Measurement of the Neutron Radius of 208Pb Through Parity Violation in Electron Scattering

By S. Abrahamyan, Z. Ahmed, H. Albataineh, K. Aniol, D. Armstrong, W. Armstrong, T. Averett, B. Babineau, A. Barbieri, V. Bellini and 125 more. 2012

352 citations recorded by the source corpus.

In contrast to the nuclear charge densities, which have been accurately measured with electron scattering, the knowledge of neutron densities still lack precision. Previous model-dependent hadron experiments suggest the difference between the neutron radius, Rn, of a heavy nucleus and the proton radius, Rp, to be in the order of several percent. To accurately obtain the difference, Rn-Rp, which is essentially a neutron skin, the Jefferson Lab Lead (208Pb) Radius Experiment (PREX) measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from 208Pb at an energy of 1.06 GeV and a scattering angle of 5° . Since Z0 boson couples mainly to neutrons, this asymmetry provides a clean measurement of Rn with respect to Rp. PREX was conducted at the Jefferson lab experimental Hall A, from March to June 2010. The experiment collected a final data sample of 2x 107 helicity-window quadruplets. The measured parity-violating electroweak asymmetry APV = 0.656 ± 0.060 (stat) ± 0.014 (syst) ppm corresponds to a difference between the radii of the neutron and proton distributions, Rn-Rp = 0.33+0.16-0.18 fm and provides the first electroweak observation of the neutron skin as expected in a heavy, neutron-rich nucleus. The value of the neutron radiusmore » of 208Pb has important implications for models of nuclear structure and their application in atomic physics and astrophysics such as atomic parity non-conservation (PNC) and neutron stars.« less

Subfields: Nuclear and High Energy Physics, Radiation

View Paper: https://www.semanticscholar.org/paper/f4574730a9c879094dde81106dcf915fe48e67b4

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Citations in the corpus

The P2 experiment (2018, background): “The (208)Pb Radius EXperiment (PREX) at JLab has provided the first proof-of-principle of the application of parity-violating electron scattering for the measurement of the neutron-skin thickness [46].”
Search for New Physics with Atoms and Molecules (2017, methodology): “Bounds on the e-p new physics can also be directly established from PNC electron scattering off protons in the Q-weak experiment at JLAB (Androic et al., 2013).”
The Nuclear Symmetry Energy (2016, methodology): “liminary conﬁguration (PREX-I), while CREX experiment has been approved. The updated version of PREX (PREX-II) has also been approved. The result of PREX-I experiment is reported in Fig. 13 from ref. [73]. Here is indicated the value of the measured asymmetry (the square at the center of the cross) ”
Symmetry Parameter Constraints from a Lower Bound on Neutron-matter Energy (2016, background): “…rnp=0.159±0.041 (Danielewicz & Lee 2009) (but see Danielewicz et al. (2017), who find rnp=0.223± 0.018 fm), the most recent neutron-skin thickness measurement from the PREX experiment (Abrahamyan et al. 2012) is r 0.33np 0.18 0.16= - + fm and thus the mean value is larger than our upper bound.”