Prospects for quarkonium studies at LHCb Quarkonium Production

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

LHCb Detector Forward Spectrometer Geometry, with angular acceptance 15<q<300 mrad Performance numbers relevant to quarkonium analyses: Charged tracks Dp/p = 0. 35 % - 0. 55%, s(m)=12 -25 Me. V/c 2 ECAL s(E)/E= 10% E-1/2 1 % (E in Ge. V) muon ID: e(m m) = 94 %, mis-ID rate (p m) = 3 % Vertexing: s(L)=250 mm (Primary Vertex Resolution: 10 mm in x/y, 60 mm in z) 2

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

Monte Carlo Tools PYTHIA 6. 3 for the studies shown here: PYTHIA 6. 4 for the current Monte Carlo productions: Production of J/y through Color Single Model. With Color Octet Model added, tuned to reproduce CDF measurements see note CERN-LHCb-2007 -042. Evt. Gen 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. 4

Monte Carlo J/y Samples LHCb MC (14 Te. V, Pythia 6. 3) 3<h<5 In LHCb acceptance (3<h<5, p. T<7 Ge. V/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. 5

J/y m m Reconstruction + Selection based on positive muon identification of the two m, cut on the m transverse momentum p. T>0. 7 Ge. V/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 Me. V/c 2, S/B=17. 6 ± 2. 3 in ± 3 s mass window, 1. 3 x 109 reconstructed after L 0 trigger J/y for 1 fb-1 ( =14 Te. V) Or 0. 65 x 106 for 1 pb-1 at = 7 Te. V LHCb Minimum Bias Monte Carlo (14 Te. V) 6

Separating prompt 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 Te. V) Combined mass/pseudo-propertime fit will allow to measure both prompt and J/y from b production cross sections in h and p. T bins: 4 pseudo-rapidity h bins, 3 < h < 5. 7 transverse momentum bins p. T, p. T<7 Ge. V/c. 7

Example: fit on MC at = 14 Te. V Sample corresponding to 0. 8 pb-1, = 14 Te. V Signal: Inclusive J/y sample Background: toy Monte-Carlo reproducing behaviour (mass and pseudolifetime) seen on the Minimum Bias sample. LHCb Inclusive J/y Monte Carlo + Toy MC (14 Te. V) Results (J/y with 3<h<5 and p. T<7 Ge. V/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 5 pb-1 8 of data at = 7 Te. V.

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. 9

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 p. T, separating prompt and J/y from b, With full angular analysis, in different reference frames. 10

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

+ Y(1 S) → m m Loose muon ID selection, and transverse momentum requirement (p. T(m)>1. 5 Ge. V/c). L 0 trigger efficiency: 96 % Mass resolution: 37 Me. V/c 2 Similar reconstruction and resolutions will be obtained for the Y(2 S) and Y(3 S) 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 p. T. LHCb Inclusive Y Monte Carlo (14 Te. V) 12

cc reconstruction J/y selection, adding a photon detected in the ECAL with p. T(g)>500 Me. V/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 Me. V/c 2. cc 1 cc 2 LHCb Inclusive J/y Monte Carlo (14 Te. V) 13

cb 2 reconstruction Reconstruction of cb 2(1 P) → Y(1 S) g Photon detected in ECAL, with p. T(g) > 500 Me. V/c Mass resolution: 47 Me. V/c 2 LHCb Inclusive Y Monte Carlo (14 Te. V) 14

hc reconstruction Besides di-muon states, LHCb detector performances will allow to study other states though hadronic decay modes. Reconstruction of hc → hc g is difficult (E(g)~500 Me. V in the hc rest frame). Hadronic decay channels look promising: hc → pp, hc → f K+ K-, hc → f p+ p-. In particular, hc → pp probably visible with first year data, which will give access to s(hc)x. Br(hc → pp) relative to s(J/y)x. B(J/y → pp). LHCb Signal Monte Carlo + Toy MC (10 Te. V) J/y Expected pp mass distribution: Assuming Br(h → pp) = 0. 12 %, c Toy Monte Carlo for background, reproducing background seen on fully simulated minimum bias events, -1 100 pb at = 10 Te. V cc 0 cc 1 hc cc 2 15 m(pp) (Ge. V/c 2)

X(3872) and Z(4430) Reconstruction of X(3872) → J/y p+ pp- (and the control channel Reconstruction of X(3872) → J/y p y(2 S) → J/y p+ p-), prompt or from b: systematic study of this state. Expect 1800 reconstructed B → X(3872) K , with 2 fb-1 at = 14 Te. V, allowing to disentangle unknown quantum number JPC: 1++/2 -+. LHCb Generator Only signal 1++/2 -+ Similar studies for B 0 → Z(4430)+( → y(2 S)p+)K About 6200 signal events can be selected from 2 fb-1 of data at =14 Te. V, assuming B(B 0 → Z(4430)+ K-)x. B(Z(4430)+→y(2 S)p+) = 4. 1 x 10 -5 Possible to confirm the Belle discovery with about 100 pb-1 of data at = 7 16 Te. V.

Bc Measurement of mass, lifetime and production cross section using the decay modes: Bc+ → J/y p+ assuming s(Bc+)=0. 4 mb, and Br(Bc+ → J/y p+) =0. 13 %, expect 310 signal events for 1 fb-1 of data at = 14 Te. V. Production cross section relative to B+(→ J/y K+) Bc+ → J/y m+ X: signal yield one order of magnitude larger, production cross section measurement possible with 2010 data. 1 fb-1, 14 Te. V 17

Conclusions LHCb will measure production cross sections and polarization of di-muon states, in the LHCb acceptance: 3 < h < 5, p. T<7 Ge. V/c. Other quarkonium states will also be looked at: hc, 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(1 S) p+ p-, Bc** → Bc+ p+ p-. 18