English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

We investigate the vector and scalar form factors relevant for K_{\ell 3}semileptonic decays using maximally twisted-mass fermions with two flavors ofdynamical quarks (N_f = 2). The simulations cover pion masses as light as 260MeV and four values of the lattice spacing, ranging from ~0.05 up to ~0.1 fm,which allow to compute directly, for the first time, the continuum limit forthe vector form factor at zero-momentum transfer, f_+(0). The preliminaryresult is f_+(0) = 0.9544(68), where the error is statistical only. We alsoextrapolate both form factors to the physical point and study their momentumdependence. Our results are in good agreement with those obtained from adispersion analyses of the experimental data. Together with the form factors,we analyze the ratio of the leptonic decay constants f_K / f_\pi, by imposingthe constraint coming from the Callan-Treiman theorem, obtaining at thephysical point f_K / f_\pi = 1.190(8). Combining our results for f_+(0) and f_K/ f_\pi with the experimental measurements of the leptonic and semilpetonicdecay rates, and using the determination of |V_{ud}| from nuclear beta decays,we determine the values of the Cabibbo angle |V_{us}| from both K_{\ell 3} andK_{\ell 2} decays, obtaining |V_{us}|^{K_{\ell 3}} = 0.2266(17) and$|V_{us}|^{K_{\ell 2}} = 0.2258(16).

Improved analysis of the scalar and vector form factors of kaon semileptonic decays with N_f = 2 twisted-mass fermions