Particle physics theory, phenomenology, and experiments
Considering $Z_4$ symmetry in Type I seesaw scenario, one could obtain mass-squared differences of light neutrinos, mixings and $CP$ violating phase within $3 σ$ confidence level based on neutrino oscillation data. This is possible with only three independent complex parameters for allowed Yukawa couplings and one real mass parameter for heavy right handed neutrino fields around electroweak scale. After considering only three more real parameters as coming from small soft-symmetry breaking terms, the lightest right handed neutrino could be considered as dark matter candidate via freeze-in mechanism and the other two heavier right handed neutrinos through their decays, could generate the baryonic asymmetry of the universe naturally via resonant leptogenesis.
We extend a recently developed Big Bang Nucleosynthesis (BBN) code, {\tt PRyMordial}, to constrain a broad class of Grand Unified Theories to which BBN is sensitive, since these lead to varying fundamental couplings. A previously developed self-consistent perturbative analysis of the effects of these variations has been implemented in {\tt PRyMordial}, leading to robust constraints of the value of the fine-structure constant, $α$, at the BBN epoch using current observations of Helium-4 and Deuterium abundances. We explored two different viable scenarios, relying on alternative assumptions on the gravitational sector: the variation of the gravitational coupling can be implemented by varying either particle masses, or Newton's gravitational constant. For the variation of masses, we obtained at $68\%$ confidence level a constraint on the relative variation of $α$, between the BBN epoch and the present-day laboratory value, of $Δα/α=2\pm51$ ppm (parts per million), while for the variation of Newton's constant the analogous constraint is $Δα/α=2\pm22$ ppm. We also show that, given these constraints, these models do not provide a solution to the cosmological Lithium problem.
We present a comprehensive Bayesian study of the $B_c$ meson spectrum using non-relativistic Cornell and logarithmically modified Cornell potentials, introducing the logarithmic term as the minimal deformation that preserves short-range Coulombic and long-range linear confinement while adding controlled flexibility at intermediate distances to probe the sensitivity of higher excited states to the confining form. Model parameters are sampled via Markov chain Monte Carlo (MCMC), enabling rigorous propagation of correlated uncertainties to all predictions. Spin-dependent interactions are treated perturbatively, with unequal heavy-quark masses accounted for consistently. Both potentials reproduce the known states within uncertainties, with small errors for low-lying states that grow for higher radial and orbital excitations. Analyzing radial and orbital Regge trajectories using linear and nonlinear parametrizations, we observe pronounced nonlinearity for low $S$-waves trending toward linearity at higher excitations. The modified potential yields modest, systematic shifts in higher excited states, reflecting the logarithmic correction's impact. We provide updated theoretical predictions for excited $B_c$ states with uncertainties, serving as benchmarks for ongoing and future experiments.
Simulating lattice gauge theories on quantum computers presents unique challenges that drive the development of novel theoretical frameworks. The orbifold lattice approach offers a scalable method for simulating SU($N$) gauge theories in arbitrary dimensions. In this work, we present three improvements: (i) two new simplified Hamiltonians, (ii) an encoding of the SU(2) theory with smaller number of qubits, and (iii) a reduction in the requirement for large scalar masses to reach the Kogut-Susskind limit, achieved via the inclusion of an additional term in the Hamiltonian. These advancements significantly reduce circuit depth and qubit requirements for quantum simulations. We benchmarked these improvements using Monte Carlo simulations of SU(2) in (2+1) dimensions. Preliminary results demonstrate the effectiveness of these developments and further validate the use of noncompact variables as a promising framework for scalable quantum simulations of gauge theories.
