High Energy Physics - Phenomenology

arXiv:hep-ph

Theoretical particle physics, extensions of Standard Model, predictions for experiments.

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High Energy Physics - Phenomenology Papers (hep-ph) - ScienceStack

Trending in High Energy Physics - Phenomenology

Qubits and Vacuum Amplitudes

High-energy colliders, such as the Large Hadron Collider (LHC) at CERN, are genuine quantum machines, so, in line with Richard Feynman's original motivation for Quantum Computing, the scattering processes that take place there are natural candidates to be simulated on a quantum system. Potential applications range from quantum machine learning methods for collider data analysis, to faster and more precise evaluations of intricate multiloop Feynman diagrams, more efficient jet clustering, improved simulations of parton showers, and many other tasks. In this work, the focus will be on two specific applications: first, the identification of the causal structure of multiloop vacuum amplitudes, a key ingredient of the Loop-Tree Duality and an area with deep connections to graph theory; and second, the integration and sampling of high-dimensional functions. The latter constitutes a first step toward the realization of a fully fledged quantum event generator operating at high perturbative orders.

2601.00722

Jan 2026High Energy Physics - Phenomenology

Sommerfeld Enhancement from Background Force and the Galactic Center GeV Excess

We study the impact of background-induced forces on dark matter (DM) annihilation and their implications for indirect detection. In the presence of a finite number density of background particles, loop-level interactions can generate an effective force that is significantly enhanced relative to the vacuum case. We construct a two-component DM model in which the dominant component is a fermionic particle $χ$ and the subdominant component is an ultralight pseudoscalar particle $φ$. The annihilation of $χ$ proceeds through the p-wave channel and produces gamma-ray emission. The finite density of $φ$ particles induces a background-enhanced force between $χ$ particles, leading to a sizable Sommerfeld enhancement of the annihilation. We show that a viable region of parameter space in this model can account for the gamma-ray excess observed in the Galactic Center using Fermi-LAT data. The background-induced force substantially amplifies the Sommerfeld enhancement and thus enlarges the parameter space capable of explaining the excess, highlighting the importance of background effects in astrophysical environments.

2512.24188

Dec 2025High Energy Physics - Phenomenology

Cosmic Ray Simulation with PYTHIA

We present recent developments in PYTHIA for the modelling of hadronic cascades in a medium. Several improvements have been made in the Angantyr model for collisions with nuclei, especially in the limit of low collision energies, allowing it to be used throughout the hadronic cascades. Also the simplified nuclear model in the PythiaCascade} module has been updated. We find that the two models give consistent results for cosmic ray air showers initiated by both high energy protons and nuclei.

2512.13326

Dec 2025High Energy Physics - Phenomenology

2512.02673

Chen Ning Yang Retrospective

Chen-Ning Yang made important contributions to the theory of solvable models in statistical mechanics, including generalizations of the Bethe Ansatz, magnetization in the Ising model, the Lee-Yang circle theorem, and the Yang-Baxter equation. Most famously, Yang made transformative contributions to the current Standard Model of elementary particle interactions. The proposal of Yang and T. D. Lee, that left-right symetry (parity) is violated in weak particle decays, established that the primary currents involved in weak interactions are left handed. The work of Yang and R. L. Mills gave a framework for force carriers coupling to these currents that are non-Abelian generalizations of the electromagnetic photon, which unlike the electrically neutral photon, carry ``charges'' to which they self-couple . Two decades of work by others on quantization and mass-generation mechanisms then culminated in the Standard Model.

2512.02673

Dec 2025High Energy Physics - Phenomenology

Resonant Annihilation of WIMP Dark Matter for Halo Gamma Ray Signal

We propose a resonant annihilation as a way to reconcile the WIMP annihilation cross sections in a recently reported gamma ray signal from the Milky Way halo with that for the freeze-out and the upper limit from dwarf galaxies. We perform a simple model-independent analysis based on this hypothesis and determine the required parameters. We also present a simple particle-physics model that can accommodate them.

