Transcript Study of response uniformity of LHCb ECAL

Study of response
uniformity of LHCb
ECAL
Mikhail Prokudin, ITEP
Outline
► Motivation
► Geometry
of modules
► Experimental setup
► Procedure
► MC modeling
► Results
 light yield
► Conclusion
Motivation
►
“Shashlik” technology
 cheap
 fast enough
►
trigger
 radiation hard
 easy to segment
►
Resolution
dE
a

b
E
E
 a – stochastic term ~8%/sqrt(E)
 b – constant term
RD36 data
► stochastic
term
 decrease thickness of
absorber
► increased
volume ratio
 increased Morier radius
► more shower overlaps
► keep
volume ratio constant
 photostatistics
► constant
term
 increase the volume ratio
 technology
7%
► die-mold
price ~10k $
► MC model of light
propagation in scintillator
tile
Modules geometry
► LHCb
► inner:
4x4cm2 cells
► middle: 6x6cm2 cells
► outer: 12x12cm2 cells
 67x4mm layers of
scintillator
 66x2mm layers of lead
► Prototype
 4x4cm2 cells
 280x0.5mm layers of
scintillator
 280x0.5mm layers of lead
Experimental setup
old chambers
new chamber
Beam
e, μ
Beam plug
Calorimeter
25.111m
LED monitoring
system scheme
10.97m
2.935
Calorimeter assembly
LED2
8 modules (12x12cm2x1) for leakage control
PIN
LED1
testing module
Coordinate determination
► Beam
size: 3x3cm2
► Energy cut: 60-65%
MPV position
► Details of calorimeter
construction are visible
Muons
Shifts corrected for each position
Same procedure for electrons
Muons. Procedure
► energy
only in central
cell
► 1x1 mm2 regions
► fit with Landau
distribution
 first fit to estimate
ranges
 second fit with
► f(xstart)=0.4*Max
► f(xend)=0.05*Max
 no Landau Gauss
convolution
► much
more statistics
Electrons. procedure
► Collect
energy in
3x3+4 cells
 wider signals with if
other 4 cells included
► 1x1
mm2 regions
► Iterative fit procedure
 [-1.2δ, +2δ] region
MC modeling
► Signal
nonuniformity
 Light collection nonuniformity
►Special
ray tracer program
 Scintillator tile thickness variations
►Measured
directly
 Convolution with particle energy deposition
 “natural” smearing
 energy deposition nonuniformity
 dead material
►GEANT
Ray tracer program
►
Optics
►
 refraction
► Fresnel
formulas
 reflection
► mirror
► diffuse
 attenuation
► in
medium
► on surface
 all processes could depend
on wavelength
►
Geometry
 geometrical primitives
► cylinder
► box
 Boolean operations
 voxelization
Main optical parameters
 quality of scintillator surface
 whiteness of paint
 size of “edging”
Example of ray tracer test
► Edge
effect in light
collection
 compensate dead
material between
tiles
 not trivial
 LHCb innovation
LHCb inner module
Muons
Electrons
Scale!
LHCb inner module.
Muons
Electrons
Between fibers
Between fibers
Near fibers
Near fibers
Gray – MC. Black – data. Scale!
Prototype module
Prototype. 0.5мм
LHCb. 4мм
Scale!
Prototype module and inner LHCb
module
Prototype
LHCb inner
Between fibers
Near fibers
Gray – MC. Black – data. Scale!
Between fibers
Near fibers
LHCb outer module
► 12x12cm2
Between fibers
► Distance
between
fibers 15mm
 10mm in inner
module
► Only
2 delay wire
chambers
Near fibers
 worse position
resolution
► One
set of optical
parameters to
describe all data!
Gray – MC. Black – data.
Light yield
Experiment
► Use monitoring
system
MC
► Generate photons
uniformly inside tile
volume
► Inner module for
normalization
Cosmic
Testbeam
setup
MC
inner
3000
3100
3000
middle
3600
3500
3600
outer
2500
2600
2570
prototype
700
-
600
Conclusions
► Measurements
of
uniformity of LHCb
calorimeter response
presented
 different probes
► electrons
► muons
 different modules
► inner
► outer
► prototype
 absorber and scintillator
thickness 0.5mm
► Calorimeter
response
uniformity modeled
 thickness measurements
 light collection
► ray
tracer code developed
► tile model created
 Geant
► dead
material simulation
► Model
parameters
extracted
 and checked for various
geometries
Coordinate determination
► Modify
coefficients
 residuals
► keep
mean at 0
► narrow
► Cut χ2<4
 denominator from
“Delay wire
chambers...” by
J.Spanggaard.
Lacing
Ray tracer testing
► Visualize
trajectories
 individual
photons
 using ROOT for
drawing
Geant model
►
►
Geant3
Gorynych framework
White paint,
0.15 mm
 for ITEP FLINT
experiment
►
Tile model with holes
and fibers
 same as for raytracing
►
67x4mm scintillator
layers
 66x2mm layers of
lead
►
Dead material
 steel tape, 0.2mm
thick
 white paint, 0.15mm
at edge of tile
Steel tape, 0.2 mm
Fiber in
each hole