| Re: EvtGen Output Fixed Point Precision [message #9008 is a reply to message #9007] |
Thu, 16 July 2009 18:07   |
Marius Mertens
Messages: 55
Registered: January 2009
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continuous participant |
From: *ikp.kfa-juelich.de
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Hi Stefano,
one example I just took from an event file looks like this:
Toggle Spoiler
8 24
N Id Ist M1 M2 DF DL px py pz E t x y z
0 88888 2 -1 -1 1 2 0.0001 -0.0000 9.8081 10.7911 0.0000 0.0000 0.0000 0.0000
1 431 2 0 0 3 4 -0.1031 0.1937 6.0957 6.4094 0.0000 0.0000 -0.0000 0.0000
2 -10431 2 0 0 9 10 0.1032 -0.1937 3.7124 4.3817 0.0000 0.0000 -0.0000 0.0000
3 331 2 1 1 5 6 0.1644 -0.2514 1.6517 1.9331 0.5596 -0.0090 0.0169 0.5322
4 211 1 1 1 -1 -1 -0.2675 0.4451 4.4439 4.4764 0.5596 -0.0090 0.0169 0.5322
5 113 2 3 3 7 8 -0.2246 -0.2185 1.0231 1.1931 0.5596 -0.0090 0.0169 0.5322
6 22 1 3 3 -1 -1 0.3890 -0.0329 0.6286 0.7399 0.5596 -0.0090 0.0169 0.5322
7 211 1 5 5 -1 -1 -0.2382 -0.0779 0.2085 0.3546 0.5596 -0.0090 0.0169 0.5322
8 -211 1 5 5 -1 -1 0.0137 -0.1406 0.8147 0.8385 0.5596 -0.0090 0.0169 0.5322
9 -431 2 2 2 11 12 -0.1946 -0.0838 3.2330 3.7911 0.0000 0.0000 0.0000 0.0000
10 111 2 2 2 22 23 0.2978 -0.1098 0.4794 0.5906 0.0000 0.0000 0.0000 0.0000
11 331 2 9 9 13 15 0.0849 0.2089 0.6670 1.1896 0.1595 -0.0082 -0.0035 0.1361
12 -211 1 9 9 -1 -1 -0.2796 -0.2927 2.5660 2.6015 0.1595 -0.0082 -0.0035 0.1361
13 111 2 11 11 16 17 0.0688 0.1769 0.3666 0.4343 0.1595 -0.0082 -0.0035 0.1361
14 111 2 11 11 18 19 0.0061 0.0425 0.0925 0.1691 0.1595 -0.0082 -0.0035 0.1361
15 221 2 11 11 20 21 0.0101 -0.0104 0.2079 0.5861 0.1595 -0.0082 -0.0035 0.1361
16 22 1 13 13 -1 -1 0.0887 0.1447 0.3570 0.3953 0.1595 -0.0082 -0.0035 0.1361
17 22 1 13 13 -1 -1 -0.0199 0.0322 0.0096 0.0390 0.1595 -0.0082 -0.0035 0.1361
18 22 1 14 14 -1 -1 -0.0405 0.0659 0.0199 0.0798 0.1595 -0.0082 -0.0035 0.1361
19 22 1 14 14 -1 -1 0.0465 -0.0234 0.0726 0.0893 0.1595 -0.0082 -0.0035 0.1361
20 22 1 15 15 -1 -1 -0.2346 -0.0364 -0.0355 0.2400 0.1595 -0.0082 -0.0035 0.1361
21 22 1 15 15 -1 -1 0.2447 0.0259 0.2434 0.3461 0.1595 -0.0082 -0.0035 0.1361
22 22 1 10 10 -1 -1 0.2973 -0.1216 0.4813 0.5786 0.0000 0.0000 0.0000 0.0000
23 22 1 10 10 -1 -1 0.0005 0.0118 -0.0019 0.0120 0.0000 0.0000 0.0000 0.0000
When you calculate the mass of particle 4, it evaluates to 142.266MeV.
The maximum error in mass due to rounding at 4 digits precision is
err_max=0.05MeV*(E+px+py+pz)/sqrt(E^2-px^2-py^2-pz^2)
It is admittedly not very likely that the maximum error is indeed achieved, but it does happen.
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