A dense neutrino plasma can exhibit collective flavor evolution caused by neutrino-neutrino refraction. Recently, a new class of exact nonlinear inhomogeneous solutions was discovered: single-wave (SW) solutions of the fast flavor system. The key property is that the flavor occupation numbers remain homogeneous, whereas the field of flavor coherence varies spatially with a single wave vector. The equations of motion for this structure resemble those of a collection of classical spins, in analogy with the homogeneous slow and fast flavor cases. In contrast, the SW system is not integrable (it does not possess Gaudin invariants) so that, while two-beam pendulum solutions are inevitable, they do not extend to a multi-angle system. We develop a taxonomy of all known nonlinear collective flavor solutions, explaining the overlap between categories and their differences.

Germany

Damiano Fiorillo

Georg Raffelt

Single-wave solutions of the neutrino fast flavor system. Part I. Mechanical properties

We describe how to construct an effective Hamiltonian for leading twist states in $\textit{d}$ ≥ 3 CFTs based on the separation of scales that emerges at large spin $\textit{J}$ between the AdS radius $\textit{ℓ}$ and the characteristic distance ~$\textit{ℓ}$ log $\textit{J}$ between particles rotating in AdS with angular momentum $\textit{J}$. As a controlled example, we work specifically with the toy model of a bulk complex scalar field $\textit{ϕ}$ with a $\textit{λ}$|$\textit{ϕ}$| coupling in AdS, up to $\textit{O}$($\textit{λ}$ ). For a given choice of twist cutoff Λ in the effective theory, interactions are separated into long-distance nonlocal potential terms, arising from $\textit{t}$-channel exchange of states with twist ≤ Λ , and short-distance local terms fixed by matching to low spin CFT data. At $\textit{O}$($\textit{λ}$ ), the effective Hamiltonian for the toy model has two-body nonlocal potential terms from one-loop bulk diagrams as well as three-body nonlocal potential terms from tree-level exchange of $\textit{ϕ}$. We describe in detail how these contributions are evaluated and how they are related to the CFT data entering in the large spin expansion. We discuss how to apply the construction of such effective Hamiltonians for models which do not have a large central charge or a sparse spectrum and are not typically considered holographic.

United States

Giulia Fardelli

A. Fitzpatrick

Wei Li

Towards large-spin effective theory. Part I. Three-particle states in AdS $\textit{ϕ}$ 4 theory

We propose a cogenesis scenario in which both the baryon asymmetry and dark matter abundance originate from the kinetic misalignment of the QCD axion. The framework unifies the Peccei-Quinn (PQ) mechanism with a type I seesaw sector, where Hubble-induced masses and higher-dimensional PQ-violating operators drive early time axion rotation. Working within the Dine-Fischler-Srednicki-Zhitnitsky axion model augmented by heavy neutrinos, we identify the parametric window of right-handed neutrino masses, determined by its decay rate, and the range of Hubble scales compatible with successful cogenesis, while maintaining the axion solution to the strong <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi><mi>P</mi></math> problem and satisfying current limits on axion isocurvature perturbations. Our results establish kinetic misalignment as a robust and predictive mechanism for the QCD-axion cogenesis, leading to correlated constraints on the right-handed neutrino mass and the inflation scale for an axion decay constant within the viable range <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>f</mi></mrow><mrow><mi>a</mi></mrow></msub><mo>∼</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>8</mn></mrow></msup><mi>–</mi><msup><mrow><mn>10</mn></mrow><mrow><mn>12</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi>GeV</mi></mrow></math>.

