Future Hadronic Spectroscopy at JLAB and J-PARC

1
Future Hadronic Spectroscopyat JLAB and J-PARC

• Introduction
• ? and ? Resonances
• Quark-Model Predictions
• ? Resonances
• Experimental Considerations
• Summary

Hawaii 2005 Second Joint Meeting of the Nuclear
Physics Divisions of the APS and JPS September
18, 2005
2
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.

3
Introduction (continued)

• In comparison with N and ? resonances, very
  little is known about hyperon states.
• Due to relative paucity of K?p and K?n data, our
  knowledge of properties of ? and ? comes almost
  entirely from energy-dependent PWAs.
• In comparison with strangeness 0 and -1, very
  little is known about ? and O states.

4
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?

5
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 33310881. Thus, the states should be in
  the ratio
• N????O213331.
• 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 ? ? ? ? O
Expected 7 21 21 21 7
Observed 10 14 10 6 2
From V.V. Abaev et al., Hadron Spectroscopy at
J-PARC LOI.
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Status of ? and ? Resonances
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Methods for Identifying ? and ? Events

• Strangeness -1 hyperons may be identified by
  formation in KN experiments or by production in
  ?N experiments.
• Examples of formation reactions are KN ? KN, ??,
  ??, ??, ??, K?, KN, ??(1520), and ??(1385),
  where the last two reactions are typically
  identified from the 3-body final states KN ? ???
  and KN ? ???.

8
Typical Data at 1165 and 1177 MeV/c
9
Typical Data for KN??? at 1245 and 1233 MeV/c
10
Crystal Ball Results for K?p??0? at 750 MeV/c
11
Partial-Wave Analyses of KN Scattering

• Advantage of formation reactions to study ? 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.

12
Example of an Argand Diagram Showing the ?(1520)
and ?(1690) Resonances
13
Quark-Model Predictions
14
On Missing ? and ? States

• Presence of heavier strange quark leads to
  segregation of states into ? oscillations, in
  which the two nonstrange quarks oscillate, and ?
  oscillations, in which the strange quark
  oscillates against the nonstrange pair.
• The nonstrange ? 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.

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? Resonances

• Not much is known about ? resonances. This is
  because
• 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,
• The production cross sections are small
  (typically a few µb), and
• 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).

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Status of ? Resonances
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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.

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Typical Criteria for Selecting ?? (or O? )
Events in K?p??? anything

• Require invariant mass of ?? and p to be
  consistent with ? mass.
• Require invariant mass of ?? (or K? ) and ? to be
  consistent with ?? (or O?).
• Require reconstructed ? and ?? (or O? ) tracks to
  be at least 2 cm.

D. Aston et al., PRD 32, 2270 (1985).
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Distributions of ??? Invariant Mass
D. Aston et al., PRD 32, 2270 (1985).
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? 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 ? p ? K K X, which can be
  studied at JLab

C.M. Jenkins et al., PRL 51, 951(1983)
21
States Seen in K? p ? K ??
C.M. Jenkins et al., PRL 51, 951(1983)
22
Experimental ConsiderationsHyperon 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.

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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).

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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 ? 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.

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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 ? 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.

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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 ? 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.