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Lattice QCD Evidence that the Λ(1405) Resonance is an Antikaon-Nucleon Molecule

Jonathan M. M. Hall, Waseem Kamleh, Derek B. Leinweber, Benjamin J. Menadue, Benjamin J. Owen, Anthony W. Thomas, and Ross D. Young
Phys. Rev. Lett. 114, 132002 – Published 1 April 2015
Physics logo See Synopsis: Baryon’s Innards Have Molecular Structure

Abstract

For almost 50 years the structure of the Λ(1405) resonance has been a mystery. Even though it contains a heavy strange quark and has odd parity, its mass is lower than any other excited spin-1/2 baryon. Dalitz and co-workers speculated that it might be a molecular state of an antikaon bound to a nucleon. However, a standard quark-model structure is also admissible. Although the intervening years have seen considerable effort, there has been no convincing resolution. Here we present a new lattice QCD simulation showing that the strange magnetic form factor of the Λ(1405) vanishes, signaling the formation of an antikaon-nucleon molecule. Together with a Hamiltonian effective-field-theory model analysis of the lattice QCD energy levels, this strongly suggests that the structure is dominated by a bound antikaon-nucleon component. This result clarifies that not all states occurring in nature can be described within a simple quark model framework and points to the existence of exotic molecular meson-nucleon bound states.

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  • Received 12 November 2014

DOI:https://doi.org/10.1103/PhysRevLett.114.132002

© 2015 American Physical Society

Synopsis

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Baryon’s Innards Have Molecular Structure

Published 1 April 2015

The Lambda baryon, in its excited state, behaves like a molecule, according to new lattice chromodynamics simulations of the particle’s magnetic structure.

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Authors & Affiliations

Jonathan M. M. Hall1, Waseem Kamleh1, Derek B. Leinweber1,*, Benjamin J. Menadue1,2, Benjamin J. Owen1, Anthony W. Thomas1,3, and Ross D. Young1,3

  • 1Special Research Centre for the Subatomic Structure of Matter (CSSM), Department of Physics, University of Adelaide, Adelaide, South Australia 5005, Australia
  • 2National Computational Infrastructure (NCI), Australian National University, Canberra, Australian Capital Territory 0200, Australia
  • 3ARC Centre of Excellence for Particle Physics at the Terascale (CoEPP), Department of Physics, University of Adelaide, Adelaide, South Australia 5005, Australia

  • *Corresponding author. derek.leinweber@adelaide.edu.au

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Issue

Vol. 114, Iss. 13 — 3 April 2015

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