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Wayne W. Repko

Publications and source records attributed to Wayne W. Repko.

At least 19 recordsLinked to original sources
arXiv2019

Vacuum polarization corrections to the $n=2$ and $n=3$ levels in muonic $^4$He

The $n=2$ and $n=3$ levels for muonic Helium are calculated using a potential that includes all one-loop and recoil effects. Electronic vacuum polarization corrections are calculated using an extension of Kinoshita and Nio method. For $n=2$, the results are $2p_{1/2}-2s_{1/2}=1375.05\pm 1.4$ meV and $2p_{3/2}-2s_{1/2}=1521.65\pm 1.4$ meV, essentially in agreement with the latest summary of the current calculations. The $n=3$ results are summarized in tabular form and give $3p_{1/2}-3s_{1/2}=394.76\pm 0.43$ meV and $3d_{3/2}-3p_{3/2}=111.40$ meV.

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arXiv2018

Vacuum polarization corrections to $\mu^+\mu^-$ spectrum

The energy levels of the $n=1$ and $n=2$ bound states of the $\mu^+\mu^-$ atom (true muonium) are calculated starting from a previously derived potential that correctly describes positronium to order $\alpha^5$ supplemented by the known $\alpha^6$ contributions. All electron vacuum polarization corrections on the true muonium levels are computed to order $\alpha^6$ order. The second order perturbative contributions from all of the $\alpha^4$ and $\alpha^5$ terms in the potential are also included. Additional order $\alpha^6$ contributions from the two photon and three photon annihilation processes are included in the evaluation of the ground state ($1^3S_1-1^1S_0$) hyperfine splitting.

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arXiv2017

Muonic hydrogen and the proton size

We reexamine the structure of the $n=2$ levels of muonic hydrogen using a two-body potential that includes all relativistic, recoil and one loop corrections. The potential was originally derived from QED to describe the muonium atom and accounts for all contributions to order $\alpha^5$. Since one loop corrections are included, the anomalous magnetic moment contributions of the muon can be identified and replaced by the proton anomalous magnetic moment to describe muonic hydrogen with a point-like proton. This serves as a convenient starting point to include the dominant electron vacuum polarization corrections to the spectrum and extract the proton's mean squared radius $r_p=\sqrt{\langle r^2\rangle}$. Our results are consistent with other theoretical calculations that find that the muonic hydrogen value for $r_p$ is smaller than the result obtained from electron scattering.

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arXiv2016

Note on predictions for $c\bar{s}$ quarkonia using a three-loop static potential

We extend our treatment of the the spectroscopy and decays of the charm-strange quarkonium system to include the effect of using the full three-loop QCD correction to the static short distance potential. As before, our potential model consists of the relativistic kinetic energy term, a scalar linear confining term including its relativistic corrections and the perturbative QCD spin-dependent terms. A set of unperturbed wave functions for the various states is obtained using a variational technique that is further constrained by requiring that the wave functions also satisfy the relativistic virial theorem. These are then used in a perturbative treatment of the potential to fit the mass spectrum of the $c\bar{s}$ system and calculate the radiative decay widths. Our results accurately describe the $D_s$ spectrum and are compatible with the little data that is available for the radiative decays of the $D_s$ states.

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arXiv2015

Interference effects and the use of Higgs boson pair production to study the Higgs trilinear self coupling

We show that the dominant channel proposed for the determination of the Higgs boson trilinear coupling, $pp\to HH+X$ via gluon fusion, exhibits an interference structure that is independent of the collider energy for collider energies in the range $8\,{\rm TeV}\leq \sqrt{s}\leq 100\,{\rm TeV}$ and is almost maximally destructive. This insensitivity to the collider energy remains approximately true for a variety of other two Higgs production mechanisms although the magnitude of the interference varies widely.

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arXiv2014

Residual Symmetries Applied to Neutrino Oscillations at NO$ν$A and T2K

The results previously obtained from the model-independent application of a generalized hidden horizontal $\mathbb{Z}_2$ symmetry to the neutrino mass matrix are updated using the latest global fits for the neutrino oscillation parameters. The resulting prediction for the Dirac $CP$ phase $δ_D$ is in agreement with recent results from T2K. The distribution for the Jarlskog invariant $J_ν$ has become sharper and appears to be approaching a particular region. The approximate effects of matter on long baseline neutrino experiments are explored, and it is shown how the weak interactions between the neutrinos and the particles that make up the Earth can help to determine the mass hierarchy. A similar strategy is employed to show how NO$ν$A and T2K could determine the octant of $θ_a (\equiv θ_{23})$. Finally, the exact effects of matter are obtained numerically in order to make comparisons with the form of the approximate solutions. From this analysis there emerges some interesting features of the effective mass eigenvalues.

