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