2512.014041

Dec 2025High Energy Physics - Phenomenology

2512.01961

Towards Precision Gluon Densities at Small $x$: From Resummation to Collider Observables

Accurate gluon densities at small $x$ are essential for reducing theoretical uncertainties in collider predictions, yet remain one of the least constrained ingredients in global analyses. We report recent advances in the resummation of small-$x$ logarithms in the gluon sector, focusing on collinear distributions and their interplay with transverse-momentum-dependent formulations. Particular attention is paid to the impact of gluon-proton spin correlations and to the emergence of unintegrated gluon densities derived from resummed dynamics. These developments aim to fill the current precision gap in the small-$x$ region and enable robust applications to LHC and future-collider observables.

2512.01961

Dec 2025High Energy Physics - Phenomenology

Two-loop all-plus helicity amplitudes for self-dual Higgs boson with gluons via unitarity cut constraints

We present the two-loop amplitudes for a self-dual Higgs boson with up to four positive helicity gluons in the heavy top-quark limit. Because the tree amplitudes in the all-plus sector vanish, we can construct simple representations of the polylogarithmic parts of the two-loop amplitudes using four-dimensional unitarity cuts into rational one-loop and tree amplitudes. The remaining rational function ambiguity is extracted from a tensor integral reduction over finite fields. The final expressions are presented using polylogarithms up to weight two and compact rational functions of spinor-helicity products.

2511.11537

Nov 2025High Energy Physics - Phenomenology

Effects of Early-Universe Inhomogeneity on Bubble Formation: Primordial Black Holes as an Extreme Case

Our early Universe is not perfectly homogeneous and it may contain some inhomogeneous sources, which might distort the local spacetime and modify the bubble nucleation rate. Taking the primordial black hole as an extreme example, we investigate the bubble nucleation rate of a first-order phase transition in the vicinity of primordial black holes or other primordial gravitational sources. Our analysis reveals that the presence of primordial black holes can reduce the effective action and might modify the nucleation rate due to their gravitational effects, potentially altering the dynamics of the phase transition in the early universe and producing new gravitational wave signals since the gravitational effects of the primordial black hole or other possible inhomogeneous sources could lead to nucleation of non-spherical symmetric bubbles.

2511.11408

Nov 2025High Energy Physics - Phenomenology

Double virtual QCD corrections to $t\bar{t}+$jet production at the LHC

We present a leading colour computation of the double virtual contributions to top-quark pair production in association with a jet at a hadron collider at next-to-next-to-leading order in QCD. The finite remainders of the two-loop amplitudes, after subtraction of infrared and ultraviolet divergences, are extracted analytically from evaluations over finite fields by using a (potentially) overcomplete basis of special functions defined through their differential equations. We construct the colour- and spin-summed interference with the tree-level amplitudes and present a \texttt{C++} library suitable for immediate use in phenomenological studies. We present new techniques for the evaluation of the special functions through direct numerical integration of differential equations which perform well across the full physical phase space.

2511.114243

Nov 2025High Energy Physics - Phenomenology

Toward a holographic realization of the 2+1-flavor QCD phase structure

We present a fully back-reacted Einstein--Maxwell--Dilaton--flavor model with dynamical light and strange sectors, calibrated to lattice QCD using a machine-learning--assisted spectral method. The model reproduces the 2+1-flavor equation of state and chiral dynamics with quantitative accuracy, and maps the Columbia plot with a tri-critical point at $m_s^{\mathrm{tri}} \simeq 21~\text{MeV}$ and a critical mass $m_c \simeq 0.785~\text{MeV}$, consistent with lattice results. At finite density, it yields a crossover-to-first-order transition and predicts a critical endpoint at $T_C = 75.4~\text{MeV}$ and $μ_C = 768~\text{MeV}$, within the reach of heavy-ion experiments. These findings establish a unified holographic framework for the QCD phase structure across quark masses and baryon density, providing the first consistent and quantitative description of both deconfinement and chiral transitions within a single holographic model.

