27 research outputs found
Multiplicity fluctuations in nuclear collisions at 158 A GeV
System size dependence of multiplicity fluctuations of charged particles
produced in nuclear collisions at 158 A GeV was studied in the NA49 CERN
experiment. Results indicate a non-monotonic dependence of the scaled variance
of the multiplicity distribution with a maximum for semi-peripheral Pb+Pb
interactions with number of projectile participants of about 35. This effect is
not observed in a string-hadronic model of nuclear collision HIJING.Comment: Presented at "Focus on Multiplicity", 17-19 of June, Bari, Ital
Report from NA49
The most recent data of NA49 on hadron production in nuclear collisions at
CERN SPS energies are presented. Anomalies in the energy dependence of pion and
kaon production in central Pb+Pb collisions are observed. They suggest that the
onset of deconfinement is located at about 30 AGeV. Large multiplicity and
transverse momentum fluctuations are measured for collisions of intermediate
mass systems at 158 AGeV. The need for a new experimental programme at the CERN
SPS is underlined.Comment: invited talk presented at Quark Matter 2004, 10 page
Omega and Antiomega production in central Pb+Pb collisions at 40 and 158 AGeV
Results are presented on Omega production in central Pb+Pb collisions at 40
and 158 AGeV beam energy. Given are transverse-mass spectra, rapidity
distributions, and total yields for the sum Omega+Antiomega at 40 AGeV and for
Omega and Antiomega separately at 158 AGeV. The yields are strongly
under-predicted by the string-hadronic UrQMD model and are in better agreement
with predictions from a hadron gas models.Comment: 5 papes, 4 figures, 1 table, updated figure 4 and table 1. Final
version, including some editorial changes, as published in PR
Observation of an Exotic S = -2, Q = -2 Baryon Resonance in Proton-Proton Collisions at the CERN SPS
Results of resonance searches in the Xi- pi-, Xi- pi+, antiXi+ pi- and
antiXi+ pi+ invariant mass spectra in proton-proton collisions at sqrt{s}=17.2
GeV are presented. Evidence is shown for the existence of a narrow Xi- pi-
baryon resonance with mass of 1.862+/-0.002 GeV/c^2 and width below the
detector resolution of about 0.018 GeV/c^2. The significance is estimated to be
4.0 sigma. This state is a candidate for the hypothetical exotic Xi_(3/2)^--
baryon with S = -2, I = 3/2 and a quark content of (d s d s ubar). At the same
mass a peak is observed in the Xi- pi+ spectrum which is a candidate for the
Xi_(3/2)^0 member of this isospin quartet with a quark content of (d s u s
dbar). The corresponding antibaryon spectra also show enhancements at the same
invariant mass.Comment: 5 pages, 3 figure
System-size dependence of strangeness production in nucleus-nucleus collisions at sqrt{s_{NN}}=17.3 GeV
Emission of pi, K, phi and Lambda was measured in near-central C+C and Si+Si
collisions at 158 AGeV beam energy. Together with earlier data for p+p, S+S and
Pb+Pb, the system-size dependence of relative strangeness production in
nucleus-nucleus collisions is obtained. Its fast rise and the saturation
observed at about 60 participating nucleons can be understood as onset of the
formation of coherent partonic subsystems of increasing size.Comment: Phys.Rev.Lett in print; version2: changes made according to the
request of the referee
Rapidity and transverse momentum dependence of pion-pion Bose-Einstein correlations measured at 20, 30, 40, 80, and 158 AGeV beam energy
Preliminary results on pion-pion Bose-Einstein correlations in central Pb+Pb
collisions measured by the NA49 experiment are presented. Rapidity as well as
transverse momentum dependence of the HBT-radii are shown for collisions at 20,
30, 40, 80, and 158 AGeV beam energy. Including results from AGS and RHIC
experiments only a weak energy dependence of the radii is observed. Based on
hydrodynamical models parameters like lifetime and geometrical radius of the
source are derived from the dependence of the radii on transverse momentum.Comment: 5 pages, 4 figures, contribution to the Quark Matter conference,
Oakland, USA, Jan 11-17, 200
Event-by-Event Fluctuations of Particle Ratios in Central Pb+Pb Collisions at 20 to 158 AGeV
In the vicinity of the QCD phase transition, critical fluctuations have been
predicted to lead to non-statistical fluctuations of particle ratios, depending
on the nature of the phase transition. Recent results of the NA49 energy scan
program show a sharp maximum of the ratio of K+ to Pi+ yields in central Pb+Pb
collisions at beam energies of 20-30 AGeV. This observation has been
interpreted as an indication of a phase transition at low SPS energies. We
present first results on event-by-event fluctuations of the kaon to pion and
proton to pion ratios at beam energies close to this maximum.Comment: 4 pages, 4 figures, Quark Matter 2004 proceeding
Application of phasor measurement units for monitoring power system dynamic performance
This Working Group is a sequel to a previous working group on Wide Area Monitoring and Control for Transmission Capability Enhancement, which published the Technical Brochure 330 in 2007. Since then the synchrophasor technology has advanced rapidly and many utilities around the world have installed hundreds of PMUs in their networks. In this Technical Brochure, we look at the current state of the technology and the extent to which it has been used in the industry. As the technology has matured, it is also important to understand the communication protocols used in synchrophasor networks and their relevant cyber-security issues. These concerns are briefly discussed in the brochure. The applications of Phasor Measurement Units (PMU) measurements reported here are divided into three categories: (a) applications already installed in utility networks, (b) applications that are well-tested, but not yet installed, and (c) applications that are beneficial to the industry, but not fully developed yet. The most common and mature applications are wide area monitoring, state estimation, and model validation. Out of these three applications, wide area monitoring is well established in the industry. The protection and control applications are emerging as evident from the reported examples. The experience of using remote synchrophasor measurements as feedback control signals is not widely reported by the industry. In parallel to this Working Group, Study Committee B5 had a Working Group on “Wide area protection and control technologies.” The Technical Brochure 664 published by this Working Group in September 2016 reviews synchrophasor technology and discusses the industry experience with wide area protection and control. The North American synchrophasor Initiative (NASPI) is another technical group that has gathered and reported a wide range of PMU experiences of industry and researchers. In summary, the field-tested applications presented in this Technical Brochure are a testimony to the confidence of utilities in the synchrophasor technology. The progress in state estimation techniques indicates that synchrophasor measurements will become a standard part of energy management and security assessment systems in the near future
System size and centrality dependence of the balance function in A + A collisions at sqrt s NN = 17.2 GeV
Electric charge correlations were studied for p+p, C+C, Si+Si and centrality selected Pb+Pb collisions at sqrt s_NN = 17.2$ GeV with the NA49 large acceptance detector at the CERN-SPS. In particular, long range pseudo-rapidity correlations of oppositely charged particles were measured using the Balance Function method. The width of the Balance Function decreases with increasing system size and centrality of the reactions. This decrease could be related to an increasing delay of hadronization in central Pb+Pb collisions
System size and centrality dependence of the balance function in A+A collisions at sqrt[sNN]=17.2 GeV
Electric charge correlations were studied for p+p, C+C, Si+Si, and centrality selected Pb+Pb collisions at sqrt[sNN]=17.2 GeV with the NA49 large acceptance detector at the CERN SPS. In particular, long-range pseudorapidity correlations of oppositely charged particles were measured using the balance function method. The width of the balance function decreases with increasing system size and centrality of the reactions. This decrease could be related to an increasing delay of hadronization in central Pb+Pb collisions