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A. Andronic

Publications and source records attributed to A. Andronic.

At least 55 records · Page 3Linked to original sources
arXiv2011

Systematics of azimuthal asymmetries in heavy ion collisions in the 1 A GeV regime

Using the large acceptance apparatus FOPI, we study central and semi-central collisions in the reactions (energies in A GeV are given in parentheses): 40Ca+40Ca (0.4, 0.6, 0.8, 1.0, 1.5, 1.93), 58Ni+58Ni (0.15, 0.25, 0.4), 96Ru+96Ru (0.4, 1.0, 1.5), 96Zr+96Zr (0.4, 1.0, 1.5), 129Xe+CsI (0.15, 0.25, 0.4), 197Au+197Au (0.09, 0.12, 0.15, 0.25, 0.4, 0.6, 0.8, 1.0, 1.2, 1.5). The observables include directed and elliptic flow. The data are compared to earlier data where possible and to transport model simulations. A stiff nuclear equation of state is found to be incompatible with the data. Evidence for extra-repulsion of neutrons in compressed asymmetric matter is found.

nucl-ex↗
arXiv2011

Transition Radiation Detectors

We review the basic features of transition radiation and how they are used for the design of modern Transition Radiation Detectors (TRD). The discussion will include the various realizations of radiators as well as a discussion of the detection media and aspects of detector construction. With regard to particle identification we assess the different methods for efficient discrimination of different particles and outline the methods for the quantification of this property. Since a number of comprehensive reviews already exist, we predominantly focus on the detectors currently operated at the LHC. To a lesser extent we also cover some other TRDs, which are planned or are currently being operated in balloon or space-borne astro-particle physics experiments.

physics.ins-det↗
arXiv2011

The thermal model on the verge of the ultimate test: particle production in Pb-Pb collisions at the LHC

We investigate the production of hadrons in nuclear collisions within the framework of the thermal (or statistical hadronization) model. We discuss both the ligh-quark hadrons as well as charmonium and provide predictions for the LHC energy. Even as its exact magnitude is dependent on the charm production cross section, not yet measured in Pb-Pb collisions, we can confidently predict that at the LHC the nuclear modification factor of charmonium as a function of centrality is larger than that observed at RHIC and compare the experimental results to these predictions.

nucl-th↗
arXiv2011

Heavy quarkonium: progress, puzzles, and opportunities

A golden age for heavy quarkonium physics dawned a decade ago, initiated by the confluence of exciting advances in quantum chromodynamics (QCD) and an explosion of related experimental activity. The early years of this period were chronicled in the Quarkonium Working Group (QWG) CERN Yellow Report (YR) in 2004, which presented a comprehensive review of the status of the field at that time and provided specific recommendations for further progress. However, the broad spectrum of subsequent breakthroughs, surprises, and continuing puzzles could only be partially anticipated. Since the release of the YR, the BESII program concluded only to give birth to BESIII; the $B$-factories and CLEO-c flourished; quarkonium production and polarization measurements at HERA and the Tevatron matured; and heavy-ion collisions at RHIC have opened a window on the deconfinement regime. All these experiments leave legacies of quality, precision, and unsolved mysteries for quarkonium physics, and therefore beg for continuing investigations. The plethora of newly-found quarkonium-like states unleashed a flood of theoretical investigations into new forms of matter such as quark-gluon hybrids, mesonic molecules, and tetraquarks. Measurements of the spectroscopy, decays, production, and in-medium behavior of c\bar{c}, b\bar{b}, and b\bar{c} bound states have been shown to validate some theoretical approaches to QCD and highlight lack of quantitative success for others. The intriguing details of quarkonium suppression in heavy-ion collisions that have emerged from RHIC have elevated the importance of separating hot- and cold-nuclear-matter effects in quark-gluon plasma studies. This review systematically addresses all these matters and concludes by prioritizing directions for ongoing and future efforts.

