arXiv subjects

Carlos Henrique de Lima

Publications and source records attributed to Carlos Henrique de Lima.

At least 19 recordsLinked to original sources

arXiv2026

Exothermic Dark Matter at LZ

We investigate whether the high-energy nuclear recoil reported by the LUX-ZEPLIN (LZ) experiment can be explained by exothermic dark matter. We realize this framework in a minimal inelastic dark photon model and show that both freeze-out and low-reheating-temperature freeze-in cosmologies can reproduce the observed rate, with GeV-scale mediator masses and small kinetic mixing. We find that the LZ event can occur in a preferred parameter region with dark matter mass around $m_χ\sim 30-200~\mathrm{GeV}$, and mass splitting $δ\sim 0.5-1~\mathrm{MeV}$. The scenario is largely insensitive to halo uncertainties and has robust predictions for different targets. In particular, argon and germanium detectors are expected to observe events at energies above the current xenon window.

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arXiv2026

On the Origins of Varying Gauge Couplings

Variations in the gauge couplings of the Standard Model have been searched for experimentally and proposed as solutions to open questions in fundamental physics. Varying gauge couplings can arise from a dynamical scalar field coupled to the gauge kinetic term. This mechanism has been invoked extensively, assuming a minimal linear coupling of the scalar to the gauge bosons. In this work, we investigate how this operator is generated from the ultraviolet perspective. We argue that in weakly coupled, renormalizable completions in four spacetime dimensions, gauge invariance forces the leading dependence of the effective gauge coupling on the scalar to be logarithmic rather than linear. The gauge coupling evolution in these scenarios can be entirely described by the renormalization-group running with dynamical mass thresholds. Beyond leading order or four dimensions, we provide examples showing that more general behavior is possible. Finally, we discuss the phenomenological implications of dynamically evolving gauge couplings, particularly in early-universe settings.

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arXiv2026

Neutrino Electroweak Couplings and the Neutrino Fog at Belle II

The mono-photon process $e^+e^- \to γ+\mathrm{invisible}$ at Belle II probes both invisible new states and the electroweak couplings of neutrinos. In this work, we study the process $e^+e^- \to γν\barν$, finding that Belle II with the full expected dataset can determine the neutrino-sensitive effective weak mixing angle to a 3.6$\%$ relative statistical precision, competitive with existing neutrino probes at other energy scales. Polarized beams, as proposed for the Chiral Belle upgrade, separate the neutral- and charged-current contributions and provide independent access to each, giving a handle on the chiral structure of the neutrino gauge interactions. The same process is an irreducible background to dark boson searches, producing a neutrino fog once the luminosity exceeds 1 ab$^{-1}$.

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arXiv2026

High Energy Photon Polarimetry at Lepton Colliders: Quantum Information from Converted Photons

We study high-energy photons produced at a lepton collider that convert into an $e^+e^-$ pair in the detector, as a tool for measuring quantum information observables. We consider single- and double-conversion processes in $e^+e^- \to γγ$ and $e^+e^- \to e^+e^-γ$. Single conversions enable an in situ extraction of the spin-analyzing power, while double conversions probe polarization correlations. Focusing on the Belle-II detector, we show that, depending on the reconstruction resolution of the opening angle of the conversion $e^+e^-$ pair, quantum correlations of the diphoton system can be probed. In particular, measurements of violations of the Bell inequality, quantum discord, concurrence, nonstabilizerness, and steerability with spatially separated GeV-scale photons can be made at high significance.

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arXiv2026

Low-Multiplicity Jets as Probes of GeV-Scale Light-Quark-Coupled Particles

We propose a search at the LHC for GeV-scale particles coupling predominantly to light quarks based on low-multiplicity jets. The search targets production in association with a hard photon and uses the feature that a light gauge-singlet can only decay into a small number of hadronic channels, yielding jets with anomalously low charged-track multiplicity and mass compared to QCD jets at the same transverse momentum. We determine the sensitivity to scalar and pseudoscalar couplings to up-quarks, and suggest a data-driven estimate that reduces the sensitivity to jet modeling uncertainties. This search extends the reach to hadronically-coupled particles into a previously inaccessible regime.

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arXiv2026

Boosting VBF Reconstruction at Muon Colliders

Forward muon detection at high-energy muon colliders is crucial for resolving the underlying electroweak process. Detecting these muons is challenging in current detector designs, limited by the shielding required to suppress the beam-induced background. This work proposes using asymmetric beam energies to boost one of the forward muons into the detector acceptance, enhancing the ability to distinguish between $W$- and $Z$-initiated vector boson fusion processes. We demonstrate the capabilities of such an asymmetric collider using VBF Higgs production at 3 and 10 TeV muon colliders with modest boost asymmetries. Asymmetric beam configurations can partially recover the physics potential lost in forward regions when detector coverage is limited.

