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HERA-B is a working experiment at DESY (Hamburg) ... ( Improved since y2k run.) Preferred configuration: W(I1) & C(B1) bkg acceptable. QM2002 ... – PowerPoint PPT presentation

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1
First Results from HERA-B
A. Zoccoli Università and INFN Bologna For the
HERA-B Collaboration
  • Outilne
  • Introduction
  • Detector trigger
  • Results from 2000 data
  • Future perspectives

Quark Matter 2002 Nantes, France July 23th, 2002
2
Introduction
HERA-B is a working experiment at DESY
(Hamburg). The original goal was to measure CP
violation in the B ?J/? K0s channel.
  • Very sophisticated and challenging detector.
  • Very selective J/? trigger.
  • Capability to reconstruct the full event

HERA-B can give a valuable contribution in the
J/? studies. ? Reference measurements in
p-Nucleus collisions.
3
Detector design
  • p-Nucleus interactions at 920 GeV
  • Event rate 10 MHz

Tracking
ECAL
Wire targets
920 GeV p-beam
Vertex detector
Magnet
RICH
Muon detector
- Large central acceptance ( 5 gt ?lab gt 2 ) - Up
to 4107 interactions/s (5ev/bx)- Highly
selective di-lepton (J/? ) trigger
4
Target
Background vs Interaction rate
8 wiressurroundingbeam 5 materials C, Ti, Al,
Pd, W
Background and rate stability depend on target
material, wire shape position, HERA.
(Improved since y2k run.)
Preferred configuration W(I1) C(B1) bkg
acceptable
5
Trigger DAQ System
Multilevel trigger scheme based on Kalman filter.
10 (5) MHz
Pretrigger/Level 1 (rejection 200-100)
(12 ms)
Level 2 (rejection. 700)
50 KHz
(10 ms)
Full online reconstruction and logging to tape
50 Hz
(1s)
Two PC-Linux farms used in L2 and for the offline
reconstruction.
6
Hera-B physics results
  • Data of the year 2000 (first short physics run)
  • ?limited statistics
  • 2. Commissioning
  • ? trigger and detector not fully available
  • (limited acceptance in xF relatively
    inefficient trigger )
  • Targets
  • C and Ti (single double wire running)

1.4106 di-lepton trigger 2106 Minimum Bias
Valuable to prove the detector capabilities in
view of the next data taking.
7
Minimum Bias studies
V0 production K0s L cross sections versus
A. No Particle ID applied.
Application of PID (RICH) for the detection of
??KK decays.
?, ? hyperons also reconstructed !
8
Dilepton trig. Prompt J/? (Muon)
After di-lepton vertex and soft Muon PID
requests. Di-muon invariant mass distribution
2880?60 J/?
40?10 ?
Study of the differential J/? distributions (XF ,
PT)
9
Dilepton trig. Prompt J/? (Electron)
-Invariant mass cut at the trigger
level. -Di-lepton vertex request.
Particle ID cuts - E/P - Bremsstrahlung request
?BR0.34?0.02?0.02
5710?380ST?280SYS J/?
10
J/? differential distributions
Average between the Muon and the Electron
channels Fit with the usual parametrizations.
First result in the negative XF region. In the
next data taking Hera-B will cover the 0.4,0.3
XF range.
11
Fraction of J/? from ?c
Mass difference spectra
cc ? J/y g
???
Sum-C
C
Entries / 25 MeV/c2
ee?
Sum-Ti
C
Entries / 25 MeV/c2
Sum-All
?MM(J/??)-M(J/?) (GeV/c2)
Background subtracted by mixing J/? and ? from
different events
?MM(J/??)-M(J/?) (GeV/c2)
N (cc ) 400
12
Result on fraction of J/y from cc
p
CSM
p
p
NRQCD
CEM
Rcc 0.321 ? 0.064 ? 0.035
p
In agreement with previous p-N experiments.
For the next data taking - First measurement of
cc suppression in nuclear matter. - Study of
production ratios between J/y , cc and Y. -
Disentangle the 2 cc states (?)
13
The HERA-B ?(bb) Measurement
Principle of the measurement
Normalization on the inclusive prompt J/? cross
section. ? Systematic error minimization


14
?(bb) muon electron signals
Afetr a cut optimization and a Maximum Likelihood
fit we get the following results
Muon
Electron
15
?(bb) Determination
QCD calculations and experimental results
Simultaneous fit to ee- ??- (in acceptance)

(submitted to EPJC)
16
2002/3 Physics Program
  • Base line physics program for next run
  • A) Detailed measurement of atomic number
  • dependence of charmonium production
  • - Extend existing measurements of J/? and ? to
    negative xF.
  • - First measurement of atomic number dependence
    of ?c.
  • B) Improved bb cross section measurement
  • -Systematics limit at ? 15 (normalization).-
    Cross section from full reconstructed B mesons
  • Data for other studies for free e.g.
  • Particle production (?, K , p, V0, Hyperons
    etc.)
  • Hard photon production
  • - Drell-Yan

17
Expected statistics
Expected event yields 2002/3 2000
J/y ( m e ) 4 106
1 104 ?c? J/y g
3 105 4 102 y
1 105
4 101
  • Targets primarily C, W
  • (but also Ti, Al Pd)
  • Acceptance in the range
  • -0.4 lt XF lt 0.3



18
Conclusions
  • HERA-B is a challenging detector built to trigger
    on J/?s
  • First results from 2000 data becoming available
  • Improved detector trigger in 2002 high
    statistics expected
  • Hera-B offers advantages for Heavy flavour pA
    physics
  • different targets, operated simultaneously
  • ? small relative uncertainties
  • large acceptance in negative xF region
  • full event capability PID, including photon
    detection

19
HERA-B
13 Nations 30 Institutes
150 physicists
IHEP, Beijing U. Tsinghua
Norway
China
U. Oslo
LIP, U. Coimbra LIP, U. Lisbon
Portugal
Denmark
NBI, Copenhagen
ITEP, Moscow JINR, Dubna
Russia
U. Humboldt, Berlin U. Dortmund DESY MPI
Heidelberg U. Heidelberg U. Mannheim MPI
Munich U. Rostock U. Siegen DESY Zeuthen
Slovenia
J.F. Inst, Ljubljani
Germany
Spain
U. Barcelona
U. Zurich
Switzerland
INR, Kiev
Ukraine
U. Texas, Austin U. Cincinnati Wayne State U. U.
Houston U. Calif, Los Angeles
INFN, U. Bologna
Italy
U. Utrecht NIKHEF
USA
Netherlands
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