We present the results of a search for the charged-lepton-flavor violating decays $\textit{B}$ → $\textit{K}$ $\textit{τ}$ $\textit{ℓ}$ , where $\textit{ℓ}$ is either an electron or a muon. The results are based on 365 fb and 711 fb datasets collected with the Belle II and Belle detectors, respectively. We use an exclusive hadronic $\textit{B}$-tagging technique, and search for a signal decay in the system recoiling against a fully reconstructed $\textit{B}$ meson. We find no evidence for $\textit{B}$ → $\textit{K}$ $\textit{τ}$ $\textit{ℓ}$ decays and set upper limits on the branching fractions in the range of (2.9–6.4)×10 at 90% confidence level.

I. Adachi

Y. Ahn

H. Aihara

N. Akopov

S. Alghamdi

M. Alhakami

A. Aloisio

K. Amos

M. Angelsmark

N. Anh Ky

C. Antonioli

D. Asner

H. Atmacan

V. Aushev

M. Aversano

R. Ayad

V. Babu

H. Bae

N. Baghel

S. Bahinipati

P. Bambade

Sw. Banerjee

S. Bansal

M. Barrett

J. Baudot

A. Baur

A. Beaubien

F. Becherer

J. Becker

J. Bennett

F. Bernlochner

V. Bertacchi

M. Bertemes

E. Bertholet

M. Bessner

S. Bettarini

B. Bhuyan

F. Bianchi

T. Bilka

D. Biswas

A. Bobrov

D. Bodrov

J. Borah

A. Boschetti

A. Bozek

M. Bračko

P. Branchini

R. Briere

T. Browder

A. Budano

S. Bussino

M. Campajola

L. Cao

G. Casarosa

C. Cecchi

M.C. Chang

P. Cheema

B. Cheon

K. Chilikin

J. Chin

H.E. Cho

K. Cho

S.J. Cho

S.K. Choi

S. Choudhury

I. Consigny

L. Corona

J. Cui

E. De La Cruz-Burelo

S. De La Motte

G. Marino

G. Pietro

R. Sangro

M. Destefanis

A. Canto

J. Dingfelder

Z. Doležal

I. Domínguez Jiménez

T. Dong

X. Dong

M. Dorigo

G. Dujany

P. Ecker

D. Epifanov

R. Farkas

P. Feichtinger

T. Ferber

T. Fillinger

C. Finck

G. Finocchiaro

F. Forti

A. Frey

B. Fulsom

A. Gale

E. Ganiev

M. Garcia-Hernandez

R. Garg

G. Gaudino

V. Gaur

V. Gautam

Search for lepton flavor-violating decay modes $\textit{B}$

We continue the study of 2D gravity—“matrix model” duality on the example of a <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo stretchy="false">(</mo><mn>2</mn><mo>,</mo><mn>2</mn><mi>p</mi><mo>+</mo><mn>1</mn><mo stretchy="false">)</mo></math> minimal string. We propose a reformulation of the duality, related to a more conventional one by “<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>x</mi><mtext>−</mtext><mi>y</mi></mrow></math> swap” in the language of topological recursion. This formulation elucidates some conceptual and technical difficulties in the dictionary of the duality and relation to other examples. In particular, it allows to circumvent the necessity to use “resonance transformations,” which were previously introduced to match the world sheet and “matrix model” correlators, and the expressions for minimal string amplitudes in this approach are reminiscent of the ones obtained recently for “complex Liouville string” theory. Using this new approach, we also formulate a conjecture on how one can compute amplitudes with operators other than tachyons in the dual theory.

Russia

Aleksandr Artemev

<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>x</mi><mtext>−</mtext><mi>y</mi></mrow></math> swap for a (2, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>2</mn><mi>p</mi><mo>+</mo><mn>1</mn></mrow></math>) minimal string

This paper presents a novel tagging technique to measure the beauty-quark partial decay-width ratio $$R_b$$ and its forward–backward asymmetry $$A_{\textrm{FB}}^b$$ at the FCC-ee, using $$\mathcal {O}(10^{12})$$ $\textit{Z}$-boson decays. The method is based on the exclusive reconstruction of a selected list of $\textit{b}$-hadron decay modes in $$Z\rightarrow b\bar{b}$$ events at the $\textit{Z}$ pole, which can provide the flavour and possibly the charge of the hemisphere. This approach effectively eliminates the contamination from light-quark physics events and reduces the leading systematic uncertainties arising from background contamination, tagging-efficiency correlations, and gluon-radiation corrections by exploiting the geometric and kinematic properties of beauty hadrons. This results in a total relative uncertainty of the order of 0.01 % for both observables. Furthermore, this precision allows to obtain a commensurate precision on the weak mixing angle $$\sin ^2(\theta _\text {W}^{\text {eff}})$$ compared to the muon forward–backward asymmetry on the order of 0.002 %.

