We investigate the discovery prospects of a leptophilic gauge boson $ Z_\ell $ at future $ e^+e^- $ colliders, focusing on a comparative study of the Circular Electron–Positron Collider (CEPC) and the International Linear Collider (ILC). Such a state naturally arises from an additional $ U(1)'_\ell $ gauge symmetry, under which quarks remain neutral while all leptons carry a universal charge, motivated by neutrino oscillations and scenarios of physics beyond the Standard Model. As a clean benchmark, we study the process $ e^+e^- \to \mu^+\mu^- $ , including realistic effects of initial-state radiation and beamstrahlung. Our results indicate that the CEPC, with its very high luminosity at $ \sqrt{s}=240 $ GeV, can probe couplings down to $ g_\ell \approx 10^{-3} $ for $ Z_\ell $ masses up to about 220 GeV. The ILC extends the sensitivity to heavier states in the multi-hundred GeV range through its higher $ \sqrt{s} $ stages. These findings demonstrate the strong complementarity of circular and linear colliders in exploring purely leptophilic interactions.

S.O. Kara

Discovery prospects for a leptophilic gauge boson Z$_{ℓ}$ at CEPC and ILC

An analytical and numerical systematic study of the neutrino mass matrix with one texture zero is presented in a basis where the charged leptons are diagonal. Under the assumption that neutrinos are Dirac particles, the analysis is conducted in detail for the normal and inverted hierarchy mass spectra. Our study is performed without any approximations, first analytically and then numerically, using current neutrino oscillation data. The analysis constrains the parameter space in such a way that, among the six possible one-texture-zero patterns, only four are favored in the normal hierarchy and one in the inverted hierarchy by current oscillation data at the $3 \sigma$ level. Phenomenological implications for the lepton CP-violating phase and neutrino masses are also explored.

Colombia

Richard H. Benavides

Yessica Lenis

John D. Gómez

William A. Ponce

One texture zero for Dirac neutrinos in a diagonal charged lepton basis * Richard H. Benavides acknowledges additional financial support from Minciencias (CD82315 CT ICETEX 2021-1080)

Heavy Majorana neutrinos ($\textit{N}$) are predicted in many models of physics beyond the Standard Model. In this work, we explore the production and detection prospects of TeV-scale heavy neutrinos ( $ m_N \gtrsim 1 $ TeV) at a future 3 TeV Compact Linear Collider (CLIC). We focus on two distinct decay topologies: (i) $ N \to \ell^\pm W^\mp $ with hadronic $\textit{W}$ boson decay, leading to a final state with one charged lepton and a hadronic fat jet $ J_W $ ; and (ii) $ N \to \nu h $ with subsequent Higgs decay $ h \to b\bar{b} $ , yielding a Higgs-tagged fat jet $ J_h $ and $\not {E}_T$ . Based on comprehensive detector-level simulations and background analysis, we present both $ 2\sigma $ exclusion limits and $ 5\sigma $ discovery reaches in the $ m_N $ – $ |V_{\ell N}|^2 $ plane. We further extract 95% confidence level upper limits on the mixing parameter $ |V_{\ell N}|^2 $ and perform a detailed comparison with existing constraints from direct searches at future colliders and indirect global fits. Our findings demonstrate that a 3 TeV CLIC can improve the sensitivity to $ |V_{\ell N}|^2 $ by about two orders of magnitude compared with the projected reaches of future hadron colliders while remaining competitive with other CLIC search channels.

China

Yao-Bei Liu

Jing-Wei Lian

Searches for heavy neutrinos at a 3 TeV CLIC in fat jet final states * Yao-Bei Liu is supported by the Natural Science Foundation of Henan Province, China (252300421988), Jing-Wei Lian is supported by the National Natural Science Foundation of China (12447140) and the Natural Science Foundation of Henan Province, China (252300421771)

We study a three-loop induced neutrino mass scenario from a non-holomorphic modular $\textit{A}$ $_{4}$ flavor symmetry and obtain the minimum scenario leading to predictions of the lepton masses, mixing angles, and Dirac and Majorana phases, which are shown through chi square analyses. In addition, we discuss the lepton flavor violations, muon anomalous magnetic moment, lepton universality, and relic density of the dark matter candidate. Moreover, we show that our model can be extended to satisfy the observed relic density of dark matter within the limit of perturbation by adding one singlet scalar boson without changing predictions in the neutrino sector.

