| Institution: | (1) Univ. di Cagliari and INFN, Cagliari, Italy;(2) CERN, Geneva, Switzerland;(3) LPC, Univ. Blaise Pascal and CNRS-IN2P3, Clermont-Ferrand, France;(4) Univ. Heidelberg, Heidelberg, Germany;(5) IST-CFTP, Lisbon, Portugal;(6) IPN-Lyon, Univ. Claude Bernard Lyon-I and CNRS-IN2P3, Lyon, France;(7) LLR, Ecole Polytechnique and CNRS-IN2P3, Palaiseau, France;(8) RIKEN, Wako, Saitama, Japan;(9) SUNY, Stony Brook, NY, USA;(10) Univ. di Torino and INFN, Torino, Italy;(11) YerPhI, Yerevan, Armenia |
| Abstract: | NA60 is a fixed-target experiment at the CERN SPS which measured dimuon production in nucleus–nucleus and proton–nucleus collisions.
The experiment collected muon pair samples of unprecedented quality in heavy-ion experiments. This paper presents a high quality
measurement of the pT distribution of the φ meson, covering a broad pT window. The data were collected in 2003 in In-In collisions at 158 GeV per nucleon. The results, presented as a function
of centrality, were studied against several possible sources of systematic effects and proved to be fairly stable. We show
that the inverse mT slope measured in In-In collisions, in the φ→μμ decay channel, depends significantly on the range used to perform the fit.
When the fit is performed at low transverse momentum, the effective inverse slope increases from peripheral to central collisions,
as measured by other experiments. We finally show that our measurement for In-In is compatible with the overall systematics
of T slope versus mass, measured in different collision systems by the NA49 experiment
PACS 25.75.Nq; 25.75.-q; 25.75.Dw; 14.40.Cs; 12.38.Mh |
