Determination of smallxshadowing corrections at DESY HERA
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Abstract:
The recent ${F}_{2}$ data can be described using the DGLAP evolution equations with an appropriate choice of input distributions and the choice of the starting scale for the ${Q}^{2}$ evolution. We demonstrate in this paper that we cannot conclude that there are no significant shadowing corrections in the DESY HERA kinematic region using ${F}_{2}$ data only. In this paper we calculate the shadowing corrections to the longitudinal structure function ${F}_{L}{(x,Q}^{2})$ and to the charm component of the proton structure function ${F}_{2}^{c}{(x,Q}^{2})$ in the HERA kinematic region using an eikonal approach. We demonstrate that the shadowing corrections to these observables are very large and that charm production is strongly modified at small $x.$ Our results agree with the few recent H1 data.Keywords:
DESY
DGLAP
Charm (quantum number)
Structure function
The recent ${F}_{2}$ data can be described using the DGLAP evolution equations with an appropriate choice of input distributions and the choice of the starting scale for the ${Q}^{2}$ evolution. We demonstrate in this paper that we cannot conclude that there are no significant shadowing corrections in the DESY HERA kinematic region using ${F}_{2}$ data only. In this paper we calculate the shadowing corrections to the longitudinal structure function ${F}_{L}{(x,Q}^{2})$ and to the charm component of the proton structure function ${F}_{2}^{c}{(x,Q}^{2})$ in the HERA kinematic region using an eikonal approach. We demonstrate that the shadowing corrections to these observables are very large and that charm production is strongly modified at small $x.$ Our results agree with the few recent H1 data.
DESY
DGLAP
Charm (quantum number)
Structure function
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The high precision diffractive DIS data from the H1 and ZEUS collaborations discussed elsewhere in these proceedings are compared. NLO DGLAP QCD fits are performed separately to the H1 and ZEUS data samples and the resulting diffractive PDFs are compared.
ZEUS (particle detector)
DGLAP
Structure function
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We make predictions for the diffractive longitudinal structure function F_L^D to be measured at HERA, based on DGLAP fits of diffractive parton distributions with twist--4 contribution. This contribution describes diffractive qqbar production from longitudinal photons and significantly changes predictions for F_L^D obtained in pure DGLAP analyses.
DGLAP
Structure function
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Preliminary results on a measurement of the proton structure function F_2 are reported for momentum transfers squared Q^2 between 1.5~GeV^2 and 5000 GeV^2 and for Bjorken x between 5.10^{-5} and 0.32 using data collected by the HERA experiments H1 and ZEUS in 1994. F_2 increases significantly with decreasing x, even in the lowest reachable Q^2 region. The data are well described by a Next to Leading Order QCD fit, and support within the present precision that the rise at low x within this Q^2 range is generated "radiatively" via the DGLAP evolution equations. Prospects for future structure function measurements at HERA are briefly mentioned.
DGLAP
ZEUS (particle detector)
Structure function
Momentum (technical analysis)
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DGLAP
Resummation
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Citations (40)
Preliminary results on a measurement of the proton structure function F_2 are reported for momentum transfers squared Q^2 between 1.5~GeV^2 and 5000 GeV^2 and for Bjorken x between 5.10^{-5} and 0.32 using data collected by the HERA experiments H1 and ZEUS in 1994. F_2 increases significantly with decreasing x, even in the lowest reachable Q^2 region. The data are well described by a Next to Leading Order QCD fit, and support within the present precision that the rise at low x within this Q^2 range is generated radiatively via the DGLAP evolution equations. Prospects for future structure function measurements at HERA are briefly mentioned.
DGLAP
ZEUS (particle detector)
Structure function
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DGLAP
ZEUS (particle detector)
Structure function
Perturbative QCD
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Citations (149)
The data on the diffractive deep inelastic scattering (DDIS) at HERA exhibit a strong excess, up to about 100%, above the twist-two NLO DGLAP description at low $Q^2$ and at large energy. I show, that complementing the DGLAP fit by twist 4 and 6 components of the saturation model leads to a good description of data at low $Q^2$ and conclude that the DDIS at HERA provides the first evidence of higher twist effects in DIS.
DGLAP
Saturation (graph theory)
Structure function
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The QCD evolution of both unpolarized and polarized generalized parton distributions (GPDs) to next-to-leading order (NLO) accuracy is presented, in both the DGLAP and ERBL regions, for two appropriately symmetrized input distributions based on conventional parton density functions. To illustrate the relative size of the NLO corrections a comparison is made with leading order evolution of the same distributions. For the first time, NLO results are given for both small and large values of the skewedness parameter, $\ensuremath{\zeta}{=x}_{\mathrm{bj}},$ i.e., for all of the kinematic range relevant to DESY HERA and HERMES.
DGLAP
DESY
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DESY
ZEUS (particle detector)
Structure function
Neutral current
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Citations (234)