The European Physical Journal A最新文献

{"title":"Quadrupole–hexadecapole coupling in the rare earth region with beyond mean field correlations","authors":"R. Rodríguez-Guzmán,&nbsp;L. M. Robledo","doi":"10.1140/epja/s10050-025-01638-x","DOIUrl":"10.1140/epja/s10050-025-01638-x","url":null,"abstract":"<div><p>The roles of static hexadecapole deformation and beyond-mean-field quadrupole–hexadecapole configuration mixing are studied for a selected set of Yb, Hf, W and Os isotopes within the mass range <span>(170 le A le 202)</span>, using the Hartree–Fock–Bogoliubov (HFB) and the two-dimensional Generator Coordinate Method (2D-GCM) approaches, based on the Gogny energy density functional. The 2D-GCM ground and excited states of the lighter isotopes are associated with diamond-like shapes while, for each isotopic chain, a region where those states correspond to square-like shapes has been found below the neutron shell closure <span>(N=126)</span>. It is shown, that for the studied nuclei the quadrupole and hexadecapole degrees of freedom are interwoven in the ground and excited states up to the mass number <span>(A=184{-}188)</span>. This structural evolution, encoded in the 2D-GCM collective wave functions, is accompanied by an enhanced prolate-oblate shape coexistence around the neutron number <span>(N=116)</span>. In agreement with previous studies, it is also shown that for the considered Yb, Hf, W and Os isotopes the inclusion of hexadecapole deformation in the ground state dynamics leads to a non trivial additional correlation energy comparable to the quadrupole correlation energy itself.</p></div>","PeriodicalId":786,"journal":{"name":"The European Physical Journal A","volume":"61 7","pages":""},"PeriodicalIF":2.8,"publicationDate":"2025-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epja/s10050-025-01638-x.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145166074","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Neutron emission spectra measurement from proton bombardment of thick carbon target","authors":"Yingyi Liu,&nbsp;Xichao Ruan,&nbsp;Jie Bao,&nbsp;Qi Sun,&nbsp;Jincheng Wang,&nbsp;Jie Ren,&nbsp;Hongyi Wu,&nbsp;Shiliang Xiao,&nbsp;Hanxiong Huang,&nbsp;Haolan Yang,&nbsp;Haotian Luo,&nbsp;Xiaoyu Wang,&nbsp;Hao Guo,&nbsp;Wenlin Li,&nbsp;Boyu Tan,&nbsp;Hao Wang","doi":"10.1140/epja/s10050-025-01601-w","DOIUrl":"10.1140/epja/s10050-025-01601-w","url":null,"abstract":"<div><p>The double-differential thick-target neutron yields (DDTTNY) for proton-induced reactions on thick carbon target were measured at 10.7 MeV, 12.9 MeV, and 14.0 MeV proton energies using the time-of-flight (TOF) method. Measurements were performed at 18 emission angles ranging from 0<span>(^{circ })</span> to 145<span>(^{circ })</span> with EJ301 liquid organic scintillation detectors. The angular distribution of neutron yields was obtained by integrating the DDTTNY spectra above the detection threshold. The total neutron yield was derived by fitting the angular distribution with Legendre polynomials. Monte Carlo simulations of neutron yields were carried out using FLUKA and MCNP codes. The simulated results were compared with experimental data, showing that the MCNP results based on the CEM physical model exhibit better agreement with experimental data in the low-energy region. In contrast, FLUKA with the PEANUT physical model underestimate neutron yields at larger angles.</p></div>","PeriodicalId":786,"journal":{"name":"The European Physical Journal A","volume":"61 7","pages":""},"PeriodicalIF":2.8,"publicationDate":"2025-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145166641","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Simplified and more efficient computations of angular-momentum-coupled Goldstone diagrams","authors":"S. L. Jin,&nbsp;J. H. Hou,&nbsp;F. R. Xu","doi":"10.1140/epja/s10050-025-01637-y","DOIUrl":"10.1140/epja/s10050-025-01637-y","url":null,"abstract":"<div><p>Motivated by the work of Kuo et al. (Ann Phys 132:237–276, 1981), we develop a simple method to compute Goldstone diagrams in the angular momentum coupled scheme. By redefining the cross-coupled matrix elements, we leverage symmetry properties more effectively, leading to simplified diagram factorization rules and promoted computational efficiency. We have successfully applied the rules to one-body tensor operators, and extended similar formulations to two-body tensor operators beyond the work of Kuo et al. (1981).