Papers

We present a theoretical framework for jet fragmentation in heavy-ion collisions based on the resummation of large energy logarithms. Exploiting the hierarchy of scales characteristic of jet quenching, we show that the jet function obeys the Banfi-Marchesini-Smye evolution equation, with medium-induced energy loss and color decoherence encoded in the initial condition. This structure reveals a close correspondence with saturation physics. In particular, the coherence angle emerges as the analog of the saturation scale and exhibits the same asymptotic scaling behavior under nonlinear evolution. As a proof of principle, we compute the jet nuclear modification factor to quantify the interplay between vacuum radiation and medium-induced color decoherence. Our framework provides a unified perturbative description of vacuum-like parton showers, medium-induced radiation, and color-coherence effects, paving the way for precision studies of jet quenching at RHIC and the LHC.

The predicted extent of inhomogeneous chiral phases in effective models of quantum chromodynamics is notoriously sensitive to ultraviolet regularization. We show that this sensitivity is largely artificial. In the two-flavor Nambu–Jona-Lasinio model, conventional implementations of three-dimensional cutoff, Pauli–Villars, and proper-time regularization produce strongly different finite-momentum instability regions. Once ultraviolet regulators are restricted to genuinely divergent vacuum contributions, however, all three prescriptions yield nearly identical stability diagrams. Both the onset of the moat regime and the subsequent finite-momentum instability become quantitatively robust. The apparent scheme dependence originates from regulating ultraviolet-finite medium contributions associated with the Fermi-surface response. Our results identify spatially modulated chiral correlations as a genuine property of the dense medium rather than an artifact of the ultraviolet prescription.

Starting from the identity $e^{2\pi i J_z}=(-1)^{F}=e^{i\pi Q}$ on the color-singlet physical state space, we derive a density-operator identity that ties imaginary rotation to an imaginary quark chemical potential, $\rho(\Omega_I+2\pi,\theta_q)=\rho(\Omega_I,\theta_q+\pi)$. Hence imaginarily rotating $SU(3)$ QCD at $(\Omega_I,\theta_q)=(2\pi,0)$ is mapped exactly onto the Roberge-Weiss (RW) point $(0,\pi)$, where charge conjugation $C$ is spontaneously broken above the RW endpoint—a conclusion independent of any model or approximation. Minimizing the one-loop effective potential on the rotation axis, we obtain analytically, for three massless flavors, the second-order transition at $\Omega_{I,C}/\pi=(22-2\sqrt{22})/9$, and a subsequent first-order transition at $\Omega_{I,{\rm lock}}/\pi=2/3+2\sqrt{111}/27$. At smaller $\Omega_I$, a continuous degeneracy of the massless one-loop approximation leaves the realization of $C$ undecided; a finite strange-quark mass lifts it. We also state how the exact relations and the on-axis predictions can be tested in lattice QCD.

We calculate the radiative decay widths of $D_{s1}(2460)\to D_s\gamma$, $D_{s1}(2536)\to D_s\gamma$, $B_{s1}(5750)\to B_s\gamma$, and $B_{s1}(5830)\to B_s\gamma$ within light-cone QCD sum rules, taking into account the mixing between the $^{1}P_{1}$ and $^{3}P_{1}$ configurations. In the bottom-strange sector, we consider the experimentally established $B_{s1}(5830)$ together with the theoretically expected lower $1^+$ state, denoted $B_{s1}(5750)$. We obtain $\Gamma[D_{s1}(2460)\to D_s\gamma]=45.9^{+10.1}_{-8.5}$ keV, $\Gamma[D_{s1}(2536)\to D_s\gamma]=0.55^{+1.73}_{-0.48}$ keV, $\Gamma[B_{s1}(5750)\to B_s\gamma]=12.0^{+2.9}_{-2.3}$ keV, and $\Gamma[B_{s1}(5830)\to B_s\gamma]=8.9^{+2.4}_{-2.0}$ keV. The $D_{s1}(2460)\to D_s\gamma$ decay width is substantially larger than that of $D_{s1}(2536)\to D_s\gamma$. This difference originates from $^{1}P_{1}$-$^{3}P_{1}$ mixing: the two basis-current contributions interfere constructively for the lower state and destructively for the higher state. In the bottom-strange sector, the two widths are comparable within their uncertainties, although the higher state still exhibits destructive interference. These results show that the radiative decay pattern of strange heavy axial-vector mesons is sensitive to the mixing of the two spin configurations.

