Coll Positioning systems: a two‐dimensional approach
The basic elements of Coll positioning systems (n clocks broadcasting electromagnetic signals in a n‐dimensional space‐time) are presented in the two‐dimensional case. This simplified approach allows us to explain and to analyze the properties and interest of these relativistic positioning systems. The positioning system defined in flat metric by two geodesic clocks is analyzed. The interest of the Coll systems in gravimetry is pointed out.

title: Vacuum type I spacetimes and aligned Papapetrou fields: symmetries
abstract: We analyse type I vacuum solutions admitting an isometry whose Killing 2-form is aligned with a principal bivector of the Weyl tensor, and we show that these solutions belong to a family of type I metrics which admit a group G3 of isometries. We give a classification of this family and study the Bianchi type for each class. The classes compatible with an aligned Killing 2-form are also determined. The Szekeres–Brans theorem is extended to non-vacuum spacetimes with vanishing Cotton tensor.

title: Aligned Electric and Magnetic Weyl Fields
abstract: The results on the non-existence of purely magnetic solutions are extended to the wider class of spacetimes which have homothetic electric and magnetic Weyl fields. This class is a particularization of the spacetimes admitting a direction for which the relative electric and magnetic Weyl fields are aligned. We give an invariant characterization of these metrics and study the properties of their Debever null vectors. The directions ‘observing’ aligned electric and magnetic Weyl fields are obtained for every Petrov-Bel type.

title: On the super-energy radiative gravitational fields
abstract: We extend our recent analysis (Ferrando J J and Saez J A 2012 ) on the Bel radiative gravitational fields to the super-energy radiative gravitational fields defined by Garcia-Parrado (2008 ). We give an intrinsic characterization of the new radiative fields and consider some distinguished classes of both radiative and non-radiative fields. Several super-energy inequalities are improved.

title: An intrinsic characterization of the Kerr metric
abstract: We give the necessary and sufficient (local) conditions for a metric tensor to be the Kerr solution. These conditions exclusively involve explicit concomitants of the Riemann tensor.

title: On the intrinsic labeling of space‐times: a characterization of the Kerr solution
abstract: The interest of obtaining an intrinsic (depending solely on the metric tensor) and fully explicit characterization of a space‐time is pointed out. We give the necessary and sufficient (local) conditions for a metric tensor to be the Kerr solution. These conditions exclusively involve concomitants of the Weyl tensor.

title: Measurement of D± production in deep inelastic ep scattering with the ZEUS detector at HERA
abstract: A bstractCharm production in deep inelastic ep scattering was measured with the ZEUS detector using an integrated luminosity of 354 pb−1. Charm quarks were identified by reconstructing D± mesons in the D± → K∓π±π± decay channel. Lifetime information was used to reduce combinatorial background substantially. Differential cross sections were measured in the kinematic region 5 < Q2< 1000 GeV2, 0.02 < y < 0.7, 1.5 < pT (D±) < 15 GeV and |η(D±)| < 1.6, where Q2 is the photon virtuality, y is the inelasticity, and pT (D±) and η(D±) are the transverse momentum and the pseudorapidity of the D± meson, respectively. Next-to-leading-order QCD predictions are compared to the data. The charm contribution, $ F_2^{{c\overline{c}}} $, to the proton structure-function F2 was extracted.

title: Photoproduction of events with rapidity gaps between jets at HERA
abstract: The photoproduction of dijet events, where the two jets with the highest transverse energy are separated by a large gap in pseudorapidity, have been studied with the ZEUS detector using an integrated luminosity of 39 pb-1. Rapidity-gap events are defined in terms of the energy flow between the jets, such that the total summed transverse energy in this region is less than some value ETCUT. The data show a clear excess over the predictions of standard photoproduction models. This is interpreted as evidence for a strongly interacting exchange of a color-singlet object. Monte Carlo models which include such a color-singlet exchange are able to describe the data.

title: ATLAS measurements of the properties of jets for boosted particle searches
abstract: Measurements are presented of the properties of high transverse momentum jets, produced in proton-proton collisions at a center-of-mass energy of root s = 7 TeV. The data correspond to an integrated luminosity of 35 pb(-1) and were collected with the ATLAS detector in 2010. Jet mass, width, eccentricity, planar flow and angularity are measured for jets reconstructed using the anti-k(t) algorithm with distance parameters R 0: 6 and 1.0, with transverse momentum p(T) > 300 GeV and pseudorapidity vertical bar eta vertical bar < 2. The measurements are compared to the expectations of Monte Carlo generators that match leading-logarithmic parton showers to leading-order, or next-to-leading-order, matrix elements. The generators describe the general features of the jets, although discrepancies are observed in some distributions.

title: Measurement of high-Q2 charged current deep inelastic scattering cross sections with a longitudinally polarised positron beam at HERA
abstract: Measurements of the cross sections for charged current deep inelastic scattering in e+p collisions with a longitudinally polarised positron beam are presented. The measurements are based on a data sample with an integrated luminosity of 132 pb−1 collected with the ZEUS detector at HERA at a centre-of-mass energy of 318 GeV. The total cross section is presented at positive and negative values of the longitudinal polarisation of the positron beams. The single-differential cross-sections dσ/dQ2, dσ/dx and dσ/dy are presented for Q2>200 GeV2. The reduced cross-section $\tilde{\sigma}$ is presented in the kinematic range 200<Q2<60 000 GeV2 and 0.006<x<0.562. The measurements agree well with the predictions of the Standard Model. The results are used to determine a lower limit on the mass of a hypothetical right-handed W boson.

title: Inclusive jet cross sections and dijet correlations in D photoproduction at HERA
abstract: Inclusive jet cross sections in photoproduction for events containing a D ∗ D ∗ meson have been measured with the ZEUS detector at HERA using an integrated luminosity of 78.6 pb −1 78.6 pb −1 . The events were required to have a virtuality of the incoming photon, Q 2 Q 2 , of less than 1 GeV 2 , and a photon–proton centre-of-mass energy in the range 130 γp 130 W γ p 280 GeV . The measurements are compared with next-to-leading-order (NLO) QCD calculations. Good agreement is found with the NLO calculations over most of the measured kinematic region. Requiring a second jet in the event allowed a more detailed comparison with QCD calculations. The measured dijet cross sections are also compared to Monte Carlo (MC) models which incorporate leading-order matrix elements followed by parton showers and hadronisation. The NLO QCD predictions are in general agreement with the data although differences have been isolated to regions where contributions from higher orders are expected to be significant. The MC models give a better description than the NLO predictions of the shape of the measured cross sections.