π- from h- analysis

neutrino.fuw.edu.pl

π- from h- analysis

π- from h- analysis

Tomasz Palczewski.

A. Soltan Institute for Nuclear Studies.

Warsaw

Poland.


Outline

• Negative pions analysis strategies

• Run 2C target, Standard Settings.

– All runs.

• MC

– Small statistics (8 k events)

• Event Selection

• Track Selection

• H - spectra

– P vers θ


First Step:

Reconstruct all negative tracks from the

main vertex.

Second Step:

MC Analysis to obtain non pion contamination

and to introduce geometrical acceptance

Benjamin Lungwitz Master Thesis


Events cuts

• Event-Cuts from „Claudia Strabel”

– ( https://twiki.cern.ch/twiki/bin/view/NA61/EventTrackCuts )

– // To exclude BPD-Outliers and to ensure a well defined beam track

• beam = (T49Beam *) event->GetBeam(); if (beam->GetBPD1x() < -1.6 || beam-

>GetBPD2x() < -1.6 || beam->GetBPD3x() > 1.5 || beam->GetBPD1y() < -1.2 ||

beam->GetBPD2y() < -1.2 || beam->GetBPD3y() > 2.0) continue;

– //Iflag-cut (only "good" events; vertex-fit converged)

• vertex = (T49VertexRoot *) event->GetPrimaryVertex(); if (vertex->GetIflag()!=0)

continue;

– // The main vertex // To have the bpd- and the fitted vertex

• vertexList = event->GetVertices(); if (vertexList->GetEntries() < 2) continue;

– // Z-Vertex Cut (to select interactions in the target)

• vertexFIT = (T49VertexRoot *) vertexList->At(1); if (vertexFIT->GetZ() < -587.9 ||

vertexFIT->GetZ() > -573.4) continue;


Events cuts

• All events from 2C runs ( preproduction).

• Minidst ( 484 files )

• Number of events in all 2C runs:

– 487462


Events cuts

• Cut 1 – BPD outliers

Number of events

After cut 1:

378349


Events Cuts – Cut 2

• Vertex Iflag-cut

Number of events

After cut 1 + 2:

275722

Some kind of bad events


Events Cuts – Cut 3

• The main vertex cut

Number of events

After cut 1 + 2 + 3:

219022

BPD-vertex and vertexFit written

Only BPD-vertex written


Events Cuts – Cut 4

Z-Vertex Cut (to select interactions in the target)

Number of events

After cut 1 + 2 + 3 + 4:

202440


Events cuts summary

All Events

After Cut1

Cut 1 + 2

Cut 1+ 2 + 3

Cut 1 + 2 + 3 + 4

487462

378349 ( ~ 78 % )

275722 (~ 56 % )

219022 (~ 45 % )

202440 (~ 41 % )

Number of tracks in selected events:

807902 ( = ~ 4 tracks/event )


All tracks ( Px, Py, Pz )


H plus


H minus


P vers Theta

h +

h -

All tracks

from

selected

events


Track Cuts

• // Independent Momentum-determination //

Minimum number of found points in VTPC1+2 of 5

– if (track->GetNPoint(0) + track->GetNPoint(1) < 5)

continue;

• // Cut on ratio of measured and potential points

– Double_t ptratio = ((Double_t) track->GetNPoint()) /

((Double_t)track->GetNMaxPoint());

– if (ptratio < 0.5) continue;

• // Cut on impact parameter

– if (TMath::Abs(track->GetBx()) > 2.5) continue;

– if (TMath::Abs(track->GetBy()) > 1.5) continue;


Track Cuts

• Number of tracks in selected events:

– 807902

H minus tracks:

- 297404


Tracks Cuts - Cut 1

• Minimum number of found points in VTPC1+2 of 5


Tracks Cuts – Cut 1

• Minimum number of found points in VTPC1+2 of 5

Number of tracks

after cut 1:

266399


Track Cuts – Cut 1 + 2

• Cut on ratio of measured and potential points

Number of tracks

after cut 1 + 2 :

264367


Cut on impact parameter

Track Cuts – Cut 3


Track Cuts – Cut 1 + 2 +3

Cut on impact parameter

Number of tracks

after cut 1 + 2 + 3:

230884


MC

• 8 files ( minidst format ) from:

– /castor/cern.ch/user/a/abgra61/MC/REC/

– 8 k events.


MC overview

All particles

in MC

( not only

from main

vertex )


e-

p

π-

Charge ==-1 Charge ==1

π+

e+

K- (12)

µ+

anti p (15)


e+ and e-


MC PI-


MC h minus (from main vertex)


MC h minus reconstructed


MC h minus after cut123


Reconstructed h minus after cut123


PI- ( MCTrack->GetPid()==9)


PI- reconstructed.


To do list

• Acceptance:

– Information from „ h minus reconstructed” and

„h minus mc”

• Non pion contamination:

– Information from „PI- reconstructed” and „h

minus reconstructed”.


Conclusions

• Work in progress.

• Good MC and higher statistics

– to obtain non-pion contamination and

acceptance.


Thank you

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