Minijet Production Research Articles

Multiparticle transverse correlation functions and minijet production in sqrt s=1.8 TeV pp-bar collisions in a Monte Carlo model.

We propose and demonstrate that multiparticle transverse correlation functions are promising observables of detecting minijet production in s=1.8 TeV pp¯ collisions.Received 7 September 1995DOI:https://doi.org/10.1103/PhysRevD.54.3659©1996 American Physical Society

Multiparton interactions and production of minijets in high energy hadronic collisions.

We discuss the inclusive cross section to produce two minijets with a large separation in rapidity in high energy hadronic collisions. The contribution to the inclusive cross section from the exchange of a BFKL Pomeron is compared with the contribution from the exchange of two BFKL Pomerons, which is induced by the unitarization of the semihard interaction. The effect of the multiple exchange is studied both as a function of the azimuthal correlation and as a function of the transverse momentum of the observed minijets. \textcopyright{} 1995 The American Physical Society.

HIJING 1.0: A Monte Carlo program for parton and particle production in high energy hadronic and nuclear collisions

Based on QCD-inspired models for multiple jets production, we developed a Monte Carlo program to study jet and the associated particle production in high energy pp, pA and AA collisions. The physics behind the program which includes multiple minijet production, soft excitation, nuclear shadowing of parton distribution functions and jet interaction in dense matter is briefly discussed. A detailed description of the program and instructions on how to use it are given.

SIBYLL: An event generator for simulation of high energy cosmic ray cascades.

We describe the physical basis and some applications of an efficient event generator designed for Monte Carlo simulations of atmospheric cascades at ultrahigh energies. The event generator (sibyll) incorporates many features of the Lund programs, but emphasizes the fragmentation region and the production of minijets. A consistent treatment of hadron-hadron and hadron-nucleus interactions is emphasized. Examples of applications are the calculation of coincident muons observed in deep underground detectors and the simulation of the longitudinal development of air shower components in the atmosphere.

Minijet production at small x

Soft pomeron exchange at high energy includes minijet production at central rapidity values. This predicts copious production of minijets in deep inelastic scattering at small x, which is closely related to the fact that νW 2 exhibits Regge behaviour. It helps to explain also how the integrated inclusive cross-section for minijet production in γp or pp collisions can be much greater than the total cross-section.

Color conductivity and evolution of the minijet plasma.

The early evolution of the gluon plasma produced in ultrarelativistic nuclear collisions is investigated via chromoviscous hydrodynamics. The initial conditions are determined by perturbative QCD minijet production including nuclear shadowing of the parton distributions. The analog of Ohmic heating is shown to damp rapidly any chromoelectric fields in the plasma. In the context of the flux tube models for beam jet fragmentation this damping is shown to suppress pair production processes, decrease transverse energy production, and reduce the quark-gluon chemical equilibration rate. Possible implications for dilepton production are noted.

Minijets and the behavior of inelasticity at high energies.

We present an extension of the interacting gluon model, used previously to calculate inelasticities and leading particle spectra in hadronic and nuclear collisions, which incorporate also the production of minijets. As a result we get inelasticity slowly increasing towards some limited value.

Studying minijets via the pT dependence of two-particle correlation in azimuthal angle phi.

Following any previous proposal that two-particle correlation functions can be used to resolve the minijet contribution to particle production in minimum biased events of high-energy hadronic interactions, I study the ${\mathit{p}}_{\mathit{T}}$ and energy dependence of the correlation. Using the higing Monte Carlo model, it is found that the correlation c(${\mathrm{\ensuremath{\varphi}}}_{1}$,${\mathrm{\ensuremath{\varphi}}}_{2}$) in the azimuthal angle \ensuremath{\varphi} between particles with ${\mathit{p}}_{\mathit{T}}$>${\mathit{p}}_{\mathit{T}}^{\mathrm{cut}}$ resembles two back-to-back jets as ${\mathit{p}}_{\mathit{T}}^{\mathrm{cut}}$ increases at high colliding energies due to minijet production. It is shown that c(0,0)-c(0,\ensuremath{\pi}), which is related to the relative fraction of particles from minijets, increases with energy. The background of the correlation for fixed ${\mathit{p}}_{\mathit{T}}^{\mathrm{cut}}$ also grows with energy due to the increase of multiple minijet production. Application of this analysis to the study of jet quenching in ultrarelativistic heavy-ion collisions is also discussed.

