We propose a minimal scenario for light thermal dark matter (DM) in sub-GeV to GeV range by incorporating a scalar singlet DM in a type-I seesaw scenario extended by an additional Higgs doublet $\textit{ϕ}$ . The latter permits efficient annihilation of light scalar DM into leptonic final states including right-handed neutrinos (RHN). We keep the charged fermion as well as neutral fermion final states in forbidden regime to avoid bounds from indirect search as well as cosmic microwave background (CMB) data. After studying the purely forbidden DM scenario with neutral and charged fermion final states separately, we discuss the interplay of forbidden and non-forbidden channels in generating light thermal DM relic by considering neutral fermions in non-forbidden mode due to relatively weaker constraints. The model can also explain the anomalous magnetic moment of muon, W-mass anomaly and saturate experimental bounds on charged lepton flavour violation and DM direct detection while offering tantalising detection prospects of RHN, the mass of which is kept approximately in the same range as DM.

India

Debasish Borah

Pritam Das

South Korea

Satyabrata Mahapatra

Narendra Sahu

Light thermal dark matter via type-I seesaw portal

A correction to this paper has been published: https://doi.org/10.1007/JHEP11(2023)198

Armenia

Hasmik Poghosyan

Rubik Poghossian

Erratum to: A note on rank 5/2 Liouville irregular block, Painlevé I and the $$ {\mathcal{H}}_0 $$ Argyres-Douglas theory

This is the first in a series of two papers, in which we compute the third-order QCD corrections to top-antitop production near threshold in $\textit{e}$ $\textit{e}$ collisions. The present paper provides a detailed outline of the strategy of computation in the framework of non-relativistic effective theory and the threshold expansion, applicable more generally to heavy-quark pair production near threshold. It summarizes matching coefficients and potentials relevant to the next-to-next-to-next-to-leading order and ends with the master formula for the computation of the third-order Green function. The master formula is evaluated in part II of the series.

Germany

M. Beneke

Japan

Y. Kiyo

K. Schuller

Third-order correction to top-quark pair production near threshold. Part I. Effective theory set-up and matching coefficients

In left-right symmetric models, the Majorana coupling matrix, <italic>f</italic>, and hence the right-handed neutrino (RHN) mass matrix, admits eight solutions assuming the form of the Dirac coupling matrix is known. Additionally, the coupling matrix depends on the parity-breaking scale, <math altimg='si1.svg'><msub><mrow><mi>v</mi></mrow><mrow><mi>R</mi></mrow></msub></math>, as a new physics scale. RHNs being Majorana in nature can possess a transition magnetic moment (TMM). Neutrino magnetic moments are inherently related to neutrino masses, as neutrino masses imply neutrino magnetic moments. We study, along with small neutrino TMM, the heavy RHN transition magnetic moment contributions to muon <math altimg='si2.svg'><mi>g</mi><mo linebreak='goodbreak' linebreakstyle='after'>&#8722;</mo><mn>2</mn></math>, <math altimg='si3.svg'><msub><mrow><mo stretchy='false'>(</mo><mi>g</mi><mo linebreak='badbreak' linebreakstyle='after'>&#8722;</mo><mn>2</mn><mo stretchy='false'>)</mo></mrow><mrow><mi>&#956;</mi></mrow></msub></math> anomaly for all eight solutions of <italic>f</italic>. We find, of the eight solutions, only two solutions of <italic>f</italic> matrix contribute to the <math altimg='si3.svg'><msub><mrow><mo stretchy='false'>(</mo><mi>g</mi><mo linebreak='badbreak' linebreakstyle='after'>&#8722;</mo><mn>2</mn><mo stretchy='false'>)</mo></mrow><mrow><mi>&#956;</mi></mrow></msub></math> in the experimental predicted range. The range of <math altimg='si1.svg'><msub><mrow><mi>v</mi></mrow><mrow><mi>R</mi></mrow></msub></math> in these cases is found to be <math altimg='si4.svg'><mn>3.4</mn><mo>&#215;</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>3</mn></mrow></msup><mo linebreak='goodbreak' linebreakstyle='after'>&#8722;</mo><mn>1.5</mn><mo>&#215;</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>4</mn></mrow></msup></math> GeV. For a complimentary check, we also study TMM-induced neutrinoless double beta decay ( <math altimg='si5.svg'><mn>0</mn><mi>&#957;</mi><mi>&#946;</mi><mi>&#946;</mi></math>), for the same set of choice of parameters. While certain parameter choices allow RHNs to explain the <math altimg='si3.svg'><msub><mrow><mo stretchy='false'>(</mo><mi>g</mi><mo linebreak='badbreak' linebreakstyle='after'>&#8722;</mo><mn>2</mn><mo stretchy='false'>)</mo></mrow><mrow><mi>&#956;</mi></mrow></msub></math> anomaly, the same configurations lead to an extremely long half-life for <math altimg='si5.svg'><mn>0</mn><mi>&#957;</mi><mi>&#946;</mi><mi>&#946;</mi></math> decay, well beyond experimental reach. Even under extreme magnetic field enhancements, the half-life decreases only marginally, reinforcing the dominance of weak interaction vertices over TMM contributions in <math altimg='si5.svg'><mn>0</mn><mi>&#957;</mi><mi>&#946;</mi><mi>&#946;</mi></math> decay.

