Evidence for strange-quark contributions to the nucleon's form factors at Q2=0.108 (GeV/c)2 -: art. no. 152001

被引：256

作者：

Maas, FE

Aulenbacher, K

Baunack, S

Capozza, L

Diefenbach, J

Gläser, B

Hammel, T

von Harrach, D

Imai, Y

Kabuss, EM

Kothe, R

Lee, JH

Lorente, A

Schilling, E

Schwaab, D

Sikora, M

Stephan, G

Weber, G

Weinrich, C

Altarev, I

Arvieux, J

El-Yakoubi, M

Frascaria, R

Kunne, R

Morlet, M

Ong, S

van de Wiele, J

Kowalski, S

Plaster, B

Suleiman, R

Taylor, S

机构：

[1] Johannes Gutenberg Univ Mainz, Inst Kernphys, D-55099 Mainz, Germany

[2] St Petersburg Inst Nucl Phys, Gatchina, Russia

[3] Univ Paris 11, Inst Phys Nucl, CNRS, IN2P3, F-91406 Orsay, France

[4] MIT, Nucl Sci Lab, Cambridge, MA 02139 USA

来源：

PHYSICAL REVIEW LETTERS | 2005年 / 94卷 / 15期

关键词：

D O I：

10.1103/PhysRevLett.94.152001

中图分类号：

O4 [物理学];

学科分类号：

0702 ;

摘要：

We report on a measurement of the parity violating asymmetry in the elastic scattering of polarized electrons off unpolarized protons with the A4 apparatus at MAMI in Mainz at a four momentum transfer value of Q(2) = 0.108 (GeV/c)(2) and at a forward electron scattering angle of 30 degrees <theta(e)< 40 degrees. The measured asymmetry is A(LR)((e) over right arrow )p = [-.36 +/- 0.29(stat) +/- 0.13(syst)] x 10(-6). The expectation from the standard model assuming no strangeness contribution to the vector current is A(0)=(-2.06 +/- 0.14) x 10(-6). We have improved the statistical accuracy by a factor of 3 as compared to our previous measurements at a higher Q(2). We have extracted the strangeness contribution to the electromagnetic form factors from our data to be G(E)(s) + 0.106G(M)(s) = 0.071 +/- 0.036 at Q(2) = 0.108 (GeV/c)(2). We again find the value for G(E)(s) + 0.106G(M)(s) to be positive, this time at an improved significance level of two sigma.

引用

页码：1 / 4

页数：4

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