2511.112731

Nov 2025High Energy Physics - Phenomenology

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High Energy Physics - Theory High Energy Physics - Experiment High Energy Astrophysical Phenomena Nuclear Theory General Relativity and Quantum Cosmology

11,065 papers

Complete NLO BFKL impact factors for quarkonium hadroproduction in NRQCD: the case of ${}^1S_0^{[1]}$, ${}^1S_0^{[8]}$, and ${}^3S_1^{[8]}$ states

We present the first complete next-to-leading order calculation of the impact factors for hadroproduction of $S$-wave quarkonium states within the BFKL formalism. We present the computation of the real-emission contributions which completes the recent one of one-loop virtual corrections by one of us for the impact factors for the ${}^1S_0^{[1]}$, ${}^1S_0^{[8]}$, and ${}^3S_1^{[8]}$ NRQCD states. We prove the cancellation of soft divergences between real and virtual contributions, and that the surviving collinear singularities are compatible with factorisation up to one loop for a novel class of processes where BFKL resummation can be applied. Our work indeed represents the first complete NLO quarkonium impact factor in the BFKL framework and paves the way to first next-to-leading-logarithmic-precision studies for hadroproduction of forward-backward quarkonium associated production at hadron colliders.

2601.04142Jan 2026

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Effect of event classification on the Tsallis-thermometer

We analyze identified hadron spectra in pp collisions at $\sqrt{s} = 13$ TeV measured by ALICE within a non-extensive statistical framework. Spectra classified by multiplicity, flattenicity, and spherocity were fitted with the Tsallis-Pareto distribution, and the parameters were studied on the Tsallis-thermometer. Multiplicity and flattenicity classes follow a previously observed scaling, while the non-extensivity parameter shows a distinct sensitivity to the spherocity. A data-driven parametrization confirms a proportionality between the Tsallis temperature and mean transverse momentum, offering a simple estimate of the effective temperature. These results highlight the ability of the Tsallis-thermometer to capture both multiplicity and event-shape effects, linking soft and hard processes in small systems.

2601.04106Jan 2026

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Axion Masses as an Inevitable Consequence of Supersymmetry Breaking

We investigate a supersymmetric framework in which soft supersymmetry-breaking effects provide the dominant origin of Peccei--Quinn (PQ) symmetry breaking and axion mass generation. In the supersymmetric limit the theory possesses an exact PQ symmetry and a massless axion, while the inclusion of soft terms proportional to the gravitino mass induces spontaneous PQ breaking, stabilizes the saxion direction, and generates a mass for the axion. As a consequence, the axion, saxion, and axino masses are all controlled by the supersymmetry-breaking scale, leading to a correlated and predictive spectrum of axion-like states. The presence of explicit soft PQ-breaking terms raises the question of vacuum alignment and CP violation. We show that although the axion mass does not originate from QCD instantons, the induced strong CP phase is parametrically suppressed by the hierarchy between the QCD-induced and soft-induced axion masses. As a result, the explicit breaking does not generate an observable CP-violating vacuum angle across the parameter space of interest. We analyze the phenomenological implications of this scenario, including axion lifetimes, axion--photon couplings, and laboratory, astrophysical, and cosmological constraints. Direct confrontations with beam-dump and collider searches, together with Big Bang nucleosynthesis bounds, demonstrate that a substantial region of parameter space remains viable and testable. The framework thus provides a self-consistent and phenomenologically rich realization of axion-like particles whose masses arise predominantly from soft supersymmetry breaking.

2601.04017Jan 2026

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Beyond Form Factors: Precise Angular Tests in Hadronic $τ$ Decays

Semileptonic $τ$ decays mainly proceed via interactions between charged lepton and quark currents. The hadronization of the quark current is intrinsically nonperturbative and generally cannot be addressed analytically. In these proceedings, we propose using symmetry arguments alone to construct clean angular observables, which, within the Standard Model and in the absence of long-distance electromagnetic corrections, remain form-factor independent. These predictions can be experimentally tested, and any observed deviation could signal either effects of physics beyond the Standard Model or provide a clean benchmark for long-distance electromagnetic corrections. We also perform a first estimate of the expected impact of new physics in an EFT framework.

