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arXiv 0803.1307nucl-th
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低能氘核电衰变的无π有效场论

Pion-less Effective Field Theory on Low-Energy Deuteron Electro-Disintegration

Stefan Christlmeier, Harald W. Griesshammer

摘要:

考虑到它与大爆炸核合成的关系以及已有的核模型与S-DALINAC实验数据之间的矛盾,在低能核有效场论中,在动量转移q <100 MeV,接近阈值的条件下,研究了无动力学π介子的电致氘核分裂2H(e,e 'p)n.电偶极电流在N2LO处和磁偶极电流在NLO处的结果比定量预测的更好地逐阶收敛,并且不包含自由参数。它是由简单的、众所周知的可观测量决定的。将双微分截面分解为横-横(L + T)、横-横(TT)和横-横干涉(LT)项,我们发现与Arenh Ovel等人用波恩势计算的势模型非常吻合。理论和数据对σ_{L + T}也有很好的一致性。然而,在理论方面,理论与实验之间的偏差在σ_{LT}上不可能达到30%,3-σ。从普适性,我们得出结论,没有正确的氘核渐近波函数的理论方法可以解释的数据。影响σ_{LT}的短距离未知贡献仅在高阶即百分之几的水平上进入。我们注意到报告数据的运动学和标准化存在一些问题。

英文摘要:

In view of its relation to Big-Bang Nucleo-Synthesis and a reported discrepancy between nuclear models and data taken at S-DALINAC, electro-induced deuteron break-up 2H(e,e' p)n is studied at momentum transfer q<100MeV and close to threshold in the low-energy nuclear Effective Field Theory without dynamical pions. The result at N2LO for electric dipole currents and at NLO for magnetic ones converges order-by-order better than quantitatively predicted and contains no free parameter. It is at this order determined by simple, well-known observables. Decomposing the doubly differential cross-section into the longitudinal-plus-transverse (L+T), transverse-transverse (TT) and longitudinal-transverse interference (LT) terms, we find excellent agreement with a potential-model calculation by Arenh"ovel et al using the Bonn potential. Theory and data also agree well on σ_{L+T}. There is however no space on the theory-side for the discrepancy of up to 30%, 3-σbetween theory and experiment in σ_{LT}. From universality, we conclude that no theoretical approach with the correct deuteron asymptotic wave-function can explain the data. Un-determined short-distance contributions that could affect σ_{LT} enter only at high orders, i.e. at the few-percent level. We notice some issues with the kinematics and normalisation of the data reported.

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