Particle Physics Research Articles

A Note on Gravitational Dark Matter Production

Dark matter, one of the fundamental components of the universe, has remained mysterious in modern cosmology and particle physics, and hence, this field is of utmost importance at the present moment. One of the foundational questions in this direction is the origin of dark matter, which directly links to its creation. In the present article, we study the gravitational production of dark matter in two distinct contexts: firstly, when reheating occurs through gravitational particle production, and secondly, when it is driven by decay of the inflaton field. We establish a connection between the reheating temperature and the mass of dark matter, and from the reheating bounds, we determine the range of viable dark matter mass values.

Deep(er) reconstruction of imaging Cherenkov detectors with swin transformers and normalizing flow models

Abstract Imaging Cherenkov detectors are crucial for particle identification (PID) in nuclear and particle physics experiments. Fast reconstruction algorithms are essential for near real-time alignment, calibration, data quality control, and efficient analysis. At the future electron–ion collider (EIC), the ePIC detector will feature a dual Ring Imaging Cherenkov (RICH) detector in the hadron direction, a Detector of Internally Reflected Cherenkov (DIRC) in the barrel, and a proximity focus RICH in the electron direction. This paper focuses on the DIRC detector, which presents complex hit patterns and is also used for PID of pions and kaons in the experiment at JLab. We present Deep(er)RICH, an extension of the seminal DeepRICH work, offering improved and faster PID compared to traditional methods and, for the first time, fast and accurate simulation. This advancement addresses a major bottleneck in Cherenkov detector simulations involving photon tracking through complex optical elements. Our results leverage advancements in Vision Transformers, specifically hierarchical Swin Transformer and normalizing flows. These methods enable direct learning from real data and the reconstruction of complex topologies. We conclude by discussing the implications and future extensions of this work, which can offer capabilities for PID for multiple cutting-edge experiments like the future EIC.

A unified machine learning approach for reconstructing hadronically decaying tau leptons

Tau leptons serve as an important tool for studying the production of Higgs and electroweak bosons, both within and beyond the Standard Model of particle physics. Accurate reconstruction and identification of hadronically decaying tau leptons is a crucial task for current and future high energy physics experiments. Given the advances in jet tagging, we demonstrate how tau lepton reconstruction can be decomposed into tau identification, kinematic reconstruction, and decay mode classification in a multi-task machine learning setup. Based on an electron-positron collision dataset with full detector simulation and reconstruction, we show that common jet tagging architectures can be effectively used for these sub-tasks. We achieve comparable momentum resolutions of 2–3% with all the tested models, while the precision of reconstructing individual decay modes is between 80–95%. We find ParticleTransformer to be the best-performing approach, significantly outperforming the heuristic baseline. This paper also serves as an introduction to a new publicly available Fuτure dataset for the development of tau reconstruction algorithms. This allows to further study the resilience of ML models to domain shifts and the efficient use of foundation models for such tasks.

Towards harmonized ecotoxicological effect assessment of micro- and nanoplastics in aquatic systems.

Micro- and nanoplastics are globally important environmental pollutants. Although research in this field is continuously improving, there are a number of uncertainties, inconsistencies and methodological challenges in the effect assessment of micro- and nanoparticles in freshwater systems. The current understanding of adverse effects is partly biased by the use of non-relevant particle types, unsuitable test setups and environmentally unrealistic dose metrics, which does not take into account realistic processes in particle uptake and consequent effects. Here we summarize the current state of the art by compiling the most recent research with the aim to highlight research gaps and further necessary steps towards more harmonized testing systems. In particular, ecotoxicological scenarios need to mirror environmentally realistic particle diversity and bioavailability. Harmonized test setups should include different uptake pathways, exposures and comparisons with natural reference particles. Effect assessments need to differentiate direct physical particle effects, such as lesions and toxicity caused by the polymer, from indirect effects, such as alterations of ambient environmental conditions by leaching, change of turbidity, food dilution and organisms' behavior. Implementation of these suggestions can contribute to harmonization and more effective, evidence-based assessments of the ecotoxicological effects of micro- and nanoplastics.

INTREPID

INTREPID The discovery of the Higgs boson at the LHC closes a central chapter of the standard model of particle physics but raises questions about dark matter, neutrino masses and baryon asymmetry. Answers may involve long-lived particles (LLPs) with non-standard signatures, requiring advanced identification algorithms. Enhancing trigger capabilities to discover LLPs and evidence of beyond the standard model (BSM) physics is, therefore, a crucial task. INTREPID uses advanced machine learning and ultra-fast processing to improve future trigger systems, potentially revolutionising high-energy physics and benefiting industries needing real-time data processing.

