Search

Khuri-Treiman equations have proven to be a useful theoretical tool in the analysis of three-body decays, especially into the 3π final state. In this work we present in full detail the necessary generalization of the formalism to study the decays of particles with arbitrary spin, parity, and charge conjugation. To this extent, we find it most convenient to work with helicity amplitudes instead of the so-called invariant amplitudes, especially when dealing with the unitarity relations. The isobar expansions in the three possible (s-, t-, and u-) final channels are related with the appropriate crossing matrices. We pay special attention to the kinematical singularities and constraints of the helicity amplitudes, showing that these can be derived by means of the crossing matrix. [ABSTRACT FROM AUTHOR]

We investigate the properties of the hidden-charm pentaquark-like resonances first observed by the LHCb Collaboration in 2015, by measuring the polarization transfer KLL between the incident photon and the outgoing proton in the exclusive photoproduction of J/ψ near threshold. We present a first estimate of the sensitivity of this observable to the pentaquark photocouplings and hadronic branching ratios, and extend our predictions to the case of the initial-state helicity correlation ALL, using a polarized target. These results serve as a benchmark for the SBS experiment at Jefferson Lab, which proposes to measure for the first time the helicity correlations ALL and KLL in J/ψ exclusive photoproduction, in order to determine the pentaquark photocouplings and branching ratios. [ABSTRACT FROM AUTHOR]

The next generation of electron-hadron facilities has the potential for significantly improving our understanding of exotic hadrons. The XYZ states have not been seen in photon-induced reactions so far. Their observation in such processes would provide an independent confirmation of their existence and offer new insights into their internal structure. Based on the known experimental data and the well-established quarkonium and Regge phenomenology, we give estimates for the exclusive cross sections of several XYZ states. For energies near threshold we expect cross sections of few nanobarns for the Zc(3900)+ and upwards of tens of nanobarns for the X(3872), which are well within reach of new facilities. [ABSTRACT FROM AUTHOR]

We present a general formalism to write the decay amplitude for multibody reactions with explicit separation of the rotational degrees of freedom, which are well controlled by the spin of the decay particle, and dynamic functions on the subchannel invariant masses, which require modeling. Using the three-particle kinematics we demonstrate the proposed factorization, named the Dalitz-plot decomposition. The Wigner rotations, which are subtle factors needed by the isobar modeling in the helicity framework, are simplified with the proposed decomposition. Consequently, we are able to provide them in an explicit form suitable for the general case of arbitrary spins. The only unknown model-dependent factors are the isobar line shapes that describe the subchannel dynamics. The advantages of the new decomposition are shown through three examples relevant for the recent discovery of the exotic charmonium candidate Zc(4430), the pentaquarks Pc, and the intriguing Λ+c→pK-π+ decay. [ABSTRACT FROM AUTHOR]