Study of Study of response response

uniformity of uniformity of LHCb ECALLHCb ECAL

Mikhail Prokudin, ITEPMikhail Prokudin, ITEP

OutlineOutline

►MotivationMotivation►Geometry of modulesGeometry of modules►Experimental setupExperimental setup►ProcedureProcedure►MC modelingMC modeling►ResultsResults

light yieldlight yield►ConclusionConclusion

MotivationMotivation► ““Shashlik” technologyShashlik” technology

cheapcheap fast enoughfast enough

► triggertrigger radiation hardradiation hard easy to segmenteasy to segment

► ResolutionResolution

a – stochastic terma – stochastic term ~8%/sqrt(E)~8%/sqrt(E) b – constant termb – constant term

► stochasticstochastic termterm decrease thickness of decrease thickness of

absorberabsorber► increased volume ratioincreased volume ratio

increased Morier radiusincreased Morier radius► more shower overlapsmore shower overlaps

►keep volume ratiokeep volume ratio constantconstant photostatisticsphotostatistics

► constant termconstant term increase the volume ratioincrease the volume ratio technologytechnology

►die-mold price ~10k $die-mold price ~10k $►MC model of light MC model of light

propagation in scintillator propagation in scintillator tiletile

bE

a

E

dE

7%

RD36 data

Modules geometryModules geometry

► LHCbLHCb► inner: 4x4cminner: 4x4cm22 cells cells►middle: 6x6cmmiddle: 6x6cm22 cells cells►outer: 12x12cmouter: 12x12cm22 cells cells

6767xx44mm layers of mm layers of scintillatorscintillator

6666x2mmx2mm layers of leadlayers of lead

► PrototypePrototype 4x4cm4x4cm22 cells cells 280280x0.5mm layers of x0.5mm layers of

scintillatorscintillator 280280x0.5mm layers of x0.5mm layers of

leadlead

Experimental setupExperimental setup

Beame, μ

Beam plug

Calorimeter

25.111m 10.97m 2.935

new chamber

old chambers

Calorimeter assembly8 modules (12x12cm2x1) for leakage

control

testing module

LED1

LED2

PIN

LED monitoring system scheme

Coordinate determinationCoordinate determination► Beam size: 3x3cmBeam size: 3x3cm22

► Energy cut: 60-65% Energy cut: 60-65% MPV positionMPV position

►Details of Details of calorimeter calorimeter construction are construction are visiblevisible

Shifts corrected for each positionSame procedure for electrons

Muons

Muons. ProcedureMuons. Procedure

► energy only in energy only in central cellcentral cell

► 1x1 mm1x1 mm22 regions regions► fit with Landau fit with Landau

distributiondistribution first fit to estimate first fit to estimate

ranges ranges second fit withsecond fit with

► f(xf(xstartstart)=0.4*Max)=0.4*Max► f(xf(xendend)=0.05*Max)=0.05*Max

no Landau Gauss no Landau Gauss convolutionconvolution►much more statisticsmuch more statistics

Electrons. procedureElectrons. procedure

► Collect energy in Collect energy in 3x3+4 cells3x3+4 cells wider signals with if wider signals with if

other 4 cells other 4 cells includedincluded

► 1x1 mm1x1 mm22 regions regions► Iterative fit Iterative fit

procedureprocedure [-1.2[-1.2δδ, +2, +2δδ] region] region

MC modelingMC modeling

►Signal nonuniformitySignal nonuniformity Light collection nonuniformityLight collection nonuniformity

►Special ray tracer programSpecial ray tracer program

Scintillator tile thickness variationsScintillator tile thickness variations►Measured directlyMeasured directly

Convolution with particle energy Convolution with particle energy depositiondeposition

““natural” smearingnatural” smearing energy deposition nonuniformityenergy deposition nonuniformity dead materialdead material

