Inelastic Proton-proton Interactions Research Articles

A New Review of Excitation Functions of Hadron Production in pp Collisions in the NICA Energy Range

Data on hadron multiplicities from inelastic proton-proton interactions in the energy range of the NICA collider have been compiled. The compilation includes recent results from the NA61/SHINE and NA49 experiments at the CERN SPS accelerator. New parameterizations for excitation functions of mean multiplicities $$\left\langle {{{\pi }^{ \pm }}} \right\rangle $$, $$\left\langle {{{K}^{ \pm }}} \right\rangle $$, $$\left\langle {K_{S}^{0}} \right\rangle $$, $$\left\langle \Lambda \right\rangle $$, $$\left\langle p \right\rangle $$, $$\left\langle {\bar {p}} \right\rangle $$ are obtained in the region of collision energies $$3 < \sqrt {{{s}_{{NN}}}} < 31$$ GeV. The energy dependence of the particle yields, as well as variation of rapidity and transverse momentum distributions are discussed. A standalone algorithm for hadron phase space generation in $$pp$$ collisions is suggested and compared to model predictions using an example of the PHQMD generator. The investigation has been performed at the Laboratory of High Energy Physics, JINR.

Statistical hadron-gas treatment of systems created in proton-proton interactions at energies available at the CERN Super Proton Synchrotron

We analyze the newest data from the NA61/SHINE collaboration which, in addition to previous results on pions and kaons, include mean multiplicities of $p$, $\Lambda$, and $\phi$-mesons produced in inelastic proton-proton (p+p) interactions at $\sqrt{s_{NN}}=6.3-17.3$~GeV. The canonical ensemble formulation of the ideal hadron resonance gas (HRG) model is used with exact conservation of net baryon number $B=2$, electric charge $Q=2$, and strangeness $S=0$. The chemical freeze-out parameters in p+p interactions are obtained and compared to those in central nucleus-nucleus collisions. Several features of p+p interactions at the CERN SPS within a statistical model are studied: 1) the inclusion of the $\phi$-meson yields in thermal fits worsens significantly the fit quality; 2) the data show large event-by-event multiplicity fluctuations in inelastic p+p interactions which can not be explained by a single fireball described by a statistical model; 3) the fits within the canonical ensemble formulation of HRG do not give any improvement over the fits within the grand canonical ensemble formulation, i.e., there are no indications for existence of a single statistical system in p+p inelastic interactions in the considered energy range.

ACCELERATION OF THERMAL PROTONS BY GENERIC PHENOMENOLOGICAL MECHANISMS

We investigate heating and acceleration of protons from a thermal gas with a generic diffusion and acceleration model, and subject to Coulomb scattering and energy loss, as was carried out in Petrosian & East (2008) for electrons. As protons gain energy their loss to electrons becomes important. Thus, we need to solve the coupled proton-electron kinetic equation. We numerically solve the coupled Fokker-Plank equations and computes the time evolution of the spectra of both particles. We show that this can lead to a quasi-thermal component plus a high energy nonthermal tail. We determine the evolution of nonthermal tail and the quasi-thermal component. The results may be used to explore the possibility of inverse bremsstrahlung radiation as a source of hard X-ray emissions from hot sources such as solar flares, accretion disk coronas and the intracluster medium of galaxy clusters. We find that emergence of nonthermal protons is accompanied by excessive heating of the entire plasma, unless the turbulence needed for scattering and acceleration is steeper than Kolmogorov and the acceleration parameters, the duration of the acceleration, and/or the initial distributions are significantly fine-tuned. These results severely constraint the feasibility of nonthermal inverse bremsstrahlung process producing hard X-ray emissions. However the nonthermal tail may be the seed particles for further re-acceleration to relativistic energies, say by a shock. In the Appendix we present some tests of the integrity of the algorithm used and present a new formula for the energy loss rate due to inelastic proton-proton interactions.

System-size and energy dependence of particle momentum spectra: The UrQMD analysis ofp+pand Pb + Pb collisions

The UrQMD transport model is used to study a system-size and energy dependence of the pion production in high energy collisions. New data of the NA61/SHINE Collaboration on spectra of negatively charged pions in proton-proton interactions at SPS energies are considered. These results are compared with the corresponding data of the NA49 Collaboration in central Pb+Pb collisions at the same collision energies per nucleon. Mean pion multiplicity per participant nucleon, inverse slope parameter of the transverse momentum spectra, and width of rapidity distribution are investigated. A role of isospin effects is discussed. We find that the UrQMD model predicts a non-monotonous behavior of mean transverse mass with collision energy for positively charged pions at the mid-rapidity in inelastic proton-proton interactions. This will be checked soon experimentally by NA61/SHINE Collaboration.

