We investigate a novel class of boosted-object signatures at the LHC, where a high-<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>p</mi><mi mathvariant="normal">T</mi></msub></math> fat jet contains an identifiable hadron or quarkonium state originating from rare or semiexclusive decays. Unlike conventional boosted jet studies, which focus on multiprong partonic substructure, our approach probes hybrid configurations such as <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>W</mi><mo>±</mo></msup><mo stretchy="false">→</mo><msup><mi>π</mi><mo>±</mo></msup><mi>γ</mi></math>, where a localized hadronic or quarkonium signal is embedded within a collimated jet. By fine-tuning the signature-oriented, pretrained Sophon artificial intelligence model optimized for large-radius jets, and combining it with an event-level boosted decision tree and a soft-drop-mass shape fit, we obtain an expected 95% confidence level upper limit of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">B</mi><mo stretchy="false">(</mo><msup><mi>W</mi><mo>±</mo></msup><mo stretchy="false">→</mo><msup><mi>π</mi><mo>±</mo></msup><mi>γ</mi><mo stretchy="false">)</mo><mo>&lt;</mo><mn>2.78</mn><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>5</mn></mrow></msup></math> for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>450</mn><mtext> </mtext><mtext> </mtext><msup><mi>fb</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup></math> in our nominal setup. This study serves as a first proof-of-principle demonstration of the hadron-in-fat-jet paradigm; substantial gains in sensitivity are expected from improved trigger strategies, additional production channels, and dedicated taggers, while the methodology itself is broadly applicable to a wide range of rare Standard Model processes and searches for light or exotic resonances at present and future collider experiments.

China

Linrui Chen

Tianyi Yang

Zixun Kou

Zijian Wang

Youpeng Wu

Leyun Gao

Qiang Li

Hadron-in-fat-jet AI tagging to detect rare decays such as <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>W</mi><mo>±</mo></msup><mo stretchy="false">→</mo><msup><mi>π</mi><mo>±</mo></msup><mi>γ</mi></math>

Right-handed lepton flavor mixing in the left-right symmetric model directly affects the production and decay of heavy Majorana neutrinos <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>N</mi><mi>R</mi></msub></math>, yet its impact on collider searches remains less explored. Using a deep neural network, we analyze the Keung-Senjanović process <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>p</mi><mi>p</mi><mo stretchy="false">→</mo><msub><mrow><mi>W</mi></mrow><mrow><mi>R</mi></mrow></msub><mo stretchy="false">→</mo><msub><mrow><mo>ℓ</mo></mrow><mrow><mi>α</mi></mrow></msub><msub><mrow><mi>N</mi></mrow><mrow><mi>R</mi></mrow></msub><mo stretchy="false">→</mo><msub><mrow><mo>ℓ</mo></mrow><mrow><mi>α</mi></mrow></msub><msub><mrow><mo>ℓ</mo></mrow><mrow><mi>β</mi></mrow></msub><mi>j</mi><mi>j</mi></mrow></math> with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mo>ℓ</mo></mrow><mrow><mi>α</mi><mo>,</mo><mi>β</mi></mrow></msub><mo>=</mo><mi>e</mi></mrow></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>μ</mi></mrow></math> at LHC Run 2 and the HL-LHC, considering both same-sign and opposite-sign dilepton channels. We adopt three benchmark mixing scenarios: unmixed, maximal mixing, and Pontecorvo-Maki-Nakagawa-Sakata (PMNS)-like. In the unmixed scenario, the deep neural network improves the expected significance over the cut-based analyses performed by ATLAS, leading to stronger expected sensitivities. For the combined <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>ℓ</mo><mo>ℓ</mo></math> analysis, the HL-LHC is projected to reach <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>m</mi><msub><mi>W</mi><mi>R</mi></msub></msub></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>m</mi><msub><mi>N</mi><mi>R</mi></msub></msub></math> values up to 6.7 (6.3) and 4.4 (4.1) TeV, respectively, under maximal (PMNS-like) mixing. For representative mass benchmarks, our analysis indicates that LHC Run 2 can test a significant portion of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mo stretchy="false">|</mo><msub><mrow><mi>V</mi></mrow><mrow><mi>e</mi><mn>1</mn></mrow></msub><mo stretchy="false">|</mo><mtext>−</mtext><mo stretchy="false">|</mo><msub><mrow><mi>V</mi></mrow><mrow><mi>μ</mi><mn>1</mn></mrow></msub><mo stretchy="false">|</mo></mrow></math> plane, and the HL-LHC could probe even smaller mixing values, including the corresponding benchmark points for both the maximal and PMNS-like patterns. Finally, we investigate complementarities with low-energy charged lepton flavor-violation processes, where future searches can overlap with or exceed the LHC reach.

