1. M. Miyabe, K. Horie, S. Shimizu, W. C. Chang and LEPS collaboration
Diffractive φ photo-production off the deuteron near the threshold in LEPS/SPring-8
M. Miyabe, K. Horie, S. Shimizu, W. C. Chang and LEPS collaboration
Kyoto Univ.

2. Φ photo production of proton near the threshold
P, glueball,  , f2’   p
High energy
Pomeron exchange
Positive energy dependence.
Low energy
Pseudo scalar meson exchange
Negative energy dependence.
Pure natural
parity exchange
Pure unnatural
parity exchange
Decay angular distribution
φ : photon pol. Angle
Φ : K decay angle.    
φ-Φ

3. Results of proton target
Peak structure around 2GeV.
Natural parity exchange is dominant
　→　0+ glueball ?
T. Mibe, et al

4. Interest of Deuteron target
Coherent production
Interact with deuteron itself.
Incoherent production
Interact with proton or neutron in deuteron.

5. Coherent production Deuteron is isoscalar target
π exchange is strongly suppressed
Very steeper t-slope in differential cross section dσ/dt .
There are no coherent production data near the production threshold.
Really exist?
If coherent process is truly exist,
which mechanism is dominant ?

6. Incoherent production
Due to isospin effect,
gπnn and gηnn has opposite sign.
→unnatural parity exchange process is suppressed in neutron case.
Information of unnatural (π/η) exchange process

7. Experiment at Spring-8
8GeV electron storage ring
Harima Hyogo

8. BCS photon beam LEPS (Laser Electron Photon at Spring-8)
Backward Compton scattered photon beam
→ 2.4GeV maximum energy
→ high polarization photon > 90%

9. Detectors setup  Dipole Magnet(0.7T) TOF wall Start counter
Liquid Hydrogen or Deuteron Target
50mm-long
(2000 Dec.-2001June)
150mm-long
(2002May-July) 
Aerogel
Cerenkov
(n=1.03)
Silicon Vertex
Detector
MWDC 3
MWDC 1
MWDC 2 1m

10. Summary of data taking Trigger condition : charged hadron track ≧ 1
Run period
(50mm-long LH2) ,Dec. – 2001, June
(150mm-long LH2) ,May July
(150mm-long LD2) ,July – 2003 Feb, Apr-Jun
Total number of trigger
180M trigger (~50% Horizontal, ~50% Vertical pol.)
170M trigger ( same )
460M trigger ( same )

11. φ event selection
Total φ event ~ 20K

12. Existence of Coherent Missing Mass distribution of D(γ,φ)X
Red : coherent(MC)
Blue : incoherent(MC)
Black : experiment data
E2~E9 : 2.423~1.723(GeV)
→ 0.1(GeV) divided

13. Extract coherent process
Black
Experiment data
Blue
Incoherent mode (MC)
Red
(Black) – (Blue)
→　Coherent component ?
E2~2.423(GeV)
↓ 0.1(GeV) divide
E9~1.723(GeV)
Preliminary

14. Cross section of coherent
Fit with exp(b*t)
Slope b is very steep
Larger than 10
Very Preliminary

15. Summary
First find coherent production off deuteron near the threshold region.
Very steep t-slope > 10 (GeV-2)
agreement with theoretical prediction.