Considerations concerning diffraction scattering in quantum chromodynamics

https://cds.cern.ch/record/180568/files/198710040.pdf

The real part of the proton-antiproton elastic scattering amplitude at the centre of mass energy of 546 GeV

https://cds.cern.ch/record/251792/files/ppe-93-115.pdf

A precise measurement of the real part of the elastic scattering amplitude at the SppS

Data on antiproton-proton cross sections at the c.m. energies 200 and 900 GeV are presented. The data were obtained at the CERN antiproton-proton Collider operated in a new pulsed mode in which the same beams were accelerated and decelerated between beam energies of 450 and 100 GeV. The properties of the machine determine the ratio of the luminosities at the two energies to about 1% and thus an accurate measurement of the ratioR of the inelastic cross sections could be made. We findR (=σ900/σ200)=1.20±0.01±0.02, where the first error is statistical and the second systematic. Interpolating existing data to estimateσine1(200 GeV) this measurement ofR leads toσine1(900 GeV)=50.3+0.4+1.0 mb. Using an extrapolated value ofσe1/σtot we estimate the total cross section at 900 GeV to be 65.3±0.7±1.5 mb. Both the inelastic and total cross sections are compatible with a ln2s dependence. Comparisons are made with different fits to the total cross section energy dependence.

/pdf/antiproton-proton-cross-sections-at-200-and-900-gev-c-m-45iv8mepem.pdf

Antiproton-proton cross sections at 200 and 900 GeV c.m. energy

We discuss various ideas on the nonperturbative vacuum structure in QCD. The stochastic vacuum model of Dosch and Simonov is presented in some detail. We show how this model produces confinement. The model incorporates the idea of the QCD vacuum acting like a dual superconductor due to an effective chromomagnetic monopole condensate. We turn then to high energy, small momentum transfer hadron-hadron scattering. A field-theoretic formalism to treat these reactions is developed, where the basic quantities governing the scattering amplitudes are correlation functions of light-like Wegner-Wilson lines and loops. The evaluation of these correlation functions with the help of the Minkowskian version of the stochastic vacuum model is discussed. A further surprising manifestation of the nontrivial vacuum structure in QCD may be the production of anomalous soft photons in hadron-hadron collisions. We interpret these photons as being due to “synchrotron radiation from the vacuum”. A duality argument leads us from there to the expectation of anomalous pieces proportional to (Q 2)1/6 in the electric form factors of the nucleons for small Q 2. Finally we sketch the idea that in the Drell-Yan reaction, where a quark-antiquark pair annihilates with the production of a lepton pair, a “chromodynamic Sokolov-Ternov effect” may be at work. This leads to a spin correlation of the q \(\bar q\) pair, observable through the angular distribution of the lepton pair.

Roland Henzi

Papers

On the validity of Martin's real-part formula