The European Physical Journal A最新文献

Understanding the substructure of atomic nuclei, particularly the clustering of nucleons inside them, is essential for comprehending nuclear dynamics. Various cluster configurations can emerge depending on excitation energy, the number and types of core clusters, and the presence of excess neutrons. Despite the prevalence of tightly bound cluster formations in low-lying states, understanding the correlation between clusters and their formation mechanisms remains incomplete. This exploring study investigates nuclear clustering at the electron–ion collider (EIC) using simulations based on the modified BeAGLE model. By simulating collisions involving (e+^{9})Be, (e+^{12})C, and (e+^{16})O nuclei, we find that the average energy of particles (langle E rangle ) and the system size ratios of particles at forward rapidity exhibit sensitivity to alpha clustering and its various configurations. These findings offer valuable insights into the dynamics of nuclear clustering and its implications for future studies at the EIC.

We emphasize the usefulness of treating delta resonances as explicit degrees of freedom in applications of chiral effective field theory (EFT) to parity-violating and time-reversal-violating (PVTV) nuclear interactions. Compared with the delta-less framework, the explicit inclusion of the delta isobar allows one to resum certain types of contributions to the PVTV two-pion exchange two- and three-nucleon potentials without at the same time introducing any unknown parameters up to next-to-next-to-leading order in the EFT expansion. We provide the corresponding expressions for the delta contributions in momentum and coordinate spaces and compare the convergence of the EFT expansion in both formulations.

Plasma Wakefield Acceleration (PWFA) is a highly promising method that can reduce the scale and cost of future electron–positron collider experiments. While significant breakthroughs have been achieved in electron acceleration both theoretically and experimentally, generating high-quality positron beams in plasma presents greater challenges. This paper reviews advanced positron acceleration schemes, including particle beam-driven wakefield acceleration, laser-driven wakefield acceleration, radiation acceleration, and hollow plasma channel acceleration. The hollow plasma channel scheme is a promising method that can provide stable and efficient acceleration of positrons, making it more advantageous for experimental implementation.

A strong effort will be dedicated in the coming years to extend the reach of ab initio nuclear-structure calculations to heavy doubly open-shell nuclei. In order to do so, the most efficient strategies to incorporate dominant many-body correlations at play in such nuclei must be identified. With this motivation in mind, the present work analyses the step-by-step inclusion of many-body correlations and their impact on binding energies of Calcium and Chromium isotopes. Employing an empirically-optimal Hamiltonian built from chiral effective field theory, binding energies along both isotopic chains are studied via a hierarchy of approximations based on polynomially-scaling expansion many-body methods. More specifically, calculations are performed based on (i) the spherical Hartree–Fock–Bogoliubov mean-field approximation plus correlations from second-order Bogoliubov many-body perturbation theory or Bogoliubov coupled cluster with singles and doubles on top of it, along with (ii) the axially-deformed Hartree–Fock–Bogoliubov mean-field approximation plus correlations from second-order Bogoliubov many-body perturbation theory built on it. The corresponding results are compared to experimental data and to those obtained via valence-space in-medium similarity renormalization group calculations at the normal-ordered two-body level that act as a reference in the present study. The spherical mean-field approximation is shown to display specific shortcomings in Ca isotopes that can be understood analytically and that are efficiently corrected via the consistent addition of low-order dynamical correlations on top of it. While the same setting cannot appropriately reproduce binding energies in doubly open-shell Cr isotopes, allowing the unperturbed mean-field state to break rotational symmetry permits to efficiently capture the static correlations responsible for the phenomenological differences observed between the two isotopic chains. Eventually, the present work demonstrates that polynomially-scaling expansion methods based on unperturbed states that possibly break (and restore) symmetries constitute an optimal route to extend ab initio calculations to heavy closed- and open-shell nuclei.

Spacelike and timelike generalized parton distributions (GPDs) have been investigated at charged-lepton accelerator facilities, for example, by the virtual Compton scattering and the two-photon process, respectively. In this work, we show the (pi ^pm ) and (pi ^0) production cross sections in neutrino (antineutrino) reactions (nu ,(bar{nu }) + N rightarrow ell + pi + N') for studying the GPDs of the nucleon by using the theoretical formalism of Pire, Szymanowski, and Wagner. The (pi ^pm )-production cross sections are useful for finding mainly gluon GPDs, whereas the (pi ^0) production probes quark GPDs, although there are sizable quark-gluon interference terms in the (pi ^pm ) production. In particular, we show the roles of the pion- and rho-pole terms, the contribution from each GPD term (H, E, ({tilde{H}}), ({tilde{E}})), the effects of the gluon GPDs (H_g) and (E_g), and the dependence on the energy of the process in the neutrino cross sections. These cross sections could be measured at Fermilab in future. The neutrino GPD studies will play a complementary role to the projects of charged-lepton and hadron reactions for determining the accurate GPDs.

