In this study, we investigate the possibility of enhancing the di-jet resonance searches by tagging the final state radiation (FSR) jet using an event-level deep neural network. It is found that solely relying on the 4-momenta of the leading three jets allows the algorithm to achieve good discriminating power that can identify the hardest FSR jet in the signal while rejecting other soft jets. Once the invariant mass is corrected with the tagged FSR jet, the mass resolution of the signal is greatly enhanced, and the sensitivity of the search is also improved by more than 10%. By crafting the input variables carefully, the algorithm introduces minimal mass sculpting for the background, and its applicability extends to a broad mass range. This work proves that FSR jet tagging can potentially enhance di-jet resonance searches, suiting various stages of the physics programmes at the Large Hadron Collider (LHC) and High-Luminosity LHC (HL-LHC).

China

Bingxuan Liu

Yuxuan Shen

Yuanshunzi Sui

Enhancing di-jet resonance searches via a final-state radiation jet tagging algorithm * Bingxuan Liu is supported by Shenzhen Campus of the Sun Yat-sen University under project 74140-12255011, and by the Young Scientists Fund (C Class) of the National Natural Science Foundation of China (12405122). Both Yuxuan Shen and Yuanshunzi Sui are supported by College Students’ Innovative Entrepreneurial Training Plan Program

This study presents a detailed investigation of the dynamics of massless test particles (photons) to analyze the stability of null circular geodesics around the Kerr–Sen black hole (KSBH) spacetime. KSBH is a new solution arising in the low-energy effective field theory of heterotic string theory. The analysis proceeds by obtaining the radial effective potential, which serves as the foundation for calculating the Lyapunov exponent, a central quantity used to describe the stability or instability of geodesic motion in dynamical systems. The study employs the Lyapunov exponent approach to determine the stability or instability of circular orbits under varying values of the charge parameter $\textit{Q}$ and Kerr parameter $\textit{a}$. Additionally, the analytical expressions for the radius of circular photon orbits and the corresponding impact parameter, defined as the ratio of conserved angular momentum to energy are also derived explicitly. To further analyze the orbital behavior, techniques such as Poincaré maps, the Lyapunov Exponent, and FLI are utilized to distinguish between regular and chaotic trajectories. The sign and magnitude of the Lyapunov exponent provide a rigorous criterion to distinguish between stable and unstable circular orbits. These results contribute to a deeper understanding of the geodesic structure and perturbative stability in string-inspired rotating charged black hole backgrounds. The findings are also compared with those of the KBH case to highlight the impact of the BH charge on the stability of null geodesics. This study provides deeper insights into the dynamical properties of null geodesics in charged rotating BH spacetimes in GR and alternative theory of gravity.

India

Pradeep Singh

Hemwati Nandan

Shubham Kala

Nidhi Handa

Lokesh Joshi

Azerbaijan

G. Mustafa

Probing strong-gravity chaos and stability of circular photon orbits around the Kerr–Sen black hole

<p>Four-derivative heterotic supergravity (without gauge fields) reduced on a <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>p</mi></math>-dimensional torus leads to half-maximal supergravity coupled to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>p</mi></math> vector multiplets, and it is known that removing the vector multiplets is a consistent truncation of the theory. We find a new consistent truncation of four-derivative heterotic supergravity on a torus that keeps the vector multiplets and precisely reproduces the bosonic action of heterotic supergravity (with heterotic gauge fields). We show that both truncations have an <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>O</mi><mo stretchy="false">(</mo><mi>d</mi><mo>+</mo><mi>p</mi><mo>,</mo><mi>d</mi><mo stretchy="false">)</mo></math> symmetry when reduced on a <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>d</mi></math>-dimensional torus and demonstrate how this embeds in the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>O</mi><mo stretchy="false">(</mo><mi>d</mi><mo>+</mo><mi>p</mi><mo>,</mo><mi>d</mi><mo>+</mo><mi>p</mi><mo stretchy="false">)</mo></math> symmetry that one gets from reducing on a (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>d</mi><mo>+</mo><mi>p</mi></mrow></math>)-dimensional torus without truncation. We then use our new truncation to obtain four-derivative corrections to the Kerr-Sen solution and compute thermodynamic quantities and multipole moments. Finally, we compare the Kerr-Sen solutions of the actions corresponding to the two different choices of truncation with the Kerr solution, the Kerr-Newman solution, and each other, and show that they have distinct four-derivative multipole structures.</p>

