Some results from LumiCal Monte Carlo Studies

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

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

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

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

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

7. Changes in Z position Original After change of the Z postions The new layer positions - not allowed to cover the neighbouring disc Z1 = Z1 id Zid = Zn+1 id - Zn id Zn+1= Zn + Zid + ZR Zn+1 - Zn < 0. 59 ZR simulation: from the distorted type of Gaussian distribution ( : from 5 up to 45 m) Z1 , Zid- the position of the first disc Zid - the distance between discs in ideal detector = 0.59 cm ZR - random selected z-position

8. Changes in X, Y positions MC simulation: Original Xn = Xid + XR Yn = Yid + YR Xn , Yn - new discs positions Deformed Xid , Yid - discs positions for ideal LumiCal XR, YR simulation XR, YR - random selected X and Y positions XR , YRwere simulated according to Gaussian distribution with  which was changed from 5 up to 45 m in 5 m step

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

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