Hadronic Cascade Research Articles

PACIAE model predictions for Pb+Pb collisions at LHC compared to the Au+Au collisions at RHIC

The parton and hadron cascade model, PACIAE, is employed to simulate the 0–6, 0–10, 15–25, and 35–45% most central Au+Au collisions at , 62.4, 130, and 200 GeV and the 0–10% most central Pb+Pb collisions at GeV. The calculated charged multiplicity and the charged particle transverse momentum distribution, pseudorapidity distribution and extended longitudinal scaling for Au+Au collisions agree with the corresponding PHOBOS data. Thus the above observables calculated for Pb+Pb collisions would be a reasonable prediction.

Reconstruction of hadronic cascades in large-scale neutrino telescopes

A strategy that allows for the reconstruction of the direction and energy of hadronic cascades is presented, as well as the preliminary results from corresponding simulation studies of the ANTARES twelve string detector. The analysis techniques are of very generic nature and can thus be easily applied for large-scale neutrino telescopes, such as KM3NeT.

Femtoscopy in relativistic heavy ion collisions and its relation to bulk properties of QCD matter

By using a viscous hydrodynamic model coupled to a hadronic cascade code, numerous features of the dynamics and equilibrium properties are explored for their impact on femtoscopic measurements. The equation of state, viscous parameters, and initial conditions are investigated. We find that femtoscopy is affected by numerous model features at the 10% level and that by including features and adjusting unknown parameters, one can explain experimental source size measurements to better than 10%.

Fully integrated transport approach to heavy ion reactions with an intermediate hydrodynamic stage

We present a coupled Boltzmann and hydrodynamics approach to relativistic heavy ion reactions. This hybrid approach is based on the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) transport approach with an intermediate hydrodynamical evolution for the hot and dense stage of the collision. Event-by-event fluctuations are directly taken into account via the nonequilibrium initial conditions generated by the initial collisions and string fragmentations in the microscopic UrQMD model. After a (3+1)-dimensional ideal hydrodynamic evolution, the hydrodynamical fields are mapped to hadrons via the Cooper-Frye equation and the subsequent hadronic cascade calculation within UrQMD proceeds to incorporate the important final state effects for a realistic freeze-out. This implementation allows us to compare pure microscopic transport calculations with hydrodynamic calculations using exactly the same initial conditions and freeze-out procedure. The effects of the change in the underlying dynamics--ideal fluid dynamics versus nonequilibrium transport theory--is explored. The freeze-out and initial state parameter dependencies are investigated for different observables. The time evolution of the baryon density and particle yields are also discussed. We find that the final pion and proton multiplicities are lower in the hybrid model calculation owing to the isentropic hydrodynamic expansion whereas the yields for strange particles are enhanced owing to the localmore » equilibrium in the hydrodynamic evolution. The results of the different calculations for the mean transverse mass excitation function, rapidity, and transverse mass spectra for different particle species at three different beam energies are discussed in the context of the available data.« less

Hadronic dissipative effects on transverse dynamics at RHIC

We simulate the dynamics of Au+Au collisions at the relativistic heavy ion collider (RHIC) with a hybrid model that treats the quark–gluon plasma macroscopically as an ideal fluid, but models the hadron resonance gas microscopically using a hadronic cascade. We find that much of the mass-ordering pattern for v2(pT) observed at RHIC is generated during the hadronic stage due to build-up of additional radial flow. We also find that the mass-ordering pattern is violated for ϕ mesons due to small interaction cross section in the hadron resonance gas.

