31 July 2023 to 4 August 2023
America/Chicago timezone

The two-pole nature of the $\Lambda(1405)$ from lattice QCD

31 Jul 2023, 17:00
20m
Curia II (WH2SW)

Curia II

WH2SW

Speaker

Fernando Romero-Lopez (MIT)

Description

The $\Lambda(1405)$ resonance is listed in PDG as a strangeness $S=-1$ baryon with quantum numbers $I(J^P)=0(\frac{1}{2}^-)$. However, most models based on chiral effective theory and unitary suggest two nearby overlapping resonance poles. This two-pole picture for the $\Lambda(1405)$ is disputed by recent phenomenological fits to experimental data which require only a single pole, and quark models which typically predict a single pole. In this presentation I will discuss the first lattice QCD computation of the coupled channel $\Sigma\pi$-$N\bar{K}$ scattering amplitude in the $\Lambda(1405)$ region. At a heavier-than-physical pion mass of $m_{\pi} = 200\,{\rm MeV}$, the amplitude clearly exhibits a virtual bound state below $\Sigma\pi$ threshold and an additional resonance pole just below $N\bar{K}$ threshold. These poles are identified from parametrizations of the two-channel $K$-matrix which are fit to the finite volume energy spectrum and analytically continued to the complex plane. Our first-principles QCD results cannot be described by a single pole and thus support the two-pole picture suggested by $SU(3)$ chiral symmetry and unitarity.

Topical area Hadronic and Nuclear Spectrum and Interactions

Primary authors

Amy Nicholson (UNC, Chapel Hill) Andre Walker-Loud (LBNL) Andrew Hanlon (Physics Department, Brookhaven National Laboratory) Barbara Cid Mora (GSI) Ben Hörz (Nuclear Science Division, Lawrence Berkeley National Laboratory) Colin Morningstar (Carnegie Mellon University) Daniel Mohler (Fermilab) Fernando Romero-Lopez (MIT) John Bulava (Deutsches Elektronen-Synchrotron DESY) Joseph Moscoso (UNC, Chapel Hill) Sarah Skinner (Carnegie Mellon University)

Presentation materials