The European Physical Journal C最新文献

{"title":"Flavour-dependent chemical freeze-out of light nuclei in relativistic heavy-ion collisions","authors":"Rishabh Sharma,&nbsp;Fernando Antonio Flor,&nbsp;Sibaram Behera,&nbsp;Chitrasen Jena,&nbsp;Helen Caines","doi":"10.1140/epjc/s10052-025-14800-y","DOIUrl":"10.1140/epjc/s10052-025-14800-y","url":null,"abstract":"<div><p>We study the production of light nuclei in Au+Au collisions at <span>(sqrt{s_textrm{NN}})</span> = 7.7–200 GeV and Pb+Pb collisions at <span>(sqrt{s_textrm{NN}})</span> = 2.76 and 5.02 TeV within a flavour-dependent chemical freeze-out scenario, assuming different flavoured hadrons undergo separate chemical freeze-out. Using the <span>Thermal-FIST</span> package, thermal parameters extracted from fits to various sets of hadron yields, including and excluding light nuclei, are used to calculate the ratios of the yields of light nuclei, namely, <i>d</i>/<i>p</i>, <span>(bar{d}/bar{p})</span>, <i>t</i>/<i>p</i>, <i>t</i>/<i>d</i>, <span>(^4text {He}/^3text {He})</span>, and <span>(^3text {H}_{varLambda }/^3text {He})</span>. A comparison with experimental data from the STAR and ALICE collaborations shows that a sequential freeze-out scenario provides a better description of light nuclei yield ratios than the traditional single freeze-out approach. These results suggest the flavour-dependent chemical freeze-out for final state light nuclei production persists in heavy-ion collisions at both RHIC and LHC energies.\u0000</p></div>","PeriodicalId":788,"journal":{"name":"The European Physical Journal C","volume":"85 9","pages":""},"PeriodicalIF":4.8,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjc/s10052-025-14800-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145210968","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Universal pattern in fermion mass ratios and implications for flavor models","authors":"Samir Varma","doi":"10.1140/epjc/s10052-025-14771-0","DOIUrl":"10.1140/epjc/s10052-025-14771-0","url":null,"abstract":"<div><p>We show that a single analytic expression using only the labels that distinguish Standard Model mass eigenstates—the ordering index <span>(din {1,2,3})</span> and electric charge <span>(q)</span>—fits all fermion mass ratios with high precision and stable <span>(mathcal {O}(1))</span> parameters. The functional form <span>(ln (m_1/m_2)= d_1^{zeta _1} d_2^{zeta _2} kappa ^{[(d_1 |q_1|)^{gamma (mu )}-(d_2 |q_2|)^{gamma (mu )}]})</span> reproduces all 30 independent quark ratios from <span>(M_Z)</span> to <span>(10^{12},text {GeV})</span> with <span>(chi ^2/textrm{dof}lesssim 10^{-6})</span> using per-scale fits (24 parameters), fixed-<span>(kappa )</span> fits (18), or global fits (5–6). Parameters remain near <span>(kappa simeq 2.3)</span>, <span>(zeta _1simeq 1.16)</span>, <span>(zeta _2simeq -0.8)</span>, <span>(gamma simeq 1.1)</span>. Three orthogonal checks establish specificity and robustness: (i) a 120-permutation test where only the physical mapping of ratios to <span>((d,|q|))</span> fits; (ii) a 720-basis scan in which the adjacent-ratio basis is uniquely preferred by AIC/BIC and many alternatives fail to converge; (iii) alternative functional forms are decisively disfavored by AIC/BIC. The same form, with natural parameters, describes charged-lepton and neutrino ratios; for <span>(q=0)</span> the charge term vanishes, leaving pure <span>(d^{zeta })</span> scaling. We sketch three minimal mechanisms—modified Froggatt–Nielsen, partial compositeness, and a Randall–Sundrum overlap—that generate the additive <span>(d)</span>–<span>(|q|)</span> dependence at the exponent level and reduce to the neutrino limit. The pattern predicts percent-level deviations from standard running near <span>(10^{14},text {GeV})</span> and, with <span>(text {meV})</span>-scale anchors, <span>(varSigma m_nu simeq 0.06,text {eV})</span>. To our knowledge, no previous empirical relation achieves simultaneous cross-sector consistency with such parameter stability; the result offers a compact target for flavor model building.</p></div>","PeriodicalId":788,"journal":{"name":"The European Physical Journal C","volume":"85 9","pages":""},"PeriodicalIF":4.8,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjc/s10052-025-14771-0.