Alvaro Alonso

© 2016, CERN for the benefit of the ATLAS collaboration.The dijet production cross section for jets containing a b-hadron has been measured in proton–proton collisions with a centre-of-mass energy of s=7 TeV, using the ATLAS detector at the LHC. The data used correspond to an integrated luminosity of 4.2fb-1. The cross section is measured for events with two identified b-jets with a transverse momentum pT> 20 GeV and a minimum separation in the η–ϕ plane of Δ R= 0.4. At least one of the jets in the event is required to have pT> 270 GeV. The cross section is measured differentially as a function of dijet invariant mass, dijet transverse momentum, boost of the dijet system, and the rapidity difference, azimuthal angle and angular distance between the b-jets. The results are compared to different predictions of leading order and next-to-leading order perturbative quantum chromodynamics matrix elements supplemented with models for parton-showers and hadronization.

© CERN for the benefit of the ATLAS collaboration 2011.We present first measurements of charged and neutral particle-flow correlations in pp collisions using the ATLAS calorimeters.Data were collected in 2009 and 2010 at centre-of-mass energies of 900 GeV and 7 TeV.Events were selected using a minimum-bias trigger which required a charged particle in scintillation counters on either side of the interaction point.Particle flows, sensitive to the underlying event, are measured using clusters of energy in the ATLAS calorimeters, taking advantage of their fine granularity.No Monte Carlo generator used in this analysis can accurately describe the measurements.The results are independent of those based on charged particles measured by the ATLAS tracking systems and can be used to constrain the parameters of Monte Carlo generators.

© 2014, The Author.: A search for the neutral Higgs bosons predicted by the Minimal Supersymmetric Standard Model is reported. The analysis is performed on data from proton-proton collisions at a centre-of-mass energy of 8 TeV collected with the ATLAS detector at the Large Hadron Collider. The samples used for this search were collected in 2012 and correspond to integrated luminosities in the range 19.5-20.3 fb−1. The MSSM Higgs bosons are searched for in the τ τ final state. No significant excess over the expected background is observed, and exclusion limits are derived for the production cross section times branching fraction of a scalar particle as a function of its mass. The results are also interpreted in the MSSM parameter space for various benchmark scenarios.

© 2014, The Author.: A search is presented for the production of new heavy quarks that decay to a Z boson and a third-generation Standard Model quark. In the case of a new charge +2/3 quark, the decay targeted is T → Zt, while the decay targeted for a new charge −1/3 quark is B → Zb. The search is performed with a dataset corresponding to 20.3 fb −1 of pp collisions at TeV recorded in 2012 with the ATLAS detector at the CERN Large Hadron Collider. Selected events contain a high transverse momentum Z boson candidate reconstructed from a pair of oppositely charged same-flavor leptons, and are analyzed in two channels defined by the absence or presence of a third lepton. Hadronic jets, in particular those with properties consistent with the decay of a b-hadron, are also required to be present in selected events. Different requirements are made on the jet activity in the event in order to enhance the sensitivity to either heavy quark pair production mediated by the strong interaction, or single production mediated by the electroweak interaction. No significant excess of events above the Standard Model expectation is observed, and lower limits are derived on the mass of vector-like T and B quarks under various branching ratio hypotheses, as well as upper limits on the magnitude of electroweak coupling parameters.

© 2015, The Author.: The production of a W boson decaying to eν or μν in association with a W or Z boson decaying to two jets is studied using 4.6 fb−1 of proton-proton collision data at √s =7 TeV recorded with the ATLAS detector at the LHC. The combined WW + WZ cross section is measured with a significance of 3.4σ and is found to be 68±7 ±19 pb, in agreement with the Standard Model expectation of 61.1±2.2 pb. The distribution of the transverse momentum of the dijet system is used to set limits on anomalous contributions to the triple gauge coupling vertices and on parameters of an effective-field-theory model.[Figure not available: see fulltext.]

BackgroundAdvance directives imply the promise of determining future medical treatment in case of decisional incapacity. However, clinical practice increasingly indicates that standardized ADs often fail to support patients’ autonomy. To date, little data are available about the quality and impact of ADs on end-of-life decisions for incapacitated acute stroke patients.MethodsWe analyzed the ADs of patients with fatal stroke, focusing on: their availability and type, stated circumstances to which the AD should apply, and stated wishes regarding specific treatment options.ResultsBetween 2011 and 2014, 143 patients died during their hospitalization on our stroke unit. Forty-two of them had a completed and signed, written AD, as reported by their family, but only 35 ADs were available. The circumstances in which the AD should apply were stated by 21/35 as a “terminal condition that will cause death within a relatively short time” or an ongoing “dying process.” A retrospective review found only 16 of 35 ADs described circumstances that, according to the medical file, could have been considered applicable by the treating physicians. A majority of patients objected to cardiopulmonary resuscitation, mechanical ventilation, and artificial nutrition, while almost all directed that treatment for alleviation of pain or discomfort should be provided at all times even if it could hasten death.ConclusionsThe prevalence of ADs among patients who die from acute stroke is still low. A major flaw of the ADs in our cohort was their attempt to determine single medical procedures without focusing on a precise description of applicable scenarios. Therefore, less than half of the ADs were considered applicable for severe acute stroke. These findings stress the need to foster educational programs for the general public about advance care planning to facilitate the processing of timely, comprehensive, and individualized end-of-life decision-making.