Conveners
Parallel 2: Baryon spectrum through meson photoproduction and electro-production
- Nick Zachariou
Parallel 2: Baryon resonances in heavy ion collisions and their role in cosmology
- Angela Badala' (Istituto Nazionale di Fisica Nucleare)
Parallel 2: Quark-Diquark Models and/or Exotics
- Alessandro Pilloni (UniME & CT)
Parallel 2: Baryon resonances in experiments with hadron beams and in the e+e- collisions
- Stefano Spataro (Istituto Nazionale di Fisica Nucleare)
Parallel 2: Partial wave analysis
- Andrey Sarantsev (PNPI)
CLAS baryon spectroscopy programme
M. Dugger* (for the CLAS Collaboration)
Arizona State University,
College of Integrated Sciences and Arts
Mesa, AZ 85212-6415, USA
E-mail: dugger@jlab.org
One of the major thrusts in hadronic physics is to more fully
understand the internal structure of baryonic matter. The challenges
presented in understanding baryonic structure are large, in...
A good understanding of the spectrum and the properties of baryon resonances requires a detailed study of the excited states and their decays. To extract contributing resonances from data, cross sections and polarization observables must be determined and further investigated by partial wave analysis. Multi-meson final states are particularly important at high energies, where resonances are...
Recently structures in invariant mass distributions and excitation energy spectra have been attributed to triangular singularities as discussed in e.g., [1,2] and in the review by Guo et al. [3]. These singularities emerge under specific kinematic conditions when new reaction channels open up. It will be shown that a triangular singularity associated with the opening of the $\gamma p...
The exclusive double pion electromagnetic production is an important tool for the study of N and 𝛥 excitations and for the search of missing baryonic resonances. As far as photoproduction is concerned, the two pion channel represents the dominant contribution to the total cross section especially in the second resonant region, therefore the formation of resonances coupling directly to the 𝛾N...
Unlike stable hadrons, whose production yield in relativistic heavy-ion collisions is established by the temperature at the chemical freeze-out, hadron resonances are subject to final-state interactions occurring in the late hadron-gas phase of the collision after the chemical freeze-out. Processes such as the rescattering of the decay products and the regeneration are competing out of...
In this contribution a summary of the highlights of the recent experimental findings on strangeness production and dynamics will be presented.
Results obtained by different experimental collaborations spanning in
a large range in centre-of-mass energy and a variety of collision systems will be discussed. The talk does not aim at being a complete review, but rather at connecting the...
Light-flavor hadrons constitute the bulk of particle production in ultrarelativistic hadron-hadron collisions at the LHC. The study of their production yields, differential in transverse momentum and multiplicity, is fundamental to constrain hadron production models and to investigate the hadronization process. In this context, hadronic resonances are particularly interesting tools since they...
Accelerator experiments have reported the exotic hadrons that cannot be understood in the ordinary hadron picture, describing baryons as $qqq$ and mesons as $q\bar{q}$. The experimental observations indicate that the exotic hadrons have multiquark structures such as a compact multiquark, e.g. $qq\bar{q}\bar{q}$ and $qqqq\bar{q}$, and a hadron composite state called hadronic molecule. There...
Diquarks are often used as QCD effective degrees of freedom to describe nucleons and other baryons as well as exotic hadrons. Phenomenologically the splittings of the four possible diquark operators, grouped into three channels dubbed "good", "bad" and "not-even-bad", can be estimated from the experimentally observed spectrum in principle. Yet, despite the concept of diquarks being very old...
Electromagnetic dipole moments of fundamental particles provide powerful probes for physics within and beyond the Standard Model. For the case of short-lived particles these have not been experimentally accessible to date due to the difficulties imposed by their short lifetimes. Novel experimental techniques have been developed to allow a unique program of direct measurements of electric and...
In the past two decades there has been tremendous progress in the theoretical and experimental investigation of multiquark states, which has expanded our understanding of what a “hadron” is. Experimental evidence suggests that Nature does not only form “conventional” hadrons such as mesons as quark-antiquark states and baryons as three-quark states, but also more exotic combinations such as...
The experimental investigation of the low-energy negatively charged kaons interaction with the nuclear matter is very important to understand the strength of the K-nuclei interaction and to provide essential input for understanding of the non-perturbative QCD in the strangeness sector. It has strong consequences in various sectors of physics, like nuclear and particle physics as well as ...
QCD-motivated models for hadrons predict a wide variety of multi-quark states beyond ordinary mesons and baryons, known as exotic states.
The first observation of a heavy exotic state by Belle in 2003 has triggered a huge experimental effort, and the last 20 years have marked a turning point in the field.
To date, states composed of four and five valence quark have been observed and their...
The talk will provide an overview of the newly-obtained knowledge about the light-baryon spectrum, as well as of the energy-dependent partial-wave analysis models which have been used to attain said knowledge. Some details will be provided on how these models can be classified, in particular with regard to their incorporation of S-Matrix constraints. An outlook will be given at the end of the...
A new approach has been developed to energy-dependent, single-channel partial wave analysis which does not require constructing and solving elaborate theoretical model of analyzed two body reaction, but uses general principles of analyticity instead. Standard approach of obtaining energy dependent two body partial waves (multipoles) was to create a theoretical model, solve it, fit the free...
We study the two step sequential one pion production mechanism, $np(I = 0) \toπ^− pp$, followed by the fusion reaction $pp \to π^+ d$, in order to describe the $np \to π^+ π^− d$ reaction with $π^+ π^−$ in $I = 0$, where a narrow peak, so far identified with a “d(2380)” dibaryon, has been observed. We find that the second step $pp \to π^+ d$ is driven by a triangle singularity that determines...