Takaaki Nomura

Hiroshi Okada

Neutrino mass model at a three-loop level from a non-holomorphic modular $\textit{A}$ $_{4}$ symmetry * Takaaki Nomura is supported by the Fundamental Research Funds for the Central Universities. Hiroshi Okada is supported by Zhongyuan Talent (Talent Recruitment Series) Foreign Experts Project

We develop a generalized holographic dark energy model based on the Rényi entropy, which introduces a logarithmic deformation of the Bekenstein–Hawking entropy and is characterized by a non-extensivity parameter $$\alpha $$ . By adopting the future event horizon as the infrared cutoff, we formulate the New Rényi Holographic Dark Energy (NRHDE) scenario and derive a modified holographic energy density that reduces smoothly to the standard HDE limit for $$\alpha \rightarrow 0$$ . Starting from the Rényi entropy formalism, we obtain a closed and self-consistent set of evolution equations for the dark energy density parameter $$\Omega _d$$ , the equation-of-state parameter $$w_d$$ , and the deceleration parameter $\textit{q}$. We perform a detailed numerical investigation of the background dynamics over a physically reasonable range of the holographic parameter $\textit{c}$ and the Rényi deformation parameter $$\alpha $$ , and show that the NRHDE model predicts a late-time phantom regime over an extended region of the $$(c,\alpha )$$ parameter space, with a smooth approach toward the cosmological-constant boundary $$w_d=-1$$ as either parameter increases. We further provide a global characterization of the parameter space by means of two-dimensional maps of the present-day equation-of-state parameter and the transition redshift, which clarify the joint impact of $$(c,\alpha )$$ on the late-time cosmological evolution. Finally, a qualitative comparison between the NRHDE background predictions and observational Hubble data from cosmic chronometers is presented as a consistency check of the model at the background level. The NRHDE framework therefore constitutes a minimal and thermodynamically motivated extension of holographic dark energy, offering a flexible platform for future quantitative tests with late-time expansion data.

Iran

Zeinab Tamri

Ali Aghamohammadi

Tayeb Golanbari

Abdolhosein Khodam-Mohammadi

A new Rényi holographic dark energy model and its cosmological implications

<p>We show that a QCD dilaton field, whose vacuum expectation value sets the strong coupling, can render the quantum chromodynamic (QCD) confinement transition first order. The QCD dilaton is cosmologically attracted to a false vacuum at weak coupling in the early Universe. Quantum tunneling toward the true vacuum triggers prompt chiral symmetry breaking and confinement of QCD, leading to detonating bubbles of the hadronic phase. We find that plasma sound waves produced by this dilaton-induced, first-order QCD phase transition generate a stochastic gravitational wave signal strikingly similar to the recently detected gravitational wave background from pulsar timing arrays. We briefly comment on how this theory can be probed through collider experiments and cosmology.</p>

Sweden

Aleksandr Chatrchyan

M.C. David Marsh

Charalampos Nikolis

Gravitational Waves from a Dilaton-Induced, First-Order QCD Phase Transition

<p>The pion light-cone distribution amplitude (LCDA) is an essential nonperturbative input for a range of high-energy exclusive processes in quantum chromodynamics. Building on our previous work, the continuum limit of the fourth Mellin moment of the pion LCDA is determined in quenched QCD using quark masses which correspond to a pion mass of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>m</mi><mi>π</mi></msub><mo>=</mo><mn>550</mn><mtext> </mtext><mtext> </mtext><mi>MeV</mi></math>. This calculation finds <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mo stretchy="false">⟨</mo><msup><mrow><mi>ξ</mi></mrow><mrow><mn>2</mn></mrow></msup><mo stretchy="false">⟩</mo><mo>=</mo><mn>0.202</mn><mo stretchy="false">(</mo><mn>8</mn><mo stretchy="false">)</mo><mo stretchy="false">(</mo><mn>9</mn><mo stretchy="false">)</mo></mrow></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mo stretchy="false">⟨</mo><msup><mrow><mi>ξ</mi></mrow><mrow><mn>4</mn></mrow></msup><mo stretchy="false">⟩</mo><mo>=</mo><mn>0.039</mn><mo stretchy="false">(</mo><mn>28</mn><mo stretchy="false">)</mo><mo stretchy="false">(</mo><mn>11</mn><mo stretchy="false">)</mo></mrow></math> where the first error indicates the combined statistical and systematic uncertainty from the analysis and the second indicates the uncertainty from working with Wilson coefficients computed to next-to-leading order. These results are presented in the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mover accent="true"><mrow><mi>MS</mi></mrow><mo stretchy="true">¯</mo></mover></math> scheme at a renormalization scale of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>μ</mi><mo>=</mo><mn>2</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></mrow></math>.</p>

