Quarkonia production with the HERA-B experiment J. Spengler, MPI Heidelberg

2 The Hera-B Detector Fixed target detector at e-p ring HERA, Desy High rate forward spectrometer (< 40MHz) Wire targets (different materials) in proton halo Proton beam at 920 GeV/c (√s = 41.6 GeV) High resolution vertexing Very good particle ID for (e, , , K, p) Hardware track trigger for lepton pairs Multiple trigger level On-line event reconstruction p- beam z [cm] 12 C 48 Ti 184 W

3 The Hera-B Detector Angular coverage in bending plane: mrad

4 Data Sample Data taking: 30. Oct Mar · 10 6 dilepton triggered events with ~300,000 J/  achieved J/  rates: / hour in 2000: / hour 210 · 10 6 minimum bias events achieved logging rates: 1000 Hz (1.7 TB/d) 90 · 10 6 hard photon + Glueball trigger see posters of W. Gradl (Q21) and M. Villa (Q20) see talk of A. Gorisek; posters of T. Knöpfle (S10), C. van Eldik (S8) and T. Zivko (S9) see poster of M. Bruschi (Q22)

5 1) p t distribution x F distribution A-dependence Decay angle distribution 2)  (2s) production 3)  c /J/  production ratio 4) bb cross section 5)  production Topics e + e -  +  - cc  (2s) bb  (1-3s) J/  Disclaimer: All results are preliminary

6 J/  production; e + e - Dilepton mass accessible from GeV/c 2  (2S) J/    80% of statistics ≈101,000 J/  width: 64 MeV/c 2

7 J/  production;  +  - Approx. 177,000 events Mass: 3095 MeV/c 2 Width: 44 MeV/c 2 Approx. 3,000 events Mass: 3674 MeV/c 2 Width: 53 MeV/c 2  (2S) J/ 

8 p T distribution of J/  80% of e + e - sample Parameterization: Results for : TargetExp.Rangeee  error C 920< W 920< Au 800E789< Si 800E771< stat. only

9 x F distribution of J/  Parameterization: TargetExp.Rangec C, W <x F <0.15 (5-6.5)  0.3 Si 800E <x F <  0.23 Au 800E <x F <  0.04 Au 800E <x F <  0.18 Negative x F range accessible for the time 10% of e + e - sample Is it adequate to describe the exp. data ??

10 A-dependence of J/  Parameterization of cross section: Determine  from two different targets: C (A=12.0) and W (A=183.8) target 25% of full e + e - sample Ratio of efficiencies includes full detector + trigger simulation Ratio of luminosities under investigation  norm. to E866 result stat. errors only

11 A-dependence of J/  Expected stat. error for full data sample: HERA-B range NRQCD pred.: R. Vogt Nucl. Phys. A700 (2002) 539 BCKT pred.: K.G. Boreskov, A.B. Kaidalov JETP. Lett. 77 (2003) 599

12 cos  distribution of J/  Parameterization: TargetExp. C, W 920 (-0.5;+0.1)  0.1 Be 530E672/  0.15 Be 800E672/  0.15 Si 800E  0.12 Cu 800E  0.08 J/  polarization described by parameter : = (0,1,-1)  (no, trans., long.) polarization Expected error of vs. p T (Muon channel): 80% of e + e - sample Important tests of models

13  (2S) to J/  ratio Measure  (2S)  e + e - relative to J/  to reduce systematic uncertainties Carbon target 30% of e + e - statistics used n J/  = 30k n  (2S) = 650

14  (2S) to J/  ratio R  (2S) = 0.13 ± 0.02   (2S) = 46 ± 12 nb/N  J/  /   (2S) = 0.72  0.01 Stat. errors only; Use  (J/  ) = 357±8±27 nb/N based on E771 and E789 results Systematic studies ongoing Muon channel gives compatible result

15  c to J/  production ratio ECAL resolution does not allow to separate  c1 and  c2 states (  m = 46MeV).  c0 neglected due to small Br.   ≈ 0.4 Results of 2000 (Phys.Lett. B561(2003) 61: N(  c ) = 370  74 (both  +  -, e + e - ) R(  c ) = 0.32  0.06  0.04

16  c to J/  production ratio  m (GeV/c 2 ) R(  c ) = 0.21±0.05 Systematic studies ongoing Electron channel gives compatible result Analysis of 2002/03 data: Comb. background by event mixing Carbon target In 15% of  +  - statistics we find about 1300  c Expect N(  c ) ~ 15k for full sample

17 pA  bb+ X, b  J/  +Y Method: Detached vertex analysis to separate B signal (decay length ~7 mm) from direct J/   Results of 2000: Eur. Phys.J. C26(2003) 345 : e + e - = ;  +  - =

18 pA  bb+ X, b  J/  +Y Analysis of 2002/03 data: 35% of e + e - and  +  - statistics Expect N B ~ 100 for full sample Carbon + Tungsten target J/  acceptance: -0.35<x F <0.15 (90% of bb cross section) Preliminary results of both channels compatible 1.5  lower than 2000 measurement

19 pN  + X,  +  -, e + e - M(  +  - ) (GeV/c 2 ) M(e + e - ) (GeV/c 2 ) Comb. BG Drell-Yan Comb. BG Drell-Yan contribution compatible with E866

20 pN  + X,  +  -, e + e - Events Br d  /dy  y=0 +-+- 33±73.9±1.1 pb/N e+e-e+e- 31±102.9±1.2 pb/N both3.4±0.8 pb/N √s (GeV) All C and W data used Relative production of  (1S)/  (2S)/  (3S) fixed on E605 data  shapes taken from MC Modified Craigie applied to allow for nuclear suppression:  =0.99  0.05 Not used in fit

21 Summary o HERA-B has finished data taking. o Large dilepton sample (both  +  -, e + e - ) allows for detailed study of J/  (300k),  (2S),  and bb- production o Quality of data is very good o HERA-B has large acceptance (negative x F ) and good particle identification o Analysis of 2002/03 data in progress o First preliminary results presented o New collaborators welcome to contribute to analysis of this rich data sample