Pion Decay

Special Geometry

run a simplified geometry with only the pipe, TPC, FTPC and SVT

Here we are looking for the decay of 250 events, each event consist of one pi+ and one pi- with exactly the same momenta p, emerging from the vertex at a polar angle of 89 deg or 70 deg and azimuthal angle of 0 deg. The idea is to look at the same 250 events with different degree of physics mechanism. We used physics None2(LOSS), None3(LOSS + DCAY). See Standard Settings

Below shows the reconstructed hits and momenta spectra for the TPC at 0.2GeV/c, 0.5GeV/c, 1.0GeV/c and 2.0GeV/c, for two cases (89 deg and 70 deg) by applying fast simulation (TFS) in bfc.C

89 degree

p=0.2GeV/c (250 Events) TPC hits none2 TPC hits none3 TPC tracks none2 TPC tracks none3 TPC tracks none2 (full spectra) TPC tracks none3 (full spectra)

p=0.5GeV/c (250 Events) TPC hits none2 TPC hits none3 TPC tracks none2 TPC tracks none3 TPC tracks none2 (full spectra) TPC tracks none3 (full spectra)

p=1.0GeV/c (250 Events) TPC hits none2 TPC hits none3 TPC tracks none2 TPC tracks none3 TPC tracks none2 (full spectra) TPC tracks none3 (full spectra)

p=2.0GeV/c (250 Events) TPC hits none2 TPC hits none3 TPC tracks none2 TPC tracks none3 TPC tracks none2 (full spectra) TPC tracks none3 (full spectra)

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70 degree

p=0.2GeV/c (250 Events) TPC hits none2 TPC hits none3 TPC tracks none2 TPC tracks none3 TPC tracks none2 (full spectra) TPC tracks none3 (full spectra)

p=0.5GeV/c (250 Events) TPC hits none2 TPC hits none3 TPC tracks none2 TPC tracks none3 TPC tracks none2 (full spectra) TPC tracks none3 (full spectra)

p=1.0GeV/c (250 Events) TPC hits none2 TPC hits none3 TPC tracks none2 TPC tracks none3 TPC tracks none2 (full spectra) TPC tracks none3 (full spectra)

p=2.0GeV/c (250 Events) TPC hits none2 TPC hits none3 TPC tracks none2 TPC tracks none3 TPC tracks none2 (full spectra) TPC tracks none3 (full spectra)

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Results

P (GeV/c)	Angle (deg)	# Pions (No DCAY)	# Pions (DCAY)	Fraction
0.2	70	500	425	0.850
0.2	89	500	435	0.870
0.5	70	500	463	0.926
0.5	89	500	465	0.930
1.0	70	500	484	0.968
1.0	89	500	472	0.944
2.0	70	500	490	0.980
2.0	89	500	485	0.970

Fraction = #Pions(DCAY) / #Pions(No DCAY)

The colored points represent the Fraction of pions of mass m=0.140 (GeV) surviving after a distance d which is given by :
N/No = exp(-d*m/(p*ctau)) , ctau(pions) =7.8 m.

The open circles represent the measured simulated fraction, see above table

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For more information about the standard settings of the events click here

For more information about the kinematics of the events click here

THIS PAGE IS ALWAYS UNDER CONSTRUTION

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