2601.03912Jan 2026

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Topological quantization of vector meson anomalous couplings

We uncover a new anomalous term in hidden local symmetry that enforces the topological quantization of vector-meson anomalous couplings. Unlike existing formulations in the literature, which introduce several unquantized coefficients, our term removes this freedom by fixing the couplings to quantized, topologically determined values. We further conjecture that it saturates the anomaly, explaining the success of vector-meson dominance while pinpointing where saturation must fail. High-precision measurements of $η^{(\prime)}\toπ^+π^-γ^*$ form factors at BESIII and the Super $τ$-Charm Facility can provide a definitive experimental discriminator of this quantized picture.

2601.03740Jan 2026

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Addicted to Flavour: 1976-2026

I describe my activities in Flavour Physics from 1976 to 2026. However, this 50th anniversary is not the only motivation for this writing. The second reason is the 350th anniversary of the discovery of the first animalcula by van Leeuvanhoek in 1676. Flavour physics makes it possible to search for new animalcula at distance scales far shorter than those resolved by van Leeuwenhoek in 1676 and even shorter than those directly accessible at the Large Hadron Collider. Achieving this goal requires not only precise measurements of a wide variety of processes, but also equally precise theoretical calculations, both within the Standard Model (SM) and beyond it. In this respect, next-to-leading-order (NLO) and next-to-next-to-leading-order (NNLO) QCD calculations of various Wilson coefficients in the SM and beyond it, in which I was involved for two decades, as well as reliable treatments of non-perturbative QCD effects, are indispensable. Equally important is the proper choice of observables that are best suited to revealing these new animalcula of particle physics. Moreover, in my view it is crucial to develop strategies for the search for New Physics (NP) that go beyond the global fits that are very popular today. While effective field theories such as WET and SMEFT are formulated in terms of Wilson coefficients of the relevant operators, with correlations characteristic of the SM and of specific NP scenarios, the most direct tests of the SM and its extensions are, in my opinion, correlations among different observables that are characteristic of particular new animalcula at work. Numerous colourful plots in this article illustrate this point. I hope that these ideas are clearly conveyed in my Flavour Autobiography, which also includes my memories of many conferences, workshops, and schools, as well as related anecdotes that are not always directly connected to physics.

2601.03722Jan 2026

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Chiral anomaly: from vacuum to Columbia plot

We use a low-energy effective approach, the extended linear sigma model, to study realizations of the $U(1)_A$ anomaly with different operators, linear and quadratic in the 't Hooft determinant. After discussing the parameterization in agreement with vacuum's phenomenology, we investigate the influence of these different anomaly terms on the Columbia plot: the square of the 't Hooft determinant favors a cross-over for small quark masses. Finally, we also discuss the extension of the 't Hooft determinant to cases in which different mesonic multiplets interact with each other. Novel chiral anomalous interaction terms involving excited (pseudo)scalar states, pseudovector, and pseudotensor mesons are expressed via a mathematical extension of the determinant, denoted as a polydeterminant.

2601.03710Jan 2026

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Why is the $Z_c(3900)$ absent in the $h_cπ$ final state?

In this work, we perform a comprehensive phenomenological analysis of the exotic hadronic states $Z_c(3900)$, $Z_c(4020)$, $Z_b(10610)$ and $Z_b(10650)$ within the framework of Heavy Quark Spin Symmetry (HQSS) and its violation. By constructing S-wave contact interactions between elastic ($D\bar{D}^*/D^*\bar{D}^*$ or $B\bar{B}^*/B^*\bar{B}^*$) and inelastic ($J/ψπ, h_cπ$ or $Υπ$, $h_bπ$) channels, we solve the Lippmann-Schwinger equation to obtain physical production amplitudes and perform a global fit to experimental invariant-mass spectra. Our results demonstrate a striking difference between the charm and bottom sectors: HQSS violation is negligible in the bottom system, leading to comparable peak structures for both $Z_b$ states in all hidden-bottom decay channels. In contrast, significant HQSS breaking is required to describe the $Z_c$ system, where the violation is predominantly concentrated in the elastic interactions. This explains the observed selectivity: $Z_c(3900)$ appears prominently only in $J/ψπ$, while $Z_c(4020)$ appears only in $h_cπ$. Pole analysis confirms the molecular nature of the states, with the $Z_c(4020)$ likely arising from a threshold cusp effect. The model's robustness is verified against variations of the form factor and cutoff, showing stable results.

