Search for Violation of Time-Reversal Invariance in Inelastic<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>e</mml:mi><mml:mo>−</mml:mo><mml:mi>p</mml:mi></mml:math>Scattering

Appel, J. A.; Chen, J. R.; Sanderson, J.; Gladding, G.; Goitein, Michael; Hanson, K.; Imrie, D. C.; Kirk, T.; Madaras, R. J.; Pound, R. V.; Price, L. E.; Wilson, Richard; Zajde, C.

doi:10.1103/physrevd.1.1285

Cited by 17 publications

(5 citation statements)

References 22 publications

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“…Previous measurements of A n with electron scattering have either been made with inelastic scattering [8,9,10,11,12] searching for T -violation, or in quasielastic scattering from polarized 3 He [13]. There are currently no published results from elastic electron scattering from polarized hydrogen.…”

Section: Previous Measurementsmentioning

confidence: 99%

Target-Normal Single Spin Asymmetries Measured with Positrons

Grauvogel,

Kutz,

Schmidt

2021

Preprint

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Two-photon exchange and the larger class of hadronic box diagrams are difficult to calculate without a large degree of model-dependence. At the same time, these processes are significant radiative corrections in parity-violating electron scattering, in neutron decay, and may even be responsible for the proton's form factor ratio discrepancy. New kinds of experimental data are needed to help constrain models and guide future box-diagram calculations. The target-normal single spin asymmetry, A n , formed with an unpolarized beam scattering from a target that is polarized normal to the scattering plane, is sensitive to the imaginary part of the two-photon exchange amplitude, and can provide a valuable constraint. A measurement with both electrons and positrons can reduce sources of experimental error, and distinguish between the effects of two-photon exchange and those of time-reversal symmetry violation. This article describes a proposed experiment in Hall A, using the new Super Big-Bite Spectrometer that can cover a momentum transfer range in the critical zone of uncertainty between where hadronic calculations and those based on partonic degrees of freedom are expected to be accurate.Keywords two-photon exchange • positrons • singlespin asymmetries • polarized target

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Section: Previous Measurementsmentioning

confidence: 99%

Target-Normal Single Spin Asymmetries Measured with Positrons

Grauvogel,

Kutz,

Schmidt

2021

Preprint

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“…Since this is also a unique combination of new form factors, a measurement of A n would provide new constraints on TPE. Previous measurements of A n with electron scattering have either been made with inelastic scattering [35][36][37][38][39], or in quasielastic scattering from polarized 3 He [40]. There are currently no published results from elastic electron scattering from polarized hydrogen.…”

Section: Target-normal Single Spin Asymmetriesmentioning

confidence: 99%

Polarization observables using positron beams

Schmidt¹

2018

AIP Conference Proceedings

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The discrepancy between polarized and unpolarized measurements of the proton's electromagnetic form factors is striking, and suggests that two-photon exchange (TPE) may be playing a larger role in elastic electron-proton scattering than is estimated in standard radiative corrections formulae. While TPE is difficult to calculate in a model-independent way, it can be determined experimentally from asymmetries between electron-proton and positron-proton scattering. The possibility of a polarized positron beam at Jefferson Lab would open the door to measurements of TPE using polarization observables. In these proceedings, I examine the feasibility of measuring three such observables with positron scattering. Polarization-transfer, specifically the -dependence for fixed Q 2 , is an excellent test of TPE, and the ability to compare electrons and positrons would lead to a drastic reduction of systematics. However, such a measurement would be severely statistically limited. Normal single-spin asymmetries (SSAs) probe the imaginary part of the TPE amplitude and can be improved by simultaneous measurements with electron and positron beams. Beam-normal SSAs are too small to be measured with the proposed polarized positron beam, but target-normal SSAs could be feasibly measured with unpolarized positrons in the spectrometer halls. This technique should be included in the physics case for developing a positron source for Jefferson Lab.

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“…Up to now, experimental searches have been mainly performed in elastic lepton-nucleon scattering, where non-zero transverse-beam SSAs of order 10 −5 − 10 −6 have been measured [4]. In inelastic scattering, no clear indication of two-photon exchange has yet been observed, where various attemps of measuring both transverse-target SSAs [6,7,8] and cross-section ratio [9,10,11,12,13,14,15] show no effect within the few-percent level. No experimental search has been done in deep-inelastic scattering (DIS) to date.…”

Section: Introductionmentioning

confidence: 99%

Search for a Two-Photon Exchange Contribution in inclusive DIS at sc hermes

Ruiz¹

2009

Proceedings of the XVII International Workshop on Deep-Inelastic Scattering and Related Topics

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The transverse-target single-spin asymmetry for inclusive deep-inelastic scattering with effectively unpolarized electron and positron beams off a transversely polarized hydrogen target was measured, with the goal of searching for a two-photon exchange signal in the kinematic range 0.004 < x < 0.9 and 0.1 GeV 2 < Q 2 < 20 GeV 2. In two separate regions Q 2 > 1 GeV 2 and Q 2 < 1 GeV 2 , and for both electron and positron beams, the asymmetries are found to be consistent with zero within statistical and systematic uncertainties, which are of order 10 −3 for the overall asymmetries.

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Search for Violation of Time-Reversal Invariance in Inelastice−pScattering

Cited by 17 publications

References 22 publications

Target-Normal Single Spin Asymmetries Measured with Positrons

Target-Normal Single Spin Asymmetries Measured with Positrons

Polarization observables using positron beams

Search for a Two-Photon Exchange Contribution in inclusive DIS at sc hermes

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