the total cross section in spontaneously broken gauge theories. It is based on an evolution equation for effective couplings in dependence on the gauge boson mass. We apply this method to weak interactions in the leading logarithm approximation. Perturbation theory becomes invalid at very high energies since one of the couplings becomes strong. The obtained total cross sections obey Froissart's bound, in contrast to previous results not using the evolution equation.     

Differential cross sections for high energy elastic hadron-hadron scattering in nonperturbative QCD

Total and differential cross sections for high energy and small momentum transfer elastic hadron-hadron scattering are studied in QCD using a functional integral approach. The hadronic amplitudes are governed by vacuum expectation values of lightlike Wegner-Wilson loops, for which a matrix cumulant expansion is derived. The cumulants are evaluated within the framework of the Minkowskian version of the model of the stochastic vacuum. Using the second cumulant, we calculate elastic differential cross sections for hadron-hadron scattering. The agreement with experimental data is good. Received: 3 September 1998 / Published online: 19 November 1998     

Elastic cross sections for electron--carbon scattering

We used the close-coupling optical (CCO) approach to investigate the open-shell carbon atom. The elastic cross sections have been presented at the energies below 90eV, and the present CCO results have been compared with other theoretical results. We found that polarization and the continuum states have significant contributions to the elastic cross sections. The present calculations show that the CCO method is capable of calculating electron scattering from open-shell atoms.     

碰撞能量对He-N2的散射截面的影响

用密耦近似方法计算了He和N2体系的微分截面和总截面及转动激发分波截面,得出微分截面及总截面随入射能量变化的规律.     

Experimental verification of Rayleigh scattering cross sections

The cavity-ringdown technique is applied to measure Rayleigh extinctions of Ar, N(2), and SF(6) in the 560-650-nm region at 294 K. It is shown that experimental and calculated Rayleigh scattering cross sections agree within an experimental uncertainty of 1% (for SF(6), 3%).     

Inelastic partial cross sections for scattering of HF by neon

An analytic expression of the potential energy surface (PES) of the ground state of the Ne-HF complex is obtained by utilizing nonlinear least square method to fit the intermolecular interaction energies [Zhang Y. Guizhou Science, 2003, 21(3): 9–13 (in Chinese)], which have been computed using the augmented correlation-consistent polarized quadruple zeta basis set aug-cc-pVQZ at the theoretical level of CCSD (T). On the basis of the PES, the partial cross sections (PCSs) at the incident energies of 60, 75, 100 and 150 meV for collisions between Ne atoms and HF molecules are calculated using the quantum close coupling approach. The effects of the long-range attractive and the short-range anisotropic interactions on the inelastic PCSs are discussed in detail. The results show: (1) The long-range attractive well of the EPS makes the significant contribution to the lower excitation PCSs, especially the tail maximum for j = 0→j′ = 1 transitions, whereas no contribution is to the j′⩾3 inelastic transitions. (2) The short-range (the repulsive and attractive) interaction makes the significant contribution to the lower excitation PCSs, especially the main peak for j = 0→j′ = 1, 2. As for the transitions of j′⩾3, the short-range interaction plays a key role in the inelastic excitation. (3) Although the positions of the maximums and minimums of the inelastic PCSs are different at the collision energies, they correspond to almost the same impact parameter. Supported by the National Natural Science Foundation of China (Grant Nos. 10676025 and 10574096)     

Target-spin effects on elastic scattering cross sections

It is shown, using a simple model and empirical results, that the odd-even differences in the scattering of He ions from ⁵⁹Co and ⁶⁰Ni can be explained as due to the scattering from the quadrupole moment which is allowed for the odd target nucleus but not the even.     

Quest for precision in hadronic cross sections at low energy: Monte Carlo tools vs. experimental data

We present the achievements of the last years of the experimental and theoretical groups working on hadronic cross section measurements at the low-energy e ⁺ e ^? colliders in Beijing, Frascati, Ithaca, Novosibirsk, Stanford and Tsukuba and on τ decays. We sketch the prospects in these fields for the years to come. We emphasise the status and the precision of the Monte Carlo generators used to analyse the hadronic cross section measurements obtained as well with energy scans as with radiative return, to determine luminosities and τ decays. The radiative corrections fully or approximately implemented in the various codes and the contribution of the vacuum polarisation are discussed.     

First measurements of positronium total scattering cross sections

A new type of experiment has been devised in which ortho-positronium diffusion to the metal walls of a series of parallel-sided cells is studied by measuring the annihilation lifetimes. Experimental results are subjected to an analysis in which two parameters are varied to give a best fit, one of the two parameters being the scattering cross section. The method requires a number of systematic corrections which have still to be worked out. Preliminary cross section values for helium, argon and isobutane are 0.017 πa ₀ ² , 0.09 πa ₀ ² , and 0.54 πa ₀ ² , respectively.