We investigate the collider signatures of a maximally flavor-violating $ U(1)_{L_\mu-L_\tau} $ model, where a new gauge boson $ Z^\prime $ and scalar triplets induce lepton flavor-changing interactions in the $\textit{μ}$-$\textit{τ}$ sector. Focusing on four-lepton final states at multi-TeV lepton colliders, we conduct a detailed analysis of cross sections, asymmetries, and polarization effects. We show that the signal cross section is highly sensitive to $ m_{Z^\prime} $ and the effective parameters $ \tilde{g}/m_{Z^\prime} $ , whereas it remains largely insensitive to the triplet Yukawa couplings within the phenomenologically allowed region. The forward-backward asymmetry exhibits a characteristic monotonic dependence on $ m_{Z^\prime} $ , and beam polarization can significantly suppress the Standard Model backgrounds while enhancing new physics contributions. We find that, in the phenomenologically allowed parameter space, the predicted observables remain highly sensitive to the underlying model parameters. These results show that multi-lepton final states are powerful probes of the $ U(1)_{L\mu - L_\tau} $ framework and can offer valuable guidance for future searches at muon and electron-positron colliders.

China

Jianing Qin

Fei Huang

Honglei Li

Zhi-Long Han

Jin Sun

Collider probes of four-lepton final states in maximally flavor-violating ${U(1)_{L_\mu-L_\tau}} $ model * Supported by National Natural Science Foundation of China (12505112, 11805081), Shandong Province Natural Science Foundation (ZR2024QA138, ZR2022MA056) and State Key Laboratory of Dark Matter Physics, University of Jinan Disciplinary Cross-Convergence Construction Project 2024 (XKJC- 202404) and Jin Sun is supported by IBS under the project code, (IBS-R018-D1)

We propose two medium-baseline, kiloton-scale neutrino experiments to study neutrinos from LHC proton-proton collisions: the Surface-based Integrated Neutrino Experiment (SINE), a surface-based scintillator panel detector observing muon neutrinos from the compact muon solenoid interaction point, and the UNDerwater Integrated Neutrino Experiment (UNDINE), a water Cherenkov detector submerged in lake Geneva observing all-flavor neutrinos from LHCb. Using a Monte Carlo simulation, we estimate millions of neutrino interactions during the high-luminosity LHC era. We show that these datasets can constrain neutrino cross sections, charm production in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>p</mi><mi>p</mi></math> collisions, strangeness enhancement as a solution to the cosmic-ray muon puzzle, and heavy neutral leptons. SINE and UNDINE thus offer a cost-effective medium-baseline complement to the proposed short-baseline forward physics facility.

United States

Nicholas W. Kamp

Carlos A. Argüelles

Albrecht Karle

United Kingdom

Jennifer Thomas

Tianlu Yuan

Lake- and surface-based detectors for forward neutrino physics

The <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>Z</mi><mn>0</mn></msup></math> bosons produced in electron-positron collisions at the potential Future Circular Collider (FCC-ee) provide unique opportunities for flavor physics. The nonzero polarization of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi mathvariant="normal">Λ</mi><mi>b</mi><mn>0</mn></msubsup></math> baryons produced in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>Z</mi><mn>0</mn></msup></math> decays enables access to a much larger set of observables than at the LHC, where the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi mathvariant="normal">Λ</mi><mi>b</mi><mn>0</mn></msubsup></math> baryons are produced unpolarized. This paper presents a toy angular analysis of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi mathvariant="normal">Λ</mi><mi>b</mi><mn>0</mn></msubsup><mo stretchy="false">→</mo><mrow><mi mathvariant="normal">Λ</mi><mo stretchy="false">(</mo><mo stretchy="false">→</mo><mi>p</mi><msup><mi>π</mi><mo>−</mo></msup><mo stretchy="false">)</mo><msup><mi>μ</mi><mo>+</mo></msup><msup><mi>μ</mi><mo>−</mo></msup></mrow></math> decays using simulation samples of collisions at the FCC-ee reconstructed using the IDEA detector concept and assuming a dataset of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>6</mn><mo>×</mo><msup><mn>10</mn><mn>12</mn></msup></math> <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>Z</mi><mn>0</mn></msup></math> bosons. While the statistical sensitivity achieved for individual angular observables is not expected to significantly exceed that from the LHCb Upgrade II experiment, the addition of the polarized observables leads to a significant improvement of the knowledge on the Wilson coefficients <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>C</mi><msup><mn>9</mn><mrow><mo stretchy="false">(</mo><mo>′</mo><mo stretchy="false">)</mo></mrow></msup></msub></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>C</mi><mrow><msup><mn>10</mn><mrow><mo stretchy="false">(</mo><mo>′</mo><mo stretchy="false">)</mo></mrow></msup></mrow></msub></math>.

