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contributions from Forward Calorimetry Collaboration L.Suszycki AGH University of Science and Technology Cracow. Experimental Aspects of Precision Luminosity Measurement. - PowerPoint PPT Presentation
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Experimental Aspects of Precision Luminosity
Measurementcontributions from
Forward Calorimetry Collaboration
L.Suszycki
AGH University of Science and Technology Cracow
L. Suszycki LCWS 04: Paris 19-23 April 2004 2
Forward Calorimetry Collaboration
H. Abramowicz11, K. Afanaciev8, S. Denisov10, R. Dollan5, D. Drachenberg5, V. Drugakov8, I. Emeliantchik8, S. Erin10, R. Ingbir11, S. Kananov11, A. Kowal4, E.
Kousnetsova5, R. Kwee5, W. Lange5, A. Levy11, W. Lohmann5, J. Lukasik4, M. Luz5, D. Miller7, I. Minashvili6, U. Nauenberg1, B. Pawlik4, N. Rusakovich6, A. Rybin10, N.
Shumeiko8, A. Stahl5, L. Suszycki4, K. Suzdalev10, V. Vrba9, W. Wierba2, J. Zachorowski3, L. Zawiejski2, F. Zyazyulya8
1 University of Colorado, Boulder, USA, 2 Institute of Nuclear Physics, Cracow, Poland, 3 Jagellonian University, Cracow, Poland, 4 University of Science and Technology, Cracow, Poland, 5 DESY, Zeuthen, Germany, 6 Joint Institute of
Nuclear Research (JINR), Dubna, Russia, 7 University College London, London, UK, 8 NC PHEP, Minsk, Belarus, 9 Institute of Physics of the Academy of
Sciences of the Czech Republik, Praha, Czech Republik, 10 Institute of High Energy Physics, Protvino, Russia, 11 Tel-Aviv University, Tel-Aviv, Israel.
L. Suszycki LCWS 04: Paris 19-23 April 2004 3
Forward Calorimetry Layout
LAT functionally is nowLuminosityCalorimeter
LumiCal– z = 305-325 cm– R= 8-28 cm – 26.2<<82 mrad– 0<<360 deg
TESLA TDR design (postponed)
Low Angle Tagger(LAT)
New mask design l*=4m
L. Suszycki LCWS 04: Paris 19-23 April 2004 4
Luminosity measurement
Based on Bhabha scattering e+e- e+e-()
At 250 GeV, =5.5 nb,
For L = 3.4 · 1034 cm-2s-1 rate R 180 Hz `one minute` luminosity possible on-line
Goal precision: L/L = 10-4
Can it be done?
LCWS 04: Paris 19-23 April 2004 5
• Si/W calorimeters on both sides of the IP
• 16/64 concentric cylinders (in r)• 30 rings (in z)• 24/120 sectors (in )• Detector simulation with
Geant3.21 Two calorimeter structures considered:• Si pads • Si strips
LumiCal Design Simulation
beam pipe
Tungsten mask
L. Suszycki LCWS 04: Paris 19-23 April 2004 6
Polar angle reconstruction• Polar angle reconstruction – good resolution, uniformity, no
bias• Fiducial volume definition min is crucial:
d/d ~1/3 , so tot(min, max) ~ min-2 , min = 26.2 mrad
L/L = 2min/ min -> min = 1.3 rad
L. Suszycki LCWS 04: Paris 19-23 April 2004 7
Angle reconstruction - Pad Design
• „oscillations” around rec vs gen linear dependence due to detector granularity
• resolution in is -dependent due to cylindrical geometry
L. Suszycki LCWS 04: Paris 19-23 April 2004 8
LumiCal – reconstruction
24 sectors
48 sectors Resolution as function of the number of cylinders (in r) and sectors (in φ)
Angle reconstruction with simple energy weighting
Both large bias and bad resolution ~0.2 – 0.3 mradobserved even using large numbers of cylinders/sectors
A.Kowal (UST Cracow)
HEP Tel Aviv UniversityA Luminosity Detector for the Future Linear Collider
Reconstruction Algorithm
)]}ln([,0max{T
ii E
EconstW
i
ii
E
EXX
i
ii
W
WXX
Events Num.
)(radgenrec
)(radgenrec
)(radgen
We explored two reconstruction algorithms: Energy weighting and logarythmic weghting
The log. weight fun. was designed to reduce steps in a granulated detector :
1. Selection of significant cells.
2. Log. smoothing.
Log. weight.
E weight.
HEP Tel Aviv UniversityA Luminosity Detector for the Future Linear Collider
Logarithmic Constant
Constant value
Constant value
)]}ln([,0max{T
ii E
EconstW
After selecting:
We explored a more systematic approach.
