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)

We construct a linear <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>S</mi><mi>U</mi><mo stretchy="false">(</mo><mn>3</mn><msub><mo stretchy="false">)</mo><mi>L</mi></msub><mo>×</mo><mi>S</mi><mi>U</mi><mo stretchy="false">(</mo><mn>3</mn><msub><mo stretchy="false">)</mo><mi>R</mi></msub></math> parity doublet model for octet baryons. Our model employs the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo stretchy="false">(</mo><mn>3</mn><mo>,</mo><mover accent="true"><mn>3</mn><mo stretchy="false">¯</mo></mover><mo stretchy="false">)</mo><mo>+</mo><mo stretchy="false">(</mo><mover accent="true"><mn>3</mn><mo stretchy="false">¯</mo></mover><mo>,</mo><mn>3</mn><mo stretchy="false">)</mo></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo stretchy="false">(</mo><mn>3</mn><mo>,</mo><mn>6</mn><mo stretchy="false">)</mo><mo>+</mo><mo stretchy="false">(</mo><mn>6</mn><mo>,</mo><mn>3</mn><mo stretchy="false">)</mo></math> chiral representations while excluding the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo stretchy="false">(</mo><mn>8</mn><mo>,</mo><mn>1</mn><mo stretchy="false">)</mo><mo>+</mo><mo stretchy="false">(</mo><mn>1</mn><mo>,</mo><mn>8</mn><mo stretchy="false">)</mo></math> representation. Through systematic analysis, we demonstrate that the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo stretchy="false">(</mo><mn>3</mn><mo>,</mo><mn>6</mn><mo stretchy="false">)</mo><mo>+</mo><mo stretchy="false">(</mo><mn>6</mn><mo>,</mo><mn>3</mn><mo stretchy="false">)</mo></math> representation containing symmetric “bad” diquarks, despite being energetically disfavored, is essential for reproducing the correct baryon mass hierarchy—particularly the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Σ</mi><mtext>−</mtext><mi mathvariant="normal">Ξ</mi></math> mass ordering. The model incorporates both spontaneous and explicit chiral symmetry breaking, with the latter implemented through bare quark mass terms that properly account for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>S</mi><mi>U</mi><mo stretchy="false">(</mo><mn>3</mn><mo stretchy="false">)</mo></math> flavor breaking effects. Our numerical analysis successfully reproduces the ground-state octet baryon masses and predicts the spectrum of excited states up to 2.5 GeV. For the experimentally challenging <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Ξ</mi></math> sector, we identify <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Ξ</mi><mo stretchy="false">(</mo><mn>1950</mn><mo stretchy="false">)</mo></math> as the first positive-parity excitation. The analysis reveals that ground states are dominated by the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo stretchy="false">(</mo><mn>3</mn><mo>,</mo><mover accent="true"><mn>3</mn><mo stretchy="false">¯</mo></mover><mo stretchy="false">)</mo><mo>+</mo><mo stretchy="false">(</mo><mover accent="true"><mn>3</mn><mo stretchy="false">¯</mo></mover><mo>,</mo><mn>3</mn><mo stretchy="false">)</mo></math> representation, consistent with the preference for “good” diquark configurations, while the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo stretchy="false">(</mo><mn>3</mn><mo>,</mo><mn>6</mn><mo stretchy="false">)</mo><mo>+</mo><mo stretchy="false">(</mo><mn>6</mn><mo>,</mo><mn>3</mn><mo stretchy="false">)</mo></math> contribution remains crucial for the mass spectrum.

Japan

Bikai Gao

Atsushi Hosaka

Linear realization of an SU(3) parity doublet model for octet baryons with a bad diquark

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

Multivariate analysis (MVA) is employed to probe the dark matter candidate A′, a gauge boson of a model rooted within Einstein-Cartan Theory, at the International Linear Collider (ILC). <monospace>WHIZARD</monospace> package is used as the event generator to simulate electron-positron interactions at the ILC, at a 500&#8239;GeV center-of-mass energy ( <math altimg='si11.svg'><msqrt><mi>s</mi></msqrt></math>) and a 500 fb <math altimg='si10.svg'><msup><mrow /><mrow><mo>&#8722;</mo><mn>1</mn></mrow></msup></math> detector&#8217;s integrated luminosity ( <math altimg='si31.svg'><mi mathvariant='script'>L</mi></math>), to produce the A&#8242; signal and the expected Standard Model background. The study focuses on the muonic decay channel of A&#8242;, utilizing several MVA classifiers such as Fisher, Deep Neural Network (DNN), and the Boosted Decision Tree (BDT), aiming to discriminate between the signal of several benchmark points, within theoretical and experimental limits, and the Standard Model background, and to explore their discovery potential at the ILC.

Egypt

Hossam Taha

El-Sayed A. El-Dahshan

S. Elgammal

Search for a dark gauge boson within Einstein-Cartan theory at the ILC using multivariate analysis

We explore whether the unprecedented energy resolution of upcoming gamma-ray telescopes can uncover relativistic effects in photon spectra resulting from dark matter (DM) annihilation or decay near the supermassive black hole (SMBH) at the Galactic Center (GC), specifically, gravitational redshift, Doppler broadening due to Lorentz boosts, and kinetic energy enhancements arising from high DM velocities. By modeling DM density and velocity profiles under various SMBH formation scenarios and DM properties, we calculate the corresponding gamma-ray spectra and identify the conditions under which SMBH-induced spectral distortions become observable. We find that, in favorable cases, the observed spectra encode the DM velocity distribution near the SMBH, enabling potential discrimination among annihilation mechanisms with different velocity dependencies. Even when SMBH-induced effects are modest, the upcoming COSI mission, with sub-percent energy resolution surpassing the typical DM velocity dispersion at the GC, $$ \mathcal{O}\left({10}^{-3}\right) $$ , may still be able to detect subtle Doppler broadening. These results highlight a promising pathway for determining the origin of gamma-ray signals and probing DM properties through high-resolution spectral measurements.

Yu Watanabe

United States

Alexander Kusenko

Shigeki Matsumoto

Indirect detection of dark matter around a supermassive black hole with high energy-resolution gamma-ray telescopes