A model for the nuclear medium modification of parton densities is presented. The approach is based on a global analysis of available deep inelastic scattering data for different nuclear targets within the rescaling model, combined with the effects of Fermi motion. The scale dependence is implemented through the DGLAP-evolved quark and gluon densities in a proton derived analytically at the leading order of QCD coupling. By fitting the rescaling parameters to experimental data on the ratio $F_2^A(x,Q^2)/F_2^{A^\prime}(x,Q^2) $ for several nuclear targets $\textit{A}$ and $\textit{A}$', we obtain predictions for nuclear parton distributions, even for unmeasured nuclei. The effects of nuclear modifications are investigated with respect to the mass number $\textit{A}$. We highlight distinct shadowing and antishadowing behaviors for gluons and quarks.

Russia

A.V. Kotikov

A.V. Lipatov

A simple model for nuclear modification of parton distribution functions * This research has been carried out at the expense of the Russian Science Foundation grant 25-22-00066, https://rscf.ru/en/project/25-22-00066/

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)

In high-energy proton-proton (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>p</mi><mi>p</mi></math>) collisions at the LHC, nonprompt charm hadrons, originating from beauty hadron decays, provide a valuable probe for beauty quark dynamics, particularly at low transverse momentum where direct beauty measurements are challenging. We employ a multiphase transport (AMPT) model of string melting version coupled with pythia8 initial conditions to study the beauty hadron and nonprompt charm hadron productions in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>p</mi><mi>p</mi></math> collisions at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>13</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></math>. In this work, the beauty quark mass during the generation stage has been increased to reproduce the measured <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>b</mi><mover accent="true"><mi>b</mi><mo stretchy="false">¯</mo></mover></math> cross section, and a beauty flavor-specific coalescence parameter <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msubsup><mrow><mi>r</mi></mrow><mrow><mi>B</mi><mi>M</mi></mrow><mrow><mi>b</mi></mrow></msubsup></mrow></math> is introduced to match LHCb measurements of beauty baryon-to-meson ratios. With these refinements, the AMPT model achieves a reasonable agreement with experimental data on beauty hadron yields and nonprompt charm hadron production from ALICE and LHCb. We present the transverse momentum and multiplicity dependence of nonprompt-to-prompt charm hadron ratios, providing new insights into the interplay between beauty quark production and the hadronization process. We emphasize that the multiplicity dependence of the nonprompt to prompt charm hadron productions can be useful to constrain the flavor dependences of the coalescence dynamics. This work establishes a unified framework for future studies of heavy quark transport and collective flow behavior in small collision systems.

Jialin He

Xinye Peng

Xiaoming Zhang

Liang Zheng

Studies of beauty hadron and nonprompt charm hadron production in pp collisions at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msqrt><mrow><mi>s</mi></mrow></msqrt><mo>=</mo><mn>13</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></mrow></math> within a transport model approach

We examine the Hawking radiation sparsity and quasinormal mode (QNM) spectra of a Schwarzschild black hole surrounded by the King dark matter distribution. The modified metric, derived from the King density profile, yields altered expressions for the lapse function, mass, and Hawking temperature. The presence of dark matter reduces the Hawking temperature, indicating suppressed thermal emission. Analysis of radiation sparsity reveals its dependence on the horizon radius, with larger scale radius $\textit{R}$ and central density $$\rho _0$$ enhancing sparsity compared to the constant value in the Schwarzschild case. The photon sphere and shadow radius increase with $\textit{R}$ and $$\rho _0$$ , suggesting enlarged black hole shadows under dark matter influence. Hawking emission rates exhibit a downward shift in both peak intensity and frequency. The QNM spectra, obtained via the Mashhoon and 3rd-order Wentzel–Kramers–Brillouin (WKB) methods, show that both the oscillation frequencies and damping or decay rate decrease with the dark matter parameter $$\alpha = 8\pi \rho _0 R^2$$ . This study also examines how King dark matter halo affects periodic particle motion around a black hole, showing that it alters orbital stability and enhances precession, leading to transitions from bound to unbound motion. These results collectively demonstrate that King dark matter substantially modifies the thermodynamic and dynamical properties of black holes, offering potential observational imprints in black hole shadow and gravitational wave studies.

