1. 09-05-05NA60 CERN meeting - Philippe PILLOT1 Status of the J/  analysis MC simulations Event selections Results on the J/  over DY ratio Results on J/  Results on T J/  Conclusion

2. 09-05-05NA60 CERN meeting - Philippe PILLOT2 MC simulations J/ ,  ’: NaGenParam dN/dp T = p T / [1 + (p T / p T0 ) 2 ]  p T0 and  adjusted to reproduce the distribution from pythia obtained with  kT = 1 GeV/c dN/dy = gaussian with y 0 = 2.92 and  = 0.6 DDbar: PYTHIA parton distribution function: GRV94_LO without nuclear effects M c = 1.35 GeV/c 2 k T distribution: gaussian with  kT = 1 GeV/c DY: PYTHIA parton distribution function: GRV94_LO weighted sum of p-p, p-n, n-p and n-n contributions without nuclear effects k T distribution: gaussian with  kT = 0.8 GeV/c Pythia y Lab from Data fitted with MC: NaGenParam (Positive fields)

3. 09-05-05NA60 CERN meeting - Philippe PILLOT3 Event selection at 4000A and 6500A  Dimuons T0J  IC  BS  0 vertex  tgt region (to avoid as much as possible non In-In interactions)  pDtarg 10%  Y lab  [2.92,3.92], Cos  CS  [-0.5,0.5]  Matched dimuons T0J  IC  BS  0 interaction vertex upstream the tgt region  Dimuon vertex = first interaction vertex (to avoid dimuons coming from re-interaction)  Cut on the correlation between M PC and M VT  Y lab  [2.92,3.92], Cos  CS  [-0.5,0.5] PC dimuons VT dimuons

4. 09-05-05NA60 CERN meeting - Philippe PILLOT4 Effect of the different selections at 4000A without the matching T0J IC BS 0 vtx  tgt pD targ kinematics -22% -21% -35% -20% -37% -14%

5. 09-05-05NA60 CERN meeting - Philippe PILLOT5 Effect of the different selections at 4000A Dimu T0J (-19%) IC (-21%) BS (-34%) (-85%) VT (-18%) Pdtarg (-20%) Kinematics (-44%) Matched dimu T0J (-17%) IC (-12%) BS (-30%) (-80%) VT (-25%) Fakes (-21%) Kinematics (-36%) E ZDC Mult VT

6. 09-05-05NA60 CERN meeting - Philippe PILLOT6 Definition of centrality bins 7 centrality bins 3 centrality bins

7. 09-05-05NA60 CERN meeting - Philippe PILLOT7 Effects of the T0J, IC, BS and M PC vs M VT selections on the previous results Modification of the selections with respect to the standard ones M VT M PC

8. 09-05-05NA60 CERN meeting - Philippe PILLOT8 Fit to the mass distribution Standard fitting procedure (Likelihood): BKG fixed from like sign pairs DY norm adjusted for M>4.2 GeV/c 2 DDbar norm adjusted in the mass range M  [2.2,2.5] GeV/c 2 J/  norm, M 0J/  and  J/ , and  ’norm (M 0  ’  M 0J/  and   ’   J/  ) adjusted in the mass range M  [2.9,4.2] GeV/c 2 Compatible results between 4000 A and 6500 A (< 2  ) J/  / DY = 18.6 ± 1.1 J/  / DY = 20.5 ± 1.5 PC dimuonsVT dimuons Mean values :

9. 09-05-05NA60 CERN meeting - Philippe PILLOT9 Check of systematic errors  modification of the selections: < ±2% if we keep at least the T0J selection  modification of the polarity of fields in simulation: < ±1%  modification of the J/  shape: ~ + 1or 2%  background estimation: < ±2% (PC dimuons) ; < ±1% (VT dimuons)  DDbar contribution (±50%): < ±2% (PC dimuons) ; < ±0.5% (VT dimuons)  other fitting procedure (- BKG from like sign - J/ ,  ’ and DY adjusted for M>2.9 GeV/c 2 - DDbar adjusted in the mass range [2.2,2.6] GeV/c 2 - J/ ,  ’ and DY adjusted for M>2.9 GeV/c 2 ): ~ –3% (PC dimuons) ; ~ –6% (VT dimuons)

