The observation of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi><mi>P</mi></math> violation in the difference of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi><mi>P</mi></math> asymmetries between <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>D</mi><mo stretchy="false">→</mo><msup><mi>K</mi><mo>+</mo></msup><msup><mi>K</mi><mo>−</mo></msup></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>D</mi><mo stretchy="false">→</mo><msup><mi>π</mi><mo>+</mo></msup><msup><mi>π</mi><mo>−</mo></msup></math> has raised a debate whether the observed asymmetries can be regarded as a signal of physics beyond the standard model (SM). In this paper we obtain all the topological amplitudes and isospin amplitudes directly from measured observables for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>D</mi><mo stretchy="false">→</mo><mi>π</mi><mi>π</mi></math>. These results unambiguously imply a very large penguin contribution, having a central value 4.74 times the magnitude of the amplitude for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>D</mi><mn>0</mn></msup><mo stretchy="false">→</mo><msup><mi>π</mi><mo>+</mo></msup><msup><mi>π</mi><mo>−</mo></msup></math>. This fitted central value differs from a reasonable SM estimate of 10% with a significance greater than <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>3.3</mn><mi>σ</mi></math>. In contrast to previous studies, we present model-independent arguments based only on unitarity of rescattering amplitudes to show that large penguins cannot arise from rescattering alone and likely indicate physics beyond the SM. In a model-independent approach we show how a very small contribution from physics beyond the SM with a large weak phase alleviates the problem.

United States

India

Rahul Sinha

Thomas E. Browder

N.G. Deshpande

Poland

Dibyakrupa Sahoo

Nita Sinha

Implications of the evidence for direct <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi><mi>P</mi></math> violation in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>D</mi><mo stretchy="false">→</mo><msup><mi>π</mi><mo>+</mo></msup><msup><mi>π</mi><mo>−</mo></msup></math> decays

We propose a novel theoretical framework in which proton decay is induced by the dark matter. While proton decay requires violation of the $\textit{B}$ + $\textit{L}$ symmetry, dark matter stability often relies on the presence of an unbroken symmetry. These seemingly distinct phenomena are unified through the global U(1) symmetry inherent in the Standard Model. Its spontaneous breaking leads to a residual $\textit{Z}$ symmetry, which ensures dark matter stability and forbids proton decay at tree level. Consequently, proton decay occurs at the one-loop level, mediated by dark sector particles. The proton lifetime is linked with the dark matter, the heavier dark matter mass enhancing proton stability, and vice versa. The $$ \mathcal{O}\left(\textrm{TeV}\right) $$ masses of the mediators remain consistent with current proton lifetime limits, making them accessible to experimental searches. In particular, the leptoquark mediating proton decay, carrying exotic $\textit{B}$ + $\textit{L}$ charges, leads to a distinctive signature in collider searches. By intertwining proton decay, dark matter stability, and collider phenomenology, this framework offers distinctive signatures that can be probed in current and future experiments.

Ranjeet Kumar

Rahul Srivastava

Dark matter induced proton decays

Deep learning has achieved remarkable success in jet classification tasks, yet a key challenge remains: understanding what these models learn and how their features relate to known QCD observables. Improving interpretability is essential for building robust and trustworthy machine learning tools in collider physics. To address this challenge, we systematically investigate equivariant and IRC-safe graph neural networks for jet classification. Using simulated jet datasets, we compare IRC-safe architectures with inbuilt E(2) and O(2) equivariance in the rapidity-azimuth plane against IRC-safe and -unsafe baselines in terms of classification performance, robustness to soft emissions, and latent representation structures. Our analysis shows that IRC-safe and symmetry-aware networks are more stable across training instances and distribute their latent variance across multiple interpretable directions. By regressing Energy Flow Polynomials onto the leading principal components, we establish a direct correspondence between learned representations and established IRC-safe jet observables. These results demonstrate that embedding symmetry and safety constraints not only improves robustness but also grounds network representations in known QCD structures, providing a principled approach toward interpretable deep learning in collider physics.

