<p>We introduce a class of multi-Higgs doublet extensions of the Standard Model that solve the strong <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi><mi>P</mi></math> problem with profound consequences for the flavor sector. The Yukawa matrices are constrained to have many zero entries by a “Higgs-flavor” symmetry, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>G</mi><mi>HF</mi></msub></math>, that acts on Higgs and quark fields. The violation of both <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi><mi>P</mi></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>G</mi><mi>HF</mi></msub></math> occurs in the Higgs mass matrix so that, for certain choices of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>G</mi><mi>HF</mi></msub></math> charges, the strong <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi><mi>P</mi></math> parameter <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mover accent="true"><mi>θ</mi><mo stretchy="false">¯</mo></mover></math> is zero at tree level. Radiative corrections to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mover accent="true"><mi>θ</mi><mo stretchy="false">¯</mo></mover></math> are computed in this class of theories. They vanish in realistic two-Higgs doublet models with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>G</mi><mi>HF</mi></msub><mo>=</mo><msub><mi mathvariant="double-struck">Z</mi><mn>3</mn></msub></math>. We also construct realistic three-Higgs models with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>G</mi><mi>HF</mi></msub><mo>=</mo><mi mathvariant="normal">U</mi><mo stretchy="false">(</mo><mn>1</mn><mo stretchy="false">)</mo></math>, where the one-loop results for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mover accent="true"><mi>θ</mi><mo stretchy="false">¯</mo></mover></math> are model-dependent. Requiring <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mover accent="true"><mi>θ</mi><mo stretchy="false">¯</mo></mover><mo>&lt;</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>10</mn></mrow></msup></math> has important implications for the flavor problem by constraining the Yukawa coupling and Higgs mass matrices. Contributions to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mover accent="true"><mi>θ</mi><mo stretchy="false">¯</mo></mover></math> from higher-dimension operators are computed at one loop and can also be sufficiently small, although the hierarchy problem of this class of theories is worse than in the Standard Model.</p>

United States

Lawrence Hall

Claudio Andrea Manzari

Bea Noether

Strong <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi><mi>P</mi></math> and flavor in multi-Higgs theories

<p>Heavy axions that couple to both quantum electrodynamics and quantum chromodynamics with masses on the order of MeV–GeV and high-scale decay constants in excess of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mo>∼</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>8</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi>GeV</mi></mrow></math> may arise generically in, e.g., axiverse constructions. In this work we provide the most sensitive search to date for the existence of such heavy axions using Fermi-LAT data toward four recent supernovae (SN): Cassiopea A, SN1987A, SN2023ixf, and SN2024ggi. We account for heavy axion production in the proto-neutron-star cores through nuclear and electromagnetic processes and then the subsequent decay of the axions into photons. While previous works have searched for gamma rays from SN1987A using the Solar Maximum Mission that observed SN1987A during the SN itself, we show that using Fermi Large Area Telescope data provides an approximately 5 orders of magnitude improvement in flux sensitivity for axions with lifetimes larger than around 10 yrs. We find no evidence for heavy axions and exclude large regions of previously unexplored parameter space.</p>

Joshua N. Benabou

Yujin Park

Garima Prabhakar

Benjamin R. Safdi

Inbar Savoray

Time-delayed gamma-ray signatures of heavy axions from core-collapse supernovae

It has long been established that axions could have been produced within the nascent proto-neutron star formed following the type II supernova SN1987A, escaped the star due to their weak interactions, and then converted to gamma rays in the Galactic magnetic fields; the nonobservation of a gamma-ray flash coincident with the neutrino burst leads to strong constraints on the axion-photon coupling for axion masses <math><mrow><msub><mrow><mi>m</mi></mrow><mrow><mi>a</mi></mrow></msub><mo>≲</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>10</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi>eV</mi></mrow></math>. In this Letter, we use SN1987A to constrain higher mass axions, all the way to <math><mrow><msub><mrow><mi>m</mi></mrow><mrow><mi>a</mi></mrow></msub><mo>∼</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>3</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi>eV</mi></mrow></math>, by accounting for axion production from the Primakoff process, nucleon bremsstrahlung, and pion conversion along with axion-photon conversion on the still-intact magnetic fields of the progenitor star. Moreover, we show that gamma-ray observations of the next Galactic supernova, leveraging the magnetic fields of the progenitor star, could detect quantum chromodynamics axions for masses above roughly <math><mrow><mn>50</mn><mtext> </mtext><mtext> </mtext><mi>μ</mi><mi>eV</mi></mrow></math>, depending on the supernova. We propose a new full-sky gamma-ray satellite constellation that we call the GALactic AXion Instrument for Supernova (GALAXIS) to search for such future signals along with related signals from extragalactic neutron star mergers.