Coherent nuclear diffractive production of minijets — illuminating color transparency

The cross section for coherent nuclear processes in which an incident meson or photon dissociates diffractively into two jets of high relative transverse momentum (between about 1 and 3 GeV/ c) is found to be proportional in QCD to A 2 in a wide kinematical region. The leading correction to this is a significant positive term ∝ A 7 3 caused by nuclear multiple scattering. We find also that shadowing of hard diffractive processes reappears as a leading twist effect in the TeV energy range.

Diffractive dissociation in the minijet model.

We use a Good-Walker model for diffraction to study the high-energy behavior of the diffractive cross sections in the minijet model. We find that the high-energy behavior of the diffractive cross section, like the elastic cross section, is determined by minijet production. Using a fit to low-energy and collider data we make predictions for the behavior of the diffractive cross sections at high energy.

Rates for dilepton production at RHIC and LHC between the [formula omitted] and υ are big

We study the problem of dilepton production in heavy ion collisions at RHIC and LHC energies. We find that, due to the expected enhanced multiplicities and larger transverse momenta of hadrons arising from minijet production, the dilepton production rate dramatically increases. We consider two extreme limits: a thermalized, hydrodynamically expanding quark-gluon plasma and a free-streaming, non-interacting gas of quarks and gluons. In both cases we find that the dilepton rate arising from electromagnetic annihilations of the quarks is significantly larger than that of the Drell-Yan process for dilepton masses between the J Ψ and the υ.

Dynamical versus decay photons in A + A collisions at √ s=200 A GeV

Dynamical photons produced via qg→q γ and q q → gγ processes in an equilibrated quark-gluon plasma are calculated in a hydrodynamic model for a wide range of initial conditions in ultra-relativistic heavy ion collisions. Electromagnetic decay photons are calculated via the Monte Carlo HIJING model including multiple minijet production. If rapid thermalization occurs and the decay photons can be subtracted with high efficiency, the dynamical photons in the range p T >GeV may serve as a useful probe of the initial conditions in the plasma.

Reexamining the jet contribution to the photoproduction cross section.

We reexamine the contribution of minijet production to the total photoproduction cross section. We show that previous calculations showing a dramatic increase of the cross section with energy have overestimated the minijet contribution at very high energies (${\mathit{E}}_{\ensuremath{\gamma}}$>${10}^{6}$ GeV). We present revised quantitative predictions. Understanding the high energy behavior of the photoproduction cross section should be a high priority as it is dictated by the gluon structure of high energy photons which will be studied in detail at the DESY ep collider HERA. It is also essential for understanding the development of extensive air showers.

HIGING: A Monte Carlo model for multiple jet production in pp, pA, and AA collisions.

Combining perturbative-QCD inspired models for multiple jet production with low ${p}_{T}$ multistring phenomenology, we develop a Monte Carlo event generator hijing to study jet and multiparticle production in high energy $\mathrm{pp}$, $\mathrm{pA}$, and $\mathrm{AA}$ collisions. The model includes multiple minijet production, nuclear shadowing of parton distribution functions, and a schematic mechanism of jet interactions in dense matter. Glauber geometry for multiple collisions is used to calculate $\mathrm{pA}$ and $\mathrm{AA}$ collisions. The phenomenological parameters are adjusted to reproduce essential features of $\mathrm{pp}$ multiparticle production data for a wide energy range ($\sqrt{s}=5\ensuremath{-}2000$ GeV). Illustrative tests of the model on $p+A$ and light-ion $B+A$ data at $\sqrt{s}=20$ GeV/nucleon and predictions for Au+Au at energies of the BNL Relativistic Heavy Ion Collider ($\sqrt{s}=200$ GeV/nucleon) are given.

