arXiv subjects

A. Pukhov

Publications and source records attributed to A. Pukhov.

At least 19 recordsLinked to original sources

arXiv2026

Report on the Advanced Linear Collider Study Group (ALEGRO) Workshop 2026

The 7th ALEGRO workshop, hosted by INFN Frascati National Laboratories from 3rd to 5th March 2026, brought together the international Advanced Novel Accelerators (ANA) community to discuss the role of advanced wakefield accelerators (AWA) in particle and high-energy physics. Organized under the ICFA-ANA panel, the workshop highlighted recent progress in plasma- and structure-based wakefield acceleration and strengthened international collaboration toward future energy-frontier colliders. A major focus was the ongoing 10 TeV linear collider design study, launched in 2025 following the US P5 recommendations. A dedicated session covered accelerator concepts, enabling technologies, and the associated physics case, while recognizing that future priorities will depend on the outcome of the European Strategy for Particle Physics Update. The workshop also reviewed nearer-term applications of advanced accelerators, including fixed-target experiments, injectors for future colliders and light sources, plasma-based Higgs factory concepts, and proton-driven plasma wakefield acceleration. Beyond high-energy physics, sessions covered free-electron lasers, synchrotron light sources, and strong-field QED. Recent demonstrations of FEL lasing with plasma-accelerated electron beams highlighted significant progress in beam quality and accelerator performance. Operational challenges for reliable user facilities, including high-availability laser and electron-beam systems, were discussed alongside the growing role of artificial intelligence and machine learning for accelerator optimization and control. This report summarizes the workshop discussions and conclusions from the chairs, together with short contributions from the presenters, providing an overview of the current status and future prospects of advanced wakefield accelerators.

physics.acc-ph↗

arXiv2026

micrOMEGAs 7: Beyond standard cosmology

We present micrOMEGAs7, a major upgrade of the micrOMEGAs package for the computation of dark matter observables in generic models. This release introduces a generalized treatment of the Boltzmann equations, allowing for user-defined modifications of the Hubble expansion rate, entropy evolution, and non-thermal dark matter production from late-decaying cosmological components, thereby extending the framework beyond the standard radiation-dominated cosmology. The relic density can now be computed in scenarios such as low-temperature reheating, early matter domination, and kination. The new version also improves the treatment of sub-GeV dark matter, in particular annihilation into light mesons through scalar mediators, and provides updated spectra for indirect detection. Several experimental and observational constraints have been implemented or revised, including CMB bounds from Planck on energy injection during recombination and Fermi-LAT limits from dwarf spheroidal galaxies. For direct detection, a recast of recent LZ results has been included, and the code now takes into account effective electromagnetic couplings of spin-$1/2$ and spin-1 dark matter. Collider observables have also been extended through the implementation of CMS dilepton resonance constraints on $Z'$ mediators. Additional improvements include a more flexible treatment of effective relativistic degrees of freedom and an updated LHAPDF interface.

hep-ph↗

arXiv2026

An electron injector for the Electron-Ion Collider based on proton-driven plasma wakefield acceleration

We describe an electron bunch injector scheme based on proton-driven plasma wakefield acceleration for the Electron-Ion Collider. The proton bunches needed to drive the plasma wake are delivered by the existing Blue-Ring of RHIC. The polarized electron source is that in the current EIC design. We describe the different elements making up the injection scheme and give an estimate for the performance. Our initial study indicates that the design parameters of the EIC are within reach when accelerating the electron bunches in the proton-driven plasma wake, with average polarization of ~70% and a luminosity of 1e34 cm$^{-2}$s$^{-1}$.

physics.acc-ph↗

arXiv2026

Tolerances to driver-witness misalignment in a quasilinear plasma wakefield accelerator

Plasma-based accelerators offer high accelerating gradients and scalability through staging or long plasma sources, which makes them good candidates for future accelerator and collider concepts. Proton-driven accelerators in particular have the potential to bring particles to high energy in a single stage. In the quasilinear regime - where the plasma wake is only partially evacuated - a witness bunch of electrons drives a cavitated wake, which acts to preserve the emittance of the portion of the witness inside this self-blowout. In the case of a misalignment between the driver and witness, this behaviour can persist, but its effectiveness is reduced. In this paper, we study transverse witness dynamics in this regime, and develop analytical models to describe the witness motion, and develop a metric to estimate emittance preservation based on a single parameter which estimates the density of the witness after phase mixing. Particle in cell simulations using the AWAKE Run 2c baseline parameters show excellent agreement with the predictive models developed. This work allows alignment constraints to be set both for the AWAKE experiment and other wakefield acceleration schemes operating in the quasilinear regime.

