aliceTofFestivalAdC201008

ALICE TOF FESTIVAL
CERN – Bdg.29, October 20th 2008
Offline tools and GRID scenario for the ALICE TOF detector
A. De Caro
(University of Salerno and INFN)
ALICE TOF Offline Group activities
ALICE software, AliROOT:
 the detector geometry (materials and geometrical distributions);
 the real MRPC features (e, st and time-over-threshold);
 the cluster finder;
 the reconstruction algorithm (matching);
 the particle identification (PID);
 the alignment procedure;
 the calibration (time slewing corrections and cable delays);
 the optimization of the ‘online’ - ‘offline’ connections (databases);
 event display.
A lot has been already done…
…but still a lot remains to do.
Nevertheless we are in good shape.
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Outline
 TOF geometry: simulation details
 TOF MRPCs: simulation of the test beam
results
 TOF clustering: new algorithm implementation
 TOF particle identification
 First cosmic m through tracking detectors
matched with TOF detector
 First alignment studies
 Some of the ALICE TOF Offline Group
successes
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Materials, shapes and their geometrical distributions in
the ALICE reference frame
April 24th 2008: all 18 TOF supermodules installed
SM4
SM5
SM3
SM2
SM6
SM1
SM7
SM8
SM0
SM9
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SM17
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TOF SMs as described in the AliROOT framework
SM5
SM4
SM3
SM2
SM6
SM1
SM7
SM8
SM0
SM9
SM17
SM10
SM11
SM12
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SM16
SM15
SM13
SM14
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TOF SM: services detail
real
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simulation
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TOF SM: front-end electronics detail
real
simulation
Finger to cool NINO ASIC
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Description of the real MRPC features:
detection efficiency
(time resolution and time-over-threshold)
as a function of the hit pad position
TOF MRPC strip: hit and activated pads
X
Z
Pad hit
by a particle
Y
Pads possibly
activated by
electrical induction
effects
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TOF MRPC strip: detection efficiency
3 1 5
4 2 6
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TOF MRPC strip: detection efficiency
3 1 5
4 2 6
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TOF MRPC strip: detection efficiency
3 1 5
4 2 6
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TOF MRPC strip: detection efficiency
3 1 5
4 2 6
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TOF MRPC strip: detection efficiency
3 1 5
4 2 6
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TOF MRPC strip: detection efficiency
3 1 5
4 2 6
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TOF MRPC strip: detection efficiency
3 1 5
4 2 6
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Standard clustering algorithm: one cluster per each fired pad.
New clustering algorithm: one cluster per each set of neighbouring fired
pads with comparable time measurements
(according to the time resolution).
Cluster time:
currently, the time weighted average (per tot);
with calibration parameters, better estimation (NIM A532, 611-621, 2004).
Similar remarks for the cluster position.
TOF multi hit associated to the same particle
con segnale
fired
not fired
senza
segnale
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Comparison between the two clustering algorithms
In blue: standard TOF cluster
In red: new TOF cluster
In green: TOF pad interested by signal
In yellow: standard TOF cluster fit
In violet: new TOF cluster fit
TOF strip in test
TOF strips as tracking detectors
D. De Gruttola, Phd thesis, Salerno May 9th 2008
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Comparison between the two clustering algorithms
In blue: standard TOF cluster
In red: new TOF cluster
In green: TOF pad interested by signal
In yellow: standard TOF cluster fit
In violet: new TOF cluster fit
Detail on the pad interested by signal,
7th strip, the one in test.
The violet line crosses the strip in test
while the yellow one does not.
The chosen order parameter is the distance
between the impact point
of the reconstructed track to the hit pad centre.
This order parameter is minimum
in case of new TOF cluster fit.
D. De Gruttola, Phd thesis, Salerno May 9th 2008
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ALICE TOF detector performances:
reconstructed mass vs momentum
and PID efficiency and contamination
in p-p and central Pb-Pb collisions
Mass vs momentum (PPR 2nd vol.)
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TOF PID efficiency and contamination (PPR 2nd vol.)
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Some results obtained with the analysis of the data
taken during the cosmic runs (12/07-09/08)
with/without L3 magnetic field.
Good chance to test the code with real data.
Cosmic muon reconstructed in ALICE detector (B=0 T)
TPC clusters
TRD clusters
TOF clusters
Reconstructed track
t1<t2
t1
Muon direction
t2
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Prospective view
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Cosmic muon reconstructed in ALICE detector (B=0.5 T)
t1<t2
Muon direction
t1
t2
m-
B = - |B| k
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Prospective view
m-
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To check the functionalities of the alignment algorithm
with real events
Distance-approach (r-z view)
 First alignment step for the
TOF detector: along the
beam direction, i.e. the z axis.
 Distance-approach: the
distance between the impact
point of the reconstructed
track on the TOF strip and
the closer TOF cluster centre
(schematically shown here).
r=371 cm
 The z component of the
distance-approach is the
parameter used to align TOF
SMs along z axis.
Reconstructed track
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Distance-approach distributions (B=0 T)
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Distance-approach distributions (B=0 T):
aligned geometry
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Distance-approach vs strip per TOF SM (B=0 T)
TPC: field cage internal wall
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Distance-approach vs strip per TOF SM (B=0.5 T)
TPC: field cage internal wall
Caused by
a not corrected calibration
for the drift velocity
(TPC people confirmed).
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Several successes obtained by the TOF Offline Group.
Some of them publicly acknowledged by the ALICE
Offline Group (green light for the TOF detector)
F.Carminati @ May 2007 Technical Board
Written code / code to be written [%]
http://indico.cern.ch/materialDisplay.py?contribId=14&materialId=slides&confId=7361
81.5%
Average
T
O
F
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Shuttle algorithm: online <-> offline
http://aliceinfo.cern.ch/Offline/Activities/Shuttle.html
Responsible: C. Zampolli
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Raw data implementation status
http://aliceinfo.cern.ch/Offline/Activities/Raw-Data.html
TOF
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CERN-Bdg.29, October 20th 2008
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