The Large Hadron Collider (LHC) aims to inject oxygen (¹⁶O) ions in the next run into its experiments. This include the anticipated one-day physics run focusing on ({O+O},)collisions at center-of-mass energy (sqrt{s_{textrm{NN}}}=7) TeV . In this study, we have used recently developed version of the EPOS (EPOS4) to study the production of identified particles ((pi ^pm ), (K^pm ) and (p({overline{p}}))) in ({O+O},)collisions at (sqrt{s_{textrm{NN}}}=7) TeV . Predictions of transverse momentum (({p_{textrm{T}}},)) spectra, ({langle p_{textrm{T}} rangle },), integrated yield (({{mathrm d}N{/}{mathrm d}{textit{y}}},)) for different centrality classes are studied. To provide insight into the collective nature of the produced particles, we look into the ({p_{textrm{T}}},)-differential particle ratios ((K/pi ) and (p/pi )) and ({p_{textrm{T}}},)-integrated particle ratios to ((pi ^++pi ^-)) as a function of charge particle multiplicity. The shape of the charge particle multiplicity (({textrm{d}N_textrm{ch}/textrm{d}eta },)) and mean transverse momentum (({langle p_{textrm{T}} rangle },)) is well described by EPOS4. The predictions for the ratios of (K/pi ) and (p/pi ) from EPOS4 exhibit a systematic overestimation compared to the trends observed in ({p+p},), ({p+Pb},)and ({Pb+Pb},)systems as a function of charged-particle multiplicity. Interestingly, the ({O+O},)results of ({p_{textrm{T}}},)-integrated particle ratios shows a clear final state multiplicity overlap with ({p+p},), ({p+Pb},)and ({Pb+Pb},)collisions. EPOS4 does not only mimics signs of collectivity, but embeds collective expansion by construction, since it relies on relativistic hydrodynamics to model the evolution of the so-called core and is one of the suitable candidates to study ultra-relativistic heavy-ion collisions. Furthermore, the foreseen data from ({O+O},)collisions at the LHC, when available, will help to better understand the heavy-ion-like behavior in small systems as well as help to put possible constraints on the model parameters.

Bent Herskind was a Gamma-Ray Grand Master, who helped trigger the modern revolution in (gamma )-ray spectroscopy, opening the door to new vistas in nuclear structure physics. His story is a remarkable one and the contributions he made to the field in terms of its scientific richness and to the development of ever more powerful detector systems, were unique. The enthusiasm and excitement he put into everything were infectious and the brilliance of his insights was compelling. His legacy will live on, not only in the significant discoveries that he made, but also in the way he instilled his deep commitment to unravelling nature’s secrets in this quest and the pleasure of physics discovery with his close collaborators. This review article summarises his career and highlights some of his scientific achievements in which the authors had the privilege to collaborate with him.

Structure functions of the spin-1 deuteron will be investigated experimentally from the late 2020’s at various facilities such as Thomas Jefferson National Accelerator Facility, Fermi National Accelerator Laboratory, nuclotron-based ion collider facility, and electron-ion colliders. We expect that a new high-energy spin-physics field could be created by these projects. In this paper, the current theoretical status is explained for the structure functions of spin-1 hadrons, especially on parton distribution functions, transverse-momentum dependent parton distributions, and fragmentation functions. Related multiparton distribution functions are also shown.

We have revisited the region of the actinides in the vicinity of the neutron number N=152 and conducted high-precision mass measurements using the newly implemented Phase-Imaging Ion-Cyclotron-Resonance (PI-ICR) technique. The masses of (^{244})Pu and (^{249})Cf were found to deviate by 5.4 and 2.9 combined sigmas, respectively, from our previous results published in 2014. This indicates the presence of systematic errors in the earlier measurements. Consequently, we decided to remeasure all the nuclides from our 2014 study, along with (^{248})Cm, to ensure accuracy and reliability. With our greatly improved apparatus, we have measured the masses of (^{244})Pu, (^{241})Am, (^{243})Am, (^{248})Cm, and (^{249})Cf, using (^{208})Pb and (^{238})U as mass references. The masses of these reference ions were recently determined with ultra-high precision at Pentatrap. Our results were implemented in the latest Atomic Mass Evaluation (AME), showing good consistency. The region related to the masses measured in this study, especially for isotopes near the N=152 deformed shell gap, is discussed in terms of two-neutron separation energies, first excited 2(^+) energy levels and their differentials, as well as (delta V_{pn}) values, the average proton-neutron interaction of the most loosely bound two nucleons.

Oxygen is one of the most common elements in the human body. Proton beams used in therapy induce nuclear reactions that cause a loss of fluence along the beam path. These reactions often lead to production of (beta ^+) emitters with relatively short half-lives (less than 20 min). Cross sections for reactions on oxygen are not sufficiently known, particularly at proton energies above few tens of MeV. This contribution presents the results of an experiment, where silicon dioxide targets were used to study nuclear reactions induced by protons with energy below 60 MeV on oxygen. The proton beam was delivered by the AIC-144 cyclotron of the Institute of Nuclear Physics in Kraków. Cross sections of reactions leading to production of ( ^{11})C, ( ^{13})N and ( ^{15})O were obtained. They agree well with the measurements using Cherenkov radiation in bulk SiO(_2). The recent measurements performed with a PET scanner provided similar results, except in the case of ( ^{16})O(p,x)( ^{11})C reaction studied in the energy of up to 200 MeV, where our results are 30% lower.