Luminosity and beam calorimeter
report
E. Kouznetsova, DESY
LAT calorimeter options
L.Suszycki, Cracow
Forward Calorimetry WG, Amsterdam, 31 March 2003
2
LAT luminosity measurement
Essential for precise luminosity measurement is a precise angle
measurement of the Bhabha scattered electrons.
L/L = 10-4 needs min = 1.4 rad
The standard (TDR) setup enables only
0.2 – 0.3 mrad accuracy with the price of 13440 channels.
We try

The standard setup improvements
and to consider alternative geometry setups:
 Flat LAT
 Stripped LAT
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Amsterdam 31. March ‚03
L.Suszycki, Cracow
Improved LAT geometry
Angle reconstruction using
All sensors :
=~0.9 mrad
Improvements comparing
to the Prague results:
1. Silicon sensors
arranged in planes
2. Non-projective cylinders
of equal height
Every 4th sensor :
=~1.1 mrad
Every 10th sensor :
=~1.5 mrad
It is resonable to apply fine
segmentation to a fraction
of cylinders only
4
Amsterdam 31. March ‚03
L.Suszycki, Cracow
Leackage makes
precision Lumi hard
5
Amsterdam 31. March ‚03
Achim Stahl
DESY Zeuthen
Flat LAT geometry
Sergey Kananov, Tel Aviv
Angle reconstruction
 All cylinders start at
z=136 cm
 7, 14, 18 or 56 cylinders
assumed
 Conical projective
geometry is kept (TDR)
Gain in angle resolution = 2.5
at price of increasing of
#channels of factor
56/14=4!
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Amsterdam 31. March ‚03
L.Suszycki, Cracow
Flat LAT shower maximum method
Sergey Kananov, Tel Aviv
Only rings near the shower
maximum at ring #8 are
significant for theta
reconstruction:
1, 3, 5, 7, 10, 16 or 20 „active”
rings
One can reach better angular
resolution with similar
#channels:
Uniform: 14 x 30 x 24 = 10080
=> 0.18 mrad
5 rings 2-fold granulated: 11760
=> 0.13 mrad
5 rings 4-fold granulated: 15120
=> 0.09 mrad
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Amsterdam 31. March ‚03
L.Suszycki, Cracow
Stripped LAT geometry
Bogdan Pawlik, Cracow
= gen - rec (radians)
vs.
strip layer („cylinder”)
Silicon 1mm strips arranged in
20 cones to read r and z x 256 strips
+
20 cones to read φ x 72 strips
=> 6560 channls in total
 = ~0.9mrad
at 9st layer
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Amsterdam 31. March ‚03
L.Suszycki, Cracow
LAT conclusions
 Preliminary results on alternative LAT geometry
are obtained
 Much more MC work is necessary to get closer
to the required acurracy of the angle
measurement
 Still awaiting for the Flat Mask decision
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Amsterdam 31. March ‚03
L.Suszycki, Cracow
Challenges in
Lumi Measurement
Some studies of sensitivity to systematic uncertainties
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Amsterdam 31. March ‚03
Achim Stahl
DESY Zeuthen
Method
BHLUMI (Ver. 4.04)
No Detector Simulation
Generate an event
 calculate coordinates on calorimeter
 apply systematic shifts
 recalculate coordinates
 apply selection cuts
 count events  Lumi
E+, E > 0.8 Ebeam
-
30 mrad < θ+ < 75 mrad
Acol < 11.5o
30 mrad < θ- < 75 mrad
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Amsterdam 31. March ‚03
Achim Stahl
DESY Zeuthen
Offset of Beams from Axis
Lin. Coeff. ≈ 0
Quadratic Coeff.:
Δoffset < 200 μm
12
Amsterdam 31. March ‚03
Achim Stahl
DESY Zeuthen
Inner Radius of Calorimeter :
ΔL/L ≈ 1.3 10-4/ μm
Longitudinal Distance
of Calorimeters :
ΔL/L ≈ -0.0033 / mm
z+ - z- < 60 μm
13
Amsterdam 31. March ‚03
Achim Stahl
DESY Zeuthen
Conclusions
To achieve ΔL / L ≈ 10-4:
Beam Offsets:
< 200 μm
Inner Radius of Cal
< 0.75 μm
Distance of Cals
< 60 μm
Center-of-Mass Energy: process dependent
but that‘s not all yet
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Amsterdam 31. March ‚03
Achim Stahl
DESY Zeuthen
LAT detector alignment
Wojciech Wierba
Institute of Nuclear Physics
Cracow Poland
Jerzy Zachorowski
M. Smoluchowski Institute of Physics
Jagiellonian University
Photonics Group
Cracow Poland
Amsterdam 31. March ‚03
Wojciech Wierba
Cracow, Poland
LAT alignment
The luminosity measurement
requires precision alignment of the LAT
detectors and stable, precision
placement in reference to the interaction
point. The beam pipe becomes as a
suitable reference because the Beam
Position Monitors are mounted inside
the vacuum pipe. This allows us to
correct the real LAT detectors position in
respect to the beam position.
