Related papers: Could the near-threshold $XYZ$ states be simply ki…
We demonstrate that the recently observed $X$, $Y$, $Z$ states cannot be purely from kinematic effect. Especially the narrow near-threshold structures in elastic channels call for nearby poles of the $S$-matrix which are qualified as…
The kinematics of a final state system with two invisible particles and two visible particles can develop cusped peak structures. This happens when the system has a fixed invariant mass (such as from a narrow resonant particle decay or with…
Physical states are characterised uniquely by their pole positions and the corresponding residues. Accordingly, in those parameters also the nature of the states should be encoded. For bound states (poles on the real $s$-axis below the…
In this work, we study the analytic properties of S-matrix for unstable particles, which is defined as the residues on the unphysical sheets where unstable poles reside. We demonstrate that anomalous thresholds associated with UV physics…
Phenomena such as state-swap, quadrature squeezing, entanglement and violation of entanglement inequalities are frequently reported to occur in quantum systems only. It is shown here that these effects can also occur in cholesteric liquid…
In many extensions of the SM, neutral massive stable particles (dark matter candidates) are produced at colliders in pairs due to an exact symmetry called a "parity". These particles escape detection, rendering their mass measurement…
We make use of a unitarized coupled-channel model to analyze the mass distribution data of final states in production processes of $X(4260)$. By analyzing the analytical structures of the decay amplitudes, we find that the line shape of…
We demonstrate how an effective density of states can be derived from the S-matrix describing a coupled-channel system. Besides the locations of poles, the phase of the determinant of the S-matrix encodes essential details in characterizing…
We investigate the anomalous triangle singularity (ATS) and its possible manifestations in various processes. We show that the ATS should have important impact on our understanding of the nature of some newly observed threshold states.…
Two-pole structures refer to the fact that two dynamically generated states are located close to each other between two coupled channels and have a mass difference smaller than the sum of their widths. Thus, the two poles overlap in the…
We consider the interplay of a quark state and a hadronic threshold in the framework of the P-matrix formalism, which is reviewed and extended for use together with conventional methods of computing quark-gluon dynamics. We provide a…
Three-step cascade decays into two invisible particles and two visible particles via two intermediate on-shell particles develop cusped peak structures in several kinematic distributions. We study the basic properties of the cusps and…
We demonstrate how S-matrix poles manifest themselves as the physical spectrum near the upper threshold in the context of the two-channel uniformized Mittag-Leffler expansion, an expression written as a sum of pole terms under an…
Feynman diagrams (notably the triangle diagram) involving heavy enough particles contain branch cuts on the physical sheet - anomalous thresholds - which, unlike normal thresholds and bound-state poles, do not correspond to any asymptotic…
Having in mind present uncertainty of the experimental situation in respect to exotic hadrons, it is important to discuss any possible theoretical arguments, pro and contra. Up to now, there are no theoretical ideas which could forbid…
Liquids in systems with spherically symmetric interactions are not thermodynamically stable when the range of the attraction is reduced sufficiently. However, these metastable liquids have lifetimes long enough that they are readily…
We study the nature of near-threshold eigenstates in systems with the attractive Coulomb plus short-range interactions. Using a model providing the Coulomb-modified effective range expansion, we analyze pole trajectories and the internal…
It is demonstrated that the candidate tetraquark states $Z_b(10610)$, $Z_b(10650)$, $Z_c(3900)$, and $Z_c(4025)$ are coupled channel cusp effects. The model explains in a natural way the masses and quantum numbers of the putative states and…
A simple model of the driven motion of interacting particles in a two dimensional random medium is analyzed, focusing on the critical behavior near to the threshold that separates a static phase from a flowing phase with a steady-state…
We investigate the survival probability of unstable states, the time-dependence of an initial state, in coupled channels. First, we extend the formulation of the survival probability from single channel to coupled channels (two channels).…