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Bernhard Schmidt DESY Das Experiment & seine Ziele März 2002 (Hintergrundinformation für PR)

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Präsentation zum Thema: "Bernhard Schmidt DESY Das Experiment & seine Ziele März 2002 (Hintergrundinformation für PR)"—  Präsentation transkript:

1 Bernhard Schmidt DESY Das Experiment & seine Ziele März 2002 (Hintergrundinformation für PR)

2 - Fixed target Experiment, benutzt nur die HERA Protonen - Vorwärtsspektrometer mit Teilchenidentifizierung p target - hohe Wechselwirkungsraten (10 7 pro Sekunde) mrad ~ 85% von 4

3 Internes Drahttarget im Vakuumsystem des HERA-p Rings - stable routine operation, IR MHz - basically smooth cohabitation with ep experiments Target wires inside vacuum vessel Carbon Aluminium Titanium Palladium Tungsten

4 Produced Luminosity ~ inelastic interactions ! Rate fluctuations 10 1m m Mo FrSaSun

5 Das Spektrometer : Dipolmagnet + Spurdetektoren Bdl=2 Tm Vertex Tracker Main Tracker

6 The Vertex Tracking System 64 double sided Si µ-strip detectors in 8 super layers read out channels Roman pot system in vacuum tank Detector modules movable radial and laterally by manipulators

7 Detector modules Steel bands Caps removed

8 Distribution of reconstructed Primary vertices on 8 wires The VDS works routinely and close to design specs = 50 µm z = 500 µm impact parameter resolution P [GeV]

9 Main Tracker (gas filled detectors) tracking in high flux environment particles / sec 1/r 2 ITR -r min = 6 cm - < 10 6 particles cm -2 sec -1 - forward hemisphere in CM -r min = 20 cm - < 10 5 particles cm -2 sec -1 - backward hemisphere in CM OTR

10 I T R The world largest (gas) micro pattern tracker individual chambers - 27 x 27 cm 2 each - 18 m 2 detector surface read out channels (ADC) Inner Tracker Construction of ITR chambers - two step gas amplification - Micro Strip Gas Chambers - Gas Electron Multiplier µm strip pitch on glass substrate - only 6 mm total height - read out by custom made ASIC chips (HELIX) - neue Technologie ! CMS, LHC-b -> no

11 Run time experience in no routine operation so far - need careful training - large gain variations between chambers - individual gain adjustment needed - no trigger signals due to large feedback noise Performance figures efficiency >90% seems possible (design 98 %) resolution ~80µm (at design) HV stability fine, no problems at high rates First real experience in 2002

12 O T R Construction of OTR modules - open honeycomb geometry - 5 mm and 10 mm drift cells - produced layer by layer - wires supported by FR4 bridges - no forced gas flow The world largest honeycomb tracker individual modules - max. of superlayer 4.6 x 6.5 meters m 2 detector surface read out channels (TDC) Thin, lightweight (X 0 ) construction self sustaining mass producible affordable OTR

13 Peking Dubna Zeuthen Hamburg OTR World work places Module Mass Production OTR mass production was a big enterprise....our courageous young colleagues faced the challenge Mio solder points on wires ….! > 100 physicists and technicians working in parallel on 4 different places 1ooo modules produced in 9 months !

14 All OTR superlayers installed by end 1999.

15 OTR routinely used for tracking in 2000 Performance and problems : HV stability at the limit voltage ~4% reduced compared to test beam substantially improved during shutdown, capacitors replaced Additional noise from TDC - trigger connection Thresholds 4 fC instead of 2.5 fC big improvement during shutdown, new drivers, optimisation of cabling etc.

16 p Teilchenidentifizierung RICHECALµ-Detektor 20 m

17 RICH detector 2 [mrad ] 2 Particle Separation Cherenkov relation for Read out by multi- anode phototubes NO -TAMEA chambers - CsI cathodes for high rate environment ! Very stable in 2000 # photons, resolution at design 1/p 2 [GeV/c] -2 e K p

18 -electron pre-triggers -photon detection ECAL

19 0 …. used for online calibration 2000 largely completed some problems with noise, stability, hot channels.. Draw back : HERA-B got fatter than foreseen dead material! > 1 X 0 in front of ECAL Shutdown : Modified analogue read out with better S/N Shutdown : All tracking chambers in Magnet removed

