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option of polarization for Lambda-Lambdabar model [message #16335] Wed, 16 April 2014 11:48 Go to next message
donghee is currently offline  donghee
Messages: 385
Registered: January 2009
Location: Germnay
first-grade participant
From: *kph.uni-mainz.de
Hi,

I am using a model EvtLambdaLambdaBarPol in EvtGen/Private to generate artifitial polarization.

Decay pbarpSystem
1.0 anti-Lambda0 Lambda0 LambdaLambdaBarPol 1.64 0.5;
Enddecay

In principle, we can give a polarization value for lambda and lambdabar with last of option, which is set to 0.5 in this example.
This way one can introduce the polarization vector n perp to scattering plane.

I could not see any changing of angular distribution in n direction, which is a quantized axis used in the measurement of hyperon polarization. When I set 0.5 and 0.0, angular distributions are same for both. That means that this option value is not correctly working for generating the polarizaiton.
Does anyone know how can I introduce a polarization with this model? or most likely you can assume that the coordinate systems are not properly lorentz-boosted and thus I cannot see any slop due to that reason.

Best wishes,
Donghee



Re: option of polarization for Lambda-Lambdabar model [message #16337 is a reply to message #16335] Wed, 16 April 2014 12:26 Go to previous message
StefanoSpataro is currently offline  StefanoSpataro
Messages: 2736
Registered: June 2005
Location: Torino
first-grade participant

From: *to.infn.it
This model changes only the spin density, not the angles. If you let Lambdas decay with phase space most probably this information is lost.
I don't know how was used this model, Jan Zhong added the polarization part, maybe Bertram knows better.
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