SwePub
Sök i SwePub databas

  Utökad sökning

Träfflista för sökning "LAR1:lu ;lar1:(kth);pers:(Moa Torbjörn)"

Sökning: LAR1:lu > Kungliga Tekniska Högskolan > Moa Torbjörn

Sortera/gruppera träfflistan
   
NumreringReferensOmslagsbildHitta
1.
  • Aad, G., et al. (författare)
  • A neural network clustering algorithm for the ATLAS silicon pixel detector
  • 2014
  • Ingår i: Journal of Instrumentation. - IOP Publishing. - 1748-0221. ; 9, s. P09009
  • Tidskriftsartikel (refereegranskat)abstract
    • A novel technique to identify and split clusters created by multiple charged particles in the ATLAS pixel detector using a set of artificial neural networks is presented. Such merged clusters are a common feature of tracks originating from highly energetic objects, such as jets. Neural networks are trained using Monte Carlo samples produced with a detailed detector simulation. This technique replaces the former clustering approach based on a connected component analysis and charge interpolation. The performance of the neural network splitting technique is quantified using data from proton-proton collisions at the LHC collected by the ATLAS detector in 2011 and from Monte Carlo simulations. This technique reduces the number of clusters shared between tracks in highly energetic jets by up to a factor of three. It also provides more precise position and error estimates of the clusters in both the transverse and longitudinal impact parameter resolution.
2.
  • Aad, G., et al. (författare)
  • A search for prompt lepton-jets in pp collisions at root s=7 TeV with the ATLAS detector
  • 2013
  • Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - Elsevier. - 0370-2693. ; 719:4-5, s. 299-317
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a search for a light (mass < 2 GeV) boson predicted by Hidden Valley supersymmetric models that decays into a final state consisting of collimated muons or electrons, denoted "lepton-jets". The analysis uses 5 fb(-1) of root s = 7 TeV proton-proton collision data recorded by the ATLAS detector at the Large Hadron Collider to search for the following signatures: single lepton-jets with at least four muons; pairs of lepton-jets, each with two or more muons; and pairs of lepton-jets with two or more electrons. This study finds no statistically significant deviation from the Standard Model prediction and places 95% confidence-level exclusion limits on the production cross section times branching ratio of light bosons for several parameter sets of a Hidden Valley model. (c) 2013 CERN. Published by Elsevier B.V. All rights reserved.
3.
  • Aad, G., et al. (författare)
  • A search for t(t)over-bar resonances using lepton-plus-jets events in proton-proton collisions at root s=8 TeV with the ATLAS detector
  • 2015
  • Ingår i: Journal of High Energy Physics. - Springer. - 1029-8479 .- 1126-6708. ; :8, s. 148
  • Tidskriftsartikel (refereegranskat)abstract
    • A search for new particles that decay into top quark pairs is reported. The search is performed with the ATLAS experiment at the LHC using an integrated luminosity of 20.3 fb(-1) of proton-proton collision data collected at a centre-of-mass energy of root s = 8TeV. The lepton-plus-jets final state is used, where the top pair decays to W (+) bW(-)(b) over bar, with one W boson decaying leptonically and the other hadronically. The invariant mass spectrum of top quark pairs is examined for local excesses or deficits that are inconsistent with the Standard Model predictions. No evidence for a top quark pair resonance is found, and 95% confidence-level limits on the production rate are determined for massive states in benchmark models. The upper limits on the cross-section times branching ratio of a narrow Z' boson decaying to top pairs range from 4.2 pb to 0.03 pb for resonance masses from 0.4 TeV to 3.0 TeV. A narrow leptophobic topcolour Z' boson with mass below 1.8 TeV is excluded. Upper limits are set on the cross-section times branching ratio for a broad colour-octet resonance with Gamma/m = 15% decaying to tt. These range from 4.8 pb to 0.03 pb for masses from 0.4 TeV to 3.0 TeV. A Kaluza-Klein excitation of the gluon in a Randall-Sundrum model is excluded for masses below 2.2 TeV.
4.
  • Aad, G., et al. (författare)
  • Combined search for the Standard Model Higgs boson in pp collisions at root s=7 TeV with the ATLAS detector
  • 2012
