${{\mathit \Lambda}_{{b}}^{0}}$ DECAY PARAMETERS

See the note on ``Baryon Decay Parameters'' in the neutron Listings.

$\alpha $ decay parameter for ${{\mathit \Lambda}_{{b}}}$ $\rightarrow$ ${{\mathit J / \psi}}{{\mathit \Lambda}}$

INSPIRE   PDGID:
S040A01
VALUE DOCUMENT ID TECN  COMMENT
$\bf{ -0.017 \pm0.026}$ OUR AVERAGE
$-0.022$ ${}^{+0.027}_{-0.026}$ 1
AAIJ
2020O
 LHCB ${{\mathit p}}{{\mathit p}}$ at 7, 8, 13 TeV
$-0.14$ $\pm0.14$ $\pm0.10$ 2
SIRUNYAN
2018R
 CMS ${{\mathit p}}{{\mathit p}}$ at 7, 8 TeV
$0.30$ $\pm0.16$ $\pm0.06$ 3
AAD
2014L
 ATLS ${{\mathit p}}{{\mathit p}}$ at 7 TeV
• • We do not use the following data for averages, fits, limits, etc. • •
$0.05$ $\pm0.17$ $\pm0.07$ 4
AAIJ
2013AG
 LHCB Repl. by AAIJ 2020O
1  Extracted using a Bayesian analysis. The most probable value is given as $-0.022$, with a 68$\%$ credibility interval [-0.048, 0.005]. Transverse polarizations of ${{\mathit \Lambda}_{{b}}^{0}}$ of $-0.004$ (68$\%$ credibility interval [-0.064, 0.051]), 0.001 (68$\%$ credibility interval [-0.035, 0.045]), and 0.032 (68$\%$ credibility interval [-0.011, 0.065]) are also reported at 7 TeV, 8 TeV and 13 TeV, respectively. Note that both statistical and systematic uncertainties are included.
2  An angular analysis of ${{\mathit \Lambda}_{{b}}}$ $\rightarrow$ ${{\mathit J / \psi}}{{\mathit \Lambda}}$ decay is performed. Note that the sign of ${{\mathit \alpha}}$ in CMS definition is the opposite to that used by AAIJ 2013AG and AAD 2014L. ${{\mathit \Lambda}_{{b}}}$ transverse production polarization of $0.00$ $\pm0.06$ $\pm0.06$ is also reported, as well as squares of the helicity amplitudes.
3  An angular analysis of ${{\mathit \Lambda}_{{b}}}$ $\rightarrow$ ${{\mathit J / \psi}}{{\mathit \Lambda}}$ decay is performed and magnitudes of all helicity amplitudes are also reported.
4  An angular analysis of ${{\mathit \Lambda}_{{b}}}$ ${{\mathit \Lambda}}$ decay is performed and a ${{\mathit \Lambda}_{{b}}}$ transverse production polarization of $0.06$ $\pm0.07$ $\pm0.02$ is also reported.
References:
AAIJ 2020O
JHEP 2006 110 Measurement of the $\Lambda^0_b\rightarrow J/\psi\Lambda$ angular distribution and the $\Lambda^0_b$ polarisation in $pp$ collisions
SIRUNYAN 2018R
PR D97 072010 Measurement of the $\Lambda_b$ polarization and angular parameters in $\Lambda_b\to J/\psi\, \Lambda$ decays from pp collisions at $\sqrt{s}=$ 7 and 8 TeV
AAD 2014L
PR D89 092009 Measurement of the Parity-Violating Asymmetry Parameter ${{\mathit \alpha}}_{b}$ and the Helicity Amplitudes for the Decay ${{\mathit \Lambda}_{{b}}^{0}}$ $\rightarrow$ ${{\mathit J / \psi}}{+}$ ${{\mathit \Lambda}^{0}}$ with the ATLAS Detector
AAIJ 2013AG
PL B724 27 Measurements of the ${{\mathit \Lambda}_{{b}}^{0}}$ $\rightarrow$ ${{\mathit J / \psi}}{{\mathit \Lambda}}$ Decay Amplitudes and the ${{\mathit \Lambda}_{{b}}^{0}}$ Polarisation in ${{\mathit p}}{{\mathit p}}$ Collisions at $\sqrt {s }$ = 7 TeV