1. φphotoproduction from nuclear targets T.Sawada LEPS Collaboration Meeting in Academia Sinica, 2008.5.1

2. φ properties with A-dependence ・ Modification studied by invariant mass spectra ・ Modification stdudied by A-dependence of the photo-production dilepton: difficulty in the treatment of the background. KK: distortion by the KN and KN interactions. Mass Number A Cross Section The modification of the spectral function implies the change of the pole position and the width. When the effective in-medium width of the φ-meson becomes larger, then its decay probability also increases, leading to a stronger absorption in nuclear matter. Thus, one might expect that the A-dependence indicates a in-medium modification of the imaginary part of the phi-meson spectral function. Within the Glauber formalism, we will analyze the φ-photoproduction data from nuclei and evaluate the in-medium φ-N cross section.

3. φ- N total cross section φ- N total cross section in free space Quark model : 13.0mb VDM relation : 7.7 - 8.7mb at E γ = 4.6 - 6.7GeV φ photo-production from nuclei at E γ = 1.5 - 2.4 GeV at forward angles (incoherent) T. Ishikawa et al., Phys. Lett. B608: 215-222(2005) 35 mb +17 -11 Large φ-N interaction (σ φN =35mb) is obtained. This result implies that the φ-N interaction is stronger than theoretical estimations due to the modification of the φ properties in the nuclear medium. Introduction

4. Experimental setup at SPring-8/LEPS 1.5 Previous experiment (T. Ishikawa et al. Phys.Lett.B608:215-222,2005. ) This experiment A systematic study over several kinematical region is very useful for a physical interpretation! γ γ γ K±K± K±K± K±K± K ± K ± K ±

5. θ the cross section of the incoherent φ-meson photoproduction with Angular dependence in the Glauber model ・ Eikonal approximation ( emission angle θ relative to γ-momentum = 0°) ・ The total reaction amplitude is built up from a sum of amplitudes on a single nucleon. ・ The incident particle is assumed to interact independently with each target nucleon. ・ The particle moves along a straight line trajectory through the nucleous. ・ Angular dependence ( in the case of θ≠0°) particle i (or photon) particle f the Eikonal formalism has been considered to Extract the in-medium properties of hadrons from the A-dependence of their production on nuclei. ・ In this experiments, the data are collected at a certain angular range determined by the detector acceptance. ・ A-dependence is effected by the emission angle. -> We need to estimate how much it is effected. azimuthal angle φ= 0° azimuthal angle φ= 180° θ σiσi σfσf nucleus nucleon θ= 0 °

6. ρ A (r) : a nuclear density function taken as a Wood-Saxon distribution. θ : the emission angle of the φ-meson relative to γ-momentum The last integration in equation being over the path of the produced φ-meson φ : the azimuthal angle of the φ-meson S i ; the attenuation probability of an i particle passing through the nucleus. (b is impact parameter) S f ; the attenuation probability of an f particle passing through the nucleus. J. Knoll, J. Randrup Nucl.Phys.A324: 445,1979. J. Blocki, J. Randrup, W.J.Swiatecki, and C.F.Tsang, Annal phys. 105, 427-462(1977) M. Effenberger, A. Sibirtsev Nucl.Phys.A632:99-108,1998. A. Sibirtsev, H.-W. Hammer, U.-G. Meissner,arXiv:0802.3373 [nucl-th] at θ= 0°limit The effective nucleon number A eff the cross section of the incoherent φ-meson photoproduction with Angular dependence in the Glauber model

7. The slope of the A α -dependence fitted to the effective nucleon numbers(H,C,Cu) calculated using the above equation, for σ i =0.14mb as a function of σ f. It is shown for the different emission angles; θ= 0°(black), θ= 30°(blue), θ= 60°(purple), and θ= 90°(red). Estimation of the effective nucleon number N eff and the slope parameter α 0 10 20 30 40 50 60 σ f [mb] 1 0.2 0.4 0.6 0.8 slopeα The effective nucleon number A eff calculated using the above equation for H, C, and Cu nuclei and σ i =0.14mb as a function of σ f. It is shown for the different emission angles; θ= 0°(black), θ= 30°(blue), θ= 60°(purple), and θ= 90°(red). 1 10 10 2 NANA

