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Outline Issue Want to measure MIPs 400 keV mm in Si and dense EM showers due to 250 500 GeV Bhabha
e

EM showers in W are dense: m = 021 2MeV c= 9 1 mm
R X : =E :

For EFlow, need to id. tracks at 1 cm from shower core requirement from physics simulations EGS setup Results Question of sampling layers thickness
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EGS Setup Use the G. Lindstrom recommendations for cut in thin sampling layers. Good accuracy with nite CPU time.
E

Reduced

E

cut

,

P

cut
:

in thin regions near the Si

Step size small 0 3 everywhere
~6 X 0.5 mm 0.4 mm 0.5 mm >3X

W bulk

W thin 100 keV 100 keV

Si 100 keV 20 keV

W thin 100 keV 500 keV

W bulk 500 keV 1000 keV

e

Ecut = 500 keV Pcut = 500 keV

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Si layer at depth 6
E

X

0

Initial electron e centered on a 1cm 1cm pixel Si thickness 0 4 mm
:

Typical EDEP in MeV distributions:

3


EDEP as function of e:
E

EDEP as function of depth for e =100 GeV:
E

4


Fraction of total EDEP in 1cm 1cm : e = 100 GeV
E

1. Broad shower max in depth 6 5 1
: E

X

0

2. Fraction of energy in central 1cm 1cm is independent of e

Results not sensitive to these
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EDEP MeV in 0.5 mm pixels from =3 mm: e =100 GeV, 6 0
x E X

x

= 0 to

6


EDEP fraction in center pixel as function of pixel size mm:

need big pixel size reduction to change dynamic range requirement signi cantly

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So for 1cm1 cm : 250 GeV Bhabha MIP = 340MeV 0 16MeV = 2100 11 bits +3 bits for MIP over threshold +2 bits formargin =16 bits
= :

decrease in pixel area by 100 gives 2-3 bits reduction Need to put in sampling layers; large gaps increase m:
R R

m

P =

i , m i where i is gap;
wR R z

i im

z =E

i c i Ec

is critical energy

This also degrades performance; not a good way to beat the dynamic range issue!

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