In this Letter, we propose a stringy model for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>n</mi></mrow></math>-point tree-level form factor with the off-shell operator in the scalar and gluon theories from the bosonic string disk amplitude: <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>n</mi></math> open string states and one closed string state scatter on the disk. In the field-theory limit (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi>α</mi></mrow><mrow><mo>′</mo></mrow></msup><mo stretchy="false">→</mo><mn>0</mn></mrow></math>), the “stringy form factor” reduces to the form factor, which helps us to investigate the hidden properties of the field-theory form factors, manifest the factorization and soft behaviors, and uncover more nontrivial relations between form factors and scattering amplitudes.

China

Qu Cao

Form Factors from String Amplitudes

Based on Belle data, the structure around 1435 MeV and the role of the <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi mathvariant="normal">Σ</mi><mo>(</mo><mn>1380</mn><mo>)</mo></mrow></math> resonance in the decay process <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msub><mi mathvariant="normal">Λ</mi><mi>c</mi></msub><mo>→</mo><mi mathvariant="normal">Λ</mi><msup><mi>π</mi><mo>−</mo></msup><msup><mi>π</mi><mo>+</mo></msup><msup><mi>π</mi><mo>+</mo></msup></mrow></math> are investigated. The <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi mathvariant="normal">Λ</mi><msup><mi>π</mi><mo>±</mo></msup></mrow></math> invariant mass spectra are approximately reproduced by the contribution from the <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi mathvariant="normal">Σ</mi><mo>(</mo><mn>1385</mn><mo>)</mo></mrow></math>, modeled as a Breit-Wigner resonance combined with background. However, an additional contribution is required to account for the pronounced enhancement near 1435 MeV. To describe this structure, two scenarios are considered for the <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi mathvariant="normal">Σ</mi><mo>(</mo><mn>1435</mn><mo>)</mo></mrow></math>: one as a Breit-Wigner resonance with spin-parity <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mn>1</mn><mo>/</mo><msup><mn>2</mn><mo>−</mo></msup></mrow></math> described via effective Lagrangians, and the other as a rescattering effect arising from coupled-channel interactions. Specifically, the channels <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msup><mover accent="true"><mi>K</mi><mo>¯</mo></mover><mn>0</mn></msup><mi>p</mi></mrow></math>, <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msup><mi>π</mi><mn>0</mn></msup><msup><mi mathvariant="normal">Σ</mi><mo>+</mo></msup></mrow></math>, <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msup><mi>π</mi><mo>+</mo></msup><msup><mi mathvariant="normal">Σ</mi><mn>0</mn></msup></mrow></math>, <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msup><mi>π</mi><mo>+</mo></msup><mi mathvariant="normal">Λ</mi></mrow></math>, and <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>η</mi><msup><mi mathvariant="normal">Σ</mi><mo>+</mo></msup></mrow></math> are included for the positively charged mode, and <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msup><mi>K</mi><mo>−</mo></msup><mi>n</mi></mrow></math>, <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msup><mi>π</mi><mn>0</mn></msup><msup><mi mathvariant="normal">Σ</mi><mo>−</mo></msup></mrow></math>, <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msup><mi>π</mi><mo>−</mo></msup><msup><mi mathvariant="normal">Σ</mi><mn>0</mn></msup></mrow></math>, <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msup><mi>π</mi><mo>−</mo></msup><mi mathvariant="normal">Λ</mi></mrow></math>, and <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi>η</mi><msup><mi mathvariant="normal">Σ</mi><mo>−</mo></msup></mrow></math> for the negatively charged mode. The rescattering contributions are evaluated using the quasipotential Bethe-Salpeter equation approach. Simulated invariant mass spectra are generated and fitted to the experimental data. Both the Breit-Wigner and rescattering mechanisms provide reasonable descriptions of the enhancement near 1435 MeV. The rescattering approach naturally generates a cusp-like structure near threshold, which closely resembles the feature observed in the data. Furthermore, the inclusion of the <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mi mathvariant="normal">Σ</mi><mo>(</mo><mn>1380</mn><mo>)</mo></mrow></math> resonance with spin-parity <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><mn>1</mn><mo>/</mo><msup><mn>2</mn><mo>−</mo></msup></mrow></math> significantly improves the fit in the low-energy region and further enhances the description near 1435 MeV through interference effects. These results underscore the essential roles of the two <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msup><mi mathvariant="normal">Σ</mi><mo>*</mo></msup><mrow><mo>(</mo><mn>1</mn><mo>/</mo><msup><mn>2</mn><mo>−</mo></msup><mo>)</mo></mrow></mrow></math> states in accurately describing the invariant mass distributions in the decay <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msub><mi mathvariant="normal">Λ</mi><mi>c</mi></msub><mo>→</mo><mi mathvariant="normal">Λ</mi><msup><mi>π</mi><mo>+</mo></msup><msup><mi>π</mi><mo>+</mo></msup><msup><mi>π</mi><mo>−</mo></msup></mrow></math>.

