scholarly journals Measurement of the running of the fine structure constant below 1 GeV with the KLOE detector

2019 ◽  
Vol 218 ◽  
pp. 02012
Author(s):  
Graziano Venanzoni
Keyword(s):  
Fine Structure ◽  
Energy Region ◽  
Direct Evidence ◽  
Branching Ratio ◽  
Structure Constant ◽  
Fine Structure Constant ◽  
Recent Measurement ◽  
Single Measurement ◽  
Lepton Universality ◽  
Hadronic Contribution

I will report on the recent measurement of the fine structure constant below 1 GeV with the KLOE detector. It represents the first measurement of the running of α(s) in this energy region. Our results show a more than 5σ significance of the hadronic contribution to the running of α(s), which is the strongest direct evidence both in time-and space-like regions achieved in a single measurement. From a fit of the real part of Δα(s) and assuming the lepton universality the branching ratio BR(ω → µ+µ−) = (6.6 ± 1.4stat ± 1.7syst) · 10−5 has been determined

Precision measurements of fine and hyperfine structure in lithium I and II

2005 ◽  
Vol 83 (4) ◽  
pp. 327-337 ◽  
Author(s):  
W A van Wijngaarden
Keyword(s):  
Fine Structure ◽  
Quantum Electrodynamics ◽  
Nuclear Charge ◽  
Structure Constant ◽  
Precision Measurements ◽  
Fine Structure Constant ◽  
Recent Measurement ◽  
Charge Radii ◽  
Fine And Hyperfine Structure

Recent advances in modeling Li I and II in conjunction with improved experimental techniques have enabled precise tests of quantum electrodynamics. For Li+, the hyperfine intervals of the 1s2s 3S1 and 1s2p 3P0,1,2 states are in excellent agreement with theory. A recent measurement of the 1s2p 3P1,2 fine-structure interval also agrees well with the calculated value and resolves a discrepancy found by two prior experiments. For neutral lithium, discrepancies exist among the results of various experiments for the 6,7Li D1 isotope shift and the 2P fine structure. However, all of the fine-structure measurements are several MHz larger than the theoretical value. Prospects for future experiments to improve the determination of the fine-structure constant and the relative 6,7Li nuclear charge radii are discussed. PACS Nos.: 32.10.Fn, 31.30.Gs, 42.62.Fi

scholarly journals New Limit on Space-Time Variations in the Proton-to-Electron Mass Ratio from Analysis of Quasar J110325-264515 Spectra

Symmetry ◽  
2020 ◽  
Vol 12 (3) ◽  
pp. 344
Author(s):  
T. D. Le
Keyword(s):  
Fine Structure ◽  
Structure Constant ◽  
Space Time ◽  
Fine Structure Constant ◽  
Electron Mass ◽  
Mass Ratio ◽  
Quasar Spectra ◽  
Time Variations ◽  
Using Data ◽  
The Universe

Astrophysical tests of current values for dimensionless constants known on Earth, such as the fine-structure constant, α , and proton-to-electron mass ratio, μ = m p / m e , are communicated using data from high-resolution quasar spectra in different regions or epochs of the universe. The symmetry wavelengths of [Fe II] lines from redshifted quasar spectra of J110325-264515 and their corresponding values in the laboratory were combined to find a new limit on space-time variations in the proton-to-electron mass ratio, ∆ μ / μ = ( 0.096 ± 0.182 ) × 10 − 7 . The results show how the indicated astrophysical observations can further improve the accuracy and space-time variations of physics constants.

scholarly journals Fine structure constant and the CMB damping scale

2012 ◽  
Vol 85 (10) ◽  
Author(s):  
Eloisa Menegoni ◽  
Maria Archidiacono ◽  
Erminia Calabrese ◽  
Silvia Galli ◽  
C. J. A. P. Martins ◽  
...  
Keyword(s):  
Fine Structure ◽  
Structure Constant ◽  
Fine Structure Constant

CONSTRAINTS ON SPATIAL VARIATIONS IN THE FINE-STRUCTURE CONSTANT FROMPLANCK

2014 ◽  
Vol 798 (1) ◽  
pp. 18 ◽  
Author(s):  
Jon O'Bryan ◽  
Joseph Smidt ◽  
Francesco De Bernardis ◽  
Asantha Cooray
Keyword(s):  
Fine Structure ◽  
Structure Constant ◽  
Spatial Variations ◽  
Fine Structure Constant

PHASE TRANSITIONS IN STRONG COUPLING QED4[N]

1992 ◽  
Vol 07 (30) ◽  
pp. 7629-7646 ◽  
Author(s):  
D. ATKINSON ◽  
H.J. DE GROOT ◽  
P.W. JOHNSON
Keyword(s):  
Phase Transition ◽  
Fixed Point ◽  
Fine Structure ◽  
Mean Field ◽  
Structure Constant ◽  
Fine Structure Constant ◽  
Massless Fermion ◽  
Charge Renormalization ◽  
Dynamical Breaking ◽  
Proper Account

We analyze coupled Dyson-Schwinger equations for massless fermion and photon propagators in QED4[N], taking proper account of charge renormalization. With one fermion flavor, we find a fixed point at an ultraviolet “fine-structure constant” of 2.10, corresponding to a phase transition (associated with the dynamical breaking of chiral symmetry) of mean-field type.

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