1 / 23

f, (w+r) production in d-C d-U S-U and Pb-Pb reactions in the NA38-NA50 CERN SPS experiments

f, (w+r) production in d-C d-U S-U and Pb-Pb reactions in the NA38-NA50 CERN SPS experiments. D.Jouan, IPN Orsay, for the NA50 and NA38 collaborations. Muon spectrometer detects f, w and r mesons through their dimuon decay

genero
Télécharger la présentation

f, (w+r) production in d-C d-U S-U and Pb-Pb reactions in the NA38-NA50 CERN SPS experiments

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. f, (w+r)production in d-C d-U S-U and Pb-Pb reactions in the NA38-NA50 CERN SPS experiments D.Jouan, IPN Orsay, for the NA50 and NA38 collaborations Muon spectrometer detects f, w and r mesons through their dimuon decay The centrality of the collision is estimated on an event by event basis QM08, February 9h, 2008, Jaipur, India

  2. NA50 collaboration B.Alessandro10, C.Alexa3, R.Arnaldi10, M.Atayan12, A.Baldit2, S.Beolé10, V.Boldea3, P.Bordalo6,a, G.Borges6, J.Castor2, B.Chaurand9, B.Cheynis11, E.Chiavassa10, C.Cicalò4, M.P.Comets8, S.Constantinescu3, P.Cortese1 , A.De Falco4, N.De Marco10, G.Dellacasa1 , A.Devaux2, S.Dita3, O.Drapier9, J.Fargeix2, P.Force2, M.Gallio10, C.Gerschel8, P.Giubellino10, M.B.Golubeva7, M.Gonin9, A.Grigoryan13, J.Y.Grossiord11, F.F.Guber7, A.Guichard11, H.Gulkanyan12, M.Idzik10,b, D.Jouan8, T.L.Karavitcheva7, L.Kluberg9, A.B.Kurepin7, Y.Le Bornec8, C.Lourenço5, M.Mac Cormick8, A.Marzari-Chiesa10, M.Masera10, A.Masoni4, M.Monteno10, A.Musso10, P.Petiau9, A.Piccotti10, J.R.Pizzi11,d, F.Prino10, G.Puddu4 , C.Quintans6, L.Ramello1, S.Ramos6,a, L.Riccati10, A.Romana9,d, H.Santos6, P.Saturnini2, E.Scomparin10 , S.Serci4, R.Shahoyan6,c, M.Sitta1, P.Sonderegger5,a, X.Tarrago8, N.S.Topilskaya7, G.L.Usai4, E.Vercellin10, L.Villatte8, N.Willis8 , T.Wu8. 1) Univ. Del Piemonte Orientale, Alessandria and IFN-Torino, Italy 2)LPC, Univ. Blaise Pascal and CNRS-IN2P3, Aubière, France 3) IFA, Bucharest, Romania 4)Univ. di Cagliari/INFN, Cagliari, Italy 5)CERN, Geneva, Switzerland 6)LIP, Lisbon, Portugal 7)INR, Moscow, Russia 8)IPN, Univ. de Paris-Sud and CNRS-IN2P3, Orsay, France 9)LLR, Ecole Polytechnique and CNRS-IN2P3, Palaiseau, France 10)Univ. Torino/INFN, Torino, Italy 11)IPN, Univ. Claude Bernard Lyon-I and CNRS-IN2P3, Villeurbanne, France 12)YerPhI, Yerevan, Armenia. a) also at IST, Universidade Técnica de Lisboa, Lisbon, Portugal b) also at Faculty of Physics and Nuclear Techniques, AGH University of Science ant Technology, Cracow, Poland c) on leave of absence from YerPhI, Yerevan, Armenia d) Deceased

  3. Physics goals and data Goals Study of strangeness production in heavy ion collisions as strangeness enhancement has been proposed among the QGP formation signatures 1) Strange to non strange production is studied through the ratio 2) Cross sections, multiplicities … 3)f « puzzle »: new NA50 updated contribution Data considered in this talk (in red) p - W , d - C , d - U , S - S , S - Cu , S - U 200 GeV/nucleon Pb – Pb (1996, 1998 and 2000) 158 GeV/nucleon ( Focus on analyses as a function of MT)

  4. Kinematical domain Rapidity: 0 < ycm < 1 (tuned to beam energy) Angular window: 0 <  < 2p -0.5 < cos cs < 0.5 in Collins-Soper frame NA50 PbPb setup : magnetic field increased, (w.r.t. NA38) last 0.8 m of 4.8 m absorber changed from C to Fe f S-U w S-U For Pb-Pb, acceptances in the lowest MT bin considered are  0.3 % (!) f Pb-Pb Acceptance w Pb-Pb Comparison with Pb-Pb limited to : MT > 1.5 GeV/c2 MT (GeV/c2)

  5. Last Pb-Pb measurement in year 2000 • WITH UPGRADED SETUP • Better target identification, in particular for peripheral events: • single target in vacuum • vertex selection with multiplicity detector Improved rejection of out of target events Improved efficiency for low Et measurement • Min bias trigger upgrades: • Additional Beam Hod. MB trigger • Timing from BH for all triggers (µµ and MB (ZDC and BH))

