We combine the recently introduced Non-Abelian Quasi-Particle Model (NAQPM) for gluons with an ideal Fermi gas of three quark species with the aim to describe the equation of state (energy density vs. temperature) of <math altimg='si7.svg'><mrow><mn>2</mn><mo linebreak='goodbreak'>+</mo><mn>1</mn></mrow></math> - flavour Lattice-QCD at zero chemical potential. Allowing temperature dependent masses for the fermions, we show that above a critical temperature <italic>T<inf>c</inf></italic> the quark mass has to drop rapidly in order to obtain energy density values compatible with the Lattice-QCD results. Within this framework, thus, the restoration of chiral symmetry in the system is observed. Furthermore, we demonstrate that the gluon variance &#8211;which is a fundamental quantity of the NAQPM&#8211; is strongly correlated to the fermion mass and decreases by orders of magnitude through the transition. The high temperature phenomenological characteristics of the gluon appear consistent to properties of the perturbative QCD gluon. The model indicates that color deconfinement and chiral symmetry restoration are interrelated and classical configurations of the QCD dynamics play an important role to the criticality of the system.

Greece

E.P. Politis

A. Tsapalis

F.K. Diakonos

Chiral transition in a non-abelian quasi-particle model with three quark flavours

We construct the graviton propagator in de Sitter space in a one-parameter family of non-covariant gauges. This family generalizes the simple gauge in which most graviton loop computations in de Sitter space have been performed. The resulting propagator has a relatively simple form and will facilitate checks of the gauge dependence of one-loop computations and proposed observables.

Czechia

Dražen Glavan

Graviton propagator in de Sitter space in a simple one-parameter gauge

The measurement of the Higgs self-coupling is considered the next milestone in the study of the Higgs boson properties. At future $\textit{e}$ $\textit{e}$ facilities below the double Higgs production threshold, this is extracted from the $\textit{Zh}$ production cross-section, which is sensitive to the trilinear coupling at the one-loop level. At the same perturbative order, potential effects beyond the Standard Model (SM) may affect the Higgstrahlung rate and distort the self-coupling determination. We study the question focusing especially on contact interactions containing two electron and two top-quark fields. We conclude that, in the context of FCC-ee and its planned runs at different energies, $\textit{eett}$ interactions change the Higgs self-coupling sensitivity below the percent level. Even in the most pessimistic scenarios, we confirm a robust sensitivity of the order of 17% at the 1$\textit{σ}$ confidence level under the assumption of otherwise SM-like Higgs couplings. A crucial role in these results is played by the measurement of fermion pair production above the $\textit{Z}$ resonance.

Germany

Lukas Allwicher

Christophe Grojean

Lucine Tabatt

Could electron-top interactions spoil the measurement of the Higgs trilinear? A quantitative estimate at future lepton colliders

Double parton distributions at small distances between the two partons are dominated by a mechanism in which the two observed partons originate from the splitting of a single parton. This contribution can be computed in terms of single-parton distributions and perturbative splitting kernels. We demonstrate that two-loop corrections to these kernels can have a substantial quantitative impact and considerably improve the stability of predictions for double parton scattering. We also consider the impact of heavy quark masses in the two-loop splitting kernels in an approximate manner.

Markus Diehl

Peter Plößl

A quantitative study of two-loop splitting in double parton distributions

Inflation generally assumes a field with nonzero potential that leads to inflationary expansion happening at arbitrarily early times. We demonstrate potentially observable consequences of inflation with a finite initial time in a model in five-dimensional warped anti-de Sitter space, with both a UV and an IR brane present during inflation. Considering an inflaton with an approximately flat potential localized on the UV brane, we derive the resulting brane motion in the bulk and the 4D effective action describing the dynamics. A concrete model allows us to evaluate possible consequences of a starting point of inflation. The background evolution is driven by the fast roll of the radion at early times and the slow roll of the inflaton at late times. We find that the action has the form of a two-field hyperbolic inflation model, the two fields being the radion and the inflaton, both of which have a time-dependent background solution. This setup is holographically dual to an inflaton coupled to a strongly coupled confining sector in which the ratio of the confinement scale to the 4D Planck scale evolves cosmologically. Focusing on the period when the equation of state becomes that of inflation, we find that the presence of the IR brane leads to deviations from the approximate de Sitter background in addition to those from the slow-roll parameters of the inflaton potential. We quantify the effect of the presence of the IR brane on the two point function of the adiabatic scalar perturbations and tensor perturbations. The dominant deviations occur at large scales: the adiabatic power spectrum has a blue tilt, while the tensor power spectrum shows oscillatory features. We present numerical fits to the shape of the adiabatic power spectrum, and discuss the implications for cosmic microwave background (CMB) analysis.

United States

Rashmish Mishra

Michael Nee

Lisa Randall

Inflation with a growing fifth dimension

This paper provides a comprehensive overview of neutrino masses and mixing in Large Extra Dimension scenarios, focusing on the phenomenological impact of a five-dimensional (5D) bulk fermion. In a flat extra dimension compactified on an $\textit{S}$ /ℤ orbifold, this fermion manifests as a Kaluza-Klein tower of right-handed neutrinos in the 4D effective theory. We systematically investigate four distinct scenarios for mass generation, considering both Dirac and Majorana mass terms originating from either the bulk or the 3-brane. For each case, we analyse the consequences for neutrino oscillations in a vacuum and in matter, deriving the resulting mass spectra and mixing patterns. By comparing these theoretical predictions with experimental data, we explore the constraints on the large extra dimensions’ parameters.

