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Title: Comprehensive search for the {theta}{sup +} pentaquark on the lattice

Abstract

We study spin 1/2 isoscalar and isovector, even and odd parity candidates for the {theta}{sup +}(1540) pentaquark particle using large scale lattice QCD simulations. Previous lattice works led to inconclusive results because so far it has not been possible to unambiguously identify the known scattering spectrum and tell whether additionally a genuine pentaquark state also exists. Here we carry out this analysis using several possible wave functions (operators). Linear combinations of those have a good chance of spanning both the scattering and pentaquark states. Our operator basis is the largest in the literature, and it also includes spatially nontrivial ones with unit orbital angular momentum. The cross correlator we compute is 14x14 with 60 nonvanishing elements. We can clearly distinguish the lowest scattering state(s) in both parity channels up to above the expected location of the pentaquark, but we find no trace of the latter. Based on that we conclude that there are most probably ({approx_equal}2{sigma}/6{sigma} levels in the negative/positive parity channels) no pentaquark bound states at our quark masses, corresponding to m{sub {pi}}=400-630 MeV. However, we cannot rule out the existence of a pentaquark state at the physical quark mass corresponding to m{sub {pi}}=135 MeV or pentaquarks with amore » more exotic wave function.« less

Authors:
; ;  [1];  [1];  [2];  [3]
  1. Institute for Theoretical Physics, Eoetvoes University (Hungary)
  2. (Germany)
  3. Department of Theoretical Physics, University of Pecs (Hungary)
Publication Date:
OSTI Identifier:
20776678
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. D, Particles Fields; Journal Volume: 73; Journal Issue: 3; Other Information: DOI: 10.1103/PhysRevD.73.034506; (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; BOUND STATE; COMPUTERIZED SIMULATION; HYPERONS; ISOVECTORS; LATTICE FIELD THEORY; MEV RANGE; ORBITAL ANGULAR MOMENTUM; PARITY; PARTICLE IDENTIFICATION; QUANTUM CHROMODYNAMICS; QUARKS; REST MASS; SCATTERING; SPIN; WAVE FUNCTIONS

Citation Formats

Csikor, F., Katz, S.D., Toth, B.C., Fodor, Z., Department of Physics, University of Wuppertal, and Kovacs, T.G. Comprehensive search for the {theta}{sup +} pentaquark on the lattice. United States: N. p., 2006. Web. doi:10.1103/PhysRevD.73.034506.
Csikor, F., Katz, S.D., Toth, B.C., Fodor, Z., Department of Physics, University of Wuppertal, & Kovacs, T.G. Comprehensive search for the {theta}{sup +} pentaquark on the lattice. United States. doi:10.1103/PhysRevD.73.034506.
Csikor, F., Katz, S.D., Toth, B.C., Fodor, Z., Department of Physics, University of Wuppertal, and Kovacs, T.G. Wed . "Comprehensive search for the {theta}{sup +} pentaquark on the lattice". United States. doi:10.1103/PhysRevD.73.034506.
@article{osti_20776678,
title = {Comprehensive search for the {theta}{sup +} pentaquark on the lattice},
author = {Csikor, F. and Katz, S.D. and Toth, B.C. and Fodor, Z. and Department of Physics, University of Wuppertal and Kovacs, T.G.},
abstractNote = {We study spin 1/2 isoscalar and isovector, even and odd parity candidates for the {theta}{sup +}(1540) pentaquark particle using large scale lattice QCD simulations. Previous lattice works led to inconclusive results because so far it has not been possible to unambiguously identify the known scattering spectrum and tell whether additionally a genuine pentaquark state also exists. Here we carry out this analysis using several possible wave functions (operators). Linear combinations of those have a good chance of spanning both the scattering and pentaquark states. Our operator basis is the largest in the literature, and it also includes spatially nontrivial ones with unit orbital angular momentum. The cross correlator we compute is 14x14 with 60 nonvanishing elements. We can clearly distinguish the lowest scattering state(s) in both parity channels up to above the expected location of the pentaquark, but we find no trace of the latter. Based on that we conclude that there are most probably ({approx_equal}2{sigma}/6{sigma} levels in the negative/positive parity channels) no pentaquark bound states at our quark masses, corresponding to m{sub {pi}}=400-630 MeV. However, we cannot rule out the existence of a pentaquark state at the physical quark mass corresponding to m{sub {pi}}=135 MeV or pentaquarks with a more exotic wave function.},
doi = {10.1103/PhysRevD.73.034506},
journal = {Physical Review. D, Particles Fields},
number = 3,
volume = 73,
place = {United States},
year = {Wed Feb 01 00:00:00 EST 2006},
month = {Wed Feb 01 00:00:00 EST 2006}
}
  • 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 high-resolution ({sigma}{sub instr.} = 1.5 MeV) search for narrow states ({Lambda} < 10 MeV) with masses of M{sub x} {approx} 1500-1850 MeV in ep {yields} e{prime}K{sup +}X,e{prime}K{sup -}X, and e{prime}{pi}{sup +}X electroproduction at small angles and low Q{sup 2} was performed. These states would be candidate partner states of the reported {Theta}{sup +}(1540) pentaquark. No statistically significant signal was observed in any of the channels at 90% C.L. Upper limits on forward production were determined to be between 0.8% and 4.9% of the {Lambda}(1520) production cross section, depending on the channel and the assumed mass and width of themore » state.« less
  • 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 themore » total cross section for a narrow resonance at 1540 MeV was found to be 0.8 nb.« less
  • A search for the {theta}{sup +} in the reaction {gamma}d{yields}pK{sup -}K{sup +}n was completed using the CLAS detector at Jefferson Lab. A study of the same reaction, published earlier, reported the observation of a narrow {theta}{sup +} resonance. The present experiment, with more than 30 times the integrated luminosity of our earlier measurement, does not show any evidence for a narrow pentaquark resonance. The angle-integrated upper limit on {theta}{sup +} production in the mass range of 1.52-1.56 GeV/c{sup 2} for the {gamma}d{yields}pK{sup -}{theta}{sup +} reaction is 0.3 nb (95% C.L.). This upper limit depends on assumptions made for the massmore » and angular distribution of {theta}{sup +} production. Using {lambda}(1520) production as an empirical measure of rescattering in the deuteron, the cross section upper limit for the elementary {gamma}n{yields}K{sup -}{theta}{sup +} reaction is estimated to be a factor of 10 higher, i.e., {approx}3 nb (95% C.L.)« less
  • We search for the charmed pentaquark candidate reported by the H1 collaboration, the {theta}{sub c}(3100){sup 0}, in e{sup +}e{sup -} interactions at a center-of-mass (c.m.) energy of 10.58 GeV, using 124 fb{sup -1} of data recorded with the BABAR detector at the PEP-II e{sup +}e{sup -} facility at SLAC. We find no evidence for such a state in the same pD*{sup -} decay mode reported by H1, and we set limits on its production cross section times branching fraction into pD*{sup -} as a function of c.m. momentum. The corresponding limit on its total rate per e{sup +}e{sup -}{yields}qq event,more » times branching fraction, is about 3 orders of magnitude lower than rates measured for the charmed {lambda}{sub c} and {sigma}{sub c} baryons in such events.« less