Hidden charm pentaquark and Λ(1405)\Lambda(1405) in the Λb0→ηcK−p(πΣ)\Lambda^0_b \to \eta_c K^- p (\pi \Sigma) reaction

We have performed a study of the $\Lambda^0_b \to \eta_c K^- p$ and $\Lambda^0_b \to \eta_c \pi \Sigma$ reactions based on the dominant Cabibbo favored weak decay mechanism. We show that the $K^- p$ produced only couples to $\Lambda^*$ states, not $\Sigma^*$ and that the $\pi \Sigma$ state is only generated from final state interaction of $\bar{K}N$ and $\eta \Lambda$ channels which are produced in a primary stage. This guarantees that the $\pi \Sigma$ state is generated in isospin $I=0$ and we see that the invariant mass produces a clean signal for the $\Lambda(1405)$ of higher mass at $1420$ MeV. We also study the $\eta_c p$ final state interaction, which is driven by the excitation of a hidden charm resonance predicted before. We relate the strength of the different invariant mass distributions and find similar strengths that should be clearly visible in an ongoing LHCb experiment. In particular we predict that a clean peak should be seen for a hidden charm resonance that couples to the $\eta_c p$ channel in the invariant $\eta_c p$ mass distribution.Comment: 8 pages, 7 figure

Bˉ0\bar B^0, B−B^- and Bˉs0\bar B^0_s decays into J/ψJ/\psi and KKˉK \bar K or πη\pi \eta

We study the $\bar B^0_s \to J/\psi K^+ K^-$, $\bar B^0 \to J/\psi K^+ K^-$, $B^- \to J/\psi K^0 K^-$, $\bar B^0 \to J/\psi \pi^0 \eta$ and $B^- \to J/\psi \pi^- \eta$ decays and compare their mass distributions with those obtained for the $\bar B^0_s \to J/\psi \pi^+ \pi^-$ and $\bar B^0 \to J/\psi \pi^+ \pi^-$. The approach followed consist in a factorization of the weak part and the hadronization part into a factor which is common to all the processes. Then what makes the reactions different are some trivial Cabibbo-Kobayashi-Maskawa matrix elements and the weight by which the different pairs of mesons appear in a primary step plus their final state interaction. These elements are part of the theory and thus, up to a global normalization factor, all the invariant mass distributions are predicted with no free parameters. Comparison is made with the limited experimental information available. Further comparison of these results with coming LHCb measurements will be very valuable to make progress in our understanding of the meson-meson interaction and the nature of the low lying scalar meson resonances, $f_0(500), f_0(980)$ and $a_0(980)$.Comment: 12 pages, 6 figures; v2: discussion added, references added, final version published in EPJ

Production and mixing of scalar mesons in ηc\eta_c and χc1\chi_{c1} decays

We briefly discuss how the chiral unitary approach in coupled channels and $SU(3)$ symmetry can be used to describe the production of $f_0(500)$, $f_0(980)$ and $a_0(980)$ in the $\chi_{c1} \to \eta \pi^+ \pi^-$ reaction, recently measured by the BESIII collaboration. In this reaction a very strong peak for the $a_0(980)$ can be seen in the $\eta\pi$ invariant mass, while clear signals for the $f_0(500)$ and $f_0(980)$ appear in the one of $\pi^+\pi^-$. Next, we show the predictions made with the same model for the analogous decay $\eta_c \to \eta \pi^+ \pi^-$, which could also be measured experimentally. We discuss the differences of these two reactions which are interesting to test the picture where these scalar mesons are dynamically generated from the interaction of pairs of pseudoscalars. Furthermore, we comment on a new recent work where the same model was used to study the $a_0(980) - f_0(980)$ mixing in the $\chi_{c1} \to \pi^0 \pi^0 \eta$ and $\chi_{c1} \to \pi^0 \pi^+ \pi^-$ reactions, showing that quantitative agreement with the experimental measurement of this mixing, also performed by BESIII, can be obtained, revealing interesting aspects of the dynamics of this process and the importance of coupled channels.Comment: Talk presented at the XVII International Conference on Hadron Spectroscopy and Structure - Hadron2017, 25-29 September, 2017, University of Salamanca, Salamanca, Spain. arXiv admin note: substantial text overlap with arXiv:1707.0722

VERSA: A Tool for the Specification and Analysis of Resource-Bound Real-Time Systems

VERSA is a tool that assists in the algebraic analysis of real-time systems. It is based on ACSR, a timed process algebra designed to express resource-bound real-time distributed systems. VERSA supports the analysis of real-time processes through algebraic rewriting, interactive execution, and equivalence testing. This paper begins by presenting a brief overview of the process algebra ACSR, its syntax, operational semantics, and equivalence relations. VERSA\u27S process and command syntax, its algebraic rewrite system, and its state-based analysis features are described fully. The presentation includes examples that illustrate the salient features of ACSR, and output from sample VERSA sessions that demonstrate the application of the tool to real-time systems analysis