Title: Weak charge form factor and radius of ²⁰⁸Pb through parity violation in electron scattering

Abstract

We use distorted wave electron scattering calculations to extract the weak charge form factor F_W($$\bar{q}$$), the weak charge radius R_W, and the point neutron radius R_n, of ²⁰⁸Pb from the PREX parity violating asymmetry measurement. The form factor is the Fourier transform of the weak charge density at the average momentum transfer $$\bar{q}$$ = 0.475 fm^-1. We find F_W($$\bar{q}$$) = 0.204 ± 0.028(exp) ± 0.001(model). We use the Helm model to infer the weak radius from F_W($$\bar{q}$$). We find RW = 5.826 ± 0.181(exp) ± 0.027(model) fm. Here the exp error includes PREX statistical and systematic errors, while the model error describes the uncertainty in R_W from uncertainties in the surface thickness σ of the weak charge density. The weak radius is larger than the charge radius, implying a 'weak charge skin' where the surface region is relatively enriched in weak charges compared to (electromagnetic) charges. We extract the point neutron radius R_n = 5.751 ± 0.175 (exp) ± 0.026(model) ± 0.005(strange) fm, from R_W. Here there is only a very small error (strange) from possible strange quark contributions. We find R_n to be slightly smaller than R_W because of the nucleon's size. As a result, we find a neutron skin thickness of R_n-R_p = 0.302 ± 0.175 (exp) ± 0.026 (model) ± 0.005 (strange) fm, where R_p is the point proton radius.

Authors:

Horowitz, C. J. ^[1]; Ahmed, Z. ^[2]; Jen, C. -M. ^[2]; Rakhman, A. ^[2]; Souder, P. A. ^[2]; Dalton, M. M. ^[3]; Liyanage, N. ^[3]; Paschke, K. D. ^[3]; Saenboonruang, K. ^[3]; Silwal, R. ^[3]; Franklin, G. B. ^[4]; Friend, M. ^[4]; Quinn, B. ^[4]; Kumar, K. S. ^[5]; McNulty, D. ^[5]; Mercado, L. ^[5]; Riordan, S. ^[5]; Wexler, J. ^[5]; Michaels, R. W. ^[6]; Urciuoli, G. M. ^[7]

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+ Show Author Affiliations

1. Univ. of Tennessee, Knoxville, TN (United States); Indiana Univ., Bloomington, IN (United States)
2. Syracuse Univ., Syracuse, NY (United States)
3. Univ. of Virginia, Charlottesville, VA (United States)
4. Carnegie Mellon Univ., Pittsburgh, PA (United States)
5. Univ. of Massachusetts Amherst, Amherst, MA (United States)
6. Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
7. INFN, Rome (Italy)

Publication Date:

Mon Mar 26 00:00:00 EDT 2012

Research Org.:

Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)

Sponsoring Org.:

USDOE Office of Science (SC)

OSTI Identifier:

1038244

Alternate Identifier(s):

OSTI ID: 1098581

Report Number(s):

JLAB-PHY-12-1409; DOE/OR/23177-1998; arXiv:1202.1468
Journal ID: ISSN 0556-2813; PRVCAN; TRN: US1201831

Grant/Contract Number:  

AC05-06OR23177

Resource Type:

Accepted Manuscript

Journal Name:

Physical Review C, Nuclear Physics

Additional Journal Information:

Journal Volume: 85; Journal Issue: 3; Journal ID: ISSN 0556-2813

Publisher:

American Physical Society (APS)

Country of Publication:

United States

Language:

English

Subject:

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ASYMMETRY; CHARGE DENSITY; ELECTRONS; FORM FACTORS; MOMENTUM TRANSFER; NEUTRONS; PARITY; PROTONS; QUARKS; SCATTERING; THICKNESS; LEAD 208