David Alvarez

© 2016, CERN for the benefit of the ATLAS collaboration.The number of charged particles inside jets is a widely used discriminant for identifying the quark or gluon nature of the initiating parton and is sensitive to both the perturbative and non-perturbative components of fragmentation. This paper presents a measurement of the average number of charged particles with >500 pT> 500 {\mathrm{MeV}} MeV inside high-momentum jets in dijet events using 20.3 fb-1 of data recorded with the ATLAS detector in pp collisions at √s = 8 TeV collisions at the LHC. The jets considered have transverse momenta from 50 GeV up to and beyond 1.5 TeV. The reconstructed charged-particle track multiplicity distribution is unfolded to remove distortions from detector effects and the resulting charged-particle multiplicity is compared to several models. Furthermore, quark and gluon jet fractions are used to extract the average charged-particle multiplicity for quark and gluon jets separately.

© 2017, The Author.Ratios of top-quark pair to Z-boson cross sections measured from proton-proton collisions at the LHC centre-of-mass energies of s=13 TeV, 8 TeV, and 7 TeV are presented by the ATLAS Collaboration. Single ratios, at a given s for the two processes and at different s for each process, as well as double ratios of the two processes at different s, are evaluated. The ratios are constructed using previously published ATLAS measurements of the tt¯ and Z-boson production cross sections, corrected to a common phase space where required, and a new analysis of Z → ℓ+ℓ− where ℓ = e, μ at s=13 TeV performed with data collected in 2015 with an integrated luminosity of 3.2 fb−1. Correlations of systematic uncertainties are taken into account when evaluating the uncertainties in the ratios. The correlation model is also used to evaluate the combined cross section of the Z → e+e− and the Z → μ+μ− channels for each s value. The results are compared to calculations performed at next-to-next-to-leading-order accuracy using recent sets of parton distribution functions. The data demonstrate significant power to constrain the gluon distribution function for the Bjorken-x values near 0.1 and the light-quark sea for x < 0.02.[Figure not available: see fulltext.]

© 2016, The Author.A search for neutral Higgs bosons of the minimal supersymmetric standard model and for a heavneutral Z′ boson is performed using a data sample corresponding to an integrated luminosity of 3.2 fb- 1 from proton–proton collisions at s=13 TeV recorded by the ATLAS detector at the LHC. The heavy resonance is assumed to decay to a τ+τ- pair with at least one τ lepton decaying to final states with hadrons and a neutrino. The search is performed in the mass range of 0.2–1.2 TeV for the MSSM neutral Higgs bosons and 0.5–2.5 TeV for the heavy neutral Z′ boson. The data are in good agreement with the background predicted by the Standard Model. The results are interpreted in MSSM and Z′ benchmark scenarios. The most stringent constraints on the MSSM mA–tan β space exclude at 95 % confidence level tan β> 7.6 for mA= 200 GeV in the mhmod+ MSSM scenario. For the Sequential Standard Model, a ZSSM′ mass up to 1.90 TeV is excluded at 95 % CL and masses up to 1.82–2.17 TeV are excluded for a ZSFM′ of the strong flavour model.

© 2017, The Author.A measurement of the ZZ production cross section in the ℓ−ℓ+ℓ′ −ℓ′ + and ℓ−ℓ+νν¯ channels in proton-proton collisions at s=8TeV at the Large Hadron Collider at CERN, using data corresponding to an integrated luminosity of 20.3 fb−1 collected by the ATLAS experiment in 2012 is presented. The fiducial cross sections for ZZ → ℓ−ℓ+ℓ′ −ℓ′ + and ZZ→ ℓ−ℓ+νν¯ are measured in selected phase-space regions. The total cross section for ZZ events produced with both Z bosons in the mass range 66 to 116 GeV is measured from the combination of the two channels to be 7.3 ± 0.4 ± 0.3− 0.1− 0.2 pb, which is consistent with the Standard Model prediction of 6. 6− 0.6+ 0.7 pb. The differential cross sections in bins of various kinematic variables are presented. The differential event yield as a function of the transverse momentum of the leading Z boson is used to set limits on anomalous neutral triple gauge boson couplings in ZZ production.[Figure not available: see fulltext.]

