arXiv subjects

NA44 Collaboration

Publications and source records attributed to NA44 Collaboration.

6 recordsLinked to original sources

arXiv2003

High transverse mass pion and proton correlations in central PbPb collisions at 17GeV/nucleon

For central PbPb collisions at a center of mass energy of 17.3 GeV/nucleon we have made the first two-dimensional measurement of the pp correlation function. These data extend the range of previous studies of HBT radii by a factor of two in transverse mass. They are consistent with a hydrodynamic interpretation and microscopic models that include hadronic rescattering and transverse expansion. We also report new data on pion correlations. The two particle correlations of negative pions at a transverse mass of 0.92 GeV imply source radii that are smaller than typical hydrodynamic fits and transport model simulations. It is possible that these fast pions may have left the source before the build up of hydrodynamic flow.

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arXiv2001

Two-kaon correlations in central Pb + Pb collisions at 158 A GeV/c

Two-particle interferometry of positive kaons is studied in Pb + Pb collisions at mean transverse momenta $ \approx 0.25$ and 0.91 GeV/c. A three-dimensional analysis was applied to the lower $p_T$ data, while a two-dimensional analysis was used for the higher $p_T$ data. We find that the source size parameters are consistent with the $m_T$ scaling curve observed in pion correlation measurements in the same collisions, and that the duration time of kaon emission is consistent with zero within the experimental sensitivity.

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arXiv1999

Two-Proton Correlations near Midrapidity in p+Pb and S+Pb Collisions at the CERN SPS

Correlations of two protons emitted near midrapidity in p+Pb collisions at 450 GeV/c and S+Pb collisions at 200A GeV/c are presented, as measured by the NA44 Experiment. The correlation effect, which arises as a result of final state interactions and Fermi-Dirac statistics, is related to the space-time characteristics of proton emission. The measured source sizes are smaller than the size of the target lead nucleus but larger than the sizes of the projectiles. A dependence on the collision centrality is observed; the source size increases with decreasing impact parameter. Proton source sizes near midrapidity appear to be smaller than those of pions in the same interactions. Quantitative agreement with the results of RQMD (v1.08) simulations is found for p+Pb collisions. For S+Pb collisions the measured correlation effect is somewhat weaker than that predicted by the model simulations, implying either a larger source size or larger contribution of protons from long-lived particle decays.

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arXiv1998

Charged Kaon and Pion Production at Midrapidity in Proton Nucleus and Sulphur Nucleus Collisions

The NA44 collaboration has measured charged kaon and pion distributions at midrapidity in sulphur and proton collisions with nuclear targets at 200 and 450 GeV/c per nucleon, respectively. The inverse slopes of kaons are larger than those of pions. The difference in the inverse slopes of pions, kaons and protons, all measured in our spectrometer, increases with system size and is consistent with the buildup of collective flow for larger systems. The target dependence of both the yields and inverse slopes is stronger for the sulphur beam suggesting the increased importance of secondary rescattering for SA reactions. The rapidity density, dN/dy, of both K+ and K- increases more rapidly with system size than for pi+ in a similar rapidity region. This trend continues with increasing centrality, and according to RQMD, it is caused by secondary reactions between mesons and baryons. The K-/K+ ratio falls with increasing system size but more slowly than the pbar/p ratio. The pi-/pi+ ratio is close to unity for all systems. From pBe to SPb the K+/p ratio decreases while K-/pbar increases and ({K+*K-}/{p*pbar})**1/2 stays constant. These data suggest that as larger nuclei collide, the resulting system has a larger transverse expansion, baryon density and an increasing fraction of strange quarks.

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arXiv1997

Proton and Antiproton Distributions at Mid-Rapidity in Proton-Nucleus and Sulphur-Nucleus Collisions

Experiment NA44 has measured proton and antiproton distributions at mid-rapidity in sulphur and proton collisions with nuclear targets at 200 and 450 GeV/c per nucleon respectively. The inverse slopes of transverse mass distributions increase with system size for both protons and antiprotons but are slightly lower for antiprotons. this could happen if antiprotons are annihilated in the nuclear medium. The antiproton yield increases with system size and centrality and is largest at mid-rapdity. The proton yield also increases with system size and centrality, but decreases from backward rapidity to midrapidity. The stopping of protons at these energies lies between the full stopping and nuclear transparency scenarios. The data are in reasonable agreement with RQMD predictions except for the antiproton yields from sulphur-nucleus collisions. PACS numbers 25.75.-q 13.85.-t 13.60.Rj

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arXiv1997

Protons, Deuterons and Flow

Proton and deuteron m_T spectra and rapidity densities at y=1.9-2.3 are presented for central SS, SPb and PbPb collisions. The inverse slopes increase with system size and mass. The radius parameter, R_G, extracted from ratios of the spectra increases with system size. R_G is proportional to 1/\sqrt{m_T} consistent with transverse flow and NA44's HBT results.

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