On direct measurement of the W production charge asymmetry at the LHC
The prospects for making a direct measurement of the W production charge asymmetry at the LHC are discussed. A modification to the method used at the Tevatron is proposed for measurements at the LHC. The expected sensitivity for such a measurement to parton distribution functions is compared to that for a measurement of the lepton charge asymmetry. The direct measurement approach is found to be less useful for placing constraints on parton distribution functions at the LHC than a measurement of the lepton charge asymmetry.

title: Exclusive electroproduction of two pions at HERA
abstract: The exclusive electroproduction of two pions in the mass range 0.4<Mππ<2.5 GeV has been studied with the ZEUS detector at HERA using an integrated luminosity of 82 pb−1. The analysis was carried out in the kinematic range of 2<Q2<80 GeV2, 32<W<180 GeV and |t|<0.6 GeV2, where Q2 is the photon virtuality, W is the photon-proton centre-of-mass energy and t is the squared four-momentum transfer at the proton vertex. The two-pion invariant-mass distribution is interpreted in terms of the pion electromagnetic form factor, |F(Mππ)|, assuming that the studied mass range includes the contributions of the ρ, ρ′ and ρ′′ vector-meson states. The masses and widths of the resonances were obtained and the Q2 dependence of the cross-section ratios σ(ρ′→ππ)/σ(ρ) and σ(ρ′′→ππ)/σ(ρ) was extracted. The pion form factor obtained in the present analysis is compared to that obtained in e+e−→π+π−.

title: Triggering on Long-Lived Neutral Particles in the ATLAS Detector
abstract: Neutral particles with long decay paths that decay to many-particle final states represent, from an experimental point of view, a challenge both for the trigger and for the reconstruction capabilities of the ATLAS apparatus. The Hidden Valley scenario serves as an excellent setting for the purpose of exploring the challenges to the trigger posed by long-lived particles.

title: HERA signature-based searches I: events with isolated leptons and missing transverse momentum at HERA
abstract: Recent results of searches for events containing isolated leptons and missing transverse momentum at HERA are presented. Searches in this final state have yielded notable excesses over Standard Model expectations in the past. Searches for isolated leptons in channels corresponding to all three generations of leptons over the full HERA running period are now available. The combined H1+ZEUS results for searches for electrons and muons are compatible with the Standard Model.

title: Study of taupair production at HERA
abstract: A study of events containing two tau leptons with high transverse momentum has been performed with the ZEUS detector at HERA, using a data sample corresponding to an integrated luminosity of 0.33 fb−1. The tau candidates were identified from their decays into electrons, muons or hadronic jets. The number of tau-pair candidates has been compared with the prediction from the Standard Model, where the largest contribution is expected from Bethe-Heitler processes. The total visible cross section was extracted. Standard Model expectations agree well with the measured distributions, also at high invariant mass of the tau pair.

title: Inclusive-jet photoproduction at HERA and determination of alpha(s)
abstract: Inclusive-jet cross sections have been measured in the reaction e p → e + jet + X for photon virtuality Q 2 1 GeV 2 and γp centre-of-mass energies in the region 142 W γ p 293 GeV with the ZEUS detector at HERA using an integrated luminosity of 300 pb − 1 . Jets were identified using the k T , anti- k T or SIScone jet algorithms in the laboratory frame. Single-differential cross sections are presented as functions of the jet transverse energy, E T jet , and pseudorapidity, η jet , for jets with E T jet > 17 GeV and − 1 η jet 2.5 . In addition, measurements of double-differential inclusive-jet cross sections are presented as functions of E T jet in different regions of η jet . Next-to-leading-order QCD calculations give a good description of the measurements, except for jets with low E T jet and high η jet . The influence of non-perturbative effects not related to hadronisation was studied. Measurements of the ratios of cross sections using different jet algorithms are also presented; the measured ratios are well described by calculations including up to O ( α s 2 ) terms. Values of α s ( M Z ) were extracted from the measurements and the energy-scale dependence of the coupling was determined. The value of α s ( M Z ) extracted from the measurements based on the k T jet algorithm is α s ( M Z ) = 0.1206 − 0.0022 + 0.0023 ( exp . ) − 0.0035 + 0.0042 ( th . ) ; the results from the anti- k T and SIScone algorithms are compatible with this value and have a similar precision.

title: On the algebraic types of the Bel–Robinson tensor
abstract: The Bel–Robinson tensor is analyzed as a linear map on the space of the traceless symmetric tensors. This study leads to an algebraic classification that refines the usual Petrov–Bel classification of the Weyl tensor. The new classes correspond to degenerate type I space-times which have already been introduced in literature from another point of view. The Petrov–Bel types and the additional ones are intrinsically characterized in terms of the sole Bel–Robinson tensor, and an algorithm is proposed that enables the different classes to be distinguished. Results are presented that solve the problem of obtaining the Weyl tensor from the Bel–Robinson tensor in regular cases.

title: Obtaining the Weyl tensor from the Bel–Robinson tensor
abstract: The algebraic study of the Bel–Robinson tensor proposed and initiated in a previous work (Ferrando and Sáez in Gen Relativ Gravit 41:1695–1715, 2009) is achieved. The canonical form of the different algebraic types is obtained in terms of Bel–Robinson eigen-tensors. An algorithmic determination of the Weyl tensor from the Bel–Robinson tensor is presented.

title: SiPMs coated with TPB: coating protocol and characterization for NEXT
abstract: Silicon photomultipliers (SiPM) are the photon detectors chosen for the tracking readout in NEXT, a neutrinoless \bb decay experiment which uses a high pressure gaseous xenon time projection chamber (TPC). The reconstruction of event track and topology in this gaseous detector is a key handle for background rejection. Among the commercially available sensors that can be used for tracking, SiPMs offer important advantages, mainly high gain, ruggedness, cost-effectiveness and radio-purity. Their main drawback, however, is their non sensitivity in the emission spectrum of the xenon scintillation (peak at 175 nm). This is overcome by coating these sensors with the organic wavelength shifter tetraphenyl butadiene (TPB). In this paper we describe the protocol developed for coating the SiPMs with TPB and the measurements performed for characterizing the coatings as well as the performance of the coated sensors in the UV-VUV range.

title: On the Bel radiative gravitational fields
abstract: We analyze the concept of intrinsic radiative gravitational fields defined by Bel and we show that the three radiative types, N, III and II, correspond with the three following different physical situations: pure radiation, asymptotic pure radiation and generic (non-pure, non-asymptotic pure) radiation. We introduce the concept of observer at rest with respect to the gravitational field and that of proper super-energy of the gravitational field and we show that, for non-radiative fields, the minimum value of the relative super-energy density is the proper super-energy density, which is acquired by the observers at rest with respect to the field. Several super-energy inequalities are also examined.

title: On the space-times admitting two shear-free geodesic null congruences
abstract: We analyze the space-times admitting two shear-free geodesic null congruences. The integrability conditions are presented in a plain tensorial way as equations on the volume element U of the time-like 2-plane that these directions define. From these we easily deduce significant consequences. We obtain explicit expressions for the Ricci and Weyl tensors in terms of U and its first and second order covariant derivatives. We study the different compatible Petrov-Bel types and give the necessary and sufficient conditions that characterize every type in terms of U. The type D case is analyzed in detail and we show that every type D space-time admitting a 2 + 2 conformal Killing tensor also admits a conformal Killing-Yano tensor.