skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: The Strangeness Physics Program at CLAS

Abstract

An extensive program of strange particle production off the nucleon is currently underway with the CEBAF Large Acceptance Spectrometer (CLAS) in Hall B at Jefferson Laboratory. This talk will emphasize strangeness electroproduction in the baryon resonance region between W=1.6 and 2.4 GeV, where indications of s-channel structure are suggestive of high-mass baryon resonances coupling to kaons and hyperons in the final state. Precision measurements of cross sections and polarization observables are being carried out with highly polarized electron and real photon beams at energies up to 6 GeV. The near-term and longer-term future of this program will also be discussed.

Authors:
Publication Date:
Research Org.:
Thomas Jefferson National Accelerator Facility, Newport News, VA
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
924021
Report Number(s):
JLAB-PHY-08-774; DOE/OR/23177-0321; arXiv:0801.0818
TRN: US0802004
DOE Contract Number:
AC05-06OR23177
Resource Type:
Conference
Resource Relation:
Conference: 2007 Winter Conference on Particle Physics: New Physics at the Electroweak Scale and New Signals at Hadron Colliders, Aspen, Colorado, 8-13 Jan 2007
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; ACCURACY; BARYONS; CEBAF ACCELERATOR; CROSS SECTIONS; ELECTRONS; ELECTROPRODUCTION; HADRONS; HYPERONS; KAONS; NUCLEONS; PHOTON BEAMS; PHYSICS; POLARIZATION; S CHANNEL; SPECTROMETERS; STRANGE PARTICLES; STRANGENESS

Citation Formats

Daniel S. Carman. The Strangeness Physics Program at CLAS. United States: N. p., 2007. Web.
Daniel S. Carman. The Strangeness Physics Program at CLAS. United States.
Daniel S. Carman. Mon . "The Strangeness Physics Program at CLAS". United States. doi:. https://www.osti.gov/servlets/purl/924021.
@article{osti_924021,
title = {The Strangeness Physics Program at CLAS},
author = {Daniel S. Carman},
abstractNote = {An extensive program of strange particle production off the nucleon is currently underway with the CEBAF Large Acceptance Spectrometer (CLAS) in Hall B at Jefferson Laboratory. This talk will emphasize strangeness electroproduction in the baryon resonance region between W=1.6 and 2.4 GeV, where indications of s-channel structure are suggestive of high-mass baryon resonances coupling to kaons and hyperons in the final state. Precision measurements of cross sections and polarization observables are being carried out with highly polarized electron and real photon beams at energies up to 6 GeV. The near-term and longer-term future of this program will also be discussed.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jan 08 00:00:00 EST 2007},
month = {Mon Jan 08 00:00:00 EST 2007}
}

Conference:
Other availability
Please see Document Availability for additional information on obtaining the full-text document. Library patrons may search WorldCat to identify libraries that hold this conference proceeding.

Save / Share:
  • An extensive program of strange particle production off the proton is currently underway with the CEBAF Large Acceptance Spectrometer (CLAS) in Hall B at Jefferson Laboratory. This talk will emphasize strangeness photo- and electroproduction in the baryon resonance region between W =1.6 and 2.5 GeV, where indications of s-channel structure are suggestive of high-mass baryon resonances coupling to kaons and hyperons in the final state. Precision measurements of cross sections and polarization observables are being carried out with both electron and real photon beams, both of which are available with high polarization at energies up to 6 GeV.
  • A brief overview of strangeness physics with the CLAS detector at JLab is given, mainly covering the domain of nucleon resonances. Several excited states predicted by the symmetric constituent quark model may have signiffcant couplings to the K+ or K0 channels. I will discuss data that are relevant in the search for such states in the strangeness channel, and give an outlook on the future prospects of the N* program at JLab with electromagnetic probes.
  • We review recent developments in strangeness photo- and electro- production off the proton and neutron, as investigated using CLAS in Hall B at Jefferson Lab. By measuring sufficient spin observables one can decompose the reaction mechanism into elementary amplitudes. We discuss progress toward this end in recent data from CLAS, including cross sections and spin observables. We next discuss new results on the mass distribution of the Lambda(1405), which shows signs of being a composite meson-baryon object of mixed isospin. The work on other hyperons such as the Xi resonances will be mentioned, and future prospects for the CLAS programmore » outlined.« less
  • A very brief overview is presented of varied strangeness-physics studies that have been conducted with the CLAS system in the era of 6 GeV beam at Jefferson Lab. A full bibliography of articles related to open strangeness production is given, together with some physics context for each work. One natural place where these studies could be continued, using a K L beam and the GlueX detector, is in the further investigation of the Λ(1405) baryon. The line shapes and cross sections of this state were found, using photoproduction at CLAS, to differ markedly in the three possible Σπ final states.more » The analogous strong-interaction reactions using a K L beam could further bring this phenomenon into focus. 1. The CLAS program ran from 1998 to 2012, during the time when the maximum Jefferson Lab beam energy was 6 GeV. An important thrust of this program was to investigate the spectrum of N * and Δ * (non-strange) baryon resonances using photo-and electro-production reactions. To this end, final states containing strange particles (K mesons and low-mass hyperons) played a significant role. The reason for this is partly due to favorable kinemat-ics. When the total invariant energy W (= √ s) of a baryonic system exceeds 1.6 GeV it becomes possible to create the lightest strangeness-containing final state, K + Λ. This is a two-body final state that is straightforward to reconstruct in the CLAS detector system [1], and theoretically it is easier to deal with two-body reaction amplitudes than with three-and higher-body reaction amplitudes. In the mass range W > 1.6 GeV the decay modes of excited nucleons tend to not to favor two-body π-nucleon final states but rather multi-pion states. As input to partial-wave decompositions and resonance-extraction models, therefore, the strangeness-containing final states of high-mass nucleon excitations have had importance. Excited baryons decay through all possible channels simultaneously, constrained by unitarity of course, and channel-coupling is crucial to determining the spectrum of excita-tions. Within this mix of amplitudes, however, the KY decay modes have proven useful. The end result has been, as summarized in the recent edition of the Review of Particle Properties [2], clearer definition of the spectrum of baryonic excitations, with definite contributions from the strangeness sector channels. To this end, strangeness photoproduction cross sections measurements at CLAS for the K + Λ, K + Σ 0 and K 0 Σ + channels on a proton target were published [3–6]. Cross sections are not enough, in general, to define the reaction mechanism, including the underlying N * excitation spectrum. Photoproduction of pseudo-scalar mesons is described by four complex amplitudes, leading to fifteen spin observables in addition to the cross section. Full knowledge of these spin observables would exhaust the information that can be gleaned experimentally about any given reaction channel. Here the hyperonic channels offer another advantage when compared with the non-strange reaction channels: the polarization of most hyperons can be measured directly through their parity-violating weak decay asymmetries. Unlike 163« less
  • The CLAS collaboration has developed a broad program for studying electromagnetically induced processes with both electron and photon beams. This program includes topics such as excited baryon resonances, meson production, hadron structure, search for pentaquarks, and the structure of nuclei. In this report, highlights of recent CLAS results will be presented.