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Register a new userHigher-order corrections to spin-spin scalar interactions in HD$^+$ and H$_2^+$
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The largest hyperfine interaction coefficients in the hydrogen molecular ion HD$^+$, i.e. the electron-proton and electron-deuteron spin-spin scalar interactions, are calculated with estimated uncertainties slightly below 1~ppm. The $(Zalpha)^2 E_F$ relativistic correction, for which a detailed derivation is presented, QED corrections up to the order $alpha^3 ln^2 (alpha)$ along with an estimate of higher-order terms, and nuclear structure corrections are taken into account. Improved results are also given for the electron-proton interaction coefficient in H$_2^+$, in excellent agreement with RF spectroscopy experiments. In HD$^+$, a 4$sigma$ difference is found in the hyperfine splitting of the $(v,L)=(0,3) to (9,3)$ two-photon transition that was recently measured with high precision. The origin of this discrepancy is unknown.
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A complete effective Hamiltonian for relativistic corrections at orders $malpha^6$ and $malpha^6(m/M)$ in a one-electron molecular system is derived from the NRQED Lagrangian. It includes spin-independent corrections to the energy levels and spin-spin scalar interactions contributing to the hyperfine splitting, both of which had been studied previously. In addition, corrections to electron spin-orbit and spin-spin tensor interactions are newly obtained. This allows improving the hyperfine structure theory in the hydrogen molecular ions. Improved values of the spin-orbit hyperfine coefficient are calculated for a few transitions of current experimental interest.
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We compute the inclusive jet spectrum in the presence of a dense QCD medium by going beyond the single parton energy loss approximation. We show that higher-order corrections are important yielding large logarithmic contributions that must be resummed to all orders. This reflects the fact that jet quenching is sensitive to fluctuations of the jet substructure.
I apply commonly used regularization schemes to a multi-loop calculation to examine the properties of the schemes at higher orders. I find complete consistency between the conventional dimensional regularization scheme and dimensional reduction, but I find that the four dimensional helicity scheme produces incorrect results at next-to-next-to-leading order and singular results at next-to-next-to-next-to-leading order. It is not, therefore, a unitary regularization scheme.
We report the results of a new search for long range spin-dependent interactions using a Rb -$^{21}$Ne atomic comagnetometer and a rotatable electron spin source based on a SmCo$_{5}$ magnet with an iron flux return. By looking for signal correlations with the orientation of the spin source we set new constrains on the product of the pseudoscalar electron and neutron couplings $g^e_p g^n_p/hbar c<1.7times10^{-14}$ and on the product of their axial couplings $g^e_A g^n_A/hbar c<5times10^{-42}$ to a new particle with a mass of less than about $1~mu$eV. Our measurements improve by about 2 orders of magnitude previous constraints on such spin-dependent interactions.
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