Minghao Xia

Liang Ma

Yi Pang

Robert J. Saskowski

Consistent four-derivative heterotic truncations and the Kerr-Sen solution

We obtain the four-derivative corrections to the Kerr-Sen solution in heterotic supergravity, which includes the Gibbons-Maeda-Garfinkle-Horowitz-Strominger solution as a limiting case. In particular, we first embed the Kerr solution into heterotic supergravity and compute the higher-derivative corrections. We then obtain the corrections to the Kerr-Sen solution by performing an $\textit{O}$(1, 2) boost of the Kerr solution, which, in contrast to the two-derivative case, requires field redefinitions to make the $\textit{O}$(1, 2) invariance of the action manifest. Finally, we compute the multipole moments and find that they are distinct from those of the Kerr solution at the four-derivative level. We also find that the multipole moments are distinct from those of the Kerr-Newman solution in Einstein-Maxwell theory at the four-derivative level, even for the most general choice of four-derivative corrections. This gives a way to experimentally distinguish traces of string theory in gravitational wave data.

Peng-Ju Hu

Robert Saskowski

Higher-derivative heterotic Kerr-Sen black holes

The 2HDM+S is the singlet extension of the two-Higgs-doublet model (2HDM). The singlet field and its mixing with the 2HDM Higgs sector lead to new contributions to the electroweak precision observables, in particular, the oblique parameters. In this study, we performed a systematic investigation of the impacts of each mixing angle on the oblique parameters. We adopted the mixing angles and physical Higgs masses as our parameters, which allow a mapping when a specific symmetry structure of the Higgs potential and various theoretical considerations are taken into account. We identified five benchmark cases, where at most one mixing angle was nonzero, and analyzed the 95% C.L. allowed parameter space using the oblique parameters. In the alignment limit of the 2HDM, we find that, other than the usual mass relations of $m_H\sim m_{H^\pm}$ or $m_A\sim m_{H^\pm}$ , electroweak precision measurements also impose an upper limit on the neutral Higgs masses. In the cases with nonzero singlet mixing with the 2HDM Higgses $\textit{H}$ or $\textit{A}$, we find approximate mass relations of $c^2_{\alpha_{HS}} m_{H} + s^2_{\alpha_{HS}}m_{h_S} = m_{H^\pm}$ or $c^2_{\alpha_{AS}} m_{A} + s^2_{\alpha_{AS}}m_{A_S} = m_{H^\pm}$ . These relations are universal to the 2HDM+S models, with or without further symmetry assumption. We also studied the non-alignment limit of the 2HDM+S, which typically has tighter constraints on the masses and mixing angles. Finally, we examined the complementarity between the electroweak precision analyses and the Higgs coupling precision measurements.

Cheng Li

Juxiang Li

Shufang Su

Wei Su

Electroweak precision constraints of the 2HDM+S * Cheng Li, Juxiang Li, and Wei Su are supported by the Natural Science Foundation of China (NSFC) (12305115), Shenzhen Science and Technology Program (202206193000001, 20220816094256002), Guangdong Provincial Key Laboratory of Gamma-Gamma Collider and Its Comprehensive Applications (2024KSYS001), and Guangdong Provincial Key Laboratory of Advanced Particle Detection Technology (2024B1212010005). Juxiang Li is also supported by the Fundamental Research Funds for the Central Universities, and the Sun Yat-sen University Science Foundation. Shufang Su is supported by the Department of Energy (DEFG02-13ER41976/DE-SC0009913)

