1. 1 Some results from LumiCal Monte Carlo Studies Michał Karbowiak, B. Pawlik, L. Zawiejski Michał Karbowiak (*), B. Pawlik, L. Zawiejski Institute of Nuclear Physics PAN, Cracow FCAL workshop October 17 2006 Munich (*) Diploma student from

2. 2 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

3. 3 LumiCal Simulation - an example pairs e + e - LumiCal IP beamstrahlung Bhabha : e+e–  e+e– (n)  Scattered electrons emitted photons BHLUMI : Guinea_Pig :

4. 4 The LumiCal positioning Two different crossing angles were selected : 0 and 20 mrad ( calorimeter along the main detector axis or an outgoing pipe) The shifts in perpendicular and longitudinal directions  z z z z  (x,y) Approximation : 20 mrad 0 mrad LumiCal IP  min 20 mad O mrad  z : 50  m steps for Z in range (-300, 300)  m  X : 50  m for (X,Y) in the range (0., 300)  m  =  gen  =  gen -  rec  L/L (  L/L ) - linear fit bias in  ~ 10 bias in  ~ 10 -5 Statistics for each point: 50 000 Bhabha events 50 000 Bhabha events  L/L (  L/L ) – the second order polynomial

5. 5 absorber ceramic sensor Internal structure One disc structure: original structure air LumiCal : changes in the internal structure

6. 6 Method: variation in position X,Y and Z of the absorber and sensor layersDeformations Z Z Z 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 deformation in Z axis deformation in X i Y axes

7. 7 Changes in Z position Original After change of the Z postions Z 1, Z id - the position of the first disc  Z id - the distance between discs in ideal detector = 0.59 cm Z R - random selected z-position Z R simulation: from the distorted type of Gaussian distribution (  : from 5 up to 45  m) Z Z 1 = Z 1 id  Z  Z id = Z n+1 id - Z n id Z Z n+1 = Z n +  Z id + Z R Z Z n+1 - Z n < 0. 59 The new layer positions - not allowed to cover the neighbouring disc

8. 8 Changes in X, Y positions Original Deformed X n = X id + X R Y n = Y id + Y R X n, Y n - new discs positions X id, Y id - discs positions for ideal LumiCal X R, Y R - random selected X and Y positions MC simulation: X R, Y R were simulated according to Gaussian distribution with  which was changed from 5 up to 45  m in 5  m step X R, Y R simulation

9. 9 Effect on relative luminosity measurements Change in structure along Z axisChange in structure along (X, Y ) axis The crossing angle 0 mrad The systematic effect on relative luminosity measurements : at least one order smaller than from the shifts the whole Lumical

10. 10 Conclusions Monte Carlo simulated events for two crossing angles 0 and 20 mrad were used Monte Carlo simulated events for two crossing angles 0 and 20 mrad were used in estimation effect on luminosity measurements from in estimation effect on luminosity measurements from the uncertainties in LumiCal position measurements the uncertainties in LumiCal position measurements or from deformation its internal structure or from deformation its internal structure The shift of the detector up to ~ 100  m in longitudinal or transversal direction 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 creates systematic effect on relative luminosity measurement on the level 10 -4. The effect from deformation of the internal LumiCal structure is at least The effect from deformation of the internal LumiCal structure is at least one order smaller. one order smaller.