Luminosity and beam calorimeter report E. Kouznetsova, DESY

Luminosity and beam calorimeter report

E. Kouznetsova, DESY

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LAT calorimeter options

L.Suszycki, Cracow

Forward Calorimetry WG, Amsterdam, 31 March 2003

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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

L.Suszycki, CracowAmsterdam 31. March ‚03

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Improved LAT geometry

Improvements comparing to the

Prague results:

1. Silicon sensors arranged in

planes

2. Non-projective cylinders of

equal height

Angle reconstruction using

All sensors :

=~0.9 mrad

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

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Leackage makesprecision Lumi hard

Achim Stahl DESY ZeuthenAmsterdam 31. March ‚03

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Flat LAT geometry

All cylinders start at z=136 cm

7, 14, 18 or 56 cylinders assumed

Conical projective geometry is kept (TDR)

Sergey Kananov, Tel Aviv

Angle reconstruction

Gain in angle resolution = 2.5at price of increasing of

#channels of factor 56/14=4!


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Flat LAT shower maximum method

Sergey Kananov, Tel AvivOnly 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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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

Stripped LAT geometryBogdan Pawlik, Cracow

= gen - rec (radians)vs.

strip layer („cylinder”)

= ~0.9mrad

at 9st layer


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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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Challenges in Lumi Measurement

Some studies of sensitivity to systematic uncertainties


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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

Acol < 11.5o

30 mrad < θ+ < 75 mrad

30 mrad < θ- < 75 mrad


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Lin. Coeff. ≈ 0

Quadratic Coeff.:Δoffset < 200 μm

Offset of Beams from Axis


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Inner Radius of Calorimeter :

ΔL/L ≈ 1.3 10-4/ μm


Longitudinal Distance of Calorimeters :

ΔL/L ≈ -0.0033 / mmz+ - z- < 60 μm

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Conclusions

Beam Offsets: < 200 μm

Inner Radius of Cal < 0.75 μm

Distance of Cals < 60 μm

Center-of-Mass Energy: process dependent

To achieve ΔL / L ≈ 10-4:

but that‘s not all yet


LAT detector alignment

Wojciech WierbaInstitute of Nuclear Physics

Cracow Poland

Jerzy ZachorowskiM. Smoluchowski Institute of Physics

Jagiellonian UniversityPhotonics GroupCracow Poland

Wojciech Wierba Cracow, PolandAmsterdam 31. March ‚03

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LAT alignmentThe 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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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.

On line system to measure displacement of the LAT detectors


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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 :

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.

Problems :

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.

First results from silicon and diamond sensors

K. Afanasiev1, I. Emeliantchik1, E. Kouznetsova2, W. Lohmann2, W. Lange2

1 NC PHEP, Minsk2 DESY Zeuthen

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Test Set Up

E. Kouznetsova DESY ZeuthenAmsterdam 31. March ‚03

discr

delay

in

gate

ADC

PAdiamond

Sr

or

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Signals from 90Sr – silicon and diamond :

Si(mip)

Diamond(noise)

Diamond(whole -spectra)Diamond


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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 sensorNew diamond samples :

• Fraunhofer Institute (Freiburg) :(12 x 12 mm)300 and 200 mDifferent surface treatments

• Prokhorov Institute (Moscow) - Dubna group

Problems and further steps :


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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 Zeuthen

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Leackage makesprecision Lumi hard

Fake Photons

Too close to beamstrahlung


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Advantages

Luminosity: More likely to achieve 0.01 %No fakes can scatter from mask into ECalVacuum much better, large orfice, bellow, valveSpace for electronics availableBetter 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


Documents

Luminosity and beam calorimeter report E. Kouznetsova, DESY