Papers

Light scalar spectators generically acquire large stochastic fluctuations during inflation, which can lead to a catastrophic overproduction of dark matter if the resulting primordial condensate survives until late times. We show that this inflationary memory can be sufficiently suppressed by an extremely feeble Higgs portal interaction with sub-freeze-in couplings ($10^{-28} \lesssim \lambda_{HS} \lesssim 10^{-9}$). The Higgs portal induces both a radiative self-interaction for the spectator as well as a thermal mass, both of which can lead to early onset of oscillations and efficient redshifting of the condensate's energy density without thermalizing the spectator or destroying the condensate. The Higgs portal also alters the stochastic equilibrium distribution of the spectator fluctuations, leading to a suppression of the field variance relative to an isolated spectator. We include a detailed treatment of the possibility that inflation may not have lasted sufficiently long for the spectator to reach its equilibrium distribution of fluctuations, finding the major constraint on such a scenario to come from isocurvature, which requires $N \gtrsim10^{10}$ e-folds. We also consider the addition of a non-minimal gravitational coupling, which extends the parameter space significantly. This model generally favors sub-GeV light dark matter ($0.1 \text{ eV} \lesssim m_S \lesssim 10 \text{ GeV}$) and in the absence of non-minimal gravity it also favors low reheating temperatures. While this mechanism can supply the entire relic abundance with sub-freeze-in portal couplings, it also naturally provides a suppressed initial condition for standard Higgs portal freeze-in.

Axion-like particles (ALPs) appear in many well-motivated extensions of the Standard Model (SM) and can exhibit characteristic interactions with electroweak gauge bosons ($V = W^\pm/ Z$) through higher-dimensional operators. We explore the production of ALPs ($a$) in association with $V$ at the HL-LHC, with $\sqrt{s}=14~{\rm TeV}$ and an integrated luminosity of $\mathcal{L}=3~{\rm ab}^{-1}$. We study the process $pp\to Va$, with $a\to\gamma\gamma$, for ALP masses in the range $20~{\rm GeV}\leq m_a\leq 200~{\rm GeV}$. This analysis extends existing associated-production searches by exploiting characteristic recoil and polarization features induced by the momentum-dependent $\rm {V-V-a}$ interaction. Using both cut-based selections and an XGBoost multivariate analysis, we demonstrate that these observables provide robust discrimination against SM backgrounds beyond the diphoton mass peak, improving the sensitivity to electroweak ALP couplings to $C_{WW} \gtrsim 5.6 \times 10^{-3}~\mathrm{TeV}^{-1}$ and $C_{BB} \gtrsim 2.8\times 10^{-2}~\mathrm{TeV}^{-1}$. We further show that, if a resonance peak is observed in data, the same observables can help distinguish an ALP-like signal from a Higgs-like spin–0 state of the same mass.

We discuss three aspects of the ongoing efforts of the CTEQ–TEA group toward global parton distribution function (PDF) analyses beyond NNLO accuracy in QCD. First, we present a realization of the SACOT-$\chi$ general-mass variable flavor number scheme for deep-inelastic scattering (DIS) at the partial next-to-next-to-next-to-leading order (pN$^3$LO) in QCD. We numerically illustrate how this SACOT-$\chi$ theory prediction captures the dependence of DIS structure functions on masses of heavy quarks with inclusion of the available $O(\alpha_s^3)$ contributions. Second, we discuss a preliminary pN$^3$LO CT25 fit that implements such contributions. Third, we extend the Candia algorithm for solving DGLAP evolution equations for unpolarized parton distribution functions (PDFs) in $x$ space to N$^3$LO in QCD. The algorithm is based on logarithmic expansions of the solution and can be extended to all orders in QCD. An expansion equivalent to the exact DGLAP solution at N$^3$LO is presented in the non-singlet sector. We show results for approximate N$^3$LO PDFs evolved using the most recent approximations to the 4-loop splitting functions in QCD.

