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Measurement of Quarkonium Production at CMS

Measurement of Quarkonium Production at CMS. ÖPG Tagung 2010. Overview. Introduction Quarkonium Production Models Quarkonium Production Measurements at CMS Event Selection and Muon Reconstruction Preliminary Results. Introduction. Quarkonium Production Mechanisms still “unknown”

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Measurement of Quarkonium Production at CMS

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  1. Measurement of Quarkonium Production at CMS Valentin Knünz (HEPHY Vienna) ÖPG Tagung 2010

  2. Overview Introduction Quarkonium Production Models Quarkonium Production Measurements at CMS Event Selection and Muon Reconstruction Preliminary Results Valentin Knünz (HEPHY Vienna)

  3. Introduction • Quarkonium Production Mechanisms still “unknown” • LHC is a ”Quarkonium factory” • Key information for the understanding of Hadron Production. p+ p+ c c b b J/ψ Y JPC = 1- - 3.097 GeV 9.460 GeV Valentin Knünz (HEPHY Vienna)

  4. Quarkonium Production Models Quarkonium Production can be factorized in two parts: Production of quark and antiquark pair (perturbative QCD) Formation of the bound Quarkonium state (non-perturbative QCD) Question: Correlation of quantum numbers of initial and final state? • The Nonrelativistic QCD Model (NRQCD) • Treats quarkonium as an approximately nonrelativistic system. (->Y measurement more significant) • Implies that set of quantum number can change by emitting low energy gluons (->COM) • The Color Singlet Model (CSM) • Initial quark-antiquark state and final quarkonium state are the same, necessarily a colour singlet. • NLO, NNLO Valentin Knünz (HEPHY Vienna)

  5. Quarkonium Production Models Experimental Test of Quarkonium Production Models at Tevatron • Diff. cross section of direct J/ψ – NRQCD • Diff. cross section of prompt Y(1S) – NNLO CSM • Polarization of direct J/ψ – both models fail J/ψ Valentin Knünz (HEPHY Vienna)

  6. Quarkonium Production Measurements at CMS Differential production cross section and Polarization Measurements • Promptly produced J/ψ’s: Directly produced J/ψ’s + feed down from heavier charmonium states Charmonium Spectrum Valentin Knünz (HEPHY Vienna)

  7. Quarkonium Production Measurements at CMS Differential production cross section and Polarization Measurements • Non Prompt J/ψ’s: J/ψ’s that come from decays of B-Hadrons Decays of B-Hadrons (most importantly feed down from B0, B+, Bs and λb) additionally complicate the charmonium production measurements –> B-fraction is determined through studies of a displaced vertex, LB = O(100μm) Valentin Knünz (HEPHY Vienna)

  8. Quarkonium Production Measurements at CMS Differential production cross section and Polarization Measurements 3. Promptly produced ϒ(1S)’s: Direct ϒ(1S)’s+ feed down from heavier bottomonium states Bottomonium Spectrum Valentin Knünz (HEPHY Vienna)

  9. Event Selection and Muon Reconstruction Decay Channels CMS is ideally suited to study quarkonium production in the dimuon decay channels: J/ψ -> μ+ μ- , Branching ratio ≈ 6% ϒ(1S) -> μ+ μ- , Branching ratio ≈ 2.5% Muon Definition Muons are defined as tracks reconstructed in the silicon tracker which are associated to a compatible signal in the muon chambers • Two Muon „Qualities“: • Global muons are built as combined fit of tracker and muon-chamber hits (in muon system at least 2 stations must be hit) • Tracker muons requirements are looser than for Global muons at the expense of a slightly larger background • Selection Constraints: • Number of Track hits > 12 (hits in pixel layer > 2) • Χ2/ndf < 4; • Tracks must pass through a cylinder (r=3cm, l=30cm) around the primary vertex Valentin Knünz (HEPHY Vienna)

  10. Event Selection and Muon Reconstruction Quarkonium Event Selection • Pairing muons (GG,GT,TT) • Rejection of same-sign events • Computing of invariant dimuon mass • Definition of mass windows GG+GT+TT GG Valentin Knünz (HEPHY Vienna)

  11. Preliminary Results • ICHEP (Paris) Preliminary results • Diff. cross section of prompt J/ψ • Fraction of J/ψ‘s from B Hadrons • Dimuon mass spectrum Valentin Knünz (HEPHY Vienna)

  12. Summary and Outlook • Quarkonium cross section and polarization measurements crucial to understand hadron production • Contradictory experimental polarization measurement results in the past • CMS is ideally suited to measure quarkonium production • Y(1S) analysis will need to wait till CMS gains more statistics • For J/ψ measurements statistics needed to get significant results almost reached Valentin Knünz (HEPHY Vienna)

  13. Valentin Knünz (HEPHY Vienna)

  14. BACKUP SLIDES Y(1S), Y(2S) and Y(3S) invariant dimuon mass distributions Rapidity of Y(x) < 2 Rapidity of muons < 1 |y| < 2 Valentin Knünz (HEPHY Vienna)

  15. BACKUP SLIDES • Comparison of Tevatron Experimental Results: • D0 II • CDF Run I • CDF Run II J/ψ Valentin Knünz (HEPHY Vienna)

  16. BACKUP SLIDES MC lifetime distributions for prompt and non prompt J/ψ‘s Valentin Knünz (HEPHY Vienna)

  17. References • CMS PAS BPH-10-002, „J/ψ prompt and non-prompt cross sections in pp collisions at √s = 7 TeV“ • CMS AN AN-10-138, „Inclusive total and differential production cross section of J/ψ and b-hadron production in pp collisions at √s = 7 TeV with the CMS experiment“ • ICHEP Valentin Knünz (HEPHY Vienna)

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