The NA60 experiment at the CERN SPS first results and future perspectives Chiara Oppedisano for the NA60 Collaboration Study of prompt dimuon and charm production with proton and heavy ion beams at the CERN SPS Detector concept and physics programme Dimuon production in p-A collisions Charged particle pseudorapidity densities in Pb-Pb collisions Future perspectives SQM 2003, Atlantic Beach, NC, USA C. Oppedisano 1 Detector concept MUON SPECTROMETER ~1m Muon filter TARGET AREA ZDC and Quartz Blade Tracking MWPCs Toroidal Magnet Fe wall Trigger hodoscopes GOAL accurate measurement of muon kinematics Hadron absorber + muon spectrometer (NA50) no information at vertex level to distinguish prompt from decay muons Dipole field 2.5 T TARGET BOX BEAM BEAM TRACKER MUON FILTER TELESCOPE IC VERTEX TELESCOPE matching tracks in muon spectrometer and in vertex spectrometer MAGNETIC FIELD measurement of muon track momentum at vertex BEAM TRACKER measurement of interaction point to determine impact parameter of muon tracks SQM 2003, Atlantic Beach, NC, USA C. Oppedisano 2 Beam tracker and target system BEAM TRACKER Silicon micro-strip detectors 2 x-y stations upstream of target box cryogenic detector (T = 130K) radiation hardness 20 mm resolution on transverse coordinates of interaction point Online monitoring of beam profile Pb @ 20 A GeV TARGET SYSTEM Proton beam Be, In and Pb targets same beam normalization for all the nuclear targets Ion beams several thin sub-targets interaction rate comparable to a thick target reduced material traversed by muon in the angular acceptance of muon spectrometer SQM 2003, Atlantic Beach, NC, USA C. Oppedisano 3 Vertex telescope Vertex spectrometer placed in magnetic field accurate measurement of angle and momentum of tracks at the vertex, covering muon spectrometer angular acceptance p-A collisions Silicon MICROSTRIP and PIXEL detectors sensors divided in regions of variable strip pitch and length occupancy <3% 16 microstrip planes grouped in 8 tracking stations ~40 cm A-A collisions Silicon PIXEL detectors high occupancy high granularity and radiation hardness tracking planes 10 four-chip planes and 3 sixteen-chip planes Y (cm) ALICE1LHCB chips, pixel size (50 425) mm2 ~32 cm Expected mass resolution: 20 MeV at w peak Hitmap (Pb-Pb collision) SQM 2003, Atlantic Beach, NC, USA C. Oppedisano X (cm)4 Intermediate mass region excess With enhanced charm p-A collisions data described by Drell-Yan + charm decays Peripheral collisions S-U and Pb-Pb collisions dimuon yield exceeds the superposition of expected sources With expected charm yield IMR dimuon yields can be reproduced by: adding thermal radiation to Drell-Yan and open charm OR scaling up of charm contribution vs. centrality by up to a factor 3 dN/dM M(GeV) Central collisions NA60 separate open charm from thermal contribution SQM 2003, Atlantic Beach, NC, USA C. Oppedisano 5 Open charm tagging measure impact parameter of muon tracks separation of the two main contributions to IMR dimuon spectra: prompt dimuon sample from interaction vertex muon pairs from D decays with offset w.r.t. interaction point µ ~10 cm Muon filter vertex , K µ offset <1mm Dµ prompt dimuons Background PROMPT dN/dM dN/dM Offset distribution Background CHARM open charm Charm Prompt 0 100 200 300 400 500 600 700 Offset (mm) SQM 2003, Atlantic Beach, NC, USA C. Oppedisano M(GeV) M(GeV) 6 Charmonium production NA50 CHARMONIUM SUPPRESSION NA50 J/y suppression indication for onset of deconfinement cc melting NA60 better mass resolution yI and J/y clearly separated In-In collisions identification of the physics variable with threshold behavior D production is the best reference for J/y production study s(p-A) = s0 Aa A-DEPENDENCE OF cc PRODUCTION IN p-A COLLISIONS Around 30-40% of J/y comes from cc radiative decays E866 NA50 cc anomalously suppressed in semi-central Pb-Pb collisions p-A 800 GeV NA60 normal absorption pattern of cc measuring the cc to J/y ratio from p-Be to p-Pb SQM 2003, Atlantic Beach, NC, USA C. Oppedisano 7 Results from p-A data (I) Dimuon mass spectrum from muon spectrometer Data collected in June 2002 6 targets (1 In, 3 Be, 1 Pb, 1 Be) 2 mm thick Vertex telescope: 14 strip planes + 1 pixel plane Zvertex resolution ~ 900 mm Target identified by vertex telescope Dimuon spectrum for each target Zvertex distribution Muon track matching between vertex telescope and muon spectrometer Pb 250 p-Be 200 sw ~ 25 MeV In 150 sf ~ 30 