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Extrapolation of J/ y cross sections from p-p 7 TeV to p-p 2.75 TeV in LO CEM

Extrapolation of J/ y cross sections from p-p 7 TeV to p-p 2.75 TeV in LO CEM. F. Bossù, M . Gagliardi INFN & Università degli Studi Torino. Outline. Color Evaporation Model d s /dy for J/ y in pp at 7 and 2.75 TeV

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Extrapolation of J/ y cross sections from p-p 7 TeV to p-p 2.75 TeV in LO CEM

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  1. Extrapolation of J/y cross sections from p-p 7 TeV to p-p 2.75 TeVin LO CEM F. Bossù, M. GagliardiINFN & Università degli Studi Torino

  2. Outline • Color Evaporation Model • ds/dy for J/y in pp at 7 and 2.75 TeV • Rescaling factors for total and y-differential cross sections: PDF andmFdependence , evaluation of systematics • Comparison with LO CSM • Conclusions and outlook • Perspectives for a pp run at 2.75 TeV

  3. At the LHC startup: Pb-Pb: = 2.75 TeV Task: evaluate s (pp -> X) at = 2.75 TeV p-p: = 7 TeV RAA meaningful if: Motivation One of the main observables for quarkonia suppression studies: the nuclear modification factor RAA X = J/y, ...c = a centrality-related quantity MEASUREMENT? EXTRAPOLATION?

  4. Leading Order Color Evaporation Model Cross section for prompt quarkonia production: some fraction F of the QQ cross section below the open heavy flavour meson threshold.Findependent of kinematics, process, . CS not explicitely required LO formulae for the rapidity distributions can be used to estimate uncertainty related to the choice of PDF set and ofmF. Dominant diagram gg->QQ only. Assuming no mR dependence of ratios of cross sections at LO

  5. Gluon distribution functions hep-ph/0201195 hep-ph/9803445 hep-ph/9903282 hep-ph/0201127 Leading Order fit for mF = 2mc

  6. Prompt J/y rapidity distributions in LO CEM mF = 2mc

  7. J/y rapidity distributions in LO CEM (2) Caveat 1: data include J/y from B-decay, curves don’t Caveat 2: curves are normalised to same integral in 2.5 < y < 4 (= measured s) Data do not seem to prefer nor discard any of these curves

  8. Rescaling factors for cross sections in ALICE acceptance Central Barrel Muon Spectrometer mF = 2mc

  9. mF dependence: cross sections ALICEMuon spectrometer ALICECentral barrel

  10. mF dependence: rescaling factors ALICECentral barrel ALICEMuon spectrometer Variation in 2mC < mF < 2mD: 4% to 10% (depending on PDF)

  11. Comparison with CSM J. P. Lansberg arXiv:1006.2750v1 [hep-ph] LO CSM with CTEQ6L PDF: 1.87 < SCB < 2.07 and 2.31 < SMS < 2.52 LO CEM with CTEQ6L PDF and mF = 2mC SCB = 1.69 and SMS = 1.96

  12. Rescaling factors for y-differential cross section ALICECentral barrel ALICEMuon spectrometer

  13. Conclusions • Rescaling factors from 7 to 2.75 TeV evaluated in LO Color Evaporation Model for total and y-diffferential cross sections, with 5 different PDFs • Variation of rescaling factors with PDF:24% in ALICE central barrel acceptance18% in ALICE muon spectrometer aceptance • Variation related to factorisation scale mF: 4%÷10% (depending on PDF) for 2mC < mF < 2mD • CSM (lower bound) vs CEM: 10% for central barrel, 16% for muon spectrometer NB: Variation = Full spread / median

  14. Outlook and hints for discussion • Take into account J/y from B-decay • NLO CEM • Newer PDFs (can we discard some of those used here?) • Explore more models (CSM, NRQCD..) • Should we expect theory to reduce systematics with combined use of LHC@7 TeV and Tevatron data?

  15. A pp run at 2.75 TeV? LHCC102 minutes (shown at LPC meeting 27/09/2010) in part (~50%) May be scheduled in 2011 http://indico.cern.ch/conferenceDisplay.py?confId=108493 One colliding bunch in IP2 LHC Programme coordinator says:

  16. A pp run at 2.75 TeV? (2) Maximum luminosity (no beam displacement) with nominal emittances, 1 colliding bunch, 7x1010 p and b* = 3.5 m : ~ 0.2 Hz/mb (vdM scan) Thus, in 20 h withb* = 10 m we should expect (at most): 20 h * 3600 s/h * (3.5/10) * 0.2 Hz / mb = 5600 mb-1 Using measured cross sections at 7 TeV and a rescaling factor to 2.75 TeV of 0.5, we get:~ 2400 J/y in e+e- in -0.9 < y < 0.9~ 1200 J/y in m+m- in 2.5 < y < 4Can we do something with this?Next slides: verypreliminary feasibility study in the muon spectrometer (signal analysis only!)

  17. Perspectives for a pp run at 2.75 TeV Generate 1200 J/y with “realistic ”input distributions at 2.75 TeV: Rescaled from CDF fit according to CEM evolution Obtained as:

  18. Perspectives for a pp run at 2.75 TeV After reconstruction: about 500 detected J/y Can we appreciate the J/y signal in such a low statistics scenario? Full physics performance coming soon

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