Kluberg, Louis

Musso, Alfredo

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Ref: CERN / SPSC 2003-004SPSC-M-694Date: January 7, 2003MEMORANDUMFrom/De : Louis Kluberg for the NA50 CollaborationTo/a : SPS CommitteeSubject/Sujet : Status report on experiment NA50The NA50 Collaboration has devoted its eorts during the past year 2002 to proceed withthe analysis of various sets of data and publication of results. A special eort has been done,in particular, on the analysis of the Pb-Pb data collected during the fall of year 2000. TheCollaboration has also nished the analysis of two samples (out of three) of proton data collectedduring various dierent proton beam periods, from 1996 to 2000, which are to be used as theexperimental reference for the Pb-Pb results.As a result, we have published or submitted for publication the following articles:P1.Scaling of charged particle multiplicity in Pb-Pb collisions at SPS energiesPhysics Letters B 530 (2002) 43; CERN-EP-2002-018.P2.Pseudorapidity distributions of charged particles as a function of centrality in Pb-Pb collisionsat 158 and 40 GeV per nucleon incident energyPhysics Letters B 530 (2002) 33; CERN-EP-2002-017.P3.Phi production in Pb-Pb collisions at 158 GeV/c per nucleon incident momentum.Accepted by Physics Letters B.P4.Charmonia and Drell-Yan production in proton-nucleus collisions at the CERN SPS.Accepted by Physics Letters B.We have also been able, after an intense collective eort during the past months of May andJune to present, at the International Conference Quark Matter 2002, Nantes, July 2002, ourrst preliminary results on J/ suppression, based on our very last set of Pb-Pb data collectedin year 2000. At this Conference, we made the three following presentations of new results:C1.Results on leptonic probes from NA50C2. Charmonia absorption in p-A collisions at the CERN SPS: results and implications onPb-Pb interactionsC3. Transverse momentum distributions of J/Psi produced in Pb-Pb and p-A interactions atthe CERN SPSStatus report on experiment NA50 January 7, 2003 Page 2We also presented our preliminary results based on our most recent data both at ICHEP2002and at ISMD2002.Finally, we are now preparing for submission to Physics Letters BCharmonia production and suppression in p-A interactions at 450 GeV.andFission cross-section of lead projectilesin Pb-nucleus interactions at 40 and 158 AGeV.This analysis work has involved both senior and young colleagues. Progress was made throughinternal presentations and discussions that took place in seven Collaboration meetings held atCERN, as well as in several working sessions, also held at CERN, on the eve of the QuarkMatter Conference. An important side-result of the accomplished work are several PhD thesisdefended, during the year, in various institutions.Although, as can be seen, we have made signicant progress, in particular in the analysis ofour year 2000 data, we are still in a position where we need several months to bring to theirnal status the analysis of the data on various physics subjects and write, eventually, the cor-responding publications. The work, still to be done, includes:1. Final results on J/psi suppression from the year 2000 data2. Study of the J/psi transverse momentum from the year 2000 data3. Study of the low mass resonances (, ! and ) from the year 2000 data4. Analysis of the last proton target data sample which was collected in year 2000 withthe aim of minimizing systematic eects in the comparison of the results from dierenttargets5. Flow studies from the anisotropy of energy and multiplicity azimuthal distributionsWe hope to be able to carry this analysis and publication program to its end during thenext months and would like therefore that Experiment NA50 is still considered as an activeexperiment at CERN for one more year.Status report on experiment NA50 January 7, 2003 Page 3 KDY=1.80 0.04-------------------------------------------------------------- (MRS 43)Figure 1: The ratio of measured to com-puted (MRS 43) Drell-Yan cross-sections fromNA51, NA38 and NA50 experiments showingthat the Drell-Yan yield is proportional to thenumber of nucleon-nucleon collisions from p-pup to Pb-Pb interactions.L (fm)Bµµσ(J/ψ)/σ(DY)pp, pd 450 GeVpA 450 GeVpA 200 GeVSU 200 GeVψ/DY20304050600 1 2 3 4 5 6 7 8Figure 2: The J/ /DY ratio vs. L at twodierent beam energies and kinematical do-mains, from NA51, NA38 and NA50 data.The line is a Glauber t to the data with acommon value for the J/ absorption cross-section, independent from the colliding sys-tems and the kinematical conditions. The tleads to abs= 4:4  0:5 mb.ET (GeV)B µµσ(J/ψ)/σ(DY)2.9-4.5σ(abs) = 4.4 mbPb-Pb 2000  - analysis APb-Pb 2000  - analysis BPb-Pb 2000  - analysis C05101520253035400 20 40 60 80 100 120 140Figure 3: The J/ /DY ratio vs. ET. Prelim-inary results, based on dimuon events only,from three independent analysis of the samedata.σ(abs) = 4.4 mb 2000 preliminaryEZDC (TeV)B µµσ(J/ψ)/σ(DY) 2.9-4.505101520253035400 5 10 15 20 25 30 35Figure 4: The J/ /DY ratio vs. EZDC. Pre-liminary results, based on dimuon trigerredevents only.Status report on experiment NA50 January 7, 2003 Page 4ET (GeV)B µµσ(J/ψ)/σ(DY)2.9-4.5σ(abs) = 4.4 mbPb-Pb 1995 - publishedPb-Pb 1998 - reanalysisPb-Pb 2000  - analysis BPb-Pb 2000  - analysis CPb-Pb 2000  - EZDC → ET05101520253035400 20 40 60 80 100 120 140Figure 5: The J/ /DY ratio vs. transverseenergy for the 2000 (preliminary results) andprevious years runs.σ(abs) = 4.4 mb 1996 published 1998 published 2000 preliminaryEZDC (TeV)B µµσ(J/ψ)/σ(DY)2.9-4.50510152025303540450 5 10 15 20 25 30 35Figure 6: The J/ /DY ratio vs. forward en-ergy for the 1996, 1998 and 2000 runs.

Status report on experiment NA50

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