Partha Konar

United Kingdom

Vishal Ngairangbam

Michael Spannowsky

Deepanshu Srivastava

Stable and interpretable jet physics with IRC-safe equivariant feature extraction

We introduce a new class of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>U</mi><mo stretchy="false">(</mo><mn>1</mn><msub><mo stretchy="false">)</mo><mi>X</mi></msub></math> symmetries where all Standard Model fermions are “chiral,” i.e., the left- and right-handed components have different charges under the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>U</mi><mo stretchy="false">(</mo><mn>1</mn><msub><mo stretchy="false">)</mo><mi>X</mi></msub></math> symmetry. Gauge anomaly cancellation is achieved by introducing three Standard Model gauge singlet dark fermions (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>f</mi><mi>i</mi></msup></math>; <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>i</mi><mo>=</mo><mn>1</mn></math>, 2, 3) charged under this symmetry. We systematically present chiral solutions for cases in which (a) one, (b) two, or (c) all three generations of Standard Model fermions are charged under the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>U</mi><mo stretchy="false">(</mo><mn>1</mn><msub><mo stretchy="false">)</mo><mi>X</mi></msub></math> symmetry. The <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>U</mi><mo stretchy="false">(</mo><mn>1</mn><msub><mo stretchy="false">)</mo><mi>X</mi></msub></math> charges of these dark fermions are uniquely determined by anomaly cancellation conditions. These new fermions belong to the dark sector, with the lightest of them being a good dark matter candidate. Additionally, the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>Z</mi><mo>′</mo></msup></math> gauge boson mediates interactions between the dark and visible sectors, and we call this <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>U</mi><mo stretchy="false">(</mo><mn>1</mn><msub><mo stretchy="false">)</mo><mi>X</mi></msub></math> symmetry as the “dark hypercharge” symmetry. Using a benchmark model, we explore phenomenological implications in the heavy <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>Z</mi><mo>′</mo></msup></math> case (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>M</mi><msup><mi>Z</mi><mo>′</mo></msup></msub><mo>&gt;</mo><msub><mi>M</mi><mi>Z</mi></msub></math>), analyzing collider constraints and examining the lightest dark fermion’s viability as dark matter. Our analysis shows that it satisfies all current dark matter constraints over a wide range of dark matter mass.

Hemant Prajapati

Dark hypercharge symmetry

We have made improved measurements of three-flavor neutrino mixing with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>19.7</mn><mo stretchy="false">(</mo><mn>16.3</mn><mo stretchy="false">)</mo><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>20</mn></mrow></msup></mrow></math> protons on target in (anti-)neutrino-enhanced beam modes. A new sample of muon-neutrino events with tagged pions has been added at the far detector, as well as new proton and photon-tagged samples at the near detector. Significant improvements have been made to the flux and neutrino interaction modeling. T2K data continue to prefer the normal mass ordering and upper octant of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi>sin</mi></mrow><mrow><mn>2</mn></mrow></msup><msub><mrow><mi>θ</mi></mrow><mrow><mn>23</mn></mrow></msub></mrow></math> with a near-maximal value of the charge-parity violating phase with best-fit values in the normal ordering of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>δ</mi></mrow><mrow><mi>CP</mi></mrow></msub><mo>=</mo><mo>−</mo><msubsup><mrow><mn>2.18</mn></mrow><mrow><mo>−</mo><mn>0.47</mn></mrow><mrow><mo>+</mo><mn>1.22</mn></mrow></msubsup></mrow></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi>sin</mi></mrow><mrow><mn>2</mn></mrow></msup><msub><mrow><mi>θ</mi></mrow><mrow><mn>23</mn></mrow></msub><mo>=</mo><msubsup><mrow><mn>0.559</mn></mrow><mrow><mo>−</mo><mn>0.078</mn></mrow><mrow><mo>+</mo><mn>0.018</mn></mrow></msubsup></mrow></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="normal">Δ</mi><msubsup><mrow><mi>m</mi></mrow><mrow><mn>32</mn></mrow><mrow><mn>2</mn></mrow></msubsup><mo>=</mo><mo stretchy="false">(</mo><msubsup><mrow><mo>+</mo><mn>2.506</mn></mrow><mrow><mo>−</mo><mn>0.052</mn></mrow><mrow><mo>+</mo><mn>0.039</mn></mrow></msubsup><mo stretchy="false">)</mo><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>3</mn></mrow></msup><mtext> </mtext><mtext> </mtext><msup><mrow><mi>eV</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></math>.

