The Galactic Center GeV Excess (GCE) remains a compelling but enigmatic signal from the inner regions of our galaxy. Muonphilic dark matter (DM), which couples exclusively to muons via a new mediator, provides a viable explanation for the GCE and relic density while naturally evading constraints from direct detection, collider searches, and other multimessenger observations. Based on the viable nonresonant parameter space identified in previous global fits, we perform a comprehensive study on the prospects for discovering such muonphilic DM in the context of a future 3 TeV muon collider, focusing on simplified models with a $Z_2$ -even mediator. Four distinct search strategies are investigated: visible on-shell mediator decays ( $\mu^{+}\mu^{-}\gamma$ final state), invisible on-shell mediator decays (mono-photon plus missing energy), mono-photon production via off-shell mediators, and vector boson fusion production. Through a detailed signal-background analysis using cut-and-count methods, we project the exclusion limits at $ 95 $ % confidence level for seven representative models across a wide range of mediator masses. Our results demonstrate that the projected limits cover a significant portion of viable parameter space that explains the GCE, establishing a muon collider as a decisive machine for testing the muonphilic DM hypothesis.

China

Wanyun Chen

Haoqi Li

Chih-Ting Lu

Qiulei Wang

Exploring muonphilic dark matter with the $\textit{Z}$ $_{2}$-even mediator at muon colliders * Chih-Ting Lu, Wanyun Chen and Haoqi Li are supported by the National Natural Science Foundation of China (NNSFC) (12335005, 12575118) and the Special funds for postdoctoral overseas recruitment, Ministry of Education of China

The processes of $ K^-p \to \pi^0 \pi^0 \Sigma^0 $ and $ K^- p \to \pi^0 \Lambda(1405) $ are studied within the effective Lagrangian approach. In addition to the “background” contribution from the $\textit{u}$-channel nucleon pole term, the contribution from the $ \Sigma(1660) $ resonance with spin-parity $ J^P=1/2^+ $ is also considered. For the $ K^-p \to \pi^0 \pi^0 \Sigma^0 $ reaction, we perform a calculation for the total and differential cross sections by considering the contribution from the $ \Sigma(1660) $ intermediate resonance decaying into $ \pi^0 \Lambda(1405) $ with $ \Lambda(1405) $ decaying into $ \pi^0 \Sigma^0 $ . With our model parameters, the available experimental data on both the $ K^-p \to \pi^0 \pi^0 \Sigma^0 $ and $ K^- p \to \pi^0 \Lambda(1405) $ reactions can be fairly well reproduced. It is shown that the contribution from the $ \Sigma(1660) $ resonance is necessary, and that these experimental measurements could be used to determine some properties of the $ \Sigma(1660) $ resonance.

Xing-Yi Ji

Si-Wei Liu

Wen-Tao Lyu

De-Min Li

En Wang

Ju-Jun Xie

Role of Σ(1660) in the $\textit{K}$ $^{−}$ $\textit{p}$ → $\textit{π}$ $^{0}$ $\textit{π}$ $^{0}$Σ$^{0}$ reaction * Supported by the National Key R&D Program of China (2023YFA1606703, 2024YFE0105200), the National Natural Science Foundation of China (12435007, 12475086, 12192263, 12361141819, 1252200936), the Natural Science Foundation of Henan (232300421140, 252300423951) and the Zhengzhou University Young Student Basic Research Projects (PhD students) (ZDBJ202522)

We have performed an updated analysis of the angular distribution of the $ \psi(3686) \to p\bar{p} $ decay by considering transverse beam polarization to investigate potential sources of forward-backward asymmetry and azimuthal modulation beyond the simple $ 1+\alpha\cos^2\theta $ form. We focus on the interference between the $ \psi(3686) $ resonance and two-photon exchange continuum process, as well as on the background from initial-state–final-state radiation (ISR–FSR) interference. A maximum-likelihood fit to the $ \cos\theta $ distribution of $ \psi(3686)\to p\bar{p} $ yields $ \alpha = 1.00 \pm 0.03 $ , which is consistent with previous results. Our model predicts a significant $ \sin(2\phi) $ modulation in the azimuthal angle, indicating the influence of transverse beam polarization. Based on these findings, two-dimensional angular analyses can be conducted in the future to fully disentangle the polarization and interference dynamics in charmonium decays to baryon pairs.

