Ref HAL: hal-01104084_v1
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Résumé:

New 1D hybrid nano-systems are elaborated with photo-active -conjugated molecules (PAM) either encapsulated into the hollow core of single-wall carbon nanotubes or non-covalently functionalized at their outer surface. The physical properties can be tuned by modifying the structural properties, providing practical routes to fit different requirements for potential applications. In this study, we report results obtained by functionalizing single wall carbon nanotubes with quathertiophene (4T) and phathlocyanine (MPc) molecules. The structural properties are investigated mainly by x-ray diffraction and/or Transmission Electron Microscopy and Raman spectroscopy. We evidence that the supramolecular organizations of confined oligothiophenes (from 1 to 3 chains into a nanotube section) depend on the nanocontainer size whereas phthalocyanine encapsulation leads the formation of a 1D-phase for which the angle between the molecule ring and the nanotubes axis is close to 32°. Confined MPc molecules display Raman spectra hardly altered with respect to the bulk phase, suggesting a rather weak interaction with the tubes. In contrast, the vibrational properties of the molecules functionalized at the outer surface of tubes display important modifications. We assume a significant curvature of the phthalocyanine induced by the interaction with the tube walls and a change of the central atom position within the molecular ring, in good agreement with our DFT calculations.

PMID 24655244
Ref Arxiv: 1311.2006
DOI: 10.1103/PhysRevLett.112.091804
WoS: 000332687600001
Ref. & Cit.: NASA ADS
27 Citations
Résumé:

This Letter presents a search for quantum black-hole production using 20.3 inverse fb of data collected with the ATLAS detector in pp collisions at the LHC at sqrt(s) = 8 TeV. The quantum black holes are assumed to decay into a lepton (electron or muon) and a jet. In either channel, no event with a lepton-jet invariant mass of 3.5 TeV or more is observed, consistent with the expected background. Limits are set on the product of cross sections and branching fractions for the lepton+jet final states of quantum black holes produced in a search region for invariant masses above 1 TeV. The combined 95% confidence level upper limit on this product for quantum black holes with threshold mass above 3.5 TeV is 0.18 fb. This limit constrains the threshold quantum black-hole mass to be above 5.3 TeV in the model considered.

Commentaires: See paper for full list of authors - 6 pages plus author list (20 pages total), 2 figures, 2 tables, submitted to Physical Review Letters, All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/EXOT-2013-03/

Ref Arxiv: 1310.6527
DOI: 10.1016/j.physletb.2013.12.010
WoS: 000330556000059
Ref. & Cit.: NASA ADS
11 Citations
Résumé:

A measurement of the mass difference between top and anti-top quarks is presented. In a 4.7 fb-1 data sample of proton--proton collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector at the LHC, events consistent with ttbar production and decay into a single charged lepton final state are reconstructed. For each event, the mass difference between the top and anti-top quark candidate is calculated. A two b-tag requirement is used in order to reduce the background contribution. A maximum likelihood fit to these per-event mass differences yields mt-mtbar = 0.67 +/- 0.61 (stat) +/- 0.41 (syst) GeV, consistent with CPT invariance.

Commentaires: See paper for full list of authors - 6 pages plus author list (22 pages total), 3 figures, 2 tables, submitted to Physics Letter B, All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/TOPQ-2012-06/

Ref Arxiv: 1409.5500
DOI: 10.1007/JHEP11(2014)104
WoS: 000345620200001
Ref. & Cit.: NASA ADS
83 Citations
Résumé:

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 ($T$), the decay targeted is $T \rightarrow Zt$, while the decay targeted for a new charge -1/3 quark ($B$) is $B \rightarrow Zb$. The search is performed with a dataset corresponding to 20.3 fb$^{-1}$ of $pp$ collisions at $\sqrt{s}=8$ 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 (electrons or muons), 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.

Commentaires: See paper for full list of authors - 36 pages plus author list + cover pages (59 pages total), 15 figures, 8 tables, submitted to JHEP. All figures, including auxiliary figures, are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/EXOT-2013-17/

PMID 25814875
Ref Arxiv: 1407.3935
DOI: 10.1140/epjc/s10052-014-3130-x
WoS: 000347171000001
Ref. & Cit.: NASA ADS
190 Citations
Résumé:

This paper presents the performance of the ATLAS muon reconstruction during the LHC run with $pp$ collisions at $\sqrt{s}=7-8$ TeV in 2011-2012, focusing mainly on data collected in 2012. Measurements of the reconstruction efficiency and of the momentum scale and resolution, based on large reference samples of $J/\psi\to \mu\mu$, $Z\to \mu\mu$ and $\Upsilon\to\mu\mu$ decays, are presented and compared to Monte Carlo simulations. Corrections to the simulation, to be used in physics analysis, are provided. Over most of the covered phase space (muon $|\eta|<2.7$ and $5 \lesssim p_{\mathrm{T}} \lesssim 100$ GeV) the efficiency is above $99\%$ and is measured with per-mille precision. The momentum resolution ranges from $1.7\%$ at central rapidity and for transverse momentum $p_{\mathrm{T}} \simeq 10$ GeV, to $4\%$ at large rapidity and $p_{\mathrm{T}} \simeq 100$ GeV. The momentum scale is known with an uncertainty of $0.05\%$ to $0.2\%$ depending on rapidity. A method for the recovery of final state radiation from the muons is also presented.

Commentaