We interpret the Euclidean solution of JT de Sitter gravity as the Coleman-de Luccia instanton for the decay of the low-entropy horizon of its static patch solution into either a Big Crunch or an infinite-entropy Lorentzian de Sitter cosmology. As in previous work by one of the authors, the Big Crunch is interpreted as bounding the entropy of the static state. The principle of detailed balance then guarantees it will transition back to a higher entropy causal diamond in the expanding cosmology. We then construct a family of explicit quantum mechanical models and appropriate metastable states, with transition probabilities well approximated by the semi-classical calculations in JT de Sitter gravity.

United States

Tom Banks

Sidan A

JT de Sitter gravity as a model of Coleman-de Luccia tunneling

We report a feasibility study of the hyperon semileptonic decay $$\varLambda \rightarrow pe^{-} {\bar{\nu }}_{e}$$ by using a fast simulation software package at STCF. With an anticipated integrated luminosity of 3.4 trillion $$J/\psi $$ per year at a center-of-mass energy of 3.097 GeV, the statistical sensitivity of the branching fraction is determined to be 0.15%. The statistical sensitivities of form factors $$g_{av}$$ and $$g_w$$ are determined to be 0.4% and 2.15%, respectively. The projected sensitivity of $$|V_{us}|$$ is obtained by combining this result with $$g_1(0)$$ from Lattice QCD, to be 0.9%, including the systematic uncertainty from the LQCD input and the statistical uncertainties of input branching fraction and form factors. The precise measurement to be obtained at STCF will provide a rigorous test of the Standard Model.

China

Junxian Zhou

Shun Wang

Tao Luo

Xiaorong Zhou

Prospects of $$|V_{us}|$$ and axial vector form factors in $$\varLambda \rightarrow pe^{-}{\bar{\nu }}_{e}$$ decay at STCF

Light scalars that couple to leptons are common figures in beyond the Standard Model endeavors. Considering a scalar that has universal and couplings to leptons only, we compute this leptophilic scalar contribution to the $$e^{-}e^{+} \rightarrow \tau ^{+}\tau ^{-} S $$ production cross section with $$S \rightarrow e^{+}e^{-}(\mu ^{+}\mu ^{-})$$ . We later compare the expected signal with recent data from the BELLE collaboration collected near the resonance $$\Upsilon (4S)$$ with $$\mathscr {L}=626 fb^{-1}$$ of integrated luminosity to place limits on the couplings-mass plane for the 4 MeV-6.5 GeV mass range. We then extended this analysis to a more general one $$e^{-}e^{+} \rightarrow {\ell }^{+}{\ell }^{-} S$$ production cross section where $$\ell =e,\mu ,\tau $$ with $$S \rightarrow e^{+}e^{-}(\mu ^{+}\mu ^{-})$$ , showing that BELLE constitutes an excellent laboratory for light scalars, where can be derived constraints stronger than those derived stemming from the g-2 of the electron or muon.

Brazil

D. Cogollo

Chile

Y. Oviedo-Torres

Farinaldo Queiroz

France

Yoxara Villamizar

J. Zamora-Saa

Search for sub-GeV scalars in $$e^+e^-$$ collisions

In the present work, we perform a combined analysis of the cross sections for $$e^+ e^- \rightarrow K^+ K^-$$ and $$e^+ e^- \rightarrow K_S^0 K_L^0$$ by including the interference between direct coupling process and resonance intermediate process. When setting the isospin factor as a free parameter, we can well reproduce the structures in the cross sections for $$e^+ e^- \rightarrow K^+ K^-$$ and $$e^+ e^- \rightarrow K_S^0 K_L^0,$$ however, the isospin factor deviates with the isospin symmetry conservation predicted value of one. By fixing the isospin factor to be one, we find the cross sections for $$e^+ e^-\rightarrow K^+ K^-$$ can be accurately fitted, while the same model parameters fail to adequately reproduce the observed cross section for the process $$e^+ e^- \rightarrow K_S^0 K_L^0,$$ which indicate that there should be contributions from other vector meson states, such as $$\rho (2150)$$ and $$\omega (2220).$$ The combined analysis with $$\phi (2170),$$ $$\omega (2220)$$ and $$\rho (2150)$$ indicate that the inclusion of $$\rho (2150)$$ can improve the descriptions of the cross sections for $$e^+ e^-\rightarrow K^+ K^-$$ and $$e^+ e^- \rightarrow K_S^0 K_L^0.$$

