1. Radial Tail Resolution in the SELEX RICH A. Morelos, P. Cooper, J
Radial Tail Resolution in the SELEX RICH A. Morelos, P.Cooper, J.Mata, J.Engelfried Using a 7 Million data sample of 600 GeV/c single track pion events, where the pion track is reconstructed upstream and downstream the SELEX RICH, a circle fit on the phototubes ring is performed. From the fit we get three parameters, the radius, and the center coordinates plus their statistical errors. Applying modest cuts on track and circle fit uncertainties we build the radius histogram distribution and count the tail the events that fall outside 5s from the b=1 radius, giving a fraction of 4x10-5 events outside the gaussian tails. This control of events stablish the ability of using the RICH as velocity spectrometers for high precession search of the K+  p+ n anti(n) experiments like CKM.

2. outline
) motivation, CKM mass resolution
) SELEX, three aspects
) radius distributions & tails
) a look into simulation
) summary

3. PNN1
PNN2

5. Número de planos prendidos Npl
Beam Transition Radiation Detector BTRD
Número de planos prendidos Npl

6. Ring Imaging Cherenkov
beam event at 600 GeV/c

7. Vector Drift Chambers VDC

8. Downstream track M1 M2
RICH
Vertex
Vdc-a
Vdc-b
Beam

9. Track existence
Select PMT´s around cm
From SELEX standard radius
ring fit
soft cuts on center and radius uncertainties

10. Mean radius dispersion by run
Dispersion cm
s radius 0.15 cm single track
0.18 cm multi-track

11. s C2n by run Single hit 0.55  0.47 cm in agreement
no track uncertainty

12. Ring Radius distribution
upstream track existence
dowstream track existence

13. 5s tail (CKM < 3 x10-5)
upstream existence
downstream existence

14. 3 s tail difference

15. for decay events in RICH
A model
for decay events in RICH
blind
Rich
downstream
existence

16. Events are left in the tails
“ C “ type: either close or opens the radius

17. A look into random PMT simulation no PMT efficiency
no individual noise

18. between two consecutive PMT´s per event
“ C “ event like events
radian
radian
maximum angle
between two consecutive PMT´s per event
( radians )
data broadness: improve lowering noise and better efficiency

19. Summary ) downstream track existence eliminated decay events which
were in the tail region
) With 5 s tail analysis we are in a region of 3.9 x10-5 events,
close to CKM requirements (less than 3 x10-5 )
) Still: a completely stand alone algorithm, work is being done,
and include noise and efficiency per tube in simulation