Slajd 1

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Some results from LumiCal Monte Carlo
Studies
FCAL workshop October 17 2006 Munich
Michal Karbowiak () , B. Pawlik , L. Zawiejski
Institute of Nuclear Physics PAN, Cracow
() Diploma student from
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LumiCal simulation
the detector position
uncertainties
internal structure deformation

Estimate their possible influence on
luminosity measurements
Geometry (previous version in LDC) GEANT 3
(BARBIE) (stand-alone program)
LumiCal
26 - 82 mrad
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LumiCal Simulation - an example
BHLUMI
Guinea_Pig
Bhabha ee ? ee (n) ?
beamstrahlung
pairs e e-
Scattered electrons
LumiCal
emitted photons
IP
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The LumiCal positioning
Two different crossing angles were selected 0
and 20 mrad ( calorimeter along the main
detector axis or an outgoing pipe)
LumiCal
IP
?min
The shifts in perpendicular and longitudinal
directions
LumiCal
Approximation
?z 50 ?m steps for Z in range (-300, 300)
?m
? z
?? ?gen - ?rec
? (x,y)
Statistics for each point 50 000 Bhabha events
?X 50 ?m for (X,Y) in the range (0., 300)
?m
?L/L (?L/L ) the second order polynomial
20 mrad
0 mrad
20 mad
O mrad
?L/L (?L/L ) - linear fit
bias in ?? 10-5
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LumiCal changes in the internal structure
original structure
Internal structure
One disc structure
sensor
air
absorber
ceramic
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Deformations
Method
variation in position X,Y and Z of the
absorber and sensor layers
Deformed structure of the LumiCal was created
by smearing in Monte Carlo X, Y and Z
positions of the layers inside detector. They
were selected randomly according to Gaussian
distributions with average equal to the original
positions and different dispersions
original
Z
deformation in Z axis
Z
deformation in X i Y axes
Z
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Changes in Z position
Original
After change of the Z postions
The new layer positions - not allowed to cover
the neighbouring disc
Z1 Z1 id
?Zid Zn1 id - Zn id
Zn1 Zn ?Zid ZR
Zn1 - Zn lt 0. 59
ZR simulation from the
distorted type of Gaussian
distribution (? from 5 up to 45
?m)
Z1 , Zid - the position of the first disc
?Zid - the distance between discs
in ideal detector 0.59 cm
ZR - random selected z-position
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Changes in X, Y positions
MC simulation
Original
Xn Xid XR
Yn Yid YR
Xn , Yn - new discs positions
Deformed
Xid , Yid - discs positions
for ideal LumiCal
XR, YR simulation
XR, YR - random selected X
and Y positions
XR , YR were simulated according to
Gaussian distribution with ? which
was changed from 5 up to 45 ?m in 5
?m step
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Effect on relative luminosity measurements
The crossing angle 0 mrad
Change in structure along Z axis
Change in structure along (X, Y ) axis
The systematic effect on relative luminosity
measurements at least one order smaller
than from the shifts the whole Lumical
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Conclusions
Monte Carlo simulated events for two crossing
angles 0 and 20 mrad were used in
estimation effect on luminosity measurements from
the uncertainties in LumiCal
position measurements or from
deformation its internal structure The shift
of the detector up to 100 ?m in longitudinal
or transversal direction creates systematic
effect on relative luminosity measurement on the
level 10-4 . The effect from deformation of
the internal LumiCal structure is at least
one order smaller.