8. π-π- π+π+ p d K-K- K+K+ dE/dx (arb.) momentum/charge (GeV/c) TPC track ( polar angle > 25. deg ) γ K±K± K ± γ K±K± K ± Analysis both Kaon are identified by TPC. one Kaon is identified by forwared spectrometer, and another one is detected by TPC. Analysis ( now, only required charge information) (use polar angle>25 degree track) + -

9. TPC K+ & TPC K- number of tracks in TPC positive charged track >=1 && negative charged track >=1 track quality ; chi-square probability > 0.02 for good de/dx performance; numhits in track >= 6 polar angle > 25 deg vertex quality ; cdist < 4. target selection Track cut Event selection Vertex cut PID K+ & PID K-

10. chi-square probability cut : chi2prb > 0.02 number of hits in track : numhits >= 6 polar angle cut : polang > 25 deg. run30000 (CH2) run30700 (C)run30200 (Cu) track cut TPC K+ & TPC K- 01 010

11. closest distance < 4. target selection ; sqrt(vtx**2+ vty**2) < 14. target selection of vertex z vertex cut run30000 (CH2) run30700 (C)run30200 (Cu) TPC K+ & TPC K-

12. invariant mass spectra of K+ K- from each targets invariant mass(K + K - ) GeV/c 2 Counts / 0.002 GeV/c 2 invariant mass(K + K - ) GeV/c 2 CH 2 targetC targetCu target 683±77 events397±57 events 117±23 events TPC K+ & TPC K- Height = 87.2±6.3 Mean = 1017±0 MeV Sigma = 6.2±0.5 MeV χ 2 /ndf = 62.16 / 38 Height = 50.2±6.3 Mean = 1016±1 MeV Sigma = 6.3±0.7 MeV χ 2 /ndf = 32.29 / 38 Height = 22.2±3.4 Mean = 1018±1 MeV Sigma = 4.2±0.6 MeV χ 2 /ndf = 51.51 / 43 0.95 1 1.05 1.1 1.15 1.2 0 20 40 60 80 0 40 80 120 160 0 10 20 30 40

13. black : CH 2 red : C (scaled by the number of photon) invm (K + K - ) [GeV] | invm(KK) – Mφ| <0.02 GeV | MM(KK) – Mp | < 0.1 GeV black : CH 2 red : C free proton (CH 2 - C) Counts / 0.02 GeV/c 2 Counts / 0.004 GeV/c 2 missing mass and invariant mass spectra of K+ K- from free proton TPC K+ & TPC K- free proton (CH 2 - C) MissingMass (K + K - ) [GeV] 0 11.4 0.20.40.60.8 1.2 0.951 1.051.1 1.151.20.951 1.051.1 1.151.2 0 11.4 0.20.40.60.8 1.2 H C Cu arb. MissingMass (K + K - ) [GeV] 011.40.2 0.40.60.8 1.2 Monte Carlo invm (K + K - ) [GeV] 0 20 40 60 50 30 10 0 20 30 40 0 20 40 60 -20 -10 50 30 10 -10 0 20 40 60 50 30 10 70

14. momentum of phi at Lab-flame [GeV/c] free proton (CH 2 -C) polar Angle at CM-system [deg] t + |t|min [GeV 2 ] forward backward 012 0-2-3-4 018060 120 kinematics of phi | invm(KK) – Mφ| <0.02 GeV && | MM(KK) – Mp | < 0.1 GeV TPC K+ & TPC K- 14 black : CH 2 red : C (scaled by the number of photon) 12 momentum of phi at Lab-flame [GeV/c] polar Angle at CM-system [deg] 018060120 0-2-3-4 t + |t|min [GeV 2 ] Counts / 0.2 GeV 2 Counts / 10 deg Counts / 0.1 GeV/c MC (proton) polar Angle at CM-system [deg] 018060120 0 12 momentum of phi at Lab-flame [GeV/c] 0 0 0 40 80 100 60 20 0 0 10 20 30 40 -10 0 10 20 30 40 -10 0 10 20 30 40 -10 40 80 60 20 40 60 20

