A theoretical analysis has been performed of the HERMES semi-inclusive deepinelastic data on the difference between $\pi^{+}$ and $\pi^{-}$multiplicities. It turns out that the application of a standard perturbativeQCD analysis, using, as usual, isospin symmetry for the fragmentationfunctions, leads to a poor description of the deuteron data at small z values.If one allows a breaking of isospin invariance, a good fit to both proton anddeuteron data can be achieved for all measured z, but the level of isospinviolation, especially at small values of z, is simply not credible. We suspectthat the problem is a consequence of using the factorized QCD treatment in akinematic region where it is unjustified.
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机译:对$ \ pi ^ {+} $和$ \ pi ^ {-} $多重性之间的差异进行了HERMES半包容性深弹性数据的理论分析。事实证明,采用标准的扰动QCD分析(通常使用等位旋对称性来实现碎片功能)会导致在z值较小时氘代数据的描述不佳。如果允许打破等位旋不变性,则非常适合对于所有测得的z,质子和氘核数据都可以实现,但是同旋异构化的水平(尤其是在z的较小值下)根本不可靠。我们怀疑该问题是在不合理的运动区域中使用因式QCD处理的结果。
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