arXiv subjects

Lucas Platter

Publications and source records attributed to Lucas Platter.

At least 19 recordsLinked to original sources

arXiv2026

Muon Capture on the Proton with Heavy-Light Currents

We construct a non-relativistic Lagrangian that describes muon-proton electroweak interactions. We determine the leading order coefficients by matching onto the theory with non-relativistic nucleons and relativistic leptons. The most impactful $\mathcal{O}(\alpha)$ corrections to those coefficients are determined by matching the non-relativistic amplitudes for capture of a free muon on a proton to the corresponding relativistic one. We use our non-relativistic effective field theory framework to calculate the capture rate in muonic hydrogen, thereby including radiative corrections of order $\alpha$ and up to order $1/m_\mu$. Using results for the Fermi coupling previously derived in EFT, we obtain singlet and triplet capture rates of $\Gamma({}^1 S_0) = 724.07 \pm 5.45~\rm{s}^{-1}$ and $\Gamma({}^3 S_1) = 11.55 \pm 0.18~\rm{s}^{-1}$, respectively.

hep-ph↗

arXiv2026

Two-Body Scattering Observables from Finite-Volume Real-Time Evolution

We study two-body scattering observables from real-time evolution in a finite periodic box. The system consists of two distinguishable particles on a two-dimensional lattice interacting through pointlike $s$- and $p$-wave interactions. We evolve their wave packets in real time, define detector observables through angular wedges in the relative coordinate, and attach infinite-volume labels obtained from the bound-state pole equation and the low-energy scattering amplitude. We train a convolutional neural network on this data and test its performance on held-out scattering problems and find that is able to predict the total magnitude and angular shape for previously unseen Hamiltonians.

nucl-th↗

arXiv2026

Taming nuclear size and shape effects in superallowed beta-decay

We present the first combined analysis of the statistical rate function f in superallowed beta decays with ab initio calculations and data. We focus on C10 to 10B, 14O to 14N and 26mAl to 26Mg, all of which are important channels for the precise determination of the Cabibbo-Kobayashi-Maskawa (CKM) matrix element Vud. Nuclear charge form factors are obtained by combining experimental data on nuclear charge radii and theory calculations of ratios of moments with the in-medium similarity renormalization group, while the beta decay form factors are derived from exact isospin relations. This enables a rigorous study of the nuclear shape dependence in the statistical rate function f and the quantification of its uncertainties from both experiment and theory. The calculation leads to a more precise test for the first-row CKM unitarity with reduced theoretical uncertainties. This work demonstrates a reliable strategy for combining nuclear many-body calculations with high-precision nuclear data to describe beta decays at tree level for precision tests of the Standard Model.

nucl-th↗

arXiv2025

Inferring the breakdown scales of the chiral expansions for $g_A$ and $m_N$

We apply Bayesian inference to the order-by-order chiral perturbation theory ($\chi$PT) expansions for the axial-vector coupling constant $g_A$ and the nucleon mass m_N, and thereby infer the scales at which $\chi$PT breaks down for these two observables. Using a pointwise Bayesian analysis, we find that the inferred breakdown scales are notably different for the two observables. For the chiral expansion of $g_A$, we obtain $251^{+20}_{-50}$ MeV and $211^{+20}_{-30}$ MeV using two distinct sets of low-energy constants, while for the chiral expansion of $m_N$ we infer a significantly larger breakdown scale of $491^{+60}_{-90}$ MeV.

hep-ph↗

arXiv2025

Improved nuclear-structure corrections to the hyperfine splitting of electronic and muonic deuterium

We calculate the nuclear-structure correction to the hyperfine splitting in both electronic and muonic deuterium using interactions from chiral effective field theory. We explore the sensitivity to different parameterizations of the nucleon-nucleon force, study the convergence pattern in the order-by-order chiral expansion, and estimate remaining uncertainties. Our results are consistent with earlier calculations from pionless effective field theory, offering new insights for a robust uncertainty quantification. Thanks to the order-of-magnitude reduction in uncertainty achieved with chiral effective field theory, the two-photon exchange contribution in electronic deuterium agrees with experimental extractions within $0.7\sigma$, in contrast to the $2.7\sigma$ discrepancy observed in muonic deuterium. This study lays the groundwork for extending TPE calculations to HFS in heavier atomic systems.

nucl-th↗

arXiv2025

Non-Efimovian two-neutron halos with an $s$-wave core-neutron resonance

We consider two-neutron halo nuclei in which the neutron core subsystem displays a resonance close to threshold. Such resonances can be generated in an effective field theory in which the scattering length and effective range are summed to all orders. We show that no three-body parameter is required to make predictions in this case and map out the universal features of such systems. We furthermore study the dependence of these universal features on the core mass. We apply our framework to the two-neutron halo nucleus ${}^{22}$C.