Japan

K. Abe

S. Abe

R. Akutsu

H. Alarakia-Charles

Y.I. Alj Hakim

Switzerland

S. Alonso Monsalve

L. Anthony

S. Aoki

K.A. Apte

T. Arai

T. Arihara

S. Arimoto

Y. Ashida

E.T. Atkin

N. Babu

JINR

V. Baranov

G.J. Barker

G. Barr

D. Barrow

P. Bates

L. Bathe-Peters

M. Batkiewicz-Kwasniak

N. Baudis

Italy

V. Berardi

L. Berns

S. Bhattacharjee

CERN

A. Blanchet

France

A. Blondel

P.M.M. Boistier

S. Bolognesi

S. Bordoni

S.B. Boyd

C. Bronner

A. Bubak

M. Buizza Avanzini

Spain

J.A. Caballero

F. Cadoux

N.F. Calabria

Vietnam

S. Cao

S. Cap

D. Carabadjac

S.L. Cartwright

M.P. Casado

M.G. Catanesi

J. Chakrani

A. Chalumeau

D. Cherdack

Russia

A. Chvirova

J. Coleman

G. Collazuol

Canada

F. Cormier

A.A.L. Craplet

A. Cudd

D. D’Ago

C. Dalmazzone

T. Daret

Hungary

P. Dasgupta

C. Davis

Yu. I. Davydov

P. de Perio

G. De Rosa

T. Dealtry

C. Densham

A. Dergacheva

R. Dharmapal Banerjee

F. Di Lodovico

G. Diaz Lopez

S. Dolan

D. Douqa

T.A. Doyle

O. Drapier

K.E. Duffy

J. Dumarchez

P. Dunne

K. Dygnarowicz

A. Eguchi

J. Elias

S. Emery-Schrenk

G. Erofeev

A. Ershova

G. Eurin

D. Fedorova

S. Fedotov

M. Feltre

L. Feng

D. Ferlewicz

A.J. Finch

M.D. Fitton

C. Forza

M. Friend

Y. Fujii

Y. Fukuda

Y. Furui

Belgium

J. García-Marcos

A.C. Germer

L. Giannessi

C. Giganti

M. Girgus

V. Glagolev

M. Gonin

Results from the T2K Experiment on Neutrino Mixing Including a New Far Detector <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>μ</mi></mrow></math>-like Sample

Charged lepton flavor-violating (cLFV) processes, which are definite proof of new physics beyond the Standard Model, have remained experimentally elusive to date. Effective field theory (EFT) has been very useful in providing information about such new physics through the higher-dimensional operators. These operators respect SM gauge invariance, and they are suppressed by appropriate powers of the energy scale <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Λ</mi></math>. In regard to lepton flavour violating (LFV) processes, the Standard Model effective field theory (SMEFT) is shown to be a useful tool for estimating any new physics effect at the scale <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Λ</mi></math>. It is worth noting that a large class of cLFV processes involves both quarks and leptons. Thus, low-energy observables play a significant role in providing bounds on lepton-flavor-violating 2-quark-2-lepton (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>2</mn><mi>q</mi><mn>2</mn><mo>ℓ</mo></math>) operators. In this work, we explore several low-energy cLFV processes that can be addressed within the SMEFT framework, relating them to the specific operators of relevance. Keeping in mind the correlation that exists among the SMEFT operators, we want to extract the strongest constraints on these <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>2</mn><mi>q</mi><mn>2</mn><mo>ℓ</mo></math> operators.

Utpal Chattopadhyay

Debottam Das

Rahul Puri

Joydeep Roy

Constraining lepton flavor violating SMEFT <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>2</mn><mi>q</mi><mn>2</mn><mo>ℓ</mo></math> operators from low-energy charged lepton flavor-violating processes

We report a flux-integrated cross section measurement of muon neutrino interactions on water and hydrocarbon via charged current reactions without charged pions in the final state with the WAGASCI-BabyMIND detector, which was installed in the T2K near detector hall in 2018. The detector is located 1.5° off-axis and is exposed to a more energetic neutrino flux than ND280, another T2K near detector, which is located at a different off-axis position. The total flux-integrated cross section is measured to be <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>1.26</mn><mo>±</mo><mn>0.18</mn><mo stretchy="false">(</mo><mtext>stat</mtext><mo>+</mo><mtext>syst</mtext><mo stretchy="false">)</mo><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>39</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mrow><msup><mrow><mi>cm</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>/</mo><mi>nucleon</mi></mrow></mrow></math> on CH and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>1.44</mn><mo>±</mo><mn>0.21</mn><mo stretchy="false">(</mo><mtext>stat</mtext><mo>+</mo><mtext>syst</mtext><mo stretchy="false">)</mo><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>39</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mrow><msup><mrow><mi>cm</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>/</mo><mi>nucleon</mi></mrow></mrow></math> on <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi mathvariant="normal">H</mi></mrow><mrow><mn>2</mn></mrow></msub><mi mathvariant="normal">O</mi></mrow></math>. These results are compared to model predictions provided by the neut v5.3.2 and genie v2.8.0 Monte Carlo generators and the measurements are compatible with these models. Differential cross sections in muon momentum and cosine of the muon scattering angle are also reported. This is the first such measurement reported with the WAGASCI-BabyMIND detector and utilizes the 2020 and 2021 datasets.