Germany

France

Lars Röhrig

Kevin Kröninger

Romain Madar

Stéphane Monteil

Italy

Fabrizio Palla

Switzerland

Emmanuel Perez

Measuring $$A_\textrm{FB}^b$$ and $$R_b$$ with exclusive $\textit{b}$-hadron decays at the FCC-ee

In this study, we present a comprehensive analysis of decay constants and chiral-even and chiral-odd distribution amplitudes (DAs) up to twist 4 for the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>ρ</mi></math> meson in the standard light-front quark model (LFQM) based on the Bakamjian-Thomas (BT) construction. For the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>ρ</mi></math> meson, which possesses both longitudinal (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>h</mi><mo>=</mo><mn>0</mn></mrow></math>) and transverse <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo stretchy="false">(</mo><mi>h</mi><mo>=</mo><mo>±</mo><mn>1</mn><mo stretchy="false">)</mo></math> polarizations, two types of decay constants, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>f</mi><mi>ρ</mi><mo stretchy="false">∥</mo></msubsup></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>f</mi><mi>ρ</mi><mo>⊥</mo></msubsup></math>, arises accordingly. We demonstrate that these decay constants can be self-consistently extracted from both local (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>z</mi><mi>μ</mi></msup><mo>=</mo><mn>0</mn></math>) and nonlocal (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>z</mi><mi>μ</mi></msup><mo>≠</mo><mn>0</mn></math>) matrix elements <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo stretchy="false">⟨</mo><mn>0</mn><mo stretchy="false">|</mo><mover accent="true"><mi>q</mi><mo stretchy="false">¯</mo></mover><mo stretchy="false">(</mo><mi>z</mi><mo stretchy="false">)</mo><mi mathvariant="normal">Γ</mi><mi>q</mi><mo stretchy="false">(</mo><mo>−</mo><mi>z</mi><mo stretchy="false">)</mo><mo stretchy="false">|</mo><mi>ρ</mi><mo stretchy="false">(</mo><mi>P</mi><mo>,</mo><mi>h</mi><mo stretchy="false">)</mo><mo stretchy="false">⟩</mo></math>, with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="normal">Γ</mi><mo>=</mo><mo stretchy="false">(</mo><msup><mrow><mi>γ</mi></mrow><mrow><mi>μ</mi></mrow></msup><mo>,</mo><msup><mrow><mi>σ</mi></mrow><mrow><mi>μ</mi><mi>ν</mi></mrow></msup><mo>,</mo><msup><mrow><mi>γ</mi></mrow><mrow><mi>μ</mi></mrow></msup><msub><mrow><mi>γ</mi></mrow><mn>5</mn></msub><mo>,</mo><mn mathvariant="bold">1</mn><mo stretchy="false">)</mo></mrow></math>, in a manner independent of current components, polarizations, and reference frames. In particular, we emphasize the role of nonlocal matrix elements involving axial-vector and scalar currents, where mixing between <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>f</mi><mi>ρ</mi><mo stretchy="false">∥</mo></msubsup></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>f</mi><mi>ρ</mi><mo>⊥</mo></msubsup></math> occurs. We show that this mixing is consistently resolved through the BT construction, ensuring the proper extraction of these decay constants. Additionally, we investigate the structure of chiral-even DAs (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>ϕ</mi><mrow><mn>2</mn><mo>;</mo><mi mathvariant="normal">V</mi></mrow><mo stretchy="false">∥</mo></msubsup><mo>,</mo><msubsup><mi>ϕ</mi><mrow><mn>3</mn><mo>;</mo><mi mathvariant="normal">V</mi></mrow><mo stretchy="false">∥</mo></msubsup><mo>,</mo><msubsup><mi>ψ</mi><mrow><mn>3</mn><mo>;</mo><mi mathvariant="normal">A</mi></mrow><mo>⊥</mo></msubsup><mo>,</mo><msubsup><mi>ϕ</mi><mrow><mn>4</mn><mo>;</mo><mi mathvariant="normal">V</mi></mrow><mo stretchy="false">∥</mo></msubsup></math>) and chiral-odd DAs (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>ϕ</mi><mrow><mn>2</mn><mo>;</mo><mi mathvariant="normal">T</mi></mrow><mo>⊥</mo></msubsup><mo>,</mo><msubsup><mi>ϕ</mi><mrow><mn>3</mn><mo>;</mo><mi mathvariant="normal">T</mi></mrow><mo>⊥</mo></msubsup><mo>,</mo><msubsup><mi>ψ</mi><mrow><mn>3</mn><mo>;</mo><mi mathvariant="normal">S</mi></mrow><mo stretchy="false">∥</mo></msubsup><mo>,</mo><msubsup><mi>ϕ</mi><mrow><mn>4</mn><mo>;</mo><mi mathvariant="normal">T</mi></mrow><mo>⊥</mo></msubsup></math>) beyond leading twists, and present their corresponding <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>ξ</mi></math>-moments and Gegenbauer moments. These results provide deeper insight into the nonperturbative structure of vector mesons and demonstrate the robustness and self-consistency of the LFQM based on the BT framework.