Zhi Gao

Rong-Gang Ping

Minggang Zhao

Update analysis of $ {\psi(3686)\to p\bar{p}}$ * The work is partly supported by the National Natural Science Foundation of China(NSFC) (12575112)

This study investigates the ultraviolet realization of semileptonic four-fermion operator $ O_{ledq}^{\alpha \beta 11} $ that incorporates Majorana dark matter (DM) in both lepton-flavor-conserving (LFC) and lepton-flavor-violating (LFV) scenarios at the one-loop level via box diagram, thereby effectively alleviating the lower bounds on the new physics scale. In addition, we investigate the interplay between model-independent constraints on the Wilson coefficients and DM direct detection, relic density, and collider searches in the context of fermion portal DM model with two mediators. We found that both the projected future constraint on the LFC Wilson coefficient $ C_{ledq}^{2211}/\Lambda^2 \lt $ $ (12.3\; \text{TeV})^{-2} $ from the measurements of neutrino non-standard interaction in the next-generation neutrino oscillation experiments, and the LFV constraint $ C_{ledq}^{1211}/\Lambda^2 \lt \left(2.2\times 10^3\; \text{TeV} \right)^{-2} $ from ongoing charged-lepton-flavor-violation searches, provide a complementary exploration of the parameter space encompassing the DM and scalar masses. With a colored mediator mass of approximately $ 2\; \text{TeV} $ , the sensitivity of the indirect constraints on the four-fermion operator can surpass those of collider searches and DM direct detection, in scenarios where the masses of the DM and scalar are close. By ensuring the correct DM relic density, however, we find that the collider searches and DM direct detection are more sensitive to the electroweak-scale DM and scalar than indirect constraints.

Yuxuan He

Gang Li

Jia Liu

Xiao-Ping Wang

Xiang Zhao

Lepton flavor of four-fermion operator and fermion portal dark matter * Gang Li and Xiang Zhao are supported by the National Natural Science Foundation of China (12347105, 12505127), the Guangdong Basic and Applied Basic Research Foundation (2024A1515012668). The work of Jia Liu is supported by the National Science Foundation of China (12235001, 12475103) and State Key Laboratory of Nuclear Physics and Technology (NPT2025ZX11). The work of Xiao-Ping Wang is supported by National Science Foundation of China (12375095) and the Fundamental Research Funds for the Central Universities

Extracting accurate results from neutrino oscillation and cross section experiments requires accurate simulation of the neutrino-nucleus interaction. The rescattering of outgoing hadrons (final state interactions) by the rest of the nucleus is an important component of these interactions. We present a new measurement of proton transparency (defined as the fraction of outgoing protons that emerge without significant rescattering) using electron-nucleus scattering data recorded by the CLAS detector at Jefferson Laboratory on helium, carbon, and iron targets. This analysis uses a new data-driven method to extract the transparency. It defines transparency as the ratio of electron-scattering events with a detected proton to quasi-elastic electron-scattering events where a proton should have been knocked out. Our results are consistent with previous measurements that determined the transparency from the ratio of measured events to theoretically predicted events. We find that the GENIE event generator, which is widely used by oscillation experiments to simulate neutrino-nucleus interactions, needs to better describe both the nuclear ground state and proton rescattering in order to reproduce our measured transparency ratios, especially at lower proton momenta.