Forward-backward correlations and charged-particle azimuthal distributions in pp interactions using the ATLAS detector

Abstract Using inelastic proton-proton interactions at $ \sqrt {s} = 900 $ GeV and 7 TeV, recorded by the ATLAS detector at the LHC, measurements have been made of the correlations between forward and backward charged-particle multiplicities and, for the first time, between forward and backward charged-particle summed transverse momentum. In addition, jet-like structure in the events is studied by means of azimuthal distributions of charged particles relative to the charged particle with highest transverse momentum in a selected kinematic region of the event. The results are compared with predictions from tunes of the pythia and herwig++ Monte Carlo generators, which in most cases are found to provide a reasonable description of the data.

J/ψproduction in nuclear collisions

Data on J/psi production in inelastic proton-proton, proton-nucleus and nucleus-nucleus interactions at 158 A GeV are analyzed and it is shown that the ratio of mean multiplicities of J/psi mesons and pions is the same for all these collisions. This observation is difficult to understand within current models of J/psi production in nuclear collisions based on the assumption of hard QCD creation of charm quarks.

A sensitive test of QCD from parton-parton scattering at the ISR

Production of jets with fast leading fragments has been studied in deep inelastic proton-proton interactions using the Split Field Magnet detector at the CERN ISR. The kinematics of the underlying parton processes is determined on an event-by-event basis. Parton scattering amplitudes are extracted for scattering angles, Θ ∗, in the interval −0.4 < cos Θ ∗ < 0.9 . The data which are known to be dominated by quark gluon scattering, agree with predictions from lowest order QCD, while e.g. an abelian theory can be excluded.

Interpretation of Highly Intelastic Proton-Proton Interactions at 10, 20, and 30 BeV/c

A phenomenological analysis of the proton spectra resulting from inelastic proton-proton interactions is presented which suggests the existence of a bremsstrahlung-type process of pion production for highly inelastic collisions. A relation $\overline{n}=\frac{{{p}_{0}}^{*}{sin\ensuremath{\theta}}^{*}}{0.4}$ is found between the implied average number of produced pions $\overline{n}$, the c.m. angle of scatter of the proton ${\ensuremath{\theta}}^{*}$, and the c.m. incident-proton momentum ${{p}_{0}}^{*}$. A simple expression for the differential cross section for secondary protons yields excellent agreement with data over a wide range of angle, momenta, and incident-proton momenta.

Analysis of inelastic proton-proton interactions in the 1 to 10 GeV energy range

Different experimental spectra relevant to inelastic protonproton interactions, at incident energies between 1 and 10 GeV, are compared with the predictions of the one-pion-exchange (OPE) model, by taking into account the production of one and two pions. This analysis gives a further confirmation of the validity of the OPE model below 3 GeV; with increasing energy, it is found that the model deteriorates rapidly, and that other effects have to be taken into account. However, the behaviour of the spectra at high energy seems to depend critically on the isospin of the exchanged system, and may be difficult to describe in terms of the pictures currently used for high-energy inelastic interactions.

Analysis of inelastic proton-proton interactions in the 1 to 10 GeV energy range

Different experimental spectra relevant to inelastic proton-proton interactions, at incident energies between 1 and 10 GeV, are compared with the predictions of the one-pion-exchange (OPE) model, by taking into account the production of one and two pions. This analysis gives a further confirmation of the validity of the OPE model below 3 GeV; with increasing energy, it is found that the model deteriorates rapidly, and that other effects have to be taken into account. However, the behaviour of the spectra at high energy seems to depend critically on the isospin of the exchanged system, and may be difficult to describe in terms of the pictures currently used for high-energy inelastic interactions.

Proton-proton collisions at 3.5 GeV

Ilford G-5 emulsions were exposed to an external, 3.5 GeY proton beam of the Berkeley Bevatron. A total of 1200 nuclear interactions of beam protons was located, of which 128 were identified as protonproton collisions. Multiple scattering, blob density, range and angle measurements were employed to determine the cross-sections for elastic and inelastic interactions as well as the identities and center-of-mass system momenta and scattering angles of secondaries from inelastic proton-proton interactions. This analysis indicates a cross-section of (8.0±2.4) mb for elastic events, (24.1±2.9) mb for two-prong inelasitc events, (7.9±1.4)mb for four-prong events and (0.6±0.3) mb for sixprong events. The mean charged pion multiplicity in inelastic interactions is 1.5±0.2 and corresponds to an average degree of inelasticity of 0.45 ±0.06. Center-of-mass system angular distributions of charged secondaries from inelastic events display a peaking for small scattering angles which is most pronounced for protons and pions from events with low secondary multiplicity. Momentum and transverse momentum distributions of secondary protons and pions from inelastic events are presented and compared with the results at other energies. The angular distribution of elastically scattered protons is found to be in fair agreement with that predicted by a uniform optical model of radius 1.25-10-13 cm and opacity 0.66.