1 / 18

Prospects for quarkonium studies at LHCb

Patrick Robbe, LAL Orsay, 19 Feb 2010. Prospects for quarkonium studies at LHCb. « Quarkonium Production at the LHC » workshop. LHCb Detector. Forward Spectrometer Geometry, with angular acceptance 15< q <300 mrad Performance numbers relevant to quarkonium analyses:

peigi
Download Presentation

Prospects for quarkonium studies at LHCb

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. Patrick Robbe, LAL Orsay, 19 Feb 2010 Prospects for quarkonium studies at LHCb « Quarkonium Production at the LHC » workshop

  2. LHCb Detector • Forward Spectrometer Geometry, with angular acceptance 15<q<300 mrad • Performance numbers relevant to quarkonium analyses: • Charged tracksDp/p = 0.35 % - 0.55%, s(m)=12-25 MeV/c2 • ECALs(E)/E= 10% E-1/2 1 % (E in GeV) • muon ID: e(mm) = 94 %, mis-ID rate (pm) = 3 % • Vertexing: s(L)=250 mm (Primary Vertex Resolution: 10mm in x/y, 60 mm in z)

  3. Introduction • Unique acceptance between LHC experiments: • Quarkonium Physics Program: • Measurement of J/y production cross-section in LHCb acceptance (3<h<5, pT<7 GeV/c), • Measurement of J/y polarization • Similar measurements with y(2S), Y(1S), Y(2S), Y(3S). • Production of cc, hc • Extensive studies of Bc, X(3872)

  4. Monte Carlo Tools • PYTHIA 6.3 for the studies shown here: • Production of J/y through Color Single Model. • PYTHIA 6.4 for the current Monte Carlo productions: • With Color Octet Model added, tuned to reproduce CDF measurements see note CERN-LHCb-2007-042. • EvtGen for decays: • Generator package which allows to have a detailed description of b J/y X decays. • Also allows correct angular correlations in decays of polarized particles. • PHOTOS for radiative corrections.

  5. Monte Carlo J/y Samples LHCb MC (14 TeV, Pythia 6.3) 3<h<5 • In LHCb acceptance (3<h<5, pT<7 GeV/c): • s(pp  prompt J/y X) x Br(J/y m+ m-) = 2.7 mb • s(pp  (b  J/y X) X') x Br(J/y m+ m-) = 0.15 mb NB: the analysis presented here does not depend on the exact spectrum of the J/y.

  6. J/y  m+ m- Reconstruction • Selection based on positive muon identification of the two m, cut on the m transverse momentum pT>0.7 GeV/c and on the quality of the m+m- vertex. • Invariant mass plot on fully simulated minimum bias events (with all background included): • Mass resolution: 11.0 ± 0.4 MeV/c2, • S/B=17.6 ± 2.3 in ±3s mass window, • 1.3x109 reconstructed after L0 trigger J/y for 1 fb-1 ( =14 TeV) • Or 0.65x106 for 1 pb-1at = 7 TeV LHCb Minimum Bias Monte Carlo (14 TeV)

  7. Separating prompt J/y from J/y from b • Use pseudo-propertime: • Prompt component characterized by peak at 0, • Exponential decay for J/y from b component, • Long tail due to association of the J/y to a not-related primary vertex. LHCb Inclusive J/y Monte Carlo (14 TeV) • Combined mass/pseudo-propertime fit will allow to measure both prompt and J/y from b production cross sections in h and pT bins: • 4 pseudo-rapidity h bins, 3 < h < 5. • 7 transverse momentum bins pT, pT<7 GeV/c.

  8. Example: fit on MC at = 14 TeV • Sample corresponding to 0.8 pb-1, = 14 TeV • Signal: Inclusive J/y sample • Background: toy Monte-Carlo reproducing behaviour (mass and pseudo-lifetime) seen on the Minimum Bias sample. LHCb Inclusive J/y Monte Carlo + Toy MC (14 TeV) • Results (J/y with 3<h<5 and pT<7 GeV/c): • s(prompt J/y) x Br(J/y → m+m-) = 2597  12 (stat)  24 (eff) nb [Input: 2667 nb] • s(J/y from b) x Br(J/y → m+m-) = 161  4 (stat)  2 (eff) nb [Input: 153 nb] Statistical error at maximum 10% in each of the analysis bin, for 5pb-1 of data at = 7 TeV.

  9. Systematics from J/y polarization • Acceptance as a function of cosq, q = helicity angle • Large LHCb detector acceptance dependance on assumed initial polarization of J/y.