In this work we study the unitarity constraints on double Higgs production from Vector Boson Fusion mediated channels, specifically in $f_1 f_2 \to f_3 f_4 H_5 H_6$ scattering, where $f$ refers generically to either fermion or anti-fermion, and both cases with quarks and leptons will be considered. We focus on the beyond Standard Model contributions from anomalous quartic couplings of two electroweak gauge bosons and two Higgs bosons ($VVHH$ with $VV=WW, ZZ$) from effective operators containing four derivatives. These four derivative operators appear in the two most popular effective field theories, SMEFT (at canonical dimension 8) and HEFT (at chiral dimension 4), and their corresponding $VVHH$ effective vertices can be easily related for the considered processes here. The aim of this work is to derive jointly the unitarity constraints on these related effective vertices using the peculiarities of the VBF mediated channels with four particles in the final state while keeping the propagation of the internal $VV$ pairs being off-shell as it must be for these channels. We also discuss the relevance of the obtained constraints for $f_1 f_2 \to f_3 f_4 H_5 H_6$ at high energy colliders.

In view of the recent experimental finding of the heavy quark flavor partner of the $D_{s0}(2317)$ in the bottom sector, the $B_{s0}(5700)$, we perform the $B^{(*)}\bar{K}^{(*)}$ coupled-channel calculation in the hidden-gauge formalism. By fixing the mass of the bound state generated by the $B\bar{K}$ interaction with $J^P=0^+$ to the observed state, we also predict five new states with $J^P=\lbrace 0,1,2\rbrace^+$ in this sector. In particular, three of them have $J^P=1^+$ and masses $5740$, $6005$ and $6065$ MeV, respectively. In addition, we evaluate the decay width of the $B_{s0}$ and $B_{s1}$ states through the isospin breaking decay mode $B_s^0\pi^0$ and $B_s^{*0}\pi^0$, respectively. We find that, because these states have large binding energies with respect to the $B^{(*)}\bar{K}$ threshold, the coupling to the bare component can reduce this decay width by more than half of the decay width, from $50$ keV in the purely molecular model to $10-20$ keV, when the $B_{s0}$ is coupled to the bare component. We also observe that, after considering heavy-quark-spin violating contributions, the decay width for the $B_{s1}$ becomes smaller than for the $B_{s0}$.

Interpreting neutrino oscillation measurements requires computing the probability that a neutrino born with one flavor is detected with another. In vacuum and in matter of constant density, this probability has exact formulas. Where the density varies along the path, as in the Earth, the Sun, or a supernova, it does not. There, the usual approaches either replace the profile by constant-density steps, whose error falls only as the square of their width, or integrate the evolution equation with a general-purpose solver, which must shorten its steps to meet a tighter tolerance. Both become slow at high accuracy, yet an analysis needs the probability at many energies, directions, and parameter values. Each new experiment or model often requires writing and validating a new solver. We present Magnus, an open-source Python code that avoids these limitations. It uses the Magnus expansion, whose error falls as a high power of its step width and whose cost is set by how fast the density varies, not by how many oscillations the path holds. Magnus accepts any density profile, any number of flavors, and any Hermitian Hamiltonian, such as those of non-standard interactions, sterile neutrinos, Lorentz-invariance violation, and pseudo-Dirac neutrinos. Where a cheaper route exists, it takes it automatically. For example, where the density varies slowly, as in the Sun, it follows the instantaneous eigenstates and applies the expansion only at resonances. Besides oscillating probabilities, Magnus returns phase-averaged ones, which describe solar and astrophysical neutrinos. A typical probability takes a few milliseconds, and batched scans are one to two orders of magnitude cheaper per point. Among the public codes we compared, Magnus is the fastest at high accuracy on a varying profile. Magnus shifts the effort of studying a new experiment or model from writing a solver to specifying its physics.

Although the spontaneous decay of axions into two photons is extremely slow on cosmological timescales, it can be strongly enhanced in environments with large bosonic occupation numbers. From a classical field perspective, stimulated axion decay is described by modified Maxwell equations. For a coherent axion background, these equations exhibit a parametric resonance characterized by a photon growth exponent $s\propto g_{a\gamma}$. By contrast, a standard kinetic description, for instance based on Boltzmann equations, involves the squared matrix element of the decay process and therefore would naturally predict a characteristic rate scaling as $s\propto g_{a\gamma}^2$. In this work, we show that these apparently different behaviors originate from the coherence properties of the axion field. Starting from an axion field with a finite momentum dispersion, we show how dephasing among its momentum modes modifies the photon instability and derive an effective evolution equation in which this effect is encoded in a kernel. For a continuous Maxwell-Boltzmann distribution of axion velocities, we obtain an implicit expression for the photon growth exponent that reproduces the two asymptotic regimes and provides an approximate description of the crossover. When amplification develops on scales shorter than the axion coherence length, the parametric resonance scaling $s\propto g_{a\gamma}$ is recovered, whereas in the opposite limit an effectively kinetic behavior with $s\propto g_{a\gamma}^2$ emerges. Although the detailed form of the crossover depends on the axion momentum distribution, we expect the asymptotic scaling with $g_{a\gamma}$ to be largely insensitive to the specific distribution assumed.

