Department of Physics, University of Massachusetts Amherst, Amherst, Massachusetts 01003, USA.
Institut für Kernphysik, Universität Mainz, D-55099 Mainz, Germany.
Phys Rev Lett. 2015 Mar 20;114(11):112501. doi: 10.1103/PhysRevLett.114.112501. Epub 2015 Mar 19.
The spin polarizabilities of the nucleon describe how the spin of the nucleon responds to an incident polarized photon. The most model-independent way to extract the nucleon spin polarizabilities is through polarized Compton scattering. Double-polarized Compton scattering asymmetries on the proton were measured in the Δ(1232) region using circularly polarized incident photons and a transversely polarized proton target at the Mainz Microtron. Fits to asymmetry data were performed using a dispersion model calculation and a baryon chiral perturbation theory calculation, and a separation of all four proton spin polarizabilities in the multipole basis was achieved. The analysis based on a dispersion model calculation yields γ(E1E1)=-3.5±1.2, γ(M1M1)=3.16±0.85, γ(E1M2)=-0.7±1.2, and γ(M1E2)=1.99±0.29, in units of 10(-4) fm(4).
核子的自旋极化率描述了核子的自旋对入射极化光子的响应方式。最独立于模型的方法是通过极化康普顿散射来提取核子的自旋极化率。在美因茨微环中，使用圆偏振入射光子和横极化质子靶，在Δ（1232）区域测量了质子的双极化康普顿散射不对称性。使用色散模型计算和重子手征微扰理论计算对不对称性数据进行拟合，在多极子基中实现了所有四个质子自旋极化率的分离。基于色散模型计算的分析得出 γ(E1E1)=-3.5±1.2，γ(M1M1)=3.16±0.85，γ(E1M2)=-0.7±1.2，和 γ(M1E2)=1.99±0.29，单位为 10(-4) fm(4)。
