# Presentation: 297186

## Quarkonia production with the HERA-Bexperiment

- J. Spengler, MPI Heidelberg

## 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

## The Hera-B Detector

- Angular coverage in bending plane: 15 - 220 mrad

## Data Sample

- Data taking: 30. Oct 2002 - 3. Mar 2003
- 150 · 106 dilepton triggered events with       		  ~300,000 J/
- 	achieved J/ rates: 1200 - 1400 / hour
- 		             in 2000:  30 - 40 / hour
- 210 · 106 minimum bias events
- 	achieved logging rates: 1000 Hz (1.7 TB/d)
- 90 · 106 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)

## Topics

-     xF distribution
-     A-dependence
-     Decay angle distribution
- 2) (2s) production
- 3) c/J/ production ratio
- 4) bb cross section
- 5)  production

**e****+**** e****-**
******+ ********-**

****c

- (2s)

- bb

- (1-3s)

- J/

- Disclaimer: All results are preliminary

## J/ production; e+ e- 

- J/ production; e+ e-

- Dilepton mass accessible from 0 - 11 GeV/c2

- (2S)

- J/

- 

- 

- 80% of statistics  ≈101,000 J/width: 64 MeV/c2

## J/ production; +- 

- J/ production; +-

- Approx. 177,000 eventsMass: 	3095 MeV/*c*2Width: 	44 MeV/*c*2

- Approx. 3,000 eventsMass: 	3674 MeV/*c*2Width: 	53 MeV/*c*2

- (2S)

- J/

## pT distribution of J/ 

- pT distribution of J/

- 80% of e+e- sample

- Parameterization:

- Results for <pT>:

| Target | Exp. | Range | e |  | error |
| --- | --- | --- | --- | --- | --- |
| C  920 |  | < 4.8 | 1.22 | 1.22 | 0.01 |
| W  920 |  | < 4.8 | 1.29 | 1.30 | 0.01 |
| Au 800 | E789 | < 2.6 |  | 1.29 | 0.009 |
| Si  800 | E771 | < 3.5 |  | 1.20 | 0.01 |

- stat. only

## xF distribution of J/ 

- Parameterization:

| Target | Exp. | Range | c |
| --- | --- | --- | --- |
| C, W  920 |  | -0.35 <xF<0.15 | (5-6.5)0.3 |
| Si  800 | E771 | -0.05 <xF<0.25 | 6.540.23 |
| Au 800 | E789 | -0.035<xF<0.135 | 5.210.04 |
| Au 800 | E789 | 0.30<xF<0.95 | 4.910.18 |

- Negative xF range accessible for the time

- 10% of e+e- sample

- Is it adequate to describe the exp. data ??

## 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

## 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

## cos distribution of J/ 

- Parameterization:

| Target | Exp. |  |
| --- | --- | --- |
| C, W 920 |  | (-0.5;+0.1)0.1 |
| Be 530 | E672/706 | 0.010.15 |
| Be 800 | E672/706 | -0.110.15 |
| Si  800 | E771 | -0.090.12 |
| Cu 800 | E866 | 0.0690.08 |

- J/ polarization described by parameter :
-  = (0,1,-1)   (no, trans., long.) polarization

- Expected error of  vs. pT (Muon channel):

- 80% of e+e- sample

- Important tests of models

## (2S) to J/ ratio 

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

## (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

## 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

## c to J/ production ratio 

- m (GeV/c2)

**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

## 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- =               ;  +-=

## pA bb+ X, bJ/+Y

- _Analysis of 2002/03 data:_
-  35% of e+e- and +- statistics
-  Expect NB ~ 100 for full sample
-  Carbon + Tungsten target
-  J/ acceptance: -0.35<xF<0.15 (90% of bb cross section)

-  Preliminary results of both channels compatible
-  1.5   lower than 2000 measurement

## pN  + X, +-,  e+e-

- pN ****** **+ X, ********+****-,  e+e-

- Drell-Yan contribution compatible with E866

## pN  + X, +-,  e+e-

|  | Events | Br• d/dyy=0 |
| --- | --- | --- |
| +- | 33±7 | 3.9±1.1 pb/N |
| e+e- | 31±10 | 2.9±1.2 pb/N |
| both |  | 3.4±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

## Summary

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