South Korea

Eung Jin Chun

Spontaneous cogenesis by the QCD axion in a type I seesaw mechanism

In the type-I two-Higgs-doublet model, the pseudoscalar $\textit{A}$ can act as a long-lived particle (LLP) for sufficiently large values of tan $\textit{β}$. At the LHC, the $\textit{A}$ particles are predominantly produced in pairs through $\textit{pp}$ → $\textit{W}$ /$\textit{Z}$ → $\textit{H}$ /$\textit{H A}$, with subsequent decays $\textit{H}$ /$\textit{H}$ → $\textit{W}$ /$\textit{Z A}$. For the mass range of our interest, 10 GeV ≲ $\textit{m}$ ≲ 100 GeV, the pseudoscalar $\textit{A}$ typically decays into a pair of bottom quarks after traveling a macroscopic distance from its production point, giving rise to displaced-vertex (DV) signatures inside the inner detector. We perform Monte Carlo simulations of signal events with DVs plus jets, and assess the discovery prospects of $\textit{A}$ as an LLP at the ATLAS and CMS experiments. Our findings show that a substantial portion of the parameter space with $\textit{m}$ > 10 GeV has already been excluded by LHC Run-2 data, while the high-luminosity LHC will be able to probe broader regions.

China

Lei Wang

Zeren Wang

Haotian Xu

Probing a long-lived pseudoscalar in type-I 2HDM with displaced vertices and jets at the LHC

Entanglement asymmetry is a relative entropy that faithfully diagnoses symmetry breaking in quantum states, possibly within a spatial subregion. In this work, we extend such framework to higher-form symmetries and compute entanglement asymmetry in theories with spontaneously-broken continuous zero- and higher-form symmetries. One of our central results is an entropic Coleman-Mermin-Wagner theorem, for 0- and $\textit{p}$-form symmetries, valid also on subregions, which forbids spontaneous breaking of continuous $\textit{p}$-form symmetries in spacetime dimensions $\textit{d}$ ⩽ $\textit{p}$ + 2. Our theorem not only qualifies symmetry breaking, it also quantifies it: spontaneous breaking triggers a nonvanishing entanglement asymmetry that grows monotonically towards the infrared, and counts the number of Goldstone fields. Along the way, we derive standalone results concerning the entanglement entropy and asymmetry of Goldstone bosons and gauge fields. In particular, we find a closed-form expression for the Rényi asymmetries of a compact scalar field on spherical subregions in three and four spacetime dimensions, and for higher-form gauge fields in higher dimensions.

Italy

Francesco Benini

Eduardo García-Valdecasas

Belgium

Stathis Vitouladitis

Higher-form entanglement asymmetry. Part I. The limits of symmetry breaking

$\textit{N}$-naturalness is a novel solution to the electroweak hierarchy problem which posits $\textit{N}$ copies of the Standard Model with varying Higgs mass-squared parameters. Reheating proceeds through a “reheaton” particle that deposits most of its energy density into the Standard Model and small but potentially measurable fractions into the other copies. Typically the sector with the lightest negative Higgs mass-squared is identified as the Standard Model. We demonstrate that $\textit{N}$-naturalness admits a broader class of realizations in which the Standard Model is identified with a heavier sector, rather than being restricted to the lightest. This is made possible by resonant mixing between the reheaton and the Higgs, which generically causes one sector to be preferentially reheated and to acquire the largest share of the energy density, singling it out as the Standard Model. We demonstrate that this scenario is consistent with current cosmological bounds on new relativistic degrees of freedom and overclosure constraints from heavy stable relics, while future cosmic microwave background and high redshift surveys will probe significant portions of the remaining parameter space. Furthermore, we highlight the possibility of a novel stochastic gravitational wave spectrum from the many cosmological first order QCD phase transitions occurring across the other sectors.

Brian Batell

Akshay Ghalsasi

Wenjie Huang

Matthew Low

$\textit{i}$-ncidental $\textit{N}$-naturalness

The decay of light bosonic dark matter particles can produce a bright electron/positron (<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>) flux that can be strongly constrained by local Voyager observations of the direct <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> flux, as well as 511 keV line and x-ray continuum observations of <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> emission. We carefully analyze the <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> yield and resulting cosmic ray and x-ray spectra from theoretically well-motivated light dark matter models, including (a) electrophilic axion-like particles, (b) dark photons, (c) scalars, and (d) <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>B</mi><mo>−</mo><mi>L</mi></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>L</mi><mi>i</mi></msub><mo>−</mo><msub><mi>L</mi><mi>j</mi></msub></math> vector bosons. We use the morphology and spectrum of the INTEGRAL 511 keV line data, the eROSITA x-ray continuum spectrum and the Voyager <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> spectrum to constrain the decay lifetime and coupling of each dark matter model. We find that 511 keV observations typically set world-leading limits on bosonic dark matter decay below masses of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>∼</mo><mn>1</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>, while eROSITA observations provide the strongest constraints in the range from 1–10 GeV. Finally, we forecast future limits from 21 cm line searches with next-generation HERA data.

