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Register a new userLimits on light-speed anisotropies from Compton scattering of high-energy electrons
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The possibility of anisotropies in the speed of light relative to the limiting speed of electrons is considered. The absence of sidereal variations in the energy of Compton-edge photons at the ESRFs GRAAL facility constrains such anisotropies representing the first non-threshold collision-kinematics study of Lorentz violation. When interpreted within the minimal Standard-Model Extension, this result yields the two-sided limit of 1.6 x 10^{-14} at 95% confidence level on a combination of the parity-violating photon and electron coefficients kappa_{o+} and c. This new constraint provides an improvement over previous bounds by one order of magnitude.
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Based on the high sensitivity of Compton scattering off ultra relativistic electrons, the possibility of anisotropies in the speed of light is investigated. The result discussed in this contribution is based on the gamma-ray beam of the ESRFs GRAAL facility (Grenoble, France) and the search for sidereal variations in the energy of the Compton-edge photons. The absence of oscillations yields the two-sided limit of 1.6 x 10^{-14} at 95 % confidence level on a combination of photon and electron coefficients of the minimal Standard Model Extension (mSME). This new constraint provides an improvement over previous bounds by one order of magnitude.
The high-precision HERA data allows searches up to TeV scales for Beyond the Standard Model contributions to electron-quark scattering. Combined measurements of the inclusive deep inelastic cross sections in neutral and charged current $ep$ scattering corresponding to a luminosity of around 1 fb$^{-1}$ have been used in this analysis. A new approach to the beyond the Standard Model analysis of the inclusive $ep$ data is presented; simultaneous fits of parton distribution functions together with contributions of new physics processes were performed. Results are presented considering a finite radius of quarks within the quark form-factor model. The resulting 95% C.L. upper limit on the effective quark radius is $0.43cdot 10^{-16}$ cm.
This executive summary of recent theory progress in Compton scattering off 3He focuses on determining neutron polarisabilities; see ref. [2] and references therein for details and a better bibliography. Prepared for the Proceedings of the 22nd International Conference on Few-Body Problems in Physics, Caen 9-13 July 2018.
The energy measurement uncertainty of circular electron positron collider (CEPC) beam must be less than $10 mathrm{MeV}$ to accurately measure the mass of the Higgs/W/Z boson. A new microwave-beam Compton backscattering method is proposed to measure the beam energy by detecting the maximum energy of scattered photons. The uncertainty of the beam energy measurement is $6 mathrm{MeV}$. The detection accuracy of the maximum energy of scattered photons need to reach $10^{-4}$. The high-precision gamma detectors can only be a high-purity germanium (HPGe) detector. It is a semiconductor detector, the effective detection range of the gamma energy is 100$mathrm{keV}$-10$mathrm{MeV}$. The maximum energy of the scattered photons is chosen to be the higher the better to reduce the influence of the synchrotron radiation background. Therefore, the maximum energy of the scattered photons is selected to be 9$mathrm{MeV}$. Therefore, the initial photons should be microwave photons to collide with the electrons with the energy of 120GeV on CEPC. The cylindrical resonant cavity with ${TM_{010}}$ mode is selected to transmit microwaves. After Compton backscattering, the scattered photons emit from the vacuum tube of the synchrotron radiation and the energy is detected by the HPGe detector. The structure of shielding materials with polyethylene and lead is designed to minimize the background noise, such as the synchrotron radiation and the classical radiation from the electron beam in the cavity. The hole radius in the side wall of the cavity is about $1.5mathrm{mm}$ to allow the electron beam to pass through. The computer simulation technology (CST) software shows that the influence of the hole radius on the cavity field is negligible, and the influence of the hole radius on the resonance frequency can be corrected easily.
Experimental bounds on induced vacuum magnetic birefringence can be used to improve present photon-photon scattering limits in the electronvolt energy range. Measurements with the PVLAS apparatus (E. Zavattini {it et al.}, Phys. Rev. D {bf77} (2008) 032006) at both $lambda = 1064$ nm and 532 nm lead to bounds on the parameter {it A$_{e}$}, describing non linear effects in QED, of $A_{e}^{(1064)} < 6.6cdot10^{-21}$ T$^{-2}$ @ 1064 nm and $A_{e}^{(532)} < 6.3cdot10^{-21}$ T$^{-2}$ @ 532 nm, respectively, at 95% confidence level, compared to the predicted value of $A_{e}=1.32cdot10^{-24}$ T$^{-2}$. The total photon-photon scattering cross section may also be expressed in terms of $A_e$, setting bounds for unpolarized light of $sigma_{gammagamma}^{(1064)} < 4.6cdot10^{-62}$ m$^{2}$ and $sigma_{gammagamma}^{(532)} < 2.7cdot10^{-60}$ m$^{2}$. Compared to the expected QED scattering cross section these results are a factor of $simeq2cdot10^{7}$ higher and represent an improvement of a factor about 500 on previous bounds based on ellipticity measurements and of a factor of about $10^{10}$ on bounds based on direct stimulated scattering measurements.
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