On the Leibniz bracket, the Schouten bracket and the Laplacian
The Leibniz bracket of an operator on a (graded) algebra is defined and some of its properties are studied. A basic theorem relating the Leibniz bracket of the commutator of two operators to the Leibniz bracket of them is obtained. Under some natural conditions, the Leibniz bracket gives rise to a (graded) Lie algebra structure. In particular, those algebras generated by the Leibniz bracket of the divergence and the Laplacian operators on the exterior algebra are considered, and the expression of the Laplacian for the product of two functions is generalized for arbitrary exterior forms.

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: 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 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: 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: Subjet distributions in deep inelastic scattering at HERA
abstract: Subjet distributions were measured in neutral current deep inelastic ep scattering with the ZEUS detector at HERA using an integrated luminosity of 81.7 pb−1. Jets were identified using the kT cluster algorithm in the laboratory frame. Subjets were defined as jet-like substructures identified by a reapplication of the cluster algorithm at a smaller value of the resolution parameter $y_{\rm cut}$. Measurements of subjet distributions for jets with exactly two subjets for $y_{\rm cut}=0.05$ are presented as functions of observables sensitive to the pattern of parton radiation and to the colour coherence between the initial and final states. Perturbative QCD predictions give an adequate description of the data.

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: Search for events with large missing transverse momentum, jets, and at least two tau leptons in 7 TeV proton–proton collision data with the ATLAS detector
abstract: A search for events with large missing transverse momentum, jets, and at least two tau leptons has been performed using 2 fb(-1) of proton-proton collision data at root s = 7 TeV recorded with the ...

title: Measurement of beauty production in deep inelastic scattering at HERA
abstract: The beauty production cross section for deep inelastic scattering events with at least one hard jet in the Breit frame together with a muon has been measured, for photon virtualities Q2>2 GeV2, with the ZEUS detector at HERA using integrated luminosity of 72 pb-1. The total visible cross section is σbb(ep→e jet μX)=40.9±5.7(stat.)-4.4+6. 0(syst.) pb. The next-to-leading order QCD prediction lies about 2.5 standard deviations below the data. The differential cross sections are in general consistent with the NLO QCD predictions; however at low values of Q2, Bjorken x, and muon transverse momentum, and high values of jet transverse energy and muon pseudorapidity, the prediction is about two standard deviations below the data.

title: Search for lepton-flavor violation at HERA
abstract: A search for lepton-flavor-violating interactions ep -> mu X and ep -> tau X has been performed with the ZEUS detector using the entire HERA I data sample, corresponding to an integrated luminosity of 130 pb(-1). The data were taken at center-of-mass energies, root s, of 300 and 318 GeV. No evidence of lepton-flavor violation was found, and constraints were derived on leptoquarks (LQs) that could mediate such interactions. For LQ masses below root s, limits were set on lambda(eq1) root beta(lq), where lambda(eq1) is the coupling of the LQ to an electron and a first-generation quark q(1), and beta(eq) is the branching ratio of the LQ to the final-state lepton l (mu or tau) and a quark q. For LQ masses much larger than root s, limits were set on the four-fermion interaction term lambda(eq alpha)lambda(eq beta)/M(L)(2)Q for LQs that couple to an electron and a quark q(alpha) and to a lepton l and a quark q(beta), where alpha and beta are quark generation indices. Some of the limits are also applicable to lepton-flavor-violating processes mediated by squarks in R-Parity-violating supersymmetric models. In some cases, especially when a higher-generation quark is involved and for the process ep -> tau X, the ZEUS limits are the most stringent to date.