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Measurement of the Average Polarization of b Baryons in Hadronic Z^0 Decays
High Energy Physics - Experiment · Submitted 10 Aug 1998
abstract compiled · 2026-09-23 · no language-model review
The authors' main claim From a fit to the distribution of this ratio, the value <P_L^{\Lambda_b}> = -0.56^{+0.20}_{-0.13} +/- 0.09 is obtained, where the first error is statistical and the second systematic.
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The abstract, sentence by sentence
In the Standard Model, b quarks produced in e^+e^- annihilation at the Z^0 peak have a large average longitudinal polarization of -0.94. Some fraction of this polarization is expected to be transferred to b-flavored baryons during hadronization. The average longitudinal polarization of weakly decaying b baryons, <P_L^{\Lambda_b}>, is measured in approximately 4.3 million hadronic Z^0 decays collected with the OPAL detector between 1990 and 1995 at LEP. Those b baryons that decay semileptonically and produce a \Lambda baryon are identified through the correlation of the baryon number of the \Lambda and the electric charge of the lepton. In this semileptonic decay, the ratio of the neutrino energy to the lepton energy is a sensitive polarization observable. The neutrino energy is estimated using missing energy measurements. From a fit to the distribution of this ratio, the value <P_L^{\Lambda_b}> = -0.56^{+0.20}_{-0.13} +/- 0.09 is obtained, where the first error is statistical and the second systematic.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | In the Standard Model, b quarks produced in e^+e^- annihilation at the Z^0 peak have a large average longitudinal polarization of -0.94. | background 1.00 | 0.05 | 0.03 | asserted 1.00 |
| s1 | Some fraction of this polarization is expected to be transferred to b-flavored baryons during hadronization. | background 0.99 | 0.05 | 0.02 | hedged possibility 0.91 |
| s2 | The average longitudinal polarization of weakly decaying b baryons, <P_L^{\Lambda_b}>, is measured in approximately 4.3 million hadronic Z^0 decays collected with the OPAL detector between 1990 and 1995 at LEP. | contribution 0.59 | 0.96 | 0.07 | asserted 1.00 |
| s3 | Those b baryons that decay semileptonically and produce a \Lambda baryon are identified through the correlation of the baryon number of the \Lambda and the electric charge of the lepton. | method 1.00 | 0.80 | 0.02 | asserted 1.00 |
| s4 | In this semileptonic decay, the ratio of the neutrino energy to the lepton energy is a sensitive polarization observable. | method 0.94 | 0.21 | 0.03 | asserted 0.99 |
| s5 | The neutrino energy is estimated using missing energy measurements. | method 1.00 | 0.85 | 0.02 | asserted 1.00 |
| s6 | From a fit to the distribution of this ratio, the value <P_L^{\Lambda_b}> = -0.56^{+0.20}_{-0.13} +/- 0.09 is obtained, where the first error is statistical and the second systematic. | result 1.00 | 0.97 | 0.93 | asserted 1.00 |
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The paper
Original abstract
In the Standard Model, b quarks produced in e^+e^- annihilation at the Z^0 peak have a large average longitudinal polarization of -0.94. Some fraction of this polarization is expected to be transferred to b-flavored baryons during hadronization. The average longitudinal polarization of weakly decaying b baryons, <P_L^{\Lambda_b}>, is measured in approximately 4.3 million hadronic Z^0 decays collected with the OPAL detector between 1990 and 1995 at LEP. Those b baryons that decay semileptonically and produce a \Lambda baryon are identified through the correlation of the baryon number of the \Lambda and the electric charge of the lepton. In this semileptonic decay, the ratio of the neutrino energy to the lepton energy is a sensitive polarization observable. The neutrino energy is estimated using missing energy measurements. From a fit to the distribution of this ratio, the value <P_L^{\Lambda_b}> = -0.56^{+0.20}_{-0.13} +/- 0.09 is obtained, where the first error is statistical and the second systematic.
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References
How the literature uses it
17 arXiv papers cite this in 19 sentences
Papers citing it · 16 sentences without a confident label
Uses its data or values 2 papers
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An approximate combination of the LEP measurements [ref] gives $r_L = 0.47 ±0.14$ for the $b$ quarks.
Prospects for measuring quark polarization and spin correlations in $b\bar{b}$ and $c\bar{c}$ samples at the LHC · Introduction · 1.00
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An approximate combination of the LEP measurements [ref] gives $r_L = 0.47 ±0.14$.
Entanglement and Bell nonlocality with bottom-quark pairs at hadron colliders · Introduction · 1.00
Cites it as background 1 paper
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This assumption was studied at LEP in collisions where the polarisation of baryons was used to probe the electroweak structure of the boson production and decays [ref] .
First measurement of prompt and non-prompt ${\rm D^{*+}}$ vector meson spin alignment in pp collisions at $\sqrt{s} = 13$ TeV · Introduction · 0.80
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