HERA-B

A. Zoccoli - PRC open session 16-May-2002

HERA-B

A. Zoccoli

Università and INFN - Bologna

PRC open session 16th May 2002


Outline

Status of the 2000 data analysis

Detector and trigger:

present status

results of 2001 data analysis

2002/3 Physics program

Summary


Run 2000 Analysis Topics

Statistics Minimum Bias: 2 million events (C, Al, Ti, W targets) DiLepton trigger: 0.45 million events DI-

0.90 million events DI-e

Minimum biasno trigger

Ks0 & production cross section.

Inclusive particle productions. polarization

Trigger Topic

Lepton pair:e+ e- ECAL pretrig Muon pretrig+ SLT tracking

bb production cross section Fraction of J/from c

Inclusive J/ xf & pt distributions J/production cross section

IR ~ 5 MHz


Minimum Bias: V0 production V0 Cross section

K0

0

K0s & mass distr.

K0s & nuclear dependence

K0

0

0


Dilepton trig. : Prompt J/ (Muon)

PID: likelihood from MUON detector and RICH

Trigger tracks confirmed by reconstruction

Cf

f

xAdx

dN)1( Xf:

622

))/(1( ot ppAdp

dN

t

pt :


x

ee

MAGNET

ECAL

Dilepton trig. : Prompt J/ (Electron)

Particle ID: E/P +

bremsstrahlung

Trigger tracks confirmed by reconstruction:

Total number of J/ in the sample: nP= 5710380ST280SYS

BR=0.340.020.02


In 2002:- First measurement of c suppression in nuclear matter.- Study of production ratios between J/c and ‘.- Disentangle the 2 c states (?)

Fraction of J/from c c J/

M=M(J/)-M(J/) (GeV/c2)

En

trie

s /

25

MeV

/c2

ee

C

C

Ti

Ti

AllAll

)/J(

)/J(Br)(R cc

c

Preliminary results:

Rc =(Carbon)

Rc =(Titanium)In agreement with previous p-N experiments.


The HERA-B (bb) MeasurementPrinciple of the measurement:

b J/ X + - X b J/ X e+ e- X

Look at the chain: via detached J/ vertices.

l+

J/Bz

X

l-

IW

upstream | downstream

Normalization on the inclusive prompt J/ cross section. Systematic error minimization


The Muon Channel: b-cuts

UNBINNED LIKELIHOOD FIT (due to low statistics):- Sig. shape from MC,- BKG shape from data.

Mass spectrum upstream and downstream:

Cuts applied: z > 7.5 z Imp. Param. to wire Iw > 35 m Imp. Param. to primary vtx Ip> 160 m

REAL

MC

BKGS

Optimization procedure:

2.21.51.9Bn

+ - invariant mass ( GeV/c2 )

En

trie

s / 1

00 M

eV/c

2


The Electron Channel: b-cuts

3.93.2

8.6B

n

UNBINNED LIKELIHOOD FIT (due to low statistics):- Sig. shape from MC,- BKG shape from data.

Cuts applied: z > 0.5 cm e Imp. Param. wire Iw > 200 m , orMin. dist. @ ZW to any other track > 250 m

REAL

MC

BKGS

Optimization procedure:

Mass spectrum upstream and downstream:

e+e- invariant mass ( GeV/c2 )

En

trie

s / 1

00 M

eV/c

2


(bb) Determination

Simultaneous fit to e+e- & +- (in acceptance):

QCD calculations and experimental results:

Extrapolation to the Hera-B acceptance:

5.7 1.5 1.3 nb/nucl.E789:727

1743 nb/nucl.E771:

TOT(bb) = nb/nucleon(syst)67(stat)

141232


Summary of 2000 analysis

The analyses on Dilepton and Minimum Bias data taken during the 2000 run are well advanced.

Understanding of the detector, of the efficiencies, of the performances, etc.

Preparation of the analysis codes in view of the 2002/3 run.

Papers on bb cross section (almost final), production of J/from c , V0 production cross section and J/decayspectra are in preparation.


2002/3 Detector Configuration

Thinnerbeampipe:500m 300m

No magnet tracker! Motivation to reduce material:- Improve calorimeter performance. e.g. 1.5x better resolution on (c - J/) mass difference- Influence on tracking shown to be small at 5 - 10 MHz interaction rate.- (being kept in a safe place in case of possible future use)


Status & actions during the shutdownVDS Fully operational in 2000. Detector modules repaired.

