Effective Rheology of Bubbles Moving in a Capillary Tube

We calculate the average volumetric flux versus pressure drop of bubbles moving in a single capillary tube with varying diameter, finding a square-root relation from mapping the flow equations onto that of a driven overdamped pendulum. The calculation is based on a derivation of the equation of motion of a bubble train from considering the capillary forces and the entropy production associated with the viscous flow. We also calculate the configurational probability of the positions of the bubbles.Comment: 4 pages, 1 figur

Alignment of the ALICE Inner Tracking System with cosmic-ray tracks

37 pages, 15 figures, revised version, accepted by JINSTALICE (A Large Ion Collider Experiment) is the LHC (Large Hadron Collider) experiment devoted to investigating the strongly interacting matter created in nucleus-nucleus collisions at the LHC energies. The ALICE ITS, Inner Tracking System, consists of six cylindrical layers of silicon detectors with three different technologies; in the outward direction: two layers of pixel detectors, two layers each of drift, and strip detectors. The number of parameters to be determined in the spatial alignment of the 2198 sensor modules of the ITS is about 13,000. The target alignment precision is well below 10 micron in some cases (pixels). The sources of alignment information include survey measurements, and the reconstructed tracks from cosmic rays and from proton-proton collisions. The main track-based alignment method uses the Millepede global approach. An iterative local method was developed and used as well. We present the results obtained for the ITS alignment using about 10^5 charged tracks from cosmic rays that have been collected during summer 2008, with the ALICE solenoidal magnet switched off.Peer reviewe

Particle identification in ALICE : a Bayesian approach

Peer reviewe

Central-to-peripheral nuclear modification factors in Pb-Pb collisions at root(NN)-N-S=17.3 GeV

We present central-to-peripheral nuclear modification factors, R-CP, for the (PT) distributions of K-S(0), Lambda, Lambda, and negatively charged particles, measured at central rapidity in Pb-Pb collisions at top SPS energy. The data cover the 55% most central fraction of the inelastic cross section. The K-S(0) and Lambda R-CP((PT)) are similar in shape to those measured at root sNN = 200 GeV at RHIC, though they are larger in absolute value. We have compared our K-S(0) R-CP data to a theoretical calculation. The prediction overestimates the data at (PT) approximate to 3-4 GeV/c, unless sizeable parton energy loss is included in the calculation. (c) 2005 Elsevier B.V. All rights reserved

Hyperon production in lead-lead interactions at 40 and 160 A GeV/c

The NA57 experiment has measured strange baryon and antibaryon production in Pb-Pb collisions at 40 A GeV/c and 160 A GeV/c beam momenta. This presentation covers strangeness enhancement and transverse spectra from the 160 A GeV/c data, and energy dependence of the particle yields. Enhancement factors increase with increasing strangeness content of the particle, when production yields from Pb-Pb collisions are compared with those observed in p-Be and p-Pb interactions. The transverse mass spectra have been analysed both with exponential fits and using a transverse flow model

Energy dependence of hyperon production in nucleus-nucleus collisions at SPS

A measurement of strange baryon and antibaryon production in Pb-Pb collisions has been carried out by the NA57 experiment at the CERN SPS, with 40 and 158 A GeV/c beam momentum. Results on Lambda, Xi and Omega hyperon yields at mid-rapidity in the most central 53% of Pb-Pb collisions at 40 A GeV/c are presented and compared with those obtained at higher energy, in the same collision centrality range. The Lambda and Xi(-) yields per unit rapidity stay roughly constant while those of Omega(-), A, (&UXi;) over bar (+) and (&UOmega;) over bar (+) increase when going to the higher SPS energy. Hyperon yields at the SPS are compared with those from the STAR experiment in root(s)NN = 130 GeV Au-Au collisions at RHIC. (C) 2004 Elsevier B.V. All rights reserved

Multiplicity of charged particles in Pb-Pb collisions at SPS energies

The multiplicity of charged particles in the central rapidity region has been measured by the NA57 experiment in Pb-Pb collisions at the CERN SPS at two beam momenta: 158 A GeV/c and 40 A GeV/c. The value of dN(ch)/d eta at the maximum has been determined and its behaviour as a function of centrality has been studied in the centrality range covered by NA57 (about 50% of the inelastic cross section). The multiplicity increase is compatible with a logarithmic dependence on the centre of mass energy. The results are compared with those from other experiments and with the VENUS and RQMD models

ALICE: Physics Performance Report, Volume II

ALICE is a general-purpose heavy-ion experiment designed to study the physics of strongly interacting matter and the quark-gluon plasma in nucleus-nucleus collisions at the LHC. It currently involves more than 900 physicists and senior engineers, from both the nuclear and high-energy physics sectors, from over 90 institutions in about 30 countries. The ALICE detector is designed to cope with the highest particle multiplicities above those anticipated for Pb-Pb collisions (dN(ch)/dy up to 8000) and it will be operational at the start-up of the LHC. In addition to heavy systems, the ALICE Collaboration will study collisions of lower-mass ions, which are a means of varying the energy density, and protons (both pp and pA), which primarily provide reference data for the nucleus-nucleus collisions. In addition, the pp data will allow for a number of genuine pp physics studies. The detailed design of the different detector systems has been laid down in a number of Technical Design Reports issued between mid-1998 and the end of 2004. The experiment is currently under construction and will be ready for data taking with both proton and heavy-ion beams at the start-up of the LHC. Since the comprehensive information on detector and physics performance was last published in the ALICE Technical Proposal in 1996, the detector, as well as simulation, reconstruction and analysis software have undergone significant development. The Physics Performance Report (PPR) provides an updated and comprehensive summary of the performance of the various ALICE subsystems, including updates to the Technical Design Reports, as appropriate. The PPR is divided into two volumes. Volume I, published in 2004 (CERN/LHCC 2003-049, ALICE Collaboration 2004 J. Phys. G: Nucl. Part. Phys. 30 1517-1763), contains in four chapters a short theoretical overview and an extensive reference list concerning the physics topics of interest to ALICE, the experimental conditions at the LHC, a short summary and update of the subsystem designs, and a description of the offline framework and Monte Carlo event generators. The present volume, Volume II, contains the majority of the information relevant to the physics performance in proton-proton, proton-nucleus, and nucleus-nucleus collisions. Following an introductory overview, Chapter 5 describes the combined detector performance and the event reconstruction procedures, based on detailed simulations of the individual subsystems. Chapter 6 describes the analysis and physics reach for a representative sample of physics observables, from global event characteristics to hard processes