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145211033","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"The (Lambda _c^+rightarrow Lambda pi ^+pi ^+pi ^-) reaction, and a triangle singularity producing the (Sigma ^*(1430)) state","authors":"Yi-Yao Li,&nbsp;Jing Song,&nbsp;Eulogio Oset,&nbsp;Wei-Hong Liang,&nbsp;Raquel Molina","doi":"10.1140/epjc/s10052-025-14820-8","DOIUrl":"10.1140/epjc/s10052-025-14820-8","url":null,"abstract":"<div><p>We study the decay <span>(Lambda _c^+ rightarrow Lambda pi ^+ pi ^+ pi ^-)</span>, focusing on the production of the <span>(Sigma ^*(1430))</span> resonance observed by the Belle Collaboration. Interpreted as a dynamically generated state from meson-baryon interactions in the chiral unitary approach, the <span>(Sigma ^*(1430))</span> signal is shown to be enhanced by a triangle singularity involving intermediate <span>(K^{*-})</span>, <i>p</i>, and <span>({bar{K}}^0)</span> states. This mechanism leads to a sharp peak near 1434 MeV in the <span>(pi ^+ Lambda )</span> invariant mass distribution, in agreement with the experimental observations, and predicts a secondary peak around 1875 MeV in the <span>(pi ^- Sigma ^*(1430))</span> spectrum tied to the triangle singularity. We also estimate the branching ratio of <span>(Lambda _c^+ rightarrow pi ^+ pi ^- Sigma ^*(1430))</span> to be about <span>(3.5 times 10^{-4})</span>. The results for the branching ratio and the <span>(pi ^- Sigma ^*(1430))</span> mass distributions are predictions of the theoretical approach, which could be tested with reanalysis of existing data.\u0000</p></div>","PeriodicalId":788,"journal":{"name":"The European Physical Journal C","volume":"85 9","pages":""},"PeriodicalIF":4.8,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjc/s10052-025-14820-8.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145211035","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Simulation of the background from (^{13})C((alpha ,,n)^{16})O reaction in the JUNO scintillator","authors":"JUNO Collaboration","doi":"10.1140/epjc/s10052-025-14333-4","DOIUrl":"10.1140/epjc/s10052-025-14333-4","url":null,"abstract":"<div><p>Large-scale organic liquid scintillator detectors are highly efficient in the detection of MeV-scale electron antineutrinos. These signal events can be detected through inverse beta decay on protons, which produce a positron accompanied by a neutron. A noteworthy background for antineutrinos coming from nuclear power reactors and from the depths of the Earth (geoneutrinos) is generated by (<span>(alpha ,,n)</span>) reactions. In organic liquid scintillator detectors, <span>(alpha )</span> particles emitted from intrinsic contaminants such as <span>(^{238})</span>U, <span>(^{232})</span>Th, and <span>(^{210})</span>Pb/<span>(^{210})</span>Po, can be captured on <span>(^{13})</span>C nuclei, followed by the emission of a MeV-scale neutron. Three distinct interaction mechanisms can produce prompt energy depositions preceding the delayed neutron capture, leading to a pair of events correlated in space and time within the detector. Thus, (<span>(alpha ,,n)</span>) reactions represent an indistinguishable background in liquid scintillator-based antineutrino detectors, where their expected rate and energy spectrum are typically evaluated via Monte Carlo simulations. This work presents results from the open-source SaG4n software, used to calculate the expected energy depositions from the neutron and any associated de-excitation products. Also simulated is a detailed detector response to these interactions, using a dedicated Geant4-based simulation software from the JUNO experiment. An expected measurable <span>(^{13})</span>C<span>((alpha ,,n)^{16})</span>O event rate and reconstructed prompt energy spectrum with associated uncertainties, are presented in the context of JUNO, however, the methods and results are applicable and relevant to other organic liquid scintillator neutrino detectors.\u0000\u0000</p></div>","PeriodicalId":788,"journal":{"name":"The European Physical Journal C","volume":"85 9","pages":""},"PeriodicalIF":4.8,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjc/s10052-025-14333-4.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145210939","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Evolution of superhorizon perturbations in early Universe with anisotropic solid remnant","authors":"Peter Mészáros,&nbsp;Daniel Račko","doi":"10.1140/epjc/s10052-025-14738-1","DOIUrl":"10.1140/epjc/s10052-025-14738-1","url":null,"abstract":"<div><p>We study effects of presence of a small amount of so-called anisotropic solid remnant in the early post-inflationary Universe dominated by radiation. This model is inspired by solid inflation and its generalizations with matter described through a triplet of fields. In our model, the internal full global Euclidean symmetry of this triplet is broken, which leads to an anisotropic expansion of the Universe. Superhorizon scalar and vector perturbations grow, while behavior of tensor perturbations remains the same as in the standard case with Universe filled with only radiation. We also find a very interesting case within the limit of a very small amount of the anisotropic solid remnant and the longest possible duration of its presence, where size of vector perturbations decreases with a different power of scale factor as in the standard scenario. The obtained results improve agreement between the observational data and the theoretical predictions of solid inflation in a case with suppressed non-linear effects.