Understanding the Performance of CMS Calorimeter

LCWS06@IISc CMS Calorimeter 1

Understanding the Performance of CMS Calorimeter

Seema Sharma,TIFR

(On behalf of CMS HCAL)


CMS Calorimeter

HCAL :

Scintillator-Brass Sampling Calorimeter

2-3 longitudinal samplings from 17-19 layers of Scnt.

ECAL:

PbWO4 Crystal

Homogeneous Calorimeter of ~26 Χ0


TB2004 Setup

2 wedges of HCal Barrel2 slices of HCal endcap6-trays of HO for 3 ringsMock-up of CMS magnetTail catcher iron7 X 7 ECal crystal matrixMock-up of material between ECal and HCalBeam line trigger counters


HCAL on a Table

HB

HE

HO

ECAL

pivot

beam

Pivot of table = IP at LHC

A phi slice of CMS HCAL


ECAL Module


Hadron Calorimeter

HO

VM

HB1

HB2


Readout Configuration


Beam Line Counters

WC-AWC-B

WC-C

S1

S4 S3S2


80 GeV/c

SCI_VLE

CK2

CK3

WC A,B,C

HCAL

HCALECAL

ECAL

V3,V6

VM

P-ID: CK2- electron CK3- pion / kaon / proton V3, V6, VM – muon

VLE tag against punchthrough muon

WC single hit to reject interaction in beam line

Beam Line at H2


Data Sets


• Done using Co60 source at the tip of a stainless steel wire.• With the source at η boundaries, adjacent tiles receive some signal.• Contributions from adjacent tiles are added.

Source Calibration

Source position


• Calibration constant corresponds to a least square fit across the tile.• An iterative procedure is followed to get final calibration constants.

Source Calibration (continued…)

Source position


Fit the pedestal distribution with a Gaussian.

Fit muon signal with a convolution of Landau and Gaussian distributions.

Float the relative contribution of the pedestal.

The peak of the fitted LandauGauss function is used as the calibration constant.

Calibration with Muons at 150 GeV


Correlation Between Source and Muon Calibration

• A straight line fit through all the points gives χ2/ndf of 18.• Some correlation is observed between the calibration constants obtained using the two methods.


300 GeV 150 GeV

100 GeV 30 GeV

HB

ECAL ECAL

HB

e-

Energy Measurement


Comparison with GEANT4 Simulation (LHEP)


Energy Measurements at Low Energies


LHEP without scintillation saturation effect (Birks’ law) shows a reasonable agreement with data for EC+HB combined system.

Need more beam clean up and better understanding of systematic errors before making more definitive conclusion, especially HB alone data, (not shown today) …proton

pions

π/e Response


Energy Resolution

0.92 GeV measured

Larger noise

than HB1

(0.4GeV in 3x3)

because of

individual layer

readout in HB2.


Two G4 physics models show difference at high energy.

Event selection – MIP in ECAL.

Longitudinal Shower Profile


Summary

Test beam data were taken during 2004 with the final(?)

electronics modules. A large data set was collected with pions and electrons with

the energies in the range 3-300 GeV with proper particle

identification especially at low energies. Test beam results are compared with the GEANT4

simulations. LHEP physics list describes the data most

closely. Energy response and resolution obtained from various

physics lists match closely and only difference is seen in

longitudinal shower profiles at high energies. HCAL team plans to continue with testing the calorimeter

modules with improved VLE beam and better PID.

Understanding the Performance of CMS Calorimeter

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