This paper describes my personal appreciation for some of the great research achievements of Mitya Diakonov, Vitya Petrov, and Maxim Polyakov, and how my own research career has followed the paths they opened. Among the topics where they have been the most influential have been the pursuit and study of the exotic pentaquark. The search for exotics may require a complementary approach, such as experimental and theoretical activity. Here, I would like to focus on a story of \(N(1680)\), a non-strange unitary partner of \({\mit \Theta }^+\), in which I was involved. Abstract Published by the Jagiellonian University 2025 authors

This review deals with measurements and future experiments of light pentaquark searches using hadron beams. Abstract Published by the Jagiellonian University 2025 authors

Collecting my memories below, I decided not to focus on particular physics ideas and their development over time, but to focus on what makes Dimitry Diakonov so special. Using his family background, based on linguistics and history, he developed over the years multiple interests and skills reaching far outside physics. Abstract Published by the Jagiellonian University 2025 authors

A factorization theorem for the hard coherent processes involving high-energy scattering of photons is derived. We elaborate the treatment for the case of the longitudinally polarized photons and extend the treatment to the case of the processes initiated by transversely polarized photons, as well as to the coherent photo-production of heavy quarkonia. A wave function of a hadron being the solution of the Schrödinger equation is presented in the space-time evolution of initially zero-size and zero-color charge wave packet of bare quarks and gluons. The increase of the running coupling constant in QCD with the distance leads to the coexistence of two phases within the hadron wave function. One phase is the pQCD phase, the second phase is dominated by the phenomenon of spontaneously broken chiral symmetry. The critical line at \(r=r_{\mathrm {c}}\) follows from the gauge symmetry, asymptotic freedom, causality, quantum diffusion, and from the cancellation of soft color fields outside the wave packet. The distinctive properties of QCD are the significant probability of a high-momentum tail of the minimal Fock component (MFC) of the hadron wave function and the strong suppression of the soft part of MFC of hadron WF in the strong coupling regime of QCD. The factorization theorems predict hard coherent processes, color transparency, color fluctuations phenomena, <span class="it">etc</span>. We argue that the value of the radius of the region occupied by the pQCD phase, \(r_{\mathrm {c}}\), is restricted by the radius of the onset of spontaneously broken chiral symmetry \(r_{\mathrm {c}}\gg r_{\mathrm {CS}}\). The success of the constituent quark model for a baryon suggests that the radius of the confinement of color is significantly larger than \(r_{\mathrm {c}}\). The presence of a color core in hadrons matches well with preQCD field theories at distances larger than the critical line for the onset of the regime of spontaneously broken chiral symmetry. It substitutes Landau nullification of the interaction within preQCD field theories, the preQCD Feynman model at the distances smaller than \(r_{\mathrm {c}}\). Abstract Published by the Jagiellonian University 2025 authors

Dmitry Diakonov, Victor Petrov, and Maxim Polyakov were my colleagues and collaborators. Mitya and Vitya were also, and maybe first of all, my close personal friends for many many years. What follows is a mixture of some recollections and a review of our joint works. Abstract Published by the Jagiellonian University 2025 authors

We present prospects for the \({\mit \Theta }^+\) pentaquark baryon search using the newly constructed LEPS2 facility at SPring-8. The LEPS2 detector system features significant improvements in acceptance for multi-particle final states compared to previous experiments. Our search employs two complementary strategies: direct production in the \(\gamma n \to K^-{\mit \Theta }^+\) reaction using a liquid deuterium target with a photon beam up to 2.4 GeV, and \(\bar {K}^{*0}\)-associated \({\mit \Theta }^+\) production using a liquid hydrogen target with a photon beam up to 2.9 GeV. The extended acceptance covers both forward and large-angle regions, effectively spanning the kinematic regions explored by previous LEPS and CLAS experiments. The large acceptance and improved resolution of LEPS2, combined with these complementary approaches, provide unprecedented sensitivity for establishing the existence of the \({\mit \Theta }^+\) or placing definitive upper limits on its production. Abstract Published by the Jagiellonian University 2025 authors

The gravitational form factors of the deuteron are calculated in the framework of non-relativistic chiral effective field theory. Non-relativistic reduction of the matrix element of the energy-momentum tensor operator for spin-one systems is worked out, and the gravitational form factors of the deuteron are extracted from the three-point function of the energy-momentum tensor using the LSZ reduction formula. The obtained form factors are compared to results of model calculations available in the literature. Abstract Published by the Jagiellonian University 2025 authors

An iterative adiabatic time-dependent Hartree–Fock–Bogoliubov (ATDHFB) method is developed within the framework of the Skyrme density functional theory. The ATDHFB equation is solved iteratively to avoid explicitly calculating the stability matrix. The contribution of the time-odd mean fields to the ATDHF(B) moment of inertia is incorporated self-consistently, and the results are verified by comparing them with the dynamical cranking predictions. The inertia mass tensor is calculated with the density-derivative term evaluated by numerical differentiation. Abstract Published by the Jagiellonian University 2025 authors