In the present work, we systematically investigate the meson-baryon molecular properties of the hidden charm pentaquark states $P_c$ and $P_{cs}$ within a coupled channel framework that combines heavy quark spin symmetry and the local hidden gauge formalism. By solving the Bethe-Salpeter equation with the momentum cutoff method, we obtain the pole trajectories, wave functions, and root-mean-square radii. For the hidden charm system, the full coupled channel interactions respecting the heavy quark spin symmetry are essential to generate the $P_c$ states, as they significantly affect the poles' widths. The dominant bound channels are $\bar{D} Σ_c$ and $\bar{D}^* Σ_c$, which couple strongly to lower decay channels. In contrast, for the hidden charm strange system, the full heavy quark spin symmetry treatment is not necessary, where the splitting PB and VB sectors yield similar results. The main bound channels $\bar{D} Ξ_c$ and $\bar{D}^* Ξ_c$ couple strongly to $\bar{D}_s Λ_c$ and $\bar{D}_s^* Λ_c$, respectively, but only weakly to the lower decay channels, differing from the hidden charm case. The trajectories of the pole widths for the loosely bound channels $\bar{D} Ξ'_c$, $\bar{D}^* Ξ'_c$, and $\bar{D}^* Ξ_c^*$ exhibit distinct behaviors. Notably, all the primary bound channels have similar binding energies in the single channel interactions due to equally attractive potentials. Furthermore, we also calculate the wave functions and root-mean-square radii of the corresponding poles. The wave functions are localized within $0\sim 6$ fm and vanish fast beyond $4$ fm. The root-mean-square radii, evaluated by two consistent methods, typically lie between $0.5$ and $2$ fm, comparable to the characteristic scale of molecular states.
2604.04817In higher-dimensional Einstein-AdS gravity, it is well known that planar and static anti-de Sitter black holes can be endowed with multiple rotation parameters via a large-gauge transformation. However, a similar prescription fails when multiple NUT parameters are added, thereby obstructing the study of holographic properties with more than one NUT charge. To pave the way towards this direction, we construct explicit planar AdS spacetimes having multiple NUT parameters in two simple ways that allow one to circumvent the strong restrictions imposed by the vacuum field equations. First, motivated by momentum relaxation holographic models, we construct multi-NUT spaces in AdS with flat horizons by adding free scalar fields possessing an axionic profile. In our second approach, we build similar configurations in Einstein gravity with quadratic-curvature corrections. As a byproduct, we end by presenting planar versions of the Kaluza-Klein monopole in AdS with different magnetic charges.
We present a constituent two-gluon description of the lowest-lying glueball states in pure Yang--Mills theory, calibrated against quenched lattice results. The framework incorporates an instanton-induced dynamical gluon mass, Casimir-scaled adjoint confinement, the short-distance adjoint Coulomb interaction, and instanton-induced central and tensor forces. The scalar $0^{++}$ glueball is found to be exceptionally compact, with a radius of order the instanton size, $ρ\sim \frac 13\,\mathrm{fm}$, consistent with lattice indications. By contrast, the tensor $2^{++}$ state remains spatially extended due to the centrifugal barrier. We also discuss the role of $S$-$D$ mixing. A semiclassical analysis further supports Regge behavior for excited states, in agreement with lattice results.
2604.04774We investigate Hawking radiation in noncommutative spacetime. For a dynamical black hole formed by the collapse of a matter shell, we demonstrate that spacetime noncommutativity modifies the interaction between the radiation field and the background geometry. In particular, the collapsing shell is effectively shifted by an amount proportional to the momentum of an outgoing Hawking mode. While the nonlocality inherent in noncommutative spacetime invalidates the conventional arguments for the robustness of Hawking radiation, the radiation decays substantially after the scrambling time, resulting in an exponentially long evaporation time.
We construct simple analytical solutions of renormalization group equations for the running coupling and for the Green functions in QCD in the asymptotic regime. These solutions have an explicit form and subsequently sum up the leading, subleading, and so on logarithms in all orders of PT. They easily reproduce the inverse logarithm expansion and allow for further summation and improvement of the asymptotic behaviour.