Imposing elastic unitarity on resonant amplitudes yields a geometric rule connecting the reaction threshold, S-matrix pole, and Breit-Wigner peak. Validated across six orders of magnitude in energy, from $^5\text{He}$ to the Higgs boson, this rule predicts currently unknown residue phases: $-44(12)^\circ$ for $^5\mathrm{He}$, $-24(7)^\circ$ for $\Sigma(1385)^+$, and $-7(13)^\circ$ for $\Xi(1530)^0$. By inverting this formalism, we determine the $\Upsilon(4S)$ pole from its empirical peak to be $10575(1)-i\,8.3(13)$ MeV, with a $-52(6)^\circ$ phase.

Due to its conceptual simplicity, Deeply Inelastic Scattering (DIS) often serves as a textbook example for Quantum Chromo Dynamics (QCD) and partonic structure of nucleons. However, it is this supposed simplicity, which makes DIS an ideal case for discussing many additional effects and corrections. In these lectures we discuss DIS within the domain of perturbative QCD covering a range of topics ranging from mathematical problems to kinematical corrections, and to practical challenges when attempting to interpret experimental measurements. Although here we focus on the exemplary case of DIS, the discussed topcis are relevant to a larger class of processes. We also give an overview of existing and future DIS measurements, and discuss their implementation into modern extractions of parton distribution functions (PDFs) which quantify the partonic structure of nucleons. The discussed features are all implemented in the open source code Yadism, which has been used for PDF extractions from a wide range of the available world data on fully inclusive DIS.

Based on the combined Deep-Inelastic Scattering (DIS) data from HERA and the exclusive $J/\psi$ and $\Upsilon$ cross sections measured at the LHC, we investigate the role of absorptive corrections on the low-$x$ behaviour of parton distribution functions (PDFs) at low and moderate scales. Using $\texttt{xFitter}$, we study the impact of these data and of non-linear evolution on PDFs at next-to-leading order (NLO) and through the NNLO$^*$ method introduced in a previous work. Finally, we determine the effective size of proton hot spots within this framework and discuss the implications of our results for future global PDF determinations.

We examine possible $C$-odd effects in elastic proton-proton and proton-antiproton scattering in the diffractive dip region. Collider data with $\sqrt{s}>500$ GeV are fitted for $0.2<|t|<1~\GeV^2$, using a simple Regge-inspired parametrization of effective $C$-even and $C$-odd amplitudes. The relative phases are not left free, but are fixed by the signature factors of the corresponding even and odd contributions. In this way, the real and imaginary parts of each term are linked by crossing. The $C$-even amplitude is first described by three effective Pomeron-like terms. The $C$-odd sector is then tested with several one-term Odderon-like forms. We find that the fits do not require a stable nonzero $C$-odd term: the odd contribution is either compatible with zero or becomes weakly constrained when we allow extra freedom. We then test whether the conclusion is changed by adding either a fourth Pomeron-like term or a second Odderon-like term. The improvement obtained with the fourth Pomeron-like term is mainly $C$-even, while the second Odderon-like term is not resolved as an independent contribution. These results provide a complementary test of recent determinations of the Odderon amplitude based on scaling and analyticity.

We point out the relevance of a new class of model-independent higher-order contributions to the trilinear and quartic self-couplings of the detected Higgs boson giving rise to potentially large effects of physics beyond the Standard Model (SM). It consists of SM-like diagrams with insertions of loop-corrected values for the trilinear and quartic Higgs self-couplings. While up to now predictions in specific models of physics beyond the SM were only evaluated up to the one-loop or, in some cases, up to the two-loop level, we demonstrate how potentially large higher-order contributions can consistently be incorporated into existing one-loop or two-loop predictions. These model-independent higher-order contributions therefore improve the existing predictions that were obtained in specific models. Confronting our predictions with the relevant experimental results and theoretical constraints, we perform a simultaneous determination of the trilinear and quartic Higgs-boson self-couplings. We show that the new set of model-independent higher-order contributions can induce sizeable shifts in the inferred bounds on the trilinear and quartic Higgs self-couplings. For example, including the new higher-order corrections can shift the upper bound on the trilinear self-coupling modifier entering the theoretical predictions to $\sim4.9$ from the experimental limit of $ 6.1$. Our results demonstrate that incorporating these higher-order contributions is essential for a reliable interpretation of present and future measurements. We further provide a public tool that implements these effects and enables direct comparison with experimental limits.