We study the generalized symmetries associated with Standard Model flavor and their fate in the presence of magnetic monopoles. This illuminates a striking phenomenological consequence: even when baryon and lepton number are classically conserved, the electroweak anomaly induces $\Delta B = \Delta L \in 3 \mathbb{Z}$ in monopole-fermion scattering for any monopole activating the anomaly. We demonstrate this mechanism in Pati-Salam theory and trinification.

The back-to-back limit of the energy-energy correlator (EEC) exhibits a finite plateau, capturing the evolution from perturbative soft-collinear radiation at weak coupling to string dynamics at strong coupling. At weak coupling, we resum its leading and next-to-leading-power logarithms through N$^3$LL in $\mathcal N=4$ SYM, including non-planar contributions. Combining this weak-coupling endpoint with bootstrap and strong-coupling data, we construct an interpolation for the plateau height from weak to strong coupling. The calculation uses a human-in-the-loop agentic workflow.

We compute Kerr-Newman quasinormal modes using a recently found exact separation of the gravitoelectric perturbation equations. For each spin-label $\varsigma=\pm1$, a matrix angular ordinary differential equation and a scalar second-order radial ordinary differential equation define a joint spectral problem for the complex frequency $\omega$ and separation constant $\lambda$. We solve this problem by imposing regularity at the angular poles, ingoing behavior at the event horizon, and outgoing behavior at infinity. We benchmark the numerical code built to solve the separated equations, and the resulting frequencies, against recently published spectral calculations of the coupled system. Comparisons with those results yield absolute differences of order $10^{-10}$ to $10^{-5}$, depending on the BH parameters and overtone number. We also find numerical hints of spin-label isospectrality in both the electromagnetic-led and gravitational-led sectors of fundamental quasinormal modes, even at near-extremal Kerr-Newman configurations. These results provide numerical evidence that the separated equations reproduce Kerr-Newman quasinormal frequencies and offer a practical route to exploring the ringdown of rotating, charged black holes.

We explore a possible decay of the top quark into a new scalar $\phi_t$ plus a charm quark. The decay is mediated by a dimension-5 operator that may be generated by the exchange of a heavy vectorlike quark, $\chi$, and can have a branching fraction close to a percent. In a minimal model, $\phi_t$ decays due to the same operator that allows the nonstandard top decay, leading to a final state involving a $c$ jet, a $b$ jet and a $W$ boson. Hence, the top quark would undergo a nonstandard cascade decay through $\phi_t$ and then through an off-shell top quark. The main nonstandard collider signal is a $t \bar t \to c \, \bar c \, b \, \bar b \, W^+ W^-$ process. In addition, production of the vectorlike quark at the LHC would lead to a signal of the type $\chi \phi_t \, j \to 3c + b \, \bar b \, W W j$.

Recently, the LHCb Collaboration reported a new narrow bottom-strange meson, $B_{s0}^*(5700)$ with mass $M= (5698.9 \pm 1.5 \pm 0.6)$~MeV, width $\Gamma<9.8$~MeV, and spin-parity $J^P=0^+$ in the $B_s^0\pi^0$ invariant-mass spectrum. Motivated by this observation, we study the low-lying $P$-wave $B_s$ mesons in a two-stage refined constituent quark model. The one-loop radiative corrections to the confinement–one-gluon exchange potential ($\alpha_s^2$) lower the whole multiplet by $25$–$50$~MeV and improve the level ordering; however, the scalar $B_{s0}^*$ mass still exceeds the LHCb data by $\sim120$~MeV in a purely compact picture. The inclusion of the coupled-channel dynamics is decisive: the $BK$ threshold, lying close to the scalar mass, generates a sizeable meson–meson (molecular-like) component that pulls the pole down to $\sim5727$~MeV, within $30$~MeV of the measurement, and simultaneously suppresses the $S$-wave phase space, naturally accounting for the anomalously narrow width. Consistent results are obtained for the $1^+$ $B_{s1}$ partner, for which we predict a mass $\sim5747$–$5755$~MeV, in agreement with the chiral-doubling scenario. The $B_{s1}$ state is expected to be very narrow and decaying mainly through the isospin-violating $B_s^*\pi^0$ and radiative $B_s\gamma$, $B_s^*\gamma$ modes, providing a clear discovery target at LHC Run~3. The $E1$ radiative widths of the $j_\ell=1/2$ states are predicted at the $50\sim 60$~keV, and the strong width of the pure $j_\ell=3/2$ state $B_{s2}^*(5840)$ ($1.5$~MeV) reproduces the measurement. Our results support the interpretation of $B_{s0}^*(5700)$ as a near-threshold scalar with strong molecular dressing and establish the predicted $1^+$ $B_{s1}(5747)$ as the decisive test of the hadronic dynamics in the $B_s$ sector.

