The European Physical Journal C最新文献

{"title":"Spectroscopic and structural properties of B, (B_s), and (B_c) mesons within a non-relativistic potential model: a comparative analysis via matrix Numerov and variational methods","authors":"Pritom Kumar Nath,&nbsp;Rishan Dev Choudhury,&nbsp;Jugal Lahkar","doi":"10.1140/epjc/s10052-026-16433-1","DOIUrl":"10.1140/epjc/s10052-026-16433-1","url":null,"abstract":"<div><p>In this work, we studied the spectroscopic masses, decay constants, oscillation frequencies, and Isgur–Wise function parameters of <i>B</i>, <span>(B_s)</span>, and <span>(B_c)</span> mesons within the framework of a non-relativistic potential model. The interaction is modelled using the Killingbeck potential, with calculations performed using two complementary approaches: the matrix Numerov method for solving the Schrödinger equation and the quantum mechanical variational method employing the Gaussian wave function. We determined the unknown parameters of the Killingbeck potential by fitting it to the Cornell potential using the ordinary least squares (OLS) method. These calibrated parameters are then used to compute the aforementioned physical observables. We obtained the masses of the heavy mesons with deviations of less than 0.5% from the highly precise experimental data. We also discussed the drawbacks and limitations of the non-relativistic model and highlighted its domain of applicability. At the end, we compare our results obtained from both methods with those from other theoretical frameworks, including QCD sum rules, lattice QCD, and alternative potential model studies.\u0000</p></div>","PeriodicalId":788,"journal":{"name":"The European Physical Journal C","volume":"86 10","pages":""},"PeriodicalIF":4.9,"publicationDate":"2026-10-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjc/s10052-026-16433-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149133062","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":"Complex phase structure and Widom line for Euler–Heisenberg black holes","authors":"Mozib Bin Awal,&nbsp;Prabwal Phukon","doi":"10.1140/epjc/s10052-026-16405-5","DOIUrl":"10.1140/epjc/s10052-026-16405-5","url":null,"abstract":"<div><p>We investigate the supercritical thermodynamics of Euler–Heisenberg AdS black holes within the framework of Lee–Yang phase transition theory. We show that the system admits two distinct critical points associated with a four-phase thermodynamic structure and identify a degenerate higher-order critical point where the two criticalities merge. Extending the thermodynamic description into the complex domain, we determine the distribution of Lee–Yang singularities and construct the corresponding complex phase diagrams. At the degenerate critical point, we find that a well-defined Widom line emerges despite the absence of a conventional coexistence curve, acting as an effective stability boundary in the supercritical regime. In the two-critical-point regime, the complex phase diagram exhibits two distinct Widom lines, one associated with a coexistence curve and the other arising solely from the complex singularity structure. We further show that the Lee–Yang formalism consistently reproduces the expected phase structure for systems with a single critical point and in the absence of criticality. Our results reveal a rich supercritical phase structure and provide new insights into the origin and physical interpretation of Widom lines.\u0000</p></div>","PeriodicalId":788,"journal":{"name":"The European Physical Journal C","volume":"86 10","pages":""},"PeriodicalIF":4.9,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjc/s10052-026-16405-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149098910","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":"Near-horizon deformation of metric and the black hole instability","authors":"Shi-Jie Ma,&nbsp;Zhan-Feng Mai,&nbsp;Run-Qiu Yang","doi":"10.1140/epjc/s10052-026-16424-2","DOIUrl":"10.1140/epjc/s10052-026-16424-2","url":null,"abstract":"<div><p>Recent time-domain analyses suggest that black hole stability may be sensitive to localized near-horizon geometric deformations, while the underlying spectral mechanism remain unclear. In this work, after verifying the instability of the model in the time domain, we systematically investigate quasi-normal mode spectra under static localized non-positive perturbations within a frequency-domain framework. We find that such deformations generically induce a new purely imaginary mode. As the deformation approaches the horizon, the imaginary part of this mode increases and eventually enters the upper half complex-frequency plane, signaling the onset of black hole instability. Numerical results reveal clear scaling relations between the critical distance for instability and the deformation strength. We further derive rigorous proofs for our discoveries in frequency domain. These results demonstrate that black hole stability under long scale is conditionally sensitive to localized deformation of metric near the horizon and establish a unified spectral framework for understanding their induced instabilities.