SSD status report Marek Chojnacki, Panos Christakoglou, Enrico Fragiacomo, Marco Van Leeuwen, Massimo Venaruzzo - Offline week, CERN

Outline  News about the cluster finder and the tracker  Noisy/dead channels  Treatment of the dead (half) modules in the cluster finder  Treatment of dead zones (two-sided) in the tracker  Calibration  Online issues – DA  Offline procedure – Results  QA online/offline - Offline week, CERN

Bad channels/modules  Dead/Noisy channels  We have one static list of bad channels based on the offline analysis of noise runs.  This file is updated after every calibration run from our DA and is stored in the OCDB.  Noisy channels: Noise after CM correction > 17 ADC  2.5%  Dead channels: Noise before CM correction < 1 ADC  coming from switched off half-ladders  Open channels: Noise after CM correction > noise before the CM correction  0.4%  High pedestal: |pedestal| > 512 ADC  <<0.1%  In total we have ~3% of noisy SSD channels 50% percent of which are located at the borders of the module (first 10 strips)  “Dead” modules:  SSD modules that are manually switched off from the data acquisition (high current half-ladders etc. – being addressed by our hardware experts) Massimo Venaruzzo - Offline week, CERN

Bad channels on the border: effect on the φ distribution  Use AliGenBox with high momenta protons (50 GeV/c) at η=0 and 250°<φ<290°  Compare simulation with real setup and ITS-ideal setup (got ideal setup for SPD and SDD from the experts)  Holes at 260° and 280° due to TPC (every 20°)  Ladders (both on lay5 and lay6) are at Φ=270°, 260°, 280°, …  Expect something at ~265°, ~275°, 285°!?  Only at ~275° something?!  Apparently no effect! SSD modules ?? IDEAL REAL RATIO REAL/IDEAL Fit pol0 Bad channels on the border are in the ladder overlap region: try to see the effect on phi distribution Enrico Fragiacomo Offline week, CERN

“Half-dead” modules  A modified version of the cluster finder has been prepared which creates recpoints from 1Dclusters  All Nsides have been tagged as bad in the OCDB  No P-N matching is done since it is not needed  Had to introduce covariance matrix for the recpoint (see next slide)  The same strategy will be applied in the case of single bad channels on one side (not entire side).  To do: check efficiency vs. purity Enrico Fragiacomo Andrea Dainese Motivation: What to do in the case of a dead single side?  Use 1D clusters? A cluster is formed from the combination of an 1D p and n-side cluster. A local simulation study was launched that could help to decide whether the poor information from the good side is better than nothing. - Offline week, CERN

Covariance matrices  So far only sigmaz2 and sigmay2 passed to the recpoint constructor  Had to define Σ=RDR T where D is the diagonal matrix in the strip coordinate system and R is the strip_to_localyz transformation  AliITSRecPoint.cxx (constructor) modified to define the out- of-diagonal element of the covariance matrix  Method SetSigmaYZ() added to AliCluster.h  Two cases (A and C are different):  “Standard” recpoint from a PN matching  Recpoint from P- or N-side 1Dcluster (as for half-dead modules in previous slide)  Also a difference on layer5 and layer6 - Offline week, CERN Enrico Fragiacomo

Dead strips/zones in the tracking  Simultaneous dead strips on both sides  Started implementation  Simplest algorithm: count bad strips inside search road on P and N side, flag as dead if both >= 1.  However: current search road very large, so a “dead area” is easy to be found with this prescription. Motivation: allow tracker to skip layer when no cluster is found and there are dead areas - Offline week, CERN Marco van Leeuwen Search road A=7.5, B=4 2 (fudge factors)  30σ! Large probability to find some dead strips in this area No sensible definition of dead area in search road Propose to allow to skip SSD (ITS) layer in tracking if no clusters are found (or redefine search road for dead strip detection)

Calibration: Charge matching performance Golden Cut |Cr|<0.2  All modules used the same calibration.  A more accurate calibration should reduce a noise by  Found one module with a discrepancy in the gain factors  Manually change the corresponding entries for the gain file  OCDB Marek Chojnacki Offline week, CERN

Calibration: Energy loss plot Muon MPV according to : pdg.lbl.gov, D.E Groom, N.V Mokhov, S.I Striganov ``Muon stopping-power and range tables: 10MeV-100TeV `` Atomic Data Tables 78, (2001), H.Bichsel, Rev. Mod. Phys. 60, 663 (1988)‏ Cosmic runs with field, tracks with ITSsignal>0.0 and kITSrefit+kTPCrefit. ITSsignal calculated using only SSD information Marek Chojnacki Offline week, CERN

QA (online/offline)  Current implementation of the automatic checks  So far only trivial checks were performed in the checker.  We need to define different reference data for thefollowing run types:  Calibration-Noise  Cosmics  Low multiplicity  High multiplicity.  Ref. data for the SSD are practically defined.  In contact with the rest of the ITS QA experts in order todefine a common QAref object for each run type (since thethree sub-detectors are considered as one detector fromthe QA point of view). - Offline week, CERN10

Backup slides - Offline week, CERN

“Bad”: present definition  Noisy strips: Noise after CM correction > 17 ADC ch  Dead strips: Noise before CM correction < 1 ADC ch  Pedestal outside of correction range: Pedestal > 512 or < -512 ADC ch  Open Channels: Noise after CM correction > Noise before CM correction  selecting events with CM > 2.5 ADC units  excluding dead (noise not CM corrected 2.5 ADC units) strips  “+ 0.5” in order to avoid statistical fluctuations  in OR withNoise after CM correction/Noise before CM correction > 1.5  excluding dead (noise not CM corrected 4 ADC units) strips - Offline week, CERN

What does mean “first” or “last”? - 1 First PLast P First N Last N - Offline week, CERN

What does mean “first” or “last”? - 2 First NLast N First P Last P - Offline week, CERN