scholarly journals A test of local Lorentz invariance with Compton scattering asymmetry

2016 ◽  
Vol 31 (38) ◽  
pp. 1650220 ◽  
Author(s):  
Prajwal Mohanmurthy ◽  
Amrendra Narayan ◽  
Dipangkar Dutta
Keyword(s):  
Refractive Index ◽  
Standard Model ◽  
Compton Scattering ◽  
Electron Scattering ◽  
Lorentz Invariance ◽  
Speed Of Light ◽  
Standard Model Extension ◽  
Model Extension ◽  
Minimal Standard ◽  
Local Lorentz Invariance

We report on a measurement of the constancy and anisotropy of the speed of light relative to the electrons in photon–electron scattering. We used the Compton scattering asymmetry measured by the new Compton polarimeter in Hall C at Jefferson Lab (JLab) to test for deviations from unity of the vacuum refractive index (n). For photon energies in the range of 9–46 MeV, we obtain a new limit of 1 − n < 1.4 × 10[Formula: see text]. In addition, the absence of sidereal variation over the six-month period of the measurement constrains any anisotropies in the speed of light. These constitute the first study of Lorentz invariance (LI) using Compton asymmetry. Within the minimal Standard Model extension (MSME) framework, our result yield limits on the photon and electron coefficients [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text]. Although these limits are several orders of magnitude larger than the current best limits, they demonstrate the feasibility of using Compton asymmetry for tests of LI. Future parity-violating electron-scattering experiments at JLab will use higher energy electrons enabling better constraints.

scholarly journals Lorentz Violation of the Photon Sector in Field Theory Models

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Lingli Zhou ◽  
Bo-Qiang Ma
Keyword(s):  
Field Theory ◽  
Standard Model ◽  
Degrees Of Freedom ◽  
Lorentz Violation ◽  
Detailed Structure ◽  
Standard Model Extension ◽  
Model Extension ◽  
The Standard Model ◽  
Minimal Standard

We compare the Lorentz violation terms of the pure photon sector between two field theory models, namely, the minimal standard model extension (SME) and the standard model supplement (SMS). From the requirement of the identity of the intersection for the two models, we find that the free photon sector of the SMS can be a subset of the photon sector of the minimal SME. We not only obtain some relations between the SME parameters but also get some constraints on the SMS parameters from the SME parameters. The CPT-odd coefficients(kAF)αof the SME are predicted to be zero. There are 15 degrees of freedom in the Lorentz violation matrixΔαβof free photons of the SMS related with the same number of degrees of freedom in the tensor coefficients(kF)αβμν, which are independent from each other in the minimal SME but are interrelated in the intersection of the SMS and the minimal SME. With the related degrees of freedom, we obtain the conservative constraints(2σ)on the elements of the photon Lorentz violation matrix. The detailed structure of the photon Lorentz violation matrix suggests some applications to the Lorentz violation experiments for photons.

scholarly journals One-loop nonbirefringent effects on the electromagnetic vertex in the Standard Model Extension

2014 ◽  
Vol 29 (22) ◽  
pp. 1450107 ◽  
Author(s):  
A. Moyotl ◽  
H. Novales-Sanchez ◽  
J. J. Toscano ◽  
E. S. Tututi
Keyword(s):  
Standard Model ◽  
Lorentz Invariance ◽  
Lorentz Violation ◽  
Tree Level ◽  
Isotropic Case ◽  
Photon Propagator ◽  
Standard Model Extension ◽  
Model Extension ◽  
The One ◽  
Electromagnetic Vertex

Lorentz violation emerged from a fundamental description of nature may impact, at low energies, the Maxwell sector, so that contributions from such new physics to the electromagnetic vertex would be induced. Particularly, nonbirefringent CPT-even effects from the electromagnetic sector modified by the Lorentz- and CPT-violating Standard Model Extension alter the structure of the free photon propagator. We calculate Lorentz-violating contributions to the electromagnetic vertex, at the one-loop level, by using a modified photon propagator carrying this sort of effects. We take the photon off shell, and find an expression that involves both isotropic and anisotropic effects of nonbirefringent violation of Lorentz invariance. Our analysis of the one-loop vertex function includes gauge invariance, transformation properties under C, P and T, and tree-level contributions from Lorentz-violating nonrenormalizable interactions. These elements add to previous studies of the one-loop contributions to the electromagnetic vertex in the context of Lorentz violation in the photon sector. Finally, we restrict our analysis to the isotropic case and derive a finite contribution from isotropic Lorentz violation to the anomalous magnetic moment of fermions that coincides with the result already reported in the literature.

scholarly journals Constraints on the standard model extension with binary pulsars

2012 ◽  
Vol 8 (S291) ◽  
pp. 558-560
Author(s):  
Yi Xie
Keyword(s):  
Standard Model ◽  
Lorentz Invariance ◽  
Standard Model Extension ◽  
Binary Pulsars ◽  
Model Extension ◽  
The Standard Model ◽  
Order Of Magnitude ◽  
Dimensionless Combination

AbstractUnder the standard model extension (SME) framework, Lorentz invariance is tested in five binary pulsars: PSR J0737-3039, PSR B1534+12, PSR J1756-2251, PSR B1913+16 and PSR B2127+11C. By analyzing the advance of periastron, we obtain the constraints on a dimensionless combination of SME parameters that is sensitive to timing observations. The results imply no evidence for the break of Lorentz invariance at 10−10 level, one order of magnitude larger than previous estimation.

scholarly journals SUPERLUMINAL NEUTRINOS IN THE MINIMAL STANDARD MODEL EXTENSION

2012 ◽  
Vol 27 (09) ◽  
pp. 1250045 ◽  
Author(s):  
NAN QIN ◽  
BO-QIANG MA
Keyword(s):  
Standard Model ◽  
Energy Relation ◽  
Muon Neutrinos ◽  
Standard Model Extension ◽  
Modified Dispersion Relation ◽  
Long Baseline ◽  
Model Extension ◽  
Modern Physics ◽  
Minimal Standard ◽  
Basic Hypothesis

The measurement of the neutrino velocity with the OPERA detector in the CNGS beam shows unexpected indication, that the muon neutrino velocity, vν, exceeds the velocity of light in the vacuum, c, which is obviously in contradiction with the most basic hypothesis of modern physics. Within the framework of minimal Standard Model Extension (SME), we discuss the modified dispersion relation and consequently the velocity–energy relation of muon neutrinos. The simplified models are fitted to the OPERA data, Fermilab experiment and MINOS data. We find that minimal Standard Model Extension can describe these long baseline superluminal neutrinos to a good accuracy. For the well-known tension between the OPERA measurement and the Supernova 1987A neutrino observation, we discuss two ways out of the contradiction.

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