Studies of the atlas tile hadron calorimeter performance
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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

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Studies of the ATLAS Tile Hadron Calorimeter Performance

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Studies of the atlas tile hadron calorimeter performance

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

    • ’01 Performance for Electrons

    • ’01 Performance for Pions

    • Calibration Strategy

    • Monitoring Program

  • Summary


Detector geometry

Detector Geometry.

y

z

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.

Hermeticity

coverage 1.7

cracks at transition region

Intermediate Tile Calorimeter + Gap Scintillators

Segmentation

Each 0.1 azimuthal slice has 73 cells

arranged into projective towers with0.1.

Each of 64X3 modules has three depth

segmentations called samples A, B, and D.

Sampling

18 mm period in z with radial tiles staggered in depth.

local variations in sampling fraction for ||<0.1

Material budget

to contain jets and to shield muon system.

η=1.7


Working environment

Working Environment.

Energy deposition per BXing (MC) for a

typical cell (A1) in the innermost sample

Occupancy 15%

Mean energy 9MeV

1/2

S =14TeV

desired dynamic range from fraction of GeV to 2TeV (had) per cell

L=(210 –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

BXing=25nsec

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.

Radiation Hardness

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

33

34

-2

-1

GeV

<4kRad/year

ID only


Dynamic range

Dynamic Range.

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.


Test beams history of the tilecal

Test Beams History of the TileCal.

‘94

‘97

’98-’99

‘96

’00-’01

’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


Hadron calorimeter performance for s

Hadron Calorimeter Performance for s.

’94

‘96

Two combined TBs with LAR

’94 – five 1m prototypes

’96 – +full size barrel Mod0

since than no combined TBs

were done.

Energy resolution

(after weighting )

Punch-through

probability fors

Average Energy loss for evts

with longitudinal leakage

Response linearity

(after weighting )

’94 – within 1%

’96 – within 2%


01 performance for electrons

’01 Performance for electrons.

 = 20

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 %

Resolution /E


01 performance for s

’01 Performance for s.

Leakage in the transverse

direction had not been

controlled -> resolution

looks larger than it is.

Resolution /E

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)

 scan

Longitudinal scan


Calibration strategy

Calibration Strategy.

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 …

Recovery methods:

Weighting Techniques (H1), Energy flow method (using tracker information)

Golden channels:

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.

t->W->jj

with 10fb of data may reach 2% level

in jet E calibration and 2% linearity.

Concerns

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.

MC


Calibration strategy cont d

Calibration Strategy (cont’d).

TB -> ATLAS calibration

What do we want? Accuracy, Stability, Uniformity, Simplicity.

Procedure:

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

variation in

gains seen

by muons is

1.8% (’01)

Cs

2

2

1

Cs

1

RMS=2%

Example of the accuracy of the

Muon constants transportation

From one EB module to other two (’01)


Monitoring program

Monitoring Program.

nA

Simulation of the

MB current from

one of the cells

100BXings

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

dynamic range.

During shut-downs

Cs scans

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.


Summary

Summary.

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.


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