Japan

Ahmad Jafar Arifi

South Korea

Ho-Meoyng Choi

United States

Chueng-Ryong Ji

Beyond leading twist: <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>ρ</mi></math> meson decay constants and distribution amplitudes in a self-consistent light-front quark model

We construct examples of renormalizable Carrollian theories with finite effective central charge and non-trivial dynamics. These include critical points that are not scale-invariant but rather exhibit hyperscaling violation. All of our examples are mildly non-Lagrangian, in that they arise from suitable $\textit{N}$ → 0 limits of Carrollian theories with $\textit{N}$-component fields, including limits of Carrollian vector models and non-abelian gauge theories. We discuss implications for flat space holography, highlighting challenges in realizing Carrollian duals to gravitational theories.

Jordan Cotler

Canada

Prateksh Dhivakar

Kristan Jensen

A finite Carrollian critical point

We present a search for new scalar bosons predicted by the Inert Doublet Model at an $$e^+e^-$$ machine with centre-of-mass energies $$\sqrt{s} $$ of 240 and 365 $$\text {G}\text {eV}$$ . Within this model, four additional scalar bosons ( $$H,\, A,\, H^+$$ and $$H^-$$ ) are predicted. Due to an additional symmetry, the lightest new scalar, here chosen to be $\textit{H}$, is stable and provides an adequate dark matter candidate. The search for pair production of the new scalars is investigated in final states with two electrons or two muons, in the context of the future circular collider proposal, FCC-ee. Building on previous studies in the context of the CLIC proposal, this analysis extends the search to detector-level objects, using a parametric neural network to enhance the signal contributions over the Standard Model backgrounds, and sets projected exclusion and discovery contours in the $$M_A-M_H$$ vs. $$M_H$$ plane. With a total integrated luminosity of 10.8 (2.7) $$\,\hbox {ab}^{-1}$$ for $$\sqrt{s} =$$ 240 (365) $$\text {G}\text {eV}$$ , the discovery reach for the model goes up to $$M_H$$ $$= 108\,(157)\,\text {G}\text {eV}$$ for $$M_A-M_H$$ $$=15$$ $$\text {G}\text {eV}$$ at $$\sqrt{s} =$$ 240 (365) $$\text {G}\text {eV}$$ . For exclusion, almost the entire phase-space available in the $$M_A-M_H$$ vs. $$M_H$$ plane is expected to be ruled out at 95% CL, reaching up to $$M_H$$ $$=110\,(165)$$ $$\text {G}\text {eV}$$ .

United Kingdom

Anubha Bal

Edward Curtis

Anne-Marie Magnan

Benedikt Maier

Croatia

Tania Robens

Nicholas Wardle

Search for additional scalar bosons within the Inert Doublet Model in a final state with two leptons at the FCC-ee

We propose a generalized Riemann-Hilbert-Birkhoff decomposition that expands the standard integrable hierarchy formalism in two fundamental ways: it allows for integer powers of Lax matrix components in the flow equations to be increased as compared to conventional models, and it incorporates constant non-zero vacuum (background) solutions.

