J.Pietraszko, HADES Coll. Meeting, GSI Nov ,  – electron multiplicity measured in HADES W. Koenig, Jerzy Pietraszko, T. Galatyuk, V. Pechenov, J. Markert, J. Stroth,...

J.Pietraszko, HADES Coll. Meeting, GSI Nov , Beginning in 2010 Three beam times in 2010: Huge in-spill currents measured in the inner MDC systems. Huge "noise" in the inner MDCs seen online on the scope and in the data.

J.Pietraszko, HADES Coll. Meeting, GSI Nov , Investigations in 2010 Trying to understand the MDC data: Clearly visible structures in the MDC T1 distributions Wire distributions "pointing" to the Veto region

J.Pietraszko, HADES Coll. Meeting, GSI Nov , Short history starting in 2010 MDC T1 perfectly correlated with Start Hits  atomic interactions Start T1 from MDC I T1 from MDC II T1 from MDC III T1 from MDC IV

J.Pietraszko, HADES Coll. Meeting, GSI Nov , Momentum distribution  -electrons seen in GEANT and modeled by W. Koenig

J.Pietraszko, HADES Coll. Meeting, GSI Nov ,  -electrons – simulation, emission from the Veto region shown in Seillac MDC I, sec 3 MDC II, sec 3 13 / event/sec 8 / event/sec and the Veto shielding.... Material:C 2 H 2 Cl Density:1.44 g/cm 3 Thickness:5 mm Installed before Aug 2011 With Veto shielding: MDC I: / event MDC II: / event

J.Pietraszko, HADES Coll. Meeting, GSI Nov ,  -electrons identification Start detector sees all bam particles. T>100 ns  min. bias data Start T1 from MDC I T1 from MDC II T1 from MDC III T1 from MDC IV HADES Trigger 60 ns Min. bias data (2 % - nuclear inter. prob.) Procedure: 1. count number of start hits for T> 200ns, 2. count number of wires in MDCI and MDC II for T>200 ns

J.Pietraszko, HADES Coll. Meeting, GSI Nov ,  -electrons identification Comparison of data from Nov2010 with Aug2011 Nov2010Aug2011 Number of MDC wires / Start Hit  Veto shielding reduces significantly  -electron yield MDCI Nov2010 (w/o Veto shielding) about 50 wires/St hit/sec !!!!  8 particles/ sector (5 in MDC II) MDCI Aug2011 (with Veto shielding) about 18 wires/St hit/sec !!!!  2.9 particles/ sector (1.6 in MDC II) expected: / event

J.Pietraszko, HADES Coll. Meeting, GSI Nov ,  -electrons identification Veto shielding - remaining  -electrons Aug2011 MDCI Aug2011 (w/o Veto shielding) about 18 wires/St hit/sec !!!!  2.9 particles/ sector (1.6 in MDC II) expected: / event Vertex reconstruction real reaction for  -electrons T>200ns  Pointing to Veto region !!!!

J.Pietraszko, HADES Coll. Meeting, GSI Nov ,  -electrons identification Comparison of "empty/full target" Aug2011  remaining particle yield come from the Au target MDCI Nov2010 (Empty target) 30 % empty events 70 % about 5 wires/St hit/sec !!!!  0.9 particles/ sector (similar in MDC II) MDCI Aug2011 (with Veto shielding) about 18 wires/St hit/sec !!!!  2.9 particles/ sector (1.6 in MDC II) expected: / event "Empty" Target"Full" Target Number of MDC wires / Start Hit 0 or 1 wire – 5% 0-3 wires – 30%

J.Pietraszko, HADES Coll. Meeting, GSI Nov , Additional shielding Rough estimation based on theta distribution in MDC I and MDC II Lengths and thickness of the shielding – to be settled – simulation ! 70% Start - Halo 70%

J.Pietraszko, HADES Coll. Meeting, GSI Nov , Summary TDCs with Multi-hit capability opens new options in the detector performance studies Significant amount of  -electrons in HADES acceptance MDCI and MDC II suffer Additional shielding feasible, in acceptance !!!, dedicated simulation essential MDC load estimation: 6 particles / sector - 2 % of events (beam particles – nuclear interaction ) 2.9 particles / sector - 98 % of events (beam particles) for 100 beam Au ions: - 6 (particles) * 2 = 12 particles / sector (nuclear interaction) (particles) * 98 = 284 particles / sector (  -electrons)  ratio is about 23  current in MDC I mainly from  -electrons Positive side of the  -electrons in HADES (not exploited): Excellent beam monitoring tool (strong effect visible when Au ion goes thorough the Au target)

J.Pietraszko, HADES Coll. Meeting, GSI Nov , backup slides

J.Pietraszko, HADES Coll. Meeting, GSI Nov ,  -electrons. Does the RICH radiator help? Vertex reconstruction for hits coming from d-electrons for file collected with the Rich radiator and without. T>200ns   -electrons, cut on MDC ToT > 25ns (cal) with CF10 RICH radiator without CF10 RICH radiator

J.Pietraszko, HADES Coll. Meeting, GSI Nov , HADES Start-Veto system (Au+Au) Detector properties: Low material budget (low interaction probability), good time resolution (below 50 ps) In vacuum operation, located directly in front of the target in order to reduce load on the RICH  Start det.: monocrystalline diamond, 50  m thickness, 4.7mm x 4.7mm  Veto det.: polycrystalline diamond, 100  m thickness, behind the RICH Detector. Start - Halo 4,7 mm 15 gold targets (Ø 2.2 mm) Start detector mm

J.Pietraszko, HADES Coll. Meeting, GSI Nov , Start-Veto system – test with Au beam (Nov 2010) Setup and conditions: Start det.: monocrystalline diamond, 50  m thickness, HV set to 200 V Veto det.: polycrystalline diamond, 100  m thickness, HV set to 200 V. Beam particles intensity: 10 6 /s per channel. St ch1 43 ps St ch2 37 ps St ch3 40 ps St ch4 37 ps St ch5St ch6 St ch7 St ch8HPTDC resolution Start detector, scCVD Start detector counts Veto detector, reference detector mm