1 / 27

J/  production in In-In and p-A collisions

J/  production in In-In and p-A collisions. Introduction Centrality dependence of J/  and ’ suppression in In-In collisions (Preliminary) results on J/ and ’ production in p-A collisions Transverse momentum and rapidity distributions Polarization Outlook/conclusions.

danielle-green
Download Presentation

J/  production in In-In and p-A collisions

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. J/ production in In-In and p-A collisions • Introduction • Centrality dependence of J/ and ’ suppression in In-In collisions • (Preliminary) results on J/ and ’ production in p-A collisions • Transverse momentum and rapidity distributions • Polarization • Outlook/conclusions E. Scomparin for the NA60 Collaboration

  2. J/ suppression in nuclear collisions • At CERN SPS energy (s ~ 20 GeV/nucleon) •  Study the onset of deconfinement (Matsui and Satz, 1986) from H. Satz, hep-ph/0609197 • Previous knowledge • 1986 – 1992: NA38 experiment (light ions and protons) • 1994 – 2000: NA50 experiment (Pb ions and protons) • Main topics (to be) studied • Normal vs anomalous suppression  needs accurate p-A data • Scaling variables(s) for the onset of the anomaly •  needs comparison between different colliding systems • J/ vs c vs ’ suppression • needs high statistics (’) • needs a sophisticated apparatus (c  J/ )  Issues presently addressed by NA60

  3. Results from p-A and Pb-Pb L. Ramello (NA50), Quark Matter 2005 • Absorption in cold nuclear matter (p-A) can explain S-U data • Anomalous suppression sets in for semi-peripheral Pb-Pb collisions • But • p-A data taken in a different energy/kinematic range • Is there anomalous suppression for systems lighter than Pb-Pb ?

  4. Muon trigger and tracking 2.5 T dipole magnet NA10/38/50 spectrometer beam tracker vertex tracker Iron wall magnetic field targets ZDC hadron absorber Matching in coordinate and momentum space Muon Other The NA60 experiment • In-In @ 158 GeV/nucleon ~ 2×108 dimuon triggers collected • 2 event samples • Set A (low ACM current)  mass resolution @ J/ ~125 MeV • Set B (high ACM current)  mass resolution @ J/ ~105 MeV • After muon matching mass resolution @ J/ ~ 70 MeV • Both sets are used for J/ analysis  maximize statistics • Improved reconstruction algorithm and alignment with respect • to QM2005 (~1 m accuracy)

  5. Event selection • 2 event selections have been used for J/ analysis • 1) • No matching required • Extrapolation of muon tracks must lie in the target region • Higher statistics • Poor vertex resolution (~1 cm) • 2) • Matching between muon tracks and vertex spectrometer tracks • Dimuon vertex in the most upstream interaction vertex • (MC correction to account for centrality bias due to fragment reinteraction) • Better control of systematics • Good vertex resolution (~200 m) • Lose 40% of the statistics • After quality cuts  NJ/ ~ 45000 (1), 29000 (2) • 2 analyses • a) Use selection 1 and normalize to Drell-Yan • b) Use selection 2 and normalize to calculated J/ nuclear absorption

  6. J/ / DY vs. centrality (analysis a) Anomalous suppressionpresent in Indium-Indium • Qualitative agreement with • NA50 results plotted as a • function of Npart • Data points have been normalized to the expected J/ normal nuclear • absorption, calculated with • as measured with p-A NA50 data • at 400 and 450 GeV J/abs = 4.18  0.35 mb B. Alessandro et al., Eur. Phys. J. C39(2005) 335 bin1  Npart = 63 (EZDC> 11 TeV) bin2  Npart = 123 (7< EZDC< 11 TeV) bin3  Npart = 175 (EZDC< 7 TeV) 3 centrality bins, defined through EZDC

  7. J/ yield vs nuclear absorption (analysis b) • Compare data to the expected J/ centrality distribution, calculated • assuming nuclear absorption (with abs =4.18 mb) as the only • suppression source Nuclear absorption require the ratio measured/expected, integrated over centrality, to be equal to the same quantity from the (J/)/DY analysis (0.87 ± 0.05) Normalization of the nuclear absorption curve