Supernova Axions Convert to Gamma Rays in Magnetic Fields of Progenitor Stars

We study thermal production of dark matter (DM) in a realization of the minimal models of Bonnefoy et al. [Phys. Rev. Lett. 131, 221802 (2023)], where parity is used to solve the strong <math><mi>C</mi><mi>P</mi></math> problem by transforming the entire Standard Model (SM) into a mirror copy. Although the mirror electron <math><msup><mi>e</mi><mo>′</mo></msup></math> is a good DM candidate, its viability is mired by the presence of the mirror up quark <math><msup><mi>u</mi><mo>′</mo></msup></math>, whose abundance is intimately related to the <math><msup><mi>e</mi><mo>′</mo></msup></math> abundance and must be suppressed. This can be achieved through a sequential freeze-in mechanism, where mirror photons are first produced from SM gluons, and then the mirror photons produce <math><msup><mi>e</mi><mo>′</mo></msup></math>. After computing the details of this double freeze-in, we discuss the allowed parameter space of the model, which lies at the threshold of experimental observations. We find that this origin of <math><msup><mi>e</mi><mo>′</mo></msup></math> DM requires a low reheating temperature after inflation and is consistent with the baryon asymmetry arising from leptogenesis, providing mirror neutrinos have a significant degeneracy. Finally, we show that this <math><msup><mi>e</mi><mo>′</mo></msup></math> DM is not compatible with Higgs parity, the simplest scheme with exact parity, unless SM parameters deviate significantly from their central values or the minimal model is extended.

Quentin Bonnefoy

Amara McCune

Christiane Scherb

Dark matter in a mirror solution to the strong <math><mi>C</mi><mi>P</mi></math> problem

We propose theories of a complete mirror world with parity (<math><mi>P</mi></math>) solving the strong <math><mi>C</mi><mi>P</mi></math> problem. <math><mrow><mi>P</mi></mrow></math> exchanges the entire standard model with its mirror copy. We derive bounds on the two new mass scales that arise: <math><msup><mi>v</mi><mo>′</mo></msup></math> where parity and mirror electroweak symmetry are spontaneously broken, and <math><msub><mi>v</mi><mn>3</mn></msub></math> where the color groups break to the diagonal strong interactions. The strong <math><mi>C</mi><mi>P</mi></math> problem is solved even if <math><mrow><msub><mrow><mi>v</mi></mrow><mrow><mn>3</mn></mrow></msub><mo>≪</mo><msup><mrow><mi>v</mi></mrow><mrow><mo>′</mo></mrow></msup></mrow></math>, when heavy colored states at the scale <math><msub><mi>v</mi><mn>3</mn></msub></math> may be accessible at LHC and future colliders. Furthermore, we argue that the breaking of <math><mi>P</mi></math> introduces negligible contributions to <math><msub><mover><mi>θ</mi><mo>¯</mo></mover><mi>QCD</mi></msub></math>, starting at three-loop order. The symmetry breaking at <math><msub><mi>v</mi><mn>3</mn></msub></math> can be made dynamical, without introducing an additional hierarchy problem.

Colorful Mirror Solution to the Strong <math><mi>C</mi><mi>P</mi></math> Problem

Protoneutron stars formed during core-collapse supernovae are hot and dense environments that contain a sizable population of muons. If these interact with new long-lived particles with masses up to roughly 100 MeV, the latter can be produced and escape from the stellar plasma, causing an excessive energy loss constrained by observations of SN 1987A. In this article we calculate the emission of light dark fermions that are coupled to leptons via a new massive vector boson, and determine the resulting constraints on the general parameter space. We apply these limits to the gauged <math><msub><mi>L</mi><mi>μ</mi></msub><mo>−</mo><msub><mi>L</mi><mi>τ</mi></msub></math> model with dark fermions, and show that the SN 1987A constraints exclude a significant portion of the parameter space targeted by future experiments. We also extend our analysis to generic effective four-fermion operators that couple dark fermions to muons, electrons, or neutrinos. We find that SN 1987A cooling probes a new physics scale up to <math><mo>∼</mo><mn>7</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></math>, which is an order of magnitude larger than current bounds from laboratory experiments.

