[G14_run] Checking angle computation

[Reinhard Schumacher]

Hi All,
	After our discussion this morning, I took Haiyun's 100 events for gamma 
n to pi- p and computed the c.m. scattering angle of the pions.  I wrote 
a half-page stand-alone program to do the kinematics, and compared my 
computed angles with the values reported today from Dao's (and Tsuneo's) 
calculations.  They agreed with each other to machine accuracy, i.e. 
more than 6 decimal places.  Thus, I believe Peng has some small 
inconsistency and mistake in his calculation.

Regards,
Reinhard

______________________________________________________________________
Reinhard Schumacher         Department of Physics, 5000 Forbes Ave.
Carnegie Mellon University, Pittsburgh, PA 15213, U.S.A.
phone: 412-268-5177         web: http://www-meg.phys.cmu.edu/~schumach
______________________________________________________________________

On 02/14/2015 04:54 PM, daoh at andrew.cmu.edu wrote:
> Dear all,
>
> As you might recall from the last meeting, Peng, Tsuneo and I were tasked
> to compute the cos(pim) in the overall center of mass frame for a 100
> events supplied by Haiyun. The initial goal was to let these events go
> through momentum correction and energy correction to check for
> inconsistency. However, I realized that with only 4-vector momentum
> information for the proton, pim, and the photon, one can not do energy
> correction (need to know the interaction vertex), nor momentum correction
> (need to know the sector, the run number, etc...). As a result, I had not
> applied any correction and computed the cos(pim) directly. I assumed the
> neutron is at rest, then I boosted the pim into the photon and at-rest
> neutron rest frame. I then computed the cos(pim) with respect to the beam
> line.
>
> I attached a file with the computed values of cos(pim) with this email if
> Peng and Tsuneo want to compare.
> Sincerely,
> Dao Ho
>
>
>
>> As discussed, I attached a 100-event text file. Each event has three
>> particles: photon beam, scattered proton and scattered pi- in order.
>> Each particle occupies one line with energy, momentum in x direction,
>> momentum in y, and momentum in z. All these variables are in Lab frame.
>> There are totally 300 lines.
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