Dynamics of diffractive dissociation

We describe a QCD based model which incorporates the main properties of the inclusive particle distributions expected for diffractive processes, including the diffractive dissociation at high energies. We study, in turn, the total cross section, $$\sigma _\mathrm{tot}$$ σ tot , the differential elastic, $$d\sigma _\mathrm{el}/dt$$ d σ el / d t , cross section, the dependence of the single proton dissociation cross section, $$\xi d\sigma ^\mathrm{SD}/d\xi $$ ξ d σ SD / d ξ , on the momentum fraction, $$\xi =1-x_L$$ ξ = 1 - x L , lost by the leading proton, the multiplicity distributions in inelastic (non-diffractive) collisions and in the processes of dissociation. Besides this we calculate the mean transverse momenta of the ‘wee partons’ (secondaries) produced in the case of dissociation (that is in the processes with a large rapidity gap) and compare it with that in inelastic interactions.

Proton–proton, pion–proton and pion–pion diffractive collisions at ultrahigh energies

The LHC energies are those at which the asymptotic regime in hadron–hadron diffractive collisions (pp, πp, ππ) might be switched on. Based on results of the Dakhno–Nikonov eikonal model which is a generalization of the Good–Walker eikonal approach for a continuous set of channels, we present a picture for transformation of the constituent quark mode to the black disk one. In the black disk mode [Formula: see text], we have a growth of the logarithm squared type for total and elastic cross-sections, σ tot ~ ln 2 s and σ el ~ ln 2 s and [Formula: see text]-scaling for diffractive scattering and diffractive dissociation of hadrons. The diffractive dissociation cross-section grows as σD ~ ln s, σDD ~ ln s, and their relative contribution tends to zero: σD/σ tot → 0, σDD/σ tot → 0. Asymptotic characteristics of diffractive and total cross-sections are universal, and this results in the asymptotical equality of cross-sections for all types of hadrons (the Gribov universality). The energy scale for switching on the asymptotic mode is estimated for different processes.

Radiolysis of ammonia-containing ices by heavy cosmic rays inside dense molecular clouds

We present experimental studies on the interaction of heavy, highly charged and energetic ions (46 MeV 58Ni13+) with interstellar ammonia-containing (H2O:NH3:CO) ice analog in an attempt to simulate the physical chemistry induced by heavy ion cosmic rays inside dense astrophysical environments. The measurements were performed at the heavy ion accelerator GANIL in Caen, France. In-situ analysis have been performed by a Fourier transform infrared spectrometer. The averaged values for the dissociation cross section of water, ammonia and carbon monoxide are determined and the estimated half life for the studied species inside dense molecular clouds is 2-3 × 106 years. The IR spectra of organic residue produced by the radiolysis have revealed, at room temperature, five bands that are tentatively assigned to vibration modes of the zwitterionic glycine (NH3+CH2COO−).

THREE-BODY COULOMB FINAL-STATE INTERACTION EFFECTS IN THE COULOMB BREAKUP OF LIGHT NUCLEI

Coulomb breakup of a projectile in the Coulomb field of a fully stripped heavy nucleus is at present one of the most popular experimental methods to obtain information on reactions of interest in nuclear astrophysics. Its theoretical interpretation presents, however, considerable difficulties, due to the three-body nature and the infinite range of the Coulomb forces involved. Among the uncertainties affecting present analyses, the possible modification of the dissociation cross-section by three-body Coulomb final-state interactions plays a major role. Various methods which have been proposed to deal with it are briefly reviewed. However, none of them is based on a consistent and mathematically satisfactory quantum mechanical treatment, with the exception of the one proposed recently. The latter, being based on the prior form of the dissociation amplitude, makes use of a genuine three-charged particle wave function for the final state which is an exact solution of the three-body Schrödinger equation, albeit only asymptotically, i.e. for large distances. Nevertheless, interesting conclusion can be drawn concerning the influence of three-body Coulomb final-state interactions on quantities of astrophysical interest.