Jin-Man Cai

Gang Li

Probing lepton flavor mixing in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>W</mi><mi>R</mi></msub></math> searches with machine learning at the LHC

We test clipping effective field theory (EFT) simulations as a method of ensuring EFT validity. The procedure imposes that, at the level of the simulation, the invariant mass of a $$W^+W^-$$ pair $$M_{WW}$$ is less than the new physics scale $$\Lambda $$ . We compare this to two other methods, comparison bin by bin of dimension-6 and dimension-8 squared contributions and implementing a cut on data. We find that setting $$M_{WW} < \Lambda $$ is not strict enough to ensure that the hierarchy of EFT operators is respected for dimension-6 and dimension-8 contributions. We also show that, even when using a stricter cut on $$M_{WW}$$ , due to different correlations between $$M_{WW}$$ and $$M_{e\mu }$$ at different EFT orders, the bins in $$M_{e\mu }$$ (the invariant mass of the leptons originating from $\textit{W}$ decays) used in an EFT fit may not truly be in the regime of EFT validity when performing a dimension-6 fit with $$M_{WW} < \Lambda $$ . We also explore the correlations of three transverse mass observables: $$M_{T1}, M_{T2}$$ and $$M_{T3}$$ , finding that $$M_{T1}$$ and $$M_{T3}$$ follow the $$M_{WW}$$ distribution more closely than $$M_{e\mu }$$ . We present sensitivity studies using both the $$M_{T3}$$ distribution and $$M_{e\mu }$$ distribution. We test implementing an experimental cut on $$M_{T3}$$ in place of clipping the EFT simulation at $$M_{WW} < \Lambda $$ . We finally comment that adding $$M_{WW} < \Lambda $$ cuts only to the EFT simulation could be interpreted as modifying the SMEFT expansion by a form factor and could therefore impact the model independence of EFT fits under this procedure.

United Kingdom

Daniel Gillies

Andrea Banfi

United States

Adam Martin

Probing EFT breakdown in the tails of $$W^+ W^-$$ observables

A precision measurement of the muon charge asymmetry from <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>W</mi></math>-boson decays in proton-proton 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> is presented. The analysis utilizes data corresponding to an integrated luminosity of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>5.1</mn><mtext> </mtext><mtext> </mtext><msup><mrow><mi>fb</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math>, recorded by the LHCb detector during 2016, 2017, and 2018. The asymmetry is measured for muons with transverse momentum between 25 and 55 GeV and pseudorapidity between 2.0 and 4.5. This result represents the most precise determination of the muon charge asymmetry in the forward region to date, exhibiting excellent agreement with next-to-next-to-leading-order predictions in perturbative quantum chromodynamics. The measured asymmetries are corrected for experimental efficiencies, resolution, and final-state photon radiation.

