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arXiv · 0902.0780

Medium modifications of the bound nucleon GPDs and the quark contribution to the spin sum rule

V. Guzey·A. W. Thomas·K. Tsushima
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Abstract

We estimate the nuclear medium modifications of the quark contribution to the bound nucleon spin sum rule, J^{q*}, as well as the separate helicity, ΔΣ*, and the angular momentum, L^{q*}, contributions to J^{q*}. For the calculation of the bound nucleon generalized parton distributions (GPDs), we use as input the bound nucleon elastic form factors predicted in the quark-meson coupling model. Our model for the bound nucleon GPDs is relevant for incoherent deeply virtual Compton scattering (DVCS) with nuclear targets. We find that the m5Aedium modifications increase J^{q*} and L^{q*} and decrease ΔΣ* compared to the free nucleon case. The effect is large and increases with increasing nuclear density ρ. For instance, at ρ=ρ_0=0.15 fm^{-3}, J^{q*} increases by 7%, L^{q*} increases by 20%, and ΔΣ* decreases by 17%. These in-medium modifications of the bound nucleon spin properties may be understood qualitatively in terms of the enhancement of the lower component of the quark Dirac spinor in the nuclear medium.

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V. Guzey, A. W. Thomas, K. Tsushima. 2009-06-29. Medium modifications of the bound nucleon GPDs and the quark contribution to the spin sum rule. https://doi.org/10.1103/physrevc.79.055205

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