CDC length and the backward coverage

[Eugene Chudakov <gen@jlab.org>]

At Elke's request I looked for processes that would need a CDC
coverage for theta>90 deg. I considered the reaction:
gamma p --> M B, d(sigma)/dt ~ exp(5t),
where M could be a light meson (omega) or a heavy meson at 1.8GeV,
and B is eigher p, Delta+(->p pi0) or Delta0 (->p pi-)
I required that the recoil proton, or the charged products of the recoil
baryon would reach a radius R>22 cm, in which case there is a chance
to use the CDC.

process            theta limit          % of events
X(1800) p      : theta(p)   > 55 deg   0% of events
omega   p      : theta(p)   > 75 deg   0% of events
X(1800) Delta+ : theta(p)   > 50 deg   0% of events
X(1800) Delta0 : theta(p)   > 50 deg   0% of events
               : theta(pi-) >145 deg   1% of events
               : theta(pi-) >120 deg   5% of events
               : theta(pi-) >102 deg  10% of events
omega   Delta0 : theta(p)   > 50 deg   0% of events
               : theta(pi-) >153 deg   1% of events
               : theta(pi-) >130 deg   5% of events
               : theta(pi-) >115 deg  10% of events

Protons need a coverage of theta<80 deg. However,
pions from Delta0 decays go backwards to about 130 deg. The latter process
involves a charge exchange and may be nor very significant for the main
GLUEX program.


Eugene