b1pi plots (fwd)

[Elke-Caroline Aschenauer <elke@jlab.org>]

Dear Curtis,

as promised today Alex S. did studies on the acceptance for
gamma p -> X(2000) p
           X -> b1(1235)+ pi-

the plots as he describes are on his www-page
http://www.jlab.org/~somov/b1pi_accept/
I think they are a nice addition to the acceptance plots comparing E852
and GlueX from Alex D. you have already in your talk.

Cheers elke



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---------- Forwarded message ----------
Date: Mon, 24 Mar 2008 14:20:56 -0400 (EDT)
From: Alexander Somov <somov@jlab.org>
To: Elke-Caroline Aschenauer <elke@jlab.org>
Subject: b1pi plots


Dear Elke,

Here are some acceptance plots
(I put them to /home/somov/public_html/b1pi_accept)

gamma p -> X(2000) p
           X -> b1(1235)+ pi-
                  |
		   -> omega pi+
                        |
                        -> pi+ pi- pi0


The plots are obtained using GEANT simulation.
For charged tracks I simply count the number of MC impact
points with the wire layers (MCTrackHit factory).

For pi0s I used:
 a) MCTrackHit information (I also match gamma's thrown angles,
   phi and theta, with the hit angles stored in MCTrackHit
   factory. Note that this factory contains primary and all
   secondary hits. I don't do any cell hit energy match here)

 b) thrown gammas are matched with the reconstructed photons
   (here, I compare angles and energy as well).


1. b1pi_nhits.eps
Acceptance as function of the number of hits per track in the
CDC+FDC.

2. b1pi_cos.eps
Acceptance as function of Gottfied-Jackson angle.
I also prepared a slide (b1pi_cos1.eps ) without "pi0 reconstructed"
events - just acceptance for charged tracks and pi0 within acceptance.


3.  b1pi_mass.eps
Acceptance as function of the X meson mass.
I generated mc samples for different X meson masses assuming
the t-channel slope = 5.0 (I can also check acceptance by generating
events with the different t slope (?) - can be done very quickly).

Please let me know what else plots might be interesting here
(lipe p/pi kinematics,...).

I can aslo put slides to the public area to get a feedback from
people (people might have done a lot of similar studies).



Cheers,
       Alex