34 research outputs found
Calibration of Tuffak polycarbonate track detector for identification of relativistic nuclei
We discuss response of Tuffak polycarbonate to relativistic heavy nuclei using two methods, measurement of the minor axis diameter and of the length of the track cone, to determine charge resolution. At Z = 92 (0.95 GeV/u 238U) both methods give about 0.9e charge resolution for a single cone measurement. Multiple cone measurements along the ion's trajectory have yielded a charge resolution [sigma]z [les] 0.25e (16 cones) when stripping foils (Cu) are interleaved between plastic sheets to minimize sheet-to-sheet charge state correlations. As the charge of the incident ion decreases to Z [approximate] 52-57, the single-cone charge resolution improves ([sigma]z ~ 0.29e). The angular response of Tuffak is fairly constant for zenith angles of incidence from 0[deg] to 48[deg]. Range measurements of stopping relativistic 238U in Tuffak deviate by ~5% from that predicted by the Bethe-Bloch formula, as expected from recent relativistic calculations. We conclude that Tuffak is an excellent track detector for identification of nuclear charges of relativistic heavy nuclei with 50 Z <= 92.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24979/1/0000406.pd
Source size scaling of fragment production in projectile breakup
Fragment production has been studied as a function of the source mass and
excitation energy in peripheral collisions of Cl+Au at 43
MeV/nucleon and Ge+Ti at 35 MeV/nucleon. The results are
compared to the Au+Au data at 600 MeV/nucleon obtained by the ALADIN
collaboration. A mass scaling, by 35 to 190, strongly
correlated to excitation energy per nucleon, is presented, suggesting a thermal
fragment production mechanism. Comparisons to a standard sequential decay model
and the lattice-gas model are made. Fragment emission from a hot, rotating
source is unable to reproduce the experimental source size scaling.Comment: 13 pages LaTeX file, including 3 postscript figures (in .tar.gz
fornmat), accepted in Phys. Rev. C . Also available at
http://thomson.phy.ulaval.ca/ions_lourds/gil-en.htm
Lambda Hyperons in 2 A*GeV Ni + Cu Collisions
A sample of Lambda's produced in 2 A*GeV Ni + Cu collisions has been obtained
with the EOS Time Projection Chamber at the Bevalac. Low background in the
invariant mass distribution allows for the unambiguous demonstration of Lambda
directed flow. The transverse mass spectrum at mid-rapidity has the
characteristic shoulder-arm shape of particles undergoing radial transverse
expansion. A linear dependence of Lambda multiplicity on impact parameter is
observed, from which a total Lambda + Sigma^0 production cross section of $112
+/- 24 mb is deduced. Detailed comparisons with the ARC and RVUU models are
made.Comment: Revised version accepted for publication in Phys. Lett.
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A FAST MEGAPIXEL CCD IMAGE ACQUISITION AND ANALYSIS SYSTEM FOR HIGH ENERGY NUCLEAR PHYSICS
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A FAST MEGAPIXEL CCD IMAGE ACQUISITION AND ANALYSIS SYSTEM FOR HIGH ENERGY NUCLEAR PHYSICS
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Investigation into the feasibility of a soft muon experiment
Issues relevant in a soft ({lt} 5 GeV) muon pair experiment at the AGS or the RHIC central region are investigated. Observation of direct muon pairs is difficult because the muon pair to pion ratio is {omicron} (10{sup {minus}4}). Absorber penetration is the only means available to identify high energy muons among a large number of hadrons. Three important sources of background are sail-through hadrons that fail to interact in the absorber, the decays of pions and kaons to muons in the absorber, and leakage of hadronic shower products through the absorber. An absorber thick enough to limit the ratio of combinatorical background pairs to pions to {omicron} (10{sup {minus}4}) imposes a significant muon kinetic energy threshold due to muon range in the absorber. Absorbers with low atomic number Z are preferred to keep this threshold low, and to avoid loss of invariant mass resolution due to energy loss straggling and multiple coulomb scattering. Long-lived meson to muon decays can be directly suppressed only by picking an absorber with short interaction length, which implies a high density, high Z material. With sufficiently high statistics, a subtraction of the spectra of like-sign pairs from the spectrum of opposite-sign pairs should recover the direct muon pair spectrum. 9 refs., 9 figs., 2 tabs
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Sub 65 ps Timing Resolution Using Large Area Silicon Avalanche Diodes
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