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

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

This study examines the black hole developed from multi-polytropic equations of state by investigating particle dynamics and various related properties, such as the radius of the horizon, the effective force, the innermost stable circular orbit radius, the photon radius, quasi-periodic oscillations, and the weak plasma lensing in uniform plasma fields, singular isothermal sphere (SIS), and non-singular isothermal gas sphere (NSIS). Furthermore, we examine the image magnification for the black hole solution. An important parameter in this black hole solution is $$c_1$$ , which significantly impacts the results. Our study shows that particle dynamics features and deflection of light are affected by the black hole parameter.

Azerbaijan

Pakistan

Allah Ditta

China

Farzan Mushtaq

Thailand

Phongpichit Channuie

Saudi Arabia

Awad Ibraheem

Asifa Ashraf

India

Rana Zulqarnain

Studying the properties of particle motion and plasma lensing in regular black holes from multi-polytropic equations of state

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.

Qu Cao

Form Factors from String Amplitudes

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

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

We introduce a new observable to probe the collective nature of the radial expansion of the quark-gluon plasma. This observable, dubbed <math altimg='si1.svg'><msub><mrow><mi>v</mi></mrow><mrow><mn>02</mn></mrow></msub><mo stretchy='false'>(</mo><msub><mrow><mi>p</mi></mrow><mrow><mi>T</mi></mrow></msub><mo stretchy='false'>)</mo></math>, represents the correlation of the spectrum with elliptic flow, in the same way as the recently measured <math altimg='si2.svg'><msub><mrow><mi>v</mi></mrow><mrow><mn>0</mn></mrow></msub><mo stretchy='false'>(</mo><msub><mrow><mi>p</mi></mrow><mrow><mi>T</mi></mrow></msub><mo stretchy='false'>)</mo></math> represents the correlation of the spectrum with the transverse momentum per particle. The advantage of <math altimg='si1.svg'><msub><mrow><mi>v</mi></mrow><mrow><mn>02</mn></mrow></msub><mo stretchy='false'>(</mo><msub><mrow><mi>p</mi></mrow><mrow><mi>T</mi></mrow></msub><mo stretchy='false'>)</mo></math> over <math altimg='si2.svg'><msub><mrow><mi>v</mi></mrow><mrow><mn>0</mn></mrow></msub><mo stretchy='false'>(</mo><msub><mrow><mi>p</mi></mrow><mrow><mi>T</mi></mrow></msub><mo stretchy='false'>)</mo></math> is that it is measured using a three-particle cumulant, as opposed to a pair correlation, which significantly reduces the sensitivity to nonflow effects. We predict non-trivial differences between <math altimg='si1.svg'><msub><mrow><mi>v</mi></mrow><mrow><mn>02</mn></mrow></msub><mo stretchy='false'>(</mo><msub><mrow><mi>p</mi></mrow><mrow><mi>T</mi></mrow></msub><mo stretchy='false'>)</mo></math> and <math altimg='si2.svg'><msub><mrow><mi>v</mi></mrow><mrow><mn>0</mn></mrow></msub><mo stretchy='false'>(</mo><msub><mrow><mi>p</mi></mrow><mrow><mi>T</mi></mrow></msub><mo stretchy='false'>)</mo></math> in semi-central Pb+Pb collisions at the Large Hadron Collider (LHC) on the basis of hydrodynamic simulations. A hint of these differences can be seen in the modification of <math altimg='si3.svg'><msub><mrow><mi>p</mi></mrow><mrow><mi>T</mi></mrow></msub></math> spectra observed by ALICE in event-shape-engineered events.