Netherlands

R. Aaij

M. Abdelfatah

A.S.W. Abdelmotteleb

Switzerland

C. Abellan Beteta

F. Abudinén

T. Ackernley

A.A. Adefisoye

Spain

B. Adeva

M. Adinolfi

P. Adlarson

France

C. Agapopoulou

C.A. Aidala

Z. Ajaltouni

S. Akar

K. Akiba

Italy

P. Albicocco

Germany

J. Albrecht

R. Aleksiejunas

CERN

F. Alessio

P. Alvarez Cartelle

R. Amalric

Brazil

S. Amato

J.L. Amey

Y. Amhis

L. An

L. Anderlini

M. Andersson

P. Andreola

M. Andreotti

S. Andres Estrada

A. Anelli

D. Ao

C. Arata

F. Archilli

Z. Areg

M. Argenton

Costa Rica

S. Arguedas Cuendis

L. Arnone

M. Artuso

E. Aslanides

R. Ataíde Da Silva

M. Atzeni

B. Audurier

J.A. Authier

D. Bacher

I. Bachiller Perea

S. Bachmann

M. Bachmayer

J.J. Back

Z.B. Bai

P. Baladron Rodriguez

V. Balagura

A. Balboni

W. Baldini

Z. Baldwin

L. Balzani

H. Bao

J. Baptista de Souza Leite

C. Barbero Pretel

M. Barbetti

I.R. Barbosa

R.J. Barlow

M. Barnyakov

S. Barsuk

W. Barter

J. Bartz

Poland

S. Bashir

B. Batsukh

P.B. Battista

A. Bavarchee

A. Bay

A. Beck

M. Becker

F. Bedeschi

I.B. Bediaga

N.A. Behling

S. Belin

A. Bellavista

I. Belov

I. Belyaev

G. Benane

G. Bencivenni

E. Ben-Haim

R. Bernet

A. Bertolin

F. Betti

J. Bex

O. Bezshyyko

S. Bhattacharya

M.S. Bieker

N.V. Biesuz

A. Biolchini

M. Birch

F.C.R. Bishop

A. Bitadze

A. Bizzeti

T. Blake

F. Blanc

J.E. Blank

S. Blusk

Precision Measurement of the Muon Charge Asymmetry from <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>W</mi></math>-Boson Decays 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"><mrow><msqrt><mrow><mi>s</mi></mrow></msqrt><mo>=</mo><mn>13</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></mrow></math> in the Forward Region

A precision measurement of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>W</mi></math>-boson production cross section is performed using the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>W</mi><mo stretchy="false">→</mo><mi>μ</mi><mi>ν</mi></math> decay channel, based on a sample of proton-proton collision data collected by the LHCb experiment 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> and corresponding to an integrated luminosity of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>5.1</mn><mtext> </mtext><mtext> </mtext><msup><mi>fb</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup></math>. The cross section is measured for muons with transverse momentum between 25 and 55 GeV and pseudorapidity between 2.0 and 4.5. The total production cross sections of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>W</mi></math> bosons are measured to be <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>σ</mi></mrow><mrow><msup><mrow><mi>W</mi></mrow><mrow><mo>+</mo></mrow></msup><mo stretchy="false">→</mo><msup><mrow><mi>μ</mi></mrow><mrow><mo>+</mo></mrow></msup><mi>ν</mi></mrow></msub><mo>=</mo><mn>1754.2</mn><mo>±</mo><mn>1.5</mn><mo>±</mo><mn>11.8</mn><mo>±</mo><mn>35.1</mn><mtext> </mtext><mtext> </mtext><mi>pb</mi></mrow></math> <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>σ</mi></mrow><mrow><msup><mrow><mi>W</mi></mrow><mrow><mo>−</mo></mrow></msup><mo stretchy="false">→</mo><msup><mrow><mi>μ</mi></mrow><mrow><mo>−</mo></mrow></msup><mover accent="true"><mrow><mi>ν</mi></mrow><mrow><mo stretchy="false">¯</mo></mrow></mover></mrow></msub><mo>=</mo><mn>1178.1</mn><mo>±</mo><mn>1.3</mn><mo>±</mo><mn>9.7</mn><mo>±</mo><mn>23.6</mn><mtext> </mtext><mtext> </mtext><mi>pb</mi></mrow></math> where uncertainties are statistical, systematic, and due to the luminosity determination, respectively. Differential distributions <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">d</mi><msub><mi>σ</mi><mrow><msup><mi>W</mi><mo>±</mo></msup><mo stretchy="false">→</mo><msup><mi>μ</mi><mo>±</mo></msup><mi>ν</mi></mrow></msub><mo>/</mo><mi mathvariant="normal">d</mi><msup><mi>η</mi><msup><mi>μ</mi><mo>±</mo></msup></msup></math> are also presented. The total and differential cross sections are in good agreement with theoretical predictions at next-to-next-to-leading order in perturbative quantum chromodynamics. This measurement is significantly more precise than previous results in this kinematic regime.

Measurement of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>W</mi></math>-boson production cross sections 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 the forward region

We revisit the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi><mi>P</mi></math>-odd form factor in the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>H</mi><mi>W</mi><mi>W</mi></math> vertex within the Standard Model, which is induced only at the one-loop level when one of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>W</mi></math> bosons is off-shell. To the best of our knowledge, the numerical evaluation of this form factor is presented for the first time. The relevant contributions from quark loops are of order <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mn>10</mn><mrow><mo>−</mo><mn>5</mn></mrow></msup></math>, well below the current experimental sensitivity. The phenomenological implications are studied through asymmetries in unpolarized and polarized observables in three-body decays.

