0000000001004641
AUTHOR
Matthias Heller
Leading order corrections to the Bethe-Heitler process in the $\gamma p\rightarrow l^+l^-p$ reaction
The ratio of di-lepton production cross sections on a proton, using the $\gamma p\rightarrow l^+ l^- p$ process, above and below di-muon production threshold allows to extract the effective lepton-proton interaction, which is required to be identical for electrons and muons if lepton universality is exact. To test for a scenario of broken universality at the percent level, of the size which could explain the different proton charge radii extracted from electron scattering and from muonic hydrogen spectroscopy, we evaluate all one-loop QED corrections to this process, including the full lepton mass dependencies. We furthermore show that two-photon exchange processes with both photons attache…
MultivariateApart: Generalized partial fractions
We present a package to perform partial fraction decompositions of multivariate rational functions. The algorithm allows to systematically avoid spurious denominator factors and is capable of producing unique results also when being applied to terms of a sum separately. The package is designed to work in Mathematica, but also provides interfaces to the Form and Singular computer algebra systems.
Multiple polylogarithms with algebraic arguments and the two-loop EW-QCD Drell-Yan master integrals
We consider Feynman integrals with algebraic leading singularities and total differentials in $\epsilon\,\mathrm{d}\ln$ form. We show for the first time that it is possible to evaluate integrals with singularities involving unrationalizable roots in terms of conventional multiple polylogarithms, by either parametric integration or matching the symbol. As our main application, we evaluate the two-loop master integrals relevant to the $\alpha \alpha_s$ corrections to Drell-Yan lepton pair production at hadron colliders. We optimize our functional basis to allow for fast and stable numerical evaluations in the physical region of phase space.
Soft-photon radiative corrections to the e−p→e−pl−l+ process
We calculate the leading-order QED radiative corrections to the process ${e}^{\ensuremath{-}}p\ensuremath{\rightarrow}{e}^{\ensuremath{-}}p{l}^{\ensuremath{-}}{l}^{+}$ in the soft-photon approximation, in two different energy regimes which are of relevance to extract nucleon structure information. In the low-energy region, this process is studied to better constrain the hadronic corrections to precision muonic hydrogen spectroscopy. In the high-energy region, the beam-spin asymmetry for double-virtual Compton scattering allows us to directly access the generalized parton distributions. We find that the soft-photon radiative corrections have a large impact on the cross sections and are there…
Soft-photon corrections to the Bethe-Heitler process in the γp→l+l−p reaction
We report on the calculation of first-order quantum electrodynamics (QED) corrections for the $\ensuremath{\gamma}p\ensuremath{\rightarrow}{l}^{+}{l}^{\ensuremath{-}}{p}^{\ensuremath{'}}$ process. An upcoming experiment at MAMI (Mainz) aims to compare the cross sections of muon- and electron-pair production in this reaction to test lepton universality. Precise knowledge of the electromagnetic radiative corrections is needed for these measurements. As a first step, we present the leading QED radiative corrections in the soft-photon approximation when accounting for the finite lepton mass. For the kinematics at MAMI, we find corrections of the percent level for muons, and of order 10% for ele…
Leading order corrections to the Bethe-Heitler process in the γp→l+l−p reaction
This paper focuses on all one-loop corrections to the Bethe-Heitler process involved in the reaction $\ensuremath{\gamma}\phantom{\rule{0}{0ex}}p\ensuremath{\rightarrow}{l}^{+}\phantom{\rule{0.333em}{0ex}}{l}^{\ensuremath{-}}\phantom{\rule{0}{0ex}}p$. These corrections are of paramount interest as they serve to check the exactness of the so called $l\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}p\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}n$ $u\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}v\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}r\phantom{\rule{0}{0ex}}s\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}l\phantom{\rule{0}{0ex}}i\phanto…
Leading-order QED radiative corrections to timelike Compton scattering on the proton
We evaluate the leading-order QED radiative corrections to the timelike Compton scattering (TCS) process $\gamma p \to l^- l^+ p$. We study these corrections in two energy regimes using different models for the TCS amplitude. In the low-energy regime we calculate the contribution due to the proton and its lowest-energy excitation, the $\Delta(1232)$ resonance. In the high-energy near-forward kinematical regime we calculate the TCS amplitude in a handbag approach in terms of Generalized Parton Distributions (GPDs). On the level of cross sections we find the QED radiative corrections to be in the $5 -10\%$ range in the low-energy regime and around $20\%$ in the high-energy regime. We show tha…
Leading order corrections to the Bethe-Heitler process in the γp→l+l−p reaction
The ratio of dilepton production cross sections on a proton, using the γp→l+l−p process, above and below the dimuon production threshold allows one to extract the effective lepton-proton interaction, which is required to be identical for electrons and muons if lepton universality is exact. To test for a scenario of broken universality at the percent level, of the size that could explain the different proton charge radii extracted from electron scattering and from muonic hydrogen spectroscopy, we evaluate all one-loop QED corrections to this process, including the full lepton mass dependencies. We furthermore show that two photon–exchange processes with both photons attached to the proton li…