United Kingdom

Arturo Giorgi

Dhruv Pasari

Jessica Turner

Do neutrinos dream in 5D? Towards a comprehensive extra-dimensional neutrino phenomenology

We investigate the $$e^+ e^- \rightarrow \eta J/\psi $$ cross section by employing a model that combines relativistic Breit–Wigner amplitudes with a unitarized coupled-channel approach to account for resonant and non-resonant contributions, respectively. By performing a global fit to the BESIII experimental data, we determine the essential free parameters of the transition amplitudes. Furthermore, we analyze the role of a dynamically generated $$D\bar{D}^*$$ pole near 3.88 GeV and demonstrate its critical contribution to shaping the observed cross-section line shape.

Mexico

Sara Rahmani

Analysis of the $$e^+e^- \rightarrow \eta J/\psi $$ cross section within a unitarized coupled-channel approach

We present the derivation of an alternative representation of the real-time in-in formalism under a spatially homogeneous and time independent electric field. Because the system exhibits instability associated with pair production of particles and antiparticles, the perturbation theory should be reorganized depending on the choice of the reference vacuum. We recast the boundary wavefunctions into the quadratic self-energy-like terms in the functional integration formalism. The resulting generating functional in the modified in-in formalism leads to the propagators that resum infinite diagrams necessary to capture the vacuum-instability effects. The proper-time representations of the propagators reproduce the known expressions from the canonical operator formalism, but our derivation based on the generating functional along the closed-time path clarifies the origin of the additional proper-time contour and provides a better physical understanding. Finally, as a concrete example of the application, we compute the in-in expectation value of the vector current in a constant electric field, and find that the simple one-loop calculation captures the pair production effect.

Japan

Kenji Fukushima

Shuhei Minato

In-in formalism with resummation in a constant electric field: propagators including nontrivial boundary wavefunctions

We investigate the discovery potential of a vector-like top partner ($\textit{T}$) in the Type-II Two-Higgs-Doublet Model at a high-energy $$\mu p$$ collider through the charged-Higgs cascade $$\mu ^+ p \rightarrow \nu _\mu \,{\bar{b}} T \rightarrow \nu _\mu \,{\bar{b}} H^+ b$$ with $$H^+\rightarrow t{\bar{b}}$$ . The signal is characterized by four $\textit{b}$ jets, one charged lepton, and missing transverse energy. A detector-level analysis is performed for representative spectra with $$m_{H^\pm }\simeq 600$$ –650 GeV and $$m_T\simeq 1.2$$ –1.9 TeV. We find that a $$5\sigma $$ discovery is achievable for $$m_T\simeq 1.2$$ TeV at integrated luminosities of 100 and $$150~\textrm{fb}^{-1}$$ even in the presence of $$20\%$$ background systematics. For $$m_T\simeq 1.5$$ TeV, discovery remains possible for vanishing or moderate systematics, while heavier benchmarks require larger statistics and/or improved control of backgrounds.

Morocco

R. Benbrik

M. Berrouj

Poland

M. Boukidi

H. Chatoui

M. Ech-chaouy

K. Kahime

K. Salime

Single production of a vector-like top as a probe of charged higgs bosons at a muon–proton collider

We investigate the dynamics of massive test particles around a static black hole in nonlocal gravity and examine the corresponding properties of high-frequency quasi-periodic oscillations (HF QPOs), constraining the nonlocal parameter to $$\alpha /M \le 0.452$$ . We show that the nonlocal parameter $$\alpha $$ enhances the effective potential $$V_{\text {eff}}$$ and leads to a systematic reduction in the energy $$\mathcal {E}$$ and angular momentum $$\mathcal {L}$$ of circular orbits. Consequently, the innermost stable circular orbit (ISCO) radius, along with the associated energy and angular momentum, decreases monotonically with $$\alpha $$ , while the radiative efficiency increases, reaching a maximum of approximately $$8.9\%$$ . We further analyze the fundamental orbital frequencies of test particles and find that, due to the spherical symmetry of the spacetime, the Keplerian frequency $$\Omega _{\phi }$$ and the vertical epicyclic frequency $$\Omega _{\theta }$$ coincide and are suppressed by $$\alpha $$ , whereas the radial epicyclic frequency $$\Omega _{r}$$ is enhanced. The impact of $$\alpha $$ on several twin-peak HF QPO models is examined, revealing that $$\alpha $$ increases both the lower and upper bounds of the predicted QPO frequency ranges. By imposing the $$2\nu _U = 3\nu _L$$ resonance condition, we analyze the resonant radius, upper QPO frequency, maximum allowed black hole mass, and the time delay between the shadow and QPO signals. We find that the resonant radius decreases with $$\alpha $$ , while the upper QPO frequency increases, spanning the range $$\nu _U \sim (673/M$$ – $$4360/M)\textrm{Hz}$$ . When the Tolman–Oppenheimer–Volkoff limit is imposed, the upper frequency is further constrained to $$\nu _U \lesssim 1450$$ Hz. Combining astronomical observations for the classification of QPOs, where $$\nu _U \ge 100$$ Hz, the black hole mass in the nonlocal gravity should satisfy $$M \lesssim 43.6M_\odot $$ . Although the radial separation between the resonant radius and the photon sphere decreases with $$\alpha $$ , the associated gravitational time delay increases, remaining below $$\sim 1.3\textrm{ms}$$ and thus negligible for current observational capabilities.

China

Tao-Tao Sui

Chen Long

Ye Zhang

The properties and predictions of quasi-periodic oscillations around a black hole in nonlocal gravity