Hadron-nucleus Collisions Research Articles

Reminiscences of Wit Busza and 41 years of [formula omitted] physics

One of the more memorable (and easiest) proposal to deal with when I served on Bob Wilson’s Program Advisory Committee at NAL (Now Fermilab) from 1972 to 1975 was Proposal-178, “A study of the average multiplicity and multiplicity distributions in hadron–nucleus collisions at high energies”, with only 4 authors, Wit Busza, Jerry Friedman, Henry Kendall and Larry Rosenson, as presented at the PAC meeting by Wit. What I remember was that he discussed only ONE 5 inch photomultiplier with a Cherenkov radiator in the beam to make this measurement of production of charged particles with angles up to 30° in various nuclei, 40 h requested. This turned out to be a “seminal” experiment leading to the Wounded Nucleon and other participant models. Subsequent p(d)+A experiments from the AGS to RHIC, as well as alpha–alpha measurements at the CERN-ISR, will be discussed together with the various ‘participants’ that they revealed.

Formation of multibaryon clusters in collisions of high energy hadrons and nuclei with carbon and neon nuclei

Formation of multibaryon clusters in 4 He + 12 C and 12 C + 12 C collisions at 4.2A GeV/c, and in π- + 12 C and p + 20 Ne collisions at 40 and 300 GeV/c, respectively, is studied using universal binary B algorithm of separation of clusters in 4-velocity space. The masses and widths of multibaryon clusters increase linearly with an increase in the number of protons (np) in a cluster. The dependences of width of clusters on np in π- + 12 C and p + 20 Ne collisions differ noticeably from the corresponding dependences in 4 He + 12 C and 12 C + 12 C collisions. In nucleus–nucleus collisions, the widths of clusters are significantly larger and grow more rapidly, as the number of protons in a cluster increases, as compared to hadron–nucleus collisions. This result is in line with the fact that, in case of identical target nuclei, the degree of "destruction" of a target nucleus is greater in case of nucleus–nucleus collisions as compared to hadron–nucleus collisions. The lifetimes of multibaryon clusters are of the same order of magnitude with those of strongly decaying baryon resonances. The lifetime of clusters decreases with an increase in np.

The Old New Frontier: Studying the CERN-SPS Energy Range with NA61/SHINE

With the Large Hadron Collider entering its third year of granting us insight into the highest collision energies to date, one should nevertheless keep in mind the unexplored physics potential of lower energies. A prime example here is the NA61/SHINE experiment at the CERN Super Proton Synchrotron. Using its large-acceptance hadronic spectrometer, SHINE aims to accomplish a number of physics goals: measuring spectra of identified hadrons in hadron-nucleus collisions to provide reference for accelerator neutrino experiments and cosmic-ray observatories, investigating particle properties in the large transverse-momentum range for hadron+hadron and hadron+nucleus collisions for studying the nuclear modification factor at SPS energies, and measuring hadronic observables in a particularly interesting region of the phase diagram of strongly-interacting matter to study the onset of deconfinement and search for the critical point of strongly-interacting matter with nucleus-nucleus collisions. This contribution shall summarise results obtained so far by NA61/SHINE, as well as present the current status and plans of its experimental programme.

High-energy cosmic ray muons in the Earth’s atmosphere

We present the calculations of the atmospheric muon fluxes at energies 10–107 GeV based on a numerical-analytical method for solving the hadron-nucleus cascade equations. It allows the non-power-law behavior of the primary cosmic ray (PCR) spectrum, the violation of Feynman scaling, and the growth of the total inelastic cross sections for hadron-nucleus collisions with increasing energy to be taken into account. The calculations have been performed for a wide class of hadron-nucleus interaction models using directly the PCR measurements made in the ATIC-2 and GAMMA experiments and the parameterizations of the primary spectrum based on a set of experiments. We study the dependence of atmospheric muon flux characteristics on the hadronic interaction model and the influence of uncertainties in the PCR spectrum and composition on the muon flux at sea level. Comparison of the calculated muon energy spectra at sea level with the data from a large number of experiments shows that the cross sections for hadron-nucleus interactions introduce the greatest uncertainty in the energy region that does not include the knee in the primary spectrum.

