904 research outputs found
QCD traveling waves at non-asymptotic energies
Using consistent truncations of the BFKL kernel, we derive analytical
traveling-wave solutions of the Balitsky-Kovchegov saturation equation for both
fixed and running coupling. A universal parametrization of the ``interior'' of
the wave front is obtained and compares well with numerical simulations of the
original Balitsky-Kovchegov equation, even at non-asymptotic energies. Using
this universal parametrization, we find evidence for a traveling-wave pattern
of the dipole amplitude determined from the gluon distribution extracted from
deep inelastic scattering data.Comment: 10 pages, 5 figures, minor revision, version to appear in PL
The unintegrated gluon distribution from the CCFM equation
The gluon distribution f(x, k_t^2,mu^2), unintegrated over the transverse
momentum k_t of the gluon, satisfies the angular-ordered CCFM equation which
interlocks the dependence on the scale k_t with the scale \mu of the probe. We
show how, to leading logarithmic accuracy, the equation can be simplified to a
single scale problem. In particular we demonstrate how to determine the
two-scale unintegrated distribution f(x,k_t^2,mu^2) from knowledge of the
integrated gluon obtained from a unified scheme embodying both BFKL and DGLAP
evolution.Comment: 16 pages LaTeX, 3 eps figure
Anterior chamber depth in mice is controlled by several quantitative trait loci
Anterior chamber depth (ACD) is a quantitative trait associated with primary angle closure glaucoma (PACG). Although ACD is highly heritable, known genetic variations explain a small fraction of the phenotypic variability. The purpose of this study was to identify additional ACD-influencing loci using strains of mice. Cohorts of 86 N2 and 111 F2 mice were generated from crosses between recombinant inbred BXD24/TyJ and wild-derived CAST/EiJ mice. Using anterior chamber optical coherence tomography, mice were phenotyped at 10–12 weeks of age, genotyped based on 93 genome-wide SNPs, and subjected to quantitative trait locus (QTL) analysis. In an analysis of ACD among all mice, six loci passed the significance threshold of p = 0.05 and persisted after multiple regression analysis. These were on chromosomes 6, 7, 11, 12, 15 and 17 (named Acdq6, Acdq7, Acdq11, Acdq12, Acdq15, and Acdq17, respectively). Our findings demonstrate a quantitative multi-genic pattern of ACD inheritance in mice and identify six previously unrecognized ACD-influencing loci. We have taken a unique approach to studying the anterior chamber depth phenotype by using mice as genetic tool to examine this continuously distributed trait
The state of workplace union reps organisation in Britain today
This article provides a brief evaluation of the state of workplace union reps’ organization in Britain as we approach the second decade of the 2000s. It documents the severe weakening of workplace union organization over the last 25 years, which is reflected in the declining number of reps, reduced bargaining power and the problem of bureaucratization. But it also provides evidence of the continuing resilience, and even combativity in certain areas of employment, of workplace union reps organization, and considers the future potential for a revival of fortunes
Solution of the Kwiecinski evolution equations for unintegrated parton distributions using the Mellin transform
The Kwiecinski equations for the QCD evolution of the unintegrated parton
distributions in the transverse-coordinate space (b) are analyzed with the help
of the Mellin-transform method. The equations are solved numerically in the
general case, as well as in a small-b expansion which converges fast for b
Lambda_QCD sufficiently small. We also discuss the asymptotic limit of large bQ
and show that the distributions generated by the evolution decrease with b
according to a power law. Numerical results are presented for the pion
distributions with a simple valence-like initial condition at the low scale,
following from chiral large-N_c quark models. We use two models: the Spectral
Quark Model and the Nambu--Jona-Lasinio model. Formal aspects of the equations,
such as the analytic form of the b-dependent anomalous dimensions, their
analytic structure, as well as the limits of unintegrated parton densities at x
-> 0, x -> 1, and at large b, are discussed in detail. The effect of spreading
of the transverse momentum with the increasing scale is confirmed, with
growing asymptotically as Q^2 alpha(Q^2). Approximate formulas for
for each parton species is given, which may be used in practical
applications.Comment: 18 pages, 6 figures, RevTe
A Magnetic Transition Probed by the Ce Ion in Square-Lattice Antiferromagnet CeMnAsO
We examined the magnetic properties of the square-lattice antiferromagnets
CeMnAsO and LaMnAsO and their solid solutions La1-xCexMnAsO by resistivity,
magnetic susceptibility, and heat capacity measurements below room temperature.
A first-order phase transition is observed at 34.1 K, below which the
ground-state doublet of the Ce ion splits by 3.53 meV. It is likely that Mn
moments already ordered above room temperature are reoriented at the
transition, as reported for related compounds, such as NdMnAsO and PrMnSbO.
This transition generates a large internal magnetic field at the Ce site in
spite of the fact that simple Heisenberg interactions should be cancelled out
at the Ce site owing to geometrical frustration. The transition takes place at
nearly the same temperature with the substitution of La for Ce up to 90%. The
Ce moment does not undergo long-range order by itself, but is parasitically
induced at the transition, serving as a good probe for detecting the magnetism
of Mn spins in a square lattice.Comment: 11 pages, 5 figures, to be published in J. Phys. Soc. Jp
Small x resummation in collinear factorisation
The summation of the small x-corrections to hard-scattering QCD amplitudes by
collinear factorisation method is reconsidered and the K-factor is derived in
leading ln x approximation with a result differing from the corresponding
expression by Catani and Hautmann (Nucl. Phys. B 427, 475, 1994). The
significance of the difference is demonstrated in the examples of structure
function F_L and of exclusive vector meson electroproduction. The formulation
covers the channels of non-vanishing conformal spin n paving the way for new
applications.Comment: 34 pages, 6 figure
Lattice collapse and quenching of magnetism in CaFe2As2 under pressure: A single crystal neutron and x-ray diffraction investigation
Single crystal neutron and high-energy x-ray diffraction have identified the
phase lines corresponding to transitions between the ambient-pressure
tetragonal (T), the antiferromagnetic orthorhombic (O) and the non-magnetic
collapsed tetragonal (cT) phases of CaFe2As2. We find no evidence of additional
structures for pressures up to 2.5 GPa (at 300 K). Both the T-cT and O-cT
transitions exhibit significant hysteresis effects and we demonstrate that
coexistence of the O and cT phases can occur if a non-hydrostatic component of
pressure is present. Measurements of the magnetic diffraction peaks show no
change in the magnetic structure or ordered moment as a function of pressure in
the O phase and we find no evidence of magnetic ordering in the cT phase. Band
structure calculations show that the transition results in a strong decrease of
the iron 3d density of states at the Fermi energy, consistent with a loss of
the magnetic moment.Comment: List of authors in metadata and typos in labeling of inset in Fig.
1(a) corrected. One ref. added. No other change
- …