Longitudinal double-spin asymmetry $A_1^{\mathrm{p}}$ and spin-dependent structure function $g_1^{\mathrm{p}}$ of the proton at small values of $x$ and $Q^2$

Abstract

We present a precise measurement of the proton longitudinal double-spin asymmetry $A_1^{\mathrm{p}}$ and the proton spin-dependent structure function $g_1^{\mathrm{p}}$ at photon virtualities $0.006(\mathrm{GeV}/c{)}^2<Q^2<1(\mathrm{GeV}/c{)}^2$ in the Bjorken $x$ range of $4\times 10^{-5}<x<4\times 10^{-2}$. The results are based on data collected by the COMPASS Collaboration at CERN using muon beam energies of $160\mathrm{GeV}$ and $200\mathrm{GeV}$. The statistical precision is more than tenfold better than that of the previous measurement in this region. In the whole range of $x$, the measured values of $A_1^{\mathrm{p}}$ and $g_1^{\mathrm{p}}$ are found to be positive. It is for the first time that spin effects are found at such low values of $x$.

arXiv comment19 pages, 7 figures

References in corpus (13)

• The COMPASS Experiment at CERN
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• A Modification of the Saturation Model: DGLAP evolution
• Precise determination of the spin structure function ${\mathbf{g}}_1$ of the proton, deuteron and neutron
• Evidence for polarization of gluons in the proton
• The Spin-dependent Structure Function of the Proton g_1^p and a Test of the Bjorken Sum Rule
• The Spin Structure Function $g_1^{\mathrm{p}}$ of the Proton and a Test of the Bjorken Sum Rule
• Spin asymmetry A_1^d and the spin-dependent structure function g_1^d of the deuteron at low values of x and Q^2
• Model independent QED corrections to the process $ep⟶eX$
• Spin structure function $g_1(x,Q^2)$ and the DHGHY integral $I(Q^2)$ at low $Q^2$: predictions from the GVMD model
• Singlet structure function g_1 at small x and small Q^2
• Spin dependent structure function g_1 at low x and low Q^2
• Perturbative power Q^2-corrections to the structure function g(1)

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