Straggling of fast electrons Chaoui, Zine-El-Abidine; Bichsel, Hans
Surface and interface analysis,
April 2006, Letnik:
38, Številka:
4
Journal Article, Conference Proceeding
We present measurements of the charge balance function, from the charged particles, for diverse pseudorapidity and transverse momentum ranges in Au+Au collisions at sNN=200 GeV using the STAR ...detector at RHIC. We observe that the balance function is boost-invariant within the pseudorapidity coverage −1.3,1.3. The balance function properly scaled by the width of the observed pseudorapidity window does not depend on the position or size of the pseudorapidity window. This scaling property also holds for particles in different transverse momentum ranges. In addition, we find that the width of the balance function decreases monotonically with increasing transverse momentum for all centrality classes.
Yields, correlation shapes, and mean transverse momenta p{sub T} of charged particles associated with intermediate- to high-p{sub T} trigger particles (2.5 < p{sub T} < 10 GeV/c) in d+ Au and Au + Au ...collisions at {radical}s{sub NN} = 200 GeV are presented. For associated particles at higher p{sub T} {approx}> 2.5 GeV/c, narrow correlation peaks are seen in d + Au and Au + Au, indicating that the main production mechanism is jet fragmentation. At lower associated particle p{sub T} < 2 GeV/c, a large enhancement of the near-({Delta}{phi}{approx}0) and away-side ({Delta}{phi}{approx}{pi}) associated yields is found, together with a strong broadening of the away-side azimuthal distributions in Au + Au collisions compared to d + Au measurements, suggesting that other particle production mechanisms play a role. This is further supported by the observed significant softening of the away-side associated particle yield distribution at {Delta}{phi}{approx}{pi} in central Au + Au collisions.
Semiconductor detectors in general have a dead layer at their surfaces that is either a result of natural or induced passivation, or is formed during the process of making a contact. Charged ...particles passing through this region produce ionization that is incompletely collected and recorded, which leads to departures from the ideal in both energy deposition and resolution. The silicon \textit{p-i-n} diode used in the KATRIN neutrino-mass experiment has such a dead layer. We have constructed a detailed Monte Carlo model for the passage of electrons from vacuum into a silicon detector, and compared the measured energy spectra to the predicted ones for a range of energies from 12 to 20 keV. The comparison provides experimental evidence that a substantial fraction of the ionization produced in the "dead" layer evidently escapes by diffusion, with 46% being collected in the depletion zone and the balance being neutralized at the contact or by bulk recombination. The most elementary model of a thinner dead layer from which no charge is collected is strongly disfavored.
We present ΛΛ correlation measurements in heavy-ion collisions for Au+Au collisions at sqrts_{NN}=200 GeV using the STAR experiment at the Relativistic Heavy-Ion Collider. The Lednický-Lyuboshitz ...analytical model has been used to fit the data to obtain a source size, a scattering length and an effective range. Implications of the measurement of the ΛΛ correlation function and interaction parameters for dihyperon searches are discussed.
Stopping power of hydrogen atoms BICHSEL, H
Physical review. A, Atomic, molecular, and optical physics,
04/1991, Letnik:
43, Številka:
7
Journal Article
The stopping number of hydrogen atoms calculated with Bethe's theory in the first Born approximation is tabulated. A comparison is made with the asymptotic approximation and with a model based on the ...harmonic oscillator.
Values are given of the average energy required to produce an ion pair, Wn, and of the dose conversion factor, r, for tissue-equivalent chambers filled with either tissue-equivalent gas or air, ...irradiated by neutrons. The model for finite spherical cavities previously presented in part I was used for the calculations, which employed the W values and stopping powers of the charged particles produced in the materials described in part II. Neutron energies ranging from 0.4 to 14 MeV were considered: many of these energies were chosen because of their particularly large or small total cross-sections in order to explore the range of fluctuations of r and Wn. The results are therefore not very suitable for spectral averaging. Cavity sizes ranging from the infinitesimal Bragg-Gray to the infinite cavity were studied. It was found that the changes of r with cavity size and with neutron energy are smaller for the TE-TE chamber than for the TE-air chamber, but for Wn they are about equal; the TE-TE chamber should therefore be considered the ionisation chamber of choice but absolute doses cannot be determined with it to better than +/- 8%.
We report the first measurement of charmed-hadron (D(0)) production via the hadronic decay channel (D(0) → K(-) + π(+)) in Au+Au collisions at sqrts(NN) = 200 GeV with the STAR experiment. The charm ...production cross section per nucleon-nucleon collision at midrapidity scales with the number of binary collisions, N(bin), from p+p to central Au+Au collisions. The D(0) meson yields in central Au + Au collisions are strongly suppressed compared to those in p+p scaled by N(bin), for transverse momenta p(T) > 3 GeV/c, demonstrating significant energy loss of charm quarks in the hot and dense medium. An enhancement at intermediate p(T) is also observed. Model calculations including strong charm-medium interactions and coalescence hadronization describe our measurements.
We report a new STAR measurement of the longitudinal double-spin asymmetry A(LL) for inclusive jet production at midrapidity in polarized p + p collisions at a center-of-mass energy of sqrts=200 GeV. ...The data, which cover jet transverse momenta 5<p(T)<30 GeV/c, are substantially more precise than previous measurements. They provide significant new constraints on the gluon spin contribution to the nucleon spin through the comparison to predictions derived from one global fit to polarized deep-inelastic scattering measurements.
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