Transcript Sandorfi ppt

Effective degrees of freedom in the Nucleon ?
 photo-excitation of resonances “missing” from the PDG listing
+
Issues: (1) Res + bkg divisions ~ artificial
s-ch res
u-ch
all partial waves
(2) Electromagnetic interaction is not isospin invariant
A( N  / /)I=3/2   
A( N  / /)I=1/2  N requires both n & p
(3) CQM: “gN small for all but lowest in each oscillator band”
 need N, KY channels as well  2-step  N N … important
(CC)
(4) 8 pol obs needed for A( N) & 12 for A(* N), for both N= n, p
• fitting models to incomplete-subsets of asymmetry data will produce
statements about models and endless arguments about the amplitude
• path to convincing results on the presence/absence of new states are
complete exps that (over-) determine production amplitudes
Complete experiments in pseudo-scalar meson production
p  K+
r
  H 2  K   ,P,Cx,Cz,Ox,Oz,T
r
r
r

  FROST ( H )  K   E,G,Lx,Lz,Tx,Tz
r
r r

  H D  K   E,G,Lx,Lz,Tx,Tz
r

complete
set
r r
frozen-Spin H  D - developed at BNL, migrating to JLab (?)
• high polarizations • in-beam lifetimes >> year
• very low backgrounds  clean channel separation
• factors of > 20 reduction in running-time
n  K0
r
r
r
0
  H D  K    ,E,G,P,T,Cx,Cz,Ox,Oz,Lx,Lz,Tx,Tz
- a complete set
Channel coupling requires
0p, –p
complete experiments
in
other
decay
channels,
particularly

r
r
r r
 requires   Recoil and Target  Recoil exps.  challenge