physics.plasm-ph↗

arXiv2025

Self-Adaptive Stabilization and Quality Boost for Electron Beams from All-Optical Plasma Wakefield Accelerators

Shot-to-shot fluctuations in electron beams from laser wakefield accelerators present a significant challenge for applications. Here, we show that instead of using such fluctuating beams directly, employing them to drive a plasma photocathode-based wakefield refinement stage can produce secondary electron beams with greater stability, higher quality, and improved reliability. Our simulation-based analysis reveals that drive beam jitters are compensated by both the insensitivity of beam-driven plasma wakefield acceleration, and the decoupled physics of plasma photocathode injection. While beam-driven, dephasing-free plasma wakefield acceleration mitigates energy and energy spread fluctuations, intrinsically synchronized plasma photocathode injection compensates charge and current jitters of incoming electron beams, and provides a simultaneous quality boost. Our findings suggest plasma photocathodes are ideal injectors for hybrid laser-plasma wakefield accelerators, and nurture prospects for demanding applications such as free-electron lasers.

physics.acc-ph↗

arXiv2024

Measurement of the emittance of accelerated electron bunches at the AWAKE experiment

The vertical plane transverse emittance of accelerated electron bunches at the AWAKE experiment at CERN has been determined, using three different methods of data analysis. This is a proof-of-principle measurement using the existing AWAKE electron spectrometer to validate the measurement technique. Large values of the geometric emittance, compared to that of the injection beam, are observed ($\sim \SI{0.5}{\milli\metre\milli\radian}$ compared with $\sim \SI{0.08}{\milli\metre\milli\radian}$), which is in line with expectations of emittance growth arising from plasma density ramps and large injection beam bunch size. Future iterations of AWAKE are anticipated to operate in conditions where emittance growth is better controlled, and the effects of the imaging systems of the existing and future spectrometer designs on the ability to measure the emittance are discussed. Good performance of the instrument down to geometric emittances of approximately $\SI{1e-4}{\milli\metre\milli\radian}$ is required, which may be possible with improved electron optics and imaging.

physics.acc-ph↗

arXiv2024

micrOMEGAs 6.0: N-component dark matter

micrOMEGAs is a numerical code to compute dark matter (DM) observables in generic extensions of the Standard Model of particle physics. We present a new version of micrOMEGAs that includes a generalization of the Boltzmann equations governing the DM cosmic abundance evolution which can be solved to compute the relic density of N-component DM. The direct and indirect detection rates in such scenarios take into account the relative contribution of each component such that constraints on the combined signal of all DM components can be imposed. The co-scattering mechanism for DM production is also included, whereas the routines used to compute the relic density of feebly interacting particles have been improved in order to take into account the effect of thermal masses of t-channel particles. Finally, the tables for the DM self-annihilation - induced photon spectra have been extended down to DM masses of 110 MeV, and they now include annihilation channels into light mesons.

hep-ph↗

arXiv2023

Feebly-interacting dark matter

We briefly review scenarios with feebly interacting particles (FIMPs) as dark matter candidates. The discussion covers issues with dark matter production in the early universe as well as signatures of FIMPs at the high energy and high intensity frontier as well as in astroparticle and cosmology.

hep-ph↗

arXiv2022

Electron and ion acceleration from femtosecond laser-plasma peeler scheme

Using three-dimensional particle-in-cell simulations, we further investigate the electron and ion acceleration from femtosecond laser-plasma peeler scheme which was proposed in our recent paper (Shen et al 2021 Phys. Rev. X 11 041002). In addition to the standard setup where a laser pulse impinges on an edge of a single tape target, two new variants of the target, i.e., a parallel tape and a cross tape target, were proposed, where strong surface plasma waves can also be efficiently excited at the front edges of the target. By using a tabletop 200 TW-class laser pulse, we observe generation of high-flux, well-collimated, superponderomotive electrons. More importantly, quasimonoenergetic proton beams can always be obtained in all the three setups, while with the single tape case, the obtained proton beam has the highest peak energy and narrowest spectrum.

physics.plasm-ph↗

arXiv2022

Cross-Filament Stochastic Acceleration of Electrons in Kilojoule Picosecond Laser Interactions with Near Critical Density Plasmas