United States

S. Dytman

M. Betancourt

N. Steinberg

L.B. Weinstein

Israel

A. Ashkenazi

J. Tena-Vidal

A. Papadopoulou

G. Chambers-Wall

J. Smith

P. Achenbach

France

J.S. Alvarado

M.J. Amaryan

H. Atac

Saudi Arabia

L. Baashen

N.A. Baltzell

Italy

L. Barion

United Kingdom

M. Bashkanov

M. Battaglieri

F. Benmokhtar

A. Bianconi

A.S. Biselli

M. Bondi

F. Bossù

S. Boiarinov

Germany

K.-Th. Brinkmann

W.J. Briscoe

Chile

W.K. Brooks

S. Bueltmann

V.D. Burkert

T. Cao

R. Capobianco

D.S. Carman

J.C. Carvajal

P. Chatagnon

Russia

V. Chesnokov

H. Chinchay

G. Ciullo

P.L. Cole

M. Contalbrigo

A. D’Angelo

Armenia

N. Dashyan

R. De Vita

M. Defurne

A. Deur

S. Diehl

C. Djalali

R. Dupre

H. Egiyan

A. El Alaoui

L. El Fassi

L. Elouadrhiri

M. Farooq

S. Fegan

I.P. Fernando

A. Filippi

G. Gavalian

G.P. Gilfoyle

R.W. Gothe

L. Guo

K. Hafidi

H. Hakobyan

M. Hattawy

F. Hauenstein

T.B. Hayward

D. Heddle

A. Hobart

M. Holtrop

Yu-Chun Hung

Y. Ilieva

D.G. Ireland

E.L. Isupov

H. Jiang

South Korea

H.S. Jo

S. Joosten

M. Khandaker

A. Kim

W. Kim

F.J. Klein

V. Klimenko

A. Kripko

V. Kubarovsky

S.E. Kuhn

L. Lanza

P. Lenisa

D. Marchand

V. Mascagna

D. Matamoros

B. McKinnon

T. Mineeva

M. Mirazita

V. Mokeev

C. Munoz Camacho

P. Nadel-Turonski

T. Nagorna

K. Neupane

D. Nguyen

S. Niccolai

M. Osipenko

L.L. Pappalardo

R. Paremuzyan

Proton transparency and neutrino physics: New methods and modeling

Brazil

Níckolas Aguiar Alves

Lectures on the Bondi–Metzner–Sachs Group and related topics in infrared physics

We study the processes <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>ν</mi><mi>τ</mi></msub><mi>n</mi><mo stretchy="false">→</mo><msub><mi mathvariant="normal">Λ</mi><mi>c</mi></msub><msup><mi>τ</mi><mo>−</mo></msup><mo stretchy="false">(</mo><msup><mi>π</mi><mo>−</mo></msup><msub><mi>ν</mi><mi>τ</mi></msub><mo stretchy="false">)</mo></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mover accent="true"><mi>ν</mi><mo stretchy="false">¯</mo></mover><mi>τ</mi></msub><mi>p</mi><mo stretchy="false">→</mo><mi mathvariant="normal">Λ</mi><msup><mi>τ</mi><mo>+</mo></msup><mo stretchy="false">(</mo><msup><mi>π</mi><mo>+</mo></msup><msub><mover accent="true"><mi>ν</mi><mo stretchy="false">¯</mo></mover><mi>τ</mi></msub><mo stretchy="false">)</mo></math>, with particular emphasis on the pion energy and angular distributions, as a possible signal for lepton flavor universality violation, and in general of physics beyond the Standard Model (SM), as well as a sensitive probe of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>τ</mi></math> polarization vector. We work within an effective low-energy extension of the SM with all dimension-six four-fermion operators. In this framework, complex Wilson coefficients which encode new physics can generate <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>C</mi><mi>P</mi></mrow></math>-violating contributions. We propose an observable that provides a genuine <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>C</mi><mi>P</mi></mrow></math>-odd signal due to its sensitivity to particular transverse components of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>τ</mi></math> polarization vector. Namely, we show that the asymmetry in the azimuthal-angle distribution of the pion in the decay <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>τ</mi><mo>±</mo></msup><mo stretchy="false">→</mo><msup><mi>π</mi><mo>±</mo></msup><msub><mi>ν</mi><mi>τ</mi></msub></math> constitutes a smoking-gun prediction of such a beyond the SM scenario. We estimate the strength of this effect extrapolating nucleon-hyperon form factors recently obtained from lattice QCD calculations.

