Experimental Aspects of Precision Luminosity Measurement contributions from Forward Calorimetry Collaboration L.Suszycki AGH University of Science and Technology Cracow

L. SuszyckiLCWS 04: Paris April Forward Calorimetry Collaboration H. Abramowicz 11, K. Afanaciev 8, S. Denisov 10, R. Dollan 5, D. Drachenberg 5, V. Drugakov 8, I. Emeliantchik 8, S. Erin 10, R. Ingbir 11, S. Kananov 11, A. Kowal 4, E. Kousnetsova 5, R. Kwee 5, W. Lange 5, A. Levy 11, W. Lohmann 5, J. Lukasik 4, M. Luz 5, D. Miller 7, I. Minashvili 6, U. Nauenberg 1, B. Pawlik 4, N. Rusakovich 6, A. Rybin 10, N. Shumeiko 8, A. Stahl 5, L. Suszycki 4, K. Suzdalev 10, V. Vrba 9, W. Wierba 2, J. Zachorowski 3, L. Zawiejski 2, F. Zyazyulya 8 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. SuszyckiLCWS 04: Paris April Forward Calorimetry Layout LAT functionally is now LuminosityCalorimeter LumiCal –z = 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. SuszyckiLCWS 04: Paris April Luminosity measurement Based on Bhabha scattering e+e-  e+e-(  ) At 250 GeV,  =5.5 nb, For L = 3.4 · cm -2 s -1 rate R  180 Hz  `one minute` luminosity possible on-line Goal precision:  L/L = Can it be done?

LCWS 04: Paris April 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. SuszyckiLCWS 04: Paris April 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 = 2  min /  min ->   min = 1.3  rad

L. SuszyckiLCWS 04: Paris April Angle reconstruction - Pad Design „oscillations” around  rec vs  gen linear dependence due to detector granularity resolution in  is  - dependent due to cylindrical geometry

L. SuszyckiLCWS 04: Paris April 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 mrad observed even using large numbers of cylinders/sectors A.Kowal (UST Cracow)

HEP Tel Aviv UniversityA Luminosity Detector for the Future Linear Collider Reconstruction Algorithm Events Num. 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 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

HEP Tel Aviv UniversityA Luminosity Detector for the Future Linear Collider Energy dependent constant 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) 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 Events Num. E weight. Log. weight.

L. SuszyckiLCWS 04: Paris April 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 April 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. SuszyckiLCWS 04: Paris April Stripped LumiCal - Bhabha events Reconstruction : energy 7GeV (0.44√E) Angle ~0.09 mrad ACOLINEARITY ~1MRAD E gen - E rec B.Pawlik (INP-PAS, Cracow) θ L – θ R (mrad)θ gen – θ rec (mrad)

L. SuszyckiLCWS 04: Paris April Detector mechanics Calorimeter assembling - perfect homogenity, - stable Calorimeter positioning (r min =8 cm),  r min = 4  m,  z = 0.2mm Challenging for mechanics and thermal stability!  r min = 1  m x  T for steel support ( factor 1/3 for W support) Monitoring of calorimeter shift and/or deformation due to: - temperature - ageing - ground motion Laser method for on-line control is being developed

LCWS 04: Paris April 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 μm Axial LumiCal position < 60 μm possible resolution of ~1  m 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. SuszyckiLCWS 04: Paris April 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  m beam tilt  = 0.2 mrad Beam Calorimeter (BeamCal) foreseen for fast beam diagnostics may help

L. SuszyckiLCWS 04: Paris April 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 Size 1.3cm*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 = cells R L 8 cm 28 cm 6.10 m

L. SuszyckiLCWS 04: Paris April 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)