© 2017, CERN for the benefit of the ATLAS collaboration.This paper presents a measurement of the polarisation of W bosons from tt¯ decays, reconstructed in events with one high-pT lepton and at least four jets. Data from pp collisions at the LHC were collected at s = 8 TeV and correspond to an integrated luminosity of 20.2 fb- 1. The angle θ∗ between the b-quark from the top quark decay and a direct W boson decay product in the W boson rest frame is sensitive to the W boson polarisation. Two different W decay products are used as polarisation analysers: the charged lepton and the down-type quark for the leptonically and hadronically decaying W boson, respectively. The most precise measurement of the W boson polarisation via the distribution of cos θ∗ is obtained using the leptonic analyser and events in which at least two of the jets are tagged as b-quark jets. The fitted fractions of longitudinal, left- and right-handed polarisation states are F0=0.709±0.019, FL=0.299±0.015 and FR=-0.008±0.014, and are the most precisely measured W boson polarisation fractions to date. Limits on anomalous couplings of the Wtb vertex are set.

© 2017, CERN for the benefit of the ATLAS collaboration.A measurement of the tt¯ Z and tt¯ W production cross sections in final states with either two same-charge muons, or three or four leptons is presented. The analysis uses a data sample of proton–proton collisions at s=13 TeV recorded with the ATLAS detector at the Large Hadron Collider in 2015, corresponding to a total integrated luminosity of 3.2 fb- 1. The inclusive cross sections are extracted using likelihood fits to signal and control regions, resulting in σtt¯Z= 0.9 ± 0.3 pb and σtt¯W= 1.5 ± 0.8 pb, in agreement with the Standard Model predictions.

© 2017, The Author.Same- and opposite-sign charge asymmetries are measured in lepton+jets tt¯ events in which a b-hadron decays semileptonically to a soft muon, using data corresponding to an integrated luminosity of 20.3 fb−1 from proton-proton collisions at a centre-of-mass energy of s=√8 TeV collected with the ATLAS detector at the Large Hadron Collider at CERN. The charge asymmetries are based on the charge of the lepton from the top-quark decay and the charge of the soft muon from the semileptonic decay of a b-hadron and are measured in a fiducial region corresponding to the experimental acceptance. Four CP asymmetries are measured and are found to be compatible with zero and consistent with the Standard Model.[Figure not available: see fulltext.]

© 2017, CERN for the benefit of the ATLAS collaboration.The production of two prompt J/ ψ mesons, each with transverse momenta pT> 8.5 GeV and rapidity |y| < 2.1, is studied using a sample of proton-proton collisions at s=8 TeV, corresponding to an integrated luminosity of 11.4 fb- 1 collected in 2012 with the ATLAS detector at the LHC. The differential cross-section, assuming unpolarised J/ ψ production, is measured as a function of the transverse momentum of the lower-pTJ/ ψ meson, di-J/ ψpT and mass, the difference in rapidity between the two J/ ψ mesons, and the azimuthal angle between the two J/ ψ mesons. The fraction of prompt pair events due to double parton scattering is determined by studying kinematic correlations between the two J/ ψ mesons. The total and double parton scattering cross-sections are compared with predictions. The effective cross-section of double parton scattering is measured to be σeff= 6.3 ± 1.6 ± 1.0 mb.

© 2017, The Author.Differential cross sections are presented for the prompt and non-prompt production of the hidden-charm states X and ψ, in the decay mode J/ψπ+π−, measured using 11.4 fb−1 of pp collisions at s=8 TeV by the ATLAS detector at the LHC. The ratio of cross-sections X/ψ is also given, separately for prompt and non-prompt components, as well as the non-prompt fractions of X and ψ. Assuming independent single effective lifetimes for non-prompt X and ψ production gives RB=ℬ+any)ℬ→J/ψπ+π−)/ℬ+any)ℬ→J/ψπ+π−)=±0.08)×10−2 separating short- and long-lived contributions, assuming that the short-lived component is due to Bc decays, gives RB = ± 0.11) × 10−2, with the fraction of non-prompt X produced via Bc decays for pT) > 10 GeV being ± 2 ± 5)%. The distributions of the dipion invariant mass in the X and ψ decays are also measured and compared to theoretical predictions.[Figure not available: see fulltext.]