15. mass/charge spectrum in spectrometer after K + K - PID(in tpc) mass/charge [GeV/c 2 ] invm(K + K - ) invm(K - p) invm(K + K - ) invm(K - p) p K- K+ Counts / 0.033 GeV/c 2 Counts / 0.04 GeV/c 2 Counts / 0.06 GeV/c 2 (CH 2 target data) phi(1020), L(1520) in KKp identified events TPC K+ & TPC K- φ→KKp Λ(1520)→KKp non-resonant KKp 012 1.3 1.4 1.5 1.6 1.7 1.8 1.9 0.9 1 1.1 1.2 1.3 1.3 1.4 1.5 1.6 1.7 1.8 1.9

16. spectrometer & TPC number of tracks in TPC >=1 track quality cut ; chi-square probability > 0.02 target selection vtz & cdist < 4. PID Kaon K decay-in-flight rejection ; chi-square probability > 0.02 Target selection by z of vertex number of tracks in spectrometer >=1 Event selection LEPS track cut TPC track cut not required PID ( only charge ) spectrometer & tpc

17. K+ selection chi2 vtz chi2prob > 0.02 -1656 < vtz < -1386 spectrometer track cut (K+ ) spectrometer & tpc

18. K- selection chi2 vtz chi2prob > 0.02 -1656 < vtz < -1386 spectrometer track cut (K- ) spectrometer & tpc

19. sqrt(vtx**2 + vty**2) <25 -1570< vtz <-1400 chi2 prob > 0.02 spectrometer & tpc

20. Counts/0.002GeV/c 2 invariant mass(K + K - ) GeV/c 2 forward spectrometer K + & TPC K - event CH 2 target C target Cu target Counts/0.002GeV/c 2 invariant mass(K + K - ) GeV/c 2 Cu targetC targetCH 2 target 937±100 events 390±63 events 176±84 events 844±98 events 182±41 events386±53 events invariant mass spectra of K+ K- from each targets spectrometer & tpc Height = 126.7±8.5 Mean = 1022±0 MeV Sigma = 5.9±0.5 MeV χ 2 /ndf = 17.79 / 20 Height = 59.2±6.3 Mean = 1021±1 MeV Sigma = 5.3±0.9 MeV χ 2 /ndf = 29.97 / 20 Height = 15.1±3.2 Mean = 1020±0 MeV Sigma = 9.3±4.0 MeV χ 2 /ndf = 20.94 / 20 Height = 97.2±6.5 Mean = 1024±1 MeV Sigma = 9.0±0.7 MeV χ 2 /ndf = 37.23 / 25 Height = 50.4±4.5 Mean = 1024±1 MeV Sigma = 6.1±0.6 MeV χ 2 /ndf = 37.59 / 25 Height = 15.9±2.0 Mean = 1026±1 MeV Sigma = 9.2±0.2 MeV χ 2 /ndf = 16.12 / 25 0 100 200 300 400 500 600 0.95 1 1.05 1.1 1.15 1.2 10 20 30 0 20 40 60 80 100 forward spectrometer K - & TPC K + event 0 40 80 120 160 200 0 100 200 300 40 80 120 20 60 100 5 15 25

21. spectrometer K+ & TPC K- Invariant Mass (K + K - ) free proton (CH 2 -C) black : CH 2 red : C (scaled by the number of photon) Cut: | invm(KK) – Mφ| <0.02 GeV Cut: | MM(KK) – Mp | < 0.1 GeV Counts / 0.02 GeV/c 2 Counts / 0.004 GeV/c 2 free proton (CH 2 -C) black : CH 2 red : C missing mass and invariant mass spectra of K+ K- from free proton Missing Mass (K + K - ) 0 0.2 0.4 0.6 0.8 1 1.2 1.4 Missing Mass (K + K - ) 0 0.2 0.4 0.6 0.8 1 1.2 1.4 0.95 1 1.05 1.1 1.15 1.2 Invariant Mass (K + K - ) 0.95 1 1.05 1.1 1.15 1.2 0 40 80 120 160 200 0 40 80 -40 100 200 300 400 500 0 50 100 150 -50 0