Understanding the interaction of kilojoule, picosecond laser pulse with long-scale length preplasma or homogeneous near critical density (NCD) plasma is crucial for guiding experiments at national short-pulse laser facilities. Using full three-dimensional particle-in-cell simulations, we demonstrate that in this regime, cross-filament stochastic acceleration is an important mechanism that contributes to the production of superponderomotive, high-flux electron beams. Since the laser power significantly exceeds the threshold of the relativistic self-focusing, multiple filaments are generated and can propagate independently over a long distance. Electrons jump across the filaments during the acceleration, and their motion becomes stochastic. We find that the effective temperature of electrons increases with the total interaction time following a scaling like $T_{\rm eff}\proptoτ_{i}^{0.65}$. By irradiating a submillimeter thick NCD target, the space charge of electrons with energy above 2.5 MeV reaches tens of $μ$C. Such high-flux electrons with superponderomotive energies significantly facilitate applications in high-energy-density science, nuclear science, secondary sources and diagnostic techniques.

physics.plasm-ph↗

arXiv2022

Branched flow of intense laser light in plasma with uneven density distribution

Branched flow is an interesting phenomenon that can occur in diverse systems. It is usually linear in the sense that the flow does not alter the medium properties. Branched flow of light on thin films was recently discovered. A question of interest is thus if nonlinear branched flow of light can also occur. Here we found using particle-in-cell simulations that with intense laser propagating in plasma with randomly uneven density distribution, photoionization by the laser can locally enhance the density variations along the laser paths and thus the branching of the laser. However, too-intense lasers can smooth the uneven electron density and suppress branching. The observed branching properties agree well with an analysis based on a Helmholtz equation for the laser electric field. Branched flow of intense laser in uneven plasma potentially opens up a new realm of intense laser-matter interaction.

physics.plasm-ph↗

arXiv2022

WIMP and FIMP dark matter in the inert doublet plus singlet model

We consider multi-component dark matter in a model where one dark matter component is feebly interacting (FIMP) while the second is weakly interacting (WIMP). The model contains an inert scalar doublet and a complex scalar singlet and features a discrete $Z_4$ symmetry. We determine the parameter space that satisfies theoretical constraints, collider constraints, relic density as well as direct and indirect detection limits. We discuss the possibility to probe the model through collider and astrophysical searches. We find that it is possible that the FIMP forms the dominant DM component, in this case the astrophysical signatures of the WIMP are much suppressed. We also explore the case where the doublet can decay into pairs of singlets leaving only one DM component, the FIMP. These scenarios are constrained by BBN and are best explored at colliders since astrophysical signatures are suppressed.

hep-ph↗

arXiv2022

New insights in laser-generated ultra-intense gamma-ray and neutron sources for nuclear applications and science

Ultra-intense MeV photon and neutron beams are indispensable tools in many research fields such as nuclear, atomic and material science as well as in medical and biophysical applications. For astrophysical applications aimed for laboratory investigations, neutron fluxes in excess of 10$^{21}$ n/(cm$^2$ s) are required. Such ultra-high fluxes are unattainable with existing conventional reactor- and accelerator-based facilities. Currently discussed concepts for generating high-flux neutron beams are based on ultra-high-power multi-petawatt lasers operating at >10$^{23}$ W/cm$^2$ intensities. Here, we present a novel efficient concept for generating $γ$ and neutron beams based on enhanced generation of direct laser accelerated electrons in relativistic laser interactions with a long-scale near critical density plasma at 10$^{19}$ W/cm$^{2}$ intensity. New experimental insights in the laser-driven generation of ultra-intense well-directed multi-MeV beams of photons with >10$^{12}$ ph/sr and a ultra-high intense neutron source with >6$\times$10$^{10}$ neutrons per shot are presented. More than 1.4\% laser-to-gamma conversion efficiency above 10 MeV and 0.05\% laser-to-neutron conversion efficiency were recorded, already at moderate relativistic laser intensities and ps pulse duration. This approach promises a strong boost of the diagnostic potential of existing kJ PW laser systems used for ICF research.

physics.plasm-ph↗

arXiv2021

Spatial profile of accelerated electrons from ponderomotive scattering in hydrogen cluster targets