Wounded Constituents

The concept of the "wounded" hadronic constituents is formulated. Preliminary estimates indicate that it may help to understand the transverse mass dependence of particle production in hadron-nucleus and nucleus-nucleus collisions.

Number of collisions in the Glauber model and beyond

The so-called number of hadron-nucleus collisions ${n}_{\mathrm{coll}}(b)$ at impact parameter $b$ and its integral value ${N}_{\mathrm{coll}}$, which are used to normalize the measured fractional cross section of a hard process, are calculated within the Glauber-Gribov theory, including the effects of nucleon short-range correlations. The Gribov inelastic shadowing corrections are summed to all orders by employing the dipole representation. Numerical calculations are performed at the energies of the BNL Relativistic Heavy Ion Collider (RHIC) and CERN Large Hadron Collider (LHC). We found that whereas the Gribov corrections generally increase the value of ${N}_{\mathrm{coll}}$, the inclusion of nucleon correlations, acting in the opposite directions, decreases it by a comparable amount. The interplay of the two effects varies with the value of the impact parameter.

Production of multibaryon clusters in hadron-nucleus collisions at high energies

The results obtained by analyzing the production of multibaryon clusters in π−C and p20Ne interactions at momenta of 40 and 300 GeV/c, respectively, are presented.

QCD motivated approach to soft interactions at high energies: Nucleus–nucleus and hadron–nucleus collisions

In this paper we consider nucleus–nucleus and hadron–nucleus reactions in the kinematic region: g A 1 / 3 G 3 P exp ( Δ P Y ) ⩾ 1 and G 3 P 2 exp ( Δ P Y ) < 1 , where G 3 P is the triple Pomeron coupling, g is the vertex of Pomeron nucleon interaction, and 1 + Δ P denotes the Pomeron intercept. We find that in this kinematic region the traditional Glauber–Gribov eikonal approach is inadequate. We show that it is necessary to take into account inelastic Glauber corrections, which cannot be expressed in terms of the nucleon–nucleon scattering amplitudes. We derive the nucleus–nucleus scattering amplitude in the wide range of energies where α P ′ Y ≪ R A 2 , where this amplitude does not depend on the details of the nucleon–nucleon interaction at high energy. In the formalism we present, the only (correlated) parameters that are required to describe the data are Δ P , G 3 P and g. These parameters were taken from our description of the nucleon–nucleon data at high energies Gotsman et al. (2008) [1]. The predicted nucleus modification factor is compared with RHIC Au–Au data at W = 200 GeV . Estimates for LHC energies are presented and discussed.

The multiplicity of particle production from hadron-hadron and nucleus-nucleus interaction

The particle production in hadron-nucleon (h-N), hadron-nucleus (h-A) and nucleus-nucleus (A-A) collisions at high energies are studied in view of the multi-peripheral model. A multi-peripheral T-matrix element is assumed with multi surface parameter that is functionally dependent on the number of particles in the final state and control the kinematical path of the reaction. A Monte Carlo code is designed to simulate events ac-cording to a hypothetical model, the quark structure of the interacting nucleons is consid-ered. The number of possible nucleon collisions inside the target nucleus plays an important role in folding the (h-N) to generate the (h-A) and (A-A) collisions. The predictions of the model give reasonable agreement with the recently examined experimental data.

Nuclear-like effects in proton–proton collisions at high energy

We show that several effects considered nuclear effects are not nuclear in the sense that they do not only occur in nucleus-nucleus and hadron-nucleus collisions but, as well, they are present in hadron-hadron (proton-proton) collisions. The matter creation mechanism in hh, hA and AA collisions is always the same. The pT suppression of particles produced in large multiplicity events compared to low multiplicity events, the elliptic flow and the Cronin effect are predicted to occur in pp collisions at LHC energies as a consequence of the obtained high density partonic medium.

