1 / 26

The light meson spectroscopy program

The light meson spectroscopy program . Landscape Experiments BES III (J/ y decays) COMPASS ( p − beam) CLAS ( g beam) Outlook. Elton S. Smith, Jefferson Lab 13 th International Conference on Meson-Nucleon Physics and the Structure of the Nucleon. Light Mesons. q. q. q. q. q.

august
Download Presentation

The light meson spectroscopy program

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. The light meson spectroscopy program • Landscape • Experiments • BES III (J/y decays) • COMPASS (p− beam) • CLAS (g beam) • Outlook Elton S. Smith, Jefferson Lab 13th International Conference on Meson-Nucleon Physics and the Structure of the Nucleon

  2. Light Mesons q q q q q q q q • Quark model mesons (u, d, s quarks) • Glueballs (gluons and no quarks) • Multiquarks (quark-antiquark pairs) • Hybrids (quarks and gluons, which contribute to static properties) Call these the “ABC” states KlemptZaitsev Phys Rep 454 (2007) 1

  3. Normal Mesons – qq color singlet bound states K* w r f K* K0 JPC = 0– +0++1– – 1+ –2++ … Allowed combinations JPC = 0– –0+ –1– +2+ – … Not-allowed: exotic Spin/angular momentum configurations & radial excitations generate the known spectrum of light quark mesons. Starting with u - d - s we expect to find mesons grouped in nonets - each characterized by a given J, P and C. Spin 0 Spin 1 S2 S = S1 + S2 J = L + S P = - (-1)L C = (-1)L+S K0 K+ S1 L h’ p0 p+ p− h K−

  4. Nonets of Scalar (0++) Mesons q q q q I3 Jaffe Phys Rev D15 (1977) 267 Crede Meyer Prog Part NuclPhy 63 (2009) 74

  5. BESIII: e+e- in the charmonium region Operating since 2008, √s = 2 − 4.2 GeV Wei Moriond QCD and High Energy Interactions 2013

  6. BES III: pp mass threshold enhancement M ~ 1.83-1.86 GeV Confirmation of enhancement first observed by BES II • Possible interpretations • Conventional meson • ppbar bound state / multi-quark • glueball Chinese Phys C 34 (2010) 421

  7. BES III: pp mass threshold PWA • Breit-Wigner and S-wave FSI describes structure • M = 1832 ± 19 MeV • G = 13 ± 39 MeV • Spin-parity of 0-+ strongly favored by PWA fit Ablikim PRL 108 (2012) 112003 Chinese Phys C 34 (2010) 421

  8. BES III: X(1835) structures in J/y->gh’p+p- • X(1835) • M = 1837 ± 3 MeV • G = 190 ± 9 MeV • X(2120) • M = 2122 ± 7 MeV • G = 83 ± 16 MeV • X(2370) • M = 2376 ± 9 MeV • G = 83 ± 17 MeV • Angular distribution of X(1835) consistent with 0-+ assignment • Pure glue lattice expects lowest 0-+ glueball mass ~ 2.5 GeV Ablikim PRL 106 (2011) 072002

  9. BES III: X(1870) in J/y->wX, X->hp+p- w X(1870) h(1405) f1(1285) • X(1870) • M = 1877 ± 6 MeV • G = 57 ± 12 MeV • X-> a0(980)p, a0->hp • Identification of X(1870)? • Spin-parity 0-+? • Is it the X(1835)? h2(1870)? • Need PWA! Ablikim PRL 107 (2011) 182001

  10. BES III: Summary and prospects • Huge data samples collected for charmonium decays at BES III • Data based on 200 M J/y events • Confirms of the ppbar mass threshold enhancement at 1832 MeV • Confirms of the X(1835)->h’p+p- and finds two new structures: X(2120) and X(2370) • Observes the new structure X(1870) in J/y -> wX(hp+p-) • 1.2 billion J/y and 500 million y events already collected • Expect rich physics results in the coming years from BES III

  11. Spectrum of 1−+ exotic signals q q q q Expectation from LQCD Unlikely Hybrid Dynamical origin? I3 Meyer Van Haarlem Phys Rev C82 (2010) 025208