hep-ph↗
arXiv2010

Systematics of central heavy ion collisions in the 1A GeV regime

Using the large acceptance apparatus FOPI, we study central collisions in the reactions (energies in A GeV are given in parentheses): 40Ca+40Ca (0.4, 0.6, 0.8, 1.0, 1.5, 1.93), 58Ni+58Ni (0.15, 0.25, 0.4), 96Ru+96Ru (0.4, 1.0, 1.5), 96Zr+96Zr (0.4, 1.0, 1.5), 129Xe+CsI (0.15, 0.25, 0.4), 197Au+197Au (0.09, 0.12, 0.15, 0.25, 0.4, 0.6, 0.8, 1.0, 1.2, 1.5). The observables include cluster multiplicities, longitudinal and transverse rapidity distributions and stopping, and radial flow. The data are compared to earlier data where possible and to transport model simulations.

nucl-ex↗
arXiv2010

Heavy quark(onium) at LHC: the statistical hadronization case

We discuss the production of charmonium in nuclear collisions within the framework of the statistical hadronization model. We demonstrate that the model reproduces very well the availble data at RHIC. We provide predictions for the LHC energy where, dependently on the charm production cross section, a dramatically different behaviour of charmonium production as a function of centrality might be expected. We discuss also the case in elementary collisions, where clearly the statistical model does not reproduce the measurements.

nucl-th↗
arXiv2010

Hadron Production in Ultra-relativistic Nuclear Collisions: Quarkyonic Matter and a Triple Point in the Phase Diagram of QCD

We argue that features of hadron production in relativistic nuclear collisions, mainly at CERN-SPS energies, may be explained by the existence of three forms of matter: Hadronic Matter, Quarkyonic Matter, and a Quark-Gluon Plasma. We suggest that these meet at a triple point in the QCD phase diagram. Some of the features explained, both qualitatively and semi-quantitatively, include the curve for the decoupling of chemical equilibrium, along with the non-monotonic behavior of strange particle multiplicity ratios at center of mass energies near 10 GeV. If the transition(s) between the three phases are merely crossover(s), the triple point is only approximate.

hep-ph↗
arXiv2009

The horn, the hadron mass spectrum and the QCD phase diagram - the statistical model of hadron production in central nucleus-nucleus collisions

We present the status of the description of hadron production in central nucleus-nucleus collisions within the statistical model . The recent inclusion of very high-mass resonances and the sigma meson leads to an improved description of the data, in particular the energy dependence of the K+/pi+ ratio at SPS energies (``the horn''). The connection to the QCD phase diagram is discussed.

nucl-th↗
arXiv2009

The canonical partition function for relativistic hadron gases

Particle production in high-energy collisions is often addressed within the framework of the thermal (statistical) model. We present a method to calculate the canonical partition function for the hadron resonance gas with exact conservation of the baryon number, strangeness, electric charge, charmness and bottomness. We derive an analytical expression for the partition function which is represented as series of Bessel functions. Our results can be used directly to analyze particle production yields in elementary and in heavy ion collisions. We also quantify the importance of quantum statistics in the calculations of the light particle multiplicities in the canonical thermal model of the hadron resonance gas.

hep-ph↗
arXiv2009

A comprehensive study of rate capability in Multi-Wire Proportional Chambers

Systematic measurements on the rate capability of thin MWPCs operated in Xenon, Argon and Neon mixtures using CO2 as UV-quencher are presented. A good agreement between data and existing models has been found, allowing us to present the rate capability of MWPCs in a comprehensive way and ultimately connect it with the mobilities of the drifting ions.

physics.ins-det↗
arXiv2009

Statistical hadronization of heavy flavor quarks in elementary collisions: successes and failures

We analyze recently compiled data on the production of open heavy flavor hadrons and quarkonia in e+e- as well as pp and p-nucleus collisions in terms of the statistical hadronization model. Within this approach the production of open heavy flavor hadrons is well described with parameters deduced from a thermal analysis of light flavor hadron production. In contrast, quarkonium production in such collisions cannot be described in this framework. We point out the relevance of this finding for our understanding of quarkonium production in ultra-relativistic nucleus-nucleus collisions.

