Hadronic resonance production in Pb-Pb collisions at the ALICE experiment

Measurements of the yields of hadronic resonances (relative to non-resonances) in high-energy heavy-ion collisions allow the chemical freeze-out temperature and the time between chemical and thermal freeze-out of the collision system to be studied, while modifications to resonance masses and widths could be a signature of chiral symmetry restoration. The spectra (for pT < 5 GeV/c), total integrated yields, ratios to non-resonances (phi/pi and phi/K), mass, and width of the phi(1020) meson and the uncorrected yields, mass, and width of the K*(892)0 and anti-K*(892)0 mesons have been measured using the ALICE detector for Pb-Pb collisions at 2.76 TeV. These measurements will be compared to results from other collision systems and energies. Angular correlations between leading trigger hadrons and phi(1020) mesons have been measured in Pb-Pb and pp collisions; the mass and width of the phi(1020) meson as a function of the correlation angle will be presented.Comment: 10 pages, 9 figures; Proceedings for Nucleus-Nucleus 2012, 21 May-1 June 2012, San Antonio, Texas, USA; Submitted for publication in J. Phys.: Conference Serie

Resonances as Probes of Heavy-Ion Collisions at ALICE

Hadronic resonances serve as unique probes in the study of the hot and dense nuclear matter produced in heavy-ion collisions. Properties of the hadronic phase of the collision can be extracted from measurements of the suppression of resonance yields. A comparison of the transverse-momentum spectra of the phi(1020) meson and the proton (which have similar masses) can be used to study particle production mechanisms. Resonance measurements in pp collisions provide input for tuning QCD-inspired particle production models and serve as reference measurements for other collision systems. Measurements of resonances in p-Pb collisions allow nuclear effects in the absence of a hot and dense final state to be studied. The ALICE Collaboration has measured resonances in pp, p-Pb, and Pb-Pb collisions. These measurements will be discussed and compared to results from other experiments and to theoretical models.Comment: 4 Pages, 1 figure, Proceedings of Hot Quarks 2014, Las Negras, Spain, 21-28 September 2014, to be published in Journal of Physics: Conference Serie

Recent hadronic resonance measurements at ALICE

In heavy-ion physics, measurements of short-lived hadronic resonances allow the properties of the hadronic phase of the collision to be studied. In addition, resonances can be used along with stable hadrons to study parton energy loss in the quark-gluon plasma and the mechanisms that shape hadron pT spectra at intermediate transverse momenta. Resonance measurements in small systems serve as a reference for heavy-ion collisions and contribute to searches for collective effects. An overview of recent results on hadronic resonance production measured in ALICE is presented. These results include the pT spectra and yields of the rho(770)0, K*(892)0, and phi(1020) mesons in pp, p-Pb, and Pb-Pb collisions at different energies as well as the Sigma(1385)+/- and Xi(1530)0 baryons in pp and p-Pb collisions.Comment: 4 pages, 3 figures, Proceedings of the 16th International Conference on Strangeness in Quark Matter (SQM 2016), Berkeley, California, USA, 27 June-1 July 2016, to be published in Journal of Physics: Conference Serie

Disorder Effects in CA-Models for Traffic Flow

We investigate the effect of quenched disorder in the Nagel-Schreckenberg model of traffic flow. Spatial inhomogenities, i.e. lattice sites where the braking probability is enlarged, are considered as well as particle disorder, i.e. cars of a different maximum velocity. Both types of disorder lead to segregated states.Comment: 6 pages, 4 postscript figures, Proceedings of the conference "Traffic and Granular Flow '97", Duisburg, Germany, October 5-8, 199

Hadronic resonances in heavy-ion collisions at ALICE (Strangeness in Quark Matter 2013)

Properties of the hadronic phase of high-energy heavy-ion collisions can be studied by measuring the ratios of hadronic resonance yields to the yields of longer-lived particles. These ratios can be used to study the strength of re-scattering effects, the chemical freeze-out temperature, and the lifetime between chemical and kinetic freeze-out. The restoration of chiral symmetry during the early hadronic phase or near the phase transition may lead to shifts in the masses and increases in the widths of hadronic resonances. The ALICE collaboration has measured the spectra, masses, and widths of the K*(892)0 and phi(1020) resonances in Pb-Pb collisions at 2.76 TeV. These results, including RAA and the ratios of the integrated resonance yields to stable hadron yields, are presented and compared to results from other collision systems and to theoretical predictions.Comment: 4 pages, 3 figures, Proceedings of Strangeness in Quark Matter conference, 21-27 July 2013, Birmingham, U

The ALICE electromagnetic calorimeter high level triggers

The ALICE (A Large Ion Collider Experiment) detector yields a huge sample of data from different sub-detectors. On-line data processing is applied to select and reduce the volume of the stored data. ALICE applies a multi-level hardware trigger scheme where fast detectors are used to feed a three-level (L0, L1, and L2) deep chain. The High-Level Trigger (HLT) is a fourth filtering stage sitting logically between the L2 trigger and the data acquisition event building. The EMCal detector comprises a large area electromagnetic calorimeter that extends the momentum measurement of photons and neutral mesons up to $p_T=250$ GeV/c, which improves the ALICE capability to perform jet reconstruction with measurement of the neutral energy component of jets. An online reconstruction and trigger chain has been developed within the HLT framework to sharpen the EMCal hardware triggers, by combining the central barrel tracking information with the shower reconstruction (clusters) in the calorimeter. In the present report the status and the functionality of the software components developed for the EMCal HLT online reconstruction and trigger chain will be discussed, as well as preliminary results from their commissioning performed during the 2011 LHC running period.Comment: Proceeding for the CHEP 2012 Conferenc

Localized defects in a cellular automaton model for traffic flow with phase separation

We study the impact of a localized defect in a cellular automaton model for traffic flow which exhibits metastable states and phase separation. The defect is implemented by locally limiting the maximal possible flow through an increase of the deceleration probability. Depending on the magnitude of the defect three phases can be identified in the system. One of these phases shows the characteristics of stop-and-go traffic which can not be found in the model without lattice defect. Thus our results provide evidence that even in a model with strong phase separation stop-and-go traffic can occur if local defects exist. From a physical point of view the model describes the competition between two mechanisms of phase separation.Comment: 14 pages, 7 figure

A realistic two-lane traffic model for highway traffic

A two-lane extension of a recently proposed cellular automaton model for traffic flow is discussed. The analysis focuses on the reproduction of the lane usage inversion and the density dependence of the number of lane changes. It is shown that the single-lane dynamics can be extended to the two-lane case without changing the basic properties of the model which are known to be in good agreement with empirical single-vehicle data. Therefore it is possible to reproduce various empirically observed two-lane phenomena, like the synchronization of the lanes, without fine-tuning of the model parameters