Measurement of the cross-section for b-jets produced in association with a Z boson at root s=7 TeV with the ATLAS detector ATLAS Collaboration

A measurement is presented of the inclusive cross-section for b-jet production in association with a Z boson in pp collisions at a centre-of-mass energy of root s = 7 TeV. The analysis uses the data sample collected by the ATLAS experiment in 2010, corresponding to an integrated luminosity of approximately 36 pb(-1). The event selection requires a Z boson decaying into high P-T electrons or muons, and at least one b-jet, identified by its displaced vertex, with transverse momentum p(T) > 25 GeV and rapidity vertical bar y vertical bar < 2.1. After subtraction of background processes, the yield is extracted from the vertex mass distribution of the candidate b-jets. The ratio of this cross-section to the inclusive Z cross-section (the average number of b-jets per Z event) is also measured. Both results are found to be in good agreement with perturbative QCD predictions at next-to-leading order

The embryo as moral work object: PGD/IVF staff views and experiences

Copyright @ 2008 the authors. This article is available in accordance with the Creative Commons Deed, Attribution 2.5, see http://creativecommons.org/licenses/by-nc-nd/2.5/deed.en_CA.We report on one aspect of a study that explored the views and experiences of practitioners and scientists on social, ethical and clinical dilemmas encountered when working in the field of preimplantation genetic diagnosis (PGD) for serious genetic disorders. The study produced an ethnography based on observation, interviews and ethics discussion groups with staff from two PGD/IVF Units in the UK. We focus here on staff perceptions of work with embryos that entails disposing of ‘affected’ or ‘spare’ embryos or using them for research. A variety of views were expressed on the ‘embryo question’ in contrast to polarised media debates. We argue that the prevailing policy acceptance of destroying affected embryos, and allowing research on embryos up to 14 days leaves some staff with rarely reported, ambivalent feelings. Staff views are under-researched in this area and we focus on how they may reconcile their personal moral views with the ethical framework in their field. Staff construct embryos in a variety of ways as ‘moral work objects’. This allows them to shift attention between micro-level and overarching institutional work goals, building on Casper's concept of ‘work objects’ and focusing on negotiation of the social order in a morally contested field.The Wellcome Trust Biomedical Ethics Programme, who funded the projects‘Facilitating choice, framing choice: the experience of staff working in pre-implantation genetic diagnosis’ (no: 074935), and ‘Ethical Frameworks for Embryo Donation:the views and practices of IVF/PGD staff’ (no: 081414)

Search for WH production with a light Higgs boson decaying to prompt electron-jets in proton-proton collisions at s\sqrt{s}=7 TeV with the ATLAS detector

A search is performed for WH production with a light Higgs boson decaying to hidden-sector particles resulting in clusters of collimated electrons, known as electron-jets. The search is performed with 2.04 fb-1 of data collected in 2011 with the ATLAS detector at the LHC in proton-proton collisions at $\sqrt{s}$=7 TeV. One event satisfying the signal selection criteria is observed, which is consistent with the expected background rate. Limits on the product of the WH production cross section and the branching ratio of a Higgs boson decaying to prompt electron-jets are calculated as a function of a Higgs boson mass in the range from 100 GeV to 140 GeV.Peer Reviewe

Measurement of flow harmonics with multi-particle cumulants in Pb plus Pb collisions at root(NN)-N-S=2.76 TeV with the ATLAS detector

ATLAS measurements of the azimuthal anisotropy in lead-lead collisions at root(NN)-N-S = 2.76 TeV are shown using a dataset of approximately 7 mu b(-1) collected at the LHC in 2010. The measurements are performed for charged particles with transverse momenta 0.5 < p(T) < 20 GeV and in the pseudorapidity range vertical bar eta vertical bar < 2.5. The anisotropy is characterized by the Fourier coefficients, vn, of the charged-particle azimuthal angle distribution for n = 2-4. The Fourier coefficients are evaluated using multi-particle cumulants calculated with the generating function method. Results on the transverse momentum, pseudorapidity and centrality dependence of the v(n) coefficients are presented. The elliptic flow, v(2), is obtained from the two-, four-, six-and eight-particle cumulants while higher-order coefficients, v(3) and v(4), are determined with two-and four-particle cumulants. Flow harmonics v(n) measured with four-particle cumulants are significantly reduced compared to the measurement involving two-particle cumulants. A comparison to v(n) measurements obtained using different analysis methods and previously reported by the LHC experiments is also shown. Results of measurements of flow fluctuations evaluated with multiparticle cumulants are shown as a function of transverse momentum and the collision centrality. Models of the initial spatial geometry and its fluctuations fail to describe the flow fluctuations measurements

Performance of the ATLAS track reconstruction algorithms in dense environments in LHC Run 2