We study primordial black holes and scalar-induced gravitational waves in the supersymmetric 331 model based on SU(6). The inflaton continues to be the D-flat radial combination of the 331 symmetry-breaking fields Phi and Phi-bar, fields which are already accountable for the CMB branch. A gauge-invariant contribution that is localised in the Kaehler frame function causes the force in the Einstein frame to decrease over a finite range of the field and results in a temporary nonattractor phase. We calculate the supergravity potential and the radial metric, evolve the background and the Mukhanov-Sasaki modes, and assess the neutral covariant Hessian along the local region. The CMB trajectory is still in agreement with the present observational constraints while the curvature spectrum attains a value of P_zeta ~ 5.38 x 10^-3 when k ~ 1.88 x 10^13 Mpc^-1. The enhanced spectrum leads to a primordial black hole distribution with a mass comparable to that of an asteroid and to a maximum in the scalar-induced gravitational wave signal at a frequency of 3.17 x 10^-2 Hz with Omega_GW,0 h^2 ~ 9.41 x 10^-11. The local geometry also results in a clear hierarchy of sensitivities. The gravitational wave spectrum changes smoothly as one moves along nearby trajectories whereas the Gaussian tail of the primordial black hole distribution changes much more rapidly. The positive eigenvalues of the neutral transverse Hessian remain throughout the reference trajectory. A Gaussian critical collapse calculation yields a reference integrated primordial black hole fraction of near 9.08 x 10^-3, while recent nonlinear studies suggest significant corrections to the statistics of rare collapses at the scalar power achieved here.

The dielectric surface of the Moon provides an efficient interface for the conversion of dark matter dark photons into radio waves. This work explores a novel detection strategy that aims to capture this radio emission using standard radio telescope antennas. Detailed sensitivity projections are presented that demonstrate the power of this technique. It is found that both current and future radio observatories, including large arrays such as the Atacama Large Millimeter/submillimeter Array (ALMA) and the Square Kilometer Array (SKA), as well as large single dishes like the Five-hundred-meter Aperture Spherical Telescope (FAST) and the Green Bank Telescope (GBT), can explore a substantial and previously inaccessible parameter space for these dark matter candidates.

The mixed-mode trajectories arising from permutation-enforced $\lambda$-$\rho$ mode mixing are first investigated in the diquark picture. By accounting for the internal structure and substructure of baryons, we propose an approach to construct the mixed-mode Regge trajectories for baryons composed of three identical quarks. For triply heavy baryons $\Omega_{ccc}$ and $\Omega_{bbb}$, naive diquark-quark basis states without full permutation symmetrization violate the exchange symmetry required by the Pauli exclusion principle for three identical fermions; consequently, physical eigenstates arise as permutation-enforced $\lambda$-$\rho$ mode admixtures. Under the minimal-mixing assumption, we explicitly perform permutation symmetrization for the $J^{P}=(3/2)^{+}$ radially-excited S-wave states and construct mixed-mode Regge trajectory formulas for these symmetrized states. Unlike triply heavy baryons $\Omega_{ccb}/\Omega_{cbb}$ in the fixed diquark $(cc)b/(bb)c$ picture where well-defined pure $\rho$- and $\lambda$-trajectories exist, genuine pure-mode trajectories no longer survive for $\Omega_{ccc}$ and $\Omega_{bbb}$ due to permutation-driven cross-mode mixing. The resulting effective radial trajectories exhibit a novel sprouting-branch-like behavior. Both the original unmixed trajectories and the mixed-mode effective trajectories exhibit behavior of $M\sim x^{2/3}$ (where $x=n_r,\,N_r,\,n_r+N_r$). Radially excited masses are crudely estimated via the mixed-mode Regge trajectories, which show reasonable agreement with existing theoretical predictions.