En su obra The Idea of Justice, Amartya Sen expone una crítica a lo que denomina «teoría transcendental de la justicia», argumentando que su papel resulta irrelevante para guiar las acciones requeridas para combatir la injusticia en condiciones no-ideales. En este trabajo exploramos una posible relación de compatibilidad entre el enfoque comparativo auspiciado por Sen y un marco mínimo transcendental de justicia global que constriña las elecciones para evitar trayectorias institucionales que desemboquen en escenarios incompatibles con las concepciones de justicia que generaron las evaluaciones originales.

Tras comparar la concepción de Risse de Propiedad Común de la Tierra (PCT) con otras alternativas teóricas de redistribución global (Steiner, Pogge) o de reformulación de los derechos humanos en términos de membrecía (Cohen, Benhabib), concluimos que PCT, como teoría de justicia distributiva global, defiende un umbral innecesariamente bajo; y como concepción de derechos humanos no fundamenta con robustez las garantías socioeconómicas. Finalmente, la especificación de los derechos humanos a partir de la membrecía global no es traducible a términos de «derecho a no-exclusión de la nueva propiedad pública» (Sachar), ya que la condición de subsistencia de los derechos humanos no implica necesariamente la condición de independencia del estatus de co-propietario original. Así pues, esta derivación contingente de los derechos humanos no cumple la condición de transitividad exigida por sus requisitos internos de justificación.

The main thesis can be summarized the following way: If freedom-status is the master good for republicans then, when democratic participation and mandatory citizenship undermine the self-respect of permanent minorities, self-alienation becomes a political status compatible with the republican ideal of freedom as non-domination. By self-alienation I understand the voluntary withdrawal of active democratic participation, the rejection of national membership as citizen, and the assumption of the status of permanent resident. The paper argues that permanent residency and national citizenship must be conceived as equivalent statuses in terms of non-domination and therefore, as compatible forms of democratic equality.

This article analyses the problems of the transition from a modus vivendi to a moral conception of toleration and its extension to the international realm in the work of John Rawls. This essay starts from conceptual problems implicit in the experience of the European Reform, an inspiring historical event in the emergence of political liberalism, and analyses its development and accommodation to the current globalized context. Special attention is paid to the problems arising from the commitment with dissenting transformative movements within consultation hierarchies and the demands of tolerant egalitarian recognition by non-liberal societies. We defend that it is possible to hold and alternative reading within this frame. It enables us to explore the potential for reflexive evolution in the Society of Peoples as a realistic utopia. If traditional societies peoples have the capacity to develop modernising «creative adaptations» (alternative modernities), there would be realistic conditions for a thicker global basic structure, a higher degree of international cooperation and channelsinstitutionalise individual rights.

El texto de Tácito sobre el incendio de Roma y la per-secución neroniana constituye uno de los textos más antiguos de la his-toriografía romana sobre los cristia-nos y ha sido objeto de innumerables hipótesis por lo controvertido del mismo. B. Shaw, recientemente, ha considerado la persecución nero-niana de los cristianos como un mito sin base histórica. Este artí-culo aborda los datos de Tácito, así como el impacto que el incendio y la persecución de este empera-dor dejaron en las fuentes cristia-nas. Asimismo, se expone la tesis de B. Shaw, las críticas que se le hanhecho, así como una posible solución

The purpose of this chapter is to examine the limitations of our current political structures in incorporating the cosmopolitan principles that may be emerging in the normative developments of our global order. The perspective that I take is explicitly cosmopolitan, although it is elaborated out of an exercise of immanent criticism from within our existing institutional order. This analysis confronts spaces of the incipient articulation of cosmopolitan realities with political models of international legitimacy. This scenario constitutes an example of the incapacity of national state democracies to give a proper account of their foreign duties through national or supranational institutions. We briefly examine two emerging political sites that partially realize cosmopolitan realities in defiance of the national system. The first case is the political space of our metropoleis and their distinctive disposition towards refugees in Europe. The second case is the emergence of a cross-border network of urban connectivity and the alternative characterization of the refugee flows as a constitutive part in this transnational social fabric.