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  • 2000-2004  (3)
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  • 2000-2004  (3)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 18 (2001), S. 645-649 
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We consider the role of hadronic rescattering of daughter kaons on the observed mass spectra from $\phi$ meson decays in ultra-relativistic heavy ion collisions. A hadronic cascade code (RQMD v2.4) shows that $\sim$ 26% of all $\phi$ 's decaying to $K^+K^-$ in central Pb+Pb collisions at SPS energies ( $E_{beam} = 158 AGeV$ ) have a rescattered or absorbed daughter. This significantly affects the reconstructed invariant mass of the pair and shifts $\phi$ mesons out of the mass peak. Kaon rescattering depletes the low velocity region, hardening and broadening the observed $\phi m_t$ and rapidity distributions respectively, relative to the dilepton channel. This effect produces an apparent change in the experimentally determined branching ratio not necessarily related to chiral symmetry restoration. Comparisons to recent experimental measures at CERN energies reveal a possible mechanism to account for the shape of the observed spectra, though not their absolute relative magnitude.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. 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.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. 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.
    Type of Medium: Electronic Resource
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