Speaker
Dr
Kiyoshi Tanida
(Japan Atomic Energy Agency)
Description
Evidence for a narrow $\Lambda^*$ resonance at a mass of
about 1665 MeV (just above the combined mass of the $\Lambda$ ground
state plus the $\eta$ meson) has been seen in the $M(pK^-)$ mass of
the Dalitz plot for $\Lambda_c \to pK^-\pi^+$
decay at the Belle experiment [1].
Additional evidence for this resonance is found in the
partial-wave analysis (PWA) of data on $K^- p$ reactions
done independently by several groups [2-6], driven by
angular distributions of the $K^- p \to \Lambda\eta$ reaction
by the Crystal Ball collaboration [7].
If a narrow $\Lambda^*$ resonance exists at this mass,
then the conventional quark model cannot explain it,
and a possible explanation is that it is a crypto-exotic baryon
with a dominant meson-baryon component to its wave function.
Therefore we have proposed a definitive experiment for $K^- p \to
\Lambda \eta$, using the newly built hypTPC detector to establish
the existence of the proposed narrow $\Lambda(1665)$ and determine
its spin and parity in just two weeks of beamtime at J-PARC (P72).
We will discuss these evidences for the proposed $\Lambda^*$
resonance and introduce the P72 experiment.
[1] S. B. Yang {\em et al.} (Belle Collaboration),
Phys. Rev. Lett. {\bf 117}, 011801 (2016).
[2] H. Kamano, S.X. Nakamura, T.-S.H. Lee and T. Sato
Phys. Rev. C {\bf 90}, 065204 (2014).
[3] H. Kamano, S.X. Nakamura, T.-S.H. Lee and T. Sato
Phys. Rev. C {\bf 92}, 025205 (2015); {\it ibid.}, {\bf 95}, 049903 (2017).
[4] Bo-Chao Liu and Ju-Jun Xie, Phys. Rev. C {\bf 85}, 038201 (2012).
[5] Bo-Chao Liu and Ju-Jun Xie, Phys. Rev. C {\bf 86}, 055202 (2012).
[6] Jun Shi and Bing-Song Zou, Phys. Rev. C {\bf 91}, 035202 (2015).
[7] A. Starostin {\em et al.,} (Crystal Ball collaboration),
Phys. Rev. C {\bf 64}, 055205 (2001).
Author
Dr
Kiyoshi Tanida
(Japan Atomic Energy Agency)
