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

We discuss a novel UV completion of a class of Argyres-Douglas (AD) theories in the Ω-background by its embedding into the renormalisation group flow from five dimensional $$ \mathcal{N}=1 $$ superconformal field theories (SCFT) on $\textit{S}$ . This is obtained via analysing these theories in the light of ($\textit{q}$-)Painlevé/gauge theory correspondence, which allows to compute the five dimensional BPS partition functions as an expansion in the Wilson loop vev with integer $\textit{q}$-polynomials coefficients. These are derived formulating the gauge theory on a blown-up geometry and using a five-dimensional lift of (topological) operator/state correspondence. We discuss in detail the phase diagram of the four dimensional limits, pinpointing the special AD loci. Explicit computations are reported for $$ {\overset{\sim }{E}}_1 $$ SCFT and its limit to H = ($\textit{A}$ $\textit{, A}$ ) AD theory.

Italy

Giulio Bonelli

Pavlo Gavrylenko

Ideal Majtara

Alessandro Tanzini

On a 5D UV completion of Argyres-Douglas theories

Random tensor models can be used as combinatorial devices to generate Euclidean dynamical triangulations. A physical continuum limit of dynamical triangulations requires a suitable generalization of the double-scaling limit of random matrices. This limit corresponds to a fixed point of a pregeometric Renormalization Group flow in which the tensor size $\textit{N}$ serves as the Renormalization Group scale. We search for corresponding fixed points in order-4 random tensor models associated to dynamical triangulations in 4 dimensions. In a $\textit{O}$($\textit{N}$) symmetric setting, we discuss the resulting phase portrait as a function of the regulator parameters. We optimize our results, identifying parameter values for which the results are minimally sensitive to parameter changes. We find three fixed-point candidates: only one of them is real across the entire parameter range, but only has two relevant directions. This should be contrasted with the university class of the Reuter fixed point in continuum quantum gravity, very likely characterized by three relevant directions. We conclude that simple combinatorial models of Euclidean triangulations and the Reuter fixed point most likely lie in different universality classes.

Germany

Alicia Castro

Astrid Eichhorn

Razvan Gurau

Towards a quantitative characterization of gravitational universality classes for order-4 random tensor models

Quantifying the effects of finite temperature and density (FTD) on particle properties is essential for understanding phenomena within and beyond the Standard Model. In this work, we present a simplified framework for calculating particle production rates at FTD without resorting to a full thermal field theory calculation. We do so by relating the imaginary part of a particle’s $\textit{n}$-loop finite temperature self energy, which defines its in-medium damping rate, to a sum of thermally weighted tree-level vacuum rates. Such a mapping results in novel “interference” contributions to particle production which have no vacuum analog and which have been relatively overlooked in the phenomenology literature. These interference terms are known to regulate collinear and infrared divergences that arise when calculating interaction rates in a medium. We demonstrate the impact of these corrections with two toy models and find that properly accounting for these interference terms can alter particle production by an 𝒪(1) amount. We additionally compare the size of these corrections to the thermal mass corrections often studied in the literature, finding the sizes of these contributions to be of similar order.

Canada

Nirmalya Brahma

Saniya Heeba

Hugo Schérer

Katelin Schutz

Spectral Surgery in a Heat Bath: a finite-temperature guide to particle production for phenomenologists

