$\textit{U}$-spin symmetry, which reflects the symmetry between the down-type $\textit{d}$ and $\textit{s}$ quarks, is a powerful tool for analyzing heavy hadron weak decays. Motivated by recent experimental achievements in the bottom baryon sector, we study the $\textit{U}$-spin sum rules for bottom baryon decays. The effective Hamiltonian for $\textit{b}$ quark decay is zero under the $\textit{U}$-spin lowering operators $$U_-^n$$ , permitting us to derive $\textit{U}$-spin sum rules involving only the $$b\rightarrow d$$ transition or $$b\rightarrow s$$ transition. Moreover, a new operator, $$S_b=U_++rU_3-r^2U_-$$ , is proposed to generate $\textit{U}$-spin sum rules involving both the $$b\rightarrow d$$ and $$b\rightarrow s$$ transitions. The proof that the effective Hamiltonian for $\textit{b}$ quark decay is zero under $$U_-^n$$ and $$S_b$$ is presented. The master formulas for generating $\textit{U}$-spin sum rules for the two-body decays of bottom baryons involving $$b\rightarrow c\overline{c}d/s$$ , $$b\rightarrow c\overline{u}d/s$$ , $$b\rightarrow u\overline{u}d/s$$ , and $$b\rightarrow u\overline{c}d/s$$ transitions are derived. Numerous $\textit{U}$-spin sum rules for the two-body decays of bottom baryons are obtained through these master formulas, which provide hints for new decay modes and enable the extraction of dynamical information. As a phenomenological analysis, some branching fractions are predicted according to $\textit{U}$-spin symmetry. Several rate and decay parameter sum rules beyond the $\textit{U}$-spin limit are found, providing a more precise test of flavor symmetry in the bottom baryon sector. Moreover, some $\textit{CP}$ asymmetry relations for $\textit{U}$-spin conjugate pairs in heavy baryon decays are derived for the first time by taking partial-wave amplitudes into account.

China

Si-Jia Wen

Wei-Chen Fu

Di Wang

$\textit{U}$-spin sum rules for two-body decays of bottom baryons

We discuss physics-informed renormalization group flows (PIRGs) for general operators. We show that operator PIRGs provide comprehensive access to all correlation functions of the quantum field theory under investigation. The operator PIRGs can be seen as a completion of the PIRG approach, whose qualitative computational simplification and structural insights are now fully accessible for general applications. The potential of this setup is assessed within a simple analytic example of the zero-dimensional <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>ϕ</mi><mn>4</mn></msup></math>-theory, for which the generating functions of the fundamental field are computed within a vertex expansion, using the one- to ten-point functions.

Friederike Ihssen

Jan M. Pawlowski

Physics-informed operator flows and observables

I propose a novel laboratory search for dark photons based on radiation-safety monitoring at synchrotron radiation facilities, including NanoTerasu, SPring-8, the KEK Photon Factory, and the European Synchrotron Radiation Facility. Dark photons can be produced parasitically in undulators or via photon-mirror interactions and subsequently traverse optical systems and shielding. Taking into account quantum effects and the internal structure of undulators, mirrors, and detectors, I show that even a simple Geiger-Müller counter routinely used for radiation-safety monitoring can detect such dark photons outside the shielding and set the strongest purely laboratory limits on the kinetic mixing parameter, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>χ</mi><mo>≲</mo><mn>5</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>6</mn></mrow></msup></mrow></math>, in the mass range 1–50 eV. Since radiation safety is strictly regulated, the resulting limits provide robust and realistic constraints.

