No Arabic abstract
A brief historical review is made of the hadron-hadron (hh) total cross section and hadron-nucleus absorption cross section measurements, made mainly at high energy proton synchrotrons. Then I shall discuss low p_tprocesses, including diffraction processes and fragmentation of nuclei in nucleus-nucleus collisions. Nucleus-nucleus collisions at higher energy colliders are then considered, mainly in the context of the search for the gluon quark plasma. Conclusions and a short discussion on perspectives follow.
We analyze the self-similarity approach applied to study the hadron production in p-p and A-A collisions. This approach allows us to describe rather well the ratio of the proton to anti-proton yields in A-A collisions as a function of the energy at a wide range from a few GeV to a few TeV. We suggest a modification of this approach to describe rather well the inclusive spectra of hadrons produced in $pp$ collisions at different initial energies from the AGS to LHC.
The hadron inclusive spectra in pp collisions at high energies are analyzed within a soft QCD model, namely the quark-gluon string model. In addition to the sea quark distribution in the incoming proton we consider also the unintegrated gluon distribution that has an increasing behaviour when the gluon transverse momentum grows. It leads to an increase of the inclusive spectra of hadrons and their multiplicity in the central rapidity region of pp collision at LHC energies.
We study the effect of strong longitudinal color fields (SCF) in p+p reactions up to Large Hadron Collider energies in the framework of the HIJING/BBbar v2.0 model that combines (collinear factorized) pQCD multiple minijet production with soft longitudinal string excitation and hadronization. The default vacuum string tension, kappa0 = 1 GeV/fm, is replaced by an effective power law energy dependent string tension, that increases monotonically with center-of-mass energy. The exponent 0.06 is found sufficient to reproduce well the energy dependence of multiparticle observables in RHIC, Tevatron, as well as recent LHC data. This exponent is found to be only half of that predicted by the Color Glass Saturation model, lambda(CGC)=0.115, where gluon fusion multiparticle production mechanisms are assumed. In HIJING/BBbar v2.0, the rapid growth of central-rapidity density with energy is due to the interplay of copious minijet production and increasing SCF contributions. The large (strange)baryon-to-meson ratios measured at Tevatron energies are well described. A significant enhancement of these ratios is predicted up to the highest LHC energy (14 TeV). The effect of JJbar loops and SCF on baryon-anti-baryon asymmetry and its relation to baryon number transport is also discussed.
In this article, we will present a systematic analysis of transverse momentum spectra of the strange hadron in different multiplicity events produced in pp collision at $sqrt{s}$ = 7 TeV, pPb collision at $sqrt{s_{NN}}$ = 5.02 TeV and PbPb collision at $sqrt{s_{NN}}$ = 2.76 TeV. The differential freeze out scenario of strange hadron $K^{0}_{s}$ assumed while analyzing the data using a Tsallis distribution which is modified to include transverse flow. The $p_{T}$ distributions of strange hadron in different systems are characterized in terms of the parameters namely, Tsallis temperature ($T$), power ($n$) and average transverse flow velocity ($beta$).
Parton distribution functions (PDFs) describe the structure of hadrons as composed of quarks and gluons. They are needed to make predictions for short-distance processes in high-energy collisions and are determined by fitting to cross section data. We review definitions of the PDFs and their relations to high-energy cross sections. We focus on the PDFs in protons, but also discuss PDFs in nuclei. We review in some detail the standard statistical treatment needed to fit the PDFs to data using the Hessian method. We discuss tests that can be used to critically examine whether the assumptions are indeed valid. We also present some ideas of what one can do in the case that the tests indicate that the assumptions fail.