[G12] Missing mass plot for pKK -- Advice needed

[Dennis Weygand]

One more thing: 

What is mm? You never defined it.

Dennis



On Nov 12, 2009, at 5:38 PM, Mukesh Saini wrote:

> Hello all,
> 
> I am attaching a few plots and need help to understand the negative masses we get. I am using ClasEvent and bos2ntuple code to make my ntuples.
> 
> Code to make the plots:
> 
> root [30] ntp->Draw("sqrt( -mm_px**2 - mm_py**2 - mm_pz**2 + mm_t**2 ) -mm","","")
> root [31] ntp->Draw("sqrt( -mm_px**2 - mm_py**2 - mm_pz**2 + mm_t**2 ) ","","")   
> root [32] ntp->Draw("mm","","")                                                    
> 
> As you can see majority of mm is less than 0,hence I lose a lot of events when i make my cuts. The other way that I can calculate sqrt(E**2 - P**2) seems to give me the wrong answer too (All values positive even when I switch the signs on all terms inside the sqrt). I am sure this is some famous functionality that I am just unaware of. Please do let me know how to understand this and if needed fix this. 
> 
> Thanks,
> Mukesh.
> 
> Graduate Student,
> Florida State University.
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--
Dennis Weygand
weygand at jlab.org
(757) 269-5926