K group activitiesK group activities

K+K- retracking features

New vs Old : resolution

future planning.

Conclusion and outlook

K+K- retracking features

New vs Old : resolution

future planning.

Conclusion and outlook

KPM ReconstructionKPM Reconstruction

KPM Selection KPM retracking DST production

Done and working

Finalized, under test

Not yet addressed

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

In Otranto In Otranto

Done andworking

Since August Under debugging

now

KPM retracking:new & updated modules

KPM retracking:new & updated modules

Kmerge

T0_find

atfmod

Merge tracks and udpdate pattern candidates. Orders and updates K id from different ECL algos in ECLO

Pattern Banks & ECLO

Finds the KPM t0 global T0GL

New K TOF implementation, specific K m.s. treatment, correct hit times for T0

Fit Banks

module New features Updated bank

K+K- reconstruction: merging

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

Kaon track

Kaon track

K reconstruction: T0 findingK reconstruction: T0 finding

o Applied to tagged events with K decay products with ECAL cluster associated.

o 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.

t+-t- (ns)

2001 data

Kresolution/1Kresolution/1

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!

Sigma = 3.3 MeV Sigma = 3.4 MeV

Sigma = 2.0 MeV Sigma = 2.0 MeVNew

Old

K pullsK pulls

Pools are now ok!

The dE/dx for a kaon is subtracted while tracking and multiple scattering is taken into account in the error matrix

Pull = 1.1 Pull = 1.15 New

Old

K retracking AC pathK retracking AC path

use kpm_restore dcdbini raw2dtce t0meno dconvr dcprar merge 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 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

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.

New vs Old recostructionNew 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.

New vs Old : K momentum resolution/2

New vs Old : K momentum resolution/2

The distorsion induced in the OLD rec. gets more evident as far the track gets longer

Kaon Prec – Ptrue distribution at the decay vertex versus the Kaon decay path

Effect on dataEffect on data

-- old recostruction-- new recostruction

The new recostructionslightly improves resolution

New vs Old: vertex resolution

New vs Old: vertex resolution

New

Old

The vertex resolutionis slightly improved. In particular tails are reduced

New vs Old : broken tracks 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

New vs Old : tracking eff. vs DC hitsNew vs Old : tracking eff. vs DC hits

On the selected sample the tracking efficiency are similar.

K tracking efficiency

New vs Old : tracking eff. vs cos K

New vs Old : tracking eff. vs cos K

Due to the request for at least a TAG to compute any eff, large events statistic is needed.

Rec.

Rec.

New vs Old : tagging eff. vs DC hits

New vs Old : tagging eff. vs DC hits

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!

Tagged/tracked eff.

Future planning:Future planning:

The cross section: (next talk) memo by end of 2002.

Br (K+ Br ( K+ Maxim PhD thesis.

Absolute Br(K+) by summer 2003 (2 body, semileptonic).

Br (K+ Andrea Ventura PHD thesis by summer 2003.

Br (K+ e+Andrea Ventura PHD thesis by summer 2003.

ConclusionsConclusions

• 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).