Latest results on charmonium (and open charm) at the CERN- SPS E. Scomparin (INFN – Torino, Italy) for the NA60 Collaboration Introduction Charmonium suppression in p-A and A-A collisions Preliminary results on the A-dependence of the open charm yield Conclusions

Charmonia suppression: pA, AA Study of charmonium production/suppression in pA/AA collisions THE hard probe at SPS energy AA collisions Color screening and charmonium suppression > 20 year long history pA collisions Production models (CSM, NRQCD, CEM, ....) Initial/final state nuclear effects (shadowing, dissociation,...) Reference for understanding dissociation in a hot medium

The NA60 experiment NA60, the third generation experiment studying quarkonia production at the CERN SPS hadron absorber Muon Other and tracking Muon trigger magnetic field Iron wall 2.5 T dipole magnet NA10/38/50 spectrometer beam tracker vertex tracker targets Matching in coordinate and momentum space Data samples In-In collisions at 158 GeV/nucleon p-A collisions at 158 and 400 GeV 9 nuclear targets, Al-U-W-Cu-In-Be1-Be2-Be3-Pb (mixed A-order to limit possible z-dependent systematics)

p-A collisions W Pb Cu In U Be Al Not enough DY statistics to extract (as in NA50) B J//DY target by target Pb Be In Cu W U Al Estimate of nuclear effects through relative cross sections: all targets simultaneously on the beam beam luminosity factors Niinc cancel out (apart from a small beam attenuation factor)  no systematic errors  acceptance and recostruction efficiencies do not completely cancel out (these quantities and their time evolution are computed for each target)  each target sees the vertex spectrometer under a (slightly) different angle: kinematic window is restricted, to reduce systematic (0.28<ycm<0.78 at 158GeV and -0.17<ycm<0.33 at 400GeV)

A-dependence of relative cross sections 400 GeV 158 GeV  increasing suppression of the J/ yield as a function of A larger suppression at 158GeV using a Glauber fit to extract abs 158 GeV: abs J/ = 7.6 ± 0.7 ± 0.6 mb 400 GeV: abs J/ = 4.3 ± 0.8 ± 0.6 mb NA60 Coll., arXiv:1004.5523 very good agreement with NA50 (4.6 ± 0.6mb) shadowing neglected, as usually done at fixed target (but not correct!) using 158 GeV: = 0.882 ± 0.009 ± 0.008 400 GeV:  = 0.927 ± 0.013 ± 0.009 systematic errors due to : target thicknesses (<1.5%)‏ J/ y distribution (<1.5%)‏ reconstruction eff. calculation (<3%)‏

 vs xF NA60 pA results can be compared with  values from other experiments (HERAB, E866, NA50 and NA3) E. Scomparin et al., Nucl. Phys. A830 (2009) 239 In the region close to xF=0, increase of  with √s NA60 400 GeV very good agreement with NA50 NA60 158 GeV: smaller , hints of a decrease towards high xF ? discrepancy with NA3 Systematic error on  for NA60 points ~0.01

 vs x2 Shadowing effects and final state absorption (in the 21 approach) should scale with x2, since If parton shadowing and final state absorption were the only relevant mechanisms   should not depend on √s at constant x2 NA60 data (two energies in the same experimental conditions)  reduced systematics on  NA60 Δα(400-158 GeV)  x2   0 in the explored x2 range clearly other effects should be present NA60 Coll., arXiv:1004.5523

Reference for AA data CNM effects, evaluated in pA, can be extrapolated to AA, assuming a scaling with the L variable and taking into account that: abs shows an energy/kinematical dependence reference obtained from 158 GeV pA data (same energy/kinematical range as the AA data) in AA collisions, shadowing affects both projectile and target proj. and target antishadowing taken into account in the reference determination The current reference is based on: slope determined only from pA@158GeV abs J/ (158 GeV) = 7.6 ± 0.7 ± 0.6 mb Nuclear effects scale with L…Se uso solo pA PC point: 8% error. Con SU 3%. Differenza slopes 0.3 sigma normalization to J/pp determined from pA@158 GeV (J//DY point) and (to reduce the overall error) SU@200GeV SU has been included in the fit, since it has a slope similar to pA at 158 GeV advantage: small error on normalization (3%) drawback: hypothesis that SU is “normal”‏

Anomalous suppression In-In 158 GeV (NA60) Pb-Pb 158 GeV (NA50) Using the previously defined reference: Central Pb-Pb:  still anomalously suppressed In-In: almost no anomalous suppression Ratio measured over expected B. Alessandro et al., EPJC39 (2005) 335 R. Arnaldi et al., Nucl. Phys. A830 (2009) 345 R.Arnaldi, P. Cortese, E. Scomparin Phys. Rev. C 81 (2009), 014903