22. forward backward 01 2 polar Angle at CM-system [deg] 018060 120 t + |t| min [GeV 2 ] 0 -2-3-4 free proton (CH 2 -C) black : CH 2 red : C momentum of phi at Lab-flame[GeV] | invm(KK) – Mφ| <0.02 GeV && | MM(KK) – Mp | < 0.1 GeV kinematics of φ spectrometer K+ & TPC K- Counts / 0.2 GeV 2 Counts / 10 deg Counts / 0.1 GeV/c MC (proton) Cut: 012 momentum of phi at Lab-flame[GeV] 01 2 polar Angle at CM-system [deg] 018060 120 polar Angle at CM-system [deg] 018060120 t + |t| min [GeV 2 ] 0 -2-3-40-2-3-4 0 200 400 600 0 100 200 50 150 250 0 100 200 50 150 0 40 80 60 20 -20 100 300 500 100

23. spectrometer K- & TPC K+ black : CH 2 red : C free proton (CH 2 - C) Cut: | invm(KK) – Mφ| <0.02 GeV Cut: | MM(KK) – Mp | < 0.1 GeV Counts / 0.02 GeV/c 2 Counts / 0.004 GeV/c 2 missing mass and invariant mass spectra of K+ K- from free proton Missing Mass (K + K - ) 0 0.2 0.4 0.6 0.8 1 1.2 1.4 Missing Mass (K + K - ) 0 0.2 0.4 0.6 0.8 1 1.2 1.4 Invariant Mass (K + K - ) 0.95 1 1.05 1.1 1.15 1.2 Invariant Mass (K + K - ) 0.95 1 1.05 1.1 1.15 1.2 0 40 80 120 0 40 80 120 160 0 0 40 80 -40 40 80 120

24. momentum of phi at Lab-flame[GeV] forward backward polar Angle at CM-system [deg] 018060120 t + |t| min GeV 2 0 -2-3 -4 black : CH 2 red : C free proton (CH 2 - C) 012 | invm(KK) – Mφ| <0.02 GeV && | MM(KK) – Mp | < 0.1 GeV spectrometer K- & TPC K+ Kinematics of φ Counts / 0.2 GeV 2 Counts / 10 deg Counts / 0.1 GeV/c MC (proton) Cut: 012 018060120 t + |t| min GeV 2 0 -2-3-4 012 018060120 0 -2-3-4 t + |t| min GeV 2 polar Angle at CM-system [deg] momentum of phi at Lab-flame[GeV] polar Angle at CM-system [deg] 0 40 80 120 160 0 40 80 20 60 100 0 200 300 0 40 80 120 0 200 400 600 0 50 100 150 200

25. invm(K+K-) invm(K-p) invm(K+K-) invm(K-p) K+ K- p Counts / 0.06 GeV/c 2 (CH 2 target data) required PID K + K - p φ(1020), Λ(1520) in K + K - p identified events φ→KKp Λ(1520)→KKp non-resonant KKp MC 1.3 1.4 1.5 1.6 1.7 1.8 1.9 0.9 1 1.1 1.2 1.3 1.3 1.5 1.7 1.9 1.4 1.6 1.8 Counts / 0.04 GeV/c 2 0 20 40 60 0 10 20

26. invm(K+K-) invm(K-p) invm(K+K-) invm(K-p) K- K+ p Counts / 0.04 GeV/c 2 Counts / 0.06 GeV/c 2 (CH 2 target data) required PID K + K - p φ(1020), Λ(1520) in K + K - p identified events φ→KKp Λ(1520)→KKp non-resonant KKp 0.9 1 1.1 1.2 1.3 1.3 1.4 1.5 1.6 1.7 1.8 1.9 1.3 1.5 1.7 1.9 1.4 1.6 1.8 0 10 20 0 10 20 30

27. Summary We have performed hyperon photoproduction experiment at SPring-8/LEPS with CH 2, C and Cu target using 1.5 –2.4 GeV photons. Time Projection Chamber surrounding the target extended the acceptance to backward region. LEPS standard detector system (forward spectrometer system) were used to detect forward going particles. In this talk, the status of the analysis of φ(1020) photoproduction has been reported. The determination of theφ-N cross section will be done in near future.