Mexico

A.I. Hernández-Juárez

G. Tavares-Velasco

J. Martínez-Ramón

<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi><mi>P</mi></math>-odd form factor in the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>H</mi><mi>W</mi><mi>W</mi></math> vertex

Using bootstrap methods, we provide evidence for the existence of a non-linear W-algebra, denoted $$ {\mathcal{W}}_{\infty}^{\mathrm{s},\mathrm{s}} $$ , which contains the $\textit{small}$ $$ \mathcal{N} $$ = 4 super Virasoro algebra and features an infinite tower of additional generators, organized in $\textit{short}$ supersymmetry multiplets. The algebra $$ {\mathcal{W}}_{\infty}^{\mathrm{s},\mathrm{s}} $$ has one free parameter, its central charge $\textit{c}$. We claim that the simple quotient of $$ {\mathcal{W}}_{\infty}^{\mathrm{s},\mathrm{s}} $$ for $\textit{c}$ = –3($\textit{N}$ – 1) is isomorphic to the vertex operator algebra associated to 4d $$ \mathcal{N} $$ = 4 $$ \mathfrak{su}(N) $$ super Yang-Mills theory. We define a filtration in $$ {\mathcal{W}}_{\infty}^{\mathrm{s},\mathrm{s}} $$ and provide evidence that it reproduces the $\textit{R}$-filtration, which is crucial to extract 4d SCFT data from the vertex operator algebra. Finally, we present explicit formulae for all the (anti)commutators of the wedge algebra of $$ {\mathcal{W}}_{\infty}^{\mathrm{s},\mathrm{s}} $$ .

Federico Bonetti

Carlo Meneghelli

A universal W-algebra for $$ \mathcal{N} $$ = 4 super Yang-Mills

We study the process <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>W</mi><mo>+</mo></msup><msup><mi>W</mi><mo>−</mo></msup></math> with the aim of estimating the prospects for observing heavy neutrino contributions at future <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>-colliders. In this work, we consider two implementations of heavy-light neutrino mixing: a linearized mixing approximation applied in popular models and an exact unitary mixing scheme. We conclude that the approximate realization leads to physically incorrect results for this process, while exact unitary mixing provides some signatures that can be experimentally checked.

Russia

G.A. Chachava

S.I. Godunov

Importance of unitarity in the search for heavy neutrinos 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>W</mi><mo>+</mo></msup><msup><mi>W</mi><mo>−</mo></msup></math>

In this study, we develop a framework for producing exotic muonic kaon atoms ( $ K\mu $ ) in semileptonic $ D^{0} $ decays using an effective weak Hamiltonian, a helicity-based treatment of leptonic current, and a nonrelativistic bound-state projection. The resulting branching ratio $ BR(D^{0} \to(K\mu )\nu_{\mu})=2.29\times10^{-10} $ is implemented in a ROOT-based code to estimate yields at a relativistic heavy-ion collider (RHIC), large hadron collider (LHC), and super tau-charm facility (STCF). We demonstrate quantitatively that $ K\mu $ atoms, which are also produced through coalescence in the quark–gluon plasma (QGP), offer a sensitive probe of low-momentum primordial muons and early-time electromagnetic radiation, acting as complementary constraints in an otherwise unexplored phase space for thermal dilepton and photon emission. Newly estimated dissociation cross-sections in detector material indicate that secondary-vertex reconstruction should be experimentally feasible, enabling the clean experimental identification of atoms. Projected yields from QGP coalescence in LHC and RHIC heavy-ion collisions and from $ D^{0} $ decays in LHC high-luminosity $ p+p $ collisions indicate that the first observation of $ K\mu $ atoms is within reach.

Xiaofeng Wang

Zebo Tang

Zhangbu Xu

Chi Yang

Wangmei Zha

Yifei Zhang

Production of muonic kaon atoms at high-energy colliders * This work was supported in part by the National Natural Science Foundation of China (12361141827, 12422510), and by the Office of Nuclear Physics within the U.S. Department of Energy Office of Science (DE-FG02-89ER40531). The National Key Research and Development Program of China (2022YFA1604900). W. Zha acknowledges support from the Anhui Provincial Natural Science Foundation (2508085JX002), the Youth Innovation Promotion Association of the Chinese Academy of Sciences, and the Chinese Academy of Sciences (YSBR088)

We study the light asymptotic limit of the one-point torus conformal block in $\textit{A}$ Toda field theory. Through the AGT correspondence, this problem can be translated into the computation of the instanton partition function of four-dimensional $$ \mathcal{N} $$ = 2 U($\textit{n}$) supersymmetric Yang-Mills theory, which we then examine in the limit $\textit{b}$ → 0 at fixed conformal dimensions. We show that, in this regime, the instanton sum simplifies drastically: for each Young diagram, only boxes with specific arm lengths contribute to the bifundamental factors. Exploiting this property, we derive an explicit representation for the light one-point torus $\textit{W}$ conformal block valid for arbitrary $\textit{n}$ ≥ 2.

Armenia

Armen Poghosyan

Hasmik Poghosyan

The $\textit{W}$ $\textit{n}$ light one-point torus conformal block