Event Centrality Research Articles

Study of the transverse mass spectra of strange particles in Pb–Pb collisions at 158 A GeV/c

The NA57 experiment has collected high statistics, high purity samples of K0S and Λ, Ξ and Ω hyperons produced in Pb–Pb collisions at 158 A GeV/c. In this paper we present a study of the transverse mass spectra of these particles for a sample of events corresponding to the most central 53% of the inelastic Pb–Pb cross-section. We analyse the transverse mass distributions in the framework of the blast-wave model for the full sample and, for the first time at the SPS, as a function of the event centrality.

The silicon Multiplicity Detector for the NA50 experiment

The operation and performance of the silicon strip Multiplicity Detector in the heavy-ion experiment NA50 at CERN are presented together with a selection of physics results. The main features of the detector are high speed (50 MHz sampling frequency), high granularity (more than 13,000 strips), and good radiation resistance. The detector provided a measurement of event centrality in Pb–Pb collisions, as well as target identification and the measurement of charged particle pseudorapidity distributions as a function of centrality.

Sports Tourism: From Binary Division to Quadripartite Construct

The convergence of sport with tourism is a phenomenon of such recent origin that there is, as yet, no universally accepted definition of ‘sports tourism’. Until recently the descriptors invariably followed a conceptual dualism with sport on the one side and tourism on the other, each field of study separated out from the other. Sport was further demarcated in a binary fashion between players and spectators. Recent work, however, has reconstituted the conventional binary opposites into ‘an other’ that is more than the sum of two parts, and this is ‘sports tourism’. The construct which best captures this trialectic (sport/tourism/sports tourism) is, in fact, a quadripartite exploration of the original binary division, an expansion of sport and tourism into hard and soft sports tourism, and hard and soft tourism sport. However, this construct omits several fundamental relationships between sport and tourism. These omissions include the centrality of events in formalized sports tourism, the role of sports tourism in creating a sense of place through co-branding and providing the impetus for wider development (as with the 2000 Sydney Olympic Games), the burgeoning partnership between sports organizations and tourism authorities, and the ‘sub-culture of the tournament’ that invariably accompanies sport tourism but which is not present in tourism sport. These issues are illustrated with examples drawn from Australia, New Zealand, the South Pacific and, to a lesser extent, Asia. An expanded construct of Gammon and Robinson's framework of sports tourism/tourism sport is then offered which incorporates these additional elements.

High momentum particle suppression in AuAu collisions at RHIC

Phenix has measured at mid-rapidity tranverse momentum spectra of charged particles in AuAu collisions at √SNN = 130 [1] and 200 GeV/c. At both energies, in central collisions Phenix observes a suppression of high momentum particles relative to a binary collision scaling of nucleon-nucleon interactions. The evolution with the event centrality has been investigated [2].

Do You See What I See? Effects of Group Consciousness on African American Women's Attributions to Prejudice

This study examined the effects of three types of group consciousness among African American women ( ethnic, feminist, and womanist) on prejudice attributions and appraised personal significance ( centrality) of a negative intergroup event. African American female college students ( N = 123) imagined themselves in an audiotaped scenario in which they overheard two European American male classmates make negative evaluations of them. The scenario provided no cause for the negative evaluations and no references to race or gender. Multiple regression analyses revealed that higher ethnic and womanist consciousness were related to increased prejudice attributions and greater centrality appraisals ( p < .05), while feminism had no effect. Results suggest that womanist consciousness may be more relevant than traditional feminist consciousness in predicting African American women's perceptions of prejudice.

The PHOBOS detector at RHIC

This manuscript contains a detailed description of the PHOBOS experiment as it is configured for the Year 2001 running period. It is capable of detecting charged particles over the full solid angle using a multiplicity detector and measuring identified charged particles near mid-rapidity in two spectrometer arms with opposite magnetic fields. Both of these components utilize silicon pad detectors for charged particle detection. The minimization of material between the collision vertex and the first layers of silicon detectors allows for the detection of charged particles with very low transverse momenta, which is a unique feature of the PHOBOS experiment. Additional detectors include a time-of-flight wall which extends the particle identification range for one spectrometer arm, as well as sets of scintillator paddle and Cherenkov detector arrays for event triggering and centrality selection.