CERN

Spain

Jorge Martin Camalich

Germany

Jonas Spinner

Robert Ziegler

Supernova limits on muonic dark forces

ATLAS observed a limit for the cross section of dijet resonances, which is weaker than expected for a mass slightly below <math><mrow><mo>≈</mo><mn>1</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></mrow></math>. In addition, CMS reported hints for the (nonresonant) pair production of dijet resonances <math><mi>X</mi></math> via a particle <math><mi>Y</mi></math> at a very similar mass range with a local (global) significance of <math><mrow><mn>3.6</mn><mi>σ</mi></mrow></math> (<math><mrow><mn>2.5</mn><mi>σ</mi></mrow></math>) at <math><msub><mi>m</mi><mi>X</mi></msub><mo>≈</mo><mn>950</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>. In this article, we show that, using the preferred range for <math><msub><mi>m</mi><mi>X</mi></msub></math> from the ATLAS analysis, one can reinterpret the CMS analysis of didijets in terms of a resonant search with <math><mi>Y</mi><mo>→</mo><mi>X</mi><mi>X</mi></math>, with a significantly reduced look-elsewhere effect, finding an excess for <math><msub><mi>m</mi><mi>Y</mi></msub><mo>≈</mo><mn>3.6</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></math> with a significance of <math><mn>4.0</mn><mi>σ</mi></math> (<math><mn>3.2</mn><mi>σ</mi></math>) locally (globally). We present two possible UV completions capable of explaining the (di)dijet excesses, one containing two scalar diquarks, the other one involving heavy gluons based on an <math><mrow><mi>S</mi><mi>U</mi><mo>(</mo><mn>3</mn><msub><mrow><mo>)</mo></mrow><mrow><mn>1</mn></mrow></msub><mo>×</mo><mi>S</mi><mi>U</mi><mo>(</mo><mn>3</mn><msub><mrow><mo>)</mo></mrow><mrow><mn>2</mn></mrow></msub><mo>×</mo><mi>S</mi><mi>U</mi><mo>(</mo><mn>3</mn><msub><mrow><mo>)</mo></mrow><mrow><mn>3</mn></mrow></msub></mrow></math> gauge symmetry, spontaneously broken to <math><mi>S</mi><mi>U</mi><mo>(</mo><mn>3</mn><mo>)</mo></math> color. In the latter case, nonperturbative couplings are required, pointing toward a composite or extradimensional framework. In fact, using 5D anti–de Sitter space-time, one obtains the correct mass ratio for <math><msub><mi>m</mi><mi>X</mi></msub><mo>/</mo><msub><mi>m</mi><mi>Y</mi></msub></math>, assuming the <math><mi>X</mi></math> is the lowest-lying resonance, and predicts a third (di)dijet resonance with a mass around <math><mo>≈</mo><mn>2.2</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></math>.

Switzerland

Andreas Crivellin

South Africa

Bruce Mellado

Salah-Eddine Dahbi

Consistency and interpretation of the LHC dijet excesses

The discrepancies between data on rare <math><mi>b</mi></math>-hadron decays, controlled by the underlying neutral-current transitions <math><mi>b</mi><mo>→</mo><mi>s</mi><msup><mo>ℓ</mo><mo>+</mo></msup><msup><mo>ℓ</mo><mo>−</mo></msup><mo>(</mo><mo>ℓ</mo><mo>=</mo><mi>e</mi><mo>,</mo><mi>μ</mi><mo>)</mo></math>, and the corresponding Standard Model predictions constitute one of the most intriguing hints for new physics. Leptoquarks are prime candidates to solve these anomalies and, in particular, the scalar leptoquark, <math><msub><mi>S</mi><mn>3</mn></msub></math>, triplet under <math><mi>S</mi><mi>U</mi><mo>(</mo><mn>2</mn><msub><mo>)</mo><mi>L</mi></msub></math> with hypercharge <math><mi>Y</mi><mo>=</mo><mo>−</mo><mn>1</mn><mo>/</mo><mn>3</mn></math>, provides a very good fit to data. Here, we entertain the possibility that the same scalar leptoquark <math><msub><mi>S</mi><mn>3</mn></msub></math>, responsible for the lepton flavor universality anomalies, is the portal to a fermionic dark sector consisting of two additional vectorlike fermions, one of which is a candidate for the cosmological dark matter. We study two scenarios, where the dark matter candidate belongs to an <math><mi>S</mi><mi>U</mi><mo>(</mo><mn>2</mn><msub><mo>)</mo><mi>L</mi></msub></math> singlet and triplet respectively, and discuss the theory parameter space in the context of the dark matter candidate’s relic density and prospects for direct and indirect dark matter searches. Direct detection rates are highly suppressed and generically below the neutrino floor. Current observations with, and future prospects for, high-energy gamma-ray telescopes such as HESS and the Cherenkov Telescope Array are much more promising, as they already provide powerful constraints on the models under consideration, and will potentially probe the full parameter space in the future.

