K  reconstruction status

1. K reconstruction status P. Branchini E. De Lucia P. De Simone M. Martemianov B. Sciascia V. Patera • K+K- retracking features • New vs Old : resolution • New vs Old : efficiencies • Conclusion and outlook V.Patera – KLOE GM – Otranto – 10 June 2002

2. KPM Selection KPM retracking DST production Not yet addressed Done and working Finalized, under test KPM Reconstruction The KPM reconstruction has been updated/ridesigned, in particular with respect of: Track merging, T0 finding, K± TOF correction, Multiple scattering treatment optimization, ECLO and Event selection interaction V.Patera – KLOE GM – Otranto – 10 June 2002

3. Merge tracks and udpdate pattern candidates. Orders and updates K id from different ECL algos in ECLO Pattern Banks & ECLO Kmerge T0_find Finds the KPM t0 global T0GL New K TOF implementation, specific K m.s. treatment, correct hit times for T0 Fit Banks atfmod KPM retracking:new & updated modules module New features Updated bank V.Patera – KLOE GM – Otranto – 10 June 2002

4. K+K- reconstruction: merging Due to K large TOF, wrong T0 and large m.s. the “standard” rec. produces a large fraction of broken tracks (at the pattern level!). No recovery possible by the Fit K+mn The Kmerge module merge all the possible tracks (not only K+K- ) on the basis of their angle, distance and momenta and rebuild the KPM ECLO banks. After merging and T0 correction, the tracking/pass=2 (usually) splits only the correct kinks K-mn V.Patera – KLOE GM – Otranto – 10 June 2002

5. 2001 data t+-t- (ns) K reconstruction: T0 finding • Applied to tagged events with K decay products with ECAL cluster associated. • From K decay vertex position, cluster times, momentum of K and charged daughter at vertex is possible to trace back the T0 of the event. V.Patera – KLOE GM – Otranto – 10 June 2002

6. K (DTFS) first point - K(DHIT) first point Kaon length < 80 cm Kaon length > 80 cm  = 2.3 MeV/c  = 2.9 MeV/c  = 1.7 MeV/c  = 2.6 MeV/c RED : Lynch approximation PINK : Gaussian formula K reconstruction: multiple scattering KLOE memo 270 Good performance in KPM stream are obtained switching off m.s. only for K . Optimization still needed !! ( m.s. step, m.s. calculation..) V.Patera – KLOE GM – Otranto – 10 June 2002

7. K  retracking AC path The correct merging of the broken tracks must be done at level of pattern candidates  DTCE1 and DHRE1 banks are needed. The minimal AC path for K retracking is reported. The red modules have been updated/written for this stream use dcdbini raw2dtce dconvr dcprar - merge atfmod/par=1 vtxfin/par=1 -eclmod ecl_kpmfilt kmerge-t0_find/par=4 atfmod/par=2-vtxfin/par=2 The KPM retracking is very CPU consuming. The production rate on fibm12 has been estimated to be ~ 2 pb-1/day/CPU Now M.S. is switched off for K here !!! V.Patera – KLOE GM – Otranto – 10 June 2002

8. New vs Old: comparison is on the way • We are tuning the retracking on MC. To use old reconstruction chain we are forced to use the events streamed by the OLD selection algorithms. • The problem is a multivariate one.. We analize one refinement per time, but correlations are big! The fine tuning is still missing and only relative comparison are presented. • The efficiencies have been studied in a subsample of tagged events: given a tag we look at what happen in the opposite emisphere. V.Patera – KLOE GM – Otranto – 10 June 2002

9. KPM MC sample selection The KPM EVCL algorithms are OR-ed together. There is a big overlap among the three. The shown efficiency is computed by MC. Estimation from DATA is in progress ~ 5x105 MC events have been generated and reconstructed (with MB addition in the Drift Chamber). Out of that only ~ 1.7x105are filtered as KPM V.Patera – KLOE GM – Otranto – 10 June 2002

10. New vs Old : K momentum resolution @ first hit @ vertex V.Patera – KLOE GM – Otranto – 10 June 2002

11. New vs Old : K momentum resolution/2 Kaon Prec – Ptrue distribution at the decay vertex versus the Kaon decay path The distorsion induced in the OLD rec. gets more evident as far the track gets longer V.Patera – KLOE GM – Otranto – 10 June 2002

12. New vs Old: vertex resolution New The vertex resolution is slightly improved. In particular tails are reduced Old V.Patera – KLOE GM – Otranto – 10 June 2002

13. New vs Old : broken tracks Distribution of total length vs momentum of splitted kaons of the entire MC sample (1.7x105 ev). The merging get rid of most of the broken track better decay length distribution ! OLD NEW V.Patera – KLOE GM – Otranto – 10 June 2002

14. New vs Old : resolution on Pdaughter Distribution of the reconstructed Mp02 in the K rest frame The K momentum improved resolution slightly improves also the reconstruction of the daughter momentum in the K rest frame. The peak width can be looked at also in data !! V.Patera – KLOE GM – Otranto – 10 June 2002

15. New vs Old : resolution on Pdaughter Distribution of the reconstructed neutrino invariant mass squared in the K rest frame V.Patera – KLOE GM – Otranto – 10 June 2002

16. New vs Old : tracking eff. vs DC hits On the selected sample the tracking efficiency are similar. This analisys must be repeated on data to have the final answer on the retracking behaviour ! Ktracking efficiency V.Patera – KLOE GM – Otranto – 10 June 2002

17. New vs Old : tracking eff. vs cosq K Rec. Rec. Due to the request for at least a TAG to compute any eff, large events statistic is needed. V.Patera – KLOE GM – Otranto – 10 June 2002

18. New vs Old : tagging eff. vs DC hits Tagged/tracked eff. The new reconstruction seems to behaviour better than the standard one. The tagging efficiency is sensitive to the combination of tracking and vertex eff iciency N.B. is the eff of a very clean sub-sample! V.Patera – KLOE GM – Otranto – 10 June 2002

19. Conclusions • The retracking code of the KPM stream is in its final shape, yet has to be tested on high statistics • Sizeable (but not fantastic) improvement with respect to the standard reconstruction at first glance • Fine tuning is missing ( cuts on track merging, m.s. scatterers distribution, T0 for non tagged events..) • DST production could ( and should ) start since July V.Patera – KLOE GM – Otranto – 10 June 2002