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arXiv2026

Characterizing Dark Bosons at Chiral Belle

We explore the advantages of a polarized electron beam at Belle II, as proposed for ``Chiral Belle'', in the search for invisibly decaying (dark) bosons that weakly couple to the Standard Model. By measuring the polarization dependence of the production cross section of dark bosons in association with a photon, the dark boson's spin and Lorentz structure of its couplings can potentially be determined. We analyze the mono-photon channel, $e^+ e^- \rightarrow γ+ \text{invisible}$, in detail, focusing on the production of an on-shell spin-1 boson. We explore this in the context of three separate scenarios for a new dark vector: a dark photon, a mass-mixed ``dark $Z$'', and a vector that couples to right-handed electrons, and estimate how well the couplings of such bosons to electrons can be constrained in the event of a positive signal.

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arXiv2026

Hadronic Probes of Non-Standard Neutrino Interactions

In this work, we study leptonic decays of hadrons as probes of light neutrinophilic scalars that mediate enhanced neutrino self-interactions. Such scalars can be emitted in processes involving neutrinos, turning two-body decays into three-body final states and producing characteristic spectral distortions. We compute these effects for charged pion decay and nuclear electron capture decay, including both on-shell and off-shell scalar emission, as well as the loop-induced renormalization required to cancel divergences. Using these results, we derive the projected sensitivity of PIONEER and assess the current and future reach of BeEST. The resulting low-energy spectral tails provide a characteristic signal for light neutrinophilic scalars, making upcoming hadron decay experiments powerful probes of light mediators of non-standard neutrino self-interactions.

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arXiv2025

Novel Phases of a Baryon-Dense QCD-like Theory

We investigate the phases of a strongly coupled QCD-like theory at finite baryon chemical potential using s-confining supersymmetric QCD deformed by anomaly-mediated supersymmetry breaking. Focusing on the case of three colors and four flavors, we identify novel phases including spontaneous breaking of baryon number and/or parity. Both first-order and second-order phase transitions are observed as the baryon chemical potential is varied. These findings may offer insights into possible phases of real QCD at intermediate baryon densities.

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arXiv2025

The Sign of Gauge-Higgs Couplings at Future Lepton Colliders

This work investigates the capability of future lepton colliders to determine the sign of the gauge-Higgs coupling through the vector boson fusion (VBF) $Zh$ process. This channel offers a model-independent way to probe the sign of the gauge-Higgs coupling. Its sensitivity to interference effects and universal coupling with new physics makes it particularly effective. We show that a high-energy lepton collider such as CLIC can fully determine the sign of the gauge-Higgs coupling in a model-independent way and with high confidence.

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arXiv2024

Probing Lepton Number Violation at Same-Sign Lepton Colliders

Same-sign lepton colliders offer a promising environment to probe lepton number violation. We study processes that change lepton number by two units in the context of Majorana heavy neutral leptons and neutrinophilic scalars at $μ$TRISTAN, a proposed same-sign muon collider. Our work shows that such colliders, with modest energy and luminosity requirements, can either reveal direct evidence of lepton number violation or significantly constrain unexplored regions of parameter space, especially in the case of a neutrinophilic scalar.

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arXiv2024

Influence of new states in searches for negative gauge-Higgs couplings

In this work, we explore how constraints based on interference effects for the negative gauge-Higgs coupling scenario are affected by new physics. Models that achieve this wrong-sign gauge-Higgs coupling inevitably have new charged Higgs states. These states affect the interpretation of interference effects. We recast the ATLAS analysis for VBF $Wh$, showing that the previously excluded negative gauge-Higgs coupling scenario is still experimentally viable for charged Higgs masses below $370$~GeV. We show that it is possible to weaken this bound further with mild tuning in the parameter space. We discuss how to further constrain the wrong-sign gauge-Higgs coupling hypothesis and point out the potential of VBF $Zh$ to exclude this scenario in a model-independent way.

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arXiv2024

Is the real two-Higgs-doublet model consistent?

We provide strong evidence that the widely-studied real two-Higgs-doublet model is inconsistent under renormalization due to quark-induced divergent CP violation (CPV). We identify the necessary ingredients for the CPV to enter the renormalization-group equations based on symmetry proprieties of the divergent diagrams. We demonstrate that while these ingredients are present starting at six loops, the divergent CPV is zero at that order due to approximate symmetries. We show that these symmetries are broken at seven loops and determine the parameter dependence of the resulting divergent CPV.