Mass ordering of differential elliptic flow and its violation for ϕ mesons

We simulate the dynamics of Au+Au collisions at the Relativistic Heavy Ion Collider (RHIC) with a hybrid model that treats the dense early quark-gluon plasma (QGP) stage macroscopically as an ideal fluid but models the dilute late hadron resonance gas (HG) microscopically using a hadronic cascade. By comparing with a pure hydrodynamic approach we identify effects of hadronic viscosity on the transverse momentum spectra and differential elliptic flow v{sub 2}(p{sub T}). We investigate the dynamical origins of the observed mass ordering of v{sub 2}(p{sub T}) for identified hadrons, focusing on dissipative effects during the late hadronic stage. Within our approach, we find that, at RHIC energies, much of the finally observed mass splitting is generated during the hadronic stage, due to buildup of additional radial flow. The {phi} meson, having a small interaction cross section, does not fully participate in this additional flow. As a result, it violates the mass-ordering pattern for v{sub 2}(p{sub T}) that is observed for other hadron species. We also show that the early decoupling of the {phi} meson from the hadronic rescattering dynamics leads to interesting and unambiguous features in the p{sub T} dependence of the nuclear suppression factor R{sub AA} and of the {phi}/pmore » ratio.« less

TeV to PeV neutrinos and gamma-rays with Mountain SHALON Mirror Cherenkov Telescope

Problems in observation of extensive air showers generated by neutrinos are connected with an extremely small cross-section of inelastic collisions of neutrinos with nuclei. However, two facts allow to search for showers generated by neutrinos: (1) a hadron cascade with a primary energy of more than 10 13 eV leaves a mountain ridge to the atmosphere from a depth ∼ 300 g / cm 2 without any essential loss of the total energy in the hadron cascade, and (2) air Cherenkov radiation from such hadron cascades will be observed with a 7.5 km distant telescope over an area of more than 7 × 10 5 m 2 . This partially compensates for the small cross-section of inelastic neutrino collisions. Observations have been carried out since 1992 at the high mountain Tien-Shan station using the SHALON Cherenkov mirror telescope with ∼11.2 m 2 mirror area and image matrix of 144 PMT with full angle >8°. The telescope characteristics allowed to start searching for local neutrino sources with energy 10 13 –10 16 eV on EAS generated in the mountain-range located at some 7.5 and more kilometers from the gamma-telescope (in Russian the abbreviation SHALON means - the Extensive Air Showers from Neutrino).

Measurements and simulation studies of piezoceramics for acoustic particle detection

Calibration sources are an indispensable tool for all detectors. In acoustic particle detection the goal of a calibration source is to mimic neutrino signatures as expected from hadronic cascades. A simple and promising method for the emulation of neutrino signals are piezo ceramics. We will present an detailed microscopic and macroscopic understanding of these piezo ceramics.

HEAT CAPACITY RELEVANT TO QGP PHASE TRANSITION AT $\sqrt{^SNN} = 200\ {\rm GeV}$

A parton and hadron cascade model, PACIAE, is applied to follow the particle transport in both the partonic and hadronic stages of the 0–5% most central Au + Au collisions at [Formula: see text]. We have determined the specific heat of π+ + π− in pure hadronic scenario (hadonic final state) and the specific heat of [Formula: see text] in pure partonic scenario (partonic initial state). The specific heat of π+ + π− in hadronic scenario is nearly a factor of 1.2 smaller than that of [Formula: see text] in partonic scenario. However, the specific heat of [Formula: see text] is very hard to survive the hadronization.

Elliptic flow from a hybrid CGC, full 3D hydro and hadronic cascade model

We investigate the robustness of the discovery of the perfect fluid through comparison of hydrodynamic calculations with the elliptic flow coefficient v2 at midrapidity in Au+Au collisions at . Employing the Glauber model for initial entropy density distributions, the centrality dependence of v2 is reasonably reproduced by using an ideal fluid description of the early QGP stage followed by a hadronic cascade in the late hadronic stage. On the other hand, initial conditions based on the colour glass condensate model are found to generate larger elliptic flow due to larger initial eccentricity ε. We further predict v2/ε at a fixed impact parameter as a function of collision energy up to the LHC energy.

Direct photon production in p + p and Au + Au collisions at in the PACIAE model

A parton and hadron cascade model, PACIAE, is used in investigating the PHENIX data of the direct photon and π0 invariant differential cross sections in p + p collisions and the direct photon and π0pT distributions in 0–10% of most central Au + Au collisions at top RHIC energy. It turns out that the above data are possible to be described by this microscopic transport model.