New result: J/ cross section in pA J/ production cross sections for pA data Preliminary Banda blu-> errore su sigma e normalizzazione (1 sigma) Systematic error on (absolute) luminosity estimation quite high Relative luminosity estimate between 158 and 400 GeV much better known (~2-3% systematic error) Normalize NA60 400 GeV cross section ratios to NA50 results 158 GeV cross sections constrained by the relative normalization

New reference using J/ cross sections Alternative approach for the normalization of the pA reference curve based on the pA J/ absolute cross section To fully profit from this approach, a measurement of the absolute J/ cross section in In-In would be needed. For the moment… J//DY values are obtained rescaling the DY cross section measured at 450 GeV by NA50 (not enough statistics at 158 GeV) Main advantage: no assumption on SU, since it is not used anymore in the fit Preliminary No practical consequence on anomalous J/Ψ suppression difference with previous CNM reference ~1% well within errors

Anomalous suppression: SPS vs RHIC SPS results compared with RHIC RAA results normalized to RAA(CNM) Both Pb-Pb and Au-Au seem to depart from the reference curve at Npart~200 For central collisions more important suppression in Au-Au with respect to Pb-Pb M. Leitch (E866), workshop on “Quarkonium in Hot Media:From QCD to Experiment”, Seattle 2009 Agreement between SPS and RHIC results as a function of the charged particle multiplicity

Other pA results: pT distributions <pT2>= <pT2>pp+  (A1/3-1) NA60 158 GeV R. Arnaldi et al., Nucl. Phys. A830 (2009) 345 pT broadening observed (usually ascribed to Cronin effect) NA60 results suggest a smaller broadening at low √s NA3 result similar to higher √s values agreement NA60 vs NA50 at 400 GeV

Other pA results: polarization Helicity  compatible with zero everywhere no large differences between NA60, HERAB and PHENIX as observed by HERAB, |λHE|< |λCS| p-A 158 GeV HE CS R. Arnaldi et al., Nucl. Phys. A830 (2009) 345

Other AA results: polarization First full measurement of the J/ angular distribution in nuclear collisions vs. pT vs. centrality Polarization is rather small everywhere: no pT or centrality dependence Positive azimuthal coefficient at low pT? Polarization in AA may be influenced by the hot medium  quantitative predictions needed! R. Arnaldi et al., Nucl. Phys. A830 (2009) 345

Open charm production in p-A collisions Open charm share initial state effects with charmonium  a measurement of open charm in p-A collisions may help in understanding J/ suppression Recent results from SELEX and E866 suggest rather strong nuclear effects on open charm E866/NuSea Preliminary A. Blanco et al. (SELEX), EPJC64(2009) 637 M. Leitch (E866), workshop on “Heavy Quarkonia Production in Heavy-Ion Collisions”, ECT* 2009

Open charm dimuons in p-A: NA60 NA50 tried to evaluate DD production studying the IMR in pA Large background levels (S/B ~0.05 at m = 1.5 GeV/c2) NA50 had to impose a constant DD/DY vs A (i.e. DD= DY ~1 ) M.C. Abreu et al., EPJC14(2000) 443 NA60 is much better placed, thanks to the muon matching  S/B is ~60 times more favourable

Open charm dimuons in p-A: NA60 High-mass DY statistics is low in NA60 Use the ratios /DY from NA50 (EPJC48(2006)329) to fix the DY contribution Good resolution on the longitudinal position of the vertex in the IMR (no problem in target assignment) DD DY Results given for the 400 GeV sample only (at 158 GeV DD contribution much smaller than DY)

Open charm dimuons in p-A: results Kinematic range: 3.2<ylab<3.7 (-0.17<ycm<0.33) Study the ratio /DD (reduce systematic errors) Preliminary Systematic errors Fit starting point Track 2 /DY (norm. and J/) Background normalization Using the measured J/ value one gets DD = 0.960.03 Anti-shadowing would suggest DD >1

Conclusions NA60: physics analysis still ongoing In the charmonium and open charm sector Detailed studies of charmonium suppression in pA Nuclear effects stronger when decreasing √s Build CNM reference with pA data taken in the same energy/kinematic domain of AA Look for anomalous suppression in In-In and Pb-Pb Observed in central Pb-Pb collisions In In-In almost no anomalous suppression Open charm in pA can be studied looking at the IMR dimuons Very preliminary results for pA at 400 GeV: DD close to 1