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Johann Rafelski

Publications and source records attributed to Johann Rafelski.

At least 19 recordsLinked to original sources
arXiv2026

Isospin-symmetry violation - kaons and beyond (ISO-BREAK 25: summary and outlook)

This report summarizes the presentations and discussions during the ISO-BREAK 25 Workshop ``Isospin symmetry violation: kaons and beyond'', which was held at Jan Kochanowski University in Kielce on October 23--25, 2025. We address the current status of the isospin-symmetry breaking discovered by NA61/SHINE in nucleus--nucleus collisions at the CERN SPS, its confirmation by other experiments and studies in \ee and deep inelastic scattering. In addition, we discuss the theoretical status as well as we outline experimental and theoretical priorities towards understanding this currently unexplained phenomenon.

nucl-ex↗
arXiv2026

Science Of Nuclear Fusion: Insights and Ideas

Advances in several physics domains open up novel paths to smaller scale, higher energy density opportunities to advance small systems for nuclear fusion. Here we survey both legacy and several novel ``table-top'' approaches which attract current interest. We furthermore address a few related practical and challenging nuclear science topics arising in the context of magnetic confinement and inertial confinement fusion. The contents emphasis includes: By example of solar fusion cycles we draw attention to aneutronic fusion reaction chains. Considering the natural isotopic abundances we assess more carefully the meaning of the term ``limitless energy'' in the context of actual fusion power realizations. We describe achievements in laser-driven proton-boron fusion, and extensions to a self-sustaining and nearly fully aneutronic proton-boron-nitride reaction cycle. We propose another aneutronic option, where the target is a mix of beryllium and light helium isotope; this 3-helium is arguably the most mentioned fusion component in this article. We look in depth at the plasmonic opto-electric field-enhancement for fusion, and at the particle (muon) catalyzed fusion option. We describe problems in harnessing the dt fusion for civilian use. We introduce space travel as forthcoming application of aneutronic fusion.

nucl-th↗
arXiv2026

Technical Proposal for the Atom Interferometer CERN Experiment (AICE) Facility

We present the technical proposal for the Atom Interferometer CERN Experiment (AICE), a $\mathcal{O}(100)$ m vertical atom interferometer to be installed against the wall of the PX46 access shaft to the LHC. AICE is conceived as a versatile and flexible long-baseline atom-interferometry facility whose primary scientific goal is probing for bosonic ultralight dark matter (ULDM) in a mass range inaccessible to other experiments, with a secondary goal of pioneering the exploration of gravitational waves (GWs) with frequencies in the range ${\sim}$0.03-3 Hz as a pathfinder for future longer-baseline detectors. The initial configuration employs ultracold $^{87}$Sr atoms in a single-photon 698-nm interferometer with three shaft-based atom sources in a multi-source gradiometer geometry, supported by one surface reference source for laser stabilisation and diagnostics, to target scalar ULDM. Operation with $^{88}$Sr will give sensitivity to axion-like particles (ALPs), vector ULDM with $B-L$ couplings and violation of the principle of equivalence, while a $^{171}$Yb upgrade will improve the sensitivity to $B-L$ couplings and equivalence violations. Probing the Einstein equivalence principle (EP) and measuring $α$ will proceed in parallel with the ULDM searches. A conceptual feasibility study and a detailed technical implementation study have established that PX46 is a uniquely mature and implementation-ready site, with no technical showstoppers. Completing site preparation works during LS3 would enable the subsequent installation and operation of AICE without impacting HL-LHC operations. The detector design builds on the VLBAI and MAGIS experiments and the AION-10 Technical Design Report, scaling the strontium gradiometer architecture to the $\sim$100 m baseline. AICE is endorsed by the TVLBAI Proto-Collaboration, comprising 57 institutions in 22 countries.

hep-ex↗
arXiv2026

Weinberg Angle, Neutron Abundance in BBN, and Lifetime

We present state of the art kinetic theory determination of the neutron abundance available for the Big-Bang nucleosynthesis (BBN). Our work is motivated by the study of the neutron lifespan measured in the laboratory and the unknown strength of weak interactions coupling constant $G_\mathrm{F}$ at finite temperature in the primordial Universe. We draw attention to the relevant dependence of $G_\mathrm{F}$ on the symmetry breaking Weinberg angle $s^2_\mathrm{W}$, a free parameter in the standard model of particle physics. We establish how the value of $s^2_\mathrm{W}$ by way of $G_\mathrm{F}$ modification influences neutron abundance available for BBN and neutron lifetime.

hep-ph↗
arXiv2026

Covariant Cherenkov Radiation and its Friction Force

We derive the covariant generalization of the Frank-Tamm formula describing the Cherenkov radiation by a charged particle moving uniformly with a speed faster than the local speed of light within a homogeneous dielectric medium. We use our result to derive the covariant Cherenkov radiation reaction force and obtain a four-force explicitly orthogonal to particle four-velocity consistent with a relativistic friction force. We present the photon emission spectrum that is dependent primarily on the dielectric properties of the medium. We hint at a possible use of this work to interpret an excess of soft photons seen in relativistic hadron collisions.