Jun He

Role of <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msup><mi mathvariant="normal">Σ</mi><mo>*</mo></msup><mrow><mo>(</mo><mn>1</mn><mo>/</mo><msup><mn>2</mn><mo>−</mo></msup><mo>)</mo></mrow></mrow></math> baryons in <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msub><mi mathvariant="normal">Λ</mi><mi>c</mi></msub><mo>→</mo><mi mathvariant="normal">Λ</mi><msup><mi>π</mi><mo>+</mo></msup><msup><mi>π</mi><mo>+</mo></msup><msup><mi>π</mi><mo>−</mo></msup></mrow></math> decay

Consideration is being given to upgrading the SuperKEKB electron-positron collider with the introduction of electron-beam polarization. This would enable a unique precision electroweak physics program that opens new ways to search for physics beyond the Standard Model. The upgrade would enable Belle II to make a number of high precision measurements, one of which is the left-right cross-section asymmetry in the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup></mrow><mo stretchy="false">→</mo><mrow><msup><mi>e</mi><mo>+</mo></msup><msup><mi>e</mi><mo>−</mo></msup></mrow></math> Bhabha scattering process. The expected level of precision in such a measurement will require the theoretical values of the asymmetry to be calculated at least to the next-to-leading order (NLO) level, and the implementation of simulation event generators with a similar level of precision. In this study, we compare the calculations of the ReneSANCe Monte Carlo generator with those of an independent NLO calculation to determine the level of agreement in this process. An average difference of 0.3% between the calculations is found. Using the published Belle II efficiency for selecting Bhabha events and assuming a <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>40</mn><mtext> </mtext><mtext> </mtext><msup><mrow><mi>ab</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math> dataset having 70% polarization, the projected uncertainty on the weak mixing angle, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>sin</mi><mn>2</mn></msup><msub><mi>θ</mi><mi>W</mi></msub></math>, is calculated using ReneSANCe to be <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>±</mo><mn>0.00032</mn></math> or better. Combining this with left-right asymmetry measurements from muons and taus under the assumption of lepton universality yields a projected overall uncertainty of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>±</mo><mn>0.00019</mn></math> on <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>sin</mi><mn>2</mn></msup><msub><mi>θ</mi><mi>W</mi></msub></math> with SuperKEKB upgraded to have polarized electron beams.

Canada

C. Miller

J.M. Roney

Left-right asymmetry calculation comparisons and projected sensitivity to the weak mixing angle in polarized Bhabha scattering at 10.58 GeV

Nonlinear electrodynamics has been an important area of research for a long time. Investigations based on nonlinear Lagrangians, such as Euler–Heisenberg and Born–Infeld, are instrumental in exploring the limits of classical and quantum field theories, providing valuable insights into strong-field phenomena. In this context, this work considers how light propagates in strong-field environments, where such nonlinearities play significant roles, offering a way to investigate events in high-energy astrophysics, quantum optics, and fundamental physics beyond classical Maxwell’s framework. Here, several aspects of light propagation in nonlinear electrodynamics are discussed. Phase and group velocities are derived and several interesting behaviors are unveiled, such as birefringence, non-reciprocal propagation, and asymmetries between phase and group velocities in special configurations. Specific solutions based on commonly studied nonlinear theories are also investigated, and phenomena like slow-light and one-way propagation are discussed.

Brazil

T. Cruz

V. De Lorenci

E. Guzmán-Herrera

C. Ribeiro

Exploring light propagation in nonlinear electrodynamics: phase and group velocities and related phenomena

In this paper, we conduct a data-driven study of the production of softened hadrons and their contribution to the transverse momentum spectrum. To this end, we assume that the production of charged particles at soft and hard scales fundamentally results from the fragmentation of color strings. We analyze the $$\textit{p}_\text {T}$$ -spectrum data from pp to AA collisions at LHC energies reported by the ALICE Collaboration, finding that, in all cases, the data can be collapsed into a $$\textit{p}_\text {T}$$ -exponential trend in the range 1 GeV $$<\textit{p}_\text {T}<$$ 6 GeV. With this insight, the description of the $$\textit{p}_\text {T}$$ -spectrum should contain information on the charged particle production coming from two different sources: fragmentation of color strings and collective phenomena that redistribute the transverse momentum and enhance the production of particles at intermediate $$\textit{p}_\text {T}$$ . We also found different relations between the effective temperature, multiplicity, and average $$\textit{p}_\text {T}$$ for pp and AA collisions, indicating inherent dissimilarities between small and large colliding systems. In contrast, the contribution of the softened hadrons to the $$\textit{p}_\text {T}$$ -spectrum and average $$\textit{p}_\text {T}$$ collapse onto scaling laws. Our results show that the physical mechanisms producing softened hadrons have similar origins for all colliding systems, revealing a stronger dependence on freeze-out parameters rather than the system size.