hep-ph↗
arXiv2009

Thermal hadron production in relativistic nuclear collisions

We present the status of the description of hadron production in central nucleus-nucleus collisions within the statistical model . Extending previous studies by inclusion of very high-mass resonances (m>2 GeV), and the up-to-now neglected scalar $σ$ meson leads to an improved description of the data. In particular, the hitherto poorly reproduced energy dependence of the K+/pi+ ratio at SPS energies ("the horn") is now well described through the connection to the hadronic mass spectrum and, implicitly, Hagedorn's limiting temperature.

nucl-th↗
arXiv2009

Thermal hadron production in relativistic nuclear collisions: the hadron mass spectrum, the horn, and the QCD phase transition

We present, using the statistical model, a new analysis of hadron production in central collisions of heavy nuclei. This study is motivated by the availability of final measurements both for the SPS (beam energies 20-160 AGeV) and for the RHIC energies ($\sqrt{s_{NN}}$=130 and 200 GeV) and by updates in the hadron mass spectrum, which is a crucial input for statistical models. Extending previous studies by inclusion of very high-mass resonances (m> 2 GeV), and the up-to-now neglected scalar $σ$ meson leads to an improved description of the data. In particular, the hitherto poorly reproduced energy dependence of the $K^+/π^+$ ratio at SPS energies ("the horn") is now well described through the connection to the hadronic mass spectrum and, implicitly, Hagedorn's limiting temperature. We thereby demonstrate the intimate connection between the horn and the QCD phase transition.

nucl-th↗
arXiv2009

Thermal description of hadron production in e+e- collisions revisited

We present a comprehensive analysis of hadron production in e+e- collisions at different center-of-mass energies in the framework of the statistical model of the hadron resonance gas. The model is formulated in the canonical ensemble with exact conservation of all relevant quantum numbers. The parameters of the underlying model were determined using a fit to the average multiplicities of the latest measurements at $\sqrt{s}$ = 10, 29-35, 91 and 130-200 GeV. The results demonstrate that, within the accuracy of the experiments, none of the data sets is satisfactorily described with this approach, calling into question the notion that particle production in e+e- collisions is thermal in origin.

hep-ph↗
arXiv2009

Measurement of the in-medium K0 inclusive cross section in pi- -induced reactions at 1.15 GeV/c

The K0 meson production by pi- mesons of 1.15 GeV/c momentum on C, Al, Cu, Sn and Pb nuclear targets was measured with the FOPI spectrometer at the SIS accelerator of GSI. Inclusive production cross-sections and the momentum distributions of K0 mesons are compared to scaled elementary production cross-sections and to predictions of theoretical models describing the in-medium production of kaons. The data represent a new reference for those models, which are widely used for interpretation of the strangeness-production in heavy-ion collisions. The presented results demonstrate the sensitivity of the kaon production to the reaction amplitudes inside nuclei and point to the existence of a repulsive KN-potential of 20+-5 MeV at normal nuclear matter density.

nucl-ex↗
arXiv2009

Canonical Statistical Model and hadron production in $e^+e^-$ annihilations

We discuss the production of hadrons in $e^+e^-$ collisions at $\sqrt s=91$ GeV. We address the question wether the particle yields measured in the final states are consistent with the statistical model predictions. In the model formulation we account for exact conservation of all relevant quantum numbers using the canonical description of the partition function. Within our model the validity of the thermodynamical approach to quantify particle production in $e^+e^-$ annihilations is not obvious.

hep-ph↗
arXiv2008

Z0 Boson Measurement with the ALICE Central Barrel in pp collisions at 14 TeV

The possibility to detect the Z0 in the ALICE central barrel is studied via the electronic decay channel Z0->e+e-. The signal and the background are simulated with the leading order event generator PYTHIA 6. The total cross-sections are taken from NLO calculations. Based on test beam data, the electron identification performance of the Transition Radiation Detector is extrapolated to high momenta. The expected yields for minimum-bias pp collisions at 14 TeV are presented. An isolation cut on the single electron, together with a minimum transverse momentum cut, allows to obtain a clear signal. The expected background is of the order of 1 % with the main contribution coming from misidentified pions from jets.

hep-ex↗