Extended Higgs sectors beyond the Standard Model (BSM) allow to dynamically generate the observed baryon asymmetry of the Universe through electroweak baryogenesis and thereby solve one of the most prominent open problems of the SM. The strong first-order phase transitions (PTs), required to preserve the generated asymmetry in the electroweak vacuum, source gravitational waves (GW) that can be tested at future experiments like LISA. Gravitational waves hence provide the exciting possibility to probe BSM physics through cosmological processes. In order to be able to eventually pin down the specific underlying physics, a good understanding of the evolution of the vacuum of the model under investigation is indispensable as well as of the uncertainties that are involved in the derivation of the GW spectrum. We use our code BSMPTv3 that allows to reliably derive the finite temperature vacuum structure of extended Higgs sectors with multiple vacuum directions and calculates the GW spectrum of the found (multiple) strong first-order PTs, and we apply it to the real, i.e. CP-conserving, 2-Higgs-Doublet Model. Taking into account all relevant theoretical and experimental constraints, we perform a thorough analysis of its vacuum evolution, the related collider and GW phenomenology and complement it by an uncertainty discussion.

We investigate the connection between resonant leptogenesis and a primordial stochastic gravitational-wave background in a minimal two-right-handed-neutrino type-I seesaw with a real singlet scalar. The scalar sector admits a $\mathbb Z_2$-symmetric tree-level potential, while the tiny right-handed-neutrino coupling to the $\mathbb Z_2$-odd scalar generates a radiative vacuum-energy bias that causes the domain-wall network to annihilate. For quasi-degenerate heavy neutrinos, we describe the heavy-neutrino system with a density-matrix kinetic framework and use the ratio $r_q=\Delta M/\Gamma_{N_1}$ as an organizing variable for the separated, resonant and coherent regimes. The heavy-neutrino parameters that control the physical mass splitting also enter the radiatively generated domain-wall bias, providing a model-dependent link between the quantum-kinetic baryon asymmetry and the gravitational-wave peak frequency and amplitude. We emphasize that the gravitational- wave signal is not a direct measurement of an individual low-energy neutrino parameter; rather, it provides a model-dependent consistency relation among neutrino data, resonant leptogenesis, domain-wall annihilation and the stochastic gravitational-wave background.

We present a leading-order study of the rare exclusive decays $t \to bM$, where $M$ denotes a pseudoscalar or vector meson. Starting from the tree-level transition $t \to bW^* \to b(q\bar q')$ and using a factorization approximation, we derive compact expressions for the amplitudes and partial widths in which the long-distance QCD dynamics is encoded in the meson decay constants $f_M$. We provide numerical branching-ratio predictions for representative modes such as $t \to b\pi^+$, $t \to bK^+$, $t \to bD_s^{(*)}$, and $t \to bB_c^{(*)}$, finding $\mathrm{Br} \sim 10^{-8}$–$10^{-7}$. For vector final states, we derive helicity amplitudes and Standard-Model polarization fractions, and we outline the sensitivity of these observables to anomalous chiral $tWb$ couplings in the limit $m_b \to 0$. Our results provide an updated Standard Model (SM) baseline for rare exclusive top-quark decays and a starting point for EFT interpretations of non-standard charged-current interactions.

Higgs pair production provides an important probe of the Higgs self-interaction and the Higgs potential structure. We study the lightest neutral Higgs pair production process $gg \to hh$ via gluon fusion at the 14 TeV LHC, in the $U(1)_X$ supersymmetric standard model. As a $U(1)$ extension of the minimal supersymmetric standard model (MSSM), this model introduces new superfields that bring additional one-loop contributions to the production amplitude. We analyze the parameter dependence of the cross section numerically and present contour distributions in two-dimensional parameter planes. The results indicate that the gauge couplings $g_X$ and $g_{YX}$ are the most sensitive parameters, and the model yields sizable new physics corrections under current experimental constraints. This work helps to understand Higgs physics in the $U(1)_X$SSM and guides new physics searches at the high-luminosity LHC.