Co-planar events, QCD jets and diffractive dissociations

We propose an interpretation of co-planar γ-family events observed in mountain emulsion chambers, based on a systematic Monte Carlo simulation of the atmospheric propagation of cosmic ray particles at energies 10 15–10 17 eV with an interaction model that includes QCD-jet and mini-jet production and diffractive dissociation. Our analysis indicates that the diffractive process plays an important role in the formation of the co-planar structure in γ-family events with visible energies ΣE γ =100−400 TeV. The QCD jets are found not to be the major source of the co-planar structure at primary energies ∼10 16 eV, although they make a significant contribution to the inelastic cross section and are responsible for the double-core configuration.

Role of multiple minijets in high-energy hadronic reactions.

The multiplicity distributions of charged particles in high-energy hadron collisions including the production of multiple minijets are considered in the framework of the eikonal formalism. Large-multiplicity events at high energies are found to be dominated by the production of many jets with 2{le}{ital P}{sub {ital T}}{le}4 GeV. The contributions from larger-{ital P}{sub {ital T}} minijets become prevailing for high-multiplicity fluctuations in narrow rapidity intervals.

Multiplicities and minijets at the Tevatron

We show that the KNO scaling violation in the parton branching model is due to the increase of the gluon contribution to the hadronic multiplicities. This results in the widening of the probability distribution in agreement with experimental data. We also find excellent agreement with experimental data on multiplicity moments in different rapidity regions. We present theoretical predictions for the multiplicities and moments at the Tevatron energies. We also show that QCD minijet cross section with p T min of order 3 GeV and K factor of order 2 gives a very good description of the minijet data. We extrapolate our theoretical predictions to Tevatron energies indicating that measurements of the minijet production at these energies will have some resolving power to distinguish between different sets of structure functions.

Minijets and their consequences for collisions of heavy nuclei

The UA1 data for minijets are used to estimate minijet production in nucleus-nucleus collisions at collider energies. The average number N ̄ of minijets and the average transverse energy E ̄ t that they carry off are expected to be proportional to A 4 3 . For minijets with pt > ptmin at √ snn = 200 GeV, N ̄ is proportional to p −4 min and E ̄ t to p −3 tmin. For UU collisions at RHIC, N ̄ ≈ 100 and E ̄ T ≈ 350 GeV . The minijet will produce features in the final state similar to those expected from a thermalised quark-gluon plasma (increases in multiplicity and < pt > of the hadrons, and of strangeness and charm), and will themselves contribute to the formation of such a plasma.

Minijet production in high-energy nucleus-nucleus collisions.

Uranium-uranium collisions at the energy of the Brookhaven Relativistic Heavy-Ion Collider (100 + 100 GeV per nucleon) are predicted to produce an average of nearly 100 jets with ${p}_{T}&gt;3$ GeV. These jets will on average carry of 70 GeV of transverse energy ${E}_{T}$ per unit rapidity. Central collisions produce more transverse energy than this; the ${E}_{T}$ distribution extends up to about $\frac{(5{A}^{\frac{4}{3}} {\mathrm{GeV}}^{4})}{{p}_{Tmin}^{3}}$ per unit rapidity, which is 4 times the average. It is estimated that the minijets are likely to undergo further collisions and become thermalized.

Semi-hard QCD: Minijets and elastic scattering

Starting from the QCD calculation of the amplitude for semi-hard interactions we establish a quantitative correlation between the growth of the cross section for minijet production and the changes in the pp̄ elastic differential cross section between ISR and Spp̄S collider energies. The fact that the semi-hard amplitude is central plays an essential role. The predicted behaviour for σ tot, σ tot/ σ tot, ϱ and d σ/d t at higher energies is presented.