The initial state radiation experiment at MAMI

Mihovilovič, M.; Merkel, H.; Weber, A.

doi:10.22323/1.212.0051

Cited by 3 publications

(3 citation statements)

References 4 publications

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“…An experiment at MAMI is underway, aimed at measuring proton form-factors at very low momentum transfers by using a technique based on initial state radiation (ISR) [99]. The idea is that ISR, Fig.…”

Section: Isr Form Factor Measurementsmentioning

confidence: 99%

The proton radius puzzle

Carlson

2015

Progress in Particle and Nuclear Physics

252

164

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The proton size, specifically its charge radius, was thought known to about 1% accuracy. Now a new method probing the proton with muons instead of electrons finds a radius about 4% smaller, and to boot gives an uncertainty limit of about 0.1%. We review the different measurements, some of the calculations that underlie them, some of the suggestions that have been made to resolve the conflict, and give a brief overview new related experimental initiatives. At present, however, the resolution to the problem remains unknown.

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Section: Isr Form Factor Measurementsmentioning

confidence: 99%

The proton radius puzzle

Carlson

2015

Progress in Particle and Nuclear Physics

252

164

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“…• Initial state radiation at MAMI, A1 collaboration [46]: Making use of the initial state radiation techniques, where the initial electron momentum is degraded by photon emission, the momentum transfer to the proton is reduced. The scattered electron is measured with the usual spectrometers but no information on the photon is observed.…”

Section: Scattering Experimentsmentioning

confidence: 99%

Experiments towards resolving the proton charge radius puzzle

Antognini

Schuhmann

Amaro

et al. 2016

EPJ Web of Conferences

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Abstract.We review the status of the proton charge radius puzzle. Emphasis is given to the various experiments initiated to resolve the conflict between the muonic hydrogen results and the results from scattering and regular hydrogen spectroscopy. The proton charge radius puzzleThe historical route to the proton charge radius (r p ) is from elastic electron-proton scattering. In a completely complementary fashion, it has been obtained also from "high-precision" laser spectroscopy of hydrogen (H). Since a few years, "high-sensitivity" laser spectroscopy of muonic hydrogen (μp) offers a third way. The value extracted from μp with a relative accuracy of 5×10 −4 is an order of magnitude more accurate than obtained from the other methods. Yet the value is 4% smaller than derived from electron-proton scattering and H spectroscopy with a disagreement at the 7σ level [1][2][3][4][5].In the last five years as summarized in [6,7] various cross checks and refinements of boundstate QED calculations needed for the extraction of r p from μp have been performed, together with investigations of the proton structure. Several suggestions in the field of "beyond standard model" BSM physics have been articulated, re-analysis of scattering data have been carried out and new experiments have been initiated. Despite this, presently the discrepancy still persists and the resolution a

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“…As described earlier, the extrapolation to Q 2 = 0 is critical. Using initial state radiation to lower the effective beam energy, Mainz aims to lower the current limit for Q 2 min by more than an order of magnitude [31]. The approach has significantly different systematics than the classical approach.…”

Section: Scattering Experimentsmentioning

confidence: 99%