J/   analysis: results for ICHEP Presentation based on: Several weekly discussions inside PWG3-muon and PWG3 The work of many people inside the muon group (calibration, alignment, analysis....) Today Summary of the main results that have been proposed to be shown next week at ICHEP E.S., July 15, 2010

Data sample The following results are based on the data samples: LHC10b (runs 114916-117222) – pass2 LHC10c1 (runs 118903-120242) – pass2 LHC10c2 (runs 120476-120824) – pass2 LHC10d (runs 122372-125296) – pass1 These periods correspond to slightly different configurations of the muon spectrometer. In particular, LHC10c has been splitted in two parts (LHC10c1: full trigger coverage, LHC10c2: problems in half of the trigger chambers)

Total available statistics  0 match  1 match 2 match Kinematic cut: 2.5<y<4 Fit: gaussian+exponential NJ/ M (Gev/c2)  (GeV) S/B 2.9 - 3.3  0 match 1285 ± 75 3.118±0.004 0.095 ± 0.004 1.66 1 match 1277 ± 73 3.115±0.004 0.096 ± 0.004 1.77 = 2 match 884 ± 59 3.110±0.005 0.103 ± 0.004 2.49 CINT1B 191 E6 CMUS1B 8 E6

Statistics per period (1) LHC10b NJ/ M (Gev/c2)  (GeV) S/B 2.9 - 3.3 0 match 70±18 3.115±0.018 0.094±0.015 1.17 1 match 73±18 3.107±0.017 0.096±0.016 1.57 =2 match 52±13 3.092±0.016 0.084±0.014 2.25 CINT1B 34 E6 CMUS1B 0.45 E6 LHC10c1 NJ/ M (Gev/c2)  (GeV) S/B 2.9 - 3.3 0 match 324±36 3.123±0.008 0.098±0.007 1.77 1 match 320±35 3.120±0.008 0.098±0.006 1.91 =2 match 268±31 3.121±0.009 0.106±0.007 2.62 CINT1B 59 E6 CMUS1B 1.9 E6 LHC10c2 NJ/ M (Gev/c2)  (GeV) S/B 2.9 - 3.3 0 match 152±27 3.135±0.011 0.086±0.010 1.60 1 match 137±26 3.130±0.011 0.086±0.011 1.69 =2 match 30±11 3.128±0.022 0.083±0.021 2.76 CINT1B 28 E6 CMUS1B 0.6 E6

Statistics per period (2) Current period (runs 122372-125296) LHC10d NJ/ M (Gev/c2)  (GeV) S/B 2.9 - 3.3  0 match 727 ± 59 3.117 ± 0.005 0.093 ± 0.005 1.42 1 match 728 ± 57 3.112 ± 0.005 0.093 ± 0.007 1.56 = 2 match 534 ± 47 3.107 ± 0.006 0.102 ± 0.006 2.42 CINT1B 69 E6 CMUS1B 4.7 E6 Almost all these J/ were collected with the high intensity beams. Unfortunately, the amount of J/ collected with the displaced beams (Jul 1st – Jul 6th) is negligible (runs 124750 – 125296) CINT1B 34 E6 CMUS1B 0.8 E6 NJ/  0 match 97 ± 23

Study of pT distributions 1<pT< 2 GeV/c 2<pT< 3 GeV/c 0<pT< 1 GeV/c (0 match) 3<pT< 4 GeV/c 4<pT< 5 GeV/c 5<pT< 10 GeV/c

Comparison with “realistic” simulations Invariant mass fits, in pT bins, with J/ pole and resolution as free parameters Simulations of the J/ signal now include Residual misalignment Realistic tracking/trigger efficiency, period by period Data Monte-Carlo Good agreement data vs Monte-Carlo, for the J/ mass resolution !

Acceptance/efficiency calculation Based on pure signal generation, with realistic kinematic distributions CDF pp 7 parameterization (AliGenMUONlib) pT extrapolated from CDF results y obtained from CEM calculations No polarization ( = 0) Slightly lower efficiency of the tracking for the LHC10d period Does not vary strongly as a function of pT (0 match)

pT spectra corrected for acceptance/efficiency LHC10c1 LHC10c2 LHC10d Integral of the spectra normalized to 1 After correcting the spectrum corresponding to each period with its own efficiency, we get a good relative agreement  sum the spectra LHC10b discarded (too low statistics)

Total pT spectrum The efficiency corrected pT spectrum still misses an absolute normalization. However, its shape can be compared with Monte-Carlo and pT and pT2 can be computed Our corrected J/ pT spectrum is softer than the CDF extrapolation Data Monte Carlo

pT and pT2 Two possibilities Fit the pT spectrum with a suitable function Advantage: can be extrapolated to pT   Drawback: function-dependent 2) Extract pT and pT2 directly from data Advantage: not model dependent Drawback: results depend on pT reach of the measurement Previous experiments (including PHENIX) have used the function First proposed by Yoh et al., PRL 41 (1978) 684 No physics content, only phenomenological With this choice one simlply has pT2=p02/4, pT=(35/256)p0

Fit of J/ pT distribution We get 2/ndf = 0.47 p0 = 6.0 ± 0.2 GeV/c which leads to pT2 = 9.08 ± 0.54 (GeV/c)2 pT = 2.59 ± 0.08 GeV/c Can be compared with other experimental results, obtained with a fitting approach

Comparison with previous experiments

Stability vs LHC period As a test of our efficiency correction procedure, we can check if pT2 and pT are stable with respect to the various considered periods Results are quite stable over the whole data taking

Systematic errors It is of course possible to extract the pT2 directly from the data, as This gives pT2 = 8.2 (GeV/c)2 which is obviously smaller than the previous estimate, due to the fact that our pT reach is finite If we truncate the function at our maximum pT reach, we get pT2 = 7.8 (GeV/c)2, a value similar to the one quoted above

Rapidity distribution With the available statistics we can compute the rapidity distribution of the J/ in 5 bins, using an approach identical to the one adopted for the pT distributions dN/dy(a.u.) MC There are some deviations wrt the Monte-Carlo Data Edge effect due to acceptance falling down at the upper and lower limit of our coverage ? Suggestion: remove edges  we have now re-done this analysis in 5 bins in the interval 2.7<y<3.8

Rapidity distribution (2.7<y<3.8) MC Data Follows more closely the MC behaviour Probably healthier to remove the edges of the rapidity domain

Conclusions Proposal for ICHEP presentation(s), as emerged from the PWG3 rehearsal meeting of Tuesday Data Monte Carlo MC 2/ndf = 0.47

Backup

Mass spectra -3.8<y<-3.58 -3.58<y<-3.36

Comparison with Monte-Carlo Rather good agreement of the mass resolution between data and Monte-Carlo Data Monte-Carlo