  6. Analysis The opposite-sign muon pair invariant mass distributionmade of: • 1. Adimuonmass continuum(fromcomb. background, Dalitzdecays, etc...) 2. Muon pairs fromdecays of w, f, r isfitted,aftercomb. background subtraction (fromlike-sign pairs), assuming for production: • Breit-Wigner for resonances(+c.s.w = c.s.r,) • an exponential for the continuum : dN/dM exp(-M/M0) The MC simulation uses dN/dy  exp(-(y-y0)2/2s2) • dN/dMT  MT3/2exp(-MT/T) and Flat cosqcs

  7. as a function of centrality (Dimuons, acceptancecorrected) Integrated in MT MT > 1.5GeV/c2 f/(w+r)mm increases smoothly withNpart and with the size of the interacting nuclei Pb-Pb S-U d-U Meaning of f/(w+r)~1.2 ? d-C gS ~ 0.7 Npart

  8. 1.5< MT<1.8 f/w+r: no dependence on MT (f/w+r)mmIn a MT bin Pb-Pb 1.8< MT<2.2 f and w have close properties (masses) f/w is then mostly sensitive to the strangeness content (A.Shor) in thermodynamical models , MT is the relevant parameter for the production : in MT domains • f/w+rclosely related to gS2 In central Pb-Pb collisions: (+effect of strangeness saturation gS ,for s quarks) NO EXTRAPOLATION but Flow, secondary production, could nevertheless play a role Note: heregSmeansgS/gq

  9. Evolution of cross sectionvsd-A and AB a Parameterization: s = k Ab*Ba d-C vs d-U: Cronin, af~aw < 1 S-U vs d-U : af >> aw >1 b PbPb vs d-U: ~  similar  (assuming adU/dC for U->Pb) • af >> aw : increase of f production (strangeness enhancement) • 2 regimes for aw? (Increase of Projectile or target) MT 0<Y<1

  10. MT > 1.5GeV/c2 f increase or w-r decrease ? multf/npart (a.u.) • Between systems: af increase on top of a global a increase • With centrality: increase of f multiplicity per participant Nµµ/(NMB* Npart), ~flat for w-r multw-r/npart (a.u.)  The increase of f/(w-r) is due to an increase of the f Tao Wu PhDThesis, 2003 Npart

  11. d induced af and aw-r w.r.t. other measurements Fair agreement Very precise comparison should include the increase with PT and Y evolution

  12. T (GeV) The so-called f puzzle (I) MT Slopes measurements disagree between experiments….

  13. The so-called f puzzle (II) Multiplicitymeasurements disagree between experiments…. Central PbPb collisions Up to most recent papers: [NA45 - PRL 96 (2006) 152301] Also QM06, SQM07

  14. Times are changing: BR*104 change in f->µµ branching ratio+15% PDG BR values through the years (PDG « fit » value available since 2001) Universality: BRµµ expected to converge towards BRee (=> additional -4% on f multiplicity) NA50: new 2000 measurement: more precise trigger(s) timing, two minimum bias triggers NA50 Multiplicity is obtained from separate measurement of dimuons and collisions numbers

  15. Comparison of Pb-Pb multiplicities (I) (Pb-Au (7%) for CERES) CERES: PRL96-152301-2006 NA49: PLB 491 2000 59 /1996

  16. Comparison of Pb-Pb multiplicities (II) (Pb-Au (7%) for CERES) CERES: PRL96-152301-2006 NA49: PLB 491 2000 59

  17. Comparison of Pb-Pb multiplicities (III) (Pb-Au (7%) for CERES) CERES: PRL96-152301-2006 NA49: PLB 491 2000 59 Branching ratio for μμchange together with upgraded data collection and new sample and analysis lead to a lower multiplicity

  18. Comparison of Pb-Pb multiplicities (IV) (Pb-Au (7%) for CERES) CERES: PRL96-152301-2006 NA49: PLB 491 2000 59 The updated comparison plot

  19. Comparison of Pb-Pb multiplicities (Pb-Au (7% c.s.) for CERES) CERES: PRL96-152301-2006 NA49: PLB 491 2000 59 The most recent NA50 f multiplicity measurement is lower than the previous one but still disagrees by a factor ~2 with CERES and NA49 measurements in most of the MT domain (3%c.s.) 2 effects for NA50 now lower results: 1) 15% increase of BR 2) New 2000 measurement fluctuates by ~ -8% compared to previous (1996) one

  20. Are dilepton results compatible ? • BRµµ: still -4% compared to BRee Account could have to be taken of small difference: Eventually: correction for centrality domain: 3%  5% This leads to a 8% correction a visible effect anyway: NA50 and CERES dilepton results are quite compatible within large errors of CERES (e+e-) a difference between K+K- and l+l-decay channels ?

  21. At SPS energies, the production of f and w+rhave been compared for: • d-C, d-U, S-U and Pb-Pb, as a function of MT • Pb-Pb 2000 ismeasuredwith an upgraded set up. The ratio f/w+r • increases as a function of centrality (Npart or Et), • increases with the size of the interacting nuclei • is MT independent • Cross sections and multiplicities increase of f/wis due to f increase • new measurement of af and aw-rbetween d-C and d-U Summary incompatibilities in f puzzle ~solved: the updated f puzzle shows: • a smaller than previous, but remaining disagreement, a factor ~2, between NA50 (μμ) and CERES (KK), also NA49 (KK) • an agreement, within the large CERES (ee) errors, between: NA50 (μμ) and CERES (ee) • a differenceremains • between the hadronic and dileptondecaychannels

  22. Back up

  23. Why a specific reference is better W.Geist QM91 EPJC50_315 Fair agreement Very precise comparison should include the increase with PT and Y evolution

More Related