The mass of the $\pi^-$

The most precise values of the mass of the negatively charged pion have been determined from several measurements of X-ray wavelengths for transitions in pionic atoms at PSI. The Particle Data Group gives the average m_{\pi^-}mπ− = (139.570 61 \pm± 0.000 24) MeV/c^22.

The mass of the 4\pi^+$

The most precise value for the pion mass was determined from a precision measurement at PSI of the muon momentum in pion decay at rest, \pi^+ \rightarrow \mu^+ + \nu_{\mu}π+→μ++νμ. The result is m_{\pi^+} = 139.570\,21(14)mπ+=139.57021(14)~MeV/c^22. This value is more precise, however, in agreement with the recent compilation of the Particle Data Group for m_{\pi^-}mπ−. The agreement of m_{\pi^+}mπ+ with the recent measurement. This yields a new quantitative measure of CPT invariance in the pion sector: (m_{\pi^+} - m_{\pi^-})/m_{\pi}(\mbox{av}) = (-2.9 \pm 2.0)\cdot 10^{-6}(mπ+−mπ−)/mπ(av)=(−2.9±2.0)⋅10−6, an improvement by two orders of magnitude.

ON THE SEARCH FOR HADRON MODES OF HIDDEN CHARM MESONS DECAY

From the results obtained in publication [1] as well percentage between decay modes of exitated states of mesons, cited in reference book “Particle Data Group” became possible to evaluate the number of hadron final states on which the meson with hidden charm decay. In the paper is shown a rough estimate of final states number for hadron decays of mesons with hidden charm. The most statistically secured are the final states for ηс (1 S), 2 (π+π-) and π+π- K+K- for χс0 (1P) mesons.

Standard versus non-standard CP phases in neutrino oscillation in matter with non-unitarity

We formulate a perturbative framework for the flavor transformation of the standard active three neutrinos but with a non-unitary flavor mixing matrix, a system which may be relevant for the leptonic unitarity test. We use the $\alpha$ parametrization of the non-unitary matrix and take its elements $\alpha_{\beta \gamma}$ ($\beta,\gamma = e,\mu,\tau$) and the ratio $\epsilon \simeq \Delta m^2_{21} / \Delta m^2_{31}$ as the small expansion parameters. Two qualitatively new features that hold in all the oscillation channels are uncovered in the probability formula obtained to first order in the expansion: (1) The phases of the complex $\alpha$ elements always come into the observable in the particular combination with the $\nu$SM CP phase $\delta$ in the form $[e^{- i \delta } \bar{\alpha}_{\mu e}, ~e^{ - i \delta} \bar{\alpha}_{\tau e}, ~\bar{\alpha}_{\tau \mu}]$ under the Particle Data Group convention of a unitary $\nu$SM mixing matrix. (2) The diagonal $\alpha$ parameters appear in particular combinations $\left( a/b - 1 \right) \alpha_{ee} + \alpha_{\mu \mu}$ and $\alpha_{\mu \mu} - \alpha_{\tau \tau}$, where $a$ and $b$ denote, respectively, the matter potential due to charged current and neutral current reactions. This property holds only in the unitary evolution part of the probability, and there is no such feature in the genuine non-unitary part, while the $\delta$–$\alpha$ parameter phase correlation exists for both. The reason for such remarkable stability of the phase correlation is discussed.

Power Laws and Elementary Particle Decays

This study analyzes the correlation between the lifetime and the rest energy of the unstable particle states with a lifetime greater than the zeptosecond (10−21 s), using data available from the Particle Data Group. This set of states seems to be divided into three groups, in each of which the two quantities can be correlated through a remarkably accurate power law. Although this fact does not represent anything new compared to the predictions of the Standard Model, it nevertheless reveals an unexpected order structure in the set of particle decays, emerging from such predictions.

𝜃23 = π/4 and δ = −π/2 in neutrino mixing, which convention?

Considerable information has been obtained about neutrino mixing matrix. Present data show that in the particle data group (PDG) parametrization, the 2–3 mixing angle and the CP violating phase are consistent with [Formula: see text] and [Formula: see text], respectively. A lot of efforts have been devoted to constructing models in realizing a mixing matrix with these values. However, the particular angles and phase are parametrization convention dependent. The meaning about the specific values for mixing angle and phase needs to be clarified. Using the well-known nine independent ways of parametrizing the mixing matrix, we show in detail how the mixing angles and phase change with conventions even with the 2–3 mixing angle to be [Formula: see text] and the CP violating phase to be [Formula: see text]. The original Kobayashi–Maskawa and an additional one belong to such a category. The other 6 parametrizations have mixing angles and phase very different values from those in the PDG parametrization although the physical effects are the same. Therefore one should give the specific parametrization convention when making statements about values for mixing angles and phase.

Power Laws and Elementary Particle Decays

This study analyzes the correlation between the lifetime and the rest energy of the unstable particle states with a lifetime greater than the zeptosecond (10−21 s), using data available from the Particle Data Group. This set of states seems to be divided into three groups, in each of which the two quantities can be correlated through a remarkably accurate power law. Although this fact does not represent anything new compared to the predictions of the Standard Model, it nevertheless reveals an unexpected order structure in the set of particle decays, emerging from such predictions.

Power Laws and Elementary Particle Decays

This study analyzes the correlation between the lifetime and the rest energy of the unstable particle states with a lifetime greater than the zeptosecond (10−21 s), using data available from the Particle Data Group. This set of states seems to be divided into three groups, in each of which the two quantities can be correlated through a remarkably accurate power law. Although this fact does not represent anything new compared to the predictions of the Standard Model, it nevertheless reveals an unexpected order structure in the set of particle decays, emerging from such predictions.

Addendum to predicting the $K^0\Lambda$ photoproduction observables by using the multipoles approach

We present an addendum to our previous paper to improve the performance of the proposed isobar model in describing the $\gamma + n\to K^0+\Lambda$ reaction observables. Since two new data sets have become available for this reaction channel that show sizable discrepancies, i.e. the CLAS and MAMI data, we propose three different models, M1, M2, and M3, obtained from including the CLAS, MAMI, and both data sets, respectively, in the fitting database. The new models can nicely describe the $\gamma+p\to K^++\Lambda$ observables, as in the case of the previous model, but significantly improve the agreement with the new $\gamma + n\to K^0+\Lambda$ cross section data. The extracted resonance properties in the present models can be well constrained within the current Particle Data Group estimates. The different contributions of the background and resonance terms in the previous and present calculations are thoroughly discussed. A brief discussion on the problem of data discrepancy is also presented.

Semi-leptonic decays of a particle to three bodies

Is presented the dynamics and kinematics of the semi-leptonic decays with interaction V-A calculating the decay width and the fraction of decay for each process using spectator model. The results are compared with the experimental data of the table particle data group, which show that the model prediction for this type of decay can be considered as a first approximation. This type of analysis is particularly important because it allows one hand, introduce to the beginner students to the study of particle physics and on the other gives the possibility to use strategies to address topics modern in physics courses at university level.