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Radiatively generated isospin violations in the nucleon and the NuTeV anomaly.
M Glück1, P Jimenez-Delgado, E Reya
1Institut für Physik, Universität Dortmund, D-44221 Dortmund, Germany.
Physical Review Letters
|August 11, 2005
Summary
Quantum Electrodynamics (QED) photon bremsstrahlung effects explain isospin asymmetries in particle distributions. This resolves the NuTeV anomaly discrepancy in sin(2Theta(w)) measurements when combined with hadronic sources and strangeness asymmetry.
Area of Science:
- Particle Physics
- Quantum Field Theory
- Nuclear Physics
Background:
- The NuTeV experiment reported a significant discrepancy in the measurement of sin(2Theta(w)) compared to the world average.
- Isospin symmetry is a fundamental concept in nuclear and particle physics, but it can be violated by various effects.
Purpose of the Study:
- To investigate the role of QED leading O(alpha) photon bremsstrahlung effects in generating isospin asymmetries.
- To reconcile the NuTeV anomaly by accounting for both QED and nonperturbative hadronic contributions to isospin violation.
Main Methods:
- Calculations of isospin asymmetries in valence and sea quark distributions.
- Inclusion of nonperturbative hadronic sources like quark and target mass differences.
- Incorporation of a strangeness asymmetry (s != sbar) contribution.
Main Results:
- QED leading O(alpha) photon bremsstrahlung effects predict significant isospin asymmetries.
- Combining these QED effects with hadronic sources and strangeness asymmetry successfully removes the discrepancy observed in the NuTeV sin(2Theta(w)) measurement.
Conclusions:
- QED effects play a crucial role in understanding isospin asymmetries in particle distributions.
- The NuTeV anomaly can be explained by a combination of QED, hadronic, and strangeness asymmetry contributions.