1. 1 Update offline zero suppression on missing E T Aim : Implementation of a true 2.5 cut Offline Studies of resolutions of Missing E T on zero bias events Runs studied: - 163392 2.5  run online from 6 th of September - 162594 1.5  run online from 25 th of August and 2.5  offline Stephanie Beauceron LPNHE – Paris Jet/Met Meeting 10/24/2002

2. 2 2.5 Cut Offline From Robert’s file (official noise), sigma for all channels is determined and non- linearity corrected  Convert the value to energy and cut on cell energy Missing E T is calculated without Coarse Hadronic. MexMey Met 162594 2.5  offline 163392 2.5  online Set

3. 3 Evolution with sigma cut Strange oscillations of ME x and ME y with the number of sigma… After 2.5 , we have more stable value for ME T and SE T

4. 4 Met resolutions for zero bias events  Cells with positive energy 162594 1.5  online 163392 2.5  online 162594 2.5  offline  Same noise variation between negative/positive energy cells  Cells with negative energy If (E cell >0) _ ME x =  p x.cos(  ) ME y =  p y.sin(  ) ME T =  (ME x 2 +ME y 2 ) SE T =  p T If (E cell <0) _ ME x =  -p x.cos(  ) ME y =  -p y.sin(  ) ME T =  (ME x 2 +ME y 2 ) SE T =  -p T

5. 5 Met resolutions for zero bias events  Cells with positive energy  All Cells  Compensation of the negative energy cells with positive ones 162594 1.5  online 163392 2.5  online 162594 2.5  offline If (E cell >0) _ ME x =  p x.cos(  ) ME y =  p y.sin(  ) ME T =  (ME x 2 +ME y 2 ) SE T =  p T ME x =  p x.cos(  ) ME y =  p y.sin(  ) ME T =  (ME x 2 +ME y 2 ) SE T =  p T

6. 6

7. 7 Met resolutions for zero bias events 162594 1.5  online 162594 2.5  offline Run I : Met ~ 0.020xSet + 1 Run II at 2.5  : Met = 0.025xSet + 1.7 Run II at 1.5  : Met = 0.026xSet + 0.4 From cells with positive energy

8. 8 Met resolutions for zero bias events 162594 1.5  online 162594 2.5  offline Run I : Met ~ 0.020xSet + 1 From cells with positive energy Run II at 2.5  : Met = 0.025xSet + 1.7 Run II at 1.5  : Met = 0.026xSet + 0.4 From cells with negative energy Run II at 2.5  : Met = 0.019xSet + 1.2 Run II at 1.5  : Met = 0.024xSet + 0.6

9. 9 Conclusion The noise from cells with negative energy is identical to the noise from cells with positive energy But the missing E T is not the same when we compute it with all the cells  The cells with negative energy vanish with positive ones. ME T resolution is compatible with Run I values.  Still to understand why ME x and Me y are varying with the value of the sigma cut…