Elastic scattering can generate entanglement and non-local magic between the spins of the two outgoing particles. The amount of entanglement and magic produced is encoded in the S-matrix; a unitary quantum gate that acts on the joint Hilbert space of the two spin-J particles. Previous work derived the entanglement power in terms of the scattering phase shifts for rotationally invariant S-matrices with J=1/2,1,3/2. In this paper, a closed form solution is derived for all J. We further prove that a broad class of non-local quantum resources depend to leading order only on the squared projective Hilbert-Schmidt distance from the nearest non-entangling gate. This holds for the entanglement power and non-local magic power, and the choice of resource simply changes the overall normalization. This universality establishes a common geometric origin for the leading resource-generating capacity of scattering, independent of the details of the interaction.

Much of the recent progress in machine learning domains such as language models has come from scaling laws that predict performance as a function of training effort. In high-energy physics (HEP) similar behavior has now been observed. To aid further study, we present a systematic procedure to derive robust scaling laws and compare design choices on the relevant budget axes for HEP tasks. We first validate the full scaling trajectory on toy problems and then apply the procedure to multi-task transformers on the ~11 billion-jet ATLAS JetSet2 dataset, in both the compute- and data-constrained regimes. For the latter, we predict, to the best of our knowledge for the first time, the jointly optimal model size, training horizon, learning rate and batch size under early stopping. At compute-optimal scaling, we recover a near-equal $\sqrt{C}$ dependence of model and dataset size, and find that auxiliary objectives lower the primary jet-classification loss at equal compute budget. Expanding the inputs toward lower-level data systematically lowers the loss while leaving the scaling exponent nearly unchanged. The onset of the power-law regime is itself set by scale: below a threshold in dataset size the loss carries little information about high-compute scaling, underscoring the value of large, high-quality full-simulation datasets as a foundation for scaling studies and the development of foundation models in HEP.

The 248 keV nuclear-recoil event observed by the LUX-ZEPLIN (LZ) experiment could potentially arise from dark matter (DM) interactions with nucleons. We investigate elastic scattering interpretation, focusing on Lagrangians that yield a local significance of $3\sigma$ or higher for some DM mass. We identify DM parameter space compatible with the LZ event and assess its consistency with collider constraints by recasting the ATLAS monojet plus missing-transverse-momentum search at $\sqrt{s}=13$ TeV, based on $139~\mathrm{fb}^{-1}$ of data. For most of the effective interactions, we find that LHC constraints exclude the DM interpretation of the LZ event for DM masses below $\lesssim\,$TeV subject to the effective field theory (EFT) validity. In particular, we derive, for the first time, LHC constraints on several explicit momentum-dependent Lagrangians, including $\mathcal{L}_{10}$. For many interactions, these constraints are sufficiently strong that the corresponding parameter space below DM mass $\lesssim\,$TeV may be challenging to probe even with future direct detection experiments. Our results, therefore, have broader implications beyond the interpretation of the LZ event itself.

In the standard three-flavor paradigm, two of the three neutrino mass-squared differences are independent. The existence of an additional dependence between these oscillation parameters was recently predicted on empirical grounds, taking the form $$\frac{\sqrt{\Delta m^2_{31}}+\sqrt{\Delta m^2_{21}}}{\sqrt{\Delta m^2_{31}}-\sqrt{\Delta m^2_{21}}}=\sqrt{2}.$$ The JUNO Collaboration has now reported the most precise measurements to date of both $\Delta m^2_{21}$ and $\Delta m^2_{31}$. We demonstrate that this relation is in excellent agreement with the experimental data, which yield $1.4143_{-0.0038}^{+0.0036}$ corresponding to a relative precision of $0.27\%$. Remarkably, the central value differs by less than $0.03$ standard deviations from the prediction ($\sqrt{2}\approx1.4142$). This provides strong experimental support for the novel constraint and thereby suggests an underlying symmetry governing the neutrino mass spectrum, rather than purely independent parameters.

The measure of indirect CP violation in the neutral kaon system, $\epsilon_K$, is an important precision test of the Standard Model. A first-principles Standard Model prediction of $\epsilon_K$ requires evaluating the long-distance contribution in which the $\Delta S = 2$ process proceeds via two $\Delta S = 1$ operators. The non-perturbative nature of QCD in the relevant energy regimes requires a lattice QCD simulation. In this paper we present the two-loop, $O(\alpha_s)$ RI/SMOM - $\overline{\text{MS}}$ matching factors required to renormalize a lattice QCD calculation of the long-distance contribution to $\epsilon_K$.