United States

William Detmold

Anthony V. Grebe

Japan

Issaku Kanamori

Taiwan

C.J. David Lin

Robert J. Perry

Yong Zhao

Parton physics from a heavy-quark operator product expansion: Lattice QCD calculation of the fourth moment of the pion distribution amplitude

This paper investigates the shadow and quasinormal modes (QNMs) of a Schwarzschild black hole (BH) embedded in a Hernquist dark matter (DM) halo, focusing on the influence of DM parameters – specifically the core radius $$r_{s}$$ and core density $$\rho _{s}$$ – on BH observational signatures. We analyze the structure of the BH shadow, lensing ring, and photon ring, showing that the shadow radius increases with both $$r_{s}$$ and $$\rho _{s}$$ . Using the WKB approximation, Padé approximants, and time-domain integration, we compute the QNMs for scalar, electromagnetic, and axial gravitational perturbations. Our results reveal that the DM halo modifies the spacetime’s effective potential: larger values of $$r_{s}$$ or $$\rho _{s}$$ reduce the peak of the potential barrier, leading to lower oscillation frequencies and slower wavefunction damping. These findings highlight the systematic impact of DM on strong-field observables and suggest that BH shadows and QNMs provide a viable means to probe DM profiles in galactic nuclei.

Shitao Qi

Ziqiang Cai

Shadows and quasinormal modes of a Schwarzschild black hole immersed in Hernquist dark matter halo

Inflationary production of massive dark photons with non-minimal couplings to gravity shows surprising growth at large momenta. These couplings appear in the effective low energy description of a more fundamental theory. We find that the growth is absent in explicit gauge invariant UV-complete models. Such completions are also free of “ghost” instabilities, which often appear in the effective models.

Finland

Oleg Lebedev

South Korea

Jong-Hyun Yoon

Taming the dark photon production via a non-minimal coupling to gravity

We study the superradiant stability of magnetized Reissner–Nordström black holes against charged, massive scalar perturbations at linear order in the magnetization parameter <italic>b</italic>. At this order the Klein&#8211;Gordon equation is separable and the horizon acquires a magnetically induced angular velocity <math altimg='si1.svg'><mrow><msub><mstyle mathvariant='normal'><mi>&#937;</mi></mstyle><mi>H</mi></msub><mo linebreak='goodbreak'>=</mo><mn>4</mn><mi>b</mi><mi>Q</mi><mo linebreak='goodbreak'>/</mo><msub><mi>r</mi><mo>+</mo></msub></mrow></math>, enlarging the superradiant band to <math altimg='si2.svg'><mrow><mi>&#969;</mi><mo linebreak='goodbreak'>&lt;</mo><mi>m</mi><msub><mstyle mathvariant='normal'><mi>&#937;</mi></mstyle><mi>H</mi></msub><mo linebreak='goodbreak'>+</mo><mi>q</mi><msub><mstyle mathvariant='normal'><mi>&#934;</mi></mstyle><mi>H</mi></msub></mrow></math>. Despite this enhancement, a sign analysis of the quartic governing the extrema of the effective potential&#8211;validated by numerical scans&#8211;shows that no exterior barrier&#8211;well forms, including in the eikonal scaling ( <italic>m</italic>, &#8467;&#8239;&#8594;&#8239;&#8734; with <math altimg='si3.svg'><mrow><mi>m</mi><mi>b</mi><mo linebreak='goodbreak'>=</mo><mi mathvariant='script'>O</mi><mo>(</mo><mn>1</mn><mo>)</mo></mrow></math>). Without a trapping well, quasi-bound superradiant modes do not arise, and the black-hole bomb is therefore absent. We conclude that Hod&#8217;s no-bomb theorem remains robust for weakly magnetized, non-rotating black holes at <math altimg='si4.svg'><mrow><mi mathvariant='script'>O</mi><mo>(</mo><mi>b</mi><mo>)</mo></mrow></math>.

Indonesia

Haryanto M. Siahaan

No-bomb theorem for weakly magnetized Reissner-Nordström black holes: A linear-order analysis