Two-particle interferometry of positive kaons is studied in Pb+Pb collisions at mean transverse momenta <p(T)> approximately 0.25 and 0.91 GeV/c. A three-dimensional analysis was applied to the lower ...p(T) data, while a two-dimensional analysis was used for the higher p(T) data. We find that the source-size parameters are consistent with the m(T) scaling curve observed in pion-correlation measurements in the same collisions, and that the duration time of kaon emission is consistent with zero within the experimental sensitivity.
Proton and deuteron production has been observed in S+S and S+Pb collisions at 200 A\(\cdot\)GeV and in Pb+Pb reactions at 158 A\(\cdot\)GeV at the CERN SPS accelerator. For Pb+Pb triton production ...was also measured. The p and d spectra as well as the p and t spectra were observed in similar rapidity ranges and over similar ranges of transverse momenta per nucleon, making it possible to interpret the cross sections of the composite particles in terms of coalescence mechanisms. Volumes of homogeneity were extracted and compared to pion-pair HBT interferometry results. Special attention is given to the dependence on transverse mass, centrality and rapidity.
The NA44 Collaboration has measured yields and differential distributions of
K
+,
K
−,
π
+,
π
− in transverse kinetic energy and rapidity, around the center-of-mass rapidity in 158 A GeV/
c Pb+Pb ...collisions at the CERN SPS. A considerable enhancement of
K
+ production per
π is observed, as compared to
p+
p collisions at this energy. To illustrate the importance of secondary hadron rescattering as an enhancement mechanism, we compare strangeness production at the SPS and AGS with predictions of the transport model RQMD.
Azimuthal anisotropy (v(2)) and two-particle angular correlations of high p(T) charged hadrons have been measured in Au+Au collisions at sqrts(NN)=130 GeV for transverse momenta up to 6 GeV/c, where ...hard processes are expected to contribute significantly. The two-particle angular correlations exhibit elliptic flow and a structure suggestive of fragmentation of high p(T) partons. The monotonic rise of v(2)(p(T)) for p(T)<2 GeV/c is consistent with collective hydrodynamical flow calculations. At p(T)>3 GeV/c, a saturation of v(2) is observed which persists up to p(T)=6 GeV/c.
Two-particle correlations of negative pions as a function of charged particle multiplicity are studied in Pb+Pb collisions at \(\sqrt{s}=17.3\)GeV per nucleon using the NA44 experiment at the CERN ...Super Proton Synchrotron(SPS). We find that the source size parameters increase with the charged particle multiplicity. However the slope of the source size parameters plotted as a function of charged multiplicity is slightly larger at high multiplicity than at low multiplicity. The value of \(\lambda\) is independent of charged multiplicity. For Pb+Pb collisions, \(R_L\) is larger than \(R_{TS}\) and \(R_{TO}\) for all multiplicity intervals, whereas these three radius parameters were approximately equal in S+Nucleus collisions. The ratios (\(R_L/R_{TS}\)) and (\(R_L/R_{TO}\)) for Pb+Pb data show almost no dependence on charged multiplicity. The duration of pion emission \(\Delta \tau\) is constant at 3.8\(\pm\)1.1 fm/c as a function of the charged multiplicity in Pb+Pb collisions. Effective volume (V) is also calculated as V=\(\pi\times R_{TS}^2\times R_L\), assuming a cylindrically shaped source. We found, within the limited statistics, the effective volume rapidly increases at high multiplicity.
Hardware controls for the STAR experiment at RHIC Reichhold, D; Bieser, F; Bordua, M ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2003, Letnik:
499, Številka:
2
Journal Article
Recenzirano
The STAR detector sits in a high radiation area when operating normally; therefore it was necessary to develop a robust system to remotely control all hardware. The STAR hardware controls system ...monitors and controls approximately 14,000 parameters in the STAR detector. Voltages, currents, temperatures, and other parameters are monitored. Effort has been minimized by the adoption of experiment-wide standards and the use of pre-packaged software tools. The system is based on the Experimental Physics and Industrial Control System (EPICS)
1. VME processors communicate with subsystem-based sensors over a variety of field busses, with High-level Data Link Control (HDLC) being the most prevalent. Other features of the system include interfaces to accelerator and magnet control systems, a web-based archiver, and C++-based communication between STAR online, run control and hardware controls and their associated databases. The system has been designed for easy expansion as new detector elements are installed in STAR.
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