Rising total cross sections

As two hadrons pass one another the vacuum between them becomes polarised. It is shown that quark-loop contributions to the vacuum polarisation account for most, if not all, of the rise of the total cross section with energy.     

The rise of total cross sections and a critical pomeron

The framework of a Reggeon Field Theory with thresholds in rapidity is used to predict the rise of pp total cross section while maintaining the critical character of the pomeron.     

Double pomeron jet cross sections

We treat hadron-hadron collisions where the final state is kinematically of the kind associated with double-pomeron-exchange (DPE) and has large transverse momentum jets. We show that in addition to the conventional factorized (FDPE) contribution, there is a nonfactorized (NDPE) contribution which has no pomeron beam jet. Within a simple model we compute DPE-two-jet total and differential cross sections at Tevatron energy scales, and show that the NDPE contribution is dominant.     

Inclusive cross sections in the central region and the supercritical pomeron

Using the double-Regge formalism and a supercritical pomeron with α_P(0)=1+Δ, we analyse the energy dependence of inclusive cross sections for negatively charged particles (c⁻) and K_s⁰ at CM rapidity y=0 in the CERN PS-Sp̄pS collider energy range. The values of Δ(c⁻)=0.170±0.008 and Δ(K_s⁰)=0.167±0.024 are found to be very close to each other and compatible with estimates of Δ derived from the total cross sections.     

Heavy-ion total reaction cross sections

A one-parameter expression has been found which predicts with a smaller χ² than previous expressions, the total reaction cross sections for a large number of heavy-ion systems covering a wide energy range. The expression uses an interaction radius which is a sum of the equivalent uniform matter radii of the interacting nuclei plus and energy-dependent term.     

Measurement of the neutrino-nucleon and antineutrino-nucleon total cross sections

The v and $\text{v}$ nucleon total cross-sections have been determined as a function of energy using a sample of 2500 v and 950 $\text{v}$ event. The results are compared with predictions of scaling and charge symmetry hypotheses.     

Universality tests for total cross sections

Starting directly from data we test the universality of the decomposition of total cross-sections in an asymptotically dominant term, the Pomeron, and a non dominant one, the Reggeon. Without assuming Regge pole model behaviour or additive quark model relations we show that data are compatible with both models. Support is not found for models predicting asymptotical equality of total cross-sections.     

Upper bound on total cross sections

It is shown, under certain assumptions, that if the Nth derivative of the absorptive part of an elastic scattering amplitude exists in the interval t ₁t0, then, the total cross section has the asymptotic upper bound      

Pionization effects in proton-nucleus total cross sections

A simple unitary model for meson production effects in proton-nucleus scattering was used earlier to estimate the pionization corrections to the proton-deuteron total cross section. This model is here used to study the corresponding effects in heavy nuclei using a generalization of the optical limit. An increase in the total cross sections at the upper limit of NAL energies of roughly 20% is found.     

Alignment effects in deuteron total cross sections

The alignment dependence of the total cross section of deuterium is a purely multiple scattering phenomenon. An estimate of this for pion scattering using Glauber theory shows that the most important contribution is associated with the deuteron D-state (typically 1%) with corrections coming from the double spin flip. Measurements of the proton total cross section with an aligned deuteron beam should also yield other interesting information on the wave function of the deuteron D-state.     

Constraints on the asymptotic behaviour of total cross sections

We derive constraints on the asymptotic behaviour of total cross sections which follow from dispersion relations and measured real parts of the forward scattering amplitudes. For πN and pp scattering, these constraints are calculated using recent results from FNAL and Serpukhov. The relation to other methods is discussed.     

Fast-neutron total and scattering cross sections of elemental titanium

Energy-averaged total neutron cross sections of elemental titanium are measured from ? 1.0 to 4.5 MeV with statistical accuracies of ? 1%. Differential elastic neutron-scattering angular distributions are measured from 1.5 to 4.0 MeV at incident energy intervals of ≦ 0.2 MeV. Differential cross sections for the inelastic neutron excitation of “states” in titanium at 158 ± 26, 891 ± 8, 984 ± 15, 1428 ± 39, 1541 ± 30, 1670 ± 80, 2007 ± 8, 2304 ± 22, 2424 ± 16 and 2615 ± 10 keV are measured in the incident-neutron energy range 1.5 to 4.0 MeV. Neutrons corresponding to additional states at approximately 2845 and 3010 keV were qualitatively observed. The experimental results are interpreted in terms of an energy-averaged optical-statistical and coupled-channels models including consideration of collective vibrations. The implications of these models and their use in the context of strong fluctuating structure are discussed.     

High-mass diffraction and Regge behavior of total cross sections

We consider a modified two-component model of particle production in which diffractive excitation into high mass states gives a contribution to K^±p, π^±p and pp total cross sections of sufficient magnitude and with the proper associated threshold to be a possible explanation of deviations of σ_tot from Regge pole model fits at Serpukhov energies. We present tests of the model. for K⁺p scattering by extrapolating σ_tot to National Accelerator Laboratory energies and by calculating the high mass diffraction contribution to the forward peak in inclusive reactions. The consistency of this scheme is discussed in relation to the pomeron intercept and the form of the triple-pomeron coupling.     

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.     

Analyticity and quark-gluon structure of hadron total cross sections

The amplitudes of hadron-hadron forward elastic scattering at high energies are investigated on the basis of analyticity and crossing symmetry. A universal uniformizing variable for them is proposed, and the formulas for crossing-even and crossing-odd amplitudes are derived. The same parameters in these formulas determine the real and imaginary (total cross sections) parts of the amplitudes. The analysis of the parameters determined from experimental data clearly points to the quark-gluon structure of hadron total cross sections. The total cross sections for hyperon-proton scattering are predicted. They are consistent with experimental data and, in particular, with the new SELEX-collaboration measurement σ_tot(Σ^?p).     

Fast-neutron total and scattering cross sections of58Ni

Neutron total cross sections of⁵⁸Ni were measured at 25 keV intervals from 0.9 to 4.5 MeV with 50–100 keV resolutions. Attention was given to self-shielding corrections to the observed total cross sections. Differential elastic- and inelastic-scattering cross sections were measured at 50 keV intervals from 1.35 to 4.0 MeV with 50–100 keV resolutions. Inelastic excitation of levels at 1.458±0.009, 2.462+-0.010, 2.791±0.015, 2.927+-0.012 and 3.059+-0.025 MeV was observed. The experimental results were interpreted in terms of optical-statistical and coupled-channels models.     

Velocity dependence of total Penning ionization cross sections

The velocity dependence of the total Penning ionization cross sections,σ(v), is measured in the thermal relative velocity region, using a time of flight method.σ(v) curves are reported for the collision systems He(2¹ S)/Ar, Kr, Xe, N₂, Hg, He(2³ S)/Ar, Kr, Xe, N₂, Hg, Ne(³ P _{2, 0})/Kr, Hg, and Ar(³ P _{2, 0})/Hg. In a qualitative discussion it is shown that all features of the measuredσ(v) curves may be explained within the frame of the theory of Penning ionization, allowing to extract information on the physical quantities governing the process: on the interaction potentialV(R) and on the transition probabilityW(R). A theoretical calculation for the He(2³ S)/Ar system shows good agreement with our experimentalσ(v) curve. On the basis of the present results earlier data onσ(v), and on absolute cross sections and rate constants obtained at certain relative velocity distributions are discussed.