Target excitation-dependent erratic fluctuation of pions in hadron–nucleus interactions

In this paper we studied the target excitation dependence of erratic behavior of rapidity gaps in p–AgBr interactions at 400 GeV/c and π−–AgBr interactions at 200 and 350 GeV/c. We estimated the entropy-like quantity Sq. The study reveals a positive indication of the erratic nature of event-to-event fluctuations in relativistic hadron–nucleus interactions, and the fluctuation pattern depends on the degree of target excitation for all the interactions.

Double diffraction at zero impact parameter

Protons may sometimes have the configuration of a compact diquark, separated transversely from the quark by a string. If both protons in a collision have this form, the strings may be parallel, giving final states with high multiplicity, ellipticity and a ridge structure, or transverse, with leading protons and (sometimes) rapidity gaps. Simple considerations lead one to expect, at [Formula: see text], central masses in the few GeV /c2 range, appropriate for glueball states.

Double pomeron exchange at the CERN Intersecting Storage Rings and $Sp\bar{p}S$ Collider

The CERN Intersecting Storage Rings, with [Formula: see text] from 22 GeV to 63 GeV and [Formula: see text], allowed the first observations of p + p → p + X + p with two leading protons (xF > 0.95) or two rapidity gaps Δy > 3. Studies of the central hadronic system (X) were made to search for glueballs, finding f0 and f2 resonances, and to advance our understanding of hadronic diffraction. I review the experiments, not including those at the Split Field Magnet (SFM) facility covered elsewhere in this volume. Some double pomeron exchange studies at the CERN [Formula: see text] Collider are also covered.