This document summarizes the discussions at the program "Precision QCD with the Electron Ion Collider", held from May to June 2025 at the Institute for Nuclear Theory (INT) at the University of Washington. The program was co-sponsored by the INT and by the Center for Frontiers in Nuclear Science (CFNS, Stony Brook University). Over its five-week duration it brought together about 70 theorists, experimentalists and computer scientists all interested in the physics program at the future Electron Ion Collider in preparation at Brookhaven National Laboratory. Key topics at the program were: higher-order perturbative-QCD calculations and techniques; nuclear structure and tomography; comparisons of phenomenological and lattice determinations of parton distribution functions; identification of signature observables for saturated gluons; assessment of the importance of AI techniques for EIC studies and detector development.
High-precision determinations of Cabibbo-Kobayashi-Maskawa (CKM) matrix elements are essential probes of physics Beyond the Standard Model (BSM). Current precision tests show a deficit in the first row unitarity relation. At the current level of precision, the only relevant CKM matrix elements that contribute to this test are $|V_{ud}|$ and $|V_{us}|$. Without resorting to nuclear inputs, they can be extracted from the combination of the experimental decay width of kaon and pion leptonic decays, along with the theoretical calculation of their decay constants; combined with the decay width of semileptonic kaon decays, with the computation of the corresponding form factor at zero momentum transfer. We review current efforts by the Fermilab Lattice and MILC collaborations towards a correlated analysis of the lattice inputs needed for this test using Highly Improved Staggered Quarks (HISQ) on the $N_f=2+1+1$ MILC configurations along with Staggered Chiral Perturbation Theory (SChPT) as a functional form for the chiral-continuum limit.
While supersymmetric models provide a solution to the big hierarchy problem, natural SUSY is also allowed by the little hierarchy problem. In supersymmetric models which include the Peccei-Quinn (PQ) solution to the strong CP problem, one expects the presence of an axion-axino-saxion supermultiplet with a micro-eV-scale axion and a saxion with mass of order the soft breaking scale. The axino mass is much more model-dependent, and may occur in the range of keV-TeV: over 9 orders of magnitude. This leads to the possibility of the axino as lightest SUSY particle (LSP) and the presence of mixed axion plus axino dark matter. The case of natural SUSY with higgsino-like WIMPs as LSP seems (nearly) excluded by multi-ton noble liquid WIMP detector limits, even in the case where the LSP has a depleted abundance compared to axions. We examine the case where the axino is LSP leading to mixed axion-axino dark matter in a natural SUSY context. We map out regions of PQ scale f_a vs. axino mass m_{\ta} parameter space where such a scenario remains viable in both the SUSY DFSZ and KSVZ axion models. For axino mass ~100 keV, we find solutions in accord with the measured dark matter abundance with mainly warm axino dark matter for f_a~ 10^{11} GeV and also solutions with mainly axion cold DM and a tiny axino contribution for higher f_a~ 3\times 10^{12} GeV.
It is shown that a duplication of the hypercharge, which is identical for the normal sector but different for the dark sector, may manifestly address neutrino mass and dark matter.
In recently proposed framework of non-holomorphic modular symmetry introduces the concept of negative and zero modular weight of Yukawa couplings. These Yukawa couplings are function of complex modulus $τ$, which is responsible for the CP asymmetry produced during leptogenesis. In this work, we restrict the $τ$ on the fixed points of modular symmetry rather than its fundamental domain in such manner Yukawa couplings are also get fixed. We have adopt this framework and propose a type III seesaw mechanism. The model is tested against neutrino oscillation data through a $χ^2$ analysis using NuFIT~6.1. To test the stability of these predictions, we also analyze regions near each fixed point by introducing a deviation $τ\rightarrow τ_{\rm fixed}(1 + εe^{iφ})$ with $ε\in (0,0.1)$ and $φ\in (-π,π)$. Our results show that certain fixed points, along with their nearby regions, are capable of producing viable neutrino phenomenology while also generating the observed baryon asymmetry of the Universe.
