News from May Cosmics GCJacques & Yasmine 16 mai 2008
Selection of Yasmin transparencies • For the full story consult • http://indico.cern.ch/conferenceDisplay.py?confId=34031
Plan for the discussion « It’s all about timing » Yasmine has a plane to take @ 18h50 :-) • 1Zone by zone analysis needs brainstorming • 2Efficiency of the selection We have an explanation • 3High multiplicity events Irina suggests in her mail a way of understanding this.
data • Run 22476 from GC May 08. • We started to worry because: • We noticed that the rms of the asymmetry Was worse then what we had in the previous run (10/04/08). • We made the same plots as usual ref: mail from Jacques Jeudi 8 mai only we seperate them for each zone of the ECAL and the HCAL see slide .
Up to now the HCAL • 2 noisy cells in HCAL =>worsen timing => to be removed • The behaviour of the HCAL seems fine: 1We have roughly the same number of events in the Current/Next or Current/Prev. 2 the difference of the statistics between the Outer and the inner zone is consistent with the geometry of both regions.
Up to now ECAL ouch! • The middle ECAL seems fine. • The outer ECAL is strange we see only 25 Current/Next events for 600 events in the Current/Prev! • The amount of selected events in the inner ECAL is really small 8 Current/Next events and 0 Current/Prev events!!!
Old remaining pbs! • We go back to the run of march A side 20876 • We start with 13686 and we end up with 663 for the coincidence the efficiency of the whole selection is 4.8 % while from the trigger side we know that we should have 95% good cosmics. Question: Where do we loose them?
What we do in detail For each cell: ADC(P)+ADC(C) > 150 or ADC(C)+ADC(N) > 150 for the ECAL (resp 20 HCAL) For each Event : Condition2: Hits >1 Condition3: |R|<0.8 We always have two sets of events, events which appear in the Current/Next or Current/Prev. Note: In the following the conditions 1,2,3 will be Refered as C1, C2,C3. Condition 1
Selection in detailRun 14 Mars • HCAL • Current/Prev: • After C1 : 5965 • After C2: 5084 • After C3: 3259 • Current/Next: • After C1: 6828 • After C2: 5105 • After C3: 148 • ECAL • Current/Prev • After C1: 4524 • After C2: 3796 • After C3: 968 • Current/Next: • After C1: 7286 • After C2: 6420 • After C3: 27 • Note: Within in ECAL events 32 are not usuable # of hits>60.
So • For the Current/Prev Events we loose a lot !This is explained by the fact that in this run we had a +7 ns offset computed from the fit. • For the Current/Next Event we loose almost everything because of the extra L0DU delay that we had in this run! In the analysis we looked at Prev1/Current/Next1 but really the cosmics were in Prev2/Prev1/Current! • To validate these hypothesis, we should look at the selection efficiency for a run where the offsets in the TTCRx were corrected and where we have no pb with the L0DUNext slide
10 April Run C side But the offsetin the TTCRxwere corrected • ECAL • Current/Next • After C1:5752 • After C2: 4921 • After C3:2955 • Current/Prev • After C1: 4985 • After C2: 4467 • After C3: 2888 • HCAL • Current/Prev • After C1: 5808 • After C2:5097 • After C3:3375 • Current/Next • After C1 : 4636 • After C2: 3911 • After C3: 2918 Conclusion for part 2: We Start with 10893 Events out of which 2907 were used for the coincidence study We have 28% of efficiency which sounds reasonable!
Either a super nova? but most probably something that we need to understand! We saw this previously in March. Event 588 Run 22476
Summary of events with mutiplicity > 60 • 9 events in total. • 8 are always in the same Y region according to Irina these events might be actually LED Events. • 1 Event doesn’t belong to this region see event display in the following slide.
Event 21408 Ecal Prs Hcal Bremsstralhung?? From Olivier
Conclusion of Friday • Difference between outer middle inner ECAL could be crate timing problem? Or tell1 problem? Look at -2 events (when Yasmin back) • The big flare event could be unvolontary LED (some pin diode signal) but why not all cells (16/LED). How can all LED triggers when LEDTSB cycles by groups of LED • Efficiency when timed is OK => program for other users