arXiv subjects

Luca H. Abu El-Haj

Publications and source records attributed to Luca H. Abu El-Haj.

3 recordsLinked to original sources

arXiv2026

Probing inflationary particle production with the CMB power spectrum

Particle production is common to many microphysical models of inflation and can imprint observable features in the cosmic microwave background (CMB) anisotropies. We consider a scenario in which the inflaton couples to an extremely massive field ($m_χ\gtrsim \mathcal{O}(100 H_I)$, where $H_I$ is the inflationary Hubble scale). In this model, particle production happens in a burst at a characteristic conformal time, $η_*$, which sources localized features in the CMB. In this paper, we compute the full temperature and polarization two-point functions for this model. We then search for these features in CMB power spectrum data from Planck and the Atacama Cosmology Telescope (ACT), with the latter allowing access to features on smaller angular scales. In the joint analysis of Planck and ACT data, we find a mild $\sim 2 σ$ hint for a signal induced by this inflationary model on scales $3 \,\, \text{Mpc}\leqη_*\leq 10 \,\, \text{Mpc}$, though this hint is not present at a statistically significant level in either dataset when analyzed individually. Using a Fisher forecast, we find that these features should be observable at the $3-5σ$ level for a Simons Observatory-like experiment, if they are indeed real. We also compare our power-spectrum-based constraints to previous matched-filter-based bounds on this model. For sufficiently light particles ($m_χ\lesssim 200 H_I$), the power spectrum yields tighter constraints by more than an order of magnitude, but in the higher-mass regime where particle production is rare, the matched-filter approach provides stronger bounds.

astro-ph.CO↗

arXiv2026

Continuum contribution to charged-current absorption of low-energy $ν_e$ on $^{40}$Ar

Accurate modeling of the absorption of tens-of-MeV $ν_e$ on $^{40}$Ar is needed to enable measurements of astrophysical neutrinos using large liquid argon time projection chamber (LArTPC) detectors, such as those planned for the Deep Underground Neutrino Experiment (DUNE). We revisit the MARLEY neutrino interaction model used in present estimates of DUNE sensitivity to supernova and solar neutrino signals. Multiple theoretical refinements are pursued, especially in the unbound continuum region of nuclear excitation energy. Inclusive charged-current neutrino-argon cross sections are calculated using a hybrid strategy. Nuclear transitions to unbound states are treated using a Hartree-Fock Continuum Random Phase Approximation (HF-CRPA) model, including forbidden contributions. Allowed transitions to low-lying discrete levels are also included using indirect measurements and approximate corrections for the momentum transfer dependence. Exclusive predictions are obtained by coupling these calculations with a statistical nuclear de-excitation model. The impact on observables of interest for DUNE and similar experiments is examined in terms of both total and differential cross sections. Our refined calculations predict a lower allowed portion of the cross section relative to the prior MARLEY model. At neutrino energies appreciably below 100 MeV, the inclusion of forbidden transitions does not fully compensate for the loss of allowed strength. For a representative neutrino burst from a galactic core-collapse supernova, our results suggest that MARLEY 1.2.0 overestimates the event yield in a DUNE-like detector by approximately 20%. However, because this overestimation is more severe at backwards angles, use of the charged-current $ν_e$-$^{40}$Ar reaction for supernova pointing may be more feasible than previously expected.

hep-ph↗

arXiv2026

Constraining Inflationary Particle Production with CMB Polarization

Following Philcox et al. (2025), we investigate a scenario with a massive partner to the inflaton ($O(100)$ times the inflationary Hubble scale), in which particles are produced during a narrow time period, leaving characteristic hot- or cold-spots in the cosmic microwave background (CMB). Using tools developed for thermal Sunyaev-Zel'dovich cluster-finding, we search component-separated Planck PR4 $E$-mode maps for these hotspots, and compare to analogous results in $T$. Our analysis pipeline is validated on simulated observations and gives unbiased constraints for sufficiently large and bright hotspots. At Planck sensitivities, the temperature data are more sensitive to small hotspots, but for sufficiently large hotspots the polarization data are more sensitive. We improve upon earlier work by building a full Poissonian likelihood for the hotspot abundance. We find no strong evidence for primordial hotspots and thereby place novel bounds on the couplings between the inflaton and massive scalars during inflation, probing physics at energies many orders of magnitude above any feasible terrestrial collider. The bounds derived from our new likelihood improve upon those of Philcox et al. (2025) by more than an order of magnitude for sufficiently light particles ($M_0\lesssim100H_I$). We also forecast the inferred bounds on inflationary physics for a search using Atacama Cosmology Telescope (ACT) data, and from an optimistic cosmic-variance-limited experiment (CV), for which $E$-mode data provide stronger constraints than $T$ on nearly all scales. ACT should improve on the Planck constraints by $\gtrsim10\%$, nearing the CV limit allowed by its sky coverage. Finally, we compare the constraining power of localized searches to that of a power spectrum analysis, and demonstrate that for sufficiently few produced particles the localized search performed herein is dominant.

astro-ph.CO↗