2604.04569In gauge theories, the mass of a field has been regarded as a purely on-shell concept: the pole mass is gauge-invariant, but the off-shell propagator has had no gauge-invariant definition of mass. We show that renormalization defines a gauge-invariant mass function at every virtuality, together with a gauge-invariant vertex. The virtual particle becomes as well defined as the on-shell one: the distinction is not dynamical but purely kinematic.
Compact astrophysical objects, such as neutron stars, can provide a unique environment where the interplay between strongly interacting nuclear matter and dark matter (DM) can yield possible observable signatures. We investigate here the impact of fermionic DM interacting with nucleons via a vector mediator ($Z^\prime$) portal inside neutron stars using the relativistic mean field (RMF) framework. Unlike scalar portal DM models, which primarily modify the effective nucleon mass through scalar interactions, vector mediators introduce additional repulsive interactions that directly affect the baryonic chemical potential and the pressure of dense matter. We show that the precise measurements of neutron star properties, including the mass radius relation and tidal deformability from gravitational wave observations, X-ray and radio observations of pulsars, can shed light on properties of DM. We study the gross structural properties of a neutron star using the Tolman Oppenheimer Volkoff (TOV) equations, employing an equation of state (EOS) for neutron star matter in the presence of vector portal-assisted DM. The resulting stellar configurations consistent with observational bounds from gravitational wave observations in LIGO/Virgo, and X-ray observations of pulsars in NICER, are shown to constrain the vector portal DM parameters. It is observed that, while large portal mass can soften the EOS of the DM admixed neutron star matter, the light portal mass can make the EOS stiffer at large densities resulting in distinct mass-radius relation and the tidal deformability between the two scenarios. The vector portal DM scenario, with DM interaction with quarks via $Z^\prime$ vector boson, can establish a direct connection to terrestrial searches, including direct and indirect detection and collider searches for the $Z^\prime$ boson.
Detectors designed for the International Linear Collider have been studied over many years, and a good understanding of the relevant requirements and constraints has been developed. With the prospect of future Higgs Factory projects with different properties (for example, the FCC-ee), the adaptations required for use at such facilities are being investigated. We outline our current understanding in this note.
We study oscillon/I-ball solutions in a real scalar version of the Friedberg-Lee-Sirlin (FLS) model. Using the two-timing analysis, we derive the conditions for oscillon solutions and explore multi-field oscillon configurations. In these configurations, the two fields form co-located oscillons that oscillate with frequencies set by their respective masses. These multi-field oscillons can be viewed as a bound state of two oscillons due to attractive interactions between the fields. We confirm these analytical predictions through numerical lattice calculations. This work extends the standard picture of single-field oscillons and may be relevant for cosmological scenarios involving multiple interacting real scalar fields.
We study chimera baryons, fermion bound states composed of two (hyper)quarks transforming in the fundamental and one in the antisymmetric representation of a non-Abelian gauge group. While in QCD they coincide with ordinary baryons, in composite Higgs models (CHMs) with top partial compositeness, spin-1/2 chimera baryons serve as partners of the top quark and are responsible for its large mass. We perform non-perturbative lattice calculations of the low-lying spectrum of the chimera baryons, in a specific realization of CHMs based on a Sp(4) gauge theory. In the quenched approximation, we present the numerical results in the continuum and massless limits. Then, for dynamical fermions, we measure the spectrum and matrix elements by employing a newly developed spectral density analysis for several choices of the lattice parameters.
We investigate D-insatnton effects on the holographic Weyl semimetal in top-down approach. From the free energy of the D7 brane embedding solutions, we get phase diagram in terms of the electron mass, instanton number, and temperature in the unit of the weyl parameter. We calculate non-linear conductivities from the regularity condition of the probe D7 brane and investgate anomalous Hall phenomena in the boundary system. From the study of the phase diagram, we suggest the gaped phase induced by the instanton to a topological insulator.