63 research outputs found
Two-photon exchange correction to the hyperfine splitting in muonic hydrogen
We reevaluate the Zemach, recoil and polarizability corrections to the
hyperfine splitting in muonic hydrogen expressing them through the low-energy
proton structure constants and obtain the precise values of the Zemach radius
and two-photon exchange (TPE) contribution. The uncertainty of TPE correction
to S energy levels in muonic hydrogen of 105 ppm exceeds the ppm accuracy level
of the forthcoming 1S hyperfine splitting measurements at PSI, J-PARC and
RIKEN-RAL.Comment: 17 pages, 4 figures, version published in Eur. Phys. J. C, 77, no.
12, 858 (2017
Subtracted dispersion relation formalism for the two-photon exchange correction to elastic electron-proton scattering: comparison with data
We apply a subtracted dispersion relation formalism with the aim to improve
predictions for the two-photon exchange corrections to elastic electron-proton
scattering observables at finite momentum transfers. We study the formalism on
the elastic contribution, and make a detailed comparison with existing data for
unpolarized cross sections as well as polarization transfer observables.Comment: 49 pages, 26 figures, version published in Eur. Phys. J. A 51, no. 2,
24 (2015
Two-photon exchange correction to muon-proton elastic scattering at low momentum transfer
We evaluate the two-photon exchange (TPE) correction to the muon-proton
elastic scattering at small momentum transfer. Besides the elastic (nucleon)
intermediate state contribution, which is calculated exactly, we account for
the inelastic intermediate states by expressing the TPE process approximately
through the forward doubly virtual Compton scattering. The input in our
evaluation is given by the unpolarized proton structure functions and by one
subtraction function. For the latter, we provide an explicit evaluation based
on a Regge fit of high-energy proton structure function data. It is found that,
for the kinematics of the forthcoming muon-proton elastic scattering data of
the MUSE experiment, the elastic TPE contribution dominates, and the size of
the inelastic TPE contributions is within the anticipated error of the
forthcoming data.Comment: 33 pages, 15 figures, version published in Eur. Phys. J. C 76, no. 3,
125 (2016
Two-photon exchange contribution to elastic -proton scattering: Full dispersive treatment of states and comparison with data
We evaluate the two-photon exchange correction to the elastic electron-proton
scattering cross section within a dispersive framework. Besides the elastic
contribution, we account for all intermediate state contributions using
the phenomenological MAID fit as an input. We develop a novel method for the
analytical continuation of the two-photon exchange amplitudes into the
unphysical region and generalize our previous work to the momentum transfer
region . We
compare our results with recent OLYMPUS, CLAS and VEPP-3 data as well as with
empirical fits and estimates in the forward angular region.Comment: 43 pages, 21 figures, version published in Phys. Rev. D 96, 096001
(2017
Tau Neutrinos in the Next Decade: from GeV to EeV
Tau neutrinos are the least studied particle in the Standard Model. Thiswhitepaper discusses the current and expected upcoming status of tau neutrinophysics with attention to the broad experimental and theoretical landscapespanning long-baseline, beam-dump, collider, and astrophysical experiments.This whitepaper was prepared as a part of the NuTau2021 Workshop.<br
Scaled momentum distributions for K-S(0) and Λ /̄ Λ in DIS at HERA
Scaled momentum distributions for the strange hadrons K0S and Λ/Λ¯ were measured in deep inelastic ep scattering with the ZEUS detector at HERA using an integrated luminosity of 330 pb−1. The evolution of these distributions with the photon virtuality, Q 2, was studied in the kinematic region 10 < Q 2  < 40000 GeV2 and 0.001 < x < 0.75, where x is the Bjorken scaling variable. Clear scaling violations are observed. Predictions based on different approaches to fragmentation were compared to the measurements. Leading-logarithm parton-shower Monte Carlo calculations interfaced to the Lund string fragmentation model describe the data reasonably well in the whole range measured. Next-to-leading-order QCD calculations based on fragmentation functions, FFs, extracted from e + e − data alone, fail to describe the measurements. The calculations based on FFs extracted from a global analysis including e + e −, ep and pp data give an improved description. The measurements presented in this paper have the potential to further constrain the FFs of quarks, anti-quarks and gluons yielding K0S and Λ/Λ¯ strange hadrons
Fundamental Symmetries, Neutrons, and Neutrinos (FSNN): Whitepaper for the 2023 NSAC Long Range Plan
This whitepaper presents the research priorities decided on by attendees of
the 2022 Town Meeting for Fundamental Symmetries, Neutrons and Neutrinos, which
took place December 13-15, 2022 in Chapel Hill, NC, as part of the Nuclear
Science Advisory Committee (NSAC) 2023 Long Range Planning process. A total of
275 scientists registered for the meeting. The whitepaper makes a number of
explicit recommendations and justifies them in detail
- …