Speaker
Description
We study the weak decay of the $\Lambda_b$ baryon into $J/\psi \phi \Lambda$. This reaction is particularly interesting as it allows for the study of exotic or new hadron resonances in all the three two-particle channels (i.e, $J/\psi \phi$, $J/\phi \Lambda$ and $\phi \Lambda$).
It is interesting to study the final state interaction of $J/\psi$ and $\phi$, since as we know from experimental data that there are several exotic resonances in this channel. For the $\Lambda_b \rightarrow J/\psi \phi \Lambda$ decay, at the quark level, the most probable weak transition proceeds via the creation of a $\Lambda$ baryon and a $D^*_s \bar{D^*_s}$ pair that is linked via the $X(4160)$ resonance to the finally observed $J/\psi \phi$pair. A similar process involving resonance production via $X(4140)/X(4160)$ was considered in [1] but studying the $B^+ \rightarrow J/\psi \phi K^+$. We will show that exotic $X$ resonances can be clearly seen by studying the invariant mass spectrum of $J/\psi \phi$ pairs from $\Lambda_b \rightarrow J/\psi \phi \Lambda$ decay.
The hidden-charm pentaquark $P_C(4450)$, observed recently by the LHCb collaboration [2], may be of molecular nature, as advocated by some chiral unitary approaches that also predict pentaquark partners in the strangeness $S=-1$ sector [3]. This strange hidden charm pentaquark can be produced via $J/\psi \Lambda$ final state interaction in our reaction and, as we shall see, traces of such a state can be seen in the $\Lambda_b \rightarrow J/\psi \phi \Lambda$ decay by studying the invariant mass spectrum of $J/\psi \Lambda$ pairs. A similar study and conclusions have been performed in [4], but studying the $\Lambda_b \rightarrow J/\psi \eta \Lambda$ decay.
Finally, in the $\phi \Lambda$ invariant mass spectrum, we might look for the presence of a $\Lambda$ resonance around $2150 MeV$ that has been predicted in Ref [5] as dynamically generated in a chiral unitarity approach.
References:
[1] En Wang, Ju-Jun Xie, Li-Sheng Geng, and Eulogio Oset, Phys. Rev. D97, 014017 (2018).
[2] R. Aaij, B. [LHCb collaboration], Phys. Rev. Lett. 115, 072001 (2015).
[3] J.J. Wu, R. Molina, E. Oset and B.S. Zou, Phys. Rev. Lett. 105, 232001
(2010); Phys.Rev. C84, 015202 (2011).
[4] A. Feijoo, V.K. Magas, A. Ramos and E. Oset, Phys. Rev. D92, 076015
(2015).
[5] E. Oset and A. Ramos, Eur. Phys. J. A44, 445 (2010).
