[G12] vertex distribution

[Michael C. Kunkel]

Greetings and thanks to all for the input


I have a few questions and comments.

To Dennis, I had thought of this, but when I plot the effective mass 
distribution of e+e- for events where MVRT are inside/outside the 
target, I get event that appear to be daltiz decays, not conversions. I 
have attached a plot to this email that shows the effective mass of the 
leptons (squared) divided by the pi0 mass (squared). The plot shows that 
for events where MVRT says are outside of the target, there is a 
distribution of mass for e+e-. If these were conversions, there would be 
no mass. From my GEMC simulations, the most a e+e- mass can be from 
conversions is 35 MeV (0.068 on the plot attached), and this is due to 
multiple scattering processes.

To Eugene, I will have to get those plots to you tomorrow. My home 
internet and Jlab are frustrating to work with.

To Michael, if these were conversions then gamma p -> p pi0 -> p gamma 
gamma ->gamma e+e-. Therefore we would still have the final state of 
e+e- gamma. A tighter cut on the effective mass or missing mass would 
not reduce a spread in x-y.

BR
MK





On 3/18/13 4:58 PM, Michael Paolone wrote:
> If this is true, tightening the missing mass = 0 and effective mass = pi0
> cuts should reduce the x-y vertex spread, right?
>
> -Michael
>
>
>> I think Dennis is correct.  This is the likely explanation.....Ken
>>
>> From: g12-bounces at jlab.org [mailto:g12-bounces at jlab.org] On Behalf Of
>> Dennis Weygand
>> Sent: Monday, March 18, 2013 4:27 PM
>> To: Michael C. Kunkel
>> Cc: g12 at jlab.org
>> Subject: Re: [G12] vertex distribution
>>
>> OK, I think I got it:
>>
>> Your e+ e- gamma sample has a large number of events such that:
>>
>> 1) pi0 --> gamma gamma
>> 2) One of the gamma's converts in material outside of the target
>>
>> MVRT still has the correct vertex since the e+ e- opening angle is 0.
>>
>> Dennis
>>
>>
>>
>>
>> On Mar 18, 2013, at 3:52 PM, Michael C. Kunkel wrote:
>>
>>
>> Greetings,
>>
>> I got my hands on PPipPim data to plot the MVRT information.
>> I have posted the plots of the r of MVRT and x vs. y of MVRT for the
>> following topologies:
>>
>> Pion; Missing Mass Proton Pi+ Pi- -> 0 (exclusive)
>>           Effective Mass Pi+ Pi- ->Omega
>>
>> Lepton: Missing Mass Proton e+ e-  < Pi0
>>               Missing Mass Proton e+ e- gamma -> 0 (exclusive)
>>               Effective Mass e+ e- gamma ->Pi0
>>
>> Plot can be found at
>> https://clasweb.jlab.org/rungroups/g7/wiki/index.php/Reconstruction_study
>> for March 18, 2013
>>
>> Before anyone cries "bug", let me assure everyone that the manner in which
>> the MVRT data is collected for the pions is the same as for leptons, i.e.
>> a clasEvent function.
>>
>>  From what I deduce, it appears that either exclusive Pi0 production can
>> happen outside of the target (cough cough), or for some reason when the
>> particle is a lepton, we have resolution problems. Neither I can
>> understand from looking at what creates the MVRT.
>>
>> Thoughts and help would be appreciated greatly.
>>
>> BR
>> MK
>>
>> On 3/13/13 3:46 PM, Dennis Weygand wrote:
>> Does anyone have  plots of vertex distributions (z, x vs y, r from MVRT)
>> for any topology?
>> Dennis
>>
>> --
>> Dennis Weygand
>> weygand at jlab.org<mailto:weygand at jlab.org>
>> (757) 269-5926 (office)
>> (757) 870-4844 (cell)
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> _______________________________________________
>>
>> G12 mailing list
>>
>> G12 at jlab.org<mailto:G12 at jlab.org>
>>
>> https://mailman.jlab.org/mailman/listinfo/g12
>>
>>
>> --
>> Dennis Weygand
>> weygand at jlab.org<mailto:weygand at jlab.org>
>> (757) 269-5926 (office)
>> (757) 870-4844 (cell)
>>
>>
>>
>>
>>
>> _______________________________________________
>> G12 mailing list
>> G12 at jlab.org
>> https://mailman.jlab.org/mailman/listinfo/g12
>>
>

-------------- next part --------------
A non-text attachment was scrubbed...
Name: inside_outside_lepton_pairs.jpg
Type: image/jpeg
Size: 18227 bytes
Desc: not available
Url : https://mailman.jlab.org/pipermail/g12/attachments/20130318/da9ef5a7/attachment-0001.jpg