Tribhuban Parida

Poland

Rupam Samanta

France

Jean-Yves Ollitrault

Correlation between particle spectra and elliptic flow

The photoproduction of <math altimg='si1.svg'><mi>J</mi><mo stretchy='false'>/</mo><mi>&#968;</mi></math> meson off the nucleon is investigated using a dynamical model based on a Hamiltonian that describes the reaction mechanisms involving meson-exchange and direct <math altimg='si1.svg'><mi>J</mi><mo stretchy='false'>/</mo><mi>&#968;</mi></math>-radiation terms. Pomeron exchange is also included to account for the monotonically increasing high-energy behavior of the cross section. To explore the low-energy mechanism, we scrutinize the role of light-meson [ <math altimg='si2.svg'><msup><mrow><mi>&#960;</mi></mrow><mrow><mn>0</mn></mrow></msup><mo stretchy='false'>(</mo><mn>135</mn><mo stretchy='false'>)</mo></math>, <math altimg='si3.svg'><mi>&#951;</mi><mo stretchy='false'>(</mo><mn>548</mn><mo stretchy='false'>)</mo></math>, <math altimg='si4.svg'><msup><mrow><mi>&#951;</mi></mrow><mrow><mo>&#8242;</mo></mrow></msup><mo stretchy='false'>(</mo><mn>958</mn><mo stretchy='false'>)</mo></math>, <math altimg='si5.svg'><msub><mrow><mi>f</mi></mrow><mrow><mn>1</mn></mrow></msub><mo stretchy='false'>(</mo><mn>1285</mn><mo stretchy='false'>)</mo></math>] and charmonium-meson [ <math altimg='si27.svg'><msub><mrow><mi>&#951;</mi></mrow><mrow><mi>c</mi></mrow></msub><mo stretchy='false'>(</mo><mn>1</mn><mi>S</mi><mo stretchy='false'>)</mo></math>, <math altimg='si28.svg'><msub><mrow><mi>&#967;</mi></mrow><mrow><mi>c</mi><mn>0</mn></mrow></msub><mo stretchy='false'>(</mo><mn>1</mn><mi>P</mi><mo stretchy='false'>)</mo></math>, <math altimg='si29.svg'><msub><mrow><mi>&#967;</mi></mrow><mrow><mi>c</mi><mn>1</mn></mrow></msub><mo stretchy='false'>(</mo><mn>1</mn><mi>P</mi><mo stretchy='false'>)</mo></math>, <math altimg='si30.svg'><msub><mrow><mi>&#951;</mi></mrow><mrow><mi>c</mi></mrow></msub><mo stretchy='false'>(</mo><mn>2</mn><mi>S</mi><mo stretchy='false'>)</mo></math>, <math altimg='si10.svg'><msub><mrow><mi>&#967;</mi></mrow><mrow><mi>c</mi><mn>1</mn></mrow></msub><mo stretchy='false'>(</mo><mn>3872</mn><mo stretchy='false'>)</mo></math>] exchanges in the <italic>t</italic>-channel diagram. Most of the coupling constants are determined from the radiative decays of the <math altimg='si1.svg'><mi>J</mi><mo stretchy='false'>/</mo><mi>&#968;</mi></math> or the relevant charmonium mesons. The final <math altimg='si1.svg'><mi>J</mi><mo stretchy='false'>/</mo><mi>&#968;</mi></math>- <italic>N</italic> interaction is described by gluon-exchange and direct <math altimg='si11.svg'><mi>J</mi><mo stretchy='false'>/</mo><mi>&#968;</mi><mi>N</mi></math> coupling. The parameters of the Hamiltonian are fitted using the latest GlueX and <math altimg='si1.svg'><mi>J</mi><mo stretchy='false'>/</mo><mi>&#968;</mi></math>-007 experiments at the Jefferson Laboratory (JLab). We find that among the meson-exchange terms, the light mesons <math altimg='si3.svg'><mi>&#951;</mi><mo stretchy='false'>(</mo><mn>548</mn><mo stretchy='false'>)</mo></math> and <math altimg='si4.svg'><msup><mrow><mi>&#951;</mi></mrow><mrow><mo>&#8242;</mo></mrow></msup><mo stretchy='false'>(</mo><mn>958</mn><mo stretchy='false'>)</mo></math> make the most significant contributions to <math altimg='si12.svg'><mi>&#947;</mi><mi>p</mi><mo stretchy='false'>&#8594;</mo><mi>J</mi><mo stretchy='false'>/</mo><mi>&#968;</mi><mi>p</mi></math>, while the effect of charmonium mesons is relatively minor. The final-state interaction (FSI) contribution is found to be 1 - 2 orders of magnitude smaller than that of the Born term, but becomes significant near the threshold when a Yukawa-type potential is employed for the charmonium-nucleon interaction. The resulting total and <italic>t</italic>-dependent differential cross sections show good agreement with the JLab data. High-precision angular measurements near the threshold energy ( <math altimg='si13.svg'><msub><mrow><mi>E</mi></mrow><mrow><mi>&#947;</mi></mrow></msub><mo>&#10877;</mo><mn>8.9</mn></math> GeV) are highly desirable to clarify the role of the FSI term.

South Korea

Sang-Ho Kim

<italic>J</italic>/ <italic>&#968;</italic>-meson photoproduction off the nucleon in a dynamical model

In this paper, we investigate pure geometric <math altimg='si1.svg'><mi>f</mi><mo stretchy='false'>(</mo><mi>R</mi><mo stretchy='false'>)</mo></math> cosmology branes embedded in five-dimensional spacetime. The form of <math altimg='si1.svg'><mi>f</mi><mo stretchy='false'>(</mo><mi>R</mi><mo stretchy='false'>)</mo></math> is chosen as a polynomial. The Five-dimensional scalar curvature <italic>R</italic> is assumed to be constant. Based on the value of the four-dimensional cosmological constant <math altimg='si2.svg'><msub><mrow><mi>&#955;</mi></mrow><mrow><mn>4</mn></mrow></msub></math>, the branes can be classified into Minkowski, de Sitter, and de anti-de Sitter cases. Solutions for each case can be calculated. These solutions are stable against linear tensor perturbations in all cases. In the Minkowski brane case, the zero mode of gravity can be localized on the brane. In the de Sitter brane case, the zero mode and one massive Kaluza-Klein mode can be localized on the brane. In the anti-de Sitter brane case, all massive Kaluza-Klein modes can be localized on the brane. The results of the analysis of tensor fluctuations are the same in both the Einstein frame and the Jordan frame.

Heng Guo

Cai-Ling Wang

Yong-Tao Lu

Yue Sun

Lang-Lang Wang

Pure geometric <italic>f</italic>( <italic>R</italic>) branes

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