The PHOBOS detector at RHIC

This manuscript contains a detailed description of the PHOBOS experiment as it is configured for the Year 2001 running period. It is capable of detecting charged particles over the full solid angle using a multiplicity detector and measuring identified charged particles near mid-rapidity in two spectrometer arms with opposite magnetic fields. Both of these components utilize silicon pad detectors for charged particle detection. The minimization of material between the collision vertex and the first layers of silicon detectors allows for the detection of charged particles with very low transverse momenta, which is a unique feature of the PHOBOS experiment. Additional detectors include a time-offlight wall which extends the particle identification range for one spectrometer arm, as well as sets of scintillator paddle and Cherenkov detector arrays for event triggering and centrality selection. r 2002 Elsevier Science B.V. All rights reserved. PACS: 25.75. q; 29.30.Aj; 29.40.Wk; 29.85.+c

Geometric relation between centrality and the impact parameter in relativistic heavy-ion collisions

We show, under general assumptions which are well satisfied in relativistic heavy-ion collisions, that the geometric relation of centrality c to the impact parameter b, namely c ~ pi b^2/sigma_inel, holds to a very high accuracy for all but most peripheral collisions. More precisely, if c(N) is the centrality of events with the multiplicity higer than N, then b is the value of the impact parameter for which the average multiplicity <n(b)> is equal to N. The corrections to this geometric formula are of the order (Delta n(b)/<n(b)>)^2, where Delta n(b) is the width of the multiplicity distribution at a given value of b, hence are very small. In other words, the centrality effectively measures the impact parameter.

Results from the First Physics Run of PHENIX at RHIC

First results from measurements of Au−Au collisions at \(\sqrt {s_{NN} } = 130\) GeV, performed with the PHENIX experiment during the initial physics run of Brookhaven National Laboratory’s Relativistic Heavy Ion Collider in summer 2000, are summarized. Global characterization of the collisions was obtained from charged-particle multiplicity and transverse energy densities. At mid-rapidity, dNch/dν and dET/dν rise steadily with the event centrality, while the ratio / remains constant. Transverse momentum spectra of charged particles up to 5 GeV/c yield a suppression of high-momentum particles in the most central events when compared to a simple scaling of binary nucleon-nucleon collisions. The scaling matches with peripheral collisions. Transverse momentum spectra of identified neutral pions from 1 to 4 GeV/c in peripheral collisions show consistency with point-like scaling with the average number of binary collisions. Yields in central collisions are significantly suppressed. Transverse momentum spectra of identified charged hadrons up to 3.5 GeV/c were measured in minimum bias events. The mass and centrality dependencies of inverse slope parameters and mean transverse momenta were determined. Inclusive spectra of electrons were measured for momenta from a few hundred MeV/c to 4 GeV/c. Inclusive photon spectra from a few hundred MeV/c to 3 GeV/c were obtained from conversion pair measurements.

Array of scintillator counters for PHOBOS at RHIC

An array of scintillator counters (“paddle counters”) for the measurement of number and energy of charged particles in heavy-ion gold–gold collisions for the PHOBOS experiment at RHIC is described. These simple, versatile, and highly efficient detectors provide a low bias and an easily understood level zero trigger. The paddle counters can also be used to select and measure event centrality. The information from the paddle counters used for triggering and event selection included the total signal height (proportional to the number of particles), the timing information of the hits, and the number of scintillators fired. The general characteristics of the paddle counters, their design parameters, and performance during the first run at RHIC are presented in this paper.

Japan's First Cyborg? Miss Nippon, Eugenics and Wartime Technologies of Beauty, Body and Blood

In June 1931, on the eve of the invasion of Manchuria, the Japanese mass media announced the winner of the first Miss Nippon contest. Applicants were limited to rank amateurs whose photographs, and not bodies, were judged by a panel of mostly elderly men who regarded the contest as `culture work'. A second contest was held in 1934. One of the main objectives of the Miss Nippon contests was to locate and record photographically, young women whose allegedly `pure blood' and ideal bodily proportions demonstrated the success of eugenics and social hygiene programs launched decades earlier. Japan's imperialist aggression in Asia and the Pacific forms the backdrop to this study on the centrality of popular cultural events and media in the state's attempt to improve the `Japanese race' through technologies of eugenics and social hygiene. The article explores the politics of blood, body and beauty, three interrelated subjects, framed by the Miss Nippon contests, that were common to the colonial project and the discourse of eugenics alike.

Determination of the event centrality in the WA97 and NA57experiments

The procedure employed by the WA97 and NA57 experiments to determinethe number of wounded nucleons in different Pb + Pb centrality classes isdiscussed. We will also compare different centrality scales and theirinfluence on the measurement of the centrality dependence of strangeparticle yields.