Trans-Dimensional Unified Field Theory (TDUFT)

Trans-Dimensional Unified Field Theory (TDUFT) proposes a revolutionary approach to understanding the universe's intricate mechanics. By integrating the core concepts of velocity ((\phi)), time (( \hat{\phi})), mass, energy, wave-particle duality, and insights gleaned from advanced particle physics experiments, particularly those conducted at CERN, TDUFT aims to forge a cohesive bond between classical mechanics and modern quantum theories. This framework not only clarifies profound relationships among these elements but also presents opportunities for new interpretations of fundamental physical laws.

A three-parameter model for dark matter halos based on general relativity and quantum field theory

In this paper, we present a three-parameter model for the distributions of “dark matter” around local spherically symmetric and static distributions of normal matter, usually referred to as “dark matter halos”. The model is based on the assumption that the spontaneous symmetry breaking mechanism involving the Higgs field in the standard model of elementary particle physics leads to the existence of a constant distribution of vacuum energy throughout space–time. This is to be interpreted as a constant distribution of proper energy, as measured by local observers in their proper reference frames. Due to the presence of this universal distribution of vacuum energy, the model requires the introduction of the cosmological term in the Einstein field equations, in order to regulate the behavior of the resulting geometry at cosmologically large distances. By implementing the model on galactic scales, we are able to establish the gravitational consequences of such a homogeneous distribution of proper energy density at these scales. This results in equivalent halo masses and orbital velocity curves that, at least qualitatively, match the observations for galactic “dark matter” halos. Although the detailed realization of the model presented and calculated here cannot be construed as a precise representation of galactic structure, given that most of the actual structure of the galaxy, such as the galactic disk itself, is ignored, and replaced by a single spherically symmetric bulge, in this paper we do introduce the conceptual framework that may be used to construct a more complete galactic model in the future.

Stability of the standard model vacuum with vectorlike leptons: A critical examination

The stability of the standard model (SM) Higgs vacuum is a long-standing issue in particle physics. The SM Higgs quartic coupling parameter is expected to become negative at high scales, potentially generating an unstable vacuum well before reaching the Planck scale. We investigate whether the introduction of vectorlike leptons (VLLs) in six distinct gauge anomaly-independent representations can stabilize the SM vacuum without introducing additional scalar fields. By analyzing the mass spectrum and mixing angles of these VLLs with the SM leptons, we identify conditions under which the Higgs potential remains stable. We demonstrate that there exists a set of allowed but narrowed VLL spectra that can indeed stabilize the SM vacuum. We also study the effect of these VLLs on electroweak precision observables, particularly the oblique parameters S and T, to ensure the fit within global experimental constraints. Finally, we perform a comprehensive analysis of the parameter space allowed by electroweak precision data and the parameter space required for stability, highlighting cases that accommodate both. This study opens up new avenues for understanding the role of vectorlike leptons in extending the validity of the standard model up to the Planck scale. Published by the American Physical Society 2025

Nanophotonic electron accelerator: A review of particle accelerator technology

Particle accelerators are indispensable tools in various industries, spanning a wide range of research fields such as nuclear and particle physics. They are particularly valuable in the medical sector for applications like medical imaging, radiotherapy and tumor treatment. Currently, the largest and most powerful particle accelerator is the Large Hadron Collider (LHC) at CERN, a 27-kilometer-long ring-shaped tunnel that accelerates particles, such as protons, to near-light speeds and collides them. While the LHC represents the pinnacle of accelerator technology, there is significant interest in developing compact particle accelerators that can fit within buildings, laboratories, or even on tabletops. However, even smaller accelerators often occupy several square meters of valuable space and may suffer from performance limitations. Not all applications require massive machines like the LHC, and more compact solutions could fulfill many needs efficiently. Furthermore, a breakthrough in this field has been achieved by a team of laser physicists from Friedrich-Alexander University Erlangen-Nürnberg (FAU), who successfully demonstrated the first nanophotonic electron accelerator. This nanoscale device has been used to accelerate electrons, achieving a remarkable energy gain. What makes this development truly exciting is the unprecedented compactness of the nanophotonic accelerator - it is so small that it fits on a one-cent coin, making it the smallest particle accelerator currently available. Often referred to as a "particle accelerator on a chip," this technology holds immense potential, including applications in advanced cancer radiation therapies.

