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Title: Search for {theta}{sup +}(1540) Pentaquark in High-Statistics Measurement of {gamma}p{yields}K{sup 0}K{sup +}n at CLAS

Abstract

The exclusive reaction {gamma}p{yields}K{sup 0}K{sup +}n was studied in the photon energy range between 1.6 and 3.8 GeV searching for evidence of the exotic baryon {theta}{sup +}(1540){yields}nK{sup +}. The decay to nK{sup +} requires the assignment of strangeness S=+1 to any observed resonance. Data were collected with the CLAS detector at the Thomas Jefferson National Accelerator Facility corresponding to an integrated luminosity of 70 pb{sup -1}. No evidence for the {theta}{sup +} pentaquark was found. Upper limits were set on the production cross section as function of center-of-mass angle and nK{sup +} mass. The 95% C.L. upper limit on the total cross section for a narrow resonance at 1540 MeV was found to be 0.8 nb.

Authors:
; ; ; ; ;  [1]; ; ; ; ;  [2]; ; ; ; ; ; ; ; ;  [3]
  1. Istituto Nazionale di Fisica Nucleare, Sezione di Genova, and Dipartimento di Fisica, Universita di Genova, 16146 Genova (Italy)
  2. Rensselaer Polytechnic Institute, Troy, New York 12180-3590 (United States)
  3. Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606 (United States) (and others)
Publication Date:
OSTI Identifier:
20777005
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review Letters; Journal Volume: 96; Journal Issue: 4; Other Information: DOI: 10.1103/PhysRevLett.96.042001; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; CEBAF ACCELERATOR; CENTER-OF-MASS SYSTEM; GAMMA RADIATION; GEV RANGE 01-10; HYPERONS; KAONS NEUTRAL; KAONS PLUS; MASS; NEUTRONS; PARTICLE DECAY; PHOTON-PROTON INTERACTIONS; PROTONS; RESONANCE; STATISTICS; STRANGENESS; TOTAL CROSS SECTIONS

