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Register a new userImportance of Higher Twist Corrections in Polarized DIS
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Alexander Sidorov Viktorovich
Publication date
2003
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English
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The higher twist corrections $h^N(x)/Q^2$ to the spin dependent proton and neutron $g_1$ structure functions are extracted from the world data on $g_1(x,Q^2)$ in a model independent way and found to be non-negligible. Their role in determining the polarized parton densities in the nucleon is discussed. It is also considered how the results are influenced by the recent JLab and HERMES/d inclusive DIS data.
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We calculate power corrections to TMD factorization for particle production by gluon-gluon fusion in hadron-hadron collisions.
We study a twist decomposition of diffractive structure functions in the diffractive deep inelastic scattering (DDIS) at HERA. At low Q2 and at large energy the data exhibit a strong excess, up to about 100%, above the twist 2 NLO DGLAP description. The excess in consistent with higher twist effects. It is found, that complementing the DGLAP fit by twist 4 and 6 components of the GBW saturation model leads to a good description of data at low Q2. We conclude that the DDIS at HERA provides the first, strong evidence of higher twist effects in DIS.
The one-loop NLO radiative corrections to the observables in polarized DIS using assumption that a quark is an essential massive particle are considered. If compared with classical QCD formulae the obtained results are identical for the unpolarized and different for polarized sum rules, that can be explained as the influence of the finite quark mass effects on NLO QCD corrections. The explicit expression for one-loop NLO QCD contribution to the structure function g_2 is presented.
Including the effects of the ${cal{O}}(gtrsim 1 {rm GeV})$ masses of the charm quark, $tau$ lepton and target nucleon in DIS phenomenology is discussed with applications to CC neutrino DIS: Neutrino data for $F_2$ are revisited within the global analysis framework. A fully differential calculation refines the CC charm production process as a gate to extract ${s(x), {bar s} (x) }$. New results are presented for a heavy quark version of the CTEQ6 set of PDFs and for ($ u_{mu} to u_{tau}$ oscillation-signal) $tau$ neutrino cross sections.
We update QCD calculations of $B to pi, K$ form factors at large hadronic recoil by including the subleading-power corrections from the higher-twist $B$-meson light-cone distribution amplitudes (LCDAs) up to the twist-six accuracy and the strange-quark mass effects at leading-power in $Lambda/m_b$ from the twist-two $B$-meson LCDA $phi_B^{+}(omega, mu)$. The higher-twist corrections from both the two-particle and three-particle $B$-meson LCDAs are computed from the light-cone QCD sum rules (LCSR) at tree level. In particular, we construct the local duality model for the twist-five and -six $B$-meson LCDAs, in agreement with the corresponding asymptotic behaviours at small quark and gluon momenta, employing the QCD sum rules in heavy quark effective theory at leading order in $alpha_s$. The strange quark mass effects in semileptonic $B to K$ form factors yield the leading-power contribution in the heavy quark expansion, consistent with the power-counting analysis in soft-collinear effective theory, and they are also computed from the LCSR approach due to the appearance of the rapidity singularities. We further explore the phenomenological aspects of the semileptonic $B to pi ell u$ decays and the rare exclusive processes $B to K u u$, including the determination of the CKM matrix element $|V_{ub}|$, the normalized differential $q^2$ distributions and precision observables defined by the ratios of branching fractions for the above-mentioned two channels in the same intervals of $q^2$.
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