CERN November 22, 20041W.H.Trzaska HIP Jyväskylä T0 answers Meeting with LHCC referees CERN, November 22, 2004

CERN November 22, 20042W.H.Trzaska HIP Jyväskylä Old TVDC efficiency plot New TDR figure New TVDC efficiency plot r.m.s. = 3 cm 0 < width < 1.6 m

CERN November 22, 20043W.H.Trzaska HIP Jyväskylä Important: option for T0-A

CERN November 22, 20044W.H.Trzaska HIP Jyväskylä How to translate physics into counts? Contribute more Contribute less diffractive dominate Identified with minimum bias exchange of color neutral objects basis for comparison between pp and HI

CERN November 22, 20045W.H.Trzaska HIP Jyväskylä Detectors understand only counts! What is the multiplicity distribution? Where is the border line between: minimum bias semi central central collisions

CERN November 22, 20046W.H.Trzaska HIP Jyväskylä Multiplicity distribution (Pythia) 30 mm T0-A & T0-C Pythia's predictions are right (if properly interpreted)! A case in point: Croesus, King of Lydia, asked if he should wage war with Persia. Pythia replied: if you waged war you’d destroy a great power. Croesus lost badly! Pythia’a explanation: we meant your power, of course.

CERN November 22, 20047W.H.Trzaska HIP Jyväskylä New simulations What to make of it?

CERN November 22, 20048W.H.Trzaska HIP Jyväskylä What if only one side of T0 responded? No T0 trigger! Trigger&wake-up from V0 No interaction time on-line! Can be calculated off-line –Reconstructed vertex (tracking) –Slightly lower accuracy (~1.4 * 28 ps)

CERN November 22, 20049W.H.Trzaska HIP Jyväskylä Decisions are needed: On radiator’s diameter –30 mm – current baseline –20 mm – proposed by T0 On the number of detectors (T0-A + T0-C) – (current baseline) – (more electronic$ and rack Space) Decision needed by the end of 2004 to keep up with the milestones

CERN November 22, W.H.Trzaska HIP Jyväskylä Major milestones for T0 Nov 2004:Freezing radiator size Dec 2004:Electronics Design Review (joint with V0) Feb 2005: Detector module frozen; mechanics PRR Sep 2005:Full chain readout test Dec 2005: T0 Mechanics ready Feb 2006: Electronics PRR Jun 2006: T0-C ready for installation in ALICE; installation of electronics at CERN; tests of the installed T0-C Dec 2006:T0-A ready for installation in ALICE; tests of the installed T0-A

CERN November 22, W.H.Trzaska HIP Jyväskylä New publicity for T0 Our T0 detector was presented at IEEE in Rome in October 2004 –submitted to Transactions on Nuclear Science Two instrumental papers in preparation –Performance of PMT-187 –In-beam test results of the detector and electronics

CERN November 22, W.H.Trzaska HIP Jyväskylä New shoebox Has been redesigned as the result of June 2004 test at CERN: –Unaltered signal on direct output Time deterioration ≤ 2 ps (was 20 ps) Amplitude ~1.0 (was ~ 0.71) –Reduced PCB size –Reduced power consumption Performance has been tested in Jyväskylä ( T0 ) and Lyon ( V0 ) Further (minor) changes will be implemented –pulse clipping after the first stage OLDOLD NEWNEW

CERN November 22, W.H.Trzaska HIP Jyväskylä New HV divider Fixed all small glitches of the previous design –Output protection High quality components –e.g. uses gold-plated pin connectors Proper fixtures –cables (type and length) –and connectors Tomorrow (24/11/2004) we’ll get the new HV divider for full tests in Jyväskylä

CERN November 22, W.H.Trzaska HIP Jyväskylä New PMT (optimum photocathode sensitivity) Our measurements indicate that we may decrease slightly photocathode sensitivity (to be able to work at higher HV) Tomorrow the new batch of PMTs is arriving for tests in our Lab (using laser and 0.5T magnet) The best performance of a PMT in the magnetic field is achieved at the highest HV setting PMT gain increases with HV

CERN November 22, W.H.Trzaska HIP Jyväskylä New detector shell