2601.03697Jan 2026

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Role of $Σ(1660)$ in the $K^- p \toπ^0π^0Σ^0$ reaction

The processes of $K^-p \to π^0 π^0 Σ^0$ and $K^- p \to π^0 Λ(1405)$ are studied within the effective Lagrangian approach. In addition to the ``background" contribution from the $u$-channel nucleon pole term, contribution from the $Σ(1660)$ resonance with spin-parity $J^P=1/2^+$ is also considered. For the $K^-p \to π^0 π^0 Σ^0$ reaction, we perform a calculation for the total and differential cross sections by considering the contribution from the $Σ(1660)$ intermediate resonance decaying into $π^0 Λ(1405)$ with $Λ(1405)$ decaying into $π^0 Σ^0$. With our model parameters, the available experimental data on both the $K^-p \to π^0 π^0 Σ^0$ and $K^- p \to π^0 Λ(1405)$ reactions can be fairly well reproduced. It is shown that we really need the contribution from the $Σ(1660)$ resonance, and that these experimental measurements could be used to determine some properties of the $Σ(1660)$ resonance.

2601.03692Jan 2026

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Fully-strange tetraquarks: fall-apart decays and experimental candidates

We presents a systematic analysis of the fall-apart decays for the $1S$, $1P$, and $2S$-wave fully-strange tetraquark states. It shows that most of the fully-strange tetraquark states have a relatively narrow fall-apart decay width of $\mathcal{O}(10)$ MeV. The newly observed axial-vector state $X(2300)$ at BESIII may favor the low-lying $1S$-wave $1^{+-}$ state $T_{(4s)1^{+-}}(2323)$, while the $X(2500)$ resonance observed in the earlier BESIII experiment may favor the low-lying $1P$-wave $0^{-+}$ state $T_{(4s)0^{-+}}(2481)$. Some fully-strange tetraquark states predicted in theory can be searched for in their dominant fall-apart decay channels in experiment, such as $φφ$, $φφ(1680)$, $η^{(\prime)}φ$, $η^{(\prime)}h_1(1415)$, and $φf_2^{\prime}(1525)$, to which they have relatively large couplings.

2601.03614Jan 2026

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A Direct Algebraic Pathway to Hadronic Observables in the Contact Model

We present a novel algebraic framework for computing hadron properties directly within the contact interaction model. Utilizing Fierz transformations, the method recasts the Bethe-Salpeter dynamics into equations for a minimal set of \emph{projected amplitudes} for bound-state static properties and form factors, bypassing the conventional need for the meson wave function. This approach is fully demonstrated for the vector meson, enabling the direct extraction of its decay constants and form factors. The formalism provides a more efficient and unified pathway to hadron observables, with clear potential for extension to baryons and more sophisticated interactions.

2601.03514Jan 2026

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Estimating JUNO's Sensitivity to Solar Neutrino-to-antineutrino Conversion and Neutrino Magnetic Moments

We investigated JUNO's sensitivity to a possible conversion of solar neutrinos into antineutrinos via the spin-flavor precession (SFP) mechanism, and assessed the implications for constraining the neutrino-magnetic moment (NMM). Using a sensitivity-based framework appropriate for counting experiments with no prior observations, we derive 90\% C.L.\ ensemble-average sensitivities on the solar antineutrino flux for 1.8--16.8 MeV and 8.0--16.8 MeV. For the entire energy window, the results do not improve the restrictions of other experiments; the relevance occurs in the highes-energy window. In this window, we report a flux of $φ_{\mathrm{lim}}\le 4.01\times10^{1}\ \mathrm{cm^{-2}\,s^{-1}}$ and a probability of $P_{ν_e\rightarrow\barν_e}\le 2.07\times10^{-5}$, the latter normalized to the ${}^8$B flux above threshold, $Φ_{\rm SSM}(E>8~\mathrm{MeV})$. Assuming transverse solar magnetic fields of $B_\perp=50$ and $100$~kG, the corresponding magnetic-moment sensitivities are $μ_ν\le 7.27\times10^{-11}\,μ_B$ and $3.64\times10^{-11}\,μ_B$ in the high-energy window. These results highlight that JUNO has the potential to achieve sensitivities comparable to the most stringent astrophysical limits; in particular, the high-energy selection (8.0--16.8~MeV) provides a sensitivity that is competitive with current results, while the full-energy window remains primarily limited by near-reactor backgrounds.

