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 and Drell-Yan production in p-A collisions at 450 GeV incident energy

 and Drell-Yan production in p-A collisions at 450 GeV incident energy. P. Cortese for the NA50 Collaboration:

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 and Drell-Yan production in p-A collisions at 450 GeV incident energy

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  1.  and Drell-Yan production in p-A collisionsat 450 GeV incident energy P. Cortese for the NA50 Collaboration: B. Alessandro, C. Alexa, R. Arnaldi, M. Atayan, S. Beolè, V. Boldea, P. Bordalo, G. Borges, C. Castanier, J. Castor, B. Chaurand, B. Cheynis,E. Chiavassa, C. Cicalò, M.P. Comets, S. Constantinescu, P. Cortese, A. De Falco, N. De Marco, G. Dellacasa, A. Devaux, S. Dita,J. Fargeix, P. Force, M. Gallio, C. Gerschel, P. Giubellino, M.B. Golubeva, A.A. Grigorian, S. Grigorian, J.Y. Grossiord, F.F. Guber, A. Guichard,H. Gulkanyan, M. Idzik, D. Jouan, T.L. Karavitcheva, L. Kluberg, A.B. Kurepin, Y. Le Bornec, C. Lourenço, M. Mac Cormick, A. Marzari-Chiesa,M. Masera, A. Masoni, M. Monteno, A. Musso, P. Petiau, A. Piccotti, J.R. Pizzi, F. Prino, G. Puddu, C. Quintans, L. Ramello, S. Ramos,L. Riccati, H. Santos, P. Saturnini, E. Scomparin, S. Serci, R. Shahoyan, F. Sigaudo, M. Sitta, P. Sonderegger, X. Tarrago, N.S. Topilskaya,G.L. Usai, E. Vercellin, L. Villatte, N. Willis, T. Wu - Università del Piemonte Orientale/INFN, Alessandria, Italy - LAPP, CNRS-IN2P3, Annecy-le-Vieux, France - LPC, Univ. Blaise Pascal and CNRS-IN2P3, Aubière, France - IFA, Bucharest, Romania - Università di Cagliari/INFN, Cagliari, Italy - CERN, Geneva, Switzerland - LIP, Lisbon, Portugal - INR, Moscow, Russia, IPN - Univ. de Paris-Sud and CNRS-IN2P3, Orsay, France - LLR, Ecole Polytechnique and CNRS-IN2P3, Palaiseau, France - Università di Torino/INFN, Torino, Italy - IPN, Univ. Claude Bernard Lyon-I and CNRS-IN2P3, Villeurbanne, France - YerPhI, Yerevan, Armenia

  2. Physics motivation Study of heavy flavours and quarkonia production in p-A • Test of theory of strong interactions • probe the production aspects that are calculable in pQCD: the dependence of the cross section on energy, pT, xF, CS polarization • constrain theoretical approaches: NRQCD and CEM • parametrize non perturbative aspects: color neutralization of the c-cbar, b-bbar pairs andabsorption in nuclear matter • Essential reference for the study of quarkonia suppression in hot and dense matter • At SPS: J/ysuppression in Pb-Pb, In-In • p-A collisions to measure “normal” nuclearabsorption • At RHIC: J/yproduction in Au-Au,Cu-Cu • p-p and d-Au collisions as a reference • At LHC:y and  production from p-p to Pb-Pb  absorption in normal nuclear matter not systematically studied up to now even at fixed target energies  new data are useful in view of future collider experiments

  3. Experimental overview of  production in pp and pA

  4. p-A data taking at the NA50 dimuon spectrometer • 5 nuclear targets: Be, Al, Cu, Ag, W • L ~ 10 pb-1 per target • 2 data sets at 450 GeV: high luminosity and low luminosity • ~ 400  in the +- channel in total • Rapidity coverage: -0.5 < ycm < 0.5 • For the  corresponds to: -0.36 < xF < 0.36 • Collins-Soper: -0.5 < cos(CS) < 0.5 • pT ~ flat coverage Transverse polarization for ’ and ’’ is assumed in this analysis Typical acceptances: AJ/y 14% ADY ~ 21% (mmm > 6 GeV) A ~ 25%

  5. The opposite sign dimuon invariant mass spectra Drell-Yan Upsilons • Mass resolution ~ 4% at 10 GeV • Combinatorial background and other contributions are negligible in this mass range