Wen Yin

Novel Limits on Dark Photon Mixing from Radiation Safety

Nanohertz gravitational waves (GWs) from supermassive binary black holes (SMBBHs), detectable via pulsar timing arrays (PTAs), offer a novel avenue to constrain dark energy. Based on cosmological simulations and semi-analytic galaxy formation models, this study explores the detectability of individual nanohertz SMBBH sources using next-generation PTAs and their potential for constraining dark energy under an optimistic scenario considering only the presence of white noise. By constructing light-cone SMBBH populations across hardening timescales $$(\tau _H = 0.1/5/10$$ Gyr) and computing signal-to-noise ratios (SNR), we find advanced PTAs can resolve $$10^2$$ – $$10^3$$ sources with SNR $$> 8$$ (primarily at $$z < 1$$ with chirp masses of $$10^8$$ – $$10^{10}M_{\odot }).$$ If electromagnetic counterparts can be identified, optimal configurations $$(\sigma _t = 50$$ ns, $$N_p = 1000,$$ $$T_{\text {obs}} = 30$$ yr with $$ \tau _H \le 5$$ Gyr) could constrain the dark energy equation-of-state (EoS) parameter $\textit{w}$ to $$\Delta w \sim 0.023$$ –0.048, where the constraints only exhibit weak dependence on $$\tau _H$$ within 0.1–5 Gyr. If only $$10\%$$ of GW sources have detectable electromagnetic counterparts, constraints weaken to $$\Delta w = 0.075$$ $$(\tau _H = 0.1$$ Gyr) and $$\Delta w = 0.162$$ $$(\tau _H = 5$$ Gyr) under the most optimal parameter configuration. What’s more, conservative PTAs $$(N_p = 500,$$ $$\sigma _t = 100$$ –200 ns) with additional 30-year data accumulation could double resolvable source counts and improve $$\Delta w$$ precision by $$\sim 40\%.$$

Qing Yang

Gu-yue Zhang

Yi Huang

Xiao Guo

Prospective constraints on dark energy from nanohertz individual gravitational wave sources

A search for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>K</mi><mrow><mi mathvariant="normal">S</mi><mo stretchy="false">(</mo><mi mathvariant="normal">L</mi><mo stretchy="false">)</mo></mrow><mn>0</mn></msubsup><mo stretchy="false">→</mo><msup><mi>π</mi><mo>+</mo></msup><msup><mi>π</mi><mo>−</mo></msup><msup><mi>μ</mi><mo>+</mo></msup><msup><mi>μ</mi><mo>−</mo></msup></math> decays is performed using proton-proton collision data collected by the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>5.4</mn><mtext> </mtext><mtext> </mtext><msup><mi>fb</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup></math>. No <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>K</mi><mrow><mi mathvariant="normal">S</mi><mo stretchy="false">(</mo><mi mathvariant="normal">L</mi><mo stretchy="false">)</mo></mrow><mn>0</mn></msubsup><mo stretchy="false">→</mo><msup><mi>π</mi><mo>+</mo></msup><msup><mi>π</mi><mo>−</mo></msup><msup><mi>μ</mi><mo>+</mo></msup><msup><mi>μ</mi><mo>−</mo></msup></math> signals are found and upper limits are set for the first time on the branching fractions <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="script">B</mi><mo stretchy="false">(</mo><msubsup><mrow><mi>K</mi></mrow><mrow><mi mathvariant="normal">S</mi></mrow><mrow><mn>0</mn></mrow></msubsup><mo stretchy="false">→</mo><mrow><msup><mrow><mi>π</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>π</mi></mrow><mrow><mo>−</mo></mrow></msup><mrow><msup><mrow><mi>μ</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>μ</mi></mrow><mrow><mo>−</mo></mrow></msup><mo stretchy="false">)</mo></mrow></mrow><mo>&lt;</mo><mn>1.4</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>9</mn></mrow></msup></mrow></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="script">B</mi><mo stretchy="false">(</mo><msubsup><mrow><mi>K</mi></mrow><mrow><mi mathvariant="normal">L</mi></mrow><mrow><mn>0</mn></mrow></msubsup><mo stretchy="false">→</mo><mrow><msup><mrow><mi>π</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>π</mi></mrow><mrow><mo>−</mo></mrow></msup><mrow><msup><mrow><mi>μ</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>μ</mi></mrow><mrow><mo>−</mo></mrow></msup><mo stretchy="false">)</mo></mrow></mrow><mo>&lt;</mo><mn>6.6</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>7</mn></mrow></msup></mrow></math>, at the 90% confidence level.

