SPring-8/LEPS Experiment  Observation of 5-quark Resonance

1. SPring-8/LEPS Experiment Observation of 5-quark Resonance Wen-Chen Chang 章文箴 中央研究院 物理研究所

2. Outline • Hadrons in the quark models. • Exotic multi-quark states. • LEPS experiment at SPring-8, Japan. • + resonance. • Theoretical interpretations. • Outlook.

3. Instruments vs Observables

4. Mendeleev and Periodic Table

5. The Core Part: Nucleus

6. What is the World Made of?

8. Four Interactions

10. Evolvement of Interactions

11. Particles discovered 1898 - 1964: 1953 Donald Glaser invented the bubble chamber. The Brookhaven Cosmotron, a 1.3 GeV accelerator, started operation.

12. Back to Year 1964 • A hundred or so types of particles were identified: • Baryons (fermion): n, p, , , ,…. • Mesons (boson) : , , ….. • Murray Gell-Mann (Mendeleev of elementary particle physics) proposed “the eightfold way” to put these particles in order, suggesting more elementary constituents: quarks. • Three types of quarks, u, d and s. • Baryons composed of 3 quarks. • Mesons composed of 2 quarks: a quark and an antiquark.

13. Quark Model

14. Baryon Octet (s=1/2)

15. Meson Octet (s=0)

16. Baryon Decuplet (s=3/2) (1232) (1384) (1533) (1672)

17. The Color Space • The overall wave function is product of space*flavor*spin. Pauli principle requires an anti-symmetric wave function for a fermion system. • The quark configuration of ++(1232) is (uuu) and s=3/2. The wave function is symmetric in flavor, spin and space. • Introduce another degree of freedom (strong interaction charge), COLOR, to quarks and each quark in ++ has different color (uuu), but the system overall has to be colorless or . • Fundamental theory of describing “the Strong Interaction”: Quantum Chromo Dynamics (QCD). white

18. Quarks Confined Inside Colorless Hadrons Enduring mystery: Of the many allowed possibilities for combining quarks with color into colorless hadrons, only two types of configurations are well known: “pion, kaon, phi, eta” “Proton, Neutron, Lambda, Omega” q = any one of {u, d, s, c, b, t}

19. K Mesons qq p K N S X W─ Baryons built from meson-baryon, or qqqqq Q+ Hadron multiplets D++ Baryons qqq X--

20. Beyond Conventional Quark Model Spectroscopy • Di-baryons H(qqqqqq): R. Jaffe (1977). • Multi-quark mesons (qqqq): R. Jaffe (1977). • Multi-quark baryons, pentaquark (qqqqq) : H. Hogaasen (1979), D. Strottman (1979), H. Lipkin (1987), M. Praszalowicz (1987), D.I. Diakonov et al. (1997). • Hybrid states (qqg, qqqg). • Glueballs (gg, ggg). • “The discovery of a manifestly exotic baryon provides an opportunity to refine our understanding of quark dynamics at low energy, where it is not perturbative.” --- R. Jaffe and F. Wilczek. ¯ ¯ ¯ ¯

21. T. Nakano et al., Phys. Rev. Lett. 91, 012002 (2003)

23. Worldwide Observation of +(1540)

24. RCNP, Osaka University, Japan H. Fujimura, M. Fujiwara, T. Hotta, H. Kohri, T. Matsumura, N. Matsuoka, T. Mibe, M. Morita, T.Nakano, T. Yorita Osaka University, Japan N. Nomachi, A. Sakaguchi, Y. Sugaya, M. Sumihama Academia Sinica, Taiwan W.C. Chang, T.H. Chang, D.S. Oshuev, C.W. Wang, S.C. Wang Chiba University, Japan H. Kawai, T. Ooba, Y. Shiino IHEP, Russia P. Shagin JAERI, Japan Y. Asano, N. Muramatsu, R.G.T. Zegers JASRI, Japan S. Date, N. Kumagai, Y. Ohashi, H. Ookuma Konan University, Japan H. Akimune Kyoto University, Japan K. Imai, T. Ishikawa, M.Miyabe, M.Niiyamma ,M. Yosoi Nagoya University, Japan S. Fukui, T. Iwata, Y. Miyachi, A. Wakai Ohio University, U.S. K. Hicks Pusan National University, S. Korea J.K. Ahn Saskatchewan University, Canada C. Rangacharyulu Tohoku University, Japan H. Shimizu Wakayam Med. University, Japan S. Makino LEPS Collaboration