We study the laser-driven acceleration of electrons from overdense hydrogen clusters to energies of up to 13 MeV in laser forward direction and several hundreds of keV in an outer ring-like structure. The use of cryogenic hydrogen allows for high repetition-rate operation and examination of the influence of source parameters like temperature and gas flow. The outer ring-like structure of accelerated electrons, originating from the interaction, that is robust against the change of laser and target parameters can be observed for low electron densities of ca. 3$\times$10$^{16}$ cm$^{-3}$. For higher electron densities, an additional central spot of electrons in the laser forward direction can be observed. Utilizing 3D-PIC simulations, it is revealed that both electron populations mainly stem from ponderomotive scattering.

physics.plasm-ph↗

arXiv2021

Analysis of Proton Bunch Parameters in the AWAKE Experiment

A precise characterization of the incoming proton bunch parameters is required to accurately simulate the self-modulation process in the Advanced Wakefield Experiment (AWAKE). This paper presents an analysis of the parameters of the incoming proton bunches used in the later stages of the AWAKE Run 1 data-taking period. The transverse structure of the bunch is observed at multiple positions along the beamline using scintillating or optical transition radiation screens. The parameters of a model that describes the bunch transverse dimensions and divergence are fitted to represent the observed data using Bayesian inference. The analysis is tested on simulated data and then applied to the experimental data.

physics.acc-ph↗

arXiv2021

Optimized laser-assisted electron injection into a quasi-linear plasma wakefield

We present a novel electron injection scheme for plasma wakefield acceleration. The method is based on recently proposed technique of fast electron generation via laser-solid interaction: a femtosecond laser pulse with the energy of tens of mJ hitting a dense plasma target at $45^o$ angle expels a well collimated bunch of electrons and accelerates these close to the specular direction up to several MeVs. We study trapping of these fast electrons by a quasi-linear wakefield excited by an external beam driver in a surrounding low density plasma. This configuration can be relevant to the AWAKE experiment at CERN. We vary different injection parameters: the phase and angle of injection, the laser pulse energy. An approximate trapping condition is derived for a linear axisymmetric wake. It is used to optimise the trapped charge and is verified by three-dimensional particle-in-cell simulations. It is shown that a quasi-linear plasma wave with the accelerating field $\sim$ 2.5 GV/m can trap electron bunches with $\sim$ 100 pC charge, $\sim$ 60 $μ$m transverse normalized emittance and accelerate them to energies of several GeV with the spread $\lesssim$ 1 % after 10 m.

physics.plasm-ph↗

arXiv2021

Two dark matter candidates: the case of inert doublet and singlet scalars

We consider a multi-component dark matter model where the dark sector contains a scalar doublet and a complex scalar singlet. We impose a discrete $Z_4$ symmetry to ensure such that the lightest component of the doublet, $\tilde{A}$, and the singlet, $\tilde{S}$, are both stable. Interactions between the dark sectors impact significantly dark matter observables, they allow in particular to significantly relax the direct detection constraints on the model. To determine the parameter space that satisfies relic density, theoretical and collider constraints as well as direct and indirect detection limits, we perform two separate scans, the first includes the full parameter space of the model while the second is dedicated to scenarios with a compressed inert doublet spectrum. In the first case we find that the singlet is generally the dominant dark matter component while in the compressed case the doublet is more likely to be the dominant dark matter component. In both cases we find that the two dark matter particles can have masses that ranges from around $m_h/2$ to over the TeV scale. We emphasize the interplay between cosmological astrophysical and collider constraints and show that a large fraction of the parameter space that escapes current constraints is within the sensitivity reach of future detectors such as XENON-nT, Darwin or CTA. Important collider signatures are mostly found in the compressed spectrum case with the possibility of probing the model with searches for heavy stable charged particles and disappearing tracks. We also show that semi-annihilation processes such as $\tilde{S}\tilde{S}\to \tilde{A}Z$ could give the dominant signature in indirect detection searches.

hep-ph↗

arXiv2021

Simulation and Experimental Study of Proton Bunch Self-Modulation in Plasma with Linear Density Gradients

We present numerical simulations and experimental results of the self-modulation of a long proton bunch in a plasma with linear density gradients along the beam path. Simulation results agree with the experimental results reported in arXiv:2007.14894v2: with negative gradients, the charge of the modulated bunch is lower than with positive gradients. In addition, the bunch modulation frequency varies with gradient. Simulation results show that dephasing of the wakefields with respect to the relativistic protons along the plasma is the main cause for the loss of charge. The study of the modulation frequency reveals details about the evolution of the self-modulation process along the plasma. In particular for negative gradients, the modulation frequency across time-resolved images of the bunch indicates the position along the plasma where protons leave the wakefields. Simulations and experimental results are in excellent agreement.

physics.plasm-ph↗