20 Muon detector -drift tubes + iron absorber 4 superlayers 3 types of chambers Tube chambers (342) : 2 cm rectangular aluminium profile as drift tubes Pad chambers (132): as tube chambers, additional cathode pads for fast trigger signals Pixel chambers (16): gas pixel chambers,short wires parallel to beam. Covering the innermost part ~ cha. ~8 000 cha. ~5 300 cha. µ pre-trigger

21 Experience in 2000 run : tube chambers work fine with efficiency close to design gas changed to CH 4 -free mixture due to anticipated aging problems pixel chambers ok, initial noise problems solved but not used for tracking so far (missing ITR) main worry : problems with system noise, especially for pad read out ! low pre-trigger efficiency ! Shutdown work : chambers taken out and minor problems fixed (gas leaks, electronics problems) pad system completely dismounted and overhauled noise situation improved by better grounding scheme Muon identification + tracking :

22 The HERA-B DAQ and Trigger System suppression factor all hardware set up - all but L1-trigger used at design performance in Suppression factor 240 events processed simultaneously LINUX farm, highly flexible 128 ev. deep pipeline 1.7 Gbyte/sec Full event reconstruction in 240 nodes LINUX farm CERN Courier 300/450 MHz->1.4 GHz

23 First Level Trigger & pre-trigger - starting from pre-trigger seeds electrons muons - following lepton track candidates through chambers -> trigger tracks - combining track pairs - applying mass cut ( > 2 GeV) in less than 12 µsec network of custom made processors interconnected by high speed optical links Lepton pair trigger 2000 : stuck in commissioning phase

24 Das Spektrometer funktioniert …. rekonstruierte (seltsame) Zerfälle Ks0Ks0 p L - asymmetry p T [GeV/c] (2000er Daten)

25 Di-lepton trigger Elektronen Muonen

26 CP Wozu der Aufwand ??? CP violation in B - decays The initial goal B 0 J/ K s e + e BR = BR = 0.12 BR = 0.7 The golden decay is rare ! 1 out of ~ B 0 CP measurement needs > 1000 golden decays

27 - rareness of decay : impurity of B sample : Signal/BG = ! To see CP : ~1000 clean events needed with ~ 25 % efficiency observe ~10 14 events ! detector standing high rates for long time sophisticated trigger event selection data acquisition & HERA is not a very good place to produce Bs… B / tot = seconds 10 7 events / second

28 das hat nicht so ganz funktioniert… 1.HERA-B hat an vielen Stellen technologisches Neuland betreten 2.Die dabei aufgetretenen Probleme waren DEUTLICH mehr und gravierender als von den Experten erwartet 3.Das Zeitplan für HERA-B hatte keinerlei Reserven 4.Das Konzept von HERA-B ist extrem anfällig, auch gegen kleine Unzulänglichkeiten, Erfolg = (Einzelperfektion) n …… ABER : HERA-B hat enorme technologische Einsichten und Erkenntnisse gebracht …-> LHC-Experimente

29 Wie geht's weiter ? Was macht man jetzt mit dem Detektor ? -hochspezialisiertes Experiment : lepton pair trigger, m ll > 2 GeV (im wesentlichen J/ ) Viel häufiger als J/ aus B-Zerfällen sind direkte J/ Was ist daran interessant ?? Charmonium Produktion in Kernen ! p+N -> J/ X p+N -> X Als Funktion der Massenzahl N des Targets.. cc = 0 N 1 suppression

30 Positive x F : nuclear medium sees only pre.-res. state ratio /(J/ ) should be A-independent (universal suppression coefficient) Negative x F : nuclear medium sees fully formed charmonium states suppression very different for J/, c ! Here we are ! xFxF Here data exist Here NO data exist Grosse Winkel !

31 HERA-B 2002 / : resume regular data taking - complete the commissioning -understand capabilities of detector and trigger - get Physics data ! measurement of B -> J/ X J/ ~ 30 % (mainly systematic) Measurement of charmonium production for different target materials (C, Al, Ti, Pd, W) charmonium suppression - different targets simultaneously (relative measurements) - measure J ~1.5 M), ~26 k), c ~100 k), - sensitive in negative X F range (-0.3 to +0.2) - observe full final state = 0 A expected error on : < 1% for each X F bin Firsts result from 2001 commissioning run

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