Dian-Yong Chen

Jing Liu

Yu Bai

Chun-Hua Liu

Wen-Biao Yan

Zhao-Xia Meng

A combined analysis of $\textit{Y}$(2240) in the $$e^+ e^- \rightarrow K^+ K^-$$ and $$e^+ e^- \rightarrow K_S^0 K_L^0$$ processes

The proposed <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> collider offers an ideal environment for precise estimation of Higgs boson properties which are of utmost importance to validate the Standard Model of particle physics. We investigate <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>h</mi><mi>V</mi><mi>V</mi></math> couplings, where <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>V</mi><mo>∈</mo><mo stretchy="false">{</mo><mi>Z</mi><mo>,</mo><mi>γ</mi><mo stretchy="false">}</mo></math> with single Higgs production associated with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>Z</mi></math> boson at the proposed <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> machine with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>250</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>, within the Standard Model effective field theory framework. We employ the recoil mass of the dilepton system, to select the signal phase space, i.e, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>Z</mi><mi>h</mi><mo stretchy="false">→</mo><msup><mi>l</mi><mo>+</mo></msup><msup><mi>l</mi><mo>−</mo></msup><mi>b</mi><mover accent="true"><mi>b</mi><mo stretchy="false">¯</mo></mover></math> events. The constraints on the Wilson coefficients (WCs) are obtained using the optimal observable technique. On comparison with the current experimental limits at 68% CL with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>138</mn><mtext> </mtext><mtext> </mtext><msup><mi>fb</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup></math> luminosity, our limits are tighter by a factor ranging from 1.5–10 for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>C</mi><mi>P</mi></mrow></math>-even operators, while <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>C</mi><mi>P</mi></mrow></math>-odd WCs shows comparable limits.

India

Subhaditya Bhattacharya

Amir Subba

Abhik Sarkar

Optimal estimation of Higgs-gauge boson couplings at the future <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> colliders

In this study, we investigate the inflationary dynamics of Rainbow <italic>f</italic>( <italic>R</italic>) gravity characterized by <italic>f</italic>( <italic>R</italic>)&#8239;&#8771;&#8239; <italic>&#945;Rn</italic>, with the rainbow deformation <math altimg='si8.svg'><mrow><mover accent='true'><mi>f</mi><mo>&#732;</mo></mover><mrow><mo>(</mo><mi>H</mi><mo>)</mo></mrow><mo>&#8764;</mo><msup><mi>H</mi><mi>&#955;</mi></msup></mrow></math> and <math altimg='si9.svg'><mrow><mover accent='true'><mi>g</mi><mo>&#732;</mo></mover><mo linebreak='goodbreak'>=</mo><mn>1</mn></mrow></math>. The effects of the rainbow parameter <italic>&#955;</italic> and the curvature exponent <italic>n</italic> on inflationary observables are analyzed under the Atacama Cosmology Telescope (ACT) constraint 0.9709&#8239;&lt;&#8239; <italic>n<inf>s</inf></italic>&#8239;&lt;&#8239;0.9777. Numerical results reveal a clear correlation among <italic>n, &#955;</italic>, and the tensor-to-scalar ratio <italic>r</italic>, such that decreasing <italic>n</italic> corresponds to increasing <italic>&#955;</italic>, accompanied by a growth in <italic>r</italic> within observational limits. Negative values of <italic>&#955;</italic> (typically for <italic>n</italic>&#8239;&#8776;&#8239;3) yield a quasi&#8211;de Sitter inflationary phase with a nearly constant Hubble parameter and suppressed tensor modes, while positive <italic>&#955;</italic> (for <italic>n</italic>&#8239;&#8818;&#8239;2.2) drive a quintessence&#8211;like inflationary regime with enhanced expansion and a time-dependent curvature. Using power&#8211;law solutions <italic>a</italic>( <italic>t</italic>)&#8733; <italic>tp</italic>, we relate the expansion exponent to the number of <italic>e</italic>-folds <italic>N</italic>&#8239;&#8771;&#8239;50&#8211;60. Small deviations between the matter and effective equations of state indicate a mild breaking of <math altimg='si10.svg'><mrow><msub><mi>w</mi><mi>e</mi></msub><mo linebreak='goodbreak'>=</mo><mi>w</mi></mrow></math>, suggesting the emergence of matter&#8211;like behavior within the quintessence&#8211;like inflationary field. At low curvature, we further show that a logarithmic Nojiri&#8211;Odintsov correction <italic>f</italic>( <italic>R</italic>)&#8239;&#8771;&#8239; <italic>&#945;</italic>&#8242;ln&#8201;( <italic>R</italic>/ <italic>&#956;</italic> 2) naturally dominates the dynamics, giving rise to a late&#8211;time quintessence phase ( <math altimg='si11.svg'><mrow><mo>&#8722;</mo><mn>1</mn><mo linebreak='goodbreak'>&lt;</mo><msub><mi>w</mi><mi>e</mi></msub><mo linebreak='goodbreak'>&lt;</mo><mo>&#8722;</mo><mn>1</mn><mo linebreak='goodbreak'>/</mo><mn>3</mn></mrow></math> for <math altimg='si12.svg'><mrow><mi>&#955;</mi><mo linebreak='goodbreak'>&gt;</mo><mo>&#8722;</mo><mn>1</mn></mrow></math>) that asymptotically approaches a de Sitter attractor ( <math altimg='si13.svg'><mrow><msub><mi>w</mi><mi>e</mi></msub><mo>&#8594;</mo><mo>&#8722;</mo><mn>1</mn></mrow></math> as &#1013; <inf>1</inf>&#8239;&#8594;&#8239;0 or <math altimg='si14.svg'><mrow><mi>&#955;</mi><mo linebreak='goodbreak'>=</mo><mo>&#8722;</mo><mn>1</mn></mrow></math>). Thus, the combined <italic>Rn</italic> and logarithmic contributions provide a unified geometric framework in which early&#8211;time inflation and late&#8211;time cosmic acceleration naturally arise from different curvature regimes of Rainbow <italic>f</italic>( <italic>R</italic>) gravity, consistent with ACT observational data.