\u0000</p></div>","PeriodicalId":788,"journal":{"name":"The European Physical Journal C","volume":"86 10","pages":""},"PeriodicalIF":4.9,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjc/s10052-026-16424-2.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149098918","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":"Kaon-induced (phi Sigma ) production off the proton","authors":"Sang-Ho Kim,&nbsp;Myung-Ki Cheoun","doi":"10.1140/epjc/s10052-026-16441-1","DOIUrl":"10.1140/epjc/s10052-026-16441-1","url":null,"abstract":"<div><p>We investigate the reaction mechanism of <span>(K^-p rightarrow phi Sigma ^0)</span> within a hybrid Regge approach based on effective Lagrangians. The nonresonant background includes Reggeized <i>t</i>-channel <i>K</i> and <span>(K^*)</span> exchanges, together with ground-state <span>(Sigma )</span> and nucleon exchanges in the <i>s</i> and <i>u</i> channels, respectively. To describe the structures observed at <span>(3.0 leqslant P_{textrm{Lab}} leqslant 4.5)</span> GeV, we include the high-mass <span>(Sigma (2620))</span> and <span>(Sigma (3000))</span> resonances and examine the spin-parity assignments <span>(J^P = 1/2^pm ,)</span> <span>(3/2^pm ,)</span> and <span>(5/2^pm .)</span> The <span>(K^*)</span>-Reggeon exchange dominates the forward-angle cross sections, whereas the smaller <i>K</i>-Reggeon contribution is important for the total cross section at low energies and for the spin-density matrix elements. The nonresonant background alone is not sufficient to reproduce the local structures in the total cross section or the differential cross sections at large <span>(-t'.)</span> Including the two resonances, particularly the <span>(Sigma (3000),)</span> substantially improves the agreement with the available data. The <span>(J^P=5/2^-)</span> assignment for the <span>(Sigma (3000))</span> provides a reasonable overall description, although the present data do not permit a definitive determination.\u0000</p></div>","PeriodicalId":788,"journal":{"name":"The European Physical Journal C","volume":"86 10","pages":""},"PeriodicalIF":4.9,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjc/s10052-026-16441-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149098746","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":"Unified dark sector and Hubble-tension alleviation in scalar–vector–tensor gravity","authors":"Kimet Jusufi,&nbsp;Amir A. Khodahami,&nbsp;Ahmad Sheykhi,&nbsp;Jackson Levi Said,&nbsp;Emmanuel N. Saridakis","doi":"10.1140/epjc/s10052-026-16406-4","DOIUrl":"10.1140/epjc/s10052-026-16406-4","url":null,"abstract":"<div><p>We investigate a scalar–vector–tensor theory in which matter is minimally coupled to a Jordan-frame metric <span>(tilde{g}_{mu nu }=(1+Xi )g_{mu nu })</span>, while a massive vector sector interacts with the baryonic current. We show that the conformal scalar coupling modifies the physical expansion rate measured by matter observers, leading to an enhancement of the Hubble constant inferred at low redshift. We stress, however, that the Hubble rate is not a conformal invariant, whereas the acoustic angular scale <span>(theta _s)</span> is, and we derive the exact integral condition that the scalar field evolution must satisfy. We show that a single-signed scalar velocity cannot satisfy it, and we construct instead a two-epoch phenomenological evolution which matches <span>(theta _s)</span> exactly while retaining the late-time enhancement, at the cost of a small pre-recombination shift of the effective gravitational coupling. We stress that the scalar is not separately conserved, and that retaining the scalar–matter energy exchange in its continuity equation supplies a further restriction: positivity of the scalar energy density bounds the early component to <span>(z_Elesssim 13)</span>. Notably, the recombination <i>temperature</i> is unmodified, since particle masses are constant in the Jordan frame, only the expansion rate at that epoch being