  12. COMPASS: spectroscopy with pion beams Hadron Setup 2008/09 190 GeV 2004 Pilot Run (4 days 190 GeV, Pbtgt, p-) 2008/09 (high statistics, 190 GeV, LH2 tgt, p±, K±, p±) Courtesy of F. Nerling

  13. COMPASS: Exotic 1-+p1(1600)->p+p-p- ~0.4 M events Intensity =1.7% of total

  14. Amplitude analysis 3psystem in isobar model p (bachelor) 1 L pa Rpp spin S 2 pb The decay of the 3p system at point 1 to the di-pion resonance Rppand a bachelor pion is described in the Gottfried-Jackson frame. The decay of Rpp→ papb at point 2 is described in the helicity frame. Hybrid JPCMe g(beam) e = + natural e = − unnatural parity exchange n(recoil) p (target) Partial waves (in the reflectivity basis): JPCMe[isobar] L

  15. Toy example: resonant phases 2 waves Phase motion Black –Blue

  16. COMPASS: Diffractive dissociation into 3p 38% of 2008 data PWA ~ 1M events PWA ~ 24M events

  17. COMPASS: reproducing known resonances a1(1260)->(pp)sp Intensity Acceptance corrected 53 waves included Phase motion

  18. COMPASS: reference and exotic signals 1-+ Exotic Mass (GeV) Intensity Acceptance corrected 53 waves included Phase motion

  19. COMPASS: Primakoff production of p+p-p- 1-+ Exotic t’ < 0.001 GeV2 • No intensity exotic 1-+ wave near 1.6 GeV • Pilot run for Primakoff reaction, t’ < 0.001 GeV2 • Photoproduction in the Coulomb field of heavy nucleus Grube CLAS12 Workshop, Glasgow

  20. COMPASS: Summary and prospects • Diffractive production of 3p states • Analysis of 50x statistics of initial pilot run • Results for p1(1600)-> p-p-p+ and p1(1600)->p-p0p0 • Confirmation of exotic state • Ongoing analysis • Pilot Primakoff data sees no exotic in quasi-photoproduction • Exotic signals also seen in hp and h’p channels • Search for p1(2000) in the KKpp final state • COMPASS has acquired large statistics on many reactions • Diffractive dissociation of p, p-, K- on various targets • Central production of (pp) in pp reactions, which can be used for glueball searches. • p-g and K-gPrimakoff reactions on heavy targets

  21. CLAS: Photoproduction at 6 GeV Nozar PRL 102 (2009) 102002 • G12 Data Run Conditions • Ie = 60-65 nA • Eg = 3.584 – 5.453 GeV • 26.2 billion triggers • Integrated luminosity of 68 pb-1

  22. CLAS: PWA extraction of known resonances

  23. CLAS: Small non-resonant 1-+ exotic wave M=1+ and 1- Degenerate waves for unpolarizedg M=0 Expect Zero For pion exchange

  24. CLAS: PWA 1−+ − 2−+ Phase Motion

  25. CLAS: Summary and prospects • No evidence for 1−+exotic resonance in photoproduction • Confirmation of earlier limits with higher sensitivity • Intensity of exotic wave < 2% of total • Phase of exotic wave consistent with non-resonant signal • Other analyses • Study of exotic signal in gp->hp−D++ • Searches for strangeonium in gp->pfh [Spec1: D. Schott] [Future Facilities: R. Mckeown] [P. Eugenio] [L. Elouadrhiri] • GlueX in Hall D at 12 GeV • Commissioning Fall 2014 • Forward Tagger for CLAS12

  26. Summary • The spectrum of “ABC” mesons is being investigated in both collider and fixed target experiments • BES III has identified structures with masses ~ 1.8−2.4 GeV • Their internal structure is under study and may shed light on the nature of gluonic interactions. • The 1−+ exotic p1(1600)->3p is confirmed by COMPASS in p−interactions • Upper limits are set on the1−+ exotic wave in CLAS photoproduction, which are consistent with non-resonant background

More Related