Türkiye

A.I. Keskin

Rainbow <italic>f</italic>( <italic>R</italic>) Inflation: de Sitter-Quintessence Phases

The proposed Large Hadron electron Collider (LHeC), with a center-of-mass energy of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msqrt><mi>s</mi></msqrt><mo>≈</mo><mn>1.3</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></math>, provides a clean and sensitive environment to probe the top quark’s neutral current interactions with the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>Z</mi></math> boson via <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>e</mi><mo>−</mo></msup><mi>p</mi><mo stretchy="false">→</mo><msup><mi>e</mi><mo>−</mo></msup><mi>t</mi><mover accent="true"><mi>t</mi><mo stretchy="false">¯</mo></mover></math>. We investigate the precision with which the Standard Model (SM) <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>t</mi><mover accent="true"><mi>t</mi><mo stretchy="false">¯</mo></mover><mi>Z</mi></math> couplings—the vector and axial-vector components (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Δ</mi><msub><mi>C</mi><mrow><mn>1</mn><mi>V</mi></mrow></msub><mo>,</mo><mi mathvariant="normal">Δ</mi><msub><mi>C</mi><mrow><mn>1</mn><mi>A</mi></mrow></msub></math>) can be measured, along with possible new physics effects parametrized by higher-dimensional operators inducing weak electric and magnetic dipolelike interactions (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>C</mi><mrow><mn>2</mn><mi>V</mi></mrow></msub><mo>,</mo><msub><mi>C</mi><mrow><mn>2</mn><mi>A</mi></mrow></msub></math>). Focusing on the semileptonic decay channel, where either the top quark decays leptonically to a positively charged lepton (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mo>ℓ</mo><mo>+</mo></msup><mo>=</mo><msup><mi>e</mi><mo>+</mo></msup><mo>,</mo><msup><mi>μ</mi><mo>+</mo></msup></math>) and the antitop hadronically, or vice versa, we utilize the azimuthal angle difference <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Δ</mi><msub><mi>ϕ</mi><mrow><msup><mi>e</mi><mo>−</mo></msup><msup><mo>ℓ</mo><mo>±</mo></msup></mrow></msub></math> between the scattered electron and the charged lepton <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mo>ℓ</mo><mo>±</mo></msup></math> as the key observable to derive projected constraints. Using a one-parameter multibin <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>χ</mi><mn>2</mn></msup></math> analysis of the differential <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Δ</mi><msub><mi>ϕ</mi><mrow><msup><mi>e</mi><mo>−</mo></msup><msup><mo>ℓ</mo><mo>±</mo></msup></mrow></msub></math> distribution, the constraints on <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Δ</mi><msub><mi>C</mi><mrow><mn>1</mn><mi>A</mi></mrow></msub></math> improve from <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">O</mi><mo stretchy="false">(</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>1</mn></mrow></msup><mo stretchy="false">)</mo></math> at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>50</mn><mtext> </mtext><mtext> </mtext><msup><mi>fb</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup></math> to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">O</mi><mo stretchy="false">(</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>2</mn></mrow></msup><mo stretchy="false">)</mo></math> at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>1000</mn><mtext> </mtext><mtext> </mtext><msup><mi>fb</mi><mrow><mo>−</mo><mn>1</mn></mrow></msup></math>, while the improvement for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Δ</mi><msub><mi>C</mi><mrow><mn>1</mn><mi>V</mi></mrow></msub></math> remains within the same order of magnitude, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">O</mi><mo stretchy="false">(</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>1</mn></mrow></msup><mo stretchy="false">)</mo></math>. These results correspond to average relative precisions of approximately 8% and 68%, respectively, with respect to their SM values. The anomalous tensor couplings <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>C</mi><mrow><mn>2</mn><mi>V</mi></mrow></msub></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>C</mi><mrow><mn>2</mn><mi>A</mi></mrow></msub></math> are constrained at the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">O</mi><mo stretchy="false">(</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>1</mn></mrow></msup><mo stretchy="false">)</mo></math> level even at low luminosity and improve moderately with increasing luminosity. While the two-parameter analysis broadens the allowed regions due to parameter correlations, it maintains competitive sensitivity, particularly for the SM-like couplings. Throughout, we assume a systematic uncertainty of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>δ</mi><mi>s</mi></msub><mo>=</mo><mn>5</mn><mo>%</mo></math> in all analyses, and all results are quoted at the 95% confidence level. These results demonstrate the LHeC’s potential to provide complementary and competitive sensitivity to top-<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>Z</mi></math> couplings compared to current and future hadron and lepton collider capabilities.