The Flipped SU(5)×U(1) Model from Four-Dimensional Strings

We review the construction of a flipped SU(5)×U(1) model in the context of the Free-Fermionic Formulation of four-dimensional strings and present its main phenomenological consequences in particle physics and cosmology.

Exploring New Physics with PandaX-4T Low Energy Electronic Recoil Data

New particles beyond the standard model of particle physics, such as axions, can be effectively searched through their interactions with electrons. We use the large liquid xenon detector PandaX-4T to search for novel electronic recoil signals induced by solar axions, neutrinos with anomalous magnetic moment, axionlike particles, dark photons, and light fermionic dark matter. A detailed background model is established using the latest datasets with 1.54 ton yr exposure. No significant excess above the background has been observed, and we have obtained competitive constraints for axion couplings, neutrino magnetic moment, and fermionic dark matter interactions. Published by the American Physical Society 2025

Emergence of opposing arrows of time in open quantum systems

Deriving an arrow of time from time-reversal symmetric microscopic dynamics is a fundamental open problem in many areas of physics, ranging from cosmology, to particle physics, to thermodynamics and statistical mechanics. Here we focus on the derivation of the arrow of time in open quantum systems and study precisely how time-reversal symmetry is broken. This derivation involves the Markov approximation applied to a system interacting with an infinite heat bath. We find that the Markov approximation does not imply a violation of time-reversal symmetry. Our results show instead that the time-reversal symmetry is maintained in the derived equations of motion. This imposes a time-symmetric formulation of quantum Brownian motion, Lindblad and Pauli master equations, which hence describe thermalisation that may occur into two opposing time directions. As a consequence, we argue that these dynamics are better described by a time-symmetric definition of Markovianity. Our results may reflect on the formulations of the arrow of time in thermodynamics, cosmology, and quantum mechanics.

Learning PDFs through interpretable latent representations in Mellin space

Representing the parton distribution functions (PDFs) of the proton and other hadrons through flexible, high-fidelity parametrizations has been a long-standing goal of particle physics phenomenology. This is particularly true since the chosen parametrization methodology can play an influential role in the ultimate PDF uncertainties as extracted in QCD global analyses; these, in turn, are often determinative of the reach of experiments at the LHC and other facilities to nonstandard physics, including at large x, where parametrization effects can be significant. In this study, we explore a series of encoder-decoder machine-learning (ML) models with various neural-network topologies as efficient means of reconstructing PDFs from meaningful information stored in an interpretable latent space. Given recent effort to pioneer synergies between QCD analyses and lattice-gauge calculations, we formulate a latent representation based on the behavior of PDFs in Mellin space, i.e., their integrated moments, and test the ability of various models to decode PDFs from this information faithfully. We introduce a numerical package, , which implements several encoder-decoder models to reconstruct PDFs with high fidelity and use this end-to-end tool to explore how such neural-network-based models might connect PDF parametrizations to underlying properties like their Mellin moments. We additionally dissect patterns of learned correlations between encoded Mellin moments and reconstructed PDFs that suggest opportunities for further improvements to ML-based approaches to PDF parametrizations and uncertainty quantification. Published by the American Physical Society 2025

Numerical tools in particle physics

In this paper, I stress the role of the numerical tools for any theoretical predictions in the field of particle physics due to the difficult and complex computation of the different observable related to the different processes. Being one of the contributors to the program Phantom, I chose it as a prototype to shed light on the main features of the Monte Carlo event generators and how they work. I tried to keep the presentation as simple as possible, avoiding as many technical difficulties as possible, to make this short review accessible to a large number of undergraduate students. It can serve as a good starting point with plenty of references for those who want to deepen their knowledge in the subject.

Bounds on Lorentz and CPT violation from the 1S−2P transition in antihydrogen

A model for the Lorentz- and CPT-violating frequency shift for the antihydrogen 1S−2P transition in the presence of an external magnetic field is derived. Using the recent measurement of the 1S−2P transition frequency in antihydrogen by the ALPHA collaboration, which they demonstrated agrees with predictions from the Standard Model of particle physics, we establish the first constraints on 26 effective coefficients for Lorentz and CPT violation. Also, this work uses these results to underscore the value of measuring multiple transition frequencies to test CPT symmetry through antihydrogen spectroscopy, emphasizing the advantages of transitions involving states with higher angular momentum. Published by the American Physical Society 2025

Dynamical analysis of multi-soliton and interaction of solitons solutions of nonlinear model arise in energy particles of physics

Dynamical analysis of multi-soliton and interaction of solitons solutions of nonlinear model arise in energy particles of physics