On the shape of a rapid hadron in QCD

We visualize the fundamental property of pQCD: the smaller is the size of the colorless quark–gluon configuration, more rapid is the increase of its interaction with energy. Within the frame of the dipole model we use the kt factorization theorem to generalize the DGLAP approximation and/or leading ln(x0/x) approximation and evaluate the interaction of the quark dipole with a target. In the limit of fixed Q2 and x→0 we find the increase with energy of transverse momenta of quark (antiquark) within the qq¯ pair produced by the strongly virtual photon. The average pt2 is evaluated analytically within the double logarithmic approximation. We demonstrate that the invariant mass2 of the qq¯ pair increases with the energy as 0.7Q2(10−2/x)0.4αsNc/π, for transverse photons, and ∼0.7Q2exp0.36[(αsNc/π)log(10−2/x)]1/2 for longitudinal photons. We found similar pattern of the energy dependence of M2 in the LO DGLAP approximation generalized to account for the kt factorization. We discuss the impact of the found phenomenon on the dependence of the coherence length on the collision energy and demonstrate that in the regime of complete absorption effective shape of the sufficiently energetic hadron (nucleus) has the biconcave form instead of the pancake. We explain that the different representations of chiral symmetry for the central and peripheral collisions would be characteristic property of hadron (nucleus) nucleus collisions at large energies. Some implications of the found phenomena for pp collisions are discussed.

On the mechanisms of cumulative-proton production in high-energy hadron-nucleus and nucleus-nucleus collisions

The importance of studying processes involving cumulative-proton production stems from their direct relation to the formation of multiquark configurations, so-called fluctons, in a nucleus owing to nucleondensity fluctuations in which two or more nucleons occur at a distance shorter than 1 fm from one another. According to [1], multiquark configurations may arise in two different physics patterns. The first, caused by a fluctuation of the target-nucleus density, is referred to as a cold model, while the second, associated with nuclear-matter compression occurring under the effect of an incident hadron or a projectile nucleus and leading to the formation of dense quark bags, is called a hot model. It should be noted that, in early interpretations, the production of cumulative protons was related to the Fermi momenta of nucleons. However, the calculations that took into account the Fermi momentum of nucleons [2] showed that the spectrum of fast ( p> 500 MeV/c) cumulative protons cannot be described in this way. In the present study, we examine new features of the process of cumulative-proton production—in particular, we analyze the behavior of the mean multiplicity of cumulative protons as a function of the charge and mass numbers of the target nucleus. Previously, our group studied [3–5] cumulativeproton production in π −12 С, pС, 4 НеС, СС, 16 Op, and p 20 Ne collisions at primary energies in the range 3–300 GeV and, on the basis of a vast statistical data sample, confirmed the universal regularity that the slope parameter of inclusive cross sections for cumulative protons in the cumulative number β is independent of the primary energy and mass of the incident particle or nucleus. It was shown that the fraction of events involving cumulative-proton production on a carbon nucleus is sensitive to the

Transverse momentum broadening of vector boson production in high energy nuclear collisions

We calculate in perturbative QCD the transverse momentum broadening of vector boson production in high energy nuclear collisions. We evaluate the effect of initial-state parton multiple scattering for the production of the Drell-Yan virtual photon and W/Z bosons. We calculate both the initial- and final-state multiple scattering effect for the production of heavy quarkonia and their transverse momentum broadening in both nonrelativistic QCD and the color evaporation model of quarkonium formation. We find that J/{psi} and {upsilon} broadening in hadron-nucleus collision is close to 2C{sub A}/C{sub F} times the corresponding Drell-Yan broadening, which gives a good description of existing Fermilab data. Our calculations are also consistent with Relativistic Heavy Ion Collider data on J/{psi} broadening in relativistic heavy ion collisions. We predict the transverse momentum broadening of vector boson (J/{psi}, {upsilon}, and W/Z) production in relativistic heavy ion collisions at the Large Hadron Collider and discuss the role of the vector boson broadening in diagnosing medium properties.

Coherent [formula omitted] production—A novel feature at LHC?

Energy dependence of heavy quarkonia production in hadron–nucleus collisions is studied in the framework of the Glauber–Gribov theory. We emphasize a change in the space–time picture of heavy-quark state production on nuclei with energy. Longitudinally ordered scattering of a heavy-quark system takes place at low energies, while with increasing energy it transforms to a coherent scattering of projectile partons on the nuclear target. The characteristic energy scale for this transition depends on masses and rapidities of produced particles. For J/ψ, produced in the central rapidity region, the transition happens at RHIC energies. The parameter-free calculation of J/ψ in dAu collisions is in good agreement with recent RHIC data. We use distributions of gluons in nuclei to predict suppression of heavy quarkonia at LHC.