H. Aratyn

Brazil

C.P. Constantinidis

J.F. Gomes

T.C. Santiago

A.H. Zimerman

Generalized Riemann-Hilbert-Birkhoff decomposition and a new class of higher grading integrable hierarchies

The Large Hadron Collider precision measurement of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>h</mi></mrow><mrow><mn>125</mn></mrow></msub></mrow></math> properties suggests that a misaligned two-Higgs-doublet model (2HDM) type I is preferred among other types of the model. In this analysis, a lepton collider potential for charged Higgs boson observation is evaluated and compared with HL-LHC expectations. We focus on <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi>H</mi></mrow><mrow><mo>±</mo></mrow></msup><mo stretchy="false">→</mo><msup><mrow><mi>W</mi></mrow><mrow><mo>±</mo></mrow></msup><msub><mrow><mi>h</mi></mrow><mrow><mn>125</mn></mrow></msub></mrow></math> decay which is exclusively activated in misaligned scenario. An event analysis including fast detector simulation is performed, and it is shown that some parts of the parameter space which are out of HL-LHC reach can be probed by a high-energy lepton collider with signal significance exceeding <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>2</mn><mi>σ</mi></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>5</mn><mi>σ</mi></math> for exclusion or discovery. The region with highest sensitivity is in the middle range charged Higgs boson mass, i.e., <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>350</mn><mo>&lt;</mo><msub><mi>m</mi><msup><mi>H</mi><mo>±</mo></msup></msub><mo>&lt;</mo><mn>450</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>tan</mi><mi>β</mi><mo>≳</mo><mn>4</mn></math> at nonzero <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>cos</mi><mo stretchy="false">(</mo><mi>β</mi><mo>−</mo><mi>α</mi><mo stretchy="false">)</mo></math> values.

Iran

Majid Hashemi

Omid Seify

Observability of 2HDM charged Higgs boson in a misaligned scenario

We study a scale invariant inverse seesaw model that radiatively generates the electroweak scale, the Standard Model (SM) neutrino masses, and stabilizes the electroweak vacuum. Previous studies have noted that the SM Higgs potential and the electroweak scale can be radiatively generated via the minimal seesaw mechanism. This scenario, called the “neutrino option,” was UV completed by a scale invariant framework. However, these models predict singlet neutrino and scalar masses at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mn>10</mn><mn>7</mn></msup><mi>–</mi><msup><mn>10</mn><mn>9</mn></msup><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>, beyond any experimental reach and leave the electroweak vacuum metastable/unstable at high energies. In this work, we propose modifications to this framework that lower the singlet neutrino masses to experimentally accessible scales through an inverse seesaw mechanism, while fully stabilizing the electroweak vacuum with an additional singlet scalar. The possibility of generating the observed baryon asymmetry of the Universe via leptogenesis is also explored.

Aqeel Ahmed

Juan P. Garcés

Manfred Lindner

Radiative symmetry breaking with a scale invariant seesaw mechanism

A search for a pseudoscalar $\textit{a}$ produced in association with a top-quark pair, or in association with a single top quark plus a $\textit{W}$ boson, with the pseudoscalar decaying into $\textit{b}$-quarks ( $$a\rightarrow b\bar{b}$$ ), is performed using the full Run 2 data sample using a dileptonic decay mode signature. The search covers pseudoscalar boson masses between 12 and 100 GeV and involves both the kinematic regime where the decay products of the pseudoscalar are reconstructed as two standard $\textit{b}$-tagged small-radius jets, or merged into a large-radius jet due to its Lorentz boost. No significant excess relative to expectations is observed. Assuming a branching ratio $$\text {BR}(a\rightarrow b\bar{b})=100\% $$ , the range of pseudoscalar masses between 50 and 80 GeV is excluded at 95% confidence level for a coupling of the pseudoscalar to the top quark of 0.5, while a coupling of 1.0 is excluded at 95% confidence level for the masses considered, with the coupling defined as the strength modifier of the Standard Model Yukawa coupling.

G. Aad

Norway

E. Aakvaag

B. Abbott

United Arab Emirates

S. Abdelhameed

K. Abeling

N.J. Abicht

S. Abidi

M. Aboelela

Morocco

A. Aboulhorma

Israel

H. Abramowicz

Y. Abulaiti

B. Acharya

A. Ackermann

C. Bourdarios

Poland

L. Adamczyk

S. Addepalli

M. Addison

J. Adelman

Türkiye

A. Adiguzel

T. Adye

A. Affolder

Y. Afik

Spain

M. Agaras

A. Aggarwal

Romania

C. Agheorghiesei

Azerbaijan

F. Ahmadov

S. Ahuja

China

X. Ai

G. Aielli

A. Aikot

Search for a new pseudoscalar decaying into a pair of bottom and antibottom quarks in top-associated production in $$\sqrt{s}=13$$ TeV proton–proton collisions with the ATLAS detector