altered. The scalar potential naturally acts as a dynamical dark-energy sector, while the vector sector provides two distinct contributions. The temporal component, determined algebraically by the baryon current, yields an apparent matter-like term in the background expansion that is not a true fluid but rather a manifestation of the interaction energy. The propagating spatial modes, on the other hand, form a vector condensate that behaves as a collisionless pressureless component and can play the cosmological role of cold dark matter. Hence, the framework connects scalar dynamics, effective dark-energy evolution, and the <span>(H_0)</span> tension within a single setup. Finally, local gravitational constraints require a chameleon-type screening mechanism, whose efficiency we discuss critically.\u0000</p></div>","PeriodicalId":788,"journal":{"name":"The European Physical Journal C","volume":"86 10","pages":""},"PeriodicalIF":4.9,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjc/s10052-026-16406-4.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149098917","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":"Cloud screening of extremal charged BTZ black hole","authors":"Mendrit Latifi","doi":"10.1140/epjc/s10052-026-16390-9","DOIUrl":"10.1140/epjc/s10052-026-16390-9","url":null,"abstract":"<div><p>We study the instability of a charged scalar field in the near-horizon region of an extremal charged BTZ black hole. The extremal geometry contains an <span>(textrm{AdS}_2times S^1)</span> throat supported by a constant electric field, which lowers the effective scalar mass and can violate the <span>(textrm{AdS}_2)</span> Breitenlohner–Freedman bound. This identifies an infrared instability of the extremal normal state. We then construct a nearby finite-temperature branch of fully backreacted, source-free, node-free hairy black-hole solutions, thereby establishing the nonlinear continuation of the unstable mode near its onset. The scalar condensate modifies both the Maxwell field and the geometry, while stronger gravitational backreaction lowers the critical temperature and suppresses the condensate amplitude. Near the critical point, the condensate exhibits mean-field scaling. We also develop an effective near-horizon interpretation in terms of electric-flux screening. The exact zero-temperature endpoint of the hairy branch is not determined here and remains an open problem.</p></div>","PeriodicalId":788,"journal":{"name":"The European Physical Journal C","volume":"86 10","pages":""},"PeriodicalIF":4.9,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjc/s10052-026-16390-9.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149098747","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":"Comment on “Einstein–Cartan fermion condensates trapped in double walls induce axial torsion coupling bounds [Eur. Phys. J. C (2026) 86: 785]”","authors":"Luis B. Castro","doi":"10.1140/epjc/s10052-026-16388-3","DOIUrl":"10.1140/epjc/s10052-026-16388-3","url":null,"abstract":"<div><p>We point out several algebraic and dimensional inconsistencies in the derivation of the teleparallel double-wall dynamics and of the axial torsion coupling bound published in this Journal [Eur. Phys. J. C (2026) 86: 785]. Recomputing the torsion two-forms from the tetrads with vanishing spin connection, we obtain expressions that differ from those used in the paper. Consequently, the equations for the wall separation function do not lead to the reported solution, and the approximation <span>(h^2ll z^2)</span> does not restore the polynomial form adopted there. We also show that the proposed wave equation for the wall separation and the corresponding gravitational-wave interpretation require rederivation. In the fermionic sector, the zero-mode solutions and the scalar Dirac bilinear must be distinguished from the positive density <span>(varPsi ^dagger varPsi )</span>. With the corrected solutions, the effective coefficient <span>(A=eB+g_T S)</span> determines a localization length <span>(ell _{textrm{loc}}sim |A|^{-1/2})</span>, so that estimating <span>(g_T)</span> requires specifying an additional physical scale rather than imposing <span>(A=0)</span>. Hence the claimed constant condensate and the bound <span>(g_Tsim 10^{-4})</span> are not established by the calculations presented.\u0000</p></div>","PeriodicalId":788,"journal":{"name":"The European Physical Journal C","volume":"86 10","pages":""},"PeriodicalIF":4.9,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjc/s10052-026-16388-3.