The level scheme of the neutron-rich \(^{87}\)Se isotope has been extended up to 2397 keV excitation energy. The isotope of interest was produced in a neutron-induced fission reaction of a \(^{235}\)U target at the Institut Laue-Langevin in Grenoble. During the analysis, six new gamma transitions were identified by employing multifold gamma-ray coincidence relationships, measured with the FIPPS array. Based on the gamma angular correlations technique, tentative spin-parity assignments have been proposed for the low-lying levels. Abstract Published by the Jagiellonian University 2025 authors

Besides the level scheme, absolute transition strengths between excited states yield fundamental information on nuclear structure and can be determined from level lifetimes. The recoil distance Doppler-shift (RDDS) technique is very valuable for the measurement of lifetimes in the picosecond range. During the last years, our group constructed several very compact plunger devices for RDDS experiments with \(\gamma \)-ray spectrometers coupled to charged particle detector arrays situated in the target chamber, and with dedicated setups for multinucleon transfer reactions where the plunger must be placed at the grazing angle of the reaction. Recent investigations have addressed the evolution of nuclear structure in neutron-deficient nuclei in the \(A=170\) mass region from yrast \(B\)(E2) values and are discussed in this article. For these investigations very small \(B_{4/2} = B(\mathrm {E2};4_1^+ \to 2_1^+)/B(\mathrm {E2};2_1^+ \to 0_1^+)\) ratios are of particular interest, which cannot be explained with standard collective models and which are not expected from the actual level schemes nor this far from closed shells. Here, we present our new work on \(^{168}\)W, \(^{172}\)Pt, and \(^{176}\)Pt, focus on this \(B\)(E2) anomaly, and include \(B\)(E2) values between higher yrast states for which experimental data have been sparse. Abstract Published by the Jagiellonian University 2025 authors

The generator coordinate method (GCM) is a well-known method to describe nuclear collective motions. In this method, one needs to specify <span class="it">a priori</span> the relevant collective degrees of freedom as input of the method, based on empirical and/or phenomenological assumptions. Recently, we extended the GCM to include simultaneous optimization of both the basis Slater determinants and the weight factors based on the variational principle. This extension allows for the automatic optimization of the collective subspace. In this study, we apply the extended GCM to analyze \(^{20}\)Ne using the Skyrme interaction. We demonstrate that the optimized basis states correspond to excited states along a collective path, in contrast to the conventional GCM, which typically superposes only local ground states. We further calculate the low-lying excited states with the angular momentum projection and discuss the capabilities of the extended method. Abstract Published by the Jagiellonian University 2025 authors

In recent years, several cases of nuclei presenting the so-called “\(B_{4/2}\) anomaly” have been observed in the neutron-deficient region close to \(Z=50\) and \(Z=82\). In the last region, the osmium isotopic chain is of particular interest, as three consecutive isotopes, \(^{168,169,170}\)Os, have shown the presence of this peculiar phenomenon. An experiment aimed at extending the study to \(^{167}\)Os was performed at the Accelerator Laboratory of the University of Jyväskylä, using a beam of \(^{78}\)Kr at 360 MeV impinging on a \(^{92}\)Mo target. Lifetimes of several low-lying states were measured using the Recoil-Distance Doppler Shift method. The preliminary analysis and the study of the influence of unobserved feeders are discussed. Abstract Published by the Jagiellonian University 2025 authors

The neutrinoless double-beta decay (\(0\nu \beta \beta \)) nuclear matrix elements (NMEs) cannot be directly deduced from any experimental data, and their reliable calculation remains a significant challenge for the nuclear physics community. Advanced nuclear structure approaches have been developed and applied to evaluate nuclear transitions of experimental interest. However, the calculated values of \(0\nu \beta \beta \) NMEs still vary widely among different methods, affecting predictions of decay rates and constraints on various lepton violation parameters. The two-neutrino double-beta (\(2\nu \beta \beta \)) decay, which has been experimentally confirmed for eleven isotopes, plays a crucial role in testing nuclear structure models. In this context, we present the modified formalism of the Second Tamm–Dancoff Approximation (STDA) for the calculation of double-beta decay transitions. For \(2\nu \beta \beta \) of \({^{48}}\)Ca, the corresponding NMEs are calculated within the STDA, and their dependence on relevant nuclear structure parameters is investigated. Our findings indicate that a significant quenching of the axial-vector coupling constant is necessary to accurately reproduce the half-life of \(2\nu \beta \beta \) decay. Abstract Published by the Jagiellonian University 2025 authors

The structure of the low-lying quadrupole bands in \(^{180}\)Hf and \(^{182}\)W is investigated with the use of a microscopically derived IBM-1 Hamiltonian. For each isotope, a potential energy curve is constructed from self-consistent mean-field calculations, employing a Skyrme energy density functional. The fermionic potential energy curve is subsequently mapped onto the corresponding bosonic one, thus leading to the derivation of the IBM-1 Hamiltonian parameters. These parameters are then used as inputs for the calculation of energy spectra and \(B\)(E2) transition strengths for the ground state and \(\gamma \) bands in the examined isotopes. The results are compared to experimental data, showing an overall good agreement. Potential future applications of this mapping method are also discussed. Abstract Published by the Jagiellonian University 2025 authors