Specific heat in hadronic matter and in quark-gluon matter

A parton and hadron cascade model, PACIAE, is applied to follow the particle transport in partonic and the hadronic stages in 0--5% most central Au+Au collisions at energies from SPS to RHIC. We have determined the specific heat of hadron matter (${\ensuremath{\pi}}^{+}+{\ensuremath{\pi}}^{\ensuremath{-}}$) in the hadronic final state and the specific heat of quark-gluon matter ($u+d+g$) in the partonic initial state in Au+Au collisions as a function of the reaction energy (excitation function). It turns out that the quark-gluon matter (QGM) specific heat is hard to survive the hadronization and there is not a peak structure in the specific heat excitation functions in studied energy region.

Energy flow in a hadronic cascade: Application to hadron calorimetry

The hadronic cascade description developed in an earlier paper is extended to the response of an idealized fine-sampling hadron calorimeter. Calorimeter response is largely determined by the transfer of energy Eπ0 from the hadronic to the electromagnetic sector via π0 production. Fluctuations in this quantity produce the “constant term” in hadron calorimeter resolution. The increase of its fractional mean, fπ00=〈Eπ0〉/E, with increasing incident energy E causes the energy dependence of the π/e ratio in a noncompensating calorimeter. The mean hadronic energy fraction, fh0=1-fπ00, was shown to scale very nearly as a power law in E: fh0=(E/E0) m-1, where E0≈1GeV for pions, and m≈0.83. It follows that π/e=1-(1-h/e)(E/E0) m-1, where electromagnetic and hadronic energy deposits are detected with efficiencies e and h, respectively. If the mean fraction of fh0 which is deposited as nuclear gamma rays is fγ0, then the expression becomes π/e=1-(1-h′/e)(1-fγ0)(E/E0) m-1. Fluctuations in these quantities, along with sampling fluctuations, are incorporated to give an overall understanding of resolution, which is different from the usual treatments in interesting ways. The conceptual framework is also extended to the response to jets and the difference between π and p response.

Relativistic Hydrodynamics at RHIC and LHC

Recent development of a hydrodynamic model is discussed by putting an emphasis on realistic treatment of the early and late stages in relativistic heavy ion collisions. The model, which incorporates a hydrodynamic description of the quark-gluon plasma with a kinetic approach of hadron cascades, is applied to analysis of elliptic flow data at the Relativistic Heavy Ion Collider energy. It is predicted that the elliptic flow parameter based on the hybrid model increases with the collision energy up to the Large Hadron Collider energy.

The electronics for the AMS-02 calorimeter

AMS-02 is an astroparticle experiment that will operate on board of the ISS for a period of about three years. The main scientific goals of the experiment are the search for antimatter and dark matter and the study of gamma rays. In AMS-02 the Electromagnetic Calorimeter (ECAL) plays a key role for its high capability to measure e + , e - and gamma spectra and to discriminate electromagnetic showers from hadronic cascades [C. Adloff, et al., Performance of a 3D imaging electromagnetic calorimeter for the AMS02 space experiment, Proceedings of Calor 2004, Perugia, Italy. [1]]. All the electronics of the detector has been designed following stringent requirements on mechanical and thermal stability, power consumption, radiation hardness and double redundancy. The system has successfully gone through the space qualification tests and the full production will start soon.

One-dimensional hybrid approach to extensive air shower simulation

An efficient scheme for one-dimensional extensive air shower simulation and its implementation in the program conex are presented. Explicit Monte Carlo simulation of the high-energy part of hadronic and electro-magnetic cascades in the atmosphere is combined with a numeric solution of cascade equations for smaller energy sub-showers to obtain accurate shower predictions. The developed scheme allows us to calculate not only observables related to the number of particles (shower size) but also ionization energy deposit profiles which are needed for the interpretation of data of experiments employing the fluorescence light technique. We discuss in detail the basic algorithms developed and illustrate the power of the method. It is shown that Monte Carlo, numerical, and hybrid air shower calculations give consistent results which agree very well with those obtained within the corsika program.

