|
|
Bauer, M., Perez-Soler, J., & Shergold, J. D. (2024). Generalised hydrogen interactions with CINCO: a window to new physics. J. High Energy Phys., 10(10), 176–26pp.
Abstract: We present semi-analytic solutions for atomic transition rates in hydrogenic atoms induced by scalar, pseudoscalar, vector, axial-vector, and tensor interactions. Our results agree with quantum electrodynamics predictions to similar to 0.005 % precision, and further allow us to calculate absorption and emission rates for axions, hidden photons, light scalars or other dark matter candidates for hydrogen and hydrogenic ions. These results can be used to inform searches for light new physics as well as in calculations relevant to searches for fifth forces or varying fundamental constants, with applications from astrophysics to laboratory spectroscopy experiments. We also provide a dedicated tool for the construction of hydrogenic transition amplitudes: “Computation of hydrogen radial INtegrals and COefficients” (CINCO).
|
|
|
|
Beltran, R., Cottin, G., Hirsch, M., Titov, A., & Wang, Z. S. (2023). Reinterpretation of searches for long-lived particles from meson decays. J. High Energy Phys., 05(5), 031–31pp.
Abstract: Many models beyond the Standard Model predict light and feebly interacting particles that are often long-lived. These long-lived particles (LLPs) in many cases can be produced from meson decays. In this work, we propose a simple and quick reinterpretation method for models predicting LLPs produced from meson decays. With the method, we are not required to run Monte-Carlo simulation, implement detector geometries and efficiencies, or apply experimental cuts in an event analysis, as typically done in recasting and reinterpretation works. The main ingredients our method requires are only the theoretical input, allowing for computation of the production and decay rates of the LLPs. There are two conditions for the method to work: firstly, the LLPs in the models considered should be produced from a set of mesons with similar mass and lifetime (or the same meson) and second, the LLPs should, in general, have a lab-frame decay length much larger than the distance between the interaction point and the detector. As an example, we use this method to reinterpret exclusion bounds on heavy neutral leptons (HNLs) in the minimal “3+1” scenario, into those for HNLs in the general effective-field-theory framework as well as for axion-like particles. We are able to reproduce existing results, and obtain new bounds via reinterpretation of past experimental results, in particular, from CHARM and Belle.
|
|
|
|
Beltran, R., Hati, C., Hirsch, M., & Martin-Galan, A. (2026). Long-lived HNLs via ALP portal at the LHC. J. High Energy Phys., 03(3), 233–23pp.
Abstract: Heavy neutral leptons (HNLs) and axion-like particles (ALPs) are both considered well-motivated candidates for beyond the standard model (BSM) physics. If ALPs with sizable couplings to gluons exist, they will be abundantly produced at the LHC. Therefore, HNLs produced via the ALP portal may provide unprecedented sensitivities to HNL parameters. Here, we study the prospects for the high-luminosity LHC to search for long-lived HNLs. We consider future far detectors as well as ATLAS in our simulations. In the limit where the ALP mass is above the TeV scale, HNLs are effectively produced by a dimension-8 operator connecting HNL pairs to gluons. For completeness, we therefore also calculate future LHC sensitivities for HNLs produced via NRSMEFT operators with gluons.
|
|
|
|
Butterworth, J., Cullingworth, M., Egan, J., Esser, F., Sanz, V., & Ubiali, M. (2026). Probing the coupling of axions to tops and gluons with LHC measurements. J. High Energy Phys., 02(2), 073–28pp.
Abstract: We study axion-like particles (ALPs) whose dominant interactions are with gluons and third-generation quarks, and whose couplings to light Standard Model (SM) particles arise at one loop. These loop-induced effects lead to ALP decays and production channels that can be probed at the LHC, even when tree-level couplings are absent. Using an effective field theory (EFT) description that includes momentum-dependent corrections from radiative effects, we reinterpret a wide range of LHC measurements via the CONTUR framework to derive model-independent constraints on the ALP parameter space. We show that LHC data place meaningful bounds in the plane of effective couplings c(t)(0)/f(a) and c(G)(0)/f(a), and that these limits are sensitive to the UV origin of the ALP-top and ALP-gluon couplings. We discuss representative scenarios where either c(t )(0)or c(G)(0) vanishes at the matching scale, and highlight the role of EFT running and mixing in generating observable signals. We also assess the domain of validity of the EFT approach by comparing the typical momentum transfer root s in sensitive regions to the underlying scale f(a). Our results demonstrate the power of loop-aware EFT reinterpretation of SM measurements in probing otherwise elusive ALP scenarios. The framework presented here can be readily extended to include couplings to other fermions and to accommodate ALP decay or long-lived signatures.
|
|
|
|
Cepeda, M., No, J. M., Ramos, C., Sanda Seoane, R. M., & Zurita, J. (2025). Exotic h → Za Higgs decays into τ leptons. J. High Energy Phys., 07(7), 009–25pp.
Abstract: Exotic Higgs decays are among the most promising areas to be explored at the High-Luminosity LHC, given the unprecedentedly large amount (similar to 3 x 10(8)) of 125 GeV Higgs bosons that will be produced. In this context, we propose a new search channel for which the Higgs boson decays to a (leptonically decaying) Z boson and a light BSM pseudoscalar a, which subsequently decays to a pair of tau-leptons (h -> Za -> ll tau tau). After performing a validation of existing ATLAS and CMS exotic Higgs decay searches in related channels, we analyze the HL-LHC projected sensitivity of our a -> tau tau search, targeting the kinematic region where the exotic Higgs decay is two-body. We are able to probe pseudoscalar masses m(a) is an element of [5, 33] GeV by leveraging both leptonic and hadronic tau decays, and establish model-independent 95% C.L. sensitivity projections on the branching fraction BR(h -> Za) x BR(a -> tau tau). These a -> tau tau projections yield a competitive probe of light pseudoscalars, which depending on the model can become significantly more sensitive than projections from existing experimental searches in a -> μμand a -> gamma gamma final states. Finally, we explore the potential of our search to probe an Axion-Like-Particle (ALP) solution to the muon (g – 2) anomaly (when taken face-value), finding that our proposed h -> Za, a -> tau tau search can provide valuable constraints on such ALP scenario, in complementarity with existing h -> Za, a -> gamma gamma experimental searches.
|
|