Azerbaijan

Czechia

Hassan Hassanabadi

Jing Zhang

India

Dhruba Gogoi

Farokhnaz Hosseinifar

Finland

Soroush Zare

Periodic orbits and quasinormal modes of a black hole surrounded by King dark matter halo

We present updates within the MSHT global PDF fit that focus on the high $\textit{x}$ region, and on improving our understanding of the interplay of various theoretical contributions and experimental constraints here. We revisit the question of target mass and higher twist corrections, considering their impact for the first time at approximate $$\hbox {N}^3$$ LO order in a global PDF analysis. Their inclusion is found to be moderate but not negligible on both the PDFs and preferred value of the strong coupling. Increased stability in these at $$\hbox {aN}^3$$ LO is observed in comparison to lower orders. We also study the impact of an updated treatment of various fixed-target DIS data, the inclusion of SeaQuest fixed-target Drell Yan data, and new ZEUS data that extends coverage into the high $\textit{x}$ region. The SeaQuest data have the largest effect of these, in particular on the light quark separation at high $\textit{x}$, while the impact of the other updates is rather mild.

United Kingdom

L. Harland-Lang

Belgium

T. Cridge

M. Reader

R. Thorne

A reassessment of the role of high $\textit{x}$ data on the MSHT global PDF fit

In this work, we compute the one-loop four-graviton amplitudes with a massive abelian vector field (Proca) circulating in the loop. Instead of the conventional Einstein-Hilbert formulation, we employ the Landau-Lifshitz metric density approach, coupling gravity to the Proca field. Within this framework, we found that the resulting contact-terms-free $\textit{n}$-gon numerators exhibit a manifest double-copy structure, provided the external gravitational trees satisfy this property. This structure enables the direct construction of the corresponding amplitudes with a scalar in the loop. We further show that these numerators can be consistently used to evaluate pure gravity amplitudes in the sectors where contact terms vanish, offering a simplified setting to explore double-copy relations at one loop level.

Cristhiam Lopez-Arcos

One-loop double copy from gravity coupled to a massive vector field

We extend the applicability of achilles (A CHIcagoLand Lepton Event Simulator) by incorporating the single pion production mechanism in a fully exclusive fashion. The electroweak interaction vertex is modeled by combining the state-of-the-art dynamical coupled-channels approach with realistic hole spectral functions, which account for correlations in both the initial target state and the residual spectator system. Final-state interactions are treated using a semiclassical intranuclear cascade that leverages nuclear configurations to determine the correlated spatial distribution of protons and neutrons. The meson-baryon scattering amplitudes used in the cascade are computed within the dynamical coupled-channels framework, consistent with the electroweak vertex. To model pion absorption, we employ the optical potential approach of Oset and Salcedo [<a href="http://dx.doi.org/10.1016/0375-9474(88)90310-7">Nucl. Phys. A484, 557 (1988)</a>.]. As an alternative approach, we explicitly model the production and propagation of resonances which mediate pion-nucleon scattering and pion absorption. We validate our approach against pion-nucleon and pion-nucleus scattering data, and present comparisons with electron- and neutrino-nucleus measurements from <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="normal">e</mi><mn>4</mn><mi>ν</mi></mrow></math>, T2K, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>MINER</mi><mi>ν</mi><mi mathvariant="normal">A</mi></math>, and MicroBooNE.

United States

Joshua Isaacson

William Jay

Italy

Alessandro Lovato

Pedro Machado

Alexis Nikolakopoulos

Noemi Rocco

Noah Steinberg

Single pion production and pion propagation in achilles

We investigate Krylov state complexity as a probe of the quantum Mpemba effect in quantum spin chains. For models without global <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>U</mi><mo stretchy="false">(</mo><mn>1</mn><mo stretchy="false">)</mo></math> symmetry, Krylov complexity exhibits clear Mpemba-like crossings, consistent with conventional diagnostics such as the trace distance, while offering a complementary interpretation in terms of Hilbert-space exploration and dynamical delocalization. In <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>U</mi><mo stretchy="false">(</mo><mn>1</mn><mo stretchy="false">)</mo></math>-symmetric systems, we confirm that the recently proposed symmetric component of Krylov complexity serves as a robust and reliable indicator of the quantum Mpemba effect, capturing anomalous relaxation even in cases where the total complexity fails to do so.

Iran

Mohsen Alishahiha

Mohammad Javad Vasli

Krylov complexity as a probe of the quantum Mpemba effect