Unitarity Triangle from CP invariant quantities

We construct the CKM unitarity triangle from CP invariant quantities, using the coupling constant of weak decays with flavor change from b to u, and the particle - antiparticle mixing probability in the B_s and B_d systems. Also included are new measurements of the coupling V_us in Kaon decays. Of the two solutions, one agrees perfectly with the triangle constructed from CP violating processes in the K and B meson systems. The common solution yields a triangle with an area of J/2 = (1.51 +/- 0.09) x 10^{-5} and a CP violating phase gamma = 63.1^o +/- 4.0^o.Comment: 8 pages, 3 figure

High antibody levels and reduced cellular response in children up to one year after SARS-CoV-2 infection.

The COVID-19 course and immunity differ in children and adults. We analyzed immune response dynamics in 28 families up to 12 months after mild or asymptomatic infection. Unlike adults, the initial response is plasmablast-driven in children. Four months after infection, children show an enhanced specific antibody response and lower but detectable spike 1 protein (S1)-specific B and T cell responses than their parents. While specific antibodies decline, neutralizing antibody activity and breadth increase in both groups. The frequencies of S1-specific B and T cell responses remain stable. However, in children, one year after infection, an increase in the S1-specific IgA class switch and the expression of CD27 on S1-specific B cells and T cell maturation are observed. These results, together with the enhanced neutralizing potential and breadth of the specific antibodies, suggest a progressive maturation of the S1-specific immune response. Hence, the immune response in children persists over 12 months but dynamically changes in quality, with progressive neutralizing, breadth, and memory maturation. This implies a benefit for booster vaccination in children to consolidate memory formation

Search for heavy neutrinos in K+→μ+νμK^+ \rightarrow \mu^+ \nu_{\mu} decays

International audienceThe NA62 experiment recorded a large sample of K+→μ+νμ decays in 2007. A peak search has been performed in the reconstructed missing mass spectrum. In the absence of a signal, limits in the range 2×10−6 to 10−5 have been set on the squared mixing matrix element |Uμ4|2 between muon and heavy neutrino states, for heavy neutrino masses in the range 300–375 MeV/ c2 . The result extends the range of masses for which upper limits have been set on the value of |Uμ4|2 in previous production search experiments

Measurement of the form factors of charged kaon semileptonic decays

International audienceA measurement of the form factors of charged kaon semileptonic decays is presented, based on 4.4 × 10$^{6}$K$^{±}$ → π$^{0}$e$^{±}$ν$_{e}$ (K$_{e3}^{±}$ ) and 2.3 × 10$^{6}$K$^{±}$ → π$^{0}$μ±ν$_{μ}$ (K$_{μ3}^{±}$ ) decays collected in 2004 by the NA48/2 experiment. The results are obtained with improved precision as compared to earlier measurements. The combination of measurements in the K$_{e3}^{±}$ and K$_{μ3}^{±}$ modes is also presented

First observation and study of the K±→π0π0μ±νK^{\pm} \rightarrow \pi^{0} \pi^{0} \mu^{\pm} \nu decay

International audienceThe NA48/2 experiment at CERN reports the first observation of the K$^{±}$ → π$^{0}$π$^{0}$μ$^{±}$ν decay based on a sample of 2437 candidates with 15% background contamination collected in 2003–2004. The decay branching ratio in the kinematic region of the squared dilepton mass above 0.03 GeV$^{2}$/c$^{4}$ is measured to be (0.65 ± 0.03) × 10$^{−6}$. The extrapolation to the full kinematic space, using a specific model, is found to be (3.45 ± 0.16) × 10$^{−6}$, in agreement with chiral perturbation theory predictions

Review of Particle Physics, 1998-1999

A comprehensive review of the field of Particle Physics produced by the Particle Data Group (PDG). Includes a compilation/evaluation of data on particle properties, summary tables with best values and limits for particle properties, extensive summari particles, and a long section of reviews, tables, and plots on a wide variety of theoretical and experimental topics of interest to particle and astrophysicists

First observation and study of the K±→π0π0μ±νK^{\pm} \rightarrow \pi^{0} \pi^{0} \mu^{\pm} \nu decay

The NA48/2 experiment at CERN reports the first observation of the $K^{\pm} \rightarrow \pi^{0} \pi^{0} \mu^{\pm} \nu$ decay based on a sample of 2437 candidates with 15% background contamination collected in 2003-2004. The decay branching ratio in the kinematic region of the squared dilepton mass above $0.03$~GeV$^2/c^4$ is measured to be $(0.65 \pm 0.03) \times 10^{-6}$. The extrapolation to the full kinematic space, using a specific model, is found to be $(3.45 \pm 0.17) \times 10^{-6}$, in agreement with chiral perturbation theory predictions