We study deep-inelastic scattering (DIS) in the threshold region $x\to 1$ beyond leading power in $1-x$ at leading twist. In the framework of position-space soft-collinear effective theory, we derive a factorization theorem for the off-diagonal parton-scattering channel, which starts at next-to-leading power (NLP). The hadronic tensor separates into an anti-hardcollinear contribution from power-suppressed currents and a soft-collinear contribution from subleading Lagrangian interactions, whose convolution integrals exhibit endpoint divergences. We show that these divergences are resolved by endpoint factorization relations, implying that the parton distribution function (PDF) near threshold becomes a two-scale object at NLP. We derive the factorization of the NLP gluon distribution at large $x$ in terms of hardcollinear matching coefficients and a subtracted soft-collinear function. We resum the leading logarithms of $1-x$ both from $d$-dimensional factorization in the $\overline{\rm MS}$ scheme and in an endpoint scheme based on refactorization, and establish the all-order relation between the two definitions of the PDF.

We compare our previous predictions for charged-hadron production in p-O collisions at an energy of sqrt(s_NN)=9.618 TeV as published in 2025 with preliminary Run 3 data from ALICE and adapt the model parameters to the data. Our three-source model comprises a gluon-gluon central source and two valence-quark soft-gluon fragmentation sources. We describe the initial conditions using color-glass-condensate states and calculate the time-dependent partial thermalization with a relativistic diffusion model. An inversion of the maximum production amplitude at larger pseudorapidities from backward to forward towards peripheral collisions is predicted.

In this work, we revamp the democratic mixing matrix (DM) by adding a perturbation term such that the mixing angles derived from it are compatible with the NuFIT 6.1 and recent findings from the Jiangmen Underground Neutrino Observatory (JUNO). To do this, we have incorporated perturbation term in the elements of the mixing matrix such that it does not lose its unitarity. Thus, the democratic mixing matrix, once ruled out by the experimental evidences from T2K, Double Chooz, and Daya Bay, can be modified with rotational perturbation in the (1,2), (1,3), and (2,3) sectors and additional real parameters added in each element of DM. Finally, we analyze the allowed and disallowed textures in light of the JUNO findings.

We explore the multimessenger signatures from ultracompact minihalos (UCMHs) seeded by stellar-mass primordial black holes (PBHs) and composed of QCD-axion dark matter. Using the secondary-infall framework, with relic-abundance and isocurvature conditions from a pre-inflationary Peccei-Quinn scenario, we numerically recover the characteristic halo profile and adopt a conservative constant-density core for the innermost region. We study the gravitational wave and electromagnetic signatures from neutron-star-PBH inspirals inside these dense structures. Dynamical friction produces a gravitational-wave dephasing relative to the vacuum binary, observable with LISA for primordial black holes with masses $\lesssim\! 10M_\odot$. Simultaneously, gravitationally focused axions can resonantly convert into photons in the neutron-star magnetosphere, producing a narrow-band radio signature. For nearby galactic neutron stars, the projected sensitivity of the Green Bank radio telescope GBT captures the QCD-axion band in the $\mu{\rm eV}$ mass range. Gravitational waves therefore probe the presence and structure of the UCMH, while the radio signal probes the particle nature of its dark matter, making their joint observation a distinctive test of a mixed dark sector.

Recently, some research has emerged that used the Tsallis statistics in Quantum Chromodynamics (QCD). In Tsallis statistics, the Tsallis parameter $\mathfrak{q}$ reflects long-range interactions, non-Markovian memory, and multifractal boundary effects, linking directly to temperature variance in fluctuating systems, which vanish in the Boltzmann-Gibbs limit. This is our motivation to investigate the thermodynamical variables of a hot and dense system. Within a non-extensive color QCD MIT-Bag Model and using the Tsallis distributions to describe the thermal response functions related to the equation of state. The study focuses on the deconfinement phase transition from a hadronic gas to a quark-gluon plasma in order to analyze the behavior of thermodynamical quantities of the system, such as the energy density, the pressure and the interaction measure at finite volume under Tsallis statistics. Furthermore, the effect of the $\mathfrak{q}$-parameter on the phase transition point is investigated. We find that the transition point is significantly affected by the $\mathfrak{q}$-parameter in the framework of non-extensive statistics.

