1. Physics from HERA-B Torsten Zeuner PRC open session 7th May 2003
Universität Siegen
PRC open session 7th May 2003

2. Data taking 2002/03 Data taking 30. October 2002 – 03. March 2003
35 %
~ 35 % running time delivered
of which ~ 70 % used for data taking
~ 150 · 106 dilepton triggered events
~ 210 · 106 minimum bias events
achieved J/ψ rates : 1200 – 1400 J/ψ per hour
J/ψ per hour (2000)

3. J/ψ - Statistics J/ψ→µ+µ- : full statistics
J/ψ→e+e- : 40 % of statistics
J/ψ→µ+µ- : full statistics
N(J/ψ) k
M(J/ψ) GeV
σ(J/ψ) MeV
N J/ψ k
M J/ψ GeV
σ J/ψ MeV
Nψ(2s) k
Mψ(2s) GeV
σψ(2s) MeV
No Bremsstrahlung
requirement
Entries/30 MeV/c²
N(J/ψ) k
M(J/ψ) GeV
σ(J/ψ) MeV
≥ 1 Bremsstrahlung
requirement
μ+μ- invariant mass [GeV/c²]

4. Analysis in Progress Improve pN→bbX cross section measurement
higher statistics in inclusive analysis : b→J/ψX (J/ψ→ee/μμ)
exclusive recon. of b decays (B±→J/ψK±, B0→J/ψK±π±, B→J/ψKs, B→J/ψKK)
Understand double semileptonic b decays: bb→µµX
Atomic number dependence of charmonium production in pN
extend existing Fermilab measurements of J/ψ, ψ´ to negative xF
measurement of atomic number dependence of χc
Minimum Bias physics
Open charm production
Strangeness production in nuclear matter
Λ polarization
Measurement of pA→ Υ cross section (ee/μμ)
Upper limit on Br(D0→μ+μ-)
Direct photons
...

5. bb Cross Section Measurement
Inclusive reaction pA → bb X,
with bb  J/ X → (e+ e- / µ+ µ-) X
Select b  J/ X via detached J/ψ vertices IW l+
J/ B
z X l-
upstream | downstream
Normalization to prompt J/ψ
(pA  J/X)
Minimize systematic errors

6. Detached J/ψ Analysis J/ψ→e+e- J/ψ→µ+µ- # J/ψ = 40 ± 12
Δz/σz > 10
impact par. cut
No bremsstrahlung
requirement
(40 % of statistics)
Preliminary
downstream
2000 :
upstream
# J/ψ = 40 ± 12
J/ψ→µ+µ-
Δz < cm
Δz > 0.5 cm
Impact par. cut
(60 % of statistics)
Entries
Χ2/ndf /26
N(J/ψ) ± 11.22
M(J/ψ) ± 0.022
σ(J/ψ) ±
Preliminary
2000 :
No upstream J/ψ
# J/ψ = 40 ± 11

7. Charmonium Production
Typical parametrisation of pA cross section
σpA = σpN · Aα
if α = 1 for all xF, pT
no nuclear effects
Measure for J/ψ and χc nuclear dependence vs. xF, pT
Using Carbon & Tungsten
2-wire sample
NRQCD
K.G.Boreskov, A.B.Kaidalov hep-ph/ χc
total J/ψ
direct J/ψ
ψ(2s)
Input to test
different models
R.Vogt Nucl. Phys. A700(2002)539
χc production characteristics, nuclear dependence nearly unexplored

8. Charmonium Production
xF distribution
Statistical errors only
No corrections applied !
xF range : [- 0.35, 0.15]
Statistical error estimation for 2-wire sample (only μ-channel)
Muon channel full statistics
e-channel increases statistics up to factor 2 (depending on particle ID cuts)

9. Charmonium Production : χc
Fraction of J/ψ produced via χc
ΔM = M (J/ψ γ) – M (J/ψ)
background subtracted
Entries/12.5 MeV/c2
ΔM [GeV/c²]
N(χc) = 6806 ± 1058
M(χc) = ± GeV
σ(χc) = ± GeV
2000 √
Only µ-channel
Preliminary
Measurement 2000 based on
380 ± 74 χc
First measurement of χc suppression
in nuclear matter possible !
Rχc = 0.32 ± 0.06stat ± 0.04sys

10. Upsilon Production : σ(pA→ Υ )
Υ→μ+μ-
Υ→e+e- Y Y´
Y´´ Υ Υ´
Υ´´
Preliminary
Existing
measurements by
E605, E771
contradictory
Preliminary
# Υ events 35 ± 8
Width 157 MeV
# Υ events 33 ± 10
Width 335 MeV
Width : in agreement with MC
Measurement of the Υ production cross section is feasible
may help to distinguish between Fermilab measurements

11. Minimum Bias Data sample
Open charm signals
~210·106 events recorded on
Carbon, Tungsten and Titanium wire
N(D0) ± 27
M(D0) GeV
σ(D0) 30 ± 5 MeV
K0s
2.8 M
85 % of statistics 0
620 k
~ factor 300 to
2000 statistics 0
310 k -
10 k +
6.2 k
Preliminary
0(1530)
1.5 k -
500
N(D+) ± 12
M(D+) GeV
σ(D+) 26 ± 4 MeV +
460
K*0 + K*0
1.1 M 
63 k
85 % of statistics
Measurements of differential cross sections,
atomic number dependence
Measurement of ratio (D+/D0)

12. Expect preliminary results for summer conferences.
Summary
HERA-B detector & trigger in good shape
Data taking : 30.October 2002 – 3.March 2003
J/ψ per hour, 70% of available beam time used
~ 300,000 triggered J/ψ (e+e-/μ+μ-)
~ 210·106 Minimum bias events
Analysis of 2002/03 data in progress
Quality of recorded data looks good, first preliminary results promising
Expect preliminary results for summer conferences.