Preliminary results of separation from data tracks 1.Outline 2.Comparison of cosmics in both…

Preliminary results of separation from data tracks

1. Outline2. Comparison of cosmics in both

bricks3. and tracks4. Separation with NN5. Conclusion, TBD

OPERA Collab. Meeting GS May 2005

Thomas Waelchli LHEP Uni Bern

•Data from 2nd PSI-TB June 2004•Pion beam: 202MeV/c, ( contamination <1%)•Muon beam: 120MeV/c, (e contamination <5%)•2 bricks ( 30 cells, : 50 cells)

•Goal: –Follow tracks until they stop–Develop simple method for identification based on ‘normal scanning’ (16 layers/emulsion)–Fill NN with MCS angles, scattering coord., (dE/dx)

•2x5cm2 (), 3x3cm2 () scanned, outside beam-spot•Tracks reconstructed with FEDRA

–Using 200MeV/c for Kalman filter–Standard instrumental precision

1. OUTLINE

T. Waelchli, OPERA Collab. Meeting GS May 2005

T. Waelchli, OPERA Collab. Meeting GS May 2005

FINDING COSMICS…CUTS: {((nseg>10 && n0<=3) || npl>(N-3)) && t.eFlag>=0

&& track starts in 1st or 2nd emulsion&& (nseg-10) < 0.6}N: number of cells in brick

t.eP

t.eP

t.eP > 0.7

2. COSMICS IN BOTH BRICKS

T. Waelchli, OPERA Collab. Meeting GS May 2005

segi segi+1

iXi

Pb

beam

i

Average MCS angle:

av=i*cos(i)/nseg)

Average MCS coordinate: Xav=Xi*cos(i)/nseg)

Xav Xav same in and brick

Instrumental precision ca. 3mmuon brickpion brick

0muon brickpion brick

avmuon brickpion brick

T. Waelchli, OPERA Collab. Meeting GS May 2005

2. COSMICS IN BOTH BRICKS-brick is shorter larger angle of incidence 0 possible

av ca. 2mrad smaller in -brick possible thru ….

But av identical No bias

av/0

muon brickpion brick

3.AND TRACKS

707 227

T. Waelchli, OPERA Collab. Meeting GS May 2005

CUTS: {nseg>=10 && n0<=3 && npl<(N-3) && t.eFlag>=0 && t.eP<0.3 && track starts in 1st or 2nd emulsion&& (nseg-10) < 0.6}N: number of cells in brick

T. Waelchli, OPERA Collab. Meeting GS May 2005

3.AND TRACKS

avmuonspions

Xavmuonspions

av and Xav only average definednumber of cells before the end of a track.

-Good separation already ‘from eye’

-bla

-bla

-bla

T. Waelchli, OPERA Collab. Meeting GS May 2005

3.AND TRACKSs.eVolumeav

s.eVolumeav

s.eVolumeav

s.eVolumeavmuonspionsmuons

cosm.

pionscosm.

cosm. ()cosm.

....

NN with 2 (3) input neurons

INPUT LAYER: 2 (3) neurons filled with av , Xav and (eVolav)

HIDDEN LAYER with 2 (3) neuronsOUTPUT LAYER with 1 neuron:

“0” for muon“1” for pion

typical NN output

T. Waelchli, OPERA Collab. Meeting GS May 2005

Xav

IN HID OUT

orav

eVolav( )

Many different configurations tested:

•Varying number of cells

•Omitting cells at end of a track

Best efficiency is 85% using 9 cells, omitting the last.

Conclusion and TBD• Separation capability of data tracks up to

85% with less than 10 available segments

• TO BE DONE:• Improve / fine-tune simulation• (include dE/dx into NN)• Check mixing/ambiguities of FEDRA

reconstructed tracks as function of density with simulation

T. Waelchli, OPERA Collab. Meeting GS May 2005