Studying vector boson polarisation has become an integral part of the LHC physics programme in recent years, as it provides an independent test of the electroweak symmetry-breaking mechanism and the gauge sector of the electroweak Standard Model. These measurements require polarised templates from parton-shower Monte Carlo simulations. Their accuracy does not yet meet the precision requirements of upcoming measurements, leading to significant modelling uncertainties in experimental analyses that will constrain the LHC's polarisation sensitivity at latest in the HL-LHC phase. Polarised loop-induced processes have so far not been included in most parton-shower event generators, despite contributing significantly to processes of interest. In this work, we present the extension of the polarisation framework in the Monte Carlo event generator SHERPA to polarised loop-induced processes at fixed LO and LO matched to parton shower. In addition to a description of the methodology based on polarised amplitudes from the RECOLA matrix element generator, we discuss polarisation effects in relevant inclusive, loop-induced processes and their jet-associated counterparts, several of them for the first time. Both the influence of different polarisation definitions and of QCD and QED resummation effects are investigated.

We present a phenomenological study of the longitudinal unpolarized structure function $F_{UU,L}$ in semi-inclusive deep inelastic scattering (SIDIS) and its ratio with the transverse structure function, $R_{\, \rm SIDIS}=F_{UU,L}/F_{UU,T}$. We study their transverse-momentum dependence, combining for the first time low- and high-transverse-momentum contributions across the kinematic range relevant to SIDIS measurements. At low transverse momentum, $F_{UU,L}$ is power suppressed, making it sensitive to next-to-next-to-leading-power dynamics in the unpolarized sector. We find that this contribution can be sizable, with $R_{\, \rm SIDIS}\simeq 0.3$ at low transverse momentum and hard scale, producing a correction of the order of $10\%$ to transverse-momentum-integrated observables. Although these estimates remain subject to theoretical uncertainties, our results indicate that accounting for $F_{UU,L}$ is likely to be important for the interpretation of SIDIS multiplicities and motivate dedicated measurements of $R_{\, \rm SIDIS}$ to better constrain the longitudinal contribution.

We investigate the longitudinal momentum distributions (LMDs) of the deuteron using a relativistic deuteron wave function derived from a realistic nucleon-nucleon (NN) interaction within the light-front framework. By convoluting the deuteron LMDs with the nucleon parton distribution functions (PDFs), we analyze the unpolarized, longitudinally polarized, and tensor-polarized structure functions of the deuteron. In addition, we also study the EMC effect in the weakly bound deuteron through the structure function ratio $F_{2}^{D}/(F_{2}^{p}+F_{2}^{n})$, which deviates from unity due to nuclear binding and Fermi motion effects.

We solve the functional renormalization group flow of the two-flavor quark-meson model at finite temperature and quark chemical potential with Litim's regulator, using the Kurganov–Tadmor central scheme and the standard grid method, both in the local potential approximation (LPA) and in an LPA$'$ truncation with running wave function renormalization factors for the pion, sigma, and quark fields. Using the Kurganov–Tadmor scheme as a high-resolution benchmark down to very low temperatures, where the Fermi surface produces the sharpest fronts in the field derivative of the potential, we find that, with sufficiently fine resolution, the grid method gives virtually identical results in both truncations. We discuss the difficulties that the wave function renormalization factors bring into the parametrization of the model and into the flow at finite density, related to the choice of the expansion point. Contrary to some expectations, the peculiar backbending of the first-order phase boundary at low temperature, known from LPA, persists in our implementation of the LPA$'$ truncation, both with a fixed and with a running expansion point.

We present a proof-of-concept study of neural ratio estimation (NRE) - a simulation-based inference algorithm - applied to WIMP direct detection using the XENONnT experiment as an example. A binary classifier is trained on simulated parameter-observation pairs to approximate the likelihood ratio for the WIMP mass $m_\chi$ and spin-independent proton coupling $c_p$, using realistic scintillation and ionization signals produced by the fuse detector simulation. We demonstrate that astrophysical uncertainties from halo model variations are marginalized over implicitly and at no additional inference cost by including multiple halo models in the training data. Using extreme $\pm5\sigma$ Standard Halo Model variations, we show that training on a combined dataset recovers well-calibrated posteriors even under severe misspecification, while more realistic halo models produce nearly indistinguishable results. The signal-plus-background classifier yields an exclusion limit that is both qualitatively and (after accounting for differences between frequentist and Bayesian approaches) quantitatively consistent with the XENONnT expected sensitivity. These results establish NRE as a scalable complement to the profile likelihood ratio approach, with particular advantages as experiments probe deeper into the neutrino fog.