nucl-th↗

arXiv2025

The breakdown scale of pionless effective field theory in the three-nucleon sector

We make order-by-order predictions of neutron-deuteron total cross sections up to next-to-next-to-leading order in pionless effective field theory. Using Bayesian methods, we infer a posterior distribution for the breakdown scale. The result shows a mode near 100 MeV, and a combined analysis with neutron-proton scattering further sharpens the inference, placing the mode close to the pion mass scale, consistent with the expected range of pionless effective field theory.

nucl-th↗

arXiv2024

Quantifying the breakdown scale of pionless effective field theory

We use Bayesian statistics to infer the breakdown scale of pionless effective field theory in its standard power counting and with renormalization of observables carried out using the power-divergence subtraction scheme and cutoff regularization. We condition our inference on predictions of the total neutron-proton scattering cross section up next-to-next-to leading order. We quantify a median breakdown scale of approximately 1.4$m_\pi$. The 68% degree of belief interval is $[0.96,1.69]m_\pi$. This result confirms the canonical expectation that the pion mass is a relevant scale in low-energy nuclear physics.

nucl-th↗

arXiv2024

Radiative corrections to proton-proton fusion in pionless EFT

We study the leading radiative correction to proton-proton fusion using the pionless effective field theory framework at leading order. We derive the relevant matrix elements and evaluate them using the method of regions. We benchmark the accuracy of our approximations by carrying out numerical computations of the full expressions. We show that the first order radiative corrections due to the exchange of a Coulomb photon between positron and proton-proton systems map onto the Sirlin function and the $\mathcal{O}(\alpha)$ contribution from the Fermi function. We furthermore find that the nuclear structure dependent radiative correction omitted in the previous analysis by Kurylov {\it et al} gives an up to 0.2~\% correction to the pp fusion S-factor with its size ultimately depending on a two-nucleon counterterm that renormalizes the axial two-body current $L_{1A}$.

nucl-th↗

arXiv2023

Nuclear Structure Effects on Hyperfine Splittings in Ordinary and Muonic Deuterium

Precision spectroscopy of hyperfine splitting (HFS) is a crucial tool for investigating the structure of nuclei and testing quantum electrodynamics (QED). However, accurate theoretical predictions are hindered by two-photon exchange (TPE) effects. We propose a novel formalism that accounts for nuclear excitations and recoil in TPE, providing a model-independent description of TPE effects on HFS in light ordinary and muonic atoms. Combining our formalism with pionless effective field theory at next-to-next-to-leading order, the predicted TPE effects on HFS are 41.2(2.6) kHz and 0.116(9) meV for the 1S state in deuterium and the 2S state in muonic deuterium. These results are within 1.4-1.7 standard deviation from recent measurements and highlight the importance of nuclear structure effects on HFS and indicate the value of more precise measurements in future experiments.

nucl-th↗

arXiv2023

Scattering phase shifts from a quantum computer

We calculate two-body scattering phase shifts on a quantum computer using a leading order short-range effective field theory Hamiltonian. The algorithm combines the variational quantum eigensolver and the quantum subspace expansion. As an example, we consider scattering in the deuteron $^3$S$_1$ partial wave. We calculate scattering phase shifts with a quantum simulator and on real hardware. We also study how noise impacts these calculations and discuss noise mitigation required to extend our work to larger quantum processing units. With current hardware, up to five superconducting qubits can produce acceptable results, and larger calculations will require a significant noise reduction.

nucl-th↗

arXiv2023

Revisiting proton-proton fusion in chiral effective field theory

We calculate the $S$-factor for proton-proton fusion using chiral effective field theory interactions and currents. By performing order-by-order calculations with a variety of chiral interactions that are regularized and calibrated in different ways, we assess the uncertainty in the $S$-factor from the truncation of the effective field theory expansion and from the sensitivity of the $S$-factor to the short-distance axial current determined from three- and four-nucleon observables. We find that $S(0)=(4.100\pm0.019\mathrm{(syst)}\pm0.013\mathrm{(stat)}\pm0.008(g_A))\times10^{-23}~\mathrm{MeV\,fm}^2\,,$ where the three uncertainties arise, respectively, from the truncation of the effective field theory expansion, use of the two-nucleon axial current fit to few-nucleon observables and variation of the axial coupling constant within the recommended range. The increased value of $S(0)$ compared to previous calculations is mainly driven by an increase in the recommended value for the axial coupling constant and is in agreement with a recent analysis based on pionless effective field theory.