  • Ingår i: Physical Review D (Particles, Fields, Gravitation and Cosmology). - American Physical Society. - 1550-7998 .- 1550-2368. ; 86:3, s. 032003
  • Tidskriftsartikel (refereegranskat)abstract
    • A combined search for the Standard Model Higgs boson with the ATLAS detector at the LHC is presented. The data sets used correspond to integrated luminosities from 4.6 fb(-1) to 4.9 fb(-1) of proton-proton collisions collected at root s = 7 TeV in 2011. The Higgs boson mass ranges of 111.4 GeV to 116.6 GeV, 119.4 GeV to 122.1 GeV, and 129.2 GeV to 541 GeV are excluded at the 95% confidence level, while the range 120 GeV to 560 GeV is expected to be excluded in the absence of a signal. An excess of events is observed at Higgs boson mass hypotheses around 126 GeV with a local significance of 2.9 standard deviations (sigma). The global probability for the background to produce an excess at least as significant anywhere in the entire explored Higgs boson mass range of 110-600 GeV is estimated to be similar to 15%, corresponding to a significance of approximately 1 sigma.
5.
  • Aad, G, et al. (författare)
  • Drift Time Measurement in the ATLAS Liquid Argon Electromagnetic Calorimeter using Cosmic Muons
  • 2010
  • Ingår i: European Physical Journal C. Particles and Fields. - Springer. - 1434-6044. ; 70:3, s. 755-785
  • Tidskriftsartikel (refereegranskat)abstract
    • The ionization signals in the liquid argon of the ATLAS electromagnetic calorimeter are studied in detail using cosmic muons. In particular, the drift time of the ionization electrons is measured and used to assess the intrinsic uniformity of the calorimeter gaps and estimate its impact on the constant term of the energy resolution. The drift times of electrons in the cells of the second layer of the calorimeter are uniform at the level of 1.3% in the barrel and 2.8% in the endcaps. This leads to an estimated contribution to the constant term of (0.29(-0.04)(+0.05))% in the barrel and (0.54(-0.04)(+0.06))% in the endcaps. The same data are used to measure the drift velocity of ionization electrons in liquid argon, which is found to be 4.61 +/- 0.07 mm/mu s at 88.5 K and 1 kV/mm.
6.
  • Aad, G, et al. (författare)
  • Electron reconstruction and identification efficiency measurements with the ATLAS detector using the 2011 LHC proton-proton collision data
  • 2014
  • Ingår i: European Physical Journal C. Particles and Fields. - Springer. - 1434-6044. ; 74:7
  • Tidskriftsartikel (refereegranskat)abstract
    • Many of the interesting physics processes to be measured at the LHC have a signature involving one or more isolated electrons. The electron reconstruction and identification efficiencies of the ATLAS detector at the LHC have been evaluated using proton-proton collision data collected in 2011 at TeV and corresponding to an integrated luminosity of 4.7 fb. Tag-and-probe methods using events with leptonic decays of and bosons and mesons are employed to benchmark these performance parameters. The combination of all measurements results in identification efficiencies determined with an accuracy at the few per mil level for electron transverse energy greater than 30 GeV.
7.
  • Aad, G., et al. (författare)
  • Flavor tagged time-dependent angular analysis of the B-s(0) -> J/psi phi decay and extraction of Delta Gamma(s) and the weak phase phi(s) in ATLAS
  • 2014
  • Ingår i: Physical Review D (Particles, Fields, Gravitation and Cosmology). - American Physical Society. - 1550-7998 .- 1550-2368. ; 90:5, s. 052007
  • Tidskriftsartikel (refereegranskat)abstract
    • A measurement of the B-s(0) -> J/psi phi decay parameters, updated to include flavor tagging is reported using 4.9 fb(-1) of integrated luminosity collected by the ATLAS detector from root s = 7 TeV pp collisions recorded in 2011 at the LHC. The values measured for the physical parameters are phi(s) = 0.12 +/- 0.25(stat) +/- 0.05(syst) rad Delta Gamma(s) = 0.053 +/- 0.021(stat) +/- 0.010(syst) ps(-1) Gamma(s) = 0.677 +/- 0.007(stat) +/- 0.004(syst) ps(-1) vertical bar A(parallel to)(0)vertical bar(2) = 0.220 +/- 0.008(stat) +/- 0.009(syst) vertical bar A(0)(0)vertical bar(2) = 0.529 +/- 0.006(stat) +/- 0.012(syst) delta(perpendicular to) = 3.89 +/- 0.47(stat) +/- 0.11(syst) rad where the parameter Delta Gamma(s) is constrained to be positive. The S-wave contribution was measured and found to be compatible with zero. Results for phi(s) and Delta Gamma(s) are also presented as 68% and 95% likelihood contours, which show agreement with the Standard Model expectations.