MeV 100 Be Be Be Be 50 0 -4 -2 024 Z (cm)(cm) Zvertex SQM 2003, Atlantic Beach, NC, USA C. Oppedisano 8 Results from p-A data (II) Dimuon spectra after muon track matching: In and Pb targets p-In p-Pb dimuon mass resolution: ~ 25 MeV at the w peak and ~ 30 MeV at the f precise A-dependence of the w and f production (NA50 mass resolution for low masses ~ 90 MeV) Muon offset study little statistics to extract charm A-dependence SQM 2003, Atlantic Beach, NC, USA C. Oppedisano 9 Results from Pb-Pb data Pb-Pb collisions at 20 and 30 A GeV (October 2002) 3 Pb targets: 1.5, 1.0 and 0.5 mm thick dN/dZ Resolution on interaction vertex determination: σZ ~190 mm σX ~20 mm Pb targets Beam tracker sensor Target box window Xvertex from beam tracker (cm) Beam tracker vs. pixel telescope Xvertex from telescope (cm) Zvertex (cm) SQM 2003, Atlantic Beach, NC, USA Correlation width ~ 30 mm C. Oppedisano 10 Charged particle multiplicity measurement Multiplicities evaluated from clusters to access midrapidity Plane 1 - Target 1 Plane 1 - Target 3 Magnetic field switched off midrapidity midrapidity Geometrical acceptances depend on the considered plane-target set Centrality measured by ZDC dN/dh (0.1 h units) ZDC spectrum @ 30 GeV Beam trigger Interaction trigger 1 2 3 Plane 1 Data corrected for acceptance EZDC<1685 GeV 5% of total geometrical x-section SQM 2003, Atlantic Beach, NC, USA C. Oppedisano 11 dN/dh (0.1 h units) Corrections d rays (Pb+fragments) Plane 1 - Target 3 (worst case) d rays from Pb beam simulations with GEANT3.21 MC reliability tested with beam-trigger data Corrections factors calculated for each plane-target set d rays from fragments evaluated vs. centrality Correction factor for re-interaction from MC Plane 1 - Target 1 SQM 2003, Atlantic Beach, NC, USA dN/dh (0.1 h units) dN/dh (0.1 h units) Secondaries from re-interactions evaluated using UrQMD 1.2, leads to correction factors from 1.1 to 1.8 1 2 3 Plane 1 After MC corrections distributions in good agreement C. Oppedisano 12 Charged particle distributions Fit of dNch/dh distributions at 30 GeV hmax from data compatible with event generator value Systematic error ~11% (4% from residual data spread at same h, 9% on d-rays contribution, (dN/dh)/(0.5 Npart) dN/dh (0.1 h units) 3% on re-interaction factors, 5% on pixel plane efficiency) 30 GeV Npart h Centrality bin hmax (dN/dh)hmax 0-5 % 5-10% 10-20% 20-35% 2.1 ± 0.1 2.1 ± 0.1 1.9 ± 0.2 1.8 ± 0.2 172 ± 4 129 ± 4 98 ± 4 74 ± 6 SQM 2003, Atlantic Beach, NC, USA (dN/dh)/(0.5*Npart) 0.98 ± 0.02 (stat.) ± 0.11 (syst.) 0.87 ± 0.03 (stat.) ± 0.10 (syst.) 0.85 ± 0.03 (stat.) ± 0.09 (syst.) 0.91 ± 0.07 (stat.) ± 0.10 (syst.) C. Oppedisano 13 (dNch/dh)/(0.5*Npart) Npart estimated from Glauber fit to EZDC spectrum translation from laboratory to CMS frame Charged particle multiplicity per participant in Pb-Pb collisions for 5% most central events: 30 A GeV (dNch/dh)/(0.5*Npart) = 0.81 ± 0.02 (stat.) ± 0.09 (syst.) SQM 2003, Atlantic Beach, NC, USA C. Oppedisano 14 Summary and future perspectives Summary on data collected in 2002 p-A collisions: vertex telescope made of silicon strip (and pixel) planes dimuon mass resolution: ~25 MeV at the w peak, ~ 30 MeV for the f confirming expectation from simulations Pb-Pb collisions: vertex telescope in a partial configuration (only 3 pixel planes) resolution on coordinates of interaction point: ~190 mm on Zvertex ~ 20 mm on transverse coordinates measurement of charged particle pseudorapidity densities at 30 A GeV These results confirm the feasibility of the experiment and give good perspectives for next runs with proton and Indium beams SQM 2003, Atlantic Beach, NC, USA C. Oppedisano 15 NA60 Collaboration R. Arnaldi, K. Banicz, K. Borer, J. Buytaert, J. Castor, B. Chaurand, W. Chen, B. Cheynis, C. Cicalò, A. Colla, P. Cortese, A. David, A. de Falco, N. de Marco, A. Devaux, A. Devismes, A. Drees, L. Ducroux, H. En’yo, A. Ferretti, M. Floris, P. Force, A. Grigorian, J.Y. Grossiord, N. Guettet, A. Guichard, H. Gulkanian, J. Heuser, M. Keil, L. Kluberg, Z. Li, C. Lourenço, J. Lozano, F. Manso, A. Masoni, A. Neves, H. Ohnishi, C. Oppedisano, G. Puddu, E. Radermacher, P. Rosinský, E. Scomparin, J. Seixas, S. Serci, R. Shahoyan, E. Siddi, P. Sonderegger, G. Usai, H. Vardanyan and H. Wöhri 50 people, 12 institutes, 7 countries CERN Bern Palaiseau Riken BNL Yerevan Stony Brook Torino Lisbon Cagliari Clermont Lyon SQM 2003, Atlantic Beach, NC, USA C. Oppedisano 16