2601.03502Jan 2026

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Sterile Neutrino Dark Matter as a Probe of Inflationary Reheating

Sterile neutrinos offer a minimal and testable explanation for dark matter (DM), with their radiative decay actively searched for in X-ray observations. We show that cold sterile neutrino DM can be efficiently produced during reheating from inflaton decays with a tiny branching ratio, ${\rm BR}\lesssim 10^{-4}$. This production mechanism opens regions of parameter space where the active-sterile mixing is small enough to evade current X-ray constraints while reproducing the observed DM abundance. We systematically map the viable parameter space in terms of the sterile neutrino mass, mixing angle, inflaton mass, reheating temperature, and branching ratio. We further demonstrate that sterile neutrino DM can serve as a probe of inflationary reheating, with future X-ray observations capable of setting lower bounds on the reheating temperature several orders of magnitude above the existing bound from Big Bang Nucleosynthesis.

2601.03346Jan 2026

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Flavor physics at the EIC with b-jet tagging

We employ an approximate conserved quantum number (defined as "$b$-Parity" in [1]) of the Standard Model (SM): $b_P=(-1)^n$, where $n$ is the number of produced $b$-jets in the reaction $e + p/A \to n \cdot j_b +X$, to explore new TeV-scale flavor-changing interactions involving the 3rd generation quarks at the EIC; simply by counting the number of $b$-jets in the final state. In particular, the SM single and di-jet production at the EIC which occur through charge current interactions, $e + p/A \to j + \!\not\!E_T$ and $e + p/A \to 2\cdot j + \!\not\!E_T$, are $b_P$-even since the $b_P$-violating (i.e, $b_P=-1$) SM signals for these processes are necessarily CKM suppressed and, therefore, have a vanishingly small production rate. In contrast, new flavor physics can generate $b_P=-1$ signals at the EIC whose only significant SM background is due to $b$-jet misidentification. We thus show that $b_P$ can be used as a simple and sensitive probe of new flavor violating physics; specifically, we find that counting single $b$-jet events in $e + p/A \to j + \!\not\!E_T$ at the EIC with a center-of-mass (CM) energy of $\sqrt{s} \sim 140$ GeV, can probe scales of new physics up to $Λ\sim {\cal O}(5)$ TeV for a certain type of new chiral flavor-changing physics in 3rd generation interactions. This is remarkably more than 30 times larger than the assumed EIC CM energy and it critically depends on the $b$-tagging efficiency and purity as well as the feasibility of electron-beam polarization. The sensitivity of the di-jet process, $e + p/A \to 2j + \!\not\!E_T$, to these type of new physics is reduced compared to the single-jet channel.

2601.03345Jan 2026

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Cavity Multimodes as an Array for High-Frequency Gravitational Waves

Microwave cavities operated in the presence of a background magnetic field provide a promising avenue for detecting high-frequency gravitational waves (HFGWs). We demonstrate for the first time that the distinct antenna patterns of multiple electromagnetic modes within a single cavity enable localization and reconstruction of key properties of an incoming HFGW signal, including its polarization ratio and frequency drift rate. Using a 9-cell cavity commonly employed in particle accelerators as a representative example, we analyze the time-domain response of 18 nearly degenerate modes, which can be sequentially excited by a frequency-drifting signal. The sensitivity is further enhanced by the number of available modes, in close analogy to the scaling achieved by a network of independent detectors, enabling sensitivity to astrophysically plausible binary sources.