Vivek Banerjee

Sasmita Mishra

Magnetic moment of neutrinos in a left-right symmetric model and Interplay of type-I and type-II seesaw

In this work, we develop machine learning techniques to study nonperturbative scattering amplitudes. We focus on the two-to-two scattering amplitude of identical scalar particles and study a toy model where we set the double discontinuity to zero, thereby simplifying the problem numerically. Neural networks provide an efficient parameterization for scattering amplitudes, offering a flexible toolkit to describe the details of their nonperturbative structure. Combined with the bootstrap approach based on the dispersive representation of the amplitude and machine learning’s gradient descent algorithms, they offer a new method to explore the space of consistent S-matrices. We derive bounds on the values of the first two low-energy Taylor coefficients of the amplitude and characterize the resulting amplitudes that populate the allowed region. Crucially, we parallel our neural network analysis with the standard S-matrix bootstrap, both primal and dual, and observe perfect agreement across all approaches.

France

Mehmet Gümüş

Damien Leflot

Piotr Tourkine

Switzerland

Alexander Zhiboedov

The S-matrix bootstrap with neural optimizers. Part I. Zero double discontinuity

It is straightforward to take the gravitational wave solution to first order in <math altimg='si1.svg'><mi>v</mi><mo stretchy='false'>/</mo><mi>c</mi></math> far from a binary source in a Minkowski background and adapt it to the Friedmann-Lemaitre-Robertson-Walker (FLRW) background, representing an expanding isotropic and homogeneous universe. We find the analogous solution for a slightly anisotropic background, which may be a more accurate description of our late universe through which gravitational waves propagate, and implications from tight CMB anisotropy constraints may not necessarily determine the level of anisotropy in the late universe in light of modified gravity models as well as the Hubble tension. We use a perturbative form of the Bianchi I metric and demonstrate how the waveform differs. Using supernova anisotropy data as a reference, we show that the assumption of a Bianchi I background could imply on average a 2.1% difference in inferred luminosity distance compared to what would be inferred under the assumption of the FLRW background. This difference can be as high as 5.9% depending on the observation direction. Therefore, the background spacetime used for the inference of the Hubble parameter from gravitational wave data should be considered carefully.

United States

Kevin J. Ludwick

Peter L. Williams

Inferred Hubble parameter from gravitational waves in a perturbative Bianchi I background

<p>The femtoscopic <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>D</mi><mover accent="true"><mi>D</mi><mo stretchy="false">¯</mo></mover></math> correlation functions are investigated to predict the signature of the not-yet-established <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>X</mi><mo stretchy="false">(</mo><mn>3700</mn><mo stretchy="false">)</mo></math> state. Here it is interpreted as a bound state generated by solving the coupled-channel Bethe-Salpeter equations with the local hidden-gauge formalism. We prospect how the relevant properties and observables characterizing this state—like the pole position, scattering lengths and compositeness—might be affected by the variation of the parameters of the model. The amplitudes are then used as input into the momentum correlation functions of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>D</mi><mn>0</mn></msup><msup><mover accent="true"><mi>D</mi><mo stretchy="false">¯</mo></mover><mn>0</mn></msup></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>D</mi><mo>+</mo></msup><msup><mi>D</mi><mo>−</mo></msup></math> pairs. We discuss how their behaviors encode the features of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>X</mi><mo stretchy="false">(</mo><mn>3700</mn><mo stretchy="false">)</mo></math> state.</p>

Brazil

Luciano M. Abreu

Spain

Juan M. Torres-Rincon

Searching for femtoscopic signatures of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>D</mi><mover accent="true"><mi>D</mi><mo stretchy="false">¯</mo></mover></math> (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="normal">I</mi><mrow><mo>=</mo><mn>0</mn></mrow></mrow></math>), X(3700), bound state

We develop a formalism for computing the scattering amplitudes in maximally symmetric de Sitter spacetime with compact spatial dimensions. We describe quantum states by using the representation theory of de Sitter symmetry group and link the Hilbert space to “inertial” geodesic observers. The positive and negative “energy” wavefunctions are uniquely determined by the requirement that in observer's neighborhood, short wavelengths propagate as plane waves with positive and negative frequencies, respectively; they define a unique “Euclidean” (a.k.a. Bunch-Davies) de Sitter invariant vacuum, common to all inertial observers. By following the same steps as in Minkowski spacetime, we show that the scattering amplitudes are given by a generalized Dyson's formula. Compared to the flat case, they describe the scattering of wavepackets with the frequency spectrum determined by geometry. The frequency spread shrinks as the masses and/or momenta become larger than the curvature scale. Asymptotically, de Sitter amplitudes agree with the amplitudes evaluated in Minkowski spacetime.

Poland

Tomasz R. Taylor

United Kingdom

Bin Zhu

Scattering of quantum particles in global de Sitter spacetime I: The formalism

We consider a generic class of effective quantum field theories with arbitrary gauge groups and scalar matter fields. In such theories, we derive the one-loop Renormalization Group Equations (RGEs) for the physical dimension-six operators. The present paper is the first one in a series that is going to cover theories with spin- $$ \frac{1}{2} $$ matter fields, too, including the phenomenologically most relevant SMEFT and LEFT cases. Our present approach provides tools for deriving the yet unknown two-loop RGEs in the SMEFT.

Mikołaj Misiak

Ignacy Nałȩcz

One-loop renormalization group equations in generic effective field theories. Part I. Bosonic operators

The influence of a dark energy fluid on the equation of state of neutron stars is investigated. A detailed analysis is conducted for such models, including the computation of the moment of inertia, the quadrupole moment, and the tidal Love number. The results demonstrate that these quantities are interconnected through the well-known equation of state independent I-Love-Q relations. This work extends the applicability of these universal relations to a broader class of neutron star models.

Simone D’Onofrio

I-Love-Q relations for neutron stars with dark energy