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arXiv2014

Dalitz Decay $H\to\,f\bar{f}γ$ as a Background for $H\toγ\,γ$

The Dalitz decay $H\to\,f\bar{f}γ$ is calculated for very small $f\bar{f}$ invariant masses where the $f\bar{f}$ pair could be mistaken for a photon in analysis of $H\toγγ$ decays. Using the ATLAS cuts and the full Dalitz decay amplitude, we estimate this fraction to be 7.06%.

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arXiv2013

Comparison of $H\to\ell\bar{\ell}γ$ and $H\toγ\,Z, Z\to\ell\bar{\ell}$ including the ATLAS cuts

A precise comparison is made between the Dalitz decay $H\to\ell\bar{\ell}γ$ and the two body decay $H\toγZ,Z\to\ell\bar{\ell}$ for electrons and for muons including experimental cuts appropriate for the ATLAS detector. The widths for these two processes differ by 8% for electrons and 3% for muons. Given that there remain QCD radiative corrections of this order that are not included, this suggests that the isolation of the Dalitz decay will be challenging.

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arXiv2013

Phenomenological Study of Residual Z^s_2 and Zbar^s_2 Symmetries

The phenomenological consequences of the residual Z^s_2 and Zbar^s_2 symmetries are explored in detail. With a precisely measured value of the reactor angle, these two residual symmetries predict distinct distributions for the Dirac CP phase and the atmospheric angle, which leads to the possibility of identifying them at neutrino experiments. For both symmetries, it is possible to resolve the neutrino mass hierarchy in most of the parameter space, and they can be distinguished from one another if the true residual symmetry is Z^s_2 and the atmospheric angle is non-maximal. These results are obtained using an equally split schedule: a 1.5-year run of neutrinos and a 1.5-year run of antineutrinos at NOvA together with a 2.5-year run of neutrinos and a 2.5-year run of antineutrinos at T2K. This schedule can significantly increase and stabilize the sensitivities to the mass hierarchy and the octant of the atmospheric angle with only a moderate compromise to the sensitivity of distinguishing Z^s_2 and Zbar^s_2.

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arXiv2013

Three-loop Static QCD Potential in Heavy Quarkonia

We investigate the effects of including the full three-loop QCD correction to the static short distance $1/r$ potential on the spectroscopy and decays in the charmonium and upsilon systems. We use a variational technique with the full three-loop corrected potential to determine a set of unperturbed trial wave functions and treat the relativistic and one-loop corrections as perturbations. The perturbed results are compared to the subset of the charmonium and upsilon spectra using a $χ^2$ test. This approach results in more accurate descriptions of the hyperfine splittings in both the $b\bar{b}$ and $c\bar{c}$ systems.

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arXiv2012

Potential model results for the newly discovered chi_b(3P) states

The ATLAS Collaboration has recently announced the discovery of the 3P states of the Upsilon system, chi_b(3P), with mass of 10.539+-0.004(stat.)+-0.008(syst.) GeV. In a previous investigation of the Upsilon system, in the context of a comprehensive one-loop potential model, we calculated the masses of these states, but did not include them. We present those results, and others for the n = 3 states here.

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arXiv2011

Residual Symmetries for Neutrino Mixing with a Large theta_13 and Nearly Maximal delta_D

The residual Z^s_2(k) and bar Z^s_2(k) symmetries induce a direct and unique phenomenological relation with theta_x (= theta_13) expressed in terms of the other two mixing angles, theta_s (= theta_12) and theta_a (= theta_23), and the Dirac CP phase delta_D. Z^s_2(k) predicts a theta_x probability distribution centered around 3^o ~ 6^o with an uncertainty of 2^o to 4^o while those from bar Z^s_2(k) are approximately a factor of two larger. Either result fits the T2K, MINOS and Double CHOOZ measurements. Alternately a prediction for the Dirac CP phase delta_D results in a peak at +-74^o (+-106^o) for Z^s_2(k) or +-123^o (+-57^o) for bar Z^s_2(k) which is consistent with the latest global fit. We also give a distribution for the leptonic Jarslkog invariant J_v which can provide further tests from measurements at T2K and NOvA.

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arXiv2011

Z_2 Symmetry Prediction for the Leptonic Dirac CP Phase

Model-independent consequences of applying a generalized hidden horizontal Z_2 symmetry to the neutrino mass matrix are explored. The Dirac CP phase delta_D can be expressed in terms of the three mixing angles as 4 c_a s_a c_s s_s s_x cos delta_D = (s^2_s - c^2_s s^2_x) (c^2_a - s^2_a) where the s_i, c_i are sines and cosines of the atmospheric, solar, and reactor angles. This relation is independent of neutrino masses and whether neutrinos are Dirac- or Majorana-type. Given the present constraints on the angles, delta_D is constrained to be almost maximal, a result which can be explored in experiments such as NOvA and T2K. The Majorana CP phases do not receive any constraint and are thus model-dependent. Also a distribution of theta_x with a lower limit is obtained without specifying delta_D.

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