In the Kerr–Sen black hole, this study investigates the changes in hotspot images before and after the occurrence of magnetic reconnection. After reviewing the Comisso–Asenjo magnetic reconnection process and introducing the hotspot imaging method, we examine the temporal evolution of hotspot intensity, including when energy extraction occurs, when it does not occur, and when the observer’s azimuthal angle is altered. We also discuss the influence of the black hole’s expansion parameter and spin on hotspot imaging. The results indicate that the first flare may serve as a potential signature of ongoing energy extraction; changing the observer’s azimuthal angle may alter the time interval between the first and second flares; a larger expansion parameter makes it more difficult to identify the energy extraction signal, and a higher spin also makes it more challenging to detect the energy extraction signal.

Ke Wang

Xiao-Xiong Zeng

Hotspot images driven by magnetic reconnection in Kerr–Sen black hole

It has been known for about thirty years that a scattering amplitude involving D0-branes and closed strings suffers from infrared divergences beyond tree level. These divergences arise because the conventional world-sheet approach cannot account for the difference between the D0-brane’s momentum before and after scattering. We show that, by using string field theory, the divergence can be removed and the amplitude rendered finite and unambiguous. We illustrate this using the simplest possible example in bosonic string theory: a three-point function with one incoming and one outgoing D0-brane and an incoming or outgoing closed string tachyon.

Ashoke Sen

United Kingdom

Bogdan Stefański

Scattering of D0-branes and Strings

We analyze quasi-periodic oscillation data from selected X-ray binary systems hosting black holes. To model the spacetime geometry, we resort to the static Sen solution—originally derived in the framework of heterotic string theory—which reduces to the Schwarzschild spacetime for vanishing electric charge. By fitting the observed frequencies within the relativistic precession model, we constrain the mass and charge parameters of the Sen black hole and discuss their astrophysical implications, particularly in distinguishing classical black holes from their string-inspired counterparts.

Kazakhstan

Kuantay Boshkayev

Italy

Marco Muccino

Constraints on the Sen black hole mass and charge from quasi-periodic oscillations

$\textit{N}$ = 2, 4 and 8 supersymmetric string theories in four dimensional flat space-time have moduli space of vacua. We argue that starting from a theory where the moduli approach a particular moduli space point A at infinity, we can construct a classical solution that contains an arbitrarily large space-time region where the moduli take values corresponding to any other moduli space point B of our choice to any desired accuracy. Therefore the observables of a theory with a given set of asymptotic values of the moduli will have complete information on the observables for any other asymptotic values of the moduli. Also it is physically impossible for any experiment, performed over a finite time, to determine the asymptotic values of the moduli. We point out the difference between asymptotically flat space-time and asymptotically AdS space-time in this regard and discuss the possible implication of these results for holographic duals of string theories in flat space-time. For N=2 supersymmetric theories, A and B could correspond to compactifications on topologically distinct Calabi-Yau manifolds related by flop or conifold transitions.

Decorating asymptotically flat space-time with the moduli space of string theory

If a set of charged objects collide in space and the fragments disperse, then this process will emit electromagnetic waves. Classical soft photon theorem determines the constant term and the leading power law fall-off of the wave-form at late and early times in terms of only the momenta and charges of the incoming and outgoing objects. In this paper we determine an infinite set of subleading terms in the late and early time expansion of the wave-form, which also depend only on the momenta and charges of the incoming and outgoing particles. For two-particle scattering, we derive a resummed low-frequency electromagnetic wave-form, as well as the resummed wave-form at early and late times. In this analysis we ignore the effect of long range gravitational interaction, but our result is unaffected by any other short range interactions among the objects.

Debanjan Karan

Babli Khatun

Biswajit Sahoo

All order classical electromagnetic soft theorems