10. 09-05-05NA60 CERN meeting - Philippe PILLOT10 Results on the J/  / DY ratio (GRV94_LO + isospin correction)

11. 09-05-05NA60 CERN meeting - Philippe PILLOT11 Analysis of p T distributions of the J/   Extraction of the distributions from opposite sign with M  [2.9,3.3] GeV/c 2.  Subtraction of BKG and DY contributions according to their relative abundance.  The BKG shape is obtained from the like sign pair.  The DY shape is obtained from O.S. with M > 4 Gev/c 2  Acceptance correction Compatible results between 4000 A and 6500 A (< 1.8  ) = 1.662 ± 0.010 = 1.669 ± 0.012 PC dimuonsVT dimuons Mean values : ( (GeV/c) 2 )

12. 09-05-05NA60 CERN meeting - Philippe PILLOT12 Check of systematic errors  modification of the selections: < ± 0.005 (GeV/c) 2 if we keep at least T0J  modification of the polarity of fields in simulation: < –0.005 (GeV/c) 2  without BKG and DY subtraction: < –0.010 (GeV/c) 2 (depend on the yield of BKG and DY)

13. 09-05-05NA60 CERN meeting - Philippe PILLOT13 Other statistical errors  statistical error in the BKG shape: ± 0.015 (GeV/c) 2 for PC dimuons at 4000 A for the most central bin  statistical error in the DY shape: ± 0.021 (GeV/c) 2 for PC dimuons at 4000 A for the most central bin

14. 09-05-05NA60 CERN meeting - Philippe PILLOT14 Results on the of the J/  Gluon multiple scattering model: = pp + a gN ·L

15. 09-05-05NA60 CERN meeting - Philippe PILLOT15 Analysis of M T distributions of the J/  Compatible results between 4000 A and 6500 A (< 1.6  ) T = 224.9 ± 1.3 MeVT = 225.4 ± 1.5 MeV PC dimuonsVT dimuons Mean values :  Extraction of the distributions from opposite sign with M  [2.9,3.3] GeV/c 2.  Subtraction of BKG and DY contributions according to there relative abundance.  The BKG shape is obtained from the like sign pair.  The DY shape is obtained from O.S. with M > 4 Gev/c 2  Acceptance correction  fit using a thermal model: — = a 0 · — ·K 1 ( — ) dN M T 2 M T dM T T T

16. 09-05-05NA60 CERN meeting - Philippe PILLOT16 Check of systematic errors  modification of the selections: < ± 0.5 MeV if we keep at least T0J  modification of the polarity of fields in simulation: < –0.5 MeV  without BKG and DY subtraction: < –1.4 MeV  fit for M T - M J/  > 0.03 GeV/c 2 : ~ +3 MeV  fit for M T - M J/   [0.03, 1] GeV/c 2 : ~ –2 MeV

17. 09-05-05NA60 CERN meeting - Philippe PILLOT17 Other statistical errors  statistical error in the BKG shape: ± 0.7 MeV for PC dimuons at 4000 A for the most central bin  statistical error in the DY shape: ± 0.8 MeV for PC dimuons at 4000 A for the most central bin

18. 09-05-05NA60 CERN meeting - Philippe PILLOT18 Results on T J/ 

19. 09-05-05NA60 CERN meeting - Philippe PILLOT19 Correlations between, and T

20. 09-05-05NA60 CERN meeting - Philippe PILLOT20Conclusion  Results obtained at 4000 A and 6500 A are compatible  Results obtained with PC dimuons and VT dimuons are compatible  Systematic errors are always lower than statistical ones  Results on the J/  over DY ratio are compatible with previous ones (from NA38 and NA50) when represented as a function of N part  Results on are compatible with the previous ones from NA50 and well reproduced by the gluon multiple scattering model  Results on T J/  are compatible with the ones from NA50 when represented as a function of L  Correlations between, and T J/  are compatible with the results of NA50 and show a small discrepancy with the thermal model (lower than statistical error)