Measurements of neutrons in11.5AGeV/cAu+Pbheavy-ion collisions

We present measurements from Brookhaven Experiment 864 of neutron invariant multiplicity in 11.5 A GeV/c Au+Pb collisions. The measurements span a rapidity range from center-of-mass to beam rapidity (y(beam)=3.2) and are presented as a function of event centrality. The results are compared with E864 measurements of proton invariant multiplicity and an average n/p ratio at hadronic freeze-out of 1.19+-.08 is determined for the rapidity range y=1.6 to y=2.4. We discuss briefly the implications of this ratio within a simple equilibrium model of the collision system.

Radial flow in 40Ar+45Sc reactions at E=35-115 MeV/nucleon.

Collective radial flow of light fragments from $^{40}\mathrm{Ar}$${+}^{45}$Sc reactions at beam energies between 35 and 115 MeV/nucleon has been investigated using the Michigan State University 4\ensuremath{\pi} Array. The mean transverse kinetic energy 〈${\mathit{E}}_{\mathit{t}}$〉 of the different fragment types increases with event centrality and increases as a function of the incident beam energy. Comparison of our measured values of 〈${\mathit{E}}_{\mathit{t}}$〉 shows agreement with predictions of Boltzmann-Uehling-Uhlenbeck model and WIX multifragmentation model calculations. The radial flow extracted from 〈${\mathit{E}}_{\mathit{t}}$〉 accounts for approximately half of the emitted particle's energy for the heavier fragments (Z\ensuremath{\ge}4) at the highest beam energy studied. \textcopyright{} 1996 The American Physical Society.

Radial flow in Au+Au collisions at E=(0.25-1.15)A GeV.

A systematic study of energy spectra for light particles emitted at midrapidity from Au+Au collisions at E=0.25-1.15 A GeV reveals a significant non-thermal component consistent with a collective radial flow. This component is evaluated as a function of bombarding energy and event centrality. Comparisons to Quantum Molecular Dynamics (QMD) and Boltzmann-Uehling-Uhlenbeck (BUU) models are made for different equations of state.

Recent results from experiment 814 at Brookhaven

Recent results from the E814 collaboration are presented for reactions of 14.6 GeV/nucleon 28Si projectiles with targets of Al, Cu, and Pb. This includes transverse energy distributions over the full solid angle and the distribution of charged particle multiplicity in the forward hemisphere. Furthermore we present recent results on transverse momentum spectra and rapidity distributions for protons and discuss them in terms of stopping and/or transparency. A fraction of nucleons emerges at beam rapidity, even for the most central collisions. These ‘punch-through’ distributions are shown to yield information on the in-medium nucleon-nucleon cross section. Finally, we discuss antiproton production at 0° as a function of event centrality to shed some light on possible reabsorption.

Cognitive skills and young children's comprehension of television

The relation between young children's visual and verbal skills and their comprehension of an age-appropriate narrative television program was assessed. Forty-four children, aged 5 years, 3 months to 5 years, 9 months, were individually tested with 6 subscales from a comprehensive standardized intelligence test. Their comprehension of the central and incidental events, and of inferences from a 35-min narrative TV program, was also individually tested within 2 weeks of the intelligence testing. Verbal skills accounted for 42% of the variance in children's comprehension of the central events from the program. Verbal skills were also related to selectivity of memory for central versus incidental events. Visual short-term memory skills accounted for 20% of the variance in their comprehension of incidental events. It was suggested that children with high verbal skills have more capacity available for the processing of information relevant to the centrality of televised events.

Interestingness—A neglected variable in discourse processing

Symptomatic of a contemporary concern with affective factors in cognitive processing, a corpus of research is now emerging on the role of interestingness in discourse processing. This research has concentrated on narrative prose and has adopted a structural approach, arguing for the centrality of event and discourse structure in producing an affect like interest. The authors point out that this approach considers only one type of interest—knowledge-triggered —to the exclusion of another important type—value-triggered. A more comprehensive understanding of interest will only be achieved by researching other genres, such as exposition, and by considering the multiple sources of interest-producing conditions. We suggest the notion of “informational significance” as an inclusive term, and underline the need for a process-based understanding of interest.

Interestingness—A Neglected Variable in Discourse Processing

Symptomatic of a contemporary concern with affective factors in cognitive processing, a corpus of research is now emerging on the role of interestingness in discourse processing. This research has concentrated on narrative prose and has adopted a structural approach, arguing for the centrality of event and discourse structure in producing an affect like interest. The authors point out that this approach considers only one type of interest—knowledge‐triggered—to the exclusion of another important type—value‐triggered. A more comprehensive understanding of interest will only be achieved by researching other genres, such as exposition, and by considering the multiple sources of interest‐producing conditions. We suggest the notion of “informational significance” as an inclusive term, and underline the need for a process‐based understanding of interest.