Study of response uniformity of LHCb ECAL
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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