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149098913","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":"Right-handed neutrino dark matter consistent with the generation of baryon number asymmetry","authors":"Daijiro Suematsu","doi":"10.1140/epjc/s10052-026-16425-1","DOIUrl":"10.1140/epjc/s10052-026-16425-1","url":null,"abstract":"<div><p>A right-handed neutrino is a promising candidate for dark matter (DM) which has no interaction with nuclei. Since two right-handed neutrinos explain neutrino oscillation data and baryon number asymmetry through both the seesaw mechanism and leptogenesis based on the out-of-equilibrium decay of the lighter one, the lightest third right-handed neutrino could be free from them and stable to be DM. It suggests a possibility that the right-handed neutrinos could be common key particles for the explanation of three problems in the standard model (SM). We study this possibility by analyzing the structure of a neutrino mass matrix in the scotogenic model for neutrino mass. \u0000</p></div>","PeriodicalId":788,"journal":{"name":"The European Physical Journal C","volume":"86 10","pages":""},"PeriodicalIF":4.9,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjc/s10052-026-16425-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149098748","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":"Weak triplet models of neutrino magnetic moments","authors":"Svjetlana Fajfer,&nbsp;Shaikh Saad","doi":"10.1140/epjc/s10052-026-16456-8","DOIUrl":"10.1140/epjc/s10052-026-16456-8","url":null,"abstract":"<div><p>Experimental limits on neutrino magnetic moments remain several orders of magnitude above the predictions of the Standard Model; therefore, any future detection would provide unambiguous evidence for new physics. In models with Dirac neutrinos, however, mechanisms that enhance the magnetic moment typically generate excessively large neutrino masses. Recently, it has been argued that in frameworks where neutrinos mix with weak-triplet Dirac fermions, the magnetic moment can be decoupled from the neutrino mass. In this work, we revisit this possibility and show that sizable enhancements remain highly nontrivial to realize naturally. We demonstrate that, although the minimal realization allows the magnetic moment to be decoupled from the neutrino mass, obtaining an observable enhancement requires a delicate adjustment of the model parameters. Moreover, in extended scenarios, the decoupling no longer persists: the magnetic moment and neutrino mass become intrinsically linked, such that attempts to enhance the former inevitably induce large contributions to the latter.\u0000</p></div>","PeriodicalId":788,"journal":{"name":"The European Physical Journal C","volume":"86 10","pages":""},"PeriodicalIF":4.9,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjc/s10052-026-16456-8.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149098912","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":"Top pair threshold revisited","authors":"Torbjörn Sjöstrand,&nbsp;Valery A. Khoze,&nbsp;Christian T. Preuss","doi":"10.1140/epjc/s10052-026-16444-y","DOIUrl":"10.1140/epjc/s10052-026-16444-y","url":null,"abstract":"<div><p>Recently the CMS and ATLAS Collaborations have found evidence for an unexpectedly large <span>({textrm{t}}{bar{textrm{t}}})</span> cross section in the threshold region, with an excess of the order of 5–10 pb relative to continuum perturbative calculations. A convenient approach to the theoretical study of this region, unifying the above- and below-threshold behaviour, is the non-relativistic Green’s function formalism. It was first applied to top production more than 35 years ago, well before the discovery of the top. We therefore revive and dissect the old formalism, and put it back together in a more consistent form, suited for Monte Carlo event generation. Combined with some practical prescriptions, it can be applied to current conditions. As an example, the below-threshold cross section comes out to be of the order of 6.5 pb, <i>i.e.</i> comparable with the CMS and ATLAS numbers. The new code is publicly available in the <span>Pythia</span> event generator so can be used for more detailed comparisons.\u0000\u0000</p></div>","PeriodicalId":788,"journal":{"name":"The European Physical Journal C","volume":"86 10","pages":""},"PeriodicalIF":4.9,"publicationDate":"2026-10-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epjc/s10052-026-16444-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149098911","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}