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arXiv2024

On s-confining SUSY-QCD with Anomaly Mediation

In this work, we present a comprehensive study of the phase diagram of supersymmetric QCD with $N_{f}=N_{c}+1$ flavors perturbed by Anomaly Mediated Supersymmetry Breaking (AMSB). We extend the previous analyses on s-confining ASQCD theories in three different directions. We show that the existence of the QCD-like vacuum is independent of the size of the SUSY breaking parameter. We further expand the analysis of these models by including two and three-loop contributions to investigate the robustness and limitations of the results. Finally, we include the leading effect of higher-order Kähler terms to investigate the stability of the phase diagram as we approach the confining energy scale. The analysis with higher order Kähler terms is also extended for $N_{c}=2$ for which AMSB alone gives inconclusive results.

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arXiv2024

Status of negative coupling modifiers for extended Higgs sectors

In this work, we study the status of negative coupling modifiers in extended Higgs sectors, focusing on the ratio of coupling modifiers that probes custodial symmetry violation $λ_{WZ} = κ_{W}/κ_{Z}$. Higgs sectors with multiplets larger than doublets are the only weakly coupled models that give tree-level modifications to $λ_{WZ}$, and we explore all such models allowed by the constraint from the $ρ$ parameter and perturbative unitarity. This class of models has a custodial symmetry violating potential, while the vacuum configuration preserves the symmetry. We apply precision measurements from ATLAS and CMS and show that each data set can exclude a vast set of models with $λ_{WZ} < 0$ at greater than 95\% confidence level. We give evidence that $λ_{WZ}<0$ is excluded in all weakly coupled models. [Erratum for this work on page 19 changing our claims of complete exclusion of negative $λ_{WZ}$ to a softer version where only the minimal models are excluded.]

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arXiv2024

Electrobaryonic axion: hair of neutron stars

Axion-like particles are predicted in many physics scenarios beyond the Standard Model (SM). Their interactions with SM particles may arise from the triangle anomaly of the associated global symmetry, along with other SM global and gauge symmetries, including anomalies with the global baryon number and electromagnetic gauge symmetries. We initiate the phenomenological study of the corresponding ``electrobaryonic axion", a particle that couples with both the baryon chemical potential and the electromagnetic field. Neutron stars, particularly magnetars, possessing high baryon density and strong magnetic fields, can naturally develop a thin axion hair around their surface. In this study, we calculate this phenomenon, considering the effects of neutron star rotation and general relativity. For axion particles lighter than the neutron star rotation frequency, the anomalous interaction can also induce the emission of axion particles from the neutron star. This emission, in the light axion regime, can have a significant contribution to the neutron star cooling rate.

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arXiv2024

Can CP be conserved in the two-Higgs-doublet model?

We study the conditions under which the CP violation in the quark mixing matrix can leak into the scalar potential of the real two-Higgs-doublet model (2HDM) via divergent radiative corrections, thereby spoiling the renormalizability of the model. We show that any contributing diagram must involve 12 Yukawa-coupling insertions and a factor of the $U(1)_{PQ}$-breaking scalar potential parameter $λ_5$, thereby requiring at least six loops; this also implies that the 2HDM with only softly-broken $U(1)_{PQ}$ is safe from divergent leaks of CP violation to all orders. We demonstrate that additional symmetries of the six-loop diagrams in the type I and II 2HDMs guarantee that all of the divergent CP-violating contributions cancel at this order. We also show that these symmetries are violated at seven loops and enumerate the classes of diagrams that can contribute to CP-violating divergences, providing evidence that the real 2HDM is theoretically inconsistent starting at the seven-loop level.

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arXiv2023

P-wave Sommerfeld enhancement near threshold: a simplified approach

The calculation of P-wave Sommerfeld enhancement in processes with unstable particles in the final state is known to be divergent. In a complete description, where resonant (on-shell unstable particles) and non-resonant contributions are included, it has been shown that results are finite. For most beyond the Standard Model applications, these complete calculations are not readily available. In this work, we are interested in the near-threshold region and we consider only the resonant contribution. In this case, we provide a simplified prescription to compute the P-wave Sommerfeld enhancement in the narrow-width approximation of the unstable particle that directly eliminates divergences. We show that we can define a finite resonant contribution without the inclusion of the non-resonant processes in a way similar to the usual S-wave Sommerfeld enhancement.

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