Related papers: Proton size anomaly
We obtain a model independent expression for the muonic hydrogen Lamb shift up to $\mathcal O (m_\mu \alpha^6, m_\mu \alpha^5 \frac{m_\mu^2}{m_\rho^2})$. The hadronic effects are controlled by the chiral theory, which allows for their model…
The recent measurement of the like-sign dimuon charge asymmetry in semileptonic b-hadron decays by the D0 Collaboration is about 3 sigmas away from the standard-model prediction, hinting at the presence of CP-violating new physics in the…
The very precise measurement of the anomalous magnetic moment of the muon, recently released by the Muon g-2 experiment at Fermilab, can serve to set stringent constraints on new particles. If the observed 4$\sigma$ discrepancy from the…
On the basis of recent precise measurements of the electric form factor of the proton, the Zemach moments, needed as input parameters for the determination of the proton rms radius from the measurement of the Lamb shift in muonic hydrogen,…
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…
A persistence of several anomalies in muon physics, such as the muon anomalous magnetic moment and the muonic hydrogen Lamb shift, hints at new light particles beyond the Standard Model. We address a subset of these models that have a new…
The charge radius of the deuteron (D), was recently determined to three times the precision compared with previous measurements using the measured Lamb shift in muonic deuterium (muD). However, the muD value is 5.6 $\sigma$ smaller than the…
The new measurement of the muon's anomalous magnetic moment released by the Muon g-2 experiment at Fermilab sets strong constraints on the properties of many new particles. Using an effective field theory approach to the interactions of…
We present a search for possible spin dependent interactions of the neutron with matter through exchange of spin 1 bosons with axial vector couplings as envisioned in possible extensions of the Standard Model. This was sought using a slow…
Light scalars can in principle couple to both bulk matter and fermion spin, with hierarchically disparate strengths. Storage ring measurements of fermion electromagnetic moments via spin precession can be sensitive to such a force, sourced…
(Abridged) Neutrino interactions beyond the standard model may affect the cosmological evolution and can be constrained through observations. We consider the possibility that neutrinos possess secret scalar or pseudoscalar interactions…
The leading-order contribution of a new boson to the muonic fine-structure anomaly, which refers to a discrepancy between the predicted transition energies and spectroscopic measurements of $\mu-^{90}$Zr, $\mu-^{120}$Sn, and $\mu-^{208}$Pb,…
We present a phenomenological constraint on a pseudovector light boson beyond the Standard Model, which can induce a long-range spin-dependent interaction $\alpha^{\prime\prime}({\bf s}_1\cdot{\bf s}_2)\,{\rm e}^{-\lambda r}/r$. In the…
We study the corrections induced by the theory of non-commutativity, in both space-space and space-time versions, on the spectrum of hydrogen-like atoms. For this, we use the relativistic theory of two-particle systems to take into account…
Since its inception, no decisive departure from the predictions of Standard Model (SM) has been reported. But recently various experiments have observed few hints of possible departure from SM predictions in lepton flavor universality…
The proton radius has been measured in electron-proton scattering experiments and laser based spectroscopy of muonic hydrogen. The latter method is based on the precise calculations for the atomic energy levels in the approximation of…
New unification theories predict Large Extra Dimensions (LEDs). If that is the case, gravity would be stronger at short ranges than what Newtonian gravity predicts. LEDs could also have effects at atomic level. In this paper we propose a…
The twenty years since the announcement of the proton spin crisis by the European Muon Collaboration has seen tremendous progress in our knowledge of the distribution of spin within the proton. The problem is reviewed, beginning with the…
We constrain the possibility of a new pseudoscalar coupling between the muon and proton using a recent measurement of the 2S hyperfine splitting in muonic hydrogen.
Agreement between theoretical calculations of atomic structure and spectroscopic measurements is used to constrain possible contribution of exotic spin-dependent interactions between electrons to the energy differences between states in…