The $\pi^0$ mass and the first experimental verification of Coulomb de-excitation in pionic hydrogen

The most precise value for the \pi^0π0 mass was obtained from the measurement of the mass difference m_{\pi^-}-m_{\pi^0} = 4.593\,64(48)mπ−−mπ0=4.59364(48),MeV/c^22 in the charge exchange reaction \pi^-π−p \rightarrow \pi^0→π0n at PSI. With the most precise charged pion mass value, m_{\pi^+} = 139.570\,21(14)mπ+=139.57021(14),MeV/c^22 and the validity of the CPT theorem (m_{\pi^-} = m_{\pi^+}mπ−=mπ+), a value m_{\pi^0} = 134.976\,57(50)mπ0=134.97657(50),MeV/c^22 is obtained. The measurements also revealed, for the first time, evidence of an unexpectedly large contribution from Coulomb de-excitation states during the pionic atom cascade.

CPTM Symmetry for the Dirac Equation and Its Extended Version Based on the Vector Representation of the Lorentz Group

We revisit the CPT theorem for the Dirac equation and its extended version based on the vector representation of the Lorentz group. Then it is proposed that CPTM may apply to this fundamental equation for a massive fermion a s a singlet or a doublet with isospin. The symbol M stands here for reversing the sign of the mass in the Dirac equation, which can be accomplished by operation on it with the so-called gamma-five matrix that plays an essential role for the chirality in the Standard Model. We define the CPTM symmetry for the standard and extended Dirac equation and discuss its physical implications and some possible consequences for general relativity.

Does the Electron Have an Anomalous Electric Dipole Moment?

An analysis is presented of the possible existence of a second anomalous dipole moment of Dirac’s particle next to the angular one. It includes a discussion why, in spite of his own derivation, Dirac has denied its relevancy. It is shown why since then it has been overlooked and why it has vanished from leading textbooks. A critical survey is given on the reasons of its reject, including the failure of attempts to measure and its perceived violation of the CPT theorem. Moreover, by reference from literature, the possible impact is discussed in the nuclear domain and in the gravitational domain if it would exist.

Does the Electron Have an Anomalous Electric Dipole Moment?

An analysis is presented of the possible existence of a second anomalous dipole moment of Dirac’s particle next to the angular one. It includes a discussion why, in spite of his own derivation, Dirac has denied its relevancy. It is shown why since then it has been overlooked and why it has vanished from leading textbooks. A critical survey is given on the reasons of its reject, including the failure of attempts to measure and its perceived violation of the CPT theorem. Moreover, by reference from literature, the possible impact is discussed in the nuclear domain and in the gravitational domain if it would exist.

Measurement of the angular distribution of prompt gamma-rays emitted in the 117Sn(n, γ) reaction for a T-violation search

It is theoretically suggested that the violation of charge conjugation and parity symmetry (CP-violation) could be enhanced in several compound nuclear reactions. According to the CPT theorem the violation of time-reversal symmetry (T-violation) would be enhanced too. The experimental sensitivity to find a T-violating effect in neutron-induced compound nuclear reactions depends on the value of a spin factor κ(J), which is a parameter specific for each nuclide. It can be determined from the angular dependence of γ-ray emission in (n,γ) reactions induced near a p-wave resonance. In this paper, the measurement result and the analysis status of experiments using the target nucleus 117Sn are reported.

The Discrete Symmetries of the Fundamental Interactions⋆⋆⋆

Continuous and discrete symmetries. Parity (P) and its violation. T.D. Lee, C.N. Yang, and Madame Wu. The chirality of spin-1/2 particles. Left- and right-handed neutrinos. Sterile neutrinos. Charge-conjugation (C). The matter-antimatter question for neutrinos. Majorana neutrinos. Quantum baseball. Time reversal (T). The combined CP and CPT symmetries. The CPT theorem.

Are there discrete symmetries in relativistic quantum mechanics?

Since the CPT theorem was introduced in the 20th century, it has been one of the most important ongoing projects in particle physics. The CPT invariance helps to indicate if there are discrete symmetries in relativistic quantum mechanics (RQM), the answer to this question is ambiguous. This paper will mainly explain the answers via the timeline and point out misnomers and some missing concepts. We claim the answer to Are There Discrete Symmetries in Relativistic Quantum Mechanics is “yes, but no, no and yes again”. The most recent experiment shows the violation of CPT invariance is only [Formula: see text].