Femtoscopic correlation functions (CFs) have been increasingly used to extract strong interactions between pairs of unstable particles, but their physical soundness has recently been questioned. To answer this, we formulate CFs at the operator level, with the observed subsystem described by a reduced density operator and subsequent dynamics absorbed into an effective measurement operator. The Koonin-Pratt form is recovered under four well-motivated reductions. The formulation makes explicit that the source-side and interaction-side representations must be consistently matched, and motivates an operational convention in which a measured reference correlation establishes a compatible source–interaction pairing that can be extended to other pairs for CF-to-CF predictions.

A $\gamma\gamma$-collider capable of reaching the 10 TeV parton-center-of-momentum (pCM) frontier of particle physics may enable the study of phenomena beyond the Standard Model. Based on compact linear wakefield accelerator technology, such a collider could be realized by Compton scattering multi-TeV lepton beams off moderate-intensity laser pulses close to the collider interaction point, producing the required $\gamma$-photons. It is shown that, for a wide range of scattering-laser wavelengths, $\gamma\gamma$-collisions at the interaction point can meet the luminosity requirements for novel particle physics studies, even in the presence of the prolific electron-positron pair production that accompanies the interaction of the scattering laser with the multi-TeV lepton beam. Notably, this pair production imposes a natural limit on the maximum achievable photon luminosity. Accounting for this limit and for the angular divergence of the Compton photons yields an enhanced $\gamma\gamma$-collider luminosity for 250 nm and 1.25 nm scattering lasers. Moreover, the secondary pairs can themselves be exploited in physics studies, since their luminosity is high enough to produce heavy particles at rates needed for discoveries well beyond the reach of existing colliders.

We extend the small-$x$ analysis of the quark and gluon orbital angular momentum (OAM) distributions in the proton from the large-$N_c$ limit considered in our earlier works to the large-$N_c\&N_f$ limit, in which the numbers of quark colors $N_c$ and flavors $N_f$ are large with their ratio held fixed. Working in the double-logarithmic approximation (DLA), summing powers of $\alpha_s \ln^2(1/x)$ with $\alpha_s$ the strong coupling and $x$ the proton's momentum fraction carried by a parton, we correct the small-$x$ operator expression for the quark OAM distribution suggested earlier in \cite{Kovchegov:2024wjs} and relate both the quark and gluon OAM distributions to the impact-parameter moments of the polarized dipole amplitudes. We derive the large-$N_c\&N_f$ evolution equations for these moment amplitudes in the DLA; these include a new equation for the moment amplitude governing the quark OAM. We then solve these evolution equations numerically together with the helicity evolution for $N_f = 2,3,4,5,6$ and $N_c =3$. We find that, similar to the large-$N_c$ case, the OAM distributions share a common small-$x$ intercept with the helicity distributions, $L_{q+\bar{q}}(x,Q^2) \sim L_G(x,Q^2) \sim \Delta \Sigma (x,Q^2) \sim \Delta G(x,Q^2) \sim \left(\frac{1}{x} \right)^{\alpha_h}$ with the intercept $\alpha_h \approx {3.48 \sqrt{\alpha_s N_c/2\pi}}$ for $N_f = N_c = 3$ (cf.~\cite{Borden:2025ehe}): this result, along with $\alpha_h$ for other values of $N_f \neq 0$ that we studied, is smaller than the intercept of $3.66\sqrt{\alpha_s N_c/2\pi}$ found in the large-$N_c$ limit. We also compute the ratios of the OAM distributions to the helicity parton distribution functions as $x\to 0$, obtaining $L_{q+\bar{q}}(x,Q^2)/\Delta\Sigma(x,Q^2) \approx -1.01$ and $L_G(x,Q^2)/\Delta G(x,Q^2) \approx -1.94$ at $Q^2=10\, \mathrm{GeV}^2$, with both ratios being nearly independent of $N_f$.