R. Aaij

A.S.W. Abdelmotteleb

C. Abellan Beteta

F. Abudinén

T. Ackernley

A.A. Adefisoye

B. Adeva

M. Adinolfi

P. Adlarson

C. Agapopoulou

C.A. Aidala

Z. Ajaltouni

S. Akar

K. Akiba

P. Albicocco

J. Albrecht

R. Aleksiejunas

F. Alessio

P. Alvarez Cartelle

R. Amalric

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

S. Arguedas Cuendis

L. Arnone

A. Artamonov

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

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

S. Bashir

B. Batsukh

P.B. Battista

A. Bay

A. Beck

M. Becker

F. Bedeschi

I.B. Bediaga

N.A. Behling

S. Belin

A. Bellavista

K. Belous

I. Belov

I. Belyaev

G. Benane

G. Bencivenni

E. Ben-Haim

A. Berezhnoy

R. Bernet

S. Bernet Andres

A. Bertolin

F. Betti

J. Bex

O. Bezshyyko

S. Bhattacharya

J. Bhom

M.S. Bieker

N.V. Biesuz

A. Biolchini

M. Birch

F.C.R. Bishop

A. Bitadze

A. Bizzeti

T. Blake

F. Blanc

Search for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msubsup><mrow><mi>K</mi></mrow><mrow><mrow><mi mathvariant="normal">S</mi><mo stretchy="false">(</mo><mi mathvariant="normal">L</mi><mo stretchy="false">)</mo></mrow></mrow><mn>0</mn></msubsup><mo stretchy="false">→</mo><msup><mrow><mi>π</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>π</mi></mrow><mrow><mo>−</mo></mrow></msup><msup><mrow><mi>μ</mi></mrow><mrow><mo>+</mo></mrow></msup><msup><mrow><mi>μ</mi></mrow><mrow><mo>−</mo></mrow></msup></mrow></math> decays at LHCb

We present the nonrelativistic QCD (NRQCD) calculations at the next-to-leading order (NLO) of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>α</mi><mi>s</mi></msub></math> for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>B</mi><mi>c</mi><mo>*</mo></msubsup><mo stretchy="false">→</mo><msub><mi>η</mi><mi>c</mi></msub></math> vector, axial-vector, tensor, and axial-tensor form factors, and obtain complete analytical expressions for the form factors, along with their asymptotic forms in the hierarchical heavy quark limit. Our results show that the NLO corrections are both sizable and well behaved in the low squared transfer momentum <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo stretchy="false">(</mo><msup><mi>q</mi><mn>2</mn></msup><mo stretchy="false">)</mo></math> region. Using the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>NRQCD</mi><mo>+</mo><mtext>lattice</mtext></mrow><mo>+</mo><mi>z</mi></math>-series method, we further provide theoretical predictions for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>B</mi><mi>c</mi><mo>*</mo></msubsup><mo stretchy="false">→</mo><msub><mi>η</mi><mi>c</mi></msub></math> form factors across the full physical <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>q</mi><mn>2</mn></msup></math> range. Based on these predicted form factors, we finally compute the decay widths and branching fractions for the semileptonic decays <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>B</mi><mi>c</mi><mo>*</mo></msubsup><mo stretchy="false">→</mo><msub><mi>η</mi><mi>c</mi></msub><mo>+</mo><mi>l</mi><msub><mi>ν</mi><mi>l</mi></msub></math>.

