more on mass resolutions in GlueX/HallD relative to E852

[Prof Paul Eugenio <eugenio@fsu.edu>]

Hi,

I have estimated the resolutions of narrow resonances and compared these
results to known vales from E852.  Two well measured E852 narrow states
are the omega and the etaprime.  The omega signal observed in the
reaction pi- p -> n pi+ pi- 2 piz was fitted to a Gaussian with a sigma
of 19 MeV (see image e852-4pi-omega.jpg).  The etaprime was observed in
pi p -> n eta pi+ pi-. A Gaussian fit to the etaprime resulted in a
sigma of 10 MeV (see image e852-etapipi-etaprime.jpg).  In both E852
analyses a kinematic fit was performed constraining the eta and pizero
masses, and constraining the missing four-momentum mass to the neutron.

At present we have not finalized on the eta & pizero reconstruction
along with a fully constrained kinematic fit.  Because of this, the
GlueX response was esitmated by approximating the final reconstructed &
kinematically constrained etas and pizeros with the generated eta and
pizero momenta.  

Both etaprime and omega events were generated with the standard e^-5|t|
distribution.  Both angular distributions were generated isotropic. For
the charged particles, the fiducial acceptance and smearing described
earlier were used.  Eta and pizero acceptance were ignored.

The etaprime was generated with a 1 MeV BW width.  After smearing, the
etaprime signal was fitted to a Gaussian with a sigma of 7.6 MeV (E852
measured 10 MeV).   See figure in file smeared-etaprime.pdf.   

The omega was generated according to the PDG BW width of 8 MeV.  After
smearing, the convoluted width was fitted to just a Gaussian resulting
in a sigma of 15 MeV (E852 measured 19 MeV).

Paul


-- 
--
Prof. Paul Eugenio
Department of Physics
Florida State University
Tallahassee, FL  USA

850-644-2585
eugenio@fsu.edu

smeared-omega.pdf

smeared-etaprime.pdf

e852-etapipi-etaprime.jpg

e852-4pi-omega.jpg