Neutrino interaction generators are central to precision oscillation analyses, but conventional implementations do not directly provide derivatives of their predictions with respect to physics parameters, leaving analyses to obtain this dependence through reweighting, finite differences or external response models. We present ADoNIS, a fully differentiable neutrino interaction event generator that makes event reweighting and its gradients directly available, propagating exact derivatives through the nuclear ground state, hard-scattering amplitudes and stochastic intranuclear cascade. Following the physics choices of ACHILLES, we demonstrate agreement with its predictions across neutrino, electron and hadron probes, showing that differentiability is achieved without loss of physical fidelity. We then show how the resulting Jacobian exposes which measurements and regions of phase space constrain each parameter and how different probes break degeneracies, providing a quantitative tool for fit design, model tuning, measurement design and experiment design. The same differentiable predictions can be used directly in frequentist and Bayesian inference and carried through detector response to reconstructed observables for unfolding, while also yielding computational gains. In sum, ADoNIS provides a practical recipe for constructing differentiable neutrino event generators, applicable beyond the particular physics models implemented here, and this paper demonstrates their use across a wide range of tasks relevant to both theory and experiment.

We present a global two-channel Flatté amplitude analysis of the hidden-charm pentaquark candidates observed by the LHCb collaboration in the J/{\psi}p invariant-mass spectrum using the Run 1+2 dataset. We simultaneously fit the three pentaquark amplitudes to the full spectrum, including a polynomial background and complex coupling phases. The scattering length and effective range are extracted from the fitted amplitudes using the effective range expansion, with uncertainties determined through non-parametric bootstrap resampling. While real couplings yield scattering parameters compatible with a molecular interpretation, this conclusion becomes less robust when coupling phases are included. We further find that interference effects are important for the closely spaced Pc(4440)+ and Pc(4457)+ states, demonstrating the limitations of the incoherent-sum approximation.

Fragmentation functions extracted from electron-proton and electron-positron collisions have shown not to be able to explain prompt charm hadron ratios in proton-proton collisions at the LHC energies. New models and event generator tunes have been developed to correctly describe the data from the ALICE experiment in proton-proton collisions at different center of mass energies. In this work Pythia 8.312 is used to implement two of those models: the SC-CR and BLC-CR + Ropes. Both show a good performance to reproduce the data at \sqrt{s}} = 13 TeV in different event conditions for the $\Lambda_{c}^{+}/\rm{D}^0$, $\Sigma_{c}^{0,+,++}/\rm{D}^0$, $\rm{D}^{+}/\rm{D}^0$ and $\rm{D}^{*+}/\rm{D}^0$ ratios. For the particular case when the prompt charm hadrons are within jets, all the ratios show modifications relative to the case where the presence of jets is not required. A study in two different ranges of the relative transverse activity is also conducted. In this case only the baryon to meson ratios show a dependence on the underlying event activity. Results indicate that baryon and meson hadronisation are not affected in the same way by local effects or global event conditions

We study neutrino oscillations in an ultralight axion-like particle (ALP) dark-matter background using a bottom-up derivative interaction for active neutrinos. For couplings diagonal in the neutrino mass basis, the leading relative phase is fixed by the difference of the ALP field between production and detection. More generally, an unresolved background multiplies each interference term by the characteristic function of this endpoint field difference. For a single fixed-amplitude coherent mode with uniformly sampled phase, the factor is $J_0(A_{ij})$. In the slow-flight and small-dephasing regimes, this result and a Gaussian virialized-halo treatment agree at quadratic order and produce a leading $L^2E^0$ suppression. We identify the finite-exposure and coherence conditions under which the two statistical descriptions apply. As an application, we analytically map the energy-independent damping constraint derived from the first JUNO data onto the flavor benchmark $g_2=g_3$. For a local ALP density of $0.4\mathrm{GeV}/\mathrm{cm}^3$, the low-mass plateau gives $|\Delta g_{21}|=|\Delta g_{31}|\lesssim0.90\mathrm{GeV}^{-1}$. This number is a baseline-matched EFT recast of the reference damping analysis. No specific ultraviolet completion is assumed.

Neutrino oscillation phenomenology is usually communicated through two-dimensional projections (probability curves, oscillograms, and bi-probability plots), each of which flattens a function of many parameters (baseline, energy, matter density, mass ordering, and the CP-violating phase) onto a single static figure. We present NuGlass, an open-source, web-based application that renders six complementary, fully interactive 3D views of the same underlying three-flavor evolution: an oscillogram surface, a bi-probability trajectory extruded along energy, a Bloch-sphere projection of the quantum flavor state, a matter-eigenstate phasor decomposition of the oscillation amplitude, a flavor-composition tube along the propagation baseline, and a worldline view that plots the probabilities against L/E and makes the matter-induced breaking of the vacuum degeneracy visible. An oscillation channel switcher, experiment presets, and customizable animation controls are provided. NuGlass can be used both as a research exploration tool and as a public-engagement exhibit. The application runs entirely client-side and is deployed at https://czczc.github.io/nuglass/ .

