Kaon Photoproduction and the $\Lambda$ Decay Parameter ${\alpha }_{-}$

Abstract

The weak decay parameter ${\alpha }_{-}$ of the $\Lambda$ is an important quantity for the extraction of polarization observables in various experiments. Moreover, in combination with ${\alpha }_{+}$ from $\bar{\Lambda }$ decay it provides a measure for matter-antimatter asymmetry. The weak decay parameter also affects the decay parameters of the $\Xi$ and $\Omega$ baryons and, in general, any quantity in which the polarization of the $\Lambda$ is relevant. The recently reported value by the BESIII collaboration of $0.750(9)(4)$ is significantly larger than the previous PDG value of $0.642(13)$ that had been accepted and used for over 40 years. In this work we make an independent estimate of ${\alpha }_{-}$, using an extensive set of polarization data measured in kaon photoproduction in the baryon resonance region and constraints set by spin algebra. The obtained value is 0.721(6)(5). The result is corroborated by multiple statistical tests as well as a modern phenomenological model, showing that our new value yields the best description of the data in question. Our analysis supports the new BESIII finding that ${\alpha }_{-}$ is significantly larger than the previous PDG value. Any experimental quantity relying on the value of ${\alpha }_{-}$ should therefore be re-considered.

6 pages, 1 figure;

References in corpus (25)

• emcee: The MCMC Hammer
• Global $\Lambda$ hyperon polarization in nuclear collisions: evidence for the most vortical fluid
• Polarization and Entanglement in Baryon-Antibaryon Pair Production in Electron-Positron Annihilation
• Coupled-channel dynamics in the reactions piN --> piN, etaN, KLambda, KSigma
• Completeness Rules for Spin Observables in Pseudoscalar Meson Photoproduction
• Differential cross section and recoil polarization measurements for the gamma p to K+ Lambda reaction using CLAS at Jefferson Lab
• First Measurement of Beam-Recoil Observables Cx and Cz in Hyperon Photoproduction
• Fitting Parton Distribution Data with Multiplicative Normalization Uncertainties
• Measurement of matter-antimatter differences in beauty baryon decays
• Eta photoproduction in a combined analysis of pion- and photon-induced reactions
• Determining pseudoscalar meson photo-production amplitudes from complete experiments
• Photocouplings at the Pole from Pion Photoproduction
• First Measurement of Transferred Polarization in the Exclusive e p --> e' K+ Lambda Reaction
• Isospin decomposition of $\gamma N\to N^{\ast }$ transitions within a dynamical coupled-channels model
• Photoproduction of $\Lambda$ and ${\Sigma }^0$ hyperons using linearly polarized photons
• The impact of ${\mathbf{K}}^{+}\mathbf{\Lambda }$ photoproduction on the resonance spectrum
• Bayesian inference of the resonance content of p(gamma,K^+)Lambda
• Beam-Recoil Polarization Transfer in the Nucleon Resonance Region in the Exclusive $\vec{e}p\to e^{\prime }{K}^{+}\vec{\Lambda }$ and $\vec{e}p\to e^{\prime }{K}^{+}{\vec{\Sigma }}^0$ Reactions at CLAS
• Strong evidence for nucleon resonances near 1900\,MeV
• Coupled-channel analysis of $K\Sigma$ production on the nucleon up to 2.0 GeV
• Measurement of the transverse polarization of $\Lambda$ and $\bar{\Lambda }$ hyperons produced in proton-proton collisions at $\sqrt{s}=7$ TeV using the ATLAS detector
• Partial-Wave Analysis of $\gamma p\to K^{+}\Lambda$ using a multichannel framework
• Final state interactions in nonleptonic hyperon decays
• First Measurement of ${\Xi }^{-}$ Polarization in Photoproduction
• Weak and Electromagnetic Interactions of Hyperons: a Chiral Approach

Cited by in corpus (23)

• Polarization of $\Lambda$ ($\bar{\Lambda }$) hyperons along the beam direction in Au+Au collisions at $\sqrt{s_{{}_{NN}}}$ = 200 GeV
• Weak phases and CP-symmetry tests in sequential decays of entangled double-strange baryons
• Precise Measurements of Decay Parameters and $CP$ Asymmetry with Entangled $\Lambda -\bar{\Lambda }$ Pairs
• Light Baryon Spectroscopy
• Flavor Anomalies in Heavy Quark Decays
• Tests of $CP$ symmetry in the entangled ${\Xi }^0-{\bar{\Xi }}^0$ Pairs
• Hyperon electromagnetic form factors in the timelike region
• Study of CP violation in hyperon decays at Super Charm-Tau Factories with a polarized electron beam
• Light baryon resonances from a coupled-channel study including $\mathbf{K\Sigma }$ photoproduction
• Jülich-Bonn-Washington Model for Pion Electroproduction Multipoles
• Probing the internal structure of baryons
• Measurement of the ${\Lambda }_b^0\to J/\psi \Lambda$ angular distribution and the ${\Lambda }_b^0$ polarisation in $pp$ collisions
• Lifetime of the hypertriton
• The potential of $\Lambda$ and ${\Xi }^{-}$ studies with PANDA at FAIR
• Coupled $K^{+}\Lambda$ and $K^0\Lambda$ photoproduction off the nucleon: Consequences from the recent CLAS and MAMI data and the $N(1680)P_{11}$ narrow state
• First simultaneous measurement of ${\Xi }^0$ and ${\bar{\Xi }}^0$ asymmetry parameters in $\psi (3686)$ decay
• Partial wave analysis of the charmed baryon hadronic decay ${\Lambda }_c^{+}\to \Lambda {\pi }^{+}{\pi }^0$
• Production and decay of polarized hyperon-antihyperon pairs
• Beam-Recoil Transferred Polarization in $K^{+}Y$ Electroproduction in the Nucleon Resonance Region with CLAS12
• Estimates of exchange topological contributions and $CP$-violating observables in ${\Lambda }_b\to \Lambda \varphi$ decay
• Prospects of $CP$ violation in $\Lambda$ decay with polarized electron beam at STCF
• Unraveling the structure of $\Lambda$ hyperons with polarized $\Lambda \bar{\Lambda }$ pairs
• Elliptical Polarization in Partial Wave Analysis of Two Spinless Meson Photoproduction