hep-ph↗
arXiv2025

Higgs Thermal Nonequilibrium in Primordial QGP

In this work we investigate the chemical and kinetic nonequilibrium dynamics of the Higgs boson during the primordial Universe QGP (quark-gluon plasma) epoch $130\mathrm{\,GeV}>T>10\mathrm{\,GeV}$. We show that the Higgs bosons is always out of chemical abundance equilibrium with a fugacity $Υ_h = 0.69$ due to virtual decay channels. Additionally, Higgs momentum distribution is found to be ``cold'' for $T<25$\,GeV, since the scattering rate drops below the production rate.

hep-ph↗
arXiv2025

Molecular 9Be+p Fusion Reaction

We study (nuclear) fusion reactions in Beryllium. We argue that some are nuclear long-distance molecular processes of interest for low energy nuclear reactions. For these we develop a novel reaction model. We note a chain of reactions that can naturally arise in Beryllium target created by nonequilibrium proton reactions.

physics.app-ph↗
arXiv2025

Long-Baseline Atom Interferometry

Long-baseline atom interferometry is a promising technique for probing various aspects of fundamental physics, astrophysics and cosmology, including searches for ultralight dark matter (ULDM) and for gravitational waves (GWs) in the frequency range around 1~Hz that is not covered by present and planned detectors using laser interferometry. The MAGIS detector is under construction at Fermilab, as is the MIGA detector in France. The PX46 access shaft to the LHC has been identified as a very suitable site for an atom interferometer of height $\sim 100$m, sites at the Boulby mine in the UK and the Canfranc Laboratory are also under investigation, and possible sites for km-class detectors have been suggested. The Terrestrial Very-Long-Baseline Atom Interferometry (TVLBAI) Proto-Collaboration proposes a coordinated programme of interferometers of increasing baselines.

hep-ex↗
arXiv2025

Short Note on Spin Magnetization in QGP

We outline the theory of spin magnetization applicable to the QGP (quark-gluon plasma) epoch of the Universe. We show that a fully spin-polarized single flavor up-quark gas could generate a cosmic magnetic fields in excess of $10^{15}$ Tesla, far in excess of a possible upper limit to the primordial field. The complete multi component ferro-magnetized primordial fermion gas we consider consists of (five) nearly free electrically charged quarks, and leptons (electrons, muons, tau). We present details of how the magnetization is obtained using a grand partition function approach and point to the role of the nonrelativistic particle component. In the range of temperature 150 MeV to 500 MeV our results are also of interest to laboratory QGP experiments. We show that the required polarization capable to explain large scale structure magnetic fields observed has $1/T$ scaling in the limit of high $T$, and could be very small, at pico-scale. In the other limit, as temperature decreases in the expanding Universe, we show that any magnetic fields present before hadronization can be carried forward to below quark confinement condition temperature by polarization of electrons and muons.

hep-ph↗
arXiv2025

Higgs in The Cosmos

We explore the Higgs particle in the cosmic quark-gluon plasma (QGP) below the electroweak phase transition temperature $T_\mathrm{EW}\simeq 125\mathrm{\,GeV}$. We show that Higgs is neither in abundance (chemical) nor in momentum distribution equilibrium in certain stages of the Universe evolution. Nonequilibrium originates in: For chemical nonequilibrium in the always present irreversible decays into virtual heavy gauge bosons, and; For $T<25$\,GeV in relatively rapid $2\leftrightarrow 1$ formation and decay processes yielding momentum distribution as created in these reactions. As heavy particles disappear, the minimal Higgs coupling to abundant low mass particles fails in $2\to2$ (two-particle) scattering processes to assure a kinetic distribution equilibrium. The expansion of the Universe is by more than 10 orders of magnitude slower compared to microscopic processes. All other particles in the Universe are in full thermal equilibrium, with exception of the late in QGP evolution of the bottom flavor near to hadronization condition.

hep-ph↗
arXiv2025

Nuclear Fusion Enhancement by Heavy Nuclear Catalysts

We seek to understand the effect of high electron density in the proximity of a heavy nucleus on the fusion reaction rates in a hot plasma phase. We investigate quantitatively the catalytic effect of gold ($Z=79$) ions embedded in an electron plasma created due to plasmonic focusing of high-intensity short laser pulses. Using self-consistent strong plasma screening, we find highly significant changes in the internuclear potential of light elements present nearby. For gold, we see a $14\,$keV change in the internuclear potential near the nuclear surface, independent of the long-distance thermal Debye-Hückel screening. The dense polarization cloud of electrons around the gold catalyst leads to a $\sim 1.5$ enhancement of proton-boron ($^{11}$B) fusion above $T=100\,$keV.