Anja Beck

Mero Elmarassy

Asher Sabbagh

Michal Kreps

Eluned Smith

Constraints on new physics from decays of polarized <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi mathvariant="normal">Λ</mi><mi>b</mi><mn>0</mn></msubsup></math> baryons at the FCC-ee

Several possible excesses around $ 95 $ GeV hint at an additional light scalar beyond the Standard Model. We examine the capability of the Circular Electron-Positron Collider (CEPC) to test this hypothesis in the Higgs-strahlung channel $ e^{+}e^{-} \to ZS $ with $ Z \to\mu^{+}\mu^{-} $ and $ S \to\tau^{+}\tau^{-} $ . A full detector simulation shows that the optimal center-of-mass energy for studying the 95 GeV light scalar is 210 GeV. A deep neural network classifier reduces the luminosity required for discovery by half. At $ L = 20\; \mathrm{ab}^{-1} $ , the $ 5\sigma $ sensitivity of the CEPC to the signal strength $ \mu_{\tau\tau}^{ZS} $ reaches 0.016 and 0.020 for $ \sqrt{s} = 210 $ GeV and 240 GeV, respectively. The corresponding thresholds for a 5% precision measurement are $ \mu_{\tau\tau}^{ZS} \gt 0.10 $ and $ \gt 0.12 $ . At $ \sqrt{s}=210 $ GeV (240 GeV), the $ 5\sigma $ coverage of all N2HDM-Flipped samples with $ \chi^2_{h_{95}} \lt 7.82 $ requires $ L=800\ \mathrm{fb}^{-1} $ (1.22 $ \mathrm{ab}^{-1} $ ). These results establish a 210 GeV run, augmented by machine-learning selection, as the most efficient strategy to confirm or refute the 95 GeV excess at future lepton colliders.

Yabo Dong

Manqi Ruan

Kun Wang

Haijun Yang

Jingya Zhu

Testing a 95 GeV Scalar at the CEPC with Machine Learning * This work was supported by the National Natural Science Foundation of China under Grant No. 12275066 and by the startup research funds of Henan University. The work of K. Wang was also supported by the Open Project of the Shanghai Key Laboratory of Particle Physics and Cosmology under Grant No. 22DZ2229013-3. The work of M. Ruan was also supported by the National Key Program for S&T Research and Development under Contract No. 2024YFA1610603. The work of H. Yang was also supported by the National Natural Science Foundation of China under Grant No. W2441004.

Off-shell characteristics of pion generalized parton distributions (GPDs) and transverse momentum dependent parton distributions (TMDs) are examined within the framework of the Nambu–Jona-Lasinio model. In our previous studies, we separately investigated the properties of on-shell pion GPDs and light-front wave functions. Comparing the differences between on-shell and off-shell pion GPDs is particularly intriguing becuase it enables us to explore the effects associated with off-shellness. The absence of crossing symmetry causes the moments of GPDs to incorporate odd powers of the skewness parameter, resulting in new off-shell form factors. Through our calculations, we derived correction functions that account for modifications in pion GPDs attributed to off-shell effects. Unlike their on-shell counterparts, certain properties break down in the off-shell scenario; for example, symmetry properties and polynomiality conditions may no longer hold. In addition, we evaluate off-shell TMDs and compare them with their on-shell equivalents while also investigating their dependence on $ {\boldsymbol{k}}_{\perp} $ .

Jin-Li Zhang

Off-shell modifications of pion generalized parton distributions and transverse momentum dependent parton distributions * Supported by the Scientific Research Foundation of Nanjing Institute of Technology (YKJ202352) and the General Program of the Natural Science Foundation of Jiangsu Higher Education Institutions (25KJD140001)

Rare decays of the Z boson provide a sensitive probe for physics beyond the standard model. This study investigates the <math altimg='si49.svg'><mrow><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>&#8722;</mo></msup><mo>&#8594;</mo><mi>Z</mi><mo>&#8594;</mo><mi>&#957;</mi><mover accent='true'><mi>&#957;</mi><mo>&#175;</mo></mover><mi>&#947;</mi></mrow></math> process within the context of the Tera-Z programmes at future colliders such as the FCC-ee and CEPC. The SM predicts a one-loop branching ratio of <math altimg='si50.svg'><mrow><mn>7.16</mn><mo linebreak='goodbreak'>&#215;</mo><msup><mn>10</mn><mrow><mo>&#8722;</mo><mn>10</mn></mrow></msup></mrow></math> for <math altimg='si6.svg'><mrow><mi>Z</mi><mo>&#8594;</mo><mi>&#957;</mi><mover accent='true'><mi>&#957;</mi><mo>&#175;</mo></mover><mi>&#947;</mi></mrow></math>, a value four times smaller than the current experimental limit from the LEP. To explore this window for new physics, we parameterize anomalous <math altimg='si1.svg'><mrow><mi>Z</mi><mi>&#957;</mi><mover accent='true'><mi>&#957;</mi><mo>&#175;</mo></mover><mi>&#947;</mi></mrow></math> interactions using an Effective Field Theory framework, considering both dimension-6 and dimension-8 operators. A detailed simulation is performed by generating signal and background events with MadGraph, modeling particle showers with Pythia, and simulating detector effects with Delphes. The analysis employs key kinematic variables-including the photon energy ( <italic>E<inf>&#947;</inf></italic>), missing transverse energy ( <math altimg='si51.svg'><mrow><mi>E</mi><msub><mi>&#824;</mi><mi>T</mi></msub></mrow></math>), and the missing transverse energy significance ( <math altimg='si18.svg'><msub><mi>S</mi><mrow><mi>E</mi><msub><mi>&#824;</mi><mi>T</mi></msub></mrow></msub></math>) to isolate the signal. The results yield upper limits on the anomalous couplings, from which we infer branching ratios for <math altimg='si6.svg'><mrow><mi>Z</mi><mo>&#8594;</mo><mi>&#957;</mi><mover accent='true'><mi>&#957;</mi><mo>&#175;</mo></mover><mi>&#947;</mi></mrow></math> on the order of <math altimg='si52.svg'><msup><mn>10</mn><mrow><mo>&#8722;</mo><mn>9</mn></mrow></msup></math>. This represents a significant improvement of several orders of magnitude over the LEP sensitivity. Consequently, this study demonstrates the unique potential of the Tera-Z runs not only to test the SM loop-level predictions with unprecedented precision but also to tightly constrain or reveal new anomalous interactions.

