Studies of the ATLAS Tile Hadron Calorimeter Performance. Ilya Korolkov (IFAE) presented by Stanislav Němeček (FZU). Outline Tile Hadron Calorimeter ( TileCal ) Performance Detector Geometry Working Environment Dynamic Range R&D History of the TileCal ’94, ’96 Performance for Pions
Ilya Korolkov (IFAE)
Stanislav Němeček (FZU)
5.6 degree azimuthal slice
The TileCal, the barrel part
of the hadron calorimeter
in ATLAS, is a sampling
device made of steel and
scintillating tiles. Due to
the LAR EM-calorimeter in
front mainly the hadronic
response is optimized. Some
sensitivity to muons is used
in the level-1 trigger.
cracks at transition region
Intermediate Tile Calorimeter + Gap Scintillators
Each 0.1 azimuthal slice has 73 cells
arranged into projective towers with0.1.
Each of 64X3 modules has three depth
segmentations called samples A, B, and D.
18 mm period in z with radial tiles staggered in depth.
local variations in sampling fraction for ||<0.1
to contain jets and to shield muon system.
Energy deposition per BXing (MC) for a
typical cell (A1) in the innermost sample
Mean energy 9MeV
desired dynamic range from fraction of GeV to 2TeV (had) per cell
L=(210 –10 ) cm s
pile up -> on average (5-23) min bias events per BXing
improved understanding of expected min bias signals in TileCal
on average 30% less energy than it was expected in ’96
optimal filtering algorithm is well advanced
applying to ’98 TB data -> reduction in noise RMS by 30%
intension to use MB currents to monitor TileCal stability
TB data with 25nsec beam structure (’01),
timing everywhere in the module better than 1nsec
which includes beam spread. For ATLAS timing ~0.5 nsec
compatible to the bunch size.
Tiles and fibers are expected to loose less then 5% of the
light yield under 40kRad (10yeas of ATLAS) (’94-’96).
This loss to be monitored with Cs during ATLAS shut-downs.
Natural ageing of optics estimated to be at the same level.
Dedicated QC of all the electronics components
Npe/GeV improves over the years
due to the instrumentation experience.
Current plan is to set PMT gains to
1.2pC/GeV of em energy at 90 degrees.
This will require setting HVs down by
(10-40)V from the nominal values ->
non-linearity from PMTs rises up to 2%.
Non-linearity can be recovered by
LAS calibration or by weighting technique (less likely)
Dynamic Range = 1.52GeV/cell (had scale)
Proposal to enhance the dynamic
range by recovering saturation.
’93 first prototype
’94 combined with ’97 ExtB M0 full
LAR prototypes size prototype
’95 five 1m prototypes ’98 Barrel Mod0
’96 Barrel Mod0 full size reinstrumented
prototype combined’99 Barrel Mod0
with LAR and standalone
’00 one production Barrel and two ExtB modules.
’01 one Barrel and two ExtB production modules
with final electronics, start of calibration
Two combined TBs with LAR
’94 – five 1m prototypes
’96 – +full size barrel Mod0
since than no combined TBs
(after weighting )
Average Energy loss for evts
with longitudinal leakage
(after weighting )
’94 – within 1%
’96 – within 2%
Sampling ‘a’ and constant ‘b’ terms of the electron energy
resolution (’01) compared to those of the prototype Mod0.
Two production EB modules (’01)
Uniformity of (pC/GeV) in is within few %
Leakage in the transverse
direction had not been
controlled -> resolution
looks larger than it is.
Two production EB modules (’01)
The pion Energy is calculated using:
e – em calibration const
Rπ - measured signal
e/h = (1.36 ± 0.01),
Measured on Mod0
fπ = 0.11*ln(Ebeam)
Jets in-situ calibration
To correct for detector effects
non-linearity from non-compensation, longitudinal leakage, pmts,
energy lost in the dead material, (3-13)% depending on ,
noise from min bias and electronics, magnetic field effects, finite granularity
depending on physics goals may go deeper into fragmentation, IRS, FRS …
Weighting Techniques (H1), Energy flow method (using tracker information)
E/Pt for a single hadron (usually coming from )
with 10fb of data (320k signal evts)
may reach .6% level in jet E calibration.
Z/+jet Pt balance
with 10fb of data may reach 1% level
in jet E calibration and 1% linearity.
with 10fb of data may reach 2% level
in jet E calibration and 2% linearity.
limited statistics and HUGE number of weights (usually both Energy and dependent)
analysis usually assumes no tails in Energy measurements.
Requirements from the detector:
(5-10)% accuracy on EM scale after transporting TB calibration to the ATLAS, stability.
TB -> ATLAS calibration
What do we want? Accuracy, Stability, Uniformity, Simplicity.
All the modules to undergo Cs scans with the final electronics:
Final QC and repairs
Cs constants are produced
HVs (gains) are set to 1.2pC/GeV of em energy at 90 degrees.
except for the D sample (+20% gains to improve trigger)
minor impact on had trigger: 0.6% overestimation of tot had energy
and ITCs for which expected signals are smaller (-> +20%)
Target: gain setting to a better than 1% level.
8Barrels+8EBAs+8EBCs (12% of total) to be calibrated with the TB:
electron constants (pC/GeV) for every reachable TR-segment, cell.
muon constants (MOP, truncated mean) for every TR-segment, cell.
e/h, uniformity, improve Cs-data correlation …
TB constants to be transported to the cells (modules) not exposed to
the beam using Cs constants:
const = const x
After the gains
are set by Cs
cell to cell
by muons is
Example of the accuracy of the
Muon constants transportation
From one EB module to other two (’01)
Simulation of the
MB current from
one of the cells
During the data-taking
actually, during the empty bunches
not to interfere with the data flow
Monitoring of the Min Bias currents
Unique opportunity to have on-line diagnostic of the beam
(from inside of TileCal) and the optics inside of the cells.
It’s been shown that depending on the cell position 5-500
measurements are enough to reach 1% level of accuracy.
It uses “slow” electronics (RC~10msec) of the Cs system ->
Challenge is to use “fast” triggers from the empty bunches
to perform few switches which otherwise may affect data.
Laser system (LAS)
to monitor PMT block optics and PMT gains
Charge Injection System (CIS)
to monitor behavior of each read-out channel over its full
to monitor (and recalibrate if needed) optics inside of the cells
on the deep level of individual tiles, fibers and couplings.
One Barrel and two EB modules will be kept at TB area
to monitor ageing and to be the “spares” if needed.
An example of the CIS data (’01)
Injected pulse on the top
Leakage pedestals (effect of
the switches) on the bottom.
The detector geometry and principles of the TileCal were optimized for the best hadronic performance in a combined operation with other ATLAS calorimeters.
An extensive check of the stand-alone and combined performance was carried out during period from ’93 to ’99 on a set of prototypes mostly at the H8 test beam at CERN. The latest full size prototypes, called Mod0, complied to all the requirements set for the TileCal.
The research efforts since than were concentrated on calibration of the production modules which started in ’01. From all the data collected during TBs ’00-’01 we conclude that the performance of the production modules is at the same level or better than the performance of Mod0 full size prototypes.
Special efforts are applied toward future integration of the TileCal in ATLAS such as transportation of the calibration constants to the ATLAS environment and developing various monitoring systems.