F 2 c at low x

We study the heavy-quark contributions to the proton structure function F ₂(x,Q ²) at next-to-leading order using compact formulas at small values of Bjorken??s x variable. The formulas provide a good agreement with the modern HERA data for F ₂ ^c (x,Q ²).     

F 2/x G(x,Q 2) ratio at small x and the role of the contribution from infrared region

We consider the light quark electroproduction cross section.     

Q 2-evolution of parton densities at small x values. Combined H1 and ZEUS F2 data

We use the Bessel-inspired behavior of the structure function F ₂ at small x, obtained for a flat initial condition in the DGLAP evolution equations, with “frozen” and analytic modifications of the strong coupling constant to study precise combined H1 and ZEUS data for the structure function F ₂ published recently.     

Physical anomalous dimensions at small x

I present a theoretical discussion of the uncertainties related to the QCD analysis of the proton structure function F ₂(x,Q ²) at small x. The role played by the ‘unphysical’ gluon density is pointed out. It is shown how the study of more observables can reduce the theoretical uncertainty and, in particular, an alternative method of analysis, based on the introduction of physical anomalous dimensions, is suggested.     

Measurement of the proton structure function F 2 at low x and low Q 2 at HERA

We report on a measurement of the proton structure function F ₂ in the range 3.5 × 10^?5 ≤ x ≤ 4 × 10^?3 and 1.5 GeV² ≤ Q ² ≤ 15 GeV² at the ep collider HERA operating at a centre-of-mass energy of ${sqrt s} = 300 {? GeV}$. The rise of F ₂ with decreasing x observed in the previous HERA measurements persists in this lower x and Q ² range. The Q ² evolution of F ₂, even at the lowest Q ² and x measured, is consistent with perturbative QCD.     

Evaluation of angular momentum projected energy at small deformations

An expression for angular momentum projected energy at small deformations is given which can, of course, be used for large deformations as well. Numerical calculations are carried out for the nucleus ¹²⁰Sn. It is shown that the Hartree-Fock-Bogolyubov theory with angular momentum projection always produces non-spherical equilibrium shapes.     

Polarized deuteron structure functions at small x

We investigate shadowing corrections to the polarized deuteron structure functions g ₁ ^d and b₁. In the kinematic domain of current fixed target experiments we observe that shadowing effects in g ₁ ^d are approximately twice as large as for the unpolarized structure function F ₂ ^d . Furthermore, we find that b₁ is surprisingly large at x < 0.1 and receives dominant contributions from coherent double scattering.     

Multiplicity distribution of colour dipoles at small x

The colour dipole multiplicity distribution is analysed for the wave function of a heavy onium state at small x. Numerical results for the average multiplicity and the effect of cutoffs on its power growth are presented. Then, the full multiplicity distribution is analysed: the second multiplicity moment is derived and the tail of the distribution is shown to behave as exp(− log²n). These results are confirmed by a Monte Carlo simulation which also gives the fluctuations in the spatial density of dipoles.     

Magnetic ordering of YBa2(Cu1−x Fe x )3O7

The Mössbauer spectra of YBa₂(Cu_1?x Fe _x )₃O₇ at room temperature show several doublets attributed to Fe in Cu(1) sites with different oxygen configurations. Here we present a systematic study performed at 4.2 K forx=0.005, 0.01, 0.03, 0.05, 0.10, 0.15. To obtain information about the magnetic ordered state two samples, withx=0.005 andx=0.15, have been studied at 4.2 K underB _ext=5 T. The Mössbauer spectra indicate that the iron moments are polarized forx=0.005, while in the ordered state (x=0.15) they have an antiferromagnetic or spin-glass-like arrangement with high anisotropy.