\u0000</p></div>","PeriodicalId":788,"journal":{"name":"The European Physical Journal C","volume":"85 9","pages":""},"PeriodicalIF":4.8,"publicationDate":"2025-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjc/s10052-025-14738-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145211032","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Long-lived quasinormal modes and echoes in the Einstein–Gauss–Bonnet–Proca theory","authors":"B. C. Lütfüoğlu","doi":"10.1140/epjc/s10052-025-14839-x","DOIUrl":"10.1140/epjc/s10052-025-14839-x","url":null,"abstract":"<div><p>We study quasinormal modes and time-domain profiles of a massive scalar field in the background of black holes arising in Einstein–Gauss–Bonnet–Proca gravity. The black holes in this theory possess <i>primary Proca hair</i>, which modifies the effective potential and gives rise to distinctive dynamical phenomena. Using three complementary numerical techniques – the WKB method with Padé resummation, time-domain integration, and the Frobenius (Leaver) method – we obtain accurate spectra of quasinormal frequencies. Our analysis shows that increasing the scalar-field mass leads to arbitrarily long-lived states, known as quasi-resonances, a behavior shared by both the fundamental mode and the first overtone. The real part of the quasinormal mode decreases for the first and higher overtones and starting from the second overtone it reaches zero at some critical value of mass of the field. When the effective potential develops an additional peak, the late-time signal exhibits a sequence of echoes. Furthermore, the time-domain evolution reveals distinct regimes of intermediate power-law tails <span>(sim t^{-4/3-ell }sin (A(mu )t))</span> and a universal asymptotic tails <span>(sim t^{-5/6}sin (mu t))</span>.\u0000</p></div>","PeriodicalId":788,"journal":{"name":"The European Physical Journal C","volume":"85 9","pages":""},"PeriodicalIF":4.8,"publicationDate":"2025-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjc/s10052-025-14839-x.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145210297","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Polarized equatorial emission and hot spots around black holes with a dark matter halo","authors":"Tsanimir Angelov,&nbsp;Rasim Bekir,&nbsp;Galin Gyulchev,&nbsp;Petya Nedkova,&nbsp;Stoytcho Yazadjiev","doi":"10.1140/epjc/s10052-025-14537-8","DOIUrl":"10.1140/epjc/s10052-025-14537-8","url":null,"abstract":"<div><p>We study linear polarization of the accretion disks around black holes with a dark matter halo. The interaction of the black hole with the dark matter is modeled by considering an exact solution to the Einstein equations which describe a superposition of the Schwarzschild black hole with a Hernquist-type matter distribution. We simulate the observable polarization of a magnetized fluid ring orbiting around the black hole and evaluate the influence of the dark matter halo on its properties for physical parameters compatible with the dark matter distribution in galaxies. The polarization intensity and direction of the direct images deviate less than <span>(1%)</span> from the isolated Schwarzschild black hole for a range of magnetic field configurations. For indirect images the deviation increases by an order of magnitude but still remains under <span>(10%)</span> for small inclination angles corresponding to the galactic targets M87* and SgrA*. This makes detection of the dark matter impact on the polarized emissions from accretion disks extremely challenging in the near future.\u0000</p></div>","PeriodicalId":788,"journal":{"name":"The European Physical Journal C","volume":"85 9","pages":""},"PeriodicalIF":4.8,"publicationDate":"2025-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjc/s10052-025-14537-8.