1. Muon Identification Antoine Cazes Laboratoire de l’ Accelerateur Lineaire OPERA Collaboration Meeting in Frascatti Physics coordination meeting. October 28 th 2002.

2. Antoine Cazes OPERA collaboration meeting Physics coordination - 10/28/2002 Introduction First goal: follow the work of Dario  Status Report CERN/SPSC 200-025  D. Autiero & M. Komatsu Physics Performance for 3 to 1 SuperModules Contents:  Analyzed event  Selection criteria A) Topological cut B) brick Matching C) other Topological cut  Preliminary results

3. Antoine Cazes OPERA collaboration meeting Physics coordination - 10/28/2002 Analyzed event Files used : The simulation from may 2001 Nomad Generator (except charm events) Stat:  CC DIS : 20k  DIS : 7k charm (non  decay) : 6k  NC : 6.5k The OPERA configuration is TT (24 planes) DT (6x 3planes) RPC (2x 11planes)

4. Antoine Cazes OPERA collaboration meeting Physics coordination - 10/28/2002 A) First topological cut Tools: 1) Does the track exit by the back of the spectrometer? 2) The total number of wall (target + spectro) crossed by the track 3) The isolation of the Track : number of walls where there are no other hits that the one of the track 4) The mean distance between the track and the shower: computed in one projection, average of the distance between the track and the barycenter of the others hits computed for each walls. The track analyzed is the longest track found by OpRec (3D track) The cut is: back spectro OR (nb walls AND (iso OR mean dist)) (1) OR [ (2) AND [ (3) OR (4) ]]

5. Antoine Cazes OPERA collaboration meeting Physics coordination - 10/28/2002 Efficiency versus number of walls crossed by the track 95% 91% 80% 90% 25% 8% 95% 90% Cut: #Wall>9

6. Antoine Cazes OPERA collaboration meeting Physics coordination - 10/28/2002 Efficiency versus number of isolated walls 96% 92% 82% 92% 30% 12% 97% 91% Cut: # Iso>6

7. Antoine Cazes OPERA collaboration meeting Physics coordination - 10/28/2002 Efficiency versus mean distance 97% 93% 85% 93% 34% 11% 98% 92% Cut: mean D>20cm

8. Antoine Cazes OPERA collaboration meeting Physics coordination - 10/28/2002 B) Matching between the track in the TT and in the brick (1) 1) Angular matching, computed in 3D : Loop on all brick tracks and find the best matching. Cut on the maximum allowed angle. Smearing : 2mrad in the brick RMS    QE  DIS  CC DIS (mm) 7(5)14(10)12(8) (mrad) 34(18)51(27)38(14) *: diff. Between true value at first point in the Target and the value obtained by the fit. No cuts on muon Id and energy. (normalized)

9. Antoine Cazes OPERA collaboration meeting Physics coordination - 10/28/2002 Angular matching efficiency versus angle cut 100% 84% 65% 99% 88% 10% 100% 80% Cut:  <200mrad

10. Antoine Cazes OPERA collaboration meeting Physics coordination - 10/28/2002 Matching between the track in the TT and in the brick (2) 2) Momentum matching The momentum is computed in the detector using dE/dx backward inversion algorithm. (remind that 12 walls ~ 1 GeV) The momenta in the brick are smeared with a fixed resolution  p/p = 20% (if 20%  30% no change within statistical errors) Event truly matching the brick muon

11. Antoine Cazes OPERA collaboration meeting Physics coordination - 10/28/2002 Matching Efficiency versus different Momentum Matching cuts ( P range < 1.1  P brick + 1. ) AND ( ( P brick < 3 AND P range < 0.6  P brick - 0.2) OR ( P brick > 3 AND P range < 1.6 ) ) The cut is: Different 2D cuts 97% 95% 86% 91% 45% 25% 96.5% 94%

12. Antoine Cazes OPERA collaboration meeting Physics coordination - 10/28/2002 Matching cut - Recovering Events Matching Cut required are :  <200mrad AND Momentum Matching We need to improve charm rejection: Idea : so far, matching required, but not necessary No Matching case: other topological cut (C) -If the track exits the spectrometer -OR a the minimum number of wall more than 14.

13. Antoine Cazes OPERA collaboration meeting Physics coordination - 10/28/2002 Preliminary Efficiencies  CC DIS  DIS Charm (non  decay)  NC AA 94.0% (  0.2%) 87.3% (  0.4%) 94.1% (  0.3%) 15.3% (  0.4%) 10.5% (  0.4%) 93.5% (  0.3%) 86.6% (  0.4%) 93.4% (  0.2%)   ID 49.% (  2.0%) 86.% (  2.4%) 92.% (  1.2%) 81% (  1.7%) CC  matching 96.8% (  0.1%) 90.5% (  0.4%) 96.0% (  0.3%) 37.9% (  1.5%) BB 91.0% (  0.2%) 79.0% (  0.5%) 90.3% (  0.4%) 5.8% (  0.3%) Err stat. Only   ID =   +    (1-  matching ).  C  Note 94.4%10.6% Consistent

14. Antoine Cazes OPERA collaboration meeting Physics coordination - 10/28/2002 Future plans Optimize the existing cuts: Use both projections for mean distance computation 3D calculation of the momentum range reorganize the cuts New Ideas: look at the second reconstructed track (if existing). shower shape variables to study muon isolation cut study the origin of the miss-matching Needs: full fitting program (in progress) to estimate the effects of the  Id cuts on the final  analysis (signal/background). To take into account the efficiencies related to: brick finding, vertex finding, kink finding for long decay, kinematics for short…)

15. Antoine Cazes OPERA collaboration meeting Physics coordination - 10/28/2002  NC event, momentum cut

16. Antoine Cazes OPERA collaboration meeting Physics coordination - 10/28/2002 Number of Walls

17. Antoine Cazes OPERA collaboration meeting Physics coordination - 10/28/2002 Matching Efficiency (  matching ) versus Angular matching Purity: ~ 98% Purity: ~ 98% Purity: ~ 94% Purity: ~ 94% Purity: ~ 93% Purity: ~ 93% 93.7% 92.4% 84.5% 87% 11.5% 8.5% 94% 92.4% Purity : the particle matched is really the muon Cut:  >200mrad

18. Antoine Cazes OPERA collaboration meeting Physics coordination - 10/28/2002 Efficiencies (smearing momentum 30%)  CC DIS  DIS Charm (non  decay)  NC  topo1 94.0% (  0.2%) 87.3% (  0.4%) 94.1% (  0.3%) 15.3% (  0.4%) 10.6% (  0.4%) 93.5% (  0.3%) 86.6% (  0.4%) 93.3% (  0.2%)   ID 50.% (  2.0%) 87.% (  2.1%) 92.% (  1.1%) 82% (  1.5%)  topo2  matching 96.1% (  0.1%) 89.5% (  0.4%) 95.3% (  0.3%) 39.3% (  1.5%) 11 90.3% (  0.2%) 78.0% (  0.5%) 89.7% (  0.4%) 6.0% (  0.3%) Proposal Status Report Last Note