Precise interpretations of traditional fine-tuning measures

We uncover two precise interpretations of traditional electroweak fine-tuning (FT) measures that were historically missed. : the traditional FT measure shows the change in plausibility of a model in which a parameter was exchanged for the Z boson mass relative to an untuned model in light of the Z boson mass measurement. the traditional FT measure shows the exponential of the extra information, measured in nats, relative to an untuned model that you must supply about a parameter in order to fit the Z mass. We derive the mathematical results underlying these interpretations, and explain them using examples from weak scale supersymmetry. These new interpretations allow us to rigorously define FT in particle physics and beyond, shed fresh light on the status of extensions to the Standard Model and, lastly, allow us to precisely reinterpret historical and recent studies using traditional FT measures. Published by the American Physical Society 2025

New models of quintessential inflation featuring plateau and hilltop potentials

We introduce a new class of hilltop and plateau potentials which can successfully unify inflation and dark energy resulting in quintessential inflation (QI). Interestingly these new potentials are related through an inverse transformation. Namely, if V(ϕ)=V0v(ϕ) is a plateau potential then the inverse potential V(ϕ)=V0v(ϕ)-1 describes hilltop QI. A simple example is provided by the KKLT-inspired potential v(ϕ)=M2n+ϕ2nN2n+ϕ2n. When M/N≪1 this potential describes plateau QI, while its inverse, v(ϕ)-1 describes hilltop QI. Other simple models of QI arise for the class of potentials V(ϕ)∼exp∓f(ϕ), where the − (+) sign is associated with a plateau (hilltop). A key feature of this new class of QI models is the near absence of small dimensionless parameters, or small mass parameters (relative to the energy scale of the Standard Model of particle physics) – which are usually associated with the presence of dark energy. A forecast for the gravitational wave background generated in these models is provided.

Recent advancements in atomic many-body methods for high-precision studies of isotope shifts

Abstract The development of atomic many-body methods, capable of incorporating electron correlation effects accurately, is required for isotope shift (IS) studies. In combination with precise measurements, such calculations help to extract nuclear charge radii differences, and to probe for signatures of physics beyond the Standard Model of particle physics. We review here a few recently-developed methods in the relativistic many-body perturbation theory (RMBPT) and relativistic coupled-cluster (RCC) theory frameworks for calculations of IS factors in the highly charged ions (HCIs), and neutral or singly-charged ions, respectively. The results are presented for a wide range of atomic systems in order to demonstrate the interplay between quantum electrodynamics (QED) and electron correlation effects. In view of this, we start our discussions with the RMBPT calculations for a few HCIs by rigorously treating QED effects; then we outline methods to calculate IS factors in the one-valence atomic systems using two formulations of the RCC approach. Then we present calculations for two valence atomic systems, by employing the Fock-space RCC methods. For completeness, we briefly discuss theoretical input required for the upcoming experiments, their possibilities to probe nuclear properties and implications to fundamental physics studies.

A Unified Model of Natural Evolution and the Crises in Particle Physics and Cosmology

A unified model of the evolution of the universe is presented. The model consists of four stages: Planckian, Einsteinian, Darwinian, and Intellectual. The evolution of the universe is described as a single flow of information processing that begins at the Planckian stage and continues into the emergence of the most complex information processor: the human brain and the technologically developed human civilization. Each stage has its own structural and functional unit, carriers of evolutionary information, and driving evolving objects. The Planckian stage is described as a system of quantum-mechanically entangled PlanckITs: an entity that represents existence in a randomized space and randomized time. The space-time continuum is presented as a collection of addressable PlanckYTEs. APlanckYTE contains a fixed number of PlanckITs. In the Einsteinianstage, the leptons and quarks of the latest appeared generation carry the information that define the conditions for the transition to the Darwinian stage. Leptons and quarks code a set of parameters that define the conditions for the origin of life and its subsequent evolution. The following expression: ME = (9ℏc3)/(2αGkTE) is one of the results that supports this fact. The Darwinian stage describes biological evolution. The intellectual stage uses the concepts of life symmetry and intellectual fields to describes the intellectual or cultural evolution of social systems. This paper is the first of three papers: ”A Unified Model of Natural Evolution and the Crises in Particle Physics and Cosmology”; ”Space and Time at Planck’s Scale, Carriers of the Evolutionary Information, and the Evolution of the Universe”; ”Evolutionary Anthropodynamics: The Evolution of Intellectual Systems”. Some calculations are done to support the unified model of natural evolution.