ITR Installation of missing chambers. Dead chambers repaired.Noise reduction (improved grounding).

OTR Dead HV groups repaired and HV stability improved Noise reduction Higher efficiency expected.

RICH Fully operational in 2000.

ECAL Reduction of common noise (grounding improved) better E resolution.

MUON Dead channels repaired.Noise reduction higher efficiency expected.

The HERA-B detector was operational in 2000 run. Many improvements during the shutdown. Partially checked in the short run end of 2001.

Status of detector components

New improved grounding scheme on all chambers:

reduction of pick-up lower fluctuation of raw data

Old

New

ADC counts

ADC counts

Beforemagnet

Aftermagnet

Itr in 2002

Stations

Wid

th o

f R

aw D

ata

[AD

C]

~ 3% of dead channels vs ~15% in 2000.

Effect of Dead HV groups Repair, geometrical efficiency:

Noise reduction

Higher efficiency expected To be measured in the near future

OldThreshold

Otr in 2002

100

90

ADC pedestals in the new ECAL run configuration:

Better performances in PId To be measuerd in the near future

Ecal noise situation

December 2001

2000 Run


Status of First Level TriggerThe First Level trigger was not fully commissioned in 2000.

Low efficiency due to both trigger and detector performances.

Main activities: Optical Links: despite large effort, will remain the most critical HW

item Flt Algorithm fully optimized. Processor logic fully verified (vector test). Detector mapping ready, verification in progress Online software improved system New RICH multiplicity veto system available

Waiting for data to check the performance !


December 2001 dataMinimum Bias (int. Trig.): ~500k events only ~10 hours RUN !

Charged tracksChecks on reconstruction and alignment, comparison with 2000 data:

K0

0

Inclusive distributions K0s & mass distr.

2000

2001

KS width already smaller than in 2000!


December 2001 data - II

More data welcome !

NeutralsChecks on reconstruction and calibration:

Inner Middle Outer

0 seen in the Outer. After one calibration iteration (out of three). Width very close to that of 2000.


2002/3 Physics Program

Base line physics program for next run:

A) Detailed measurement of atomic numberdependence 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


Additional topics: - Charmonium spectroscopy – Drell-Yan - Measurement of production - Open charm production - Strangeness production in nuclear matter - polarization

Expected event yields: 2002/3 2000 J/( & e ) ~4 106 ~1 104

c J/~3 105

~1 102

´ ~1 105 ~4 101

Targets: primarily C, W (but also installedTi, Al & Pd) Acceptance in the range -0.4 < xf < 0.3

2002/3 Physics Program – II


Summary

The analysis of 2000 data is approaching completion.

Improved performance of the HERA-B spectrometer and understanding of the trigger. first data look promising trigger ready to be tested

Physics program: very large statistics of charmonium states expected in the next run.


Summary

HERA-B is anxiously waiting for new data to come.



Systematic checks (e-channel)DECAY LENGTH

LIKELIHOOD FIT:

MC =0.810.03 cm

RD =1.000.30 cm

BKG=0.360.13 cm

Different background optimisation:

Upstream

Downstream

Dz

(cm

)

Mass (ee) (GeV/c2)

Bkg

Bkg Bkg


Status & actions during the shutdownVDS Fully operational in 2000. Detector modules repaired.

ITR Installation of missing chambers. Dead chambers repaired.Noise reduction (improved grounding).

OTR Dead HV groups repaired. Noise reduction Higher efficiency due to lower threshold

cut.

RICH Fully operational in 2000.

ECAL Reduction of common noise (grounding improved) better E resolution.

MUON Dead channels repaired.Noise reduction lower threshold, higher efficiency.

The HERA-B detector was operational in 2000 run. Many improvements during the shutdown. Partially checked in the short run end of 2001.

Status of detector components


New improved grounding scheme on all chambers:

reduction of pick-up lower fluctuation of raw data

Old

New

ADC counts

ADC counts

Beforemagnet

Aftermagnet

Itr in 2002

Stations

Wid

th o

f R

aw D

ata

[AD

C]


~ 3% of dead channels vs ~15% in 2000.

Effect of Dead HV groups Repair, geometrical efficiency:

Noise reduction

Higher efficiency expected To be measured in the near future

OldThreshold

Otr in 2002

100

90


ADC pedestals in the new ECAL run configuration:

Better performances in PId To be measuerd in the near future

Ecal noise situation

December 2001

2000 Run

HERA-B

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