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K  group activities

K  group activities. K + K - retracking features New vs Old : resolution future planning. Conclusion and outlook. KPM Selection. KPM retracking. DST production. Not yet addressed. Done and working. Finalized, under test. KPM Reconstruction. In Otranto. In Otranto.

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K  group activities

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  1. K group activities • K+K- retracking features • New vs Old : resolution • future planning. • Conclusion and outlook

  2. KPM Selection KPM retracking DST production Not yet addressed Done and working Finalized, under test KPM Reconstruction In Otranto In Otranto Done and working Under debugging Since August now 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

  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

  4. Kaon track Kaon track 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 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

  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.

  6. Kresolution/1 Old Sigma = 3.3 MeV Sigma = 3.4 MeV New Sigma = 2.0 MeV Sigma = 2.0 MeV In Otranto we had switched off multiple scattering. dE/dx implementation did not distinguish in between pion and kaon. Pools (errors) were wrong for kaons!

  7. K pulls New Pull = 1.1 Pull = 1.15 Old The dE/dx for a kaon is subtracted while tracking and multiple scattering is taken into account in the error matrix Pools are now ok!

  8. 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 kpm_restore dcdbini raw2dtce t0meno dconvr dcprarmerge atfmod/par=1 vtxfin/par=1 trclmod/par=1 eclmod/par=3 ecl_kpmfilt t0_find/par=4 clufixtin/par=2 kmerge atfmod/par=2 vtxfin/par=2 trclmod/par=2 The KPM retracking is very CPU consuming. The production rate on fibm12 has been estimated to be ~ 1 pb-1/day/CPU Now M.S. is not switched off for K here !!! But it was switched off in Otranto.

  9. New vs Old recostruction • We have tuned the retracking on MC. This work has been done on events selected by the NEW selection algorithms, reconstructed with the standard tracking (no dE/dx for K+/- and no MS corrections). • The problem is a multivariate one.. We have analized one refinement at the time. • The efficiencies have been studied in a subsample of tagged events: given a tag we look at what happen in the opposite hemisphere.

  10. 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

  11. Effect on data -- old recostruction -- new recostruction The new recostruction slightly improves resolution

  12. New vs Old: vertex resolution New The vertex resolution is slightly improved. In particular tails are reduced Old

  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

  14. New vs Old : tracking eff. vs DC hits On the selected sample the tracking efficiency are similar. Ktracking efficiency

  15. 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.

  16. 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!

  17. Future planning: • The cross section: (next talk) memo by end of 2002. • Br (K+ m+n)/ Br ( K+ p+po ) Maxim PhD thesis. • Absolute Br(K+) by summer 2003 (2 body, semileptonic). • Br (K+ p+p0p0 ) Andrea Ventura PHD thesis by summer 2003. • Br (K+ e+np0p0 ) Andrea Ventura PHD thesis by summer 2003.

  18. 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 • We now have good pulls. • DST production is starting (it should last 1 month).

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