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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. Gen ima GEN : GEANT3 generation of - PowerPoint PPT Presentation
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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
Jean Favier OPERA Meeting Ankara 3/04/09
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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
Jean Favier OPERA Meeting Ankara 3/04/09
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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…)
Jean Favier OPERA Meeting Ankara 3/04/09
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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
Jean Favier OPERA Meeting Ankara 3/04/09
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Residuals
Fog=0
0 mrad 100 mrad
200 mrad 300 mrad
400 mrad 500 mrad
600 mrad
Jean Favier OPERA Meeting Ankara 3/04/09
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Residuals
fog=8
0 mrad 100 mrad
200 mrad 300 mrad
400 mrad 500 mrad
600 mrad
Jean Favier OPERA Meeting Ankara 3/04/09
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Not well adjusted
parameters for sigmas
variation with angle
Jean Favier OPERA Meeting Ankara 3/04/09
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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
Jean Favier OPERA Meeting Ankara 3/04/09
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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
Jean Favier OPERA Meeting Ankara 3/04/09
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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
Jean Favier OPERA Meeting Ankara 3/04/09
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Random micro and base tracks with fog
500 mrad cut
700mrad cut
Jean Favier OPERA Meeting Ankara 3/04/09
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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)
Jean Favier OPERA Meeting Ankara 3/04/09
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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….
Jean Favier OPERA Meeting Ankara 3/04/09
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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 ?