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Diffractive φ photo-production off the deuteron near the threshold in LEPS/SPring-8

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. High energy Pomeron exchange Positive energy dependence. Low energy Pseudo scalar meson exchange

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Diffractive φ photo-production off the deuteron near the threshold in LEPS/SPring-8

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

  2. High energy Pomeron exchange Positive energy dependence. Low energy Pseudo scalar meson exchange Negative energy dependence.   P, glueball,  , f2’ p Φ photo production of proton near the threshold Pure unnatural parity exchange Pure natural parity exchange Decay angular distribution φ : photon pol. Angle Φ : K decay angle.    0  0 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. 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) MWDC 3 Silicon Vertex Detector MWDC 2 MWDC 1 Detectors setup 1m

  10. Summary of data taking • Trigger condition : charged hadron track ≧ 1 • Run period • (50mm-long LH2) 2000,Dec. – 2001, June • (150mm-long LH2)2002,May - 2002.July • (150mm-long LD2) 2002,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.

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