With the increase in energy of the Large Hadron Collider to a centre-of-mass energy of 13 TeV for Run 2, events with dense environments, such as in the cores of highenergy jets, became a focus for new physics searches as well as measurements of the Standard Model. These environments are characterized by charged-particle separations of the order of the tracking detectors sensor granularity. Basic track quantities are compared between 3.2 fb(-1) of data collected by the ATLAS experiment and simulation of protonproton collisions producing high-transverse-momentum jets at a centre-of-mass energy of 13 TeV. The impact of chargedparticle separations and multiplicities on the track reconstruction performance is discussed. The track reconstruction efficiency in the cores of jets with transverse momenta between 200 and 1600 GeV is quantified using a novel, datadriven, method. The method uses the energy loss, dE/ dx, to identify pixel clusters originating from two charged particles. Of the charged particles creating these clusters, themeasured fraction that fail to be reconstructed is 0.061 +/- 0.006 (stat.) +/- 0.014 (syst.) and 0.093 +/- 0.017 (stat.) +/- 0.021 (syst.) for jet transverse momenta of 200-400GeV and 1400-1600GeV, respectively

Measurement of the W(+/-)Z production cross section and limits on anomalous triple gauge couplings in proton-proton collisions at root s=7 TeV with the ATLAS detector

This Letter presents a measurement of W(+/-)Z production in 1.02 fb(-1) of pp collision data at root s = 7 TeV collected by the ATLAS experiment in 2011. Doubly leptonic decay events are selected with electrons, muons and missing transverse momentum in the final state. In total 71 candidates are observed, with a background expectation of 12.1 +/- 1.4(stat.)(-2.0)(+4.1)(syst.) events. The total cross section for W(+/-)Z production for Z/gamma* masses within the range 66 GeV to 116 GeV is determined to be sigma(tot)(WZ) = 20.5(-2.8)(+3.1)(stat.)(-1.3)(+1.4)(syst)(-0.8)(+0.9)(lumi.) pb, which is consistent with the Standard Model expectation of 17.3(0.8)(+1.3) pb. Limits on anomalous triple gauge boson couplings are extracted. (C) 2012 CERN. Published by Elsevier B.V. All rights reserved. RI Doyle, Anthony/C-5889-2009; Pina, Joao /C-4391-2012; Li, Xuefei/C-3861-2012; Fazio, Salvatore /G-5156-2010; Smirnova, Lidia/D-8089-2012; Sivoklokov, Sergey/D-8150-2012; Smirnov, Sergei/F-1014-2011; Gladilin, Leonid/B-5226-2011; Barreiro, Fernando/D-9808-2012; Kramarenko, Victor/E-1781-2012; Prokoshin, Fedor/E-2795-2012; valente, paolo/A-6640-2010; Alexa, Calin/F-6345-2010; Gutierrez, Phillip/C-1161-2011; Pacheco Pages, Andres/C-5353-2011; Moorhead, Gareth/B-6634-2009; Livan, Michele/D-7531-2012; Takai, Helio/C-3301-2012; Petrucci, Fabrizio/G-8348-2012; Wemans, Andre/A-6738-2012; Jones, Roger/H-5578-2011; Fabbri, Laura/H-3442-2012; Kurashige, Hisaya/H-4916-2012; Villa, Mauro/C-9883-2009; Delmastro, Marco/I-5599-201

Measurement of flow harmonics with multi-particle cumulants in Pb plus Pb collisions at root(NN)-N-S=2.76 TeV with the ATLAS detector

ATLAS measurements of the azimuthal anisotropy in lead-lead collisions at root(NN)-N-S = 2.76 TeV are shown using a dataset of approximately 7 mu b(-1) collected at the LHC in 2010. The measurements are performed for charged particles with transverse momenta 0.5 < p(T) < 20 GeV and in the pseudorapidity range vertical bar eta vertical bar < 2.5. The anisotropy is characterized by the Fourier coefficients, vn, of the charged-particle azimuthal angle distribution for n = 2-4. The Fourier coefficients are evaluated using multi-particle cumulants calculated with the generating function method. Results on the transverse momentum, pseudorapidity and centrality dependence of the v(n) coefficients are presented. The elliptic flow, v(2), is obtained from the two-, four-, six-and eight-particle cumulants while higher-order coefficients, v(3) and v(4), are determined with two-and four-particle cumulants. Flow harmonics v(n) measured with four-particle cumulants are significantly reduced compared to the measurement involving two-particle cumulants. A comparison to v(n) measurements obtained using different analysis methods and previously reported by the LHC experiments is also shown. Results of measurements of flow fluctuations evaluated with multiparticle cumulants are shown as a function of transverse momentum and the collision centrality. Models of the initial spatial geometry and its fluctuations fail to describe the flow fluctuations measurements

Search for Dark Matter Candidates and Large Extra Dimensions in Events with a Photon and Missing Transverse Momentum in pp Collision Data at root s=7 TeV with the ATLAS Detector

"Results of a search for new phenomena in events with an energetic photon and large missing transverse momentum in proton-proton collisions at root s = 7 TeV are reported. Data collected by the ATLAS experiment at the LHC corresponding to an integrated luminosity of 4.6 fb(-1) are used. Good agreement is observed between the data and the standard model predictions. The results are translated into exclusion limits on models with large extra spatial dimensions and on pair production of weakly interacting dark matter candidates. DOI: 10.1103\/PhysRevLett.110.011802