Publication

Precision <i>CP</i> Symmetry Test and Polarization Analysis in Σ<SUP>+</SUP> Decays

2025

Abstract

A stringent test of CP symmetry in hyperon decays is performed using 1.0 x 10(10) J/psi events and 2.7 x 10(9) psi(3686) events collected by the BESIII experiment. The CP asymmetry in the two-body nonleptonic weak decays Sigma(+) -> p pi(0) and (Sigma) over bar (-) -> (p) over bar pi(0) is determined to be A(CP) = -0.0118 +/- 0.0083(stat) +/- 0.0028(syst), consistent with CP conservation. The average decay parameter = -0.9869 +/- 0.0011(stat) +/- 0.0016(syst) represents the most precise measurement in the baryon sector to date. A model-independent analysis of the hyperon polarization is performed for the first time at J/psi and psi(3686) resonances, revealing a clear sign reversal and offering new insight into SU(3) symmetry breaking and baryon internal structure. These results provide the most stringent constraints on CP violation in Sigma decays and establish a benchmark for future precision studies.

Official source

https://infoscience.epfl.ch/entities/publication/759b84f8-3ef9-43df-9c85-cbdabe73474c

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2025

Abstract

Official source

https://infoscience.epfl.ch/entities/publication/759b84f8-3ef9-43df-9c85-cbdabe73474c

About this result

Related concepts (32)

CP violation

In particle physics, CP violation is a violation of CP-symmetry (or charge conjugation parity symmetry): the combination of C-symmetry (charge symmetry) and P-symmetry (parity symmetry). CP-symmetry states that the laws of physics should be the same if a particle is interchanged with its antiparticle (C-symmetry) while its spatial coordinates are inverted ("mirror" or P-symmetry). The discovery of CP violation in 1964 in the decays of neutral kaons resulted in the Nobel Prize in Physics in 1980 for its discoverers James Cronin and Val Fitch.

Baryon asymmetry

In physical cosmology, the baryon asymmetry problem, also known as the matter asymmetry problem or the matter–antimatter asymmetry problem, is the observed imbalance in baryonic matter (the type of matter experienced in everyday life) and antibaryonic matter in the observable universe. Neither the standard model of particle physics nor the theory of general relativity provides a known explanation for why this should be so, and it is a natural assumption that the universe is neutral with all conserved charges.

T-symmetry

T-symmetry or time reversal symmetry is the theoretical symmetry of physical laws under the transformation of time reversal, Since the second law of thermodynamics states that entropy increases as time flows toward the future, in general, the macroscopic universe does not show symmetry under time reversal. In other words, time is said to be non-symmetric, or asymmetric, except for special equilibrium states when the second law of thermodynamics predicts the time symmetry to hold.

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Precision <i>CP</i> Symmetry Test and Polarization Analysis in Σ<SUP>+</SUP> Decays

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