The first step is finding the best constant to use under two criteria:
1. Best resolution.
2. Minimum bias.
400 GeV
))(_( radmean genrec
))(( rad
HEP Tel Aviv UniversityA Luminosity Detector for the Future Linear Collider
Energy dependent constant
)]}ln()([,0max{T
ibeami E
EEconstW
The goal is to find a global weight function.
Is the log. weight really a constant ?
Constant value
HEP Tel Aviv UniversityA Luminosity Detector for the Future Linear Collider
Beam Energy (GeV)
))(( rad
Angular resolution
Results using ‘pure electron’ simulation
Can we maintain same detector properties using a more ‘real’ MC ?
HEP Tel Aviv UniversityA Luminosity Detector for the Future Linear Collider
Azimuthal resolution
)]}ln([,0max{T
ii E
EconstW
Events Num.E weight.
Log. weight.
(deg)genrec
L. Suszycki LCWS 04: Paris 19-23 April 2004 14
LumiCal – Stripped design
• 30 tungsten rings
• every second ring has either 120 radial or 64 concentric Si strips
• 2960 readout channels
• but necessary sectioning of Si sensors will give factor of ~3 - 4
B.Pawlik (INP-PAN, Cracow)
LCWS 04: Paris 19-23 April 2004 15
Stripped LumiCal reconstruction results
• Accuracy in -reconstruction is ~50
rad
• Energy measurement with accuracy of
5 GeV (E~0.31√E)• low segmentation level
seems to be sufficient (~3000 readout channels)
B.Pawlik (INP-PAN, Cracow)
L. Suszycki LCWS 04: Paris 19-23 April 2004 16
Stripped LumiCal - Bhabha events
Reconstruction : energy 7GeV (0.44√E) Angle ~0.09 mrad ACOLINEARITY ~1MRAD
Egen - Erec
B.Pawlik (INP-PAS, Cracow)
θL – θR (mrad)θgen – θrec (mrad)
L. Suszycki LCWS 04: Paris 19-23 April 2004 17
Detector mechanics
• Calorimeter assembling - perfect homogenity, - stable
• Calorimeter positioning (rmin =8 cm), rmin = 4 m, z = 0.2mm
Challenging for mechanics and thermal stability! rmin = 1m x T for steel support ( factor 1/3 for W support)
• Monitoring of calorimeter shift and/or deformation due to:- temperature- ageing- ground motionLaser method for on-line control is being developed
LCWS 04: Paris 19-23 April 2004 18
Laser monitoring of the LumiCal detector displacement
(very preliminary)
reconstruction of He-Ne laser spot on CCD camera
Requirements on alignment:Inner Radius of LumiCal < 4 μmAxial LumiCal position < 60 μm
possible resolution of ~1m if the center of the light spot is determined with accuracy better than 0.1 pixel
J.Zachorowski (UJ),W.Wierba (INP-PAN) Cracow
Laser scan of x and y positions
slope 0.127pixel/m
To be done:• Small-pixel BW camera, • Manually controlled sensitivity,• Semiconductor laser,• Piezoelectric movement of
camera,• Independent measurement of
displacement,
• Multiframe statistics.
L. Suszycki LCWS 04: Paris 19-23 April 2004 20
Monitoring of the beam parameters
Generator level Bhabha simulation (A.Stahl, Desy-Zeuthen) yields permissible beam deviations:
beam offset r = 650 m
IP longitudinal offset z = 150 mbeam tilt = 0.2 mrad
Beam Calorimeter (BeamCal) foreseen for fast beam diagnostics may help
L. Suszycki LCWS 04: Paris 19-23 April 2004 21
Conclusions• High precision luminosity measurement involves
numerous experimental and technical problems• First MC results indicate ways of the future work• Angle reconstruction must be done very
carefully minimizing the bias• Special system for monitoring the detector
possible moves and/or deformations has to be built
• Limited space for detector makes mechanics and electronics still more difficult
• Optimized design of LumiCal is strongly dependent on choice of the LC option
The end
Thank you
Detector Design
0.34 cm Tungsten
0.31 cm Silicon
Cell Size1.3cm*2cm>1.3cm*6cm<
~1 Radiation length
~1 Radius Moliere
HEP Tel Aviv UniversityA Luminosity Detector for the Future Linear Collider
15 cylinders * 24 sectors * 30 rings = 10800 cells
RL
8 cm
28 cm
6.10 m
L. Suszycki LCWS 04: Paris 19-23 April 2004 24
LumiCal pad–design optimization
• # of active rings around the shower maximum
• logarithmic weighting in angle reconstruction
• () ~ 70 rad feasible
resolution
# of cylinders
R. Ingbir (TAU)