In this paper, pair production of standard model (SM)-like Higgs bosons, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>h</mi><mi>h</mi></math>, is studied through <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>γ</mi><mi>γ</mi></math> scattering at future electron-positron colliders, in the framework of the inert doublet model with two active doublets—i.e., the I(<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>1</mn><mo>+</mo><mn>2</mn></mrow></math>)HDM for short. The relevance of the process <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>γ</mi><mi>γ</mi><mo stretchy="false">→</mo><mi>h</mi><mi>h</mi></math> for such a beyond-the-SM (BSM) scenario stems from the fact that it is a one-loop process at lowest order, wherein inert charged states <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>χ</mi><mo>±</mo></msup></math> contribute alongside <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>W</mi><mo>±</mo></msup></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>H</mi><mo>±</mo></msup></math>, and heavy fermions (primarily, bottom and top quarks), crucially, at the same perturbative order. Given that <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>χ</mi><mo>±</mo></msup><mo>/</mo><msup><mi>H</mi><mo>±</mo></msup></math> masses and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>h</mi><msup><mi>S</mi><mo>+</mo></msup><msup><mi>S</mi><mo>−</mo></msup></math> (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>S</mi><mo>±</mo></msup><mo>=</mo><msup><mi>χ</mi><mo>±</mo></msup><mo>,</mo><msup><mi>H</mi><mo>±</mo></msup></math>) couplings are very mildly constrained, there exist regions of the parameter space of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">I</mi><mo stretchy="false">(</mo><mrow><mn>1</mn><mo>+</mo><mn>2</mn></mrow><mo stretchy="false">)</mo><mi>HDM</mi></math> where the former can be rather light and the latter rather large. After imposing up-to-date theoretical and experimental constraints on the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">I</mi><mo stretchy="false">(</mo><mrow><mn>1</mn><mo>+</mo><mn>2</mn></mrow><mo stretchy="false">)</mo><mi>HDM</mi></math>, it is found that the production rates of such processes at future <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>γ</mi><mi>γ</mi></math> machines can be enhanced by up to a factor of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>≈</mo><mn>50</mn></math> with respect to the SM, significantly exceeding typical yields of conventional two-Higgs-doublet models (2HDMs). Further, thanks to the level of control that one can attain at such facilities on the photon kinematics, leading to excellent invariant mass resolution of the incoming photon pairs, we show how it is possible to extract from this process the value of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>χ</mi><mo>±</mo></msup></math> mass (along with those of the active <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>H</mi><mo>±</mo></msup></math> states) with high precision, and whichever of the decays of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>h</mi><mi>h</mi></math> pair, both with and without beam polarization.

France

Morocco

Abdesslam Arhrib

Ayoub Hmissou

United Kingdom

Sweden

Stefano Moretti

Larbi Rahili

Probing standard-model-like di-Higgs production at photon-photon colliders in the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="normal">I</mi><mo stretchy="false">(</mo><mrow><mn>1</mn><mo>+</mo><mn>2</mn></mrow><mo stretchy="false">)</mo><mi>HDM</mi></mrow></math> type-I

We analyze quantum obstructions to classical infinite distance limits in four-dimensional string compactifications with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">N</mi><mo>=</mo><mn>1</mn></math> supersymmetry. Such quantum effects signal a severe departure from the perturbative effective action and can be of considerable importance for string model building. Our focus is on the complex structure moduli space of type IIB orientifolds with O7/O3-planes and its F-theory description. In this first part of our analysis, we investigate the behavior of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>g</mi><mi>s</mi></msub></math> corrections in infinite distance complex structure limits. Our main finding is that, depending on the location of the O7-plane, nonperturbative corrections in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>g</mi><mi>s</mi></msub></math> can become unsuppressed, thus obstructing a perturbative type IIB description in the corresponding asymptotic region of the field space. In particular, this applies to large complex structure limits. To show this, we study the F-theory description of the type IIB orientifold, in which all pure <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>g</mi><mi>s</mi></msub></math> corrections are encoded in the (classical) geometry of an elliptic Calabi-Yau fourfold. This <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>g</mi><mi>s</mi></msub></math>-corrected moduli space is found to differ significantly from the classical moduli space. In extreme cases the classical infinite distance degeneration can be completely removed at the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>g</mi><mi>s</mi></msub></math>-corrected quantum level. The behavior of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>α</mi><mo>′</mo></msup></math> corrections, as well as implications for string model building, are discussed in a companion paper.

Germany

Lukas Kaufmann

Jeroen Monnee

Timo Weigand

Max Wiesner

Quantum obstructions for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">N</mi><mo>=</mo><mn>1</mn></math> infinite distance limits. I. <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>g</mi><mi>s</mi></msub></math> obstructions

Recently, Ai, Cruz, Garbrecht, and Tamarit (ACGT) [1–3] claimed that the strong CP problem can be avoided by adopting a particular order of limits in the Euclidean path integral, in which the spacetime volume is taken to infinity before summing over all topological sectors. We critically examine this proposal using exactly solvable examples of one-dimensional quantum mechanics on a ring, namely the quantum rotor and the quantum pendulum. These systems provide fully controlled settings with known $\textit{θ}$-dependent spectra. We find that the ACGT procedure fails to reproduce the correct energy spectrum. Since the spectrum is a direct physical observable, this result demonstrates that the proposed order of limits cannot be justified and conclusions about CP conservation in QCD cannot be based on this prescription alone.

Japan

Mohammad Aghaie

Ryosuke Sato

A particle on a ring or: how I learned to stop worrying and love $\textit{θ}$-vacua

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.

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.

Thong T.Q. Nguyen

Spain

Pedro De la Torre Luque

Isabelle John

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