MEASUREMENTS AND SIMULATION STUDIES OF PIEZOCERAMICS FOR ACOUSTIC PARTICLE DETECTION

Calibration sources are an indispensable tool for all detectors. In acoustic particle detection the goal of a calibration source is to mimic neutrino signatures as expected from hadronic cascades. A simple and promising method for the emulation of neutrino signals are piezo ceramics. We will present results of measurements and simulations on these piezo ceramics.

Net charge transfer fluctuation in quark–gluon matter and hadron matter

We investigated the net charge transfer fluctuation at mid-rapidity region in Au + Au collisions at root s(NN) = 200 GeV. A partonic and hadronic cascade model, PACIAE, is applied to follow the particle transport in both the partonic and hadronic phases. We have determined the factor, kappa, which characterizes the net charge transfer fluctuation. Considering the pure hadronic and pure partonic scenarios, we obtain a factor of 3-5 difference in kappa. However, by switching on the hadronization of partonic matter and introducing the secondary hadron-hadron interactions, the factor kappa will increase and finally approach the value of the pure hadronic scenario within an accuracy of 20%. (c) 2006 Elsevier B.V. All rights reserved.

Detection of metagalactic and galactic sources of very high-energy gamma-quanta and neutrinos with the mirror Cherenkov telescope SHALON

Gamma-astronomy and neutrino astronomy are unique experimental possibilities to search for sources of high-energy cosmic rays ( 10 12 – 10 14 eV ) . Experimental data on sources of γ -quanta with the energy > 1 TeV are characterized by the fact that observed metagalactic sources (active galactic nuclei), being different in power from galactic sources by the factor of 10 6 – 10 7 , do not differ in the energy spectrum, F ( > E γ ) ∝ E γ - 1.3 ± 0.15 . The power of the metagalactic sources and their unlimited number casts doubts on the assumption of a galactic origin of the observed cosmic-ray flux. It is possible to assume that the uniform cosmic-ray spectrum is formed by “braking” in multiple elastic or inelastic collisions with relict photons in intergalactic space. Thus, the observed distribution of protons and cosmic-ray nuclei with the spectral index 2.72 ± 0.02 ( = 2.718 … , the Napier's constant) may be a consequence of such a “braking” that warms up the relict photons. Problems in observation of extensive air showers generated by neutrinos are connected with an extremely small cross section of inelastic collisions of neutrinos with nuclei. However, two facts allow to search for showers generated by neutrinos: (1) a hadron cascade with the primary energy of more than 10 12 eV leaves a mountain ridge to the atmosphere from the depth ∼ 300 g / cm 2 without an essential loss of the total energy in the hadron cascade, and (2) air Cherenkov radiation from such hadron cascades will be observed with a 7.5 km distant telescope over an area of more than 7 × 10 5 m 2 . This partially compensates the small cross section of inelastic neutrino collisions.

Features of the absorption of 2-to 40-TeV cosmic-ray hadrons in lead

For the first time, experimental data on 2-to 40-TeV hadronic cascades recorded by a lead ionization calorimeter at the Tien-Shan mountain station of the Lebedev Institute of Physics (Moscow) are compared with the results of a present-day simulation based on the GEANT 3.21 code and performed with allowance for the detection procedure. The conclusion that along-flying component appears in high-energy hadronic cascades was drawn previously on the basis of these data. Some special features of the procedure for recording TeV-range hadrons in the calorimeter are considered. It is shown that the averaged hadronic cascades and various features of single cascades having energies below 10 TeV are simulated adequately by using the QGSJET + FLUKA generators of nuclear interactions, but that they are not described by using the GHEISHA generator at lower energies. Some features of the experimentally observed cascades could not be described for cascade energies above 10 TeV.