Quarkonium Studies @ LHCb Giacomo Graziani (INFN Firenze) on behalf of the LHCb Collaboration December 5th, 2008 QWG08, Nara G. Graziani slide 1 QWG08
The LHCb Experiment dedicated to CP violation and rare decays in b sector at the LHC, where σ(bb) 500µb bb mostly forward = single armed spectrometer with fixed target like geometry L = 2 10 32 cm 2 s 1 = interactions per event < n NP >= 0.5 = 2 fb 1 /year or 4 10 11 bb/year! but high background and track multiplicity σ(bb)/σ tot 6 10 3 = emphasis on VERTEX/TRACKING and PID G. Graziani slide 2 QWG08
LHCb Detector G. Graziani slide 3 QWG08
LHCb Detector: Tracking G. Graziani slide 4 QWG08
Tracking Performances Impact Parameter Resolution Momentum Resolution average 0.4 % = Proper Time Resolution for fully reconstructed B decays typical 40 fs Tracking Efficiency 94 % for p > 10 GeV/c G. Graziani slide 5 QWG08
LHCb Detector: Particle Identification G. Graziani slide 6 QWG08
PID Performances Kaon identification average 97% with 5 % π K misid Muon identification average 93 % with 1 % π µ misid π 0 identification 50% G. Graziani slide 7 QWG08
Status Detectors installed and commissioned for the 2008 run... G. Graziani slide 8 QWG08
First Beam splash First LHC particles recorded during synchronization tests on Aug 24th and Sep 10th (shots from beam dumps with 1 particle/cm 2 ) G. Graziani slide 9 QWG08
... G. Graziani slide 10 QWG08
Cosmics cosmic muons (up to 10 6 tracks in ECAL/MUON acceptance) used for commissioning and first alignments G. Graziani slide 11 QWG08
The Trigger Output Streams: exclusive B channels ( 200 Hz) = core physics program } inclusive B ( 900 Hz) confirm muon candidate relevant for with high IP or p T quarkonium physics inclusive charm ( 300 Hz) reconstructed D (prompt J/ψ, D, di muons ( 600 Hz) high p T muons) First Physics at low luminosity: can acquire Minimum Bias events for L 4 10 28 cm 2 s 1 (rate of visible interactions < 2 khz) G. Graziani slide 12 QWG08
Expected contributions to Quarkonium Physics prompt/direct production of charmonium and bottomonium states at the LHC energy in unique range of pseudorapidity p T spectra from 1 2 GeV polarization B c studies production cross section mass and lifetime start B c spectroscopy exploring new X, Y, Z states... G. Graziani slide 13 QWG08
Simulation of quarkonium production in LHCb LHCb plans to use Pythia 6.4, using NRQCD with Color Octet Model Simultaneous tuning of CSM, COM contributions and p T cutoff to CDF data. (Presented at QWG06, documented in public LHCb note LHCb-2007-042 ) Expect J/ψ σ prod 300 µb @ s =14 TeV Predicted effective prompt J/ψ cross section for LHCb σ(pp J/ψ µ + µ ) Acc. = (3±1)µb G. Graziani slide 14 QWG08
J/ψ Production First estimation of J/ψ Trigger/Rec./Sel. efficiency ɛ 30% = expected yield = σ(j/ψ µ + µ ) Acc. ɛ L 10 6 L(pb 1 ) i.e. 2 10 9 J/ψ per nominal year J/ψ signal could be observed from day 1 using Minimum Bias events: assume L = 10 28 cm 2 s 1 = expected rate of visible interactions 0.8 khz (can be acquired without selection) = get first sample of 100 J/ψ in 4 5 h mass resolution is 12 MeV B/S=0.17 on Min. Bias events J/ψ signature essential for detector calibrations and background studies G. Graziani slide 15 QWG08
Disentangling Different J/ψ Sources prompt J/ψ can be disentangled from B J/ψ decays using excellent proper time resolution. Fit pseudo proper time t = z M J/ψ /p z to extract fraction from B decays We expect σ eff σ eff B J/ψ prompt 3 µb 200 nb χ c production can be measured from the J/ψ γ invariant mass distribution. J/ψ γ inv. mass from 10 5 inclusive J/ψ plot uses old MC with overestimated χ c production, but a clean signal can be extracted. Mass resolution is 30 MeV (not enough to resolve fine splittings) G. Graziani slide 16 QWG08
J/ψ Polarization LHCb acceptance strongly depends on cosθ dσ d cos θ 1 + αcos2 θ = σ and α to be fitted simultaneously from J/ψ mass and pseudo proper time in bins of η and p T Exercise: measure α from 30 nb 1 of inclusive J/ψ (simulated α = 0, statistical errors only) G. Graziani slide 17 QWG08
B c production LHCb in ideal position to study B c mesons: acceptance for high rapidity proper time resolution expected σ(b c ) 0.4 µb (20 Tevatron) cleanest channel is J/ψ (µ + µ )π, though BR is expected to be low (0.13%) selection based on p T and IP of B c π, J/ψ, and χ 2 vtx total efficiency (including acceptance) 1 % assuming σ prod (B c ) 0.4 µb we expect a yield of 300 events L(fb 1 ) with B/S 1 2 G. Graziani slide 18 QWG08
B c mass resolution: 25 MeV (18 MeV with J/ψ mass constraint) proper time resolution: 25 fs Preliminary estimates for mass and lifetime measurement accuracy (stat. error only): σ(m Bc ) = 1.4 MeV L(fb 1 ) σ(τ Bc ) = 29 fs L(fb 1 ) G. Graziani slide 19 QWG08
Other quarkonium studies B c production and lifetime through B c J/ψ µν (BR 1.9%, expect 8k events/fb 1 with B/S 35 from lifetime unbiased selection) search for B c (1P) and higher excited states from radiative decays to B c (1S) bottomonium and ψ(2s) production, polarization J/ψ + cc production search and study properties of the new X, Y, Z quarkonia states triggered by high mass dimuons: LHCb can collect large samples of X(3872) J/ψ π + π decays, both prompt and from b (e.g. B + X(3872)K + ) bottomonium states decaying to Υ (1S) ( µ + µ ) exclusive channels such as B Z + (4430)K G. Graziani slide 20 QWG08
Conclusions LHCb is ready for its first physics run the first minimum bias events will allow for first production studies at LHC energy in unique rapidity range: clean J/ψ sample from day 1 (0.1 nb 1 ) J/ψ from B from 1 nb 1 other quarkonia states as statistics increases competitive results on B c expected from the first physics run in 2009 quarkonium related activity increasing in the collaboration, many interesting studies to be performed on first data looking forward for the first collisions... G. Graziani slide 21 QWG08