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145210302","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Robust resonant anomaly detection with NPLM","authors":"Gaia Grosso,&nbsp;Debajyoti Sengupta,&nbsp;Tobias Golling,&nbsp;Philip Harris","doi":"10.1140/epjc/s10052-025-14759-w","DOIUrl":"10.1140/epjc/s10052-025-14759-w","url":null,"abstract":"<div><p>In this study, we investigate the application of the New Physics Learning Machine (NPLM) algorithm as an alternative to the standard CWoLa method with Boosted Decision Trees (BDTs), particularly for scenarios with rare signal events. NPLM offers an end-to-end approach to anomaly detection and hypothesis testing by utilizing an in-sample evaluation of a binary classifier to estimate a log-density ratio, which can improve detection performance without prior assumptions on the signal model. We examine two approaches: (1) a end-to-end NPLM application in cases with reliable background modelling and (2) an NPLM-based classifier used for signal selection when accurate background modelling is unavailable, with subsequent performance enhancement through a hyper-test on multiple values of the selection threshold. Our findings show that NPLM-based methods outperform BDT-based approaches in detection performance, particularly in low signal injection scenarios, while significantly reducing epistemic variance due to hyperparameter choices. This work highlights the potential of NPLM for robust resonant anomaly detection in particle physics, setting a foundation for future methods that enhance sensitivity and consistency under signal variability.\u0000</p></div>","PeriodicalId":788,"journal":{"name":"The European Physical Journal C","volume":"85 9","pages":""},"PeriodicalIF":4.8,"publicationDate":"2025-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12477090/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145197475","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"The generalized second law for fermionic and bosonic fields","authors":"Koray Düztaş","doi":"10.1140/epjc/s10052-025-14823-5","DOIUrl":"10.1140/epjc/s10052-025-14823-5","url":null,"abstract":"<div><p>We evaluate the validity of the generalized second law for Kerr black holes perturbed by fermionic and bosonic fields. We derive that the critical frequency for a test field below which the area of a Kerr black hole would decrease, coincides with the superradiance limit which pertains to bosonic fields. The fact that the absorption of fermionic fields with arbitrarily low frequencies is allowed, leads to a generic violation of the generalized second law as both the black hole and the environment lose entropy. The result does not contradict the proof of the area theorem which pre-assumes the validity of the null energy condition. We also construct a thought experiment involving bosonic fields to check whether the minimum increase in the area can compensate for the decrease in the entropy of the environment. We minimize the entropy increase by considering a black hole at the extremal limit, perturbed by a bosonic field at the superradiance limit. We show that the generalized second law remains valid for bosonic fields that satisfy the null energy condition. The result does not require the employment of entropy bounds when one assigns von Neumann entropy to test fields.\u0000</p></div>","PeriodicalId":788,"journal":{"name":"The European Physical Journal C","volume":"85 9","pages":""},"PeriodicalIF":4.8,"publicationDate":"2025-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjc/s10052-025-14823-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145210643","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Hawking–Rényi thermodynamics of rotating black holes from locally Kiselev-type behavior","authors":"Viktor G. Czinner,&nbsp;Hideo Iguchi","doi":"10.1140/epjc/s10052-025-14756-z","DOIUrl":"10.1140/epjc/s10052-025-14756-z","url":null,"abstract":"<div><p>The Hawking–Rényi model requires the Rényi entropy thermodynamic temperature of a black hole to be identical with the surface gravity defined-, Hawking temperature. We investigate this approach for stationary black hole space-times, and show that a locally Kiselev-type behavior around the horizon with a coupled anisotropic fluid is sufficient to provide a solution to the problem. In addition, due to the rotating motion, an extra shift has also to be present in the effective mass of the black hole, which is determined by the rotation parameter, <i>a</i>, and the Rényi parameter, <span>(lambda )</span>. We consider space-times with and without electric charge, and show that the functional form of the solution is the same for both cases. A full thermodynamic analysis of the model falls beyond the scope of this Letter, the main achievements are the derivation and interpretation of the solution.\u0000</p></div>","PeriodicalId":788,"journal":{"name":"The European Physical Journal C","volume":"85 9","pages":""},"PeriodicalIF":4.8,"publicationDate":"2025-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjc/s10052-025-14756-z.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145171048","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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}