Recent advances in cosmological measurements such as DESI and ACT may indicate an increase in the preferred value of the spectral tilt $n_s$ such that it disfavors rather popular models such as the Higgs or Starobinski inflation models. We argue that it actually means that the data is now sensitive enough to quantum corrections beyond simple tree-level models. Resurrecting the old theme of Coleman-Weinberg effective potential, we analyze the predictions of such models, as well as likelihood analysis, leading to a more established and interesting predictive framework.

We propose a novel approach to detecting low-energy electron antineutrinos based on the induced capture of orbital electrons by nuclei. This process is resonant, requiring the antineutrino energy to precisely match the energy difference between the final and initial atomic systems. For continuous-spectrum sources, the resonance conditions can be satisfied without fine-tuning, and the effective cross sections depend on the spectral intensity of the $\bar{\nu}_e$ flux at the resonance rather than on the neutrino energy itself. This opens the possibility of detecting neutrinos of never previously probed low energies. We identify a number of candidate nuclides that allow transitions to excited states of the daughter nuclei corresponding to resonant $\bar{\nu}_e$ energies below the inverse $\beta$ decay threshold of 1.8 MeV, and we consider a distinctive atomic-nuclear coincidence signature for background rejection. We discuss implications of the proposed method for detecting low-energy reactor neutrinos, geoneutrinos, and keV-scale thermal solar neutrinos. Applications to neutrino oscillation experiments and to reactor monitoring are also briefly discussed.

Gravitational radiation from the early Universe offers a powerful window into physics beyond the Standard Model (SM). In this paper, we investigate the low-frequency tail of gravitational radiation produced by the decay of massive particles. The energy spectrum in Minkowski space-time, $dE/d\omega$, exhibits two distinct regimes: a flat bremsstrahlung/memory spectrum above a characteristic cutoff frequency and a suppressed quadratic frequency scaling below it. The typical rate of momentum change of the decay products determines the cutoff frequency. We calculate $dE/d\omega$ in two independent but equivalent ways: using Weinberg's soft graviton theorem and by solving the equations of motion. This further establishes the connection between Weinberg's soft graviton theorem and the gravitational memory formula, which we generalize to incorporate the effects of final-state scattering. We then compute the cosmological stochastic gravitational energy spectrum $h^2\Omega_{\rm h}$ generated by many particle decays in the early Universe. We demonstrate that $h^2\Omega_{\rm h}$ exhibits linear scaling with frequency above the cutoff frequency, transitioning to cubic scaling below it. Our findings reveal a suppression of the low-frequency signal compared to a naive linear extrapolation, with implications for detection prospects. Our results also reveal the connection between bremsstrahlung and memory in the context of cosmological stochastic gravitational energy spectra from the early Universe.

Warm dark matter (WDM) has served as a valuable benchmark for constraining small-scale structure in the past decades. In this note, I examine what it would take for dark matter to be warm in the literal sense assumed by that benchmark, i.e., a thermal relic that decoupled while relativistic. Satisfying current constraints on the WDM mass, which approach the $\sim$10 keV scale, requires one of three possibilities. One possibility is that there were $\sim 10^4$ relativistic degrees of freedom in the thermal bath at the time of decoupling, which is far beyond what is available in the Standard Model or plausible extensions of it. An alternative is that there was a period of early matter domination whose entropy injection diluted the relic density. However, in this scenario, the perturbations would have evolved through an expansion history that was different from the radiation-dominated one assumed in deriving WDM transfer functions. The third possibility is a dark sector that was never in thermal contact with the Standard Model and was simply born colder via asymmetric reheating. All of these possibilities rely on strong coincidences, where physics that has nothing to do with WDM happens to provide the exact initial conditions assumed in a WDM cosmology. Meanwhile, WDM is often used as a proxy for models with self-consistent thermal histories that generically predict the suppression of structure formation on small scales in a way that is both quantitatively and qualitatively different from WDM. I therefore advocate for a transition to more expressive parameterizations and simulation-based methods in order to extract more useful information from the wealth of upcoming data.