197 research outputs found
Pseudorapidity distributions of charged particles from Au+Au collisions at the maximum RHIC energy, Sqrt(s_NN) = 200 GeV
We present charged particle densities as a function of pseudorapidity and
collision centrality for the 197Au+197Au reaction at Sqrt{s_NN}=200 GeV. For
the 5% most central events we obtain dN_ch/deta(eta=0) = 625 +/- 55 and
N_ch(-4.7<= eta <= 4.7) = 4630+-370, i.e. 14% and 21% increases, respectively,
relative to Sqrt{s_NN}=130 GeV collisions. Charged-particle production per pair
of participant nucleons is found to increase from peripheral to central
collisions around mid-rapidity. These results constrain current models of
particle production at the highest RHIC energy.Comment: 4 pages, 5 figures; fixed fig. 5 caption; revised text and figures to
show corrected calculation of and ; final version accepted for
publicatio
Charged particle densities from Au+Au collisions at sqrt{s_{NN}}=130 GeV
We present charged particle densities as a function of pseudorapidity and
collision centrality for the 197Au+197Au reaction at sqrt{s_{NN}}=130 GeV. An
integral charged particle multiplicity of 3860+/-300 is found for the 5% most
central events within the pseudorapidity range -4.7 <= eta <= 4.7. At
mid-rapidity an enhancement in the particle yields per participant nucleon pair
is observed for central events. Near to the beam rapidity, a scaling of the
particle yields consistent with the ``limiting fragmentation'' picture is
observed. Our results are compared to other recent experimental and theoretical
discussions of charged particle densities in ultra-relativistic heavy-ion
collisions.Comment: 14 pages, 4 figures; to be published in Phys. Lett.
Quadrupole-deformed and octupole collective bands in Ra
Spins and parities for collective states in Ra have been determined from conversion electron measurements with a mini-orange -spectrometer. The fast-timing method has been used to measure lifetimes of T=550(20) ps and 181(3) ps for the and members of the K=0 band, and T 7 ps and 6 ps for the and members of the K = band, respectively The quadrupole moments, deduced from the B (E2; 2) and B (E2; 4) rates are in good agreement with the previously measured value and the systematics of the region. However, the B(E1) rates of 4 × 10 efm, which represent the first B(E1) measurements for this nucleus, are at least 25 times larger than the value previously suggested for Ra. The new results are consistent with the B(E1) rates recently measured for the neighbouring Ra and reveal octupole correlations in Ra
Production of strange and multistrange hadrons in nucleus-nucleus collisions at SPS
We report the main results from experiment WA97 on the production of strange and multistrange hadrons at midrapidity in Pb+Pb, p+Pb and p+Be collisions at 158~A~GeV/. A comparison with some of the available models is presented
Transverse mass spectra of strange and multi-strange particles in Pb-Pb collisions at 158 A GeV/c
The WA97 experiment has measured the transverse mass (\mT) spectra fornegative hadrons (\hneg) and strange particles produced at mid--rapidity in Pb--Pb collisions. The increased statistics of analysed data samples allowed us to perform a study of the spectra of \PKzS, \PgL, , and\hneg~as a function of the collision centrality. The data, whichcorrespond to the most central 40\% of the total inelastic cross section,have been divided into four centrality classes according to the estimated numberof nucleons taking part in the collision. The \mT~ spectra, analysed separatelyfor each centrality bin, exhibit only weak ( 15\%) centrality dependence. The deviation of the inverse slope from the linear dependence on the particle massis confirmed even for the most central Pb--Pb collisions
Rapidity dependence of antiproton to proton ratios in Au+Au collisions at sqrt{s_{NN}}=130 GeV
Measurements, with the BRAHMS detector, of the antiproton to proton ratio at
central and forward rapidities are presented for Au+Au reactions at
sqrt{s_{NN}}=130 GeV, and for three different collision centralities. For
collisions in the 0-40% centrality range we find $N(\bar{{\rm p}})/N({\rm p}) =
0.64 +- 0.04 (stat.) +- 0.06 (syst.) at y ~0, 0.66 +- 0.03 +- 0.06 at y ~ 0.7,
and 0.41 +- 0.04 +- 0.06 at y ~ 2. The ratios are found to be nearly
independent of collision centrality and transverse momentum. The measurements
demonstrate that the antiproton and proton rapidity densities vary differently
with rapidity, and indicate that a net-baryon free midrapidity plateau (Bjorken
limit) is not reached at this RHIC energy.Comment: 8 pages, 3 figure
Strangeness enhancement at mid-rapidity in Pb-Pb collisions at 158 GeV/c
, , , and negative particle yields and transverse mass spectra have been measured at central rapidity in Pb-Pb and p-Pb collisions at 158 GeV/. The yields in Pb-Pb interactions % are presented as a function of the collision centrality and compared with those obtained from p-Pb collisions. Strangeness enhancement in Pb-Pb relative to p-Pb collisions increases with the strangeness content of the particle. Going from p-Pb to Pb-Pb, the strange particle yields increase faster than linearly with the number of participants up to , thereafter the increase becomes %linear with . Yields are studied as a function of the number of nucleons participating in the collision , which is estimated with the Glauber model. From p-Pb to Pb-Pb collisions the particle yields per participant increase substantially. The enhancement is more pronounced for multistrange particles, and exceeds an order of magnitude for the . For a number of participants, , greater than , however, all yields per participant appear to be constant
Hyperon production in proton-sulphur collisions at 200 GeV/c
The WA94 experiment uses the production of strange particles and antiparticles to investigate the properties of hot hadronic matter created in heavy--ion interactions. \PgL, \PagL, \PgXm\ and \PagXp\ particle yields and transverse mass spectra are presented for pS interactions. These results are compared with those from SS interactions. Our results are also compared with those from pW and SW interactions of the WA85 experiment
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