physics.plasm-ph↗
arXiv2025

Quarks to Cosmos: Particles and Plasma in Cosmological evolution

We describe in the context of the particle physics (PP) standard model (SM) `PP-SM' the understanding of the primordial properties and composition of the Universe in the temperature range $130\GeV>T>20\keV$. The Universe evolution is described using FLRW cosmology. We present a global view on particle content across time and describe the different evolution eras using deceleration parameter $q$. We follow the arrow of time in the expanding and cooling Universe: After the PP-SM heavies $(t, h, W, Z)$ diminish in abundance below $T\simeq 50\GeV$, the PP-SM plasma in the Universe is governed by the strongly interacting Quark-Gluon content. Once the temperature drops below $T\simeq 150\MeV$, quarks and gluons hadronize into strongly interacting matter particles. Rapid disappearance of baryonic antimatter completes at $T_\mathrm{B}=38.2\MeV$. We study the ensuing disappearance of strangeness and mesons in general. We show that the different eras defined by particle populations are barely separated from each other with abundance of muons fading out just prior to $T=\mathcal{O}(2.5)\MeV$, the era of emergence of the free-streaming neutrinos. We discuss the two relevant fundamental constants controlling the decoupling of neutrinos. We subsequently follow the primordial Universe as it passes through the hot dense electron-positron plasma epoch. The high density of positron antimatter disappears near $T=20.3\keV$: Nuclear reactions occur in the presence of a highly mobile and relatively strongly interacting electron-positron plasma phase. We apply plasma theory methods to describe the strong screening effects between heavy dust particle (nucleons). We analyze the paramagnetic characteristics of the electron-positron plasma when exposed to an external primordial magnetic field.

hep-ph↗
arXiv2024

Self-consistent strong screening applied to thermonuclear reactions

Self-consistent strong plasma screening around light nuclei is implemented in the Big Bang nucleosynthesis (BBN) epoch to determine the short-range screening potential, $eϕ(r)/T \geq 1$, relevant for thermonuclear reactions. We numerically solve the non-linear Poisson-Boltzmann equation incorporating Fermi-Dirac statistics adopting a generalized screening mass to find the electric potential in the cosmic BBN electron-positron plasma for finite-sized $^4$He nuclei as an example. Although the plasma follows Boltzmann statistics at large distances, Fermi-Dirac statistics is necessary when work performed by ions on electrons is comparable to their rest mass energy. While strong screening effects are generally minor due to the high BBN temperatures, they can enhance the fusion rates of high-$Z>2$ elements while leaving fusion rates of lower-$Z\le 2$ elements relatively unaffected. Our results also reveal a pronounced spatial dependence of the strong screening potential near the nuclear surface. These findings about the electron-positron plasma's role refine BBN theory predictions and offer broader applications for studying weakly coupled plasmas in diverse cosmic and laboratory settings.

nucl-th↗
arXiv2024

Fermi-Dirac Integrals in Degenerate Regimes: A Novel Asymptotic Expansion

We characterize in a novel manner the physical properties of the low temperature Fermi gas in the degenerate domain as a function of temperature and chemical potential. For the first time we obtain low temperature $T$ results in the domain where several fermions are found within a de Broglie spatial cell. In this regime, the usual high degeneracy Sommerfeld expansion fails. The other known semi-classical Boltzmann domain applies when fewer than one particle is found in the de Broglie cell. We also improve on the understanding of the Sommerfeld expansion in the regime where the chemical potential is close to the mass and also in the high temperature regime. In these calculcations we use a novel characterization of the Fermi distribution allowing the separation of the finite and zero temperature phenomena. The relative errors of the three approximate methods (Boltzmann limit, Sommerfeld expansion, and the new domain of several particles in the de Broglie cell) are quantified.

cond-mat.quant-gas↗
arXiv2024

Everlasting interaction: polarization summation without a Landau pole

We propose an external field approach to evaluating effective action allowing the interaction to act everywhere at all times (everlasting). Requiring that the asymptotic gauge fields are always-interacting, we implement displacement fields encoding polarization corrections into the derivation of effective action. The result is a novel polarization summation for one-cut reducible loop diagrams, which can be applied to two cases: transient quasi-constant electromagnetic fields, and everlasting interactions. In the first case, a perturbative expansion of our result recovers the Schwinger-Dyson reducible diagram series with a Landau pole. The everlasting summation evaluated in nonperturbative fashion removes the Landau pole, providing a new avenue for modeling strongly interacting theories.

hep-ph↗
arXiv2023

Dynamic fermion flavor mixing through transition dipole moments

We show that Majorana neutrino flavor mixing can be driven by transition dipole moments in the presence of external electromagnetic fields. We demonstrate the sensitivity of the rotation mixing matrix to strong fields obtaining dynamical mass eigenstates in the two-flavor model. The three-flavor case and extensions to the quark sector are introduced.

hep-ph↗
arXiv2023

Superheavy Elements and Ultradense Matter

In order to characterize the mass density of superheavy elements, we solve numerically the relativistic Thomas-Fermi model of an atom. To obtain a range of mass densities for superheavy matter, this model is supplemented with an estimation of the number of electrons shared between individual atoms. Based on our computation, we expect that elements in the island of nuclear stability around $Z = 164$ will populate a mass density range of $36.0 - 68.4$ g/cm$^3$. We then extend our method to the study of macroscopic alpha particle nuclear matter condensate drops.

nucl-th↗