  6. Extracting the  and DY signals Fit to the opposite sign dimuon invariant mass spectrum with a superposition of  and Drell-Yan signals • Line shapes from MC simulation • nDY and n free parameters in the fit • Relative weight of  states fixed from CFS experiment at 400 GeV • Good fit quality: • 2/dof = [0.91.5]

  7. Nuclear dependence of Drell-Yan production Drell-Yan cross section per nucleon-nucleon collision for M > 6 GeV Fit (Drell-Yan) with a power law  = 0 · A Drell-Yan = 0.98  0.02 2/dof = 1.4 By imposing   1 we get 2/dof = 1.3 Drell-Yan scales with nucleon-nucleon collisions  useful to normalize  yield

  8. Nuclear dependence of  production a= 0.98  0.08 (c2/dof = 0.8) a/DY = 0.98  0.09 (c2/dof = 0.9) By imposing   1 we get 2/dof = 0.8 Weak nuclear absorption for the  at mid-rapidity

  9.  nuclear absorption: comparison of  with E772 Qualitative agreement with measurement by E772 at 800 GeV NA50 measurement at 450 GeV suggests low absorption around xF = 0

  10. Study of pT and ycm dependence of  and DY production Too small statistics to divide the data sample into pT or ycm bins Strategy: 1. Comparison of experimental spectra withvarious simulated distributions obtained with different MC parameters Iterative procedure until we get self consistency in the results 2. Build an estimator of the agreement between data and Monte-Carlo taking into accountthat data and MC have finite statistics (S. Baker and R. Cousins Nucl. Instr. Meth. A221 (1984) 437) 2 3. Find the value of the parameter that minimizes 2 and get the corresponding error 4. Use the parameter obtained with this minimization to get new line-shapes to be used in the fits

  11. Drell-Yan transverse momentum Path in nuclear matter of the projectile parton

  12.  transverse momentum Statistics is too low to observe a clear nuclear dependence Making an average on the 5 data samples we get:

  13. Mean pT for DY and: comparison with other experiments

  14. Rapidity / xF distribution Results from previous experiments NA50

  15. B d() / dycm at ycm = 0 Very good agreement with existing systematics

  16. Summary • First measurement of  production in p-A collisions at 450 GeV •  cross section at mid-rapidity is compatible with CEM calculations and with the available systematics • We observed a small nuclear absorption for the  at mid rapidity. a = 0.98  0.08 • The  rapidity distribution is compatible with measurements at 400 GeV • Drell-Yan production cross section for 4.5 < M < 8.0 GeV scales with nucleon-nucleon collisions confirming observations by NA38/50/51 the invariant mass range 2.9 < M < 7.0 GeV

  17. References [Herb77] S. W. Herb et al., Pyhs. Rev. Lett. 39, 252 1977. [Yoh78] J. K. Yoh et al., Pyhs. Rev. Lett. 41, 684 1978. [Ueno79] K. Ueno et al., Phys. Rev. Lett. 42, 486 (1979). [Badier79] J. Badier et al., Phys. Lett. B86, 98 (1979). [Angelis79] A.L.S. Angelis et al., CCOR Collaboration, Phys. Lett. B87 (1979) 398. [Kourkoumelis80] C. Kourkoumelis et al., Phys. Lett. B91 (1980) 481. [Antreasyan80] D. Antreasyan et al., Phys. Rev. Lett. 45 (1980) 863. [Antreasyan81] D. Antreasyan et al., Phys. Rev. Lett. 47 (1981) 12. [Childress85] S. Childress et al., Phys. Rev. Lett. 55, 1962 (1985). [Albajar87] C. Albajar et al., Phys. Lett. B186, 237 (1987). [Yoshida89] T. Yoshida et al., Phys. Rev. D 39, 3516 (1989). [Moreno91] G. Moreno et al., Phys. Rev. D 43, 2815 (1991). [Alde91] D. M. Alde et al., Phys. Rev. Lett. 66, 2285 (1991). [Alexopoulos96] T. Alexopoulos et al., Phys. Lett. B374 (1996) 271. [Brown01] C. N. Brown et al., Pys. Rev. Lett. 86, 2529 (2001). [Acosta02] D. Acosta et al., Pys. Rev. Lett. 88, 161802 (2002). [Nedden04] M. Nedden et al., HERA-B Collaboration, hep-ex/0406042.

  18. Experimental overview:  production in pp and pA

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