Sweden

Thong T.Q. Nguyen

Spain

Pedro De la Torre Luque

Isabelle John

United Kingdom

Shyam Balaji

Pierluca Carenza

Tim Linden

INTEGRAL, eROSITA and Voyager constraints on light bosonic dark matter: ALPs, dark photons, scalars, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>B</mi><mo>−</mo><mi>L</mi></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>L</mi><mi>i</mi></msub><mo>−</mo><msub><mi>L</mi><mi>j</mi></msub></math> vectors

Based on <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo stretchy="false">(</mo><mn>10087</mn><mo>±</mo><mn>44</mn><mo stretchy="false">)</mo><mo>×</mo><msup><mn>10</mn><mn>6</mn></msup><mtext> </mtext><mtext> </mtext><mi>J</mi><mo>/</mo><mi>ψ</mi></math> events collected by the BESIII detector at the center-of-mass energy <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msqrt><mrow><mi>s</mi></mrow></msqrt><mo>=</mo><mn>3.097</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></mrow></math>, the first absolute measurement of the branching fractions for the decays <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi mathvariant="normal">Σ</mi><mo>+</mo></msup><mo stretchy="false">→</mo><mi>p</mi><msup><mi>π</mi><mn>0</mn></msup></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi mathvariant="normal">Σ</mi><mo>+</mo></msup><mo stretchy="false">→</mo><mi>n</mi><msup><mi>π</mi><mo>+</mo></msup></math> is performed. The branching fractions are determined to be <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>B</mi></mrow><mrow><msup><mrow><mi mathvariant="normal">Σ</mi></mrow><mrow><mo>+</mo></mrow></msup><mo stretchy="false">→</mo><mi>p</mi><msup><mrow><mi>π</mi></mrow><mrow><mn>0</mn></mrow></msup></mrow></msub><mo>=</mo><mo stretchy="false">(</mo><mn>49.79</mn><mo>±</mo><mn>0.06</mn><mo>±</mo><mn>0.22</mn><mo stretchy="false">)</mo><mo>%</mo></mrow></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>B</mi><mrow><msup><mi mathvariant="normal">Σ</mi><mo>+</mo></msup><mo stretchy="false">→</mo><mi>n</mi><msup><mi>π</mi><mo>+</mo></msup></mrow></msub><mo>=</mo><mo stretchy="false">(</mo><mn>49.87</mn><mo>±</mo><mn>0.05</mn><mo>±</mo><mn>0.29</mn><mo stretchy="false">)</mo><mo>%</mo></math>, where the first uncertainties are statistical and the second systematic. Our results show significant deviations from the Particle Data Group values for both decays, with differences of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>4.4</mn><mi>σ</mi></mrow></math> for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi mathvariant="normal">Σ</mi><mo>+</mo></msup><mo stretchy="false">→</mo><mi>p</mi><msup><mi>π</mi><mn>0</mn></msup></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>3.4</mn><mi>σ</mi></mrow></math> for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi mathvariant="normal">Σ</mi><mo>+</mo></msup><mo stretchy="false">→</mo><mi>n</mi><msup><mi>π</mi><mo>+</mo></msup></math>. These measurements will play important roles in precise studies of the decay properties of strange, charmed, and beauty baryons with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi mathvariant="normal">Σ</mi><mo>+</mo></msup></math> in the final states. Furthermore, the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Δ</mi><mi>I</mi><mo>=</mo><mn>1</mn><mo>/</mo><mn>2</mn></math> rule is tested in nonleptonic <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi mathvariant="normal">Σ</mi><mo>±</mo></msup></math> decays. The observed results deviate from zero by more than <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>5</mn><mi>σ</mi></math>, indicating the presence of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Δ</mi><mi>I</mi><mo>=</mo><mn>3</mn><mo>/</mo><mn>2</mn></math> transition amplitude in the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Σ</mi></math> hyperon decays.