►GEANTGEANT

Ray tracer programRay tracer program► OpticsOptics

refractionrefraction► Fresnel formulasFresnel formulas

reflectionreflection► mirrormirror► diffusediffuse

attenuationattenuation► in mediumin medium► on surfaceon surface

all processes could all processes could depend on wavelengthdepend on wavelength

► GeometryGeometry geometrical primitivesgeometrical primitives

► cylindercylinder► boxbox

Boolean operationsBoolean operations voxelizationvoxelization

► Main optical parametersMain optical parameters quality of scintillator surfacequality of scintillator surface whiteness of paintwhiteness of paint size of “edging”size of “edging”

Example of ray tracer testExample of ray tracer test

► Edge effect in Edge effect in light collectionlight collection compensate dead compensate dead

material between material between tilestiles

not trivialnot trivial LHCb innovationLHCb innovation

LHCb inner moduleLHCb inner module

Electrons Muons

Scale!

LHCb inner module.LHCb inner module.

Between fibers

Near fibers Near fibers

Between fibers

Electrons Muons

Gray – MC. Black – data. Scale!

Prototype modulePrototype module

Prototype. 0.5мм

LHCb. 4мм

Scale!

Prototype module and inner Prototype module and inner LHCb module LHCb module

Gray – MC. Black – data. Scale!

Between fibers

Near fibers

Between fibers

Near fibers

LHCb inner Prototype

LHCb outer moduleLHCb outer module► 12x12cm12x12cm22

►Distance between Distance between fibers 15mmfibers 15mm 10mm in inner 10mm in inner

modulemodule►Only 2 delay wire Only 2 delay wire

chamberschambers worse position worse position

resolutionresolution►One set of optical One set of optical

parameters to parameters to describe all data!describe all data!

Between fibers

Near fibers

Gray – MC. Black – data.

Light yieldLight yield

ExperimentExperiment► Use monitoring Use monitoring

system system

MCMC►Generate photons Generate photons

uniformly inside uniformly inside tile volumetile volume

► Inner module for Inner module for normalizationnormalization

TestbeaTestbeamm

Cosmic Cosmic setupsetup MCMC

innerinner 30003000 31003100 30003000

middlemiddle 36003600 35003500 36003600

outerouter 25002500 26002600 25702570

prototypprototypee

700700 -- 600600

ConclusionsConclusions

►Measurements of Measurements of uniformity of LHCb uniformity of LHCb calorimeter response calorimeter response presentedpresented different probesdifferent probes

►electronselectrons►muonsmuons

different modulesdifferent modules► innerinner►outerouter►prototypeprototype

absorber and absorber and scintillator thickness scintillator thickness 0.5mm0.5mm

► Calorimeter response Calorimeter response uniformity modeleduniformity modeled thickness thickness

measurementsmeasurements light collectionlight collection

► ray tracer code developedray tracer code developed► tile model createdtile model created

GeantGeant►dead material simulationdead material simulation

►Model parameters Model parameters extractedextracted and checked for various and checked for various

geometriesgeometries

Coordinate determinationCoordinate determination

►Modify coefficientsModify coefficients residualsresiduals

►keep mean at 0keep mean at 0►narrownarrow

► Cut Cut χχ22<4<4 denominator from denominator from

“Delay wire “Delay wire chambers...” by chambers...” by J.Spanggaard.J.Spanggaard.

LacingLacing

Ray tracer testingRay tracer testing► Visualize Visualize

trajectoriestrajectories individual individual

photonsphotons using ROOT using ROOT

for drawingfor drawing

Geant modelGeant model

► Geant3Geant3► Gorynych Gorynych

frameworkframework for ITEP FLINT for ITEP FLINT

experimentexperiment► Tile model with Tile model with

holes and fibersholes and fibers same as for ray-same as for ray-

tracingtracing► 67x4mm 67x4mm

scintillator layersscintillator layers 66x2mm layers of 66x2mm layers of

leadlead► Dead materialDead material

steel tape, 0.2mm steel tape, 0.2mm thickthick

white paint, 0.15mm white paint, 0.15mm at edge of tileat edge of tile

Steel tape, 0.2 mm

White paint, 0.15 mm

Fiber in each hole