Türkiye

H. Denizli

A. Senol

M. Köksal

Search for new physics effects in <math altimg='si26.svg'><mrow><mi>&#957;</mi><mover accent='true'><mi>&#957;</mi><mo>&#175;</mo></mover><mi>&#947;</mi></mrow></math> production at a tera-Z factory

Foundation models use large datasets to build an effective representation of data that can be deployed on diverse downstream tasks. Previous research developed the omnilearn foundation model for jet physics, using unique properties of particle physics, and showed that it could significantly advance discovery potential across collider experiments. This paper introduces a major upgrade, resulting in the omnilearned framework. This framework has three new elements: (1) updates to the model architecture and training, (2) using over <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>1</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>9</mn></mrow></msup></mrow></math> jets used for training, and (3) providing well-documented software for accessing all datasets and models. We demonstrate omnilearned with three representative tasks: top-quark jet tagging with the community delphes-based benchmark dataset, b tagging with ATLAS full simulation, and anomaly detection with CMS experimental data. In each case, omnilearned is the state of the art, further expanding the discovery potential of past, current, and future collider experiments.

Wahid Bhimji

Chris Harris

Japan

Vinicius Mikuni

Benjamin Nachman

Foundation model framework for all tasks involving jet physics

India

Rimi Debnath

Sanjeeda Sultana

Khandro K. Chokyi

Surajit Chattopadhyay

Corrigendum to “Phenomenological insights into holographically reconstructed fractional action cosmology: Cosmic dynamics, thermodynamics, and statefinder diagnostics” [Nuclear Physics B Volume: 1018 (September 2025) 117074]

Motivated by the stringent experimental bounds on proton lifetime and the need for precise low-energy predictions, there has been renewed interest in the renormalization group (RG) evolution of Wilson coefficients for baryon number violating (BNV) operators and their characteristic new-physics scales. In this work, we analyze the RG running of dimension-6 four-fermion operators in the $$ \overline{\textrm{MS}} $$ scheme that mediate nucleon decay channels such as $\textit{p}$ → $\textit{e}$ $\textit{π}$ , while systematically accounting for the impact of baryon number conserving (BNC) new-physics that can enter the theory at an intermediate scale as higher-dimensional effective field theory operators. These BNC operators mix with BNV ones at 1-loop and alter the RG flow. The running is performed from the electroweak scale up to representative intermediate scales of 10 GeV, 10 GeV, and 10 GeV, corresponding to possible thresholds for new BNC degrees of freedom. Comparing the RG evolved coefficients with current experimental bounds on nucleon decay lifetimes, we find that the inclusion of BNC-BNV mixing, dominated by top quark loops, can significantly lower the effective proton decay scale to ∼ 10 GeV, thus mitigating the need of a large desert. A Python package (Available at: ) is provided to facilitate the RG evolution of nucleon-decay Wilson coefficients, allowing for the inclusion of generic BNC effects.

Mathew Arun

M Shyam

Ritik Pal

RG evolution and effect of intermediate new-physics on ∆$\textit{B}$ = 1 four-fermion operators

We investigate the potential of single-spin components of the spin-density matrix in the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup><mo stretchy="false">→</mo><mi>t</mi><mover accent="true"><mi>t</mi><mo stretchy="false">¯</mo></mover></math> process at a future FCC-ee for probing heavy new physics parametrized using the Standard Model effective field theory (SMEFT) framework. We consider the full spectrum of spin observables and the complete angular decomposition of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>t</mi><mover accent="true"><mi>t</mi><mo stretchy="false">¯</mo></mover></math> production process in our study. We find that single-spin measurements generically provide stronger probes of SMEFT Wilson coefficients than measurements where the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>t</mi><mover accent="true"><mi>t</mi><mo stretchy="false">¯</mo></mover></math> spins are correlated, and that single-spin observables are important for resolving flat directions that can appear in the Wilson-coefficient parameter space.

Haotian Cao

Frank Petriello

Single-spin measurements and heavy new physics in the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup><mo stretchy="false">→</mo><mi>t</mi><mover accent="true"><mi>t</mi><mo stretchy="false">¯</mo></mover></math> process at an FCC-ee