ssd status report marek chojnacki, panos christakoglou, enrico fragiacomo, marco van leeuwen,...

SSD status report

Marek Chojnacki, Panos Christakoglou, Enrico Fragiacomo, Marco Van Leeuwen, Massimo

Venaruzzo

16.03.2009 [email protected] - 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


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


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

16.03.2009 [email protected] - 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 FragiacomoAndrea 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. Alocal simulation study was launched that could help to decide whether the poor information from the good side is better than nothing.


Covariance matrices

So far only sigmaz2 and sigmay2 passed to the recpoint constructor

Had to define Σ=RDRT 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


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


Marco van Leeuwen

22dettrackroad BA

Search road

A=7.5, B=42 (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 0.01.

Found one module with a discrepancy in the gain factors Manually change the corresponding entries for the gain file

OCDB Marek Chojnacki


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, 183-256 (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


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 the following 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 to define a common QAref object for each run type (since the three sub-detectors are considered as one detector from the QA point of view).

16.03.2009 [email protected] - Offline week, CERN 10

Backup slides


“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 + 0.5 selecting events with CM > 2.5 ADC units excluding dead (noise not CM corrected <1) & noisy (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 <1) & noisy (noise not

CM corrected > 4 ADC units) strips


What does mean “first” or “last”? - 1

First P

Last P

First N

Last N


What does mean “first” or “last”? - 2

First N

Last N

First P

Last P


ssd status report marek chojnacki, panos christakoglou, enrico fragiacomo, marco van leeuwen,...

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