Determination of quadrupole strengths in the <textbox>γ^*p→Δ(1232)textbox> transition at

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• 作者：N.F. Sparveris ; P. Achenbach ; C. Ayerbe Gayoso ; D. Baumann ; J. Bernauer ; A.M. Bernstein ; R. B&#xf6 ; hm ; D. Bosnar ; T. Botto ; A. Christopoulou ; D. Dale ; M. Ding ; M.O. Distler ; L. Doria ; J. Friedrich ; A.
• 关键词：EMR ; CMR ; Electro-pion production ; Nucleon deformation
• 刊名：Physics Letters B
• 出版年：2007
• 期刊代码：58_03702693
• 类别：ph
• 出版时间：26 July 2007
• 卷：651
• 期：2-3
• 页码：102-107
• 文件大小：525 K

摘要

We report new precise thURL&_method=retrieve&_udi=B6TVN-4NNYJ63-1&_mathId=mml28&_user=10&_cdi=5539&_rdoc=6&_acct=C000050221&_version=1&_userid=10&md5=b123fd2392e5f0ab0f6f1dc4f4f9c26e">ttp://www.sciencedirect.com/cache/MiamiImageURL/B6TVN-4NNYJ63-1-29/0?wchp=dGLbVtz-zSkWb" alt="Click to view the MathML source" align="absbottom" border="0" height=18 width=76> measurements at the peak of the tyle="text-decoration:none; color:black" href="/science?_ob=MathURL&_method=retrieve&_udi=B6TVN-4NNYJ63-1&_mathId=mml29&_user=10&_cdi=5539&_rdoc=6&_acct=C000050221&_version=1&_userid=10&md5=1d2db94fa1ef34481c3f12b288c1a04f" title="Click to view the MathML source">Δ⁺(1232) resonance at thURL&_method=retrieve&_udi=B6TVN-4NNYJ63-1&_mathId=mml30&_user=10&_cdi=5539&_rdoc=6&_acct=C000050221&_version=1&_userid=10&md5=fd844634140ed1e487596aa022422ac8">ttp://www.sciencedirect.com/cache/MiamiImageURL/B6TVN-4NNYJ63-1-33/0?wchp=dGLbVtz-zSkWb" alt="Click to view the MathML source" align="absbottom" border="0" height=18 width=136> performed at the Mainz Microtron (MAMI). The new data are sensitive to both the electric (E2) and the Coulomb (C2) quadrupole amplitudes of the tyle="text-decoration:none; color:black" href="/science?_ob=MathURL&_method=retrieve&_udi=B6TVN-4NNYJ63-1&_mathId=mml31&_user=10&_cdi=5539&_rdoc=6&_acct=C000050221&_version=1&_userid=10&md5=f6716f34539489c453dab7417deece93" title="Click to view the MathML source">γ^*N→Δ transition. They yield precise quadrupole to dipole amplitude ratios: tyle="text-decoration:none; color:black" href="/science?_ob=MathURL&_method=retrieve&_udi=B6TVN-4NNYJ63-1&_mathId=mml32&_user=10&_cdi=5539&_rdoc=6&_acct=C000050221&_version=1&_userid=10&md5=f80bc1e2c65421ec486457ed3600f2d3" title="Click to view the MathML source">CMR=(−5.09±0.28_stat+sys±0.30_model)% and tyle="text-decoration:none; color:black" href="/science?_ob=MathURL&_method=retrieve&_udi=B6TVN-4NNYJ63-1&_mathId=mml33&_user=10&_cdi=5539&_rdoc=6&_acct=C000050221&_version=1&_userid=10&md5=cefb4b909655ff39ff03ce722fd7d559" title="Click to view the MathML source">EMR=(−1.96±0.68_stat+sys±0.41_model)% for thURL&_method=retrieve&_udi=B6TVN-4NNYJ63-1&_mathId=mml34&_user=10&_cdi=5539&_rdoc=6&_acct=C000050221&_version=1&_userid=10&md5=51c69e5fb2b98a6346e9921b93b2a92e">ttp://www.sciencedirect.com/cache/MiamiImageURL/B6TVN-4NNYJ63-1-4N/0?wchp=dGLbVtz-zSkWb" alt="Click to view the MathML source" align="absbottom" border="0" height=23 width=358>. The new results are in disagreement with Constituent Quark Model predictions and in qualitative agreement with models that account for mesonic contributions, including recent Lattice calculations. They thus give further credence to the conjecture of deformation in hadronic systems favoring the attribution of the origin of deformation to the dominance of mesonic effects.