  10. Systematics from J/y polarization • Study the effect of ignoring the polarization dependance of the efficiency (J/y are not polarized in the LHCb Monte Carlo) a«data» Measured cross-section, assuming a=0 Input s«data» 0 2758 nb ± 27 nb 2820 nb +1 2738 nb ± 27 nb 3190 nb -1 2787 nb ± 28 nb 2286 nb • Systematic error up to 25 % when ignoring polarization. • Polarization will be measured (in a second step): • in bins of h and pT, • separating prompt and J/y from b, • With full angular analysis, in different reference frames.

  11. y(2S) m+m- • Similar performances than J/y: • Mass resolution: 13 MeV/c2 • S/B = 2 • Number of reconstructed y(2S) = 2-4 % of the number of reconstructed J/y. • Measurement of the ratio s(y(2S))/s(J/y), as a function of pT, separating prompt and from b. • Polarization effects complicate also the measurement: systematic error up to 22% on the cross section ratio.

  12. Y(1S) → m+m- • Loose muon ID selection, and transverse momentum requirement (pT(m)>1.5 GeV/c). • L0 trigger efficiency: 96 % • Mass resolution: 37 MeV/c2 • Similar reconstruction and resolutions will be obtained for the Y(2S) and Y(3S) states: this will allow to separate the 2 Upsilon states. • Goal is to measure cross-sections and polarization for all di-muon states, as a function of pT. LHCb Inclusive Y Monte Carlo (14 TeV)

  13. cc reconstruction • J/y selection, adding a photon detected in the ECAL with pT(g)>500 MeV/c. • Dm=m(J/y g)-m(J/y) distribution obtained on fully simulated events containing on J/y. Since the J/y background is very low, the plot contains a large fraction of the total background. • Dm resolution = 27 MeV/c2. LHCb Inclusive J/y Monte Carlo (14 TeV) cc2 cc1

  14. cb2 reconstruction • Reconstruction of cb2(1P) → Y(1S) g • Photon detected in ECAL, with pT(g) > 500 MeV/c • Mass resolution: 47 MeV/c2 LHCb Inclusive Y Monte Carlo (14 TeV)

  15. hc reconstruction • Besides di-muon states, LHCb detector performances will allow to study other states though hadronic decay modes. • Reconstruction of hc → hcg is difficult (E(g)~500 MeV in the hc rest frame). • Hadronic decay channels look promising: hc → pp, hc → f K+ K-, hc → fp+p-. • In particular, hc → pp probably visible with first year data, which will give access to s(hc)xBr(hc → pp) relative to s(J/y)xB(J/y → pp). LHCb Signal Monte Carlo + Toy MC (10 TeV) • Expected pp mass distribution: • Assuming Br(hc → pp) = 0.12 %, • Toy Monte Carlo for background, reproducing background seen on fully simulated minimum bias events, • 100 pb-1 at = 10 TeV J/y cc0 hc cc1 cc2 m(pp) (GeV/c2)

  16. X(3872) and Z(4430) • Reconstruction of X(3872) → J/yp+p- (and the control channel y(2S) → J/yp+p-), prompt or from b: systematic study of this state. • Expect 1800 reconstructed B → X(3872) K, with 2 fb-1 at = 14 TeV, allowing to disentangle unknown quantum number JPC: 1++/2-+. • Reconstruction of X(3872) → J/yp+p- (and the control channel y(2S) → J/yp+p-), prompt or from b: systematic study of this state. • Expect 1800 reconstructed B → X(3872) K, with 2 fb-1 at = 14 TeV, allowing to disentangle unknown quantum number JPC: 1++/2-+. LHCb Generator Only signal 1++/2-+ • Similar studies for B0 →Z(4430)+( →y(2S)p+)K- • About 6200signal events can be selected from 2 fb-1of data at =14 TeV, assuming B(B0 →Z(4430)+K-)xB(Z(4430)+→y(2S)p+) = 4.1x10-5 • Possible to confirm the Belle discovery with about 100 pb-1of data at = 7 TeV.

  17. Bc • Measurement of mass, lifetime and production cross section using the decay modes: • Bc+ → J/yp+ assuming s(Bc+)=0.4 mb, and Br(Bc+ → J/yp+) =0.13 %, expect 310 signal events for 1 fb-1 of data at = 14 TeV. • Production cross section relative to B+(→ J/y K+) • Bc+ → J/ym+ X: signal yield one order of magnitude larger, production cross section measurement possible with 2010 data. 1 fb-1, 14 TeV

  18. Conclusions • LHCb will measure production cross sections and polarization of di-muon states, in the LHCb acceptance: 3 < h < 5, pT<7 GeV/c. • Other quarkonium states will also be looked at: hc, cc, cb, Bc. • LHCb performances will allow to also study associate productions: J/y+J/y, J/y+cc, either reconstructing D or tagging it with a displaced e or m. • Study of « exotic » states: X(3872) and Z(4430). • Similar states can also be searched in (Quarkonium p+p-) mass spectra: Yb → Y(1S) p+p-, Bc** → Bc+p+ p-.

More Related