nucl-th↗

arXiv2022

Muon capture on the deuteron in chiral effective field theory

We consider the capture of a muon on a deuteron. An uncertainty analysis of the dominant channels is important for a careful analysis of forthcoming experimental data. We quantify the theoretical uncertainties of chiral effective-field-theory predictions of the muon-deuteron capture rate from the relevant neutron-neutron partial wave channels in the final state. We study the dependence on the cutoff used to regularize the interactions, low-energy constants calibrated using different fitting data and strategies, and truncation of the effective-field-theory expansion of the currents. Combining these approaches gives as an estimate of $\Gamma^{1/2}_{\mu d} = 399.1 \pm 7.6 \pm 4.4$ s$^{-1}$ for capture from the atomic doublet state, and $\Gamma^{3/2}_{\mu d} = 12.31 \pm 0.47 \pm 0.04$ s$^{-1}$ for capture from the quartet state.

nucl-th↗

arXiv2022

Weak decay of halo nuclei

We investigate the weak decay of one-neutron halo nuclei into the proton-core continuum, i.e., beta-delayed proton emission from the halo nucleus using a cluster effective field theory for halo nuclei. On the one hand, we calculate the direct decay into the continuum. On the other hand, we consider the case of resonant final state interactions between the proton and the core. We present our formalism and discuss the application to the decay of $^{11}$Be in detail. Moreover, we compare to recent experimental results for the branching ratio and resonance parameters. As another example, we consider the case of $^{19}$C and predict the branching ratio for beta-delayed proton emission.

nucl-th↗

arXiv2021

Residual cut-off dependence and power counting: the deuteron as a case study

Effective field theories (EFTs) require regularization and renormalization to gain predictive power. While regularization is inconsequential from the point of view of the observable predictions of EFT -- in a renormalized theory we expect predictions to be regulator-independent once the cutoff is removed -- the particular details of regulator dependence might provide interesting insights into the inner workings of an EFT. In fact, the analysis of regulator dependence has been frequently suggested as a tool to study the ordering scheme or power counting of EFTs. We show here that the choice of the regulator might impact the power law properties of the residual cutoff dependence. If this conclusion were to be confirmed, it would have consequences on the validity of this method as a tool to analyze power counting.

nucl-th↗

arXiv2021

The van der Waals interaction as the starting point for an effective field theory

We consider the system of three ${}^4$He atoms to assess whether a pure van der Waals potential can be used as a starting point for an effective field theory to describe three-body processes in ultracold atomic systems. Using a long-range van der Waals interaction in combination with short-distance two-body counterterms, we analyze the dependence of two- and three-body observables on the short-distance regulator that is required due to the singular nature of the van der Waals interaction. We benchmark our approach with results obtained with the realistic ${}^4$He-${}^4$He LM2M2 interaction and find good agreement. We furthermore show that in this effective field theory approach no three-body force is required at leading order and that universal van der Waals physics leads to a universal correlation between three-body observables in the absence of an Efimov three-body parameter.

cond-mat.quant-gas↗

arXiv2020

Electric dipole moments of three-nucleon systems in the pionless effective field theory

We calculate the electric dipole moments (EDMs) of three-nucleon systems at leading order in pionless effective field theory. The one-body contributions that arise from permanent proton and neutron EDMs and the two-body contributions that arise from CP-odd nucleon-nucleon interactions are taken into account. Neglecting the Coulomb interaction, we consider the triton and ${}^3$He, and also investigate them in the Wigner-SU(4) symmetric limit. We also calculate the electric dipole form factor and find numerically that the momentum dependence of the electric dipole form factor in the Wigner limit is, up to an overall constant (and numerical accuracy), the same as the momentum dependence of the charge form factor.

nucl-th↗

arXiv2020

Pionless Effective Field Theory Evaluation of Nuclear Polarizability in Muonic Deuterium

We calculate the longitudinal structure function of the deuteron up through next-to-next-to-leading order in the framework of pionless effective field theory. We use these results to compute the two-photon polarizability contribution to Lamb shift in muonic deuterium, which can be utilized to extract the nuclear charge radius of the deuteron. We present analytical expressions order-by-order for the relevant transition matrix elements and the longitudinal structure function, and we give numerical results for the corresponding contributions to the Lamb shift. We also discuss the impact of relativistic and other higher-order effects. We find agreement with previous calculations and explain the accuracy of our calculation.

nucl-th↗