Abstract
For almost 50 years the structure of the 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- 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 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.
- Received 12 November 2014
DOI:https://doi.org/10.1103/PhysRevLett.114.132002
© 2015 American Physical Society
Synopsis
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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