2601.03341Jan 2026

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Standard Model Higgs Peaks: a Note on the Vacuum Instability during Inflation

In the Standard Model, the Higgs potential develops an instability at high field values when the quartic self-coupling runs negative. Large quantum fluctuations during cosmic inflation could drive the Higgs field beyond the potential barrier, creating regions that would be catastrophic for our observable universe. We point out that the extreme-value statistics describing the peaks (maxima) of the Higgs values is the correct statistics to infer the condition to avoid vacuum instability. Even if this statistics delivers a bound on the Hubble rate during inflation which is only a factor $\sqrt{2}$ stronger than the one commonly adopted in the literature, it is qualitatively distinct and we believe worthwhile communicating it.

2601.03231Jan 2026

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Study of sub-GeV Dipolar Dark States at SND@LHC within Invisible Bounds on Meson Decays

Electromagnetic form factors constitute a natural portal for accessing states beyond the Standard Model. In particular, dimension-5 magnetic and electric dipole moment operators offer a minimal and predictive framework for Feebly Interacting Particles (FIPs). In this work, we perform a study of the sensitivity reach of the Scattering and Neutrino Detector (SND@LHC) in the detection of dipolar dark states through photon-mediated interactions with the Standard Model particles. The far-forward region of the LHC provides FIPs with large momenta that scatter off electrons and nuclei inside the target. Production of dark states from meson decays is constrained by invisible decay widths, while the Drell-Yan process offers a production channel in the GeV range. We present sensitivity plots for magnetic and electric dipole moment interactions at SND@LHC and compare them with constraints from direct detection, beam dump, fixed-target, and collider experiments. The validity of the effective theory that describes the dipole model is also studied by considering conservative bounds on the couplings.

2601.03186Jan 2026

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Searches for extra-dimensional excitations in light-by-light scattering

We present a comprehensive phenomenological analysis of the Radion in the Randall-Sundrum model, focusing on its production via light-by-light scattering in ultra-peripheral proton-proton collisions at the LHC. We provide a consistent derivation of the effective couplings to Standard Model fields, clarifying the normalization of the trace anomaly-induced coupling to photons and the role of kinetic mixing with the Higgs boson. We demonstrate that while the pure gravitational coupling is loop-suppressed relative to Axion-Like Particles (ALPs), making the unmixed Radion elusive, the non-minimal mixing with the Higgs sector can induce constructive interference that enhances the signal by orders of magnitude. Using forward proton tagging to select exclusive high-mass events, we reinterpret recent experimental limits on ALPs to derive the first exclusion contours for the Radion in the $(Λ_r, ξ)$ plane, showing that mixing scenarios are beginning to be constrained by current LHC data.

2601.03110Jan 2026

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Anatomy of Roper Resonance

Sixty years ago, the first excited state of a proton/neutron was ``born.'' During this time, we learned a lot about it, specifically - how unique this case is: a single resonance with two pole positions on different Riemann sheets. Let me present a brief history to remind readers how development progressed. Sure, history is sometimes something that never happened, described by those who were never there...

2601.03102Jan 2026

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Sommerfeld Effect and Bound State Formation for Dark Matter Models with Colored Mediators with SE+BSF4DM

In the universal framework of simplified $t$-channel dark matter models, the calculation of the relic abundance can be dominated by mediator annihilation when the dark matter and mediator masses are almost degenerate. We analyze four representative models with scalar and fermionic mediators, confront them with direct detection limits and highlight the differences and common features between them. The mediator annihilations are considerably enhanced by the Sommerfeld effect and bound state formation. Albeit their effect is subdominant in the coannihilation regime, excited bound state levels are included as well. We find that Sommerfeld and bound-state effects can lead to order one corrections to the constraints on the DM mass in the coannihilating regime, with the precise magnitude depending on the specific model realization. In addition we provide SE+BSF4DM, an intuitive and easy to use add-on to micrOMEGAs, allowing for an automated inclusion of these effects for a generic $t$-channel Dark Matter Model, which is publicly available on Github.

2601.03026Jan 2026

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