  8. Results and systematic errors • Small statistical errors • Careful study of systematic • errors is needed • Sources • Uncertainty on normal • nuclear absorption parameters • (abs(J/) and pp(J/)) • Uncertainty on relative • normalization between data • and absorption curve • Uncertainty on centrality • determination (affects relative • position of data and abs. curve) • Glauber model parameters • EZDC to Npart • ~10% error centrality indep. does not affect shape of the distribution • Partly common to analyses a and b • (Most) Central points affected by a considerable error

  9. Comparison with previous results (vs Npart) • NA50: Npart estimated through ET(left), or EZDC (right, as in NA60) • Good agreement with PbPb • S-U data seem to show a different behavior

  10. Various centrality estimators (,l) • Suppression vs energy density and fireball’s transverse size • Anomalous suppression sets in at  ~ 1.5 GeV/fm3 (0=1 fm/c) • What is the best scaling variable for the onset? •  Clear answer requires more accurate Pb-Pb suppression pattern

  11. Comparison with theoretical predictions A. Capella, E. Ferreiro EPJ C42(2005) 419 R.Rapp, EPJ C43(2005) 91 S. Digal, S. Fortunato, H. Satz, EPJ C32(2004) 547 centrality dependent t0 fixed termalization time t0 Dissociation and regeneration in QGP and hadron gas Percolation, with onset of suppression at Npart~140 Suppression by hadronic comovers (co = 0.65 mb, tuned for Pb-Pb collisions) • Size of the anomalous suppression reasonably reproduced • Quantitative description not satisfactory

  12. Maximum hadronic absorption • Compare J/ yield to • calculations assuming • Nuclear absorption • Maximum possible • absorption in a • hadron gas • (T = 180 MeV) L. Maiani et al., Nucl.Phys. A748(2005) 209 F. Becattini et al.,Phys. Lett. B632(2006) 233 • Both Pb-Pb and (to a lesser extent) In-In show extra-suppression

  13. We see a nice scaling (really surprising....) Coherent interpretation of SPS vs RHIC challenge for theorists Work in this direction has already started (see e.g. Karsch, Kharzeev and Satz, PLB 637(2006) 75) Comparison between SPS and RHIC • Plot J/ yield vs Npart ,normalized to collision scaling expectations

  14. ’ suppression in In-In collisions • Use selection 2 (matching of muon spectrometer tracks) • Study limited by statistics (N’~ 300) • Normalized to Drell-Yan yields 450, 400 and 200 GeV points rescaled to 158 GeV • Most peripheral point • (Npart ~ 60) does not show • an anomalous suppression • Good agreement with • Pb-Pb results Preliminary

  15. W Pb Cu In U Be Al p-A collisions at 158 GeV • Accurate proton data are an essential reference for A-A • NA60 has taken p-A data at 158 GeV Obtain for the first time at SPS energy information on nuclear absorption and production yields at the same energy of A-A data All targets • Reduce systematic errors on the reference curve for A-A collisions, • due to energy and kinematic rescaling

  16. 2/ndf = 1.24 DY J/, ’ DD Data analysis • Final analysis needs a complete understanding of the (local) • efficiency of the vertex spectrometer  still in progress • For the moment use info from muon spectrometer only • Calculate –related quantities averaged over the various targets • Obtain ratio of charmonia • production to Drell-Yan • (à la NA50) • Kinematic region • 0 < yCM <1 • -0.5 < cos CS < 0.5 • Acceptances • J/ : 0.156 • ’ : 0.173 • DY (2.9<m<4.5) : 0.150

  17. (J/)/DY = 29.2  2.3 L = 3.4 fm Preliminary! (J/)/DY at 158 GeV Rescaled to 158 GeV • Preliminary NA60 result shows that the rescaling of the J/ • production cross section from 450(400) GeV to 158 GeV is correct !

