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S. StepanyanTown Meeting, Rutgers Univ., January 12-
14 2007
Meson spectroscopy with CLAS CLAS12
Experiments with coherent production require: detection of A’ at t’tmin (Ek>few MeV) - thin targets (~10-3 g/cm2) small size, high flux (virtual) photon beams
Coherent production on nuclei can be used to eliminate s-channel background
Successful PWA of CLAS photoproduction data showed a feasibility of meson spectroscopy studies using the CLAS detector
It also reviled importance of backgrounds from ’s and N*’s
CLAS(12) with BoNuS RTPC and with available high precision, high intensity electron beams opens a new avenue for meson spectroscopy using coherent production on nuclei
a2
CLAS/g6: p’n++-
Background from s-channel processes complicates PWA (need a high statistics data), introduces ambiguities
S. StepanyanTown Meeting, Rutgers Univ., January 12-
14 2007
Coherent production of 0 and 0’ on 4He (PR-07-009)
Only C=-1 -exchanges is allowed, Natural Parity Exchange (NPE)
The helicity of the produced state will be that of the incoming photon, =, production of 0 (0’) in S-wave is forbidden
22
0
AAAd
d
C
),(Im212 0
2/1max
0 1
LL
L
L
DLLA
;0;00 AA
),(Im212 101
2/1max
1
LL
L
DLLA
Final states 0 and 0’ have I=1, C=+1, G=-1, and P=(-1)l. Resonance in the P-wave will be an exotic - IGJPC = 1-1-+
Coherent production on 4He eliminates s-channel contribution
Scattering off of the spin and isospin zero target works as a spin and parity filter for final state mesons
2
2
2111 sin)1cos5(
2
5cos53
FDPd
d
C
S. StepanyanTown Meeting, Rutgers Univ., January 12-
14 2007
CLAS12 with thin targets (3H, 3He, 4He) and with small angle tagger
1
22
22
)2(tan21
Q
Q
LL
L
0)1(2
1
0)1(2
10
)1(2
10)1(
2
1
2/1
2/1
010 32
2
QL
Spectroscopy can be extended to the higher masses (~3 GeV) and to the charged modes
Electroproduction at very small Q2’10-3, scattering angles 1o-2o, is equivalent to photoproduction with partially linearly polarized photons, complimentary solution to photon bremsstrahlung beams