On the possibility of describing the multiplicity distribution of protons in high-energy hadron-nucleus collisions within a three-step interaction model

On the possibility of describing the multiplicity distribution of protons in high-energy hadron-nucleus collisions within a three-step interaction model

J/ψsuppression and the decrease of nuclear absorption with increasing energy

In the framework of the Glauber-Gribov field theory in the eikonal approximation, we show that in hadron-nucleus collisions in the high-energy limit and under specific conditions, the rescattering contributions to the $J/\ensuremath{\psi}$ production cross section vanish, leading to an ${A}^{1}$ dependence on the atomic number $A$-except for nuclear effects in the nucleus structure function, the so-called shadowing. We show that the data from the BNL Relativistic Heavy Ion Collider on $J/\ensuremath{\psi}$ production in $d$-Au collisions can be described with nuclear shadowing alone $({\ensuremath{\sigma}}_{\mathrm{abs}}=0$). The corresponding results for $\mathrm{Au}\text{\ensuremath{-}}\mathrm{Au}$ collisions are also presented and compared with available data.

On the production of cumulative protons in high-energy hadron-nucleus and nucleus-nucleus collisions

On the production of cumulative protons in high-energy hadron-nucleus and nucleus-nucleus collisions

Meson cascade in the atmosphere, uncertainties in calculating the fluxes of high-energy muons, and data of direct measurements

A new calculation of the atmospheric fluxes of cosmic-ray hadrons and muons in the energy range 10–104 GeV is performed on the basis of the method for solving nuclear-cascade equations with allowance for a nonscaling behavior of inclusive hadron-production cross sections, the growth of cross sections for inelastic hadron-nucleus collisions with increasing energy, and a non-power-law character of the primary spectrum. The fluxes of secondary cosmic rays at various levels in the atmosphere are calculated for three models of the spectrum and composition of primary cosmic rays. The effect of uncertainties in the spectrumand composition of primary cosmic rays on the flux of atmosphericmuons and their charge ratio at sea level is investigated. The calculated energy spectra of muons at sea level are compared with the results of previous experiments and the results of recent measurements performed by means of the L3 + Cosmic and CosmoALEPH spectrometers, as well as with the results of other calculations.

Final state interactions and hadron quenching in cold nuclear matter

I examine the role of final state interactions in cold nuclear matter in modifying hadron production on nuclear targets with leptonic or hadronic beams. I demonstrate the extent to which available experimental data in electron-nucleus collisions can give direct information on final state effects in hadron-nucleus and nucleus-nucleus collisions. For hadron-nucleus collisions, a theoretical estimate based on a parton energy loss model tested in lepton-nucleus collisions shows a large effect on midrapidity hadrons at fixed target experiments. At energies currently available at the BNL Relativistic Heavy Ion Collider, the effect is large for negative rapidity hadrons but mild at midrapidity. This final state cold hadron quenching needs to be taken into account in jet tomographic analysis of the medium created in nucleus-nucleus collisions.

Strangeness conservation and pair correlations of neutral kaons with close momenta produced in inclusive multiparticle processes

The phenomenological structure of inclusive cross-sections of the production of two neutral K-mesons in hadron-hadron, hadron-nucleus and nucleus-nucleus collisions is investigated taking into account the strangeness conservation in strong and electromagnetic interactions. The relations describing the dependence of the correlations of two short-lived and two long-lived neutral kaons K S 0 K S 0 , K L 0 K L 0 and the correlations of “mixed” pairs K S 0 K L 0 at small relative momenta upon the space-time parameters of the generation region of K 0 and \( \bar K \) 0- mesons, which involve the contributions of Bose-statistics and S-wave strong final-state interaction, have been obtained. It is shown that under the strangeness conservation the correlation functions of the pairs K S 0 K S 0 and K L 0 K L 0 , produced in the same inclusive process, coincide, and the difference between the correlation functions of the pairs K S 0 K S 0 and K S 0 K L 0 is conditioned by the production of the pairs of non-identical neutral kaons K 0 \( \bar K \) 0.