Mexico

D. Herrera

J. García

A. Téllez

E. Cuautle

J. Ramírez

Scaling laws for softened hadron production at LHC energies

We investigate the identification of the Wess-Zumino-Witten (WZW) Lagrangian at colliders such as BESIII and the Super-$\textit{τ}$-Charm Facility. Our analysis concentrates on the radiative decays of $\textit{η}$ and $\textit{η}$ mesons, including $\textit{η}$ → $\textit{γγ}$, $\textit{η}$ → $\textit{γℓ}$ $\textit{ℓ}$ , $\textit{η}$ → $\textit{π}$ $\textit{π}$ $\textit{γ}$, and $\textit{η}$ → $\textit{π}$ $\textit{π}$ $\textit{ℓ}$ $\textit{ℓ}$ , as well as semileptonic kaon decays such as $\textit{K}$ → $\textit{π}$ $\textit{π}$ $\textit{ν}$ . Employing the hidden local symmetry framework to incorporate vector meson contributions, we compute the decay amplitudes and form factors. For the decay $\textit{η}$ → $\textit{π}$ $\textit{π}$ $\textit{γ}$, the box anomaly dominates, and we find that the anomalous coupling can be experimentally determined to percent-level precision at BESIII. In contrast, vector meson contributions are significant in the decay $\textit{η}$ → $\textit{π}$ $\textit{π}$ $\textit{γ}$. Using experimental data for $\textit{η}$ → $\textit{π}$ $\textit{π}$ $\textit{γ}$, we obtain $$ {\mathcal{B}}_{\textrm{box}}^{\textrm{exp}} $$ = (1.70 ± 0.05)%, which is approximately ten times larger than previously expected experimentally. We observe good agreement between our calculated anomalous couplings and experimental results. In kaon decays, WZW terms uniquely contribute to the form factor $\textit{H}$, which can be extracted from parity-conserving decay distributions. While predictions at the chiral point closely match experimental values (e.g., $\textit{H}$ = −2.31 versus −2.27 ± 0.10), we find that intermediate vector meson states introduce substantial corrections, potentially as large as 25%. We strongly advocate for revisiting these experiments to achieve improved precision in form factor extractions.

Chao-Qiang Geng

Chia-Wei Liu

Yue-Liang Wu

Identify hadron anomalous couplings at colliders

We explore constraints that arise from associating an entanglement wedge (EW) to subregions of a cutoff boundary at a finite distance in AdS/CFT, using a subcritical end-of-the-world (ETW) brane acting as a cutoff.

United States

Krishan Saraswat

Constraints from entanglement wedge nesting for holography at a finite cutoff

The hot and dense conditions of the supernova core provide an ideal environment for the production of new feebly-interacting particles. Low-energy supernovae, characterized by low explosion energy, are particularly intriguing due to their stringent constraints on energy transfer from the core to the mantle by new particles. We investigate low-energy supernova constraints on millicharged particles by considering three production channels in the core: plasmon decay, proton bremsstrahlung, and electron-positron annihilation. We compute the energy deposition due to Coulomb scatterings of millicharged particles with protons in the mantle and find that low-energy supernovae impose the most stringent constraints on millicharged particles in the mass range of ~ (12–170) MeV. Furthermore, we find that the electron-positron annihilation process, previously omitted in supernova studies on millicharged particles, is the dominant production channel in the high-mass region. This leads to new constraints from both supernova cooling calculations and low-energy supernova analyses. We also investigate MCP production via processes involving thermal pions and find that these processes could dominate over electron-positron annihilation, albeit with significant uncertainties.

Changqian Li

Zuowei Liu

Wenxi Lu

Zicheng Ye

Low-energy supernova constraints on millicharged particles

We calculate energy correlators in a general holographic model of confinement, involving an asymptotically anti-de Sitter (AdS) warped extra dimension. Building on a recent computation in a minimal hard-wall model of confinement, we show that the shockwave method for efficiently computing energy correlators in AdS generalizes to an arbitrary warped geometry. This is possible because exact, linear shockwave solutions to the 5D field equations exist in any warped background. We apply our formalism to compute the two-point energy correlator for two simple models of confinement with interesting infrared spectra — one with a gapped continuum spectrum and one with linear Regge trajectories. The results differ from the simple hard-wall model and from each other, demonstrating that the details of the confining dynamics affect the shape of the energy correlator observables.

Csaba Csáki

Steven Ferrante

Ameen Ismail

Holographic energy correlators for soft walls

Cosmic strings are powerful witnesses to cosmic events including any period of early matter domination. If such a period of matter domination was catalyzed by metastable, long-lived particles, then there will be complementary signals to ascertain the nature of the dark sector in experiments detecting primordial features in the gravitational wave (GW) power spectrum and laboratory searches for long-lived particles. We give explicit examples of global and local <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>U</mi><mo stretchy="false">(</mo><mn>1</mn><mo stretchy="false">)</mo></math> gauge extended dark sectors to demonstrate such a complementarity as the union of the two experiments reveals more information about the dark sector than either experiment. Demanding that Higgs-portal long-lived scalar be looked for, in various experiments such as DUNE, FASER, FASER-II, MATHUSLA, and SHiP, we identify the parameter space that leads to complementary observables for GW detectors such as the Laser Interferometer Space Antenna and Einstein Telescope.

Satyabrata Datta

India

Ambar Ghosal

Poland

Anish Ghoshal

United Kingdom

Graham White

Complementarity between cosmic string gravitational waves and long-lived particle searches in a laboratory