8.
  • Aad, G., et al. (författare)
  • Hunt for new phenomena using large jet multiplicities and missing transverse momentum with ATLAS in 4.7fb(-1) of root s=7 TeV proton-proton collisions
  • 2012
  • Ingår i: Journal of High Energy Physics. - Springer. - 1126-6708 .- 1029-8479. ; :7, s. 167
  • Tidskriftsartikel (refereegranskat)abstract
    • Results are presented of a search for new particles decaying to large numbers of jets in association with missing transverse momentum, using 4.7 fb(-1) of pp collision data at root s = 7 TeV collected by the ATLAS experiment at the Large Hadron Collider in 2011. The event selection requires missing transverse momentum, no isolated electrons or muons, and from >= 6 to >= 9 jets. No evidence is found for physics beyond the Standard Model. The results are interpreted in the context of a MSUGRA/CMSSM supersymmetric model, where, for large universal scalar mass m(0), gluino masses smaller than 840 GeV are excluded at the 95% confidence level, extending previously published limits. Within a simplified model containing only a gluino octet and a neutralino, gluino masses smaller than 870 GeV are similarly excluded for neutralino masses below 100 GeV.
9.
  • Aad, G., et al. (författare)
  • Measurement of charged-particle spectra in Pb plus Pb collisions at root s(NN)=2.76 TeV with the ATLAS detector at the LHC
  • 2015
  • Ingår i: Journal of High Energy Physics. - Springer. - 1029-8479 .- 1126-6708. ; :9, s. 050
  • Tidskriftsartikel (refereegranskat)abstract
    • Charged-particle spectra obtained in Pb+Pb interactions at root s(NN) = 2.76TeV and pp interactions at root s(NN) = 2.76TeV with the ATLAS detector at the LHC are presented, using data with integrated luminosities of 0.15 nb(-1) and 4.2 pb(-1), respectively, in a wide transverse momentum (0.5 < p(T) < 150 GeV) and pseudorapidity (vertical bar eta vertical bar < 2) range. For Pb+Pb collisions, the spectra are presented as a function of collision centrality, which is determined by the response of the forward calorimeters located on both sides of the interaction point. The nuclear modification factors R-AA and R-CP are presented in detail as a function of centrality, p(T) and eta. They show a distinct p(T)-dependence with a pronounced minimum at about 7 GeV. Above 60 GeV, R-AA is consistent with a plateau at a centrality-dependent value, within the uncertainties. The value is 0.55 +/- 0.01(stat.) +/- 0.04(syst.) in the most central collisions. The R-AA distribution is consistent with flat vertical bar eta vertical bar dependence over the whole transverse momentum range in all centrality classes.
10.
  • Aad, G., et al. (författare)
  • 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
  • 2014
  • Ingår i: European Physical Journal C. Particles and Fields. - Springer. - 1434-6044. ; 74:11, s. 3157
  • Tidskriftsartikel (refereegranskat)abstract
    • 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.
Skapa referenser, mejla, bekava och länka
Åtkomst
fritt online (193)
Typ av publikation
tidskriftsartikel (217)
Typ av innehåll
refereegranskat (217)
Författare/redaktör
Abbott, B. (217)
Abolins, M. (217)
Abramowicz, H. (217)
Abreu, H. (217)
Adye, T. (217)
Ahlen, S. P. (217)
visa fler...
Akimov, A. V. (217)
Aleksa, M. (217)
Aleksandrov, I. N. (217)
Allport, P. P. (217)
Amako, K. (217)
Amelung, C. (217)
Anastopoulos, C. (217)
Anderson, K. J. (217)
Antonelli, M. (217)
Arabidze, G. (217)
Arai, Y. (217)
Arnaez, O. (217)
Artamonov, A. (217)
Asai, S. (217)
Asquith, L. (217)
Assamagan, K. (217)
Baak, M. A. (217)
Bachacou, H. (217)
Bachas, K. (217)
Backes, M. (217)
Bain, T. (217)
Baines, J. T. (217)
Baker, O. K. (217)
Banas, E. (217)
Barberio, E. L. (217)
Barbero, M. (217)
Barillari, T. (217)
Barisonzi, M. (217)
Barklow, T. (217)
Barlow, N. (217)
Barnett, B. M. (217)
Barnett, R. M. (217)
Bartoldus, R. (217)
Bates, R. L. (217)
Beau, T. (217)
Beck, H. P. (217)
Beckingham, M. (217)
Bell, W. H. (217)
Bella, G. (217)
Beltramello, O. (217)
Benary, O. (217)
Benekos, N. (217)
Benhammou, Y. (217)
Benjamin, D. P. (217)
visa färre...
Lärosäte
Stockholms universitet (217)
Lunds universitet (217)
Uppsala universitet (212)
Språk
Engelska (217)
Ämne (HSV)
Naturvetenskap (217)

År

 
pil uppåt Stäng

Kopiera och spara länken för att återkomma till aktuell vy