We assess neutrino-assisted dark matter self-scattering in two scalar-mediator realizations by combining mediator-resolved potentials, numerical scattering calculations, thermal relic production, and the adopted observational constraints. In the $t$-channel case, the adopted laboratory and cosmological bounds suppress the neutrino force contribution at points reproducing the relic abundance and yielding sizable self-interactions, which are dominated by tree-level mediator exchange. Sommerfeld enhancement and early kinetic decoupling can change the relic abundance by up to 50% in the light mediator regime. In the $s$-channel case, thermal freeze-out fixes the coupling, leaving self-scattering well below the order of magnitude required for explanation of small-scale structure of the universe. An analytic upper envelope explains this shortfall of more than eleven orders of magnitude relative to the self-interacting dark matter benchmark. These results establish that, under the adopted constraints and thermal relic assumptions, the neutrino force cannot account for astrophysically relevant dark matter self-scattering in either realization.

To account for the soft transverse dynamics overlooked by the $k_T$ factorization formalism of exclusive QCD processes, we propose introducing the intrinsic transversal momentum distribution functions (iTMDs), in conjunction with the light-cone distribution amplitudes (LCDAs), to define the probability amplitude for finding a hadron state where partons move fast along the longitudinal axis while undergoing gentle oscillations in the transverse plane. We implement this framework in the calculation of the electromagnetic form factors of the pion and the proton. Our iTMDs-improved perturbative QCD predictions show good agreement with available experimental data and lattice QCD results. More importantly, we find that higher-twist, especially subleading-twist contributions, are indispensable for explaining the scaling behavior of both pion and proton form factors at intermediate momentum transfers. Furthermore, the inclusion of iTMD effects significantly improves the perturbative QCD predictions for the pion form factor in the few GeV$^2$.

Hadron resonances are intrinsically dynamical states whose observable properties are governed by the interplay between quark-model configurations and hadronic channels. Hamiltonian effective field theory provides a practical framework for connecting hadron dynamics with experimental observables and lattice QCD results. In this review, we outline the infinite- and finite-volume formulations of Hamiltonian effective field theory and survey its applications to light-hadron spectroscopy and resonance structure. By constraining the same Hamiltonian framework with experimental scattering data and lattice QCD spectra, Hamiltonian effective field theory can help distinguish among scenarios that describe the available scattering data comparably well but imply different roles for bare-state and multihadron configurations. We also review recent extensions of the Hamiltonian framework developed to address more complicated dynamical settings.

We compute the NNLO QCD contribution to the $N$-jettiness soft function for processes with two massive and an arbitrary number of massless final-state hard partons. The cancellation of all divergencies is demonstrated analytically. The finite remainder of the soft function is calculated numerically without an infrared regulator. The calculation employs the recently proposed method that uses the so-called inclusive $N$-jettiness variable to simplify the computation of the non-iterative contribution to the soft function.

We present an overview of the relativistic distorted-wave impulse approximation (RDWIA) for lepton-nucleus scattering, with emphasis on its use as an elementary-vertex model in event generators. In the intermediate-energy regime, neutrino-nucleus event generators typically follow a two-step scheme: an elementary neutrino-hadron interaction is first generated, and the outgoing hadrons are then propagated through the nuclear medium using an intranuclear cascade (INC) model. Using exclusive and inclusive $(e,e'p)$ and $(e,e')$ data for several nuclei, we assess how nuclear effects should be distributed between these two stages. In particular, we identify which effects should be included in the elementary-vertex description and which can be treated more effectively by the INC, while addressing the consistency required between both components. We also discuss nuclear transparency in quasielastic scattering. We show that it is directly connected to $(e,e'p)$ data below the two-nucleon knockout threshold; and depends on the full nuclear density distribution and the initial position of the nucleon, therefore, it varies substantially with the shell from which the nucleon is removed. We demonstrate that this shell dependence can be incorporated straightforwardly into the INC component of event generators.