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Invariant Mass Distribution Widening after 4C Fit [message #18356] Wed, 08 July 2015 09:37 Go to previous message
André Zambanini is currently offline  André Zambanini
Messages: 17
Registered: February 2012
Location: FZ Jülich
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Hi everyone,

during my investigation of cascade reconstruction with PandaRoot, I found that after the four-constraint fitter my mass resolution got worse. You can see the difference in the plot I attached. Shown are the invariant mass distributions after applying a cut on the probability (>0.01) of the four-constraint fit, once with the pre-fit values (blue) and once with the values after the fit (green).

My decay is p̅p → Ξ̅Ξ → Λ̅π⁺ & ΛK⁻ with Λ → π⁻p and Λ̅ → π⁺p̅. So in my reconstruction I'm dealing with neutral particles (Λ). I asked a bit around here in the institute and it seems, others see a similar effect when having a mixture of neutral and charged candidates as input to the 4C fitter.

I'm running with trunk r27694 but it has been seen from others here with scrut14 as well. More details like a minimal running example will follow as soon as I have concluded my thesis, which is due in the next days. In the meantime: did anyone else see something like this? If so, is there an explanation to that?


PS: The mass values are taken from the PndRhoTupleQA method qaCand().

  • Attachment: dm_xi.png
    (Size: 94.07KB, Downloaded 624 times)

[Updated on: Wed, 08 July 2015 09:40]

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