Citation Formats

Battaglieri, M., De Vita, R., Anghinolfi, M., Ricco, G., Ripani, M., Taiuti, M., Kubarovsky, V., Stoler, P., Cummings, J.P., Goett, J., Li Ji, Guo, L., Weygand, D.P., Avakian, H., Boiarinov, S., Brooks, W.K., Burkert, V.D., Degtyarenko, P.V., Deur, A., and Egiyan, H. Search for {theta}{sup +}(1540) Pentaquark in High-Statistics Measurement of {gamma}p{yields}K{sup 0}K{sup +}n at CLAS. United States: N. p., 2006. Web. doi:10.1103/PhysRevLett.96.042001.
Battaglieri, M., De Vita, R., Anghinolfi, M., Ricco, G., Ripani, M., Taiuti, M., Kubarovsky, V., Stoler, P., Cummings, J.P., Goett, J., Li Ji, Guo, L., Weygand, D.P., Avakian, H., Boiarinov, S., Brooks, W.K., Burkert, V.D., Degtyarenko, P.V., Deur, A., & Egiyan, H. Search for {theta}{sup +}(1540) Pentaquark in High-Statistics Measurement of {gamma}p{yields}K{sup 0}K{sup +}n at CLAS. United States. doi:10.1103/PhysRevLett.96.042001.
Battaglieri, M., De Vita, R., Anghinolfi, M., Ricco, G., Ripani, M., Taiuti, M., Kubarovsky, V., Stoler, P., Cummings, J.P., Goett, J., Li Ji, Guo, L., Weygand, D.P., Avakian, H., Boiarinov, S., Brooks, W.K., Burkert, V.D., Degtyarenko, P.V., Deur, A., and Egiyan, H. Fri . "Search for {theta}{sup +}(1540) Pentaquark in High-Statistics Measurement of {gamma}p{yields}K{sup 0}K{sup +}n at CLAS". United States. doi:10.1103/PhysRevLett.96.042001.
@article{osti_20777005,
title = {Search for {theta}{sup +}(1540) Pentaquark in High-Statistics Measurement of {gamma}p{yields}K{sup 0}K{sup +}n at CLAS},
author = {Battaglieri, M. and De Vita, R. and Anghinolfi, M. and Ricco, G. and Ripani, M. and Taiuti, M. and Kubarovsky, V. and Stoler, P. and Cummings, J.P. and Goett, J. and Li Ji and Guo, L. and Weygand, D.P. and Avakian, H. and Boiarinov, S. and Brooks, W.K. and Burkert, V.D. and Degtyarenko, P.V. and Deur, A. and Egiyan, H.},
abstractNote = {The exclusive reaction {gamma}p{yields}K{sup 0}K{sup +}n was studied in the photon energy range between 1.6 and 3.8 GeV searching for evidence of the exotic baryon {theta}{sup +}(1540){yields}nK{sup +}. The decay to nK{sup +} requires the assignment of strangeness S=+1 to any observed resonance. Data were collected with the CLAS detector at the Thomas Jefferson National Accelerator Facility corresponding to an integrated luminosity of 70 pb{sup -1}. No evidence for the {theta}{sup +} pentaquark was found. Upper limits were set on the production cross section as function of center-of-mass angle and nK{sup +} mass. The 95% C.L. upper limit on the total cross section for a narrow resonance at 1540 MeV was found to be 0.8 nb.},
doi = {10.1103/PhysRevLett.96.042001},
journal = {Physical Review Letters},
number = 4,
volume = 96,
place = {United States},
year = {Fri Feb 03 00:00:00 EST 2006},
month = {Fri Feb 03 00:00:00 EST 2006}
}
  • The exclusive reaction {gamma}p {yields} {bar K}{sup 0}K{sup +}n was studied in the photon energy range between 1.6-3.8 GeV searching for evidence of the exotic baryon {Theta}{sup +}(1540) {yields} nK{sup +}. The decay to nK{sup +} requires the assignment of strangeness S = +1 to any observed resonance. Data were collected with the CLAS detector at the Thomas Jefferson National Accelerator Facility corresponding to an integrated luminosity of 70 pb{sup -1}. No evidence for the {Theta}{sup +} pentaquark was found. Upper limits were set on the production cross section as function of center-of-mass angle and nK{sup +} mass. The 95%more » CL upper limit on the total cross section for a narrow resonance at 1540 MeV was found to be 0.8 nb.« less
  • The exclusive reactions {gamma}p{yields}K{sup 0}K{sup +}n and {gamma}p{yields}K{sup 0}K{sup 0}p have been studied in the photon energy range 1.6-3.8 GeV, searching for evidence of the exotic baryon {theta}{sup +}(1540) in the decays {theta}{sup +}{yields}nK{sup +} and {theta}{sup +}{yields}pK{sup 0}. Data were collected with the CLAS detector at the Thomas Jefferson National Accelerator Facility. The integrated luminosity was about 70 pb{sup -1}. The reactions have been isolated by detecting the K{sup +} and proton directly, the neutral kaon via its decay to K{sub S}{yields}{pi}{sup +}{pi}{sup -} and the neutron or neutral kaon via the missing mass technique. The mass and widthmore » of known hyperons such as {sigma}{sup +}, {sigma}{sup -} and {lambda}(1116) were used as a check of the mass determination accuracy and experimental resolution. Approximately 100 000 {lambda}*(1520)'s and 150 000 {phi}'s were observed in the K{sup 0}K{sup +}n and K{sup 0}K{sup 0}p final state, respectively. No evidence for the {theta}{sup +} pentaquark was found in the nK{sup +} or pK{sub S} invariant mass spectra. Upper limits were set on the production cross section of the reaction {gamma}p{yields}K{sup 0}{theta}{sup +} as functions of center-of-mass angle, nK{sup +} and pK{sub S} masses. Combining the results of the two reactions, the 95% C.L. upper limit on the total cross section for a resonance peaked at 1540 MeV was found to be 0.7 nb. Within most of the available theoretical models, this corresponds to an upper limit on the {theta}{sup +} width, {gamma}{sub {theta}{sup +}}, ranging between 0.01 and 7 MeV.« less
  • A search for photo-production of the {theta}{sup +}(1540) pentaquark and its decay to pK{sup 0} was performed with the CLAS detector system at Jefferson Lab. In the exclusive channel {gamma}d{yields}pK{sup 0}{sub s}K{sup -}(p), about twenty-thousand events with a slow missing proton, {pi}{sup +}{pi}{sup -} decay of the neutral kaon, and photon energy between 1.6 and 3.6 GeV are fully reconstructed. Included are numerous hyperon and meson resonances, with their decays to pK{sup -} and K{sup 0}K{sup -} respectively. To understand the possibility of a pentaquark signal amidst the backgrounds, a phenomenological isobar-inspired model of complex Breit-Wigner amplitudes and decay angularmore » distributions for the resonances is fit to the data with a maximum likelihood method. No pentaquark signal is found above the background. The upper limit on the total production cross section is measured to be consistent with other channels published by the collaboration, but systematic studies are still in progress.« less
  • A search for narrow {theta}{sup +}(1540), a candidate for a pentaquark baryon with positive strangeness, has been performed in an exclusive proton-induced reaction p + C(N) {yields} {theta}{sup +}K-bar{sup 0} + C(N) on carbon nuclei or quasifree nucleons at E{sub beam} = 70 GeV ({radical}(s) = 11.5 GeV) studying nK{sup +}, pK{sub S}{sup 0}, and pK{sub L}{sup 0} decay channels of {theta}{sup +}(1540) in four different final states of the {theta}{sup +}K-bar{sup 0} system. In order to assess the quality of the identification of the final states with neutron or K{sub L}{sup 0}, we reconstructed {lambda}(1520) {yields} nK{sub S}{sup 0}more » and {phi} {yields} K{sub L}{sup 0}K{sub S}{sup 0} decays in the calibration reactions p + C(N) {yields} {lambda}(1520)K{sup +} + C(N) and p + C(N) {yields} p{phi} + C(N). We found no evidence for a narrow pentaquark peak in any of the studied final states and decay channels. Assuming that the production characteristics of the {theta}{sup +}K-bar{sup 0} system are not drastically different from those of the {lambda}(1520)K{sup +} and p{phi} systems, we established upper limits on the cross-section ratios {sigma}({theta}{sup +}K-bar{sup 0})/{sigma}({lambda}(1520)K{sup +}) < 0.02 and {sigma}({theta}{sup +}K-bar{sup 0})/{sigma}(p{phi}) < 0.15 at 90% C.L. and a preliminary upper limit for the forward-hemisphere cross section {sigma}({theta}{sup +}K-bar{sup 0}) < 30 nb/nucleon.« less
  • Within the spectator model, we study the reaction {gamma}d {sup {yields}} K{sup -}{theta}{sup +}p {sup {yields}} K{sup -}K{sup +}np in the threshold energy region. We present the predictions for the exclusive and inclusive K{sup -}-meson angular distributions in the laboratory system for this reaction calculated for two possible parity states of the {theta}{sup +} resonance at 1.5-and 1.75-GeV beam energies with and without imposing the relevant kinematical cuts on those parts of the sampled phase space where the contribution from the main background sources, associated with the {phi}(1020), {lambda}(1520) production as well as with the K{sup -}p rescattering in themore » final state, is expected to be dominant. We show that, under the chosen kinematics, these distributions are sensitive to the {theta}{sup +} parity and, therefore, can be used as a filter for the determination of its parity.« less