Stefano Profumo

Flavor inspired model for dark matter

The discrepancies between <math><mi>b</mi><mo>→</mo><mi>s</mi><msup><mo>ℓ</mo><mo>+</mo></msup><msup><mo>ℓ</mo><mo>−</mo></msup></math> data and the corresponding Standard Model predictions constitute one of the most significant hints for new physics currently available. In fact, many scenarios that can account for these anomalies have been proposed in the literature. However, only a single light new physics explanation, i.e., with a mass below the <math><mi>B</mi></math> meson scale, is possible: a light <math><mrow><msup><mrow><mi>Z</mi></mrow><mrow><mo>′</mo></mrow></msup></mrow></math> boson. In this article, we aim at excluding any light <math><msup><mi>Z</mi><mo>′</mo></msup></math> model as a solution to <math><mi>b</mi><mo>→</mo><mi>s</mi><msup><mo>ℓ</mo><mo>+</mo></msup><msup><mo>ℓ</mo><mo>−</mo></msup></math> data, using a minimal and conservative setup. Considering the improved limits on <math><mrow><mi>B</mi><mo>→</mo><msup><mrow><mi>K</mi></mrow><mrow><mo>(</mo><mo>*</mo><mo>)</mo></mrow></msup><mi>ν</mi><mi>ν</mi></mrow></math>, including the experimental sensitivities required for a proper treatment of the necessarily sizable <math><msup><mi>Z</mi><mo>′</mo></msup></math> width, together with the forthcoming Belle II analyses of <math><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup><mo>→</mo><msup><mi>μ</mi><mo>+</mo></msup><msup><mi>μ</mi><mo>−</mo></msup><mo>+</mo><mtext>invisible</mtext></math>, can rule out a <math><msup><mi>Z</mi><mo>′</mo></msup></math> explanation of <math><mi>b</mi><mo>→</mo><mi>s</mi><msup><mo>ℓ</mo><mo>+</mo></msup><msup><mo>ℓ</mo><mo>−</mo></msup></math> data with a mass below <math><mo>≈</mo><mn>4</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>. Importantly, such a light <math><msup><mi>Z</mi><mo>′</mo></msup></math> is the only viable single particle solution to the <math><mi>b</mi><mo>→</mo><mi>s</mi><msup><mo>ℓ</mo><mo>+</mo></msup><msup><mo>ℓ</mo><mo>−</mo></msup></math> anomalies predicting <math><mi>R</mi><mo>(</mo><msup><mi>K</mi><mrow><mo>(</mo><mo>*</mo><mo>)</mo></mrow></msup><mo>)</mo><mo>&gt;</mo><mn>0</mn></math> in high <math><msup><mi>q</mi><mn>2</mn></msup></math> bins, therefore providing an essential consistency test of data.

Wolfgang Altmannshofer

Austria

Gianluca Inguglia

Paul Feichtinger

Toward excluding a light <math><mrow><msup><mrow><mi>Z</mi></mrow><mrow><mo>′</mo></mrow></msup></mrow></math> explanation of <math><mi>b</mi><mo>→</mo><mi>s</mi><msup><mo>ℓ</mo><mo>+</mo></msup><msup><mo>ℓ</mo><mo>−</mo></msup></math>

The discrepancies between the measurements of rare (semi)leptonic <math><mi>B</mi></math> decays and the corresponding Standard Model predictions point convincingly toward the existence of new physics for which a heavy neutral gauge boson (<math><msup><mi>Z</mi><mo>′</mo></msup></math>) is a prime candidate. However, the effect of the mixing of the <math><msup><mi>Z</mi><mo>′</mo></msup></math> with the SM <math><mi>Z</mi></math>, even though it cannot be avoided by any symmetry, is usually assumed to be small and thus neglected in phenomenological analyses. In this paper we point out that a mixing of the naturally expected size leads to lepton flavor universal contributions, providing a very good fit to <math><mi>B</mi></math> data. Furthermore, the global electroweak fit is affected by <math><mi>Z</mi><mo>−</mo><msup><mi>Z</mi><mo>′</mo></msup></math> mixing where the tension in the <math><mi>W</mi></math> mass, recently confirmed and strengthened by the CDF measurement, prefers a nonzero value of it. We find that a <math><msup><mi>Z</mi><mo>′</mo></msup></math> boson with a mass between <math><mrow><mo>≈</mo><mn>1</mn><mi>–</mi><mn>5</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></mrow></math> can provide a unified explanations of the <math><mi>B</mi></math> anomalies and the <math><mi>W</mi></math> mass. This strongly suggest that the breaking of the new gauge symmetry giving raise to the <math><msup><mi>Z</mi><mo>′</mo></msup></math> boson is linked to electroweak symmetry breaking with intriguing consequences for model building.

Marcel Algueró

Joaquim Matias

Unified explanation of the anomalies in semileptonic <math><mi>B</mi></math> decays and the <math><mi>W</mi></math> mass