Spain

E. Hernández

J. Nieves

Sweden

J.E. Sobczyk

Probing new physics and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>C</mi><mi>P</mi></mrow></math> violation in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>ν</mi><mi>τ</mi></msub><mi>n</mi><mo stretchy="false">→</mo><msub><mi mathvariant="normal">Λ</mi><mi>c</mi></msub><msup><mi>τ</mi><mo>−</mo></msup><mo stretchy="false">(</mo><msup><mi>π</mi><mo>−</mo></msup><msub><mi>ν</mi><mi>τ</mi></msub><mo stretchy="false">)</mo></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mover accent="true"><mi>ν</mi><mo stretchy="false">¯</mo></mover><mi>τ</mi></msub><mi>p</mi><mo stretchy="false">→</mo><mi mathvariant="normal">Λ</mi><msup><mi>τ</mi><mo>+</mo></msup><mo stretchy="false">(</mo><msup><mi>π</mi><mo>+</mo></msup><msub><mover accent="true"><mi>ν</mi><mo stretchy="false">¯</mo></mover><mi>τ</mi></msub><mo stretchy="false">)</mo></math>

Testing new-physics (NP) scenarios that couple predominantly to the third generation is notoriously difficult experimentally, as exemplified by comparing limits for the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>τ</mi></math> lepton dipole moments to those of electrons and muons. In this case, extracting limits from processes such as <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><msup><mi>τ</mi><mo>+</mo></msup><msup><mi>τ</mi><mo>−</mo></msup></math> often relies on effective-field-theory (EFT) arguments, which allow for model-independent statements, but only apply if the NP scale is sufficiently large compared to the center-of-mass energy. In this work we offer a comprehensive analysis of light NP contributions to the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>τ</mi></math> dipole moments, providing a detailed account of the interpretation of asymmetry measurements in <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><msup><mi>τ</mi><mo>+</mo></msup><msup><mi>τ</mi><mo>−</mo></msup></math> that are tailored toward the extraction of dipole moments, for the test cases of new light spin-0 and spin-1 bosons. Moreover, we study the decoupling to the EFT limit in these scenarios and discuss the complementarity to constraints from other related processes, such as production in <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></math> reactions. While covering a wide range of light NP scenarios, as specific case study we present a detailed discussion of a tauphilic gauge vector boson at Belle II.

Switzerland

Martin Hoferichter

Gabriele Levati

Light new physics and the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>τ</mi></math> lepton dipole moments

While electron and muon dipole moments are well-established precision probes of physics beyond the standard model, it is notoriously challenging to test realistic new physics (NP) scenarios for the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>τ</mi></math> lepton. Constructing suitable asymmetries in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi>e</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>e</mi></mrow><mrow><mo>−</mo></mrow></msup><mo stretchy="false">→</mo><msup><mrow><mi>τ</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>τ</mi></mrow><mrow><mo>−</mo></mrow></msup></mrow></math> has emerged as a promising such avenue, providing access to the electric and magnetic dipole moment once a polarized electron beam is available, e.g., with the proposed polarization upgrade of the SuperKEKB <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></math> collider. However, this interpretation relies on an effective-field-theory (EFT) argument that only applies if the NP scale is large compared to the center-of-mass energy. In this Letter, we address the consequences of the asymmetry measurements in the case of light NP, using light spin-0 and spin-1 bosons as test cases, to show how results can again be interpreted as constraints on dipole moments, albeit in a model-dependent manner, and how the decoupling to the EFT limit proceeds in these cases. In particular, we observe that the imaginary parts generated by light new particles can yield nonvanishing asymmetries even without electron polarization, which can again be interpreted as constraints on the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>τ</mi></math> anomalous magnetic moment. This proposed measurement, thus, presents a novel opportunity for NP searches that can be realized already with present data at Belle II.

