21 research outputs found
First analysis of anisotropic flow with Lee--Yang zeroes
We report on the first analysis of directed and elliptic flow with the new
method of Lee--Yang zeroes. Experimental data are presented for Ru+Ru reactions
at 1.69 AGeV measured with the FOPI detector at SIS/GSI. The results obtained
with several methods, based on the event-plane reconstruction, on Lee--Yang
zeroes, and on multi-particle cumulants (up to 5th order) applied for the first
time at SIS energies, are compared. They show conclusive evidence that
azimuthal correlations between nucleons and composite particles at this energy
are largely dominated by anisotropic flow.Comment: 5 pages, 3 figures, submitted to Phys. Rev. C Rapid Co
1ST OBSERVATION OF THE COULOMB-EXCITED DOUBLE GIANT-DIPOLE RESONANCE IN PB-208 VIA DOUBLE-GAMMA DECAY
The photon decay of the relativistic Coulomb excitation of the single and double giant dipole resonance (GDR) in the target has been observed in the system 1A GeV Bi-209 on Pb-208. For peripheral events which are dominated by relativistic Coulomb excitation, a large Lorentzian structure in the photon energy spectrum is peaked at 13.3+/-0.1 MeV with a width of 4.1+/-0.1 MeV, corresponding to the single GDR in the Pb-208 target. The sum energy of coincident gamma-gamma pairs shows a broad feature at 25.6+/-0.9 MeV with a Lorentzian width of 5.8+/-1.1 MeV, which we assign to the double GDR observed via the two-gamma decay channel
Heterogeneity in Economics
Heterogeneity, Uniqueness and stability of equilibrium, Adaptation, Learning, Varying expectations, B41, C62, D50, D84, G10,
Multi-strip MRPCs for FOPI
During the last years FOPI has developed a new ToF system as an upgrade of the existing detector based on Multi-strip Multi-gap Resistive Plate Chambers (MMRPCs). The intention is to increase the charged Kaon identification up to a laboratory momentum of 1 GeV/c and to enhance the azimuthal detector granularity. The new ToF barrel has an active area of 5 m(2) with 2400 individual strips (900 x 1.6 mm(2)) [A. Schuttauf, et al., Nucl. Phys. B 158 (2006) 52] which are read out on both sides by a custom designed electronics [M. Ciobanu, et al., IEEE Trans. Nucl. Sci. NS-54 (4) (2007) 1201; K. Koch, et al., IEEE Trans. Nucl. Sci. NS-52(3) (2005) 745]. To reach the envisaged goal a time resolution of 100 ps is needed, at a flight path of 1-1.3 m. Due to the rare production of the K- at SIS energies the efficiency of the MMRPCs has to be above 95%. We report on measurements with the detectors and electronics from the mass production line. For this purpose we used a proton beam at 2.0 and 1.25 GeV, at rates between 0.1 and 5 kHz/cm(2) to determine the timing, efficiency and rate capability of the MMRPC
Shape of collective flow in highly central Au(150 A MeV)+Au collisions
Using the FOPI facility at GSI, charged particles (1 â€Zâ€6) produced in the Au(150 A MeV)+Au reaction have been measured at laboratory angles 1.20 < Îlab < 300. Highly central collisions have been selected with two criteria, both dealing with the longitudinal and transverse degrees of freedom of the reaction. The relevance of this selection method is supported by QMD calculations which indicate that such criteria are able to select mean impact parameters less than 2 fm. Bias effects introduced by the criteria have been evaluated. The centre-of-mass polar angle distributions of low energy clusters emitted in these central collisions, have been extracted: the intensity ratio deduced for a transverse to longitudinal emission is found to be R= 1.4 â0.4 +0.2 . Model comparisons using QMD are presented. The value of R appears to depend sensitively on the nucleon-nucleon cross section, Ïnn. Within this model, a value of Ï=25+ - 5 mb is derived