<p>We use the light front quark model to investigate the form factors in the <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup><mo>→</mo><mi>B</mi><mover accent="true"><mi>B</mi><mo>¯</mo></mover></mrow></math> collision proceses with <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>B</mi><mo>=</mo><mi mathvariant="normal">Λ</mi><mo>,</mo><mspace width="4pt"></mspace><mi mathvariant="normal">Σ</mi></mrow></math> and <math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">Ξ</mi></math>. These form factor behaviors are calculated based on the Bethe-Salpeter formalism with <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msup><mi>q</mi><mo>+</mo></msup><mo>&gt;</mo><mn>0</mn></mrow></math> to effectively account for nonvalence contributions. We show that our results of the <math xmlns="http://www.w3.org/1998/Math/MathML"><msup><mi>q</mi><mn>2</mn></msup></math>-dependent form factors closely match the BESIII data. In particular, we obtain that <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mrow><mo>|</mo></mrow><msub><mi>G</mi><mi>eff</mi></msub><mrow><mo>|</mo><mo>=</mo><mo>(</mo></mrow><mn>0.921</mn><mo>,</mo><mspace width="0.16em"></mspace><mn>0.098</mn><mo>,</mo><mspace width="0.16em"></mspace><mn>0.189</mn></mrow></math>) and <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mrow><mi>R</mi><mo>=</mo><mo>|</mo></mrow><mfrac><msub><mi>G</mi><mi>E</mi></msub><msub><mi>G</mi><mi>M</mi></msub></mfrac><mrow><mo>|</mo><mo>=</mo><mrow><mo>(</mo><mn>0.97</mn><mo>,</mo><mspace width="0.16em"></mspace><mn>0.89</mn><mo>,</mo><mspace width="0.16em"></mspace><mn>0.936</mn><mo>)</mo></mrow></mrow></mrow></math> for <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup><mo>→</mo><mi mathvariant="normal">Λ</mi><mover accent="true"><mi mathvariant="normal">Λ</mi><mo>¯</mo></mover></mrow><mo>,</mo><mo> </mo><mrow><msup><mi mathvariant="normal">Σ</mi><mo>+</mo></msup><msup><mi mathvariant="normal">Σ</mi><mo>−</mo></msup><mo>,</mo><mspace width="0.16em"></mspace><msup><mi mathvariant="normal">Ξ</mi><mo>+</mo></msup><msup><mi mathvariant="normal">Ξ</mi><mo>+</mo></msup><mrow><mo>)</mo></mrow></mrow></math> with <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msup><mi>q</mi><mn>2</mn></msup><mo>=</mo><mrow><mo>(</mo><mn>5.74</mn><mo>,</mo><mspace width="0.16em"></mspace><mn>6.0</mn><mo>,</mo><mspace width="0.16em"></mspace><mn>7.0</mn><mo>)</mo></mrow><mspace width="0.16em"></mspace><msup><mrow><mi>GeV</mi></mrow><mn>2</mn></msup></mrow></math>.</p>

Chong-Chung Lih

Chao-Qiang Geng

Time-like electromagnetic form factors of <math xmlns="http://www.w3.org/1998/Math/MathML"><mi mathvariant="normal">Λ</mi><mo>,</mo><mo> </mo><mi mathvariant="normal">Σ</mi></math>, and <math xmlns="http://www.w3.org/1998/Math/MathML"><msup><mi mathvariant="normal">Ξ</mi><mo>+</mo></msup></math> in a light-front quark model

We study Higher-Spin Gravity in 4-dimensional (Anti-)de Sitter space, at leading order in the interactions (cubic vertices), in the AdS lightcone formalism developed by Metsaev. Using the vertices’ chiral structure, we extend the formalism into a broader class of lightcone frames, which allows for lightcones of bulk points. This enables us to write the lightcone theory in de Sitter space, where only these more general frames are available. It also allows us to formulate and verify (for the first time!) some causal properties of massless higher-spin interactions, involving lightcone foliations that share a lightray. These causal properties serve to both motivate and enable the computation of “static-patch scattering amplitudes” — the evolution of fields between the two horizons of the maximal observable region in de Sitter space. We present a computation scheme for such “amplitudes” in coordinate space, and in momentum space with spinor-helicity variables.

Jin Kozaki

Julian Lang

Yasha Neiman

Causality of higher-spin interactions on the (A)dS lightcone, with application to the static patch

In this paper, we determine the relativistic bound-state solutions for the Dirac oscillator (DO) in the curved spacetime of a cloud of strings in $$(3+1)$$ -dimensions, where such solutions are given by the four-component normalized Dirac spinor and by the relativistic energy spectrum. However, unlike literature, here, we work with the spacetime in two different forms/configurations, that is, both in its original form and in its modified form. To achieve our objective, we work with the curved DO in spherical coordinates, where we use the tetrad formalism. So, by defining a stationary ansatz for the spinor, we obtain two coupled first-order differential equations, and by substituting one equation into the other, we obtain a second-order differential equation. To analytically and exactly solve this differential equation, we use a change of function and of variable. From this, we obtain the well-known Whittaker equation, whose solution is the Whittaker function. Consequently, we obtain the energy spectrum, which is quantized in terms of the radial quantum number $\textit{n}$ and the angular quantum number $$\kappa $$ , and explicitly depends on the angular frequency $$\omega $$ (describes the DO), curvature parameter $\textit{a}$ (describes the cloud of strings), and on the effective rest mass $$m_{\text {eff}}$$ (describes the rest mass modified by the curvature of spacetime). Besides, we graphically analyze the behavior of the spectrum as a function of $$\omega $$ and $\textit{a}$ for three different values of $\textit{n}$ and $$\kappa $$ , as well as the behavior of the radial probability density for four different values of $$\kappa $$ , $$\omega $$ , and $\textit{a}$ (with $$n=0$$ ).

Brazil

R. Oliveira

The Dirac oscillator in the curved spacetime of a cloud of strings