Some ECC features studied with GenIma

Jean Favier OPERA Meeting Ankara 3/04/09

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Some ECC features studied with GenIma

Efficiency with no fog

Efficiencies with fog

Micro-track number versus fog

Distortions effects

Sensitivity to grain density

Compton or electrons background

Neutrino events


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• Genima GEN : GEANT3 generation of - single track (1 single field 200x200 2 , double layer emulsion

set-up) - or neutrino, showers events in a complete brick set-up. - The correct grain density is set by randomly eliminating some

GEANT track hits to obtain the m.i.p density at : 34 grains/100) IMA: single “classico” FORTRAN program: - read GEANT hits - add background fog - constructs the 32 images of grains, fog,etc present in the 2

emulsion layers - clusterises the images pixels - finds micro-track - finds base-track


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• Fog generation Random generation; fog density from 0 to 30 grains/1000 3

• Clustering

-Emulsion grain : 0.4 radius sphere

-In input, pixels not saturated; then saturation to 256 above a threshold ( about 10 % of the saturated value); for layer 1 the threshold is 20 % lower to take account of light attenuation in emulsion ( att=300 micron)).

Clusters of surface s 4 and s 64 pixels are eliminated

No digital filter (coded but not used for timing reason…)


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• Micro-tracks reconstruction

- Initialisation: 2 hits tracks are made with each cluster found in plane 1 to 7 associated with any cluster found in plane 10 to 16.

- Then try to fish other hits in the rest of planes by using roads ; road width depends of the track angle. Fog makes difficult a good evaluation of the residual sigmas

- Select tracks with 6 points and qui2 < 4.5REMARK: for the same physical track, you can obtain more than

one (ex 10) sligthly different micro-tracks. All are kept for base-tracks reconstruction


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Residuals

Fog=0

0 mrad 100 mrad

200 mrad 300 mrad

400 mrad 500 mrad

600 mrad


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Residuals

fog=8

0 mrad 100 mrad

200 mrad 300 mrad

400 mrad 500 mrad

600 mrad


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b

Widening of residuals

when fog increases


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Not well adjusted

parameters for sigmas

variation with angle


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• Base-tracks reconstruction

-Comparison in the midle plane of the intercepts and the angles of the two tried micro-tracks. x, y S1

slopex, slopey S2

S1=C/ (1-tg ) S2=D/ (1-tg )

- C= 3 micron - D=16 mrad


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Base-track efficiency

Fog=0


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• How fog can influence efficiency ?- Fog effects will be higher at large angle where the

sensible volume around the track is higher- infection of a good cluster: the resulting barycentre

becomes out of association: the hits number can go down from 6 to 5

- Deformations of good clusters by a fog one can produce a deterioration of qui2

- Oppositely, on a 5 hits track, one fog cluster can, by luck, occupy the sixth rank, so the track will be accepted


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Base-track efficiency

Fog effect


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Base-track efficiencies when fog increases


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• Distortion

It is simulated by random rotation (0 to max) of the

microtracks ,leaving fixed the intercept with the basis; we varied max from 0 to 40 mrad

Emulsion layer 1 basis


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Micro-tracks number


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Random micro and base tracks with fog

500 mrad cut

700mrad cut


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Grain

density

fog=8

0 mrad

400 mrad


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Grain

density

Fog=0 (preliminary)

Nhit 6

Nhit 5


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Emulsion simulation

• 16 images

Compton


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Compton background ( preliminary)

Hall C radio-activity is installed in GEANT3 (Borexino measurements) 1.5 108 gammas cross 1 m2 per day This reduces to 6 gammas per day crossing our field of view. In 1 years: 2000 crossing ( neglecting detector self-screening factor of

400 !!) produce: (based on 50 years stat) - 2 Compton micro-tracks2 Compton micro-tracks in each layer - 0.6-1 have grains in both layers - but: base-track association efficiency 0.05/100! This will result in much less Compton electron background

than electron from lead beta-radioactivity inside detector. ( see internal note J.F 07/10/03)


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BRICK EVENT ( preliminary)

Extension of set-up to a full brick; OK (in test)

Scanning and reconstruction OK (in test)

Actual time: 1hour (5600 cm2) for a tau-3h event

Writes micro-tracks parameters ( or clusters ? Or both? ) towards FEDRA ? EMUREC ?(Amina)

in progress….


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Tau 3 hadrons Full brick Base-tracks


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Tau 3 hadrons 3cm


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Electron 2 Gev


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Conclusions

• In simulation, no strong fog effect on efficiency. not simulated:the chemistry, stirring, etc of emulsion development!

• Strong distortion effects• Grain density : not confortable• Compton not a problem inside detector; lead

activity sould be dominant. Very low base-track efficiency for low energy electrons.

• Soon: GENIMA neutrino events in Fedra ?

Some ECC features studied with GenIma

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