E.A.G. Goodman

Measurement of muon neutrino induced charged current interactions without charged pions in the final state using a new T2K off-axis near detector WAGASCI-BabyMIND

We report on the measurements of directed flow <math altimg='si14.svg'><msub><mi>v</mi><mn>1</mn></msub></math> and elliptic flow <math altimg='si9.svg'><msub><mi>v</mi><mn>2</mn></msub></math> for hadrons ( <math altimg='si4.svg'><msup><mi>&#960;</mi><mo>&#177;</mo></msup></math>, <math altimg='si5.svg'><msup><mi>K</mi><mo>&#177;</mo></msup></math>, <math altimg='si6.svg'><msubsup><mi>K</mi><mrow><mi>S</mi></mrow><mn>0</mn></msubsup></math>, <math altimg='si15.svg'><mi>p</mi></math>, <math altimg='si7.svg'><mi>&#981;</mi></math>, <math altimg='si2.svg'><mstyle mathvariant='normal'><mi>&#923;</mi></mstyle></math> and <math altimg='si8.svg'><msup><mstyle mathvariant='normal'><mi>&#926;</mi></mstyle><mo>&#8722;</mo></msup></math>) from Au+Au collisions at <math altimg='si16.svg'><msqrt><msub><mi>s</mi><mrow><mi>N</mi><mi>N</mi></mrow></msub></msqrt></math> = 3 GeV and <math altimg='si9.svg'><msub><mi>v</mi><mn>2</mn></msub></math> for ( <math altimg='si4.svg'><msup><mi>&#960;</mi><mo>&#177;</mo></msup></math>, <math altimg='si5.svg'><msup><mi>K</mi><mo>&#177;</mo></msup></math>, <math altimg='si15.svg'><mi>p</mi></math> and <math altimg='si17.svg'><mover><mrow><mi>p</mi></mrow><mo stretchy='true'>&#8254;</mo></mover></math>) at 27 and 54.4 GeV with the STAR experiment. While at the two higher energy midcentral collisions the number-of-constituent-quark (NCQ) scaling holds, at 3 GeV the <math altimg='si9.svg'><msub><mi>v</mi><mn>2</mn></msub></math> at midrapidity is negative for all hadrons and the NCQ scaling is absent. In addition, the <math altimg='si14.svg'><msub><mi>v</mi><mn>1</mn></msub></math> slopes at midrapidity for almost all observed hadrons are found to be positive, implying dominant repulsive baryonic interactions. The features of negative <math altimg='si9.svg'><msub><mi>v</mi><mn>2</mn></msub></math> and positive <math altimg='si14.svg'><msub><mi>v</mi><mn>1</mn></msub></math> slope at 3 GeV can be reproduced with a baryonic mean-field in transport model calculations. These results imply that the medium in such collisions is likely characterized by baryonic interactions.

D. Isenhower

J.L. Drachenberg

M. Daugherity

L. Adamczyk

L. Fulek

M. Przybycien

R. Sikora

I. Alekseev

D.N. Svirida

I.G. Bordyuzhin

D.G. Underwood

H.M. Spinka

M. Zurek

Egypt

A. Hamed

F.M. Fawzi

M.S. Abdallah

J. Jia

A. Jentsch

A. Kiselev

A. Lebedev

A. Ogawa

A.H. Tang

A.S. Nunes

B.S. Page

E.C. Aschenauer

F. Videbæk

G. Van Buren

H.W. Ke

J. Adam

J. Lauret

J.C. Dunlop

J.C. Webb

J.D. Brandenburg

J.H. Lee

J.M. Landgraf

K. Kauder

K. Yip

L. Didenko

L. Ruan

O. Eyser

P. Sorensen

P. Tribedy

P.V. Shanmuganathan

R. Ma

R. Pak

R.S. Longacre

S. Fazio

T. Ljubicic

T. Ullrich

W. Christie

W. Guryn

W.B. Schmidke

Erratum: Disappearance of partonic collectivity in √ <italic>s</italic> <inf>NN</inf> = 3 GeV Au+Au collisions at RHIC [Phys. Lett. B 827, 137003 (2022)]