New Physics in s→uℓ−νˉs\to u\ell^-\bar\nu: Interplay between semileptonic kaon and hyperon decays

We review a novel model-independent approach to the analysis of new-physics effects in the $s\to u\ell^-\bar\nu$ transitions. We apply it to (semi)leptonic kaon decays and study their complementarity with pion and hyperon $\beta$ decays or with collider searches of new physics.Comment: Contribution to the NA62 Physics Handbook. It summarizes the analysis presented in arXiv:1605.07114 and discusses in more detail the interplay between $K_{\mu3}$ and semileptonic hyperon decays as new-physics probe

Women’s representation in politics : voter bias, party bias, and electoral systems

Estudiamos cómo afecta el sistema electoral a la presencia de mujeres en política usando un modelo en el que tanto los votantes como los partidos pueden tener un sesgo de género. Aplicamos el modelo a las elecciones municipales españolas, en las que, según la ley, los municipios utilizan dos sistemas electorales distintos: uno de listas cerradas, en el que los votantes votan por un partido, o uno de listas abiertas, en el que votan por candidatos individuales. Usando un análisis de regresión discontinua, encontramos que el sistema de listas cerradas aumenta 2,5 puntos porcentuales la proporción de mujeres entre los candidatos y los concejales, y 4,3 puntos porcentuales entre los alcaldes. Según el modelo, estos resultados se explican por un sesgo de los votantes. Proporcionamos evidencia que apoya el mecanismo del modelo. En particular, mostramos que, con carácter general, cuando dos concejales casi empatan en votos, es considerablemente más probable que el que obtuvo «un voto más» sea nombrado alcalde, pero este resultado no se observa con generalidad cuando el más votado fue una mujer y el segundo un hombre, lo que sugiere la presencia de un cierto sesgo de género. También mostramos que, en una submuestra de municipios con poco sesgo —aquellos que han tenido una alcaldesa en el pasado—, la diferencia entre los dos sistemas electorales desapareceWe study how electoral systems affect the presence of women in politics using a model in which both voters and parties might have a gender bias. We apply the model to Spanish municipal elections, in which national law mandates that municipalities follow one of two different electoral systems: a closed-list system in which voters pick one party-list, or an open-list system, in which voters pick individual candidates. Using a regression discontinuity design, we find that the closed-list system increases the share of women among candidates and councilors by 2.5 percentage points, and the share of women among mayors by 4.3 percentage points. Our model explains these results as mostly driven by voter bias against women. We provide evidence that supports the mechanism of the model. In particular, we show that, when two councilors almost tied in general-election votes, the one with “one more vote” is substantially more likely to be appointed mayor, but this does not happen when the most voted was female and the second was male, suggesting the presence of some voter bias. We also show that, in a subsample of municipalities with low bias — proxied by having had a female mayor in the past — the difference between the two electoral systems disappear

The CKM parameters in the SMEFT

The extraction of the Cabibbo-Kobayashi-Maskawa (CKM) matrix from flavour observables can be affected by physics beyond the Standard Model (SM). We provide a general roadmap to take this into account, which we apply to the case of the Standard Model Effective Field Theory (SMEFT). We choose a set of four input observables that determine the four Wolfenstein parameters, and discuss how the effects of dimension-six operators can be included in their definition. We provide numerical values and confidence intervals for the CKM parameters, and compare them with the results of CKM fits obtained in the SM context. Our approach allows one to perform general SMEFT analyses in a consistent fashion, independently of any assumptions about the way new physics affects flavour observables. We discuss a few examples illustrating how our approach can be implemented in practice.Comment: 36 pages. Version published in JHE

Duality violation in QCD Sum Rules with the LR correlator

5 páginas, 4 figuras.-- Dedicated to the memory of our colleague and friend Joaquim (Ximo) Prades.-- Talk given at the 15th International QCD Conference (Montpellier, 28th June - 3rd July 2010) and the Internation Light Cone 2010 Conference (Valencia, 14-18th June 2010).-- arXiv:1010.1219v1.We analyse the so-called violations of quark-hadron duality in Finite Energy Sum Rules with the LR correlator, through the study of the possible high-energy behavior of the LR spectral function, taking into account all known short-distance constraints and the experimental tau-decay data. In particular we show that the use of pinched weights allows to determine with high accuracy the dimension six and eight contributions in the Operator-Product Expansion, O_6 = (-4.3^{+0.9}_{-0.7}) 10^{-3} GeV^6 and O_8 = (-7.2^{+4.2}_{-5.3}) 10^{-3} GeV^8.This work has been partly supported by the EU network FLAVIAnet [MRTN-CT-2006-035482], by MICINN, Spain [FPA2007-60323, FPA2006-05294 and CSD2007-00042 –CPAN–], by Generalitat Valenciana [Prometeo/2008/069] and by Junta de Andaluc´ıa [P07-FQM 03048 and P08-FQM 101].Peer reviewe

Reactor neutrino oscillations as constraints on Effective Field Theory

We study constraints on the Standard Model Effective Field Theory (SMEFT) from neutrino oscillations in short-baseline reactor experiments. We calculate the survival probability of reactors antineutrinos at the leading order in the SMEFT expansion, that is including linear effects of dimension-6 operators. It is shown that, at this order, reactor experiments alone cannot probe charged-current contact interactions between leptons and quarks that are of the (pseudo)vector (V$\pm$A) or pseudo-scalar type. We also note that flavor-diagonal (pseudo)vector coefficients do not have observable effects in oscillation experiments. In this we reach novel or different conclusions than prior analyses of non-standard neutrino interactions. On the other hand, reactor experiments offer a unique opportunity to probe tensor and scalar SMEFT operators that are off-diagonal in the lepton-flavor space. We derive constraints on the corresponding SMEFT parameters using the most recent data from the Daya Bay and RENO experiments.Comment: 36 pages, 6 figures. v2: corrected sign error in tensor contribution (d_T); references and comments added; discussion improved. v3: analysis improved, published versio