Wei Tao

Ya-Hui Zhao

Li-Ting Wang

Qin Chang

Zhen-Jun Xiao

Form factors for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>B</mi><mi>c</mi><mo>*</mo></msubsup><mo stretchy="false">→</mo><msub><mi>η</mi><mi>c</mi></msub><mo>+</mo><mi>l</mi><msub><mi>ν</mi><mi>l</mi></msub></math> at NLO in QCD

The associated production of a photon and a top-antitop quark pair $$ \left(t\overline{t}\gamma \right) $$ is important for measuring the top-quark charge and probing the top-photon interaction, and it requires improved theoretical predictions. We focus on the calculation of two-loop amplitudes for $$ t\overline{t}\gamma $$ production at hadron colliders. The infrared singularities with full top-quark mass dependence are derived from universal anomalous dimensions combined with one-loop massive amplitudes expanded to higher orders in the dimensional regulator $\textit{ϵ}$. The finite remainders are approximated in the high-energy boosted limit using the mass-factorization formula. To validate our approach, we compare approximate one-loop amplitudes up to $$ \mathcal{O}\left({\epsilon}^2\right) $$ , as well as the two-loop infrared poles, against our exact results. The results in this paper serve as an important step toward next-to-next-to-leading order predictions for $$ t\overline{t}\gamma $$ production.

France

Guoxing Wang

Li Yang

Two-loop QCD amplitudes for $$ t\overline{t}\gamma $$ production at hadron colliders

We investigate the physics reach and potential for the study of $\textit{B}$-meson decays to invisible final states at the Future Circular Collider running electron-positron collisions at the $\textit{Z}$ pole (FCC-ee). Signal and background candidates are simulated for a proposed multipurpose detector, including inclusive contributions from $\textit{Z}$ decays to leptons or quarks. Signal candidates are selected by a mixture of rectangular cuts and a multiclass boosted decision tree classifier.

United Kingdom

M. Kenzie

R. Mangrulkar

A. Wiederhold

E. Wood

Prospects of searches for invisible $\textit{B}$-meson decays at FCC-ee

We consider a free complex massive scalar on the quotient spacetime AdS $\textit{/}$ℤ, which has the isometry group SO(2, 2) rather than its universal cover. This problem is of interest as a special example of QFT on a spacetime with closed timelike curves (CTCs), as a new context in which to study generalizations of AdS/CFT and for its role in celestial holography. A basis of time-periodic solutions to the Klein-Gordon wave equation is found in terms of hypergeometric functions. They fall into a PT even and a PT odd principal series representation, rather than the more familiar highest-weight representations of the cover of SO(2, 2). For masses below the Breitenlohner-Freedman (BF) bound, the modes fall on the unitary principal series. The presence of CTCs precludes the usual canonical quantization, but geometric quantization, which begins with a symplectic form on the phase space of classical solutions, is applicable. Operators, commutators, an SO(2, 2) invariant vacuum and a Fock space are constructed and transform like those of a CFT . The Fock space norm is positive below the BF bound. In celestial holography, AdS $\textit{/}$ℤ arises as leaves of a hyperbolic foliation of Klein space. Our analysis determines new entries in the symmetry-constrained celestial bulk-to-boundary dictionary. In particular the Klein space 𝒮-matrix is dual to a maximally entangled state in the tensor product of two copies of the ‘wedge CFT ’ associated to the timelike and spacelike wedges of Klein space. Translation invariance is not present in the wedge CFT itself but emerges as a property of this maximally entangled state.

United States

Walker Melton

Andrew Strominger

Tianli Wang

Quantum fields on time-periodic AdS3 $\textit{/}$ℤ

A Monte Carlo generator of high energy cosmic ray interactions, relying on a very basic and transparent theoretical formalism, in the framework of the Reggeon field theory, is presented. The main motivation for our work is to provide a new cosmic ray interaction model characterized by relatively transparent physics, sufficient parameter freedom, and a high computational efficiency, which can be easily managed by external users, including a retuning of the model parameters. Such a model can be used for studying potential modifications of the interaction treatment, necessary for describing particular sets of data on extensive air showers initiated by high energy cosmic rays, at a microscopic level, thereby keeping a consistency with general restrictions, like the unitarity, energy-momentum and charge conservation, and Lorentz and isospin invariance. Importantly, this should allow one to study a compatibility of such modifications with relevant accelerator data. The model results for particle production and for basic extensive air shower characteristics are presented and discussed.

Sergey Ostapchenko

Tanguy Pierog

Günter Sigl

Basic model for high energy cosmic ray interactions