25. Super Photon Ring 8 GeV (SPring-8) Harima Science Garden City

26. GeV-photon Experiments

27. SPring-8 Beam-Lines

28. Synchrotron Radiation

29. GeV Photon from Backward Compton Scattering

30. Laser System Ar ion laser (MLUV,CW 5.5W) Polarization rotator Focusing lens

31. Straight section e- (8GeV) Laser Bending magnet g Tagging counter e’ e Collision in Storage Ring

32. Linearly Polarized Photon • Backward Compton scattering with UV laser light • Intensity (typ.) : 2.5 * 106 cps • Tagging region : 1.5 GeV< Eg < 2.4 GeV • Linear polarization : 95 % at 2.4 GeV Counts Linear polarization Eg(GeV) Eg(Tagger) (GeV)

33. Experimental Hutch

34. g LEPS Detector System Dipole Magnet (0.7 T) TOF wall Start counter Aerogel Cherenkov (n=1.03) MWDC 3 Silicon Vertex Detector MWDC 2 MWDC 1 1m

35. Target,Upstream Spectrometer, Dipole Magnet LH2 Target (50 mm long) Drift Chamber g SSD Start Counter Cherenkov Detector

36. Dipole Magnet and Drift Chambers

37. Time-of-Flight Wall

38. DAQ computer and circuit FERA -UIO FastBus -NGF FADC FADC Alpha server 1200 Solaris boot server FAST ether Data Ether net VME board computer Force 7V

39. Physics event Detector Electronics DAQ RAW DATA Calibration Parameters LEPSana Ntuple Analysis Code Physics Results Offline Analysis

40. K/p separation (positive charge) Reconstructed mass p- p+ p+ p K+ K+ Events d Momentum (GeV) K- Mass(GeV) Mass/Charge (GeV) Particle Identification (50mm-long LH2) 2000,Dec. – 2001, June (150mm-long LH2) 2002,May – 2002, July (150mm-long LD2) 2002, Oct – present

41. How Do We Identifiy Resonances? J/ Resonance: Broad states with finite widths and lifetimes, which can be formed by collision between the particles into which they decay.

42. Identification of + • Two proposed production modes in photon-nucleon collisions: • Because of forward spectrometer setup, we look into neutron production mode with detection of charged K+K- and requiring missing mass to be that of nucleon. • Correction of Fermi Momentum of neutrons inside nuclei. • Backgrounds:

43. Summary of Event Selections • Target cut: z-Vertex position (Start Counter target). • Final state cut: • K+K pair detected. • Missing nucleon mass (0.90<MM<0.98 GeV/c2) after Fermi motion correction. • Remove background: • Exclusion of  events (MKK>1.04 or <1.00 GeV/c2). • Proton-tagging veto: • Fiducial cut to require scattered nucleons be within SSD acceptance. • Nucleon momentum cut. (PN>0.35 GeV/c) • Veto cut with proton tagging in SSD and two charged-track only. • 8869 events →109+signal events.

44. Summary of Event Selections • K+K pair. • z-Vertex position (Start Counter target). • Photon energy (E<2.35 GeV). • Missing nucleon mass (0.90<MM<0.98 GeV/c2). • Exclusion of  events (MKK>1.04 or <1.00 GeV/c2). • Fiducial cut to require scattered nucleons be within SSD acceptance. • Nucleon momentum cut. (PN>0.35 GeV/c) • Veto cut with proton tagging in SSD and two charged-track only. • 8869 events →109 +signal events.

45. Event Selection : Target and Exclusion of  events

46. Correction of Fermi Motion of Nucleons inside Nuclei For Nucleon Missing Mass Cut After correction Before correction

47. Removing (1520) Events: Proton Tagging in SSD SC events with a proton hit in the SSD. + signal events (without proton hit in the SSD).

48. Undetected X Calculation of Missing Mass from Energy-Momentum conservation

49. Missing Mass Spectra of K+ from LH2 target • From LH2 target • Assuming proton to be at rest

50. Final + Peak in MM Background: normalized LH2 events with similar event selections. + signal events (19.02.8 events, 4.6 significance).