Daniele S. M. Alves’s research while affiliated with Los Alamos National Laboratory and other places

A bstract It has been long-understood that final state rescattering effects provide $\mathcal{O}$ O (1) corrections to hadronic meson decays rates, such as η → πππ and η ′ → ηππ . Hence, one would expect that such effects would be just as important in axio-hadronic η and η ′ decays, such as η ⁽ ′ ⁾ → ππa , where a is an axion or axion-like particle (ALP). And indeed they are, as we show in this paper by using the treatment of dispersion relations to include the effects of strong final state interactions in several axio-hadronic processes, namely, η ⁽ ′ ⁾ → π ⁰ π ⁰ a , η ⁽ ′ ⁾ → π ⁺ π − a , and η ′ → ηπ ⁰ a . We also compute the perturbative, leading order decay rates for multiple ALP emission, such as in η ⁽ ′ ⁾ → π ⁰ aa , η ′ → ηaa and η ⁽ ′ ⁾ → aaa , and briefly discuss the expected corrections from strong interactions and the processes that must be considered for an accurate rate estimation of these multi-ALP decay channels.

A bstract We propose an adaptation of Entanglement Renormalization for quantum field theories that, through the use of discrete wavelet transforms, strongly parallels the tensor network architecture of the Multiscale Entanglement Renormalization Ansatz (a.k.a. MERA). Our approach, called wMERA, has several advantages of over previous attempts to adapt MERA to continuum systems. In particular, (i) wMERA is formulated directly in position space, hence preserving the quasi-locality and sparsity of entanglers; and (ii) it enables a built-in RG flow in the implementation of real-time evolution and in computations of correlation functions, which is key for efficient numerical implementations. As examples, we describe in detail two concrete implementations of our wMERA algorithm for free scalar and fermionic theories in (1+1) spacetime dimensions. Possible avenues for constructing wMERAs for interacting field theories are also discussed.

Ta180m is a rare nuclear isomer whose decay has never been observed. Its remarkably long lifetime surpasses the half-lives of all other known β and electron capture decays due to the large K-spin differences and small energy differences between the isomeric and lower-energy states. Detecting its decay presents a significant experimental challenge but could shed light on neutrino-induced nucleosynthesis mechanisms, the nature of dark matter, and K-spin violation. For this study, we repurposed the Majorana Demonstrator, an experimental search for the neutrinoless double-beta decay of Ge76 using an array of high-purity germanium detectors, to search for the decay of Ta180m. More than 17 kg, the largest amount of tantalum metal ever used for such a search, was installed within the ultralow-background detector array. In this Letter, we present results from the first year of Ta data taking and provide an updated limit for the Ta180m half-life on the different decay channels. With new limits up to 1.5×1019 yr, we improved existing limits by 1–2 orders of magnitude which are the most sensitive searches for a single β and electron capture decay ever achieved. Over all channels, the decay can be excluded for T1/2<0.29×1018 yr.

We describe a first measurement of the radiation from a Hf178m sample to search for dark matter. The γ flux from this sample, possessed by Los Alamos National Laboratory nuclear chemistry, was measured with a Ge detector at a distance of 1.2 m due to its high activity. We search for γ’s that cannot arise from the radioactive decay of Hf178m but might arise from the production of a nuclear state due to the inelastic scattering with dark matter. The limits obtained on this γ flux are then translated into constraints on the parameter space of inelastic dark matter. Finally, we describe the potential reach of future studies with Hf178m.

We describe a first measurement of the radiation from a $^{\bf 178m}$Hf sample to search for dark matter. The $\gamma$ flux from this sample, possessed by Los Alamos National Laboratory nuclear chemistry, was measured with a Ge detector at a distance of 4 ft due to its high activity. We search for $\gamma$s that cannot arise from the radioactive decay of $^{\bf 178m}$Hf, but might arise from the production of a nuclear state due to the inelastic scattering with dark matter. The limits obtained on this $\gamma$ flux are then translated into constraints on the parameter space of inelastic dark matter. Finally, we describe the potential reach of future studies with $^{\bf 178m}$Hf.

{180m}$Ta is a rare nuclear isomer whose decay has never been observed. Its remarkably long lifetime surpasses the half-lives of all other known$\beta$and electron capture decays due to the large K-spin differences and small energy differences between the isomeric and lower energy states. Detecting its decay presents a significant experimental challenge but could shed light on neutrino-induced nucleosynthesis mechanisms, the nature of dark matter and K-spin violation. For this study, we repurposed the MAJORANA DEMONSTRATOR, an experimental search for the neutrinoless double-beta decay of$^{76}$Ge using an array of high-purity germanium detectors, to search for the decay of$^{180m}$Ta. More than 17 kilograms, the largest amount of tantalum metal ever used for such a search was installed within the ultra-low background detector array. In this paper we present results from the first year of Ta data taking and provide an updated limit for the$^{180m}$Ta half-life on the different decay channels. With new limits up to 1.5 x$10^{19}$years, we improved existing limits by one to two orders of magnitude. This result is the most sensitive search for a single$\beta$ and electron capture decay ever achieved.

We show results from the Coherent CAPTAIN Mills (CCM) 2019 engineering run which begin to constrain regions of parameter space for axionlike particles (ALPs) produced in electromagnetic particle showers in an 800 MeV proton beam dump, and further investigate the sensitivity of ongoing data-taking campaigns for the CCM200 upgraded detector. Based on beam-on background estimates from the engineering run, we make realistic extrapolations for background reduction based on expected shielding improvements, reduced beam width, and analysis-based techniques for background rejection. We obtain reach projections for two classes of signatures; ALPs coupled primarily to photons can be produced in the tungsten target via the Primakoff process, and then produce a gamma-ray signal in the liquid argon CCM detector either via inverse Primakoff scattering or decay to a photon pair. ALPs with significant electron couplings have several additional production mechanisms (Compton scattering, e+e− annihilation, ALP-bremsstrahlung) and detection modes (inverse Compton scattering, external e+e− pair conversion, and decay to e+e−). In some regions, the constraint is marginally better than both astrophysical and terrestrial constraints. With the beginning of a three year run, CCM will be more sensitive to this parameter space by up to an order of magnitude for both ALP-photon and ALP-electron couplings. The CCM experiment will also have sensitivity to well-motivated parameter space of QCD axion models. It is only a recent realization that accelerator-based large volume liquid argon detectors designed for low-energy coherent neutrino and dark matter scattering searches are also ideal for probing ALPs in the unexplored ∼MeV mass scale.

The workshop “Shedding light on X17” brings together scientists looking for the existence of a possible new light particle, often referred to as X17. This hypothetical particle can explain the resonant structure observed at $\sim$ ∼ 17 MeV in the invariant mass of electron-positron pairs, produced after excitation of nuclei such as $^8\hbox {Be}$ 8 Be and $^4\hbox {He}$ 4 He by means of proton beams at the Atomki Laboratory in Debrecen. The purpose of the workshop is to discuss implications of this anomaly, in particular theoretical interpretations as well as present and future experiments aiming at confirming the result and/or at providing experimental evidence for its interpretation.

Rare meson decays are among the most sensitive probes of both heavy and light new physics. Among them, new physics searches using kaons benefit from their small total decay widths and the availability of very large datasets. On the other hand, useful complementary information is provided by hyperon decay measurements. We summarize the relevant phenomenological models and the status of the searches in a comprehensive list of kaon and hyperon decay channels. We identify new search strategies for under-explored signatures, and demonstrate that the improved sensitivities from current and next-generation experiments could lead to a qualitative leap in the exploration of light dark sectors.