Light New Physics and the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>τ</mi></math> Lepton Dipole Moments: Prospects at Belle II

We employ an approximate conserved quantum number [defined as “<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>b</mi></math> parity” in <a href="http://dx.doi.org/10.1103/PhysRevLett.86.3722">Phys. Rev. Lett. 86, 3722 (2001)</a>] of the Standard Model (SM): <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>b</mi><mi>P</mi></msub><mo>=</mo><mo stretchy="false">(</mo><mo>−</mo><mn>1</mn><msup><mo stretchy="false">)</mo><mi>n</mi></msup></math>, where <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>n</mi></math> is the number of produced <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>b</mi></math> jets in the reaction <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>e</mi><mo>+</mo><mi>p</mi><mo>/</mo><mi>A</mi><mo stretchy="false">→</mo><mi>n</mi><mo>·</mo><msub><mi>j</mi><mi>b</mi></msub><mo>+</mo><mi>X</mi></math>, to explore new TeV-scale flavor-changing interactions involving the third-generation quarks at the Electron-Ion Collider (EIC); simply by counting the number of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>b</mi></math> jets in the final state. In particular, the SM single and dijet production at the EIC, which occurs through charge current interactions, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>e</mi><mo>+</mo><mi>p</mi><mo>/</mo><mi>A</mi><mo stretchy="false">→</mo><mi>j</mi><mo>+</mo><mrow><msub><menclose notation="updiagonalstrike"><mi>E</mi></menclose><mi>T</mi></msub></mrow></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>e</mi><mo>+</mo><mi>p</mi><mo>/</mo><mi>A</mi><mo stretchy="false">→</mo><mn>2</mn><mo>·</mo><mi>j</mi><mo>+</mo><mrow><msub><menclose notation="updiagonalstrike"><mi>E</mi></menclose><mi>T</mi></msub></mrow></math>, are <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>b</mi><mi>P</mi></msub></math> even since the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>b</mi><mi>P</mi></msub></math>-violating (i.e., <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>b</mi><mi>P</mi></msub><mo>=</mo><mo>−</mo><mn>1</mn></math>) SM signals for these processes are necessarily Cabibbo-Kobayashi-Maskawa suppressed and, therefore, have a vanishingly small production rate. In contrast, new flavor physics can generate <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>b</mi><mi>P</mi></msub><mo>=</mo><mo>−</mo><mn>1</mn></math> signals at the EIC whose only significant SM background is due to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>b</mi></math>-jet misidentification. We thus show that <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>b</mi><mi>P</mi></msub></math> can be used as a simple and sensitive probe of new flavor-violating physics; specifically, we find that counting single <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>b</mi></math>-jet events in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>e</mi><mo>+</mo><mi>p</mi><mo>/</mo><mi>A</mi><mo stretchy="false">→</mo><mi>j</mi><mo>+</mo><mrow><msub><menclose notation="updiagonalstrike"><mi>E</mi></menclose><mi>T</mi></msub></mrow></math> at the EIC with a center-of-mass (c.m.) energy of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msqrt><mi>s</mi></msqrt><mo>∼</mo><mn>140</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math> can probe scales of new physics up to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="normal">Λ</mi><mo>≲</mo><mi mathvariant="script">O</mi><mo stretchy="false">(</mo><mn>5</mn><mo stretchy="false">)</mo><mtext> </mtext><mtext> </mtext><mi>TeV</mi></mrow></math> for a certain type of new chiral flavor-changing physics in third-generation interactions. This is remarkably more than 30 times larger than the assumed EIC c.m. energy and it critically depends on the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>b</mi></math>-tagging efficiency and purity as well as the feasibility of electron beam polarization. The sensitivity of the dijet process, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>e</mi><mo>+</mo><mi>p</mi><mo>/</mo><mi>A</mi><mo stretchy="false">→</mo><mn>2</mn><mi>j</mi><mo>+</mo><mrow><msub><menclose notation="updiagonalstrike"><mi>E</mi></menclose><mi>T</mi></msub></mrow></math>, to these types of new physics is reduced compared to the single-jet channel.

Shaouly Bar-Shalom

Jose Wudka

Flavor physics at the EIC with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>b</mi></mrow></math>-jet tagging