arXiv subjects

J. A. Miranda

Publications and source records attributed to J. A. Miranda.

4 recordsLinked to original sources

arXiv2021

Isospin-breaking corrections to $τ^- \to π^- π^0 ν_τ$ decays and the muon $g-2$

We review the isospin-breaking and electromagnetic corrections to the $τ^- \to π^- π^0 ν_τ$ decays, which are used as an input to the two-pion contributions to the hadronic vacuum polarization (at LO) of the anomalous magnetic moment ($a_μ$). We extend previous analyses by Cirigliano et al. working with ChPT with resonances. As an outcome, we improve the agreement between this determination and the other based on $e^+e^-$ data. The new results are in better agreement with an old estimation that uses Vector Dominance Model (VMD), and the discrepancy between the SM prediction and the combined results from BNL and FNAL is reduced to $2.1\,σ$ at $\mathcal{O}(p^4)$ and $2.3σ$ at $\mathcal{O}(p^6)$.

hep-ph↗

arXiv2020

New $τ$-based evaluation of the hadronic contribution to the vacuum polarization piece of the muon anomalous magnetic moment

We revisit the isospin-breaking and electromagnetic corrections to the decay $τ^-\toπ^-π^0ν_τ$, which allow its use as input in the two-pion contribution to the (leading order) hadronic vacuum polarization part of the muon anomalous magnetic moment. We extend a previous resonance chiral Lagrangian analysis, which included those operators saturating the next-to-leading order chiral low energy constants, by including the contributions of the next subleading terms. As a result, we improve agreement between the two-pion tau decay and $e^+e^-$ data and reduce the discrepancy between experiment and the SM prediction of $a_μ$ (using $τ$ input).

hep-ph↗

arXiv2018

Effective-field theory analysis of the $τ^-\to π^-π^0ν_τ$ decays

We perform an effective field theory analysis of the $τ^- \to π^- π^0 ν_τ$ decays, that includes the most general interactions between Standard Model fields up to dimension six, assuming left-handed neutrinos. We constrain as much as possible the necessary Standard Model hadronic input using chiral symmetry, dispersion relations, data and asymptotic QCD properties. As a result, we set precise (competitive with low-energy and LHC measurements) bounds on (non-standard) charged current tensor interactions, finding a very small preference for their presence, according to Belle data. Belle-II near future measurements can thus be very useful in either confirming or further restricting new physics tensor current contributions to these decays. For this, the spectrum in the di-pion invariant mass turns out to be particularly promising. Distributions in the angle defined by the $τ^-$ and $π^-$ momenta can also be helpful if measured with less than $10\%$ accuracy, both for non-standard scalar and tensor interactions.

hep-ph↗

arXiv1999

Parallel flow in Hele-Shaw cells with ferrofluids

Parallel flow in a Hele-Shaw cell occurs when two immiscible liquids flow with relative velocity parallel to the interface between them. The interface is unstable due to a Kelvin-Helmholtz type of instability in which fluid flow couples with inertial effects to cause an initial small perturbation to grow. Large amplitude disturbances form stable solitons. We consider the effects of applied magnetic fields when one of the two fluids is a ferrofluid. The dispersion relation governing mode growth is modified so that the magnetic field can destabilize the interface even in the absence of inertial effects. However, the magnetic field does not affect the speed of wave propagation for a given wavenumber. We note that the magnetic field creates an effective interaction between the solitons.

cond-mat.soft↗