There are four tasks:
 Measurement of the beam
pipe dimensions in the lab.
 Radial metrology and
mechanical design of the
LAT detectors.
 Initial alignment of the LAT
detectors in the forward
region.
 On line system to measure
displacement of the LAT
detectors.
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Amsterdam 31. March ‚03
Wojciech Wierba
Cracow, Poland
On line system to measure
displacement of the LAT detectors
 The Photonic sensor for the z (along the beam)
distance measurement:





Small probe head, just end of the ~3mm fiber.
Lightweight probe to be attached to the flange of the beam pipe.
All electronics and laser can be placed outside the TESLA detector.
Only fibers have to be feed near the LAT detector.
Continuous laser beam is not necessary i.e. power fault, laser
change/repair.
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Amsterdam 31. March ‚03
Wojciech Wierba
Cracow, Poland
On line system to measure
displacement of the LAT detectors
Fine pixel CCD sensor to measure x, y and  position :
The CCD detector should be glued to the rear face of the calorimeter. The laser beam
can be distributed via optical fiber. The laser spot will be formed by collimator or optics.
Advantages :
Problems :
Small and lightweight collimator/optics
to be attached to the flange of the beam
pipe.
Laser can be placed outside the
TESLA detector.
Continuous laser beam is not
necessary i.e. power fault, laser
change/repair.
Only some cables and fiber have to be
feed near the LAT detector.
Radiation hardness of the CCD
sensor and electronics. The CCD will
be placed between rear side of the
LAT calorimeter and tungsten shield
and probably the radiation dose will be
not so high.
Background from the particles. The
position measurement can be done in
the time slot between trains when
beams are not present. The speed of
the CCD sensor is sufficient to do that.
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Amsterdam 31. March ‚03
Wojciech Wierba
Cracow, Poland
First results from silicon
and diamond sensors
K. Afanasiev1, I. Emeliantchik1,
E. Kouznetsova2, W. Lohmann2,
W. Lange2
1
2
NC PHEP, Minsk
DESY Zeuthen
Test Set Up
or
Sr
diamond
PA
ADC
delay
in
discr
gate
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Amsterdam 31. March ‚03
E. Kouznetsova DESY Zeuthen
Signals from 90Sr – silicon and diamond :
Si
(mip)
Diamond
Diamond
Diamond
(noise)
(whole bspectra)
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Amsterdam 31. March ‚03
E. Kouznetsova DESY Zeuthen
Problems and further steps :
 Noise level is not optimal for signal/noise separation
(ENC ≈700 e)
 Possible solutions :
• Noise optimization of the existing preamplifier
• Switch to Amptek A250 (noise expected ≤ 350 e)
 New trigger scintillator matching the size of the sensor
 New diamond samples :
• Fraunhofer Institute (Freiburg) :
(12 x 12 mm)
300 and 200 m
Different surface treatments
• Prokhorov Institute (Moscow) - Dubna group
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Amsterdam 31. March ‚03
E. Kouznetsova DESY Zeuthen
New Design of the Mask
For L* = 3 m performance of the
mask calorimeters is doubtful
For larger L* things look easier
Question: How much L* do we
need?
Achim Stahl
DESY Zeuthen23
Fake Photons
Leackage makes
precision Lumi hard
Too close to
beamstrahlung
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Amsterdam 31. March ‚03
Achim Stahl
DESY Zeuthen
Advantages
Luminosity: More likely to achieve 0.01 %
No fakes can scatter from mask into ECal
Vacuum much better, large orfice, bellow, valve
Space for electronics available
Better separation of outer Cal from beamstrahlung
(5cm -> 8cm)
Hermetic to 3.9 mrad (was 5.5 with gaps)
Shintake monitor taken into account
L* approx. 4 meters
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Amsterdam 31. March ‚03
Achim Stahl
DESY Zeuthen