Symbol R
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Resolved: the LHCb lepton-universality ratios. Measurements of R(K) and R() — ratios comparing B -meson decays to muon pairs versus electron pairs, which the Standard Model predicts should be equal — showed apparent deviations through 2021 that fueled substantial theoretical interest in new mediator particles. LHCb’s December 2022 reanalysis, using the full Run 1 and Run 2 dataset with improved control of electron-misidentification backgrounds, found both ratios consistent with the Standard Model at the one-standard-deviation level. LHCb spokesperson Chris Parkes attributed the earlier apparent deviation to systematic effects in background modeling, not a statistical fluctuation in the…
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Symbol K^*
is a part of this expression. Its role is fixed by the surrounding article and by the operations shown in the formula.
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Equation 10 · Physics
How Particle Physics Beyond the Standard Model Actually Works
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Resolved: the LHCb lepton-universality ratios. Measurements of R(K) and R() — ratios comparing B -meson decays to muon pairs versus electron pairs, which the Standard Model predicts should be equal — showed apparent deviations through 2021 that fueled substantial theoretical interest in new mediator particles. LHCb’s December 2022 reanalysis, using the full Run 1 and Run 2 dataset with improved control of electron-misidentification backgrounds, found both ratios consistent with the Standard Model at the one-standard-deviation level. LHCb spokesperson Chris Parkes attributed the earlier apparent deviation to systematic effects in background modeling, not a statistical fluctuation in the…
Equation guide → · Article →Equation 7 · Physics
From Origins to Frontier: A History of Particle Physics Beyond the Standard Model
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Flavor physics produced the decade’s most closely watched near-misses. Between roughly 2014 and 2021, LHCb’s measurements of B -meson decays into muon pairs versus electron pairs — the “ R(K) ” and R() ratios that the Standard Model predicts should equal one if the model’s lepton universality holds — showed persistent tensions with that prediction, at one point reaching a statistical significance of 3.1 standard deviations and drawing serious theoretical attention as a possible sign of new particles coupling differently to muons than to electrons [ 7 ] . In December 2022, an improved, higher-statistics LHCb analysis brought the measured ratios back into agreement with the Standard Model…
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