Das Experiment & seine Ziele

Präsentation zum Thema: "Das Experiment & seine Ziele"—  Präsentation transkript:

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

2 - Fixed target Experiment, benutzt nur die HERA Protonen
- Vorwärtsspektrometer mit Teilchenidentifizierung mrad ~ 85% von 4p - hohe Wechselwirkungsraten (107 pro Sekunde)

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

4 ~ 5•1013 inelastic interactions !
Produced Luminosity ~ 5•1013 inelastic interactions ! Rate fluctuations 10 1mm Sun Mo Fr Sa

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

9 Main Tracker (gas filled detectors) 3•107 particles / sec • 1/r2
tracking in high flux environment ITR OTR rmin = 6 cm < 106 particles cm-2 sec-1 forward hemisphere in CM rmin = 20 cm < 105 particles cm-2 sec-1 backward hemisphere in CM

10 I T R Inner Tracker The world largest (gas) micro pattern tracker
184 individual chambers 27 x 27 cm2 each - 18 m2 detector surface read out channels (ADC) Construction of ITR chambers - two step gas amplification Micro Strip Gas Chambers Gas Electron Multiplier 300 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 First ‘real’ experience in 2002
Run time experience in 2000 - 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 OTR The world largest honeycomb tracker 1000 individual modules
max. of superlayer 4.6 x 6.5 meters m2 detector surface read out channels (TDC) O T R Thin, lightweight (X0) construction self sustaining mass producible affordable 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

13 OTR mass production was a big enterprise ..
..our courageous young colleagues faced the challenge Mio solder points on wires ….! 1ooo modules produced in 9 months ! > 100 physicists and technicians working in parallel on 4 different places Peking Dubna Zeuthen Hamburg OTR World 4 6 5 8 Module Mass Production work places

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 Teilchenidentifizierung
RICH ECAL µ-Detektor p 20 m

17 RICH detector Particle Separation NO Cherenkov relation for q2[mrad] 2
Read out by multi-anode phototubes NO TAMEA chambers CsI cathodes for high rate environment !  Particle Separation K p p 1/p2[GeV/c]-2 Very stable in 2000 # photons, resolution at design

18 ECAL electron pre-triggers photon detection

19 p0 2000 largely completed some problems with noise, stability, hot channels.. …. used for online calibration Shutdown : Modified analogue read out with better S/N h Draw back : HERA-B got fatter than foreseen dead material! > 1 X0 in front of ECAL Shutdown : All tracking chambers in Magnet removed

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

21 Shutdown work : Experience in 2000 run : Muon identification
tube chambers work fine with efficiency close to design gas changed to CH4-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 ! Muon identification + tracking : ->mm2.5 4 ->mm  ->mm1.8 4 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

22 The HERA-B DAQ and Trigger System
CERN Courier 200 128 ev. deep pipeline Suppression factor 1.7 Gbyte/sec 100 240 events processed simultaneously LINUX farm, highly flexible 300/450 MHz->1.4 GHz Full event reconstruction in 240 nodes LINUX farm 10 all hardware set up all but L1-trigger used at design performance in 2000 suppression factor 2•105

23 Lepton pair trigger 2000 : stuck in commissioning phase
First Level Trigger & pre-trigger Lepton pair 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 2000 : stuck in commissioning phase

24 Das Spektrometer funktioniert ….
(2000er Daten) rekonstruierte (seltsame) Zerfälle Ks0 L pT [GeV/c] pL - asymmetry

25 Di-lepton trigger Elektronen Muonen

26 CP CP violation in B - decays B0 J/yKs p+p- e+e- m+m-
Wozu der Aufwand ??? CP The initial goal CP violation in B - decays The ‘golden decay’ is rare ! BR = 5•10-4 1 out of ~ B0 BR = 0.7 B0 J/yKs p+p- e+e- m+m- CP measurement needs > 1000 golden decays BR = 0.12

27 & HERA is not a very good place to produce B’s… sB/tot=10-6
rareness of decay : 4•10-5 impurity of B sample : 10-6 Signal/BG = 4•10-11 ! To see CP : ~1000 clean events needed with ~ 25 % efficiency observe ~1014 events ! 107 seconds • 107 events / second detector standing high rates for long time sophisticated trigger event selection data acquisition &

28 das hat nicht so ganz funktioniert…
HERA-B hat an vielen Stellen technologisches Neuland betreten Die dabei aufgetretenen Probleme waren DEUTLICH mehr und gravierender als von den Experten erwartet Das Zeitplan für HERA-B hatte keinerlei Reserven 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, mll > 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 p+N -> ’X s cc =s0•Na Als Funktion der Massenzahl N des Targets .. a ≠ “suppression”

30 Positive xF : nuclear medium sees only pre.-res. state
ratio Y’/(J/Y) should be A-independent (universal suppression coefficient) Negative xF : nuclear medium sees fully formed charmonium states suppression very different for J/Y‘, cc ! a Here data exist Here we are ! Grosse Winkel ! Here NO data exist xF

31 HERA-B 2002 / 2003 Firsts result from 2001 commissioning run
measurement of  B -> J/yX J/y  ~ 30 % (mainly systematic) 2002 : resume regular data taking - complete the commissioning understand capabilities of detector and trigger get ‘Physics’ data ! Firsts result from 2001 commissioning run Measurement of charmonium production for different target materials (C, Al, Ti, Pd, W) ‘charmonium suppression’ different targets simultaneously (relative measurements) measure J/y~1.5 M), y ‘~26 k), c ~100 k), sensitive in negative XF range (-0.3 to +0.2) observe full final state s = s0 Aa expected error on a : < 1% for each XF bin