M. Ablikim

Russia

M.N. Achasov

P. Adlarson

X.C. Ai

R. Aliberti

A. Amoroso

Q. An

Y. Bai

JINR

O. Bakina

Y. Ban

H.R. Bao

X.L. Bao

Poland

V. Batozskaya

Mongolia

K. Begzsuren

N. Berger

M. Berlowski

M.B. Bertani

D. Bettoni

F. Bianchi

E. Bianco

A. Bortone

I. Boyko

R.A. Briere

A. Brueggemann

H. Cai

M.H. Cai

X. Cai

A. Calcaterra

G.F. Cao

N. Cao

Türkiye

S.A. Cetin

X.Y. Chai

J.F. Chang

T.T. Chang

G.R. Che

Y.Z. Che

C.H. Chen

Chao Chen

G. Chen

H.S. Chen

H.Y. Chen

M.L. Chen

S.J. Chen

S.M. Chen

T. Chen

W. Chen

X.R. Chen

X.T. Chen

X.Y. Chen

Y.B. Chen

Y.Q. Chen

Z.K. Chen

J. Cheng

L.N. Cheng

S.K. Choi

X. Chu

G. Cibinetto

F. Cossio

J. Cottee-Meldrum

H.L. Dai

J.P. Dai

X.C. Dai

A. Dbeyssi

R.E. de Boer

D. Dedovich

C.Q. Deng

Z.Y. Deng

A. Denig

I. Denisenko

M. Destefanis

F. De Mori

X.X. Ding

Y. Ding

Y.X. Ding

J. Dong

L.Y. Dong

M.Y. Dong

X. Dong

M.C. Du

S.X. Du

X.L. Du

Y.Y. Duan

Z.H. Duan

P. Egorov

G.F. Fan

J.J. Fan

Y.H. Fan

J. Fang

S.S. Fang

W.X. Fang

Y.Q. Fang

L. Fava

F. Feldbauer

G. Felici

C.Q. Feng

J.H. Feng

L. Feng

Q.X. Feng

First measurement of the absolute branching fractions of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi mathvariant="normal">Σ</mi><mo>+</mo></msup></math> nonleptonic decays and test of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Δ</mi><mi>I</mi><mo>=</mo><mn>1</mn><mo>/</mo><mn>2</mn></math> rule

The normalised decay rate of $\textit{B}$ → $\textit{J/ψ}$(→ $\textit{μ}$ $\textit{μ}$ )$\textit{K}$ is measured as a function of the lepton helicity angle using a data sample corresponding to an integrated luminosity of 1$\textit{.}$1 fb collected during October 2024 with the upgraded (Upgrade I) LHCb detector. This angular distribution can be parameterised by two coefficients, the forward-backward asymmetry, $\textit{A}$ , and the flatness parameter, $\textit{F}$ , whose values are constrained by conservation of angular momentum. These coefficients are measured both integrated and differentially across various kinematic and detector-response variables, and the results are found to be in good agreement with expectations. These measurements show that the detector response of the LHCb Upgrade I experiment is understood to the precision required to reliably extract the angular coefficients associated with rare $\textit{b}$ → $\textit{sμ}$ $\textit{μ}$ and $\textit{b}$ → $\textit{dμ}$ $\textit{μ}$ transitions, which are particularly sensitive to physics beyond the Standard Model.

Netherlands

R. Aaij

A. Abdelmotteleb

Switzerland

C. Abellan Beteta

F. Abudinén

T. Ackernley

A. Adefisoye

B. Adeva

M. Adinolfi

France

C. Agapopoulou

C. Aidala

Z. Ajaltouni

S. Akar

K. Akiba

M. Akthar

P. Albicocco

J. Albrecht

Lithuania

R. Aleksiejunas

F. Alessio

P. Alvarez Cartelle

R. Amalric

Brazil

S. Amato

J. 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

A. Artamonov

M. Artuso

E. Aslanides

R. Ataíde Da Silva

M. Atzeni

B. Audurier

J. Authier

Differential decay rate of $\textit{B}$ + $\textit{→ J/ψK}$ + with the LHCb Upgrade I experiment