South Africa

Katlego Machethe

Pramod Sharma

Mukesh Kumar

Rafiqul Rahaman

Bruce Mellado

Analyzing <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>t</mi><mover accent="true"><mi>t</mi><mo stretchy="false">¯</mo></mover><mi>Z</mi></math>-couplings at the future <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>e</mi><mo>−</mo></msup><mi>p</mi></math> collider

We investigate the relationship between thermodynamic phase transitions and the Lyapunov exponent of charged regular anti-de Sitter black holes in quasi-topological gravity. Our results show that the Lyapunov exponent displays multivalued behavior during phase transitions. Moreover, along the coexistence curve the Lyapunov exponent changes discontinously and continuously at the critical point. Near the critical point, the Lyapunov exponent follows a power-law behavior with a critical exponent of 1/2, suggesting its role as an order parameter and encodes information on black hole phase transitions.

Hao Xie

Si-Jiang Yang

Probing phase transitions of regular black holes in anti-de Sitter space with Lyapunov exponent

We consider soft graviton scattering for a theory where Einstein’s gravity is minimally coupled to a scalar field in the presence of a cosmological constant, i.e. in a background de Sitter space. Employing a perturbative expansion in a small cosmological constant, we compute leading, subleading and sub-subleading corrections to Weinberg’s soft graviton amplitude for the tree-level scatterings in the static patch of de Sitter space. We observe similar universal features of the soft graviton amplitude as found in (2023) 055 for the soft photons.

Divyesh Solanki

Pratik Chattopadhyay

Srijit Bhattacharjee

Perturbative soft graviton theorems in de Sitter spacetime

We perform the first computation of phase-transition parameters to cubic order in $ \lambda\sim m^2/T^2 $ , where $\textit{m}$ is the scalar mass and $\textit{T}$ is the temperature, in a simple model resembling the Higgs sector of the SMEFT. We use dimensional reduction, including 1-loop matching corrections for terms of dimension 6 (in 4-dimensional units), 2-loop contributions for dimension-4 ones and 3-loops for the squared mass. We precisely quantify the size of the different corrections, including renormalization-group running as well as quantum effects from light fields in the effective theory provided by the Coleman-Weinberg potential, and discuss briefly the implications for gravitational waves. Our results suggest that, for strong phase transitions, 1-loop corrections from dimension-6 operators can compete with 2-loop ones from quartic couplings and largely surpass those from 3-loop thermal masses.

Spain

Mikael Chala

Luis Gil

Zhe Ren

Phase transitions in dimensional reduction up to three loops * Supported by MCIN/AEI (10.13039/501100011033) and ERDF (grants PID2021-128396NB-I00 and PID2022-139466NB-C22), from the Junta de Andalucía grants FQM 101 and P21-00199 and from Consejería de Universidad, Investigación e Innovación, Gobierno de España and Unión Europea – NextGenerationEU under grants AST22 6.5 and CNS2022-136024. MC and LG are further supported by the RyC and FPU programs under contract numbers RYC2019-027155-I and FPU23/02026, respectively.