We discuss the GUDE functionals which consist of pion exchanges derived from chiral effective field theory and a Skyrme-like part. Certain pion terms lead to significant improvements in the description of ground-state energies, indicating they might be useful ingredients for true <span class="it">ab initio</span> energy density functionals. In addition, we present estimates of the statistical parameter uncertainties of the GUDE functionals. Abstract Published by the Jagiellonian University 2025 authors

A new electron–positron pair spectrometer has been designed and constructed for the simultaneous measurement of the energy and angular correlations of \(e^+e^-\) pairs from internal pair creation processes (IPC) of energetic nuclear transitions. Experiments were carried out to validate the performance of the spectrometer using the \(e^+e^-\) pairs from M1 transitions in the \(^7\)Li(\(p,\gamma )^8\)Be and an E0 transition in the \(^{19}\)F(\(p,\alpha ,e^+e^-)^{16}\)O reaction. Comparison with <span class="sf">Geant4</span> Monte Carlo simulations demonstrates that the angular correlations of \(e^+e^-\) pairs can be determined with sufficient resolution and efficiency between a correlation angle of \(40^\circ \) and \(180^\circ \) degrees. Abstract Published by the Jagiellonian University 2025 authors

The complete fusion (CF), incomplete fusion (ICF), and neutron transfer (\(1n\) stripping, \(2n\) stripping, and \(1n\) pickup) cross sections for the \(^{7}\mathrm {Li}+{^{205}\mathrm {Tl}}\) system were measured at energies around the Coulomb barrier by the online \(\gamma \)‑ray detection technique. The measured CF cross sections were found to be suppressed at above-barrier energies compared to the one-dimensional barrier penetration model (1DBPM) as well as coupled channel (CC) calculations. However, measured CF cross sections at below-barrier energies are found to be enhanced compared to 1DBPM and are in reasonable agreement with the CC calculations. The suppression observed in CF cross sections at above-barrier energies is found to be commensurate with the measured total ICF cross sections. Among ICF cross sections, \(t\)-capture is found to be dominant over \(\alpha \)-capture at all the measured energies. It is also observed that ICF is dominant at below-barrier, while CF dominates at above-barrier energies. Measured neutron transfer cross sections were compared with coupled reaction channel (CRC) calculations and found to be in agreement. The cumulative sum of all measured observables CF, ICF, and neutron transfer cross sections was found to agree with the estimated reaction cross sections. Abstract Published by the Jagiellonian University 2025 authors

The low-lying electric dipole strength in \(^{111-113,116-122,124}\)Sn was extracted with the Oslo method to systematically investigate the pygmy dipole resonance (PDR) and its evolution in Sn isotopes. The nuclear level densities (NLD) and the \(\gamma \)-ray strength functions (GSF) obtained from the Oslo data were used as inputs in the <span class="sf">TALYS</span> reaction code to produce radiative neutron-capture cross sections, Maxwellian-averaged cross sections, and rates relevant for the heavy-element nucleosynthesis. Despite a relatively small observed impact of the PDR, the experimentally extracted \(^{121,123}\)Sn(\(n,\gamma \)) \(^{122,124}\)Sn cross sections provide a notable reduction of a currently available theoretical uncertainty for the abundances of Sb isotopes in the i-process simulations. Abstract Published by the Jagiellonian University 2025 authors

Data on the structure of sulphur isotopes close to the neutron drip-line are rather scarce. The excited states of the very neutron-rich \(^{46}\)S and \(^{47}\)S nuclei have been investigated by in-beam gamma-ray spectroscopy at the Radioactive Isotope Beam Factory at the RIKEN Nishina Center. After multi-nucleon knockout reactions on the liquid-hydrogen MINOS target, the \(2^{+}_{1}\rightarrow 0^{+}_{1}\) gamma transition of \(^{46}\)S, already reported in literature, has been confirmed. Additionally, two new gamma rays have been assigned to this isotope and one gamma line has been observed in \(^{47}\)S. Abstract Published by the Jagiellonian University 2025 authors

The high-energy \(\gamma \) rays from the Giant Dipole Resonance (GDR) decay of \(^{56,60,62}\mathrm {Ni}^{*}\) nuclei at finite temperature between approximately 1.5 and 2 MeV, produced in the \(^{32,34,36}\mathrm {S}+{^{24,26}\mathrm {Mg}}\) reactions at bombarding energies between 78 and 90 MeV, were measured. The experiment was then analyzed with a statistical model using a Monte Carlo approach. Some evidence is found within the analysis on the presence of an extra yield on the tail of the Giant Dipole Resonance which may be attributed to a Pygmy Dipole Resonance in an excited nucleus. Abstract Published by the Jagiellonian University 2025 authors