</p></div>","PeriodicalId":786,"journal":{"name":"The European Physical Journal A","volume":"61 7","pages":""},"PeriodicalIF":2.8,"publicationDate":"2025-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145165381","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A deep neural network approach to solve the Dirac equation","authors":"Chuanxin Wang,&nbsp;Tomoya Naito,&nbsp;Jian Li,&nbsp;Haozhao Liang","doi":"10.1140/epja/s10050-025-01630-5","DOIUrl":"10.1140/epja/s10050-025-01630-5","url":null,"abstract":"<div><p>We extend the method from [Naito, Naito, and Hashimoto, Phys. Rev. Research <b>5</b>, 033189 (2023)] to solve the Dirac equation not only for the ground state but also for low-lying excited states using a deep neural network and the unsupervised machine learning technique. The variational method fails because of the Dirac sea, which is avoided by introducing the inverse Hamiltonian method. For low-lying excited states, two methods are proposed, which have different performances and advantages. The validity of this method is verified by the calculations with the Coulomb and Woods-Saxon potentials.</p></div>","PeriodicalId":786,"journal":{"name":"The European Physical Journal A","volume":"61 7","pages":""},"PeriodicalIF":2.8,"publicationDate":"2025-07-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145165382","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Multiple rescattering effects in the hard knockout reaction (mathbf {^2})H(varvec{(p,2p)n})","authors":"A. B. Larionov","doi":"10.1140/epja/s10050-025-01631-4","DOIUrl":"10.1140/epja/s10050-025-01631-4","url":null,"abstract":"<div><p>The interaction of a proton with a deuteron is the simplest nuclear reaction. However, it allows the study of precursors of nuclear medium effects such as initial-state/final-state interactions (ISI/FSI). In case of hard proton knockout, the deviation of ISI/FSI from the ’standard’ values may carry a signal of color transparency. In this regard, it is important to define the ’standard’ as precisely as possible. This work continues previous studies within the framework of the Generalized Eikonal Approximation (GEA). The focus is on processes where the participating protons experience multiple soft rescattering on the spectator neutron. It is shown that correct treatment of deviations of the trajectories of outgoing protons from the longitudinal direction leads to a significant modification of partial amplitudes with soft rescattering of two outgoing protons and non-vanishing amplitudes with rescattering of incoming and outgoing protons. The new treatment of multiple rescattering is important in kinematics with a forward spectator neutron.</p></div>","PeriodicalId":786,"journal":{"name":"The European Physical Journal A","volume":"61 7","pages":""},"PeriodicalIF":2.8,"publicationDate":"2025-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145165053","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Exploring freezeout dynamics and deconfinement in (Au+Au) collisions using STAR data","authors":"Pei-Pin Yang,&nbsp;M. Waqas,&nbsp;Muhammad Ajaz,&nbsp;Wei Xie,&nbsp;Jihane Ben Slimane,&nbsp;Haifa I. Alrebdi,&nbsp;Abd Al Karim Haj Ismail","doi":"10.1140/epja/s10050-025-01633-2","DOIUrl":"10.1140/epja/s10050-025-01633-2","url":null,"abstract":"<div><p>The transverse momentum distribution of <span>(pi ^+)</span>, <span>(K^+)</span>, and <i>p</i> are analyzed in the most central Gold-Gold, <span>(Au-Au)</span>, collisions over a wide energy range by the Tsallis distribution with transverse flow velocity. Analysis has been done on the experimental data estimated by STAR Collaboration, which ranges from <span>(sqrt{s_{NN}})</span> = 7.7 to 200 GeV. The freezeout parameters namely, the kinetic freezeout temperature, <i>T</i>, transverse flow velocity, <span>(beta _T)</span>, and the non-extensive related parameter, <span>(n_0)</span>, are obtained. The kinetic freezeout temperature is common for all the particles. Besides, other parameters such as the initial temperature of emission sources, mean transverse momentum, and chemical freezeout temperature, <span>(T_{ch})</span>, along with some thermodynamic quantities including the particle number density, <i>n</i>, squared sound speed, <span>(c^2_s)</span>, energy density, <span>(varepsilon )</span>, pressure, <i>P</i>, and entropy density, <i>s</i>, are extracted. We examine how each of these parameters behave in relation to energy. As the collision energy grows at the Relativistic Heavy Ion Collider (RHIC), the parameters <span>(T_i)</span>, <span>(varepsilon )</span>, <i>n</i>, <i>P</i>, and <i>s</i>, all rise steadily, however, at certain energies, the parameters <i>T</i>, <span>(beta _T)</span>, <span>(n_0)</span>, <span>(T_{ch})</span>, <span>( langle p_T rangle )</span>, and <span>(c^2_s)</span> reveals a pattern of compression. According to this saturation, the shift in phase for partial deconfinement and complete deconfinement have onset energies of 7.7 and 39 GeV, respectively. Furthermore, the distinction between the above three types of temperatures is investigated, and we found that their trends with fluctuating energy is not homogeneous. We also reveal the system’s evolution in <span>(Au-Au)</span> collisions by showing that <span>(T_i)</span> is larger than <span>(T_{ch})</span>, and the latter is larger than <i>T</i>.</p></div>","PeriodicalId":786,"journal":{"name":"The European Physical Journal A","volume":"61 7","pages":""},"PeriodicalIF":2.8,"publicationDate":"2025-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145165328","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A method for determining the charge yield distribution of fission fragments based on K-means clustering algorithm","authors":"J. Ma,&nbsp;Y. N. Li,&nbsp;X. X. Yu,&nbsp;S. J. Cheng,&nbsp;H. C. Qin,&nbsp;C. Han,&nbsp;D. Y. Huo,&nbsp;S. Y. Zhang,&nbsp;Y. X. Wang,&nbsp;Z. E. Yao,&nbsp;Z. Wei,&nbsp;Y. Zhang","doi":"10.1140/epja/s10050-025-01636-z","DOIUrl":"10.1140/epja/s10050-025-01636-z","url":null,"abstract":"<div><p>Measurement of the fission fragments charge yield distribution has been a longstanding challenge in independent yield distribution research, as traditional particle charge identification methods prove inadequate for this application. In this work, we propose a novel method for determining charge yield distribution using the K-means clustering algorithm, which relies on the simulation data of the multi-software coupled simulation of the velocity-kinetic energy (<i>v–E</i>) method fission spectrometer. Simulations of the fission reaction of ²³⁸U induced by 14 MeV neutron were conducted. By processing the pulse waveforms of individual mass chains with K-means clustering algorithm, the charge yield distribution is obtained. The results indicate that variations in the pulse signals of fission fragments within the same mass chain, following timing shift correction, primarily originate from charge differences. The influence of the number of clusters on clustering performance was analyzed, demonstrating that optimal results were achieved at <i>k</i> = 4, with a Root Mean Square Error (RMSE) of 6.95 × 10^–3 and an Error Ratio (ER) of 29.26%. Reduced sampling rates resulted in progressively degraded clustering performance. The method based on the K-means clustering algorithm developed in this work demonstrates high accuracy in charge yield distribution, thereby establishing a foundation for future high-quality independent yield distribution measurements.</p></div>","PeriodicalId":786,"journal":{"name":"The European Physical Journal A","volume":"61 7","pages":""},"PeriodicalIF":2.8,"publicationDate":"2025-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145165054","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Decay properties of the fission isomer (^{text {236m}})U","authors":"P. Reiter,&nbsp;D. Habs,&nbsp;D. Schwalm,&nbsp;P. G. Thirolf","doi":"10.1140/epja/s10050-025-01634-1","DOIUrl":"10.1140/epja/s10050-025-01634-1","url":null,"abstract":"<div><p>The delayed <span>(gamma )</span> decay and delayed fission of the shape isomer <span>(^{236m})</span>U were measured using the Heidelberg-Darmstadt Crystal Ball spectrometer. It is demonstrated that the isomeric <span>(gamma )</span> decay and the delayed fission represent two competing decay channels of the same isomeric state. This conclusion is supported by four independent observations: (i) the measured half-lives of the delayed <span>(gamma )</span> decay and delayed fission are identical, (ii) the excitation energy of the isomer is the same for both decay pathways, (iii) the missing energy in the prompt energy balance is equal for both decays, and (iv) the prompt energy spectra populating the second minimum are in agreement. An improved statistical analysis of the <span>(gamma )</span> decay indicates that the excitation energy of the isomeric ground state in the second minimum is <span>(2814 pm 33)</span> keV. The <span>(gamma )</span> back decay proceeds through several cascades involving known <span>(1^-)</span> states of the normally deformed <span>(^{236})</span>U. A direct single-step <span>(gamma )</span> transition is excluded within the experimental sensitivity.