Future Hadronic Spectroscopy at JLAB and J-PARC IntroductionIntroduction  and Λ Resonances  and Λ Resonances Quark-Model PredictionsQuark-Model Predictions  Resonances  Resonances Experimental ConsiderationsExperimental Considerations SummarySummary Hawaii 2005 Second Joint Meeting of the Nuclear Physics Divisions of the APS and JPS September 18, 2005

Introduction Historically, hadron spectroscopy experiments led to several important discoveries, including: Development of concept of SU(3) symmetry; Discovery of strange quark; Discovery of charm quark; Evidence for glueballs and multiquark states. This talk will focus on hyperon spectroscopy, at the request of the organizers.

Introduction (continued) In comparison with N* and Δ* resonances, very little is known about hyperon states. Due to relative paucity of K‾p and K‾n data, our knowledge of properties of Λ* and  * comes almost entirely from energy- dependent PWAs. In comparison with strangeness 0 and -1, very little is known about  * and Ω* states.

Open Questions Where are the “missing” hyperon states? Are there hybrid hadrons (i.e., states involving gluonics degrees of freedom)? Are there “exotic” hadrons, and if so, what are their spectra? Are there new symmetries to be discovered by improving our knowledge of hadron spectra?

Expected and Observed Baryon States Assuming baryons to be formed of three quarks (u,d,s), then SU(3) provides the decomposition into multiplets to which these states will belong as 3×3×3= Thus, the states should be in the ratio N*:Δ*:Λ*:  *:  *:Ω*=2:1:3:3:3:1. There are 14 N* listed in the PDG tables as 3* and 4* resonances, so the expected number and observed number of 3* and 4* resonances is: Resonance Δ* Λ*  *  * Ω* Expected # Observed # From V.V. Abaev et al., “Hadron Spectroscopy at J-PARC” LOI.

Status of Λ and  Resonances

Methods for Identifying  * and Λ* Events Strangeness -1 hyperons may be identified by formation in KN experiments or by production in γN experiments. Examples of formation reactions are KN → KN,  Λ, , ηΛ, η , KΔ, K*N,  Λ(1520), and  (1385), where the last two reactions are typically identified from the 3-body final states KN →  and KN →  Λ.

Typical Data at 1165 and 1177 MeV/c

Typical Data for KN→  at 1245 and 1233 MeV/c

Crystal Ball Results for K‾p→  0 Λ at 750 MeV/c

Partial-Wave Analyses of KN Scattering Advantage of formation reactions to study Λ* and  * production is that such reactions lend themselves to partial-wave analyses. Prior PWAs were limited not only by the available data, but also by computers slow by modern standards. Essentially all resonance information is based on simplistic energy-dependent parametrizations that violate unitarity of the S-matrix. There is a strong need for high-statistics data (including spin observables) for a variety of formation reactions with broad energy coverage.

Example of an Argand Diagram Showing the Λ(1520) and Λ(1690) Resonances

Quark-Model Predictions

On Missing Λ* and  * States Presence of heavier strange quark leads to segregation of states into ρ oscillations, in which the two nonstrange quarks oscillate, and Λ oscillations, in which the strange quark oscillates against the nonstrange pair. The nonstrange ρ oscillations trivially decouple from KN and related channels in the single-quark transition model. Better data are needed in order to make comparisons with predictions.

 Resonances Not much is known about  resonances. This is because* (1)They can only be produced as a part of a final state, and so the analysis is more complicated than if direct formation is possible, (2)The production cross sections are small (typically a few μb), and (3)The final states are topologically complicated and difficult to study with electronic techniques. * Note taken from Review of Particle Physics, PLB 592, p. 967 (2004).

Status of  Resonances

Methods for Identifying  * Resonances  * events must be identified in production experiments by either (1) constructing invariant-mass distributions from the  * decay products, or by (2) making missing-mass distributions. Examples will be presented of both methods.

Typical Criteria for Selecting  ‾ (or Ω ‾ ) Events in K ‾ p→  ‾ + anything Require invariant mass of  ‾ and p to be consistent with Λ mass. Require invariant mass of  ‾ (or K‾ ) and Λ to be consistent with  ‾ (or Ω‾). Require reconstructed Λ and  ‾ (or Ω‾ ) tracks to be at least 2 cm. D. Aston et al., PRD 32, 2270 (1985).

Distributions of Λ  ‾ Invariant Mass D. Aston et al., PRD 32, 2270 (1985).

 * Detection by Missing-Mass Distributions Study of K‾ p → K + X, where X contains  * Completely avoids problem of detecting decay products Analogous to study of γ p → K + K + X, which can be studied at JLab C.M. Jenkins et al., PRL 51, 951(1983)

States Seen in K‾ p → K +  *‾ C.M. Jenkins et al., PRL 51, 951(1983)

Experimental Considerations: Hyperon Spectroscopy Physics at J-PARC In Summer 2002, J-PARC Project Director called for LOIs for the nuclear and particle physics experiments at J-PARC. A total of 30 LOIs were received. Of these, at least three relate directly to hadron spectroscopy (baryons and mesons), and two of those involve spectroscopy requiring high- momentum kaon beams.

LOIs for Hadron Spectroscopy with Kaon Beams L13 – Hadron spectroscopy at J-PARC Contact persons: Shin-ya Sawada (KEK, Japan) and Hal Spinka (ANL, USA). L28 – Letter of intent for a hadron spectroscopy experiment with RF- separated high energy K ± beam at JHF Contact persons: V. Obraztsov (IHEP, Russia) and T. Tsuru (KEK, Japan).

Kaon beams for Hyperon Spectroscopy at J-PARC Proposed K1.8 beam (high-intensity K‾ beam at ~1.8 GeV/c available at the 50-GeV PS) opens the possibility for a rich program in Λ* and  * spectroscopy for states up to ~2 GeV in mass. To carry out a program in  * spectroscopy will require separated K‾ beams up to about 6 GeV/c. As already noted, present data are statistically limited, and polarization data are especially needed.

Hyperon Spectroscopy at JLAB Program to explore  * spectroscopy has already begun at JLAB using missing-mass methods (J. Price et al.). Great opportunity exists to open a new frontier in Λ* and  * spectroscopy by photoproduction and electroproduction. Production by real or virtual photons offers possibility to discover states that decouple from KN and therefore, which are not likely to be seen, in formation experiments with kaon beams.

Summary Hyperon spectroscopy is a fundamental area of physics about which we still know very little. Presence of one or two “heavy” quarks represents a departure from the permutation symmetry characterizing N* and Δ* spectroscopy. Quark-model predictions for mass spectrum and decay mechanisms have not been stringently tested due to almost no experimental progress in past two decades. High-intensity beam lines with modern 4  detectors offer opportunity to open a new frontier on the study of S=-1 and S=-2 baryons.