  18. Preliminary! ’ / DY 450, 400 and 200 GeV points rescaled to 158 GeV ’/DY = 0.51  0.07 L = 3.4 fm Also the ’ value measured by NA60 at 158 GeV is in good agreement with the normal absorption pattern, calculated from 450 (400) GeV data

  19. Transverse momentum distributions Kinematical region 0.1 < yCM < 0.9 -0.4 < cosH < 0.4 Transverse momentum distributions fitted with • Study evolution of • T and pT2 with • centrality

  20. pT2 vs centrality • If pT broadening is due to gluon scattering in the initial state •  pT2 = pT2pp + gN · L • NA60 In-In points are in fair • agreement with Pb-Pb results • We get gNInIn = 0.067  0.011 (GeV/c)2/fm pT2ppInIn = 1.15  0.07 (GeV/c)2 2/ndf = 0.62 to be compared with gNPbPb = 0.073  0.005 (GeV/c)2/fm pT2ppPbPb = 1.19  0.04 (GeV/c)2 2/ndf = 1.22 (NA50 2000 event sample)

  21. T vs centrality Fitting functions • Used by NA50 • Gives slightly • higher T values (~ 7 MeV) 1) dN/dpT = pT mT K1(mT/T) 2) dN/dpT = pT e -mT/T

  22. J/ polarization • Quarkonium polarization test of production models • CSM: transverse polarization • CEM: no polarization • NRQCD: transverse polarization at high pT • Deconfinement should lead to a higher degree of polarization • (Ioffe,Kharzeev PRC 68(2003) 094013) 0.5 < pT < 5 GeV 0.1 < yCM < 0.6 0 < pT < 5 GeV 0.4 < yCM < 0.75 H = 0.03  0.06 CS = -0.03  0.17 2/ndf =1.42 2/ndf =1.01

  23. 0.5<pT<5 0.1<yCM<0.6 0.1<yCM<0.8 0.2<pT<5 • Helicity reference system (good coverage in NA60, -0.8<cosH<0.8) • No significant polarization effects as a function of • Centrality • Kinematical region • Similar results in the Collins-Soper reference frame, • albeit with much narrower coverage (-0.4<cosCS<0.4) Polarization vs pT, y, centrality

  24. 0<pT<5, -0.4 < cosH < 0.4 y = 0.68 0.02 2/ndf = 0.60 J/ rapidity distributions • Data are consistent with a gaussian • rapidity distribution • Centrality independent • Slightly narrower at high pT ?

  25. Azimuthal distribution of the J/ central peripheral More peripheral data  hint for a non isotropic emission pattern? Only 50% of the statistics analyzed

  26. Conclusions and perspectives • NA60 has performed a high-quality study of J/ production • in Indium-Indium collisions at the SPS • Confirms, for a much lighter system, the anomalous suppression • seen in Pb-Pb collisions by NA50 • Onset of anomalous suppression at Bj~ 1.5 GeV/fm3 • Preliminary results from p-A collisions at 158 GeV show that • the normalization of the absorption curve is correct • Peripheral In-In and Pb-Pb results are compatible with p-A • Absence of J/ polarization in the kinematical window probed by NA60 • pT distributions sensitive to initial state effects • Study of J/ suppression for other collision systems, with the accuracy • allowed by a vertex spectrometer, would be very interesting

  27. CERN Heidelberg Bern Palaiseau BNL Riken Yerevan Stony Brook Torino Lisbon Cagliari Clermont Lyon The NA60 collaboration http://cern.ch/na60 ~ 60 people 13 institutes8 countries R. Arnaldi, R. Averbeck, K. Banicz, K. Borer, J. Buytaert, J. Castor, B. Chaurand, W. Chen, B. Cheynis, C. Cicalò, A. Colla, P. Cortese, S. Damjanović, A. David, A. de Falco, N. de Marco, A. Devaux, A. Drees, L. Ducroux, H. En’yo, A. Ferretti, M. Floris, P. Force, A.A. Grigoryan, J.Y. Grossiord, N. Guettet, A. Guichard, H. Gulkanyan, J. Heuser, M. Keil, L. Kluberg, Z. Li, C. Lourenço, J. Lozano, F. Manso, P. Martins, A. Masoni, A. Neves, H. Ohnishi, C. Oppedisano, P. Parracho, P. Pillot, T. Poghosyan, G. Puddu, E. Radermacher, P. Ramalhete, P. Rosinsky, E. Scomparin, J. Seixas, S. Serci, R. Shahoyan,P. Sonderegger, H.J. Specht, R. Tieulent, E. Tveiten, G. Usai, H. Vardanyan, R. Veenhof and H. Wöhri

More Related