</p></div>","PeriodicalId":786,"journal":{"name":"The European Physical Journal A","volume":"61 7","pages":""},"PeriodicalIF":2.8,"publicationDate":"2025-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epja/s10050-025-01634-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145164651","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hydrodynamic description of direct photon spectrum and elliptic flow in Pb + Pb collisions at LHC","authors":"Sándor Lökös,&nbsp;Gábor Kasza","doi":"10.1140/epja/s10050-025-01625-2","DOIUrl":"10.1140/epja/s10050-025-01625-2","url":null,"abstract":"<div><p>In high energy heavy ion collisions a new state of matter, the strongly coupled quark gluon plasma is formed that exhibits similar properties as the Universe had couple of microseconds after the Big Bang, hence such collisions are usually referred as Little Bangs. Subsequent investigations showed that the created medium is a nearly perfect fluid whose time evolution can be described by hydrodynamic models. The distribution of the hadrons that are created in the freeze-out after a rapid expansion carry information about the final state. On the other hand, with penetrating probes, e.g., with direct photons, one can model the time evolution of the quark gluon plasma. In this paper, we present a hydrodynamic model that was inspired by an analytical solution of the equation of relativistic hydrodynamics. The invariant transverse momentum spectrum and the elliptic flow of direct photons were calculated, the model parameters were obtained by comparison the calculations to LHC ALICE data. Based on the results we give an estimation for the initial temperature of the plasma.</p></div>","PeriodicalId":786,"journal":{"name":"The European Physical Journal A","volume":"61 7","pages":""},"PeriodicalIF":2.8,"publicationDate":"2025-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epja/s10050-025-01625-2.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145164712","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Thermodynamic analysis of transverse momentum spectra in Pb–Pb collisions at 2.76 TeV: centrality dependence of temperature, freezeout parameters and non-extensitivity","authors":"M. Waqas,&nbsp;Hassan Ali Khan,&nbsp;Wolfgang Bietenholz,&nbsp;Muhammad Ajaz,&nbsp;Jihane Ben Slimane,&nbsp;Haifa I. Alrebdi,&nbsp;A. Haj Ismail","doi":"10.1140/epja/s10050-025-01626-1","DOIUrl":"10.1140/epja/s10050-025-01626-1","url":null,"abstract":"<div><p>We study properties of Pb–Pb collisions at 2.76 TeV in mid-rapidity, <span>(|y|&lt;0.5,)</span> based on data by the ALICE Collaboration. In particular, we examine the transverse momentum <span>((p_T))</span> spectra of positively charged (identified) hadrons, <span>(pi ^+,)</span> <span>(K^+)</span> and <i>p</i>,  generated in various centrality intervals. We perform individual fits using the thermodynamically consistent Tsallis distribution to extract the following quantities: the non-extensitivity parameter, <i>q</i>,  the effective temperature, <span>(T_{textrm{eff}},)</span> the kinetic freezeout volume, <i>V</i>,  the mean transverse flow velocity, <span>(beta _T,)</span> the mean kinetic freezeout temperature, <span>(langle T_0rangle ,)</span> the thermal temperature, <span>(T_{textrm{th}},)</span> and the parameter <span>(zeta ,)</span> which characterizes the fluctuating number of generated particles. From peripheral to central collision, and from lower to higher charged particle multiplicity per pseudorapidity unit, <span>(langle dN_{textrm{ch}}/deta rangle ,)</span> all these quantities are observed to increase, with the exception of <i>q</i>,  which has the opposite behavior. The parameters <span>(T_{textrm{eff}},)</span> <i>q</i>,  and <i>V</i> depend on the hadron mass in a way that supports the scenarios of volume differential freezeout and multiple kinetic freezeout. Furthermore, we extracted <span>(langle T_{textrm{eff}}rangle )</span> and <span>(langle qrangle )</span> for different collisions and energies at LHC and RHIC, and compare their dependencies on <span>(langle dN_{textrm{ch}}/deta rangle )</span> and <span>(langle N_{textrm{part}} rangle .)</span></p></div>","PeriodicalId":786,"journal":{"name":"The European Physical Journal A","volume":"61 7","pages":""},"PeriodicalIF":2.8,"publicationDate":"2025-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145163446","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}