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# Differences

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man:science:physics [2013/05/04 08:49]
man:science:physics [2013/05/31 16:11] (current)
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+
+====== Particle Physics ======
+{{keywords>​particle Lorentz vector}}
+
+====== Showing data from HepData database ======
+
+The best approach is to download "​scavis"​ Jython script from [[http://​durpdg.dur.ac.uk/​|Durham HepData database]] and run it in the SCaVis editor or as a batch script. This is the best supported approach which also allows to deal with statistical and systematical errors separately since data are imported to the P1D object. You can further modify P1D graphical attributes or replace HPlot canvas with other canvaces (like HPlotJa). You can also combine statistical and systematical errors using the methods of the P1D class. ​
+
+====== Lorentz representation of a particle ​ ======
+{{tag>​Lorentz decay particle}}
+
+You can represent a relativistic particle using a Lorentz representation. Use the class [[/​scavis/​api/​doc.php/​hephysics/​particle/​LParticle.html | LParticle]] which defines a particle in terms of the four-Lorentz vector. A particle is characterized by either (px,​py,​pz,​E) or (x,​y,​z,​time). ​
+
+For example, below we define a "​top"​ quark with the mass 170 GeV and with the momentum pZ=400 GeV
+<code python>
+from hephysics.particle import *
+Top=LParticle("​top quark",​170)
+Top.setV3( 0,0,400 )
+print Top.toString()
+</​code>​
+
+
+Now we are ready to go with a small Monte Carlo simulation for decay of the top particle.
+Below we calculate the maximum opening angle between its decay products
+
+<code python 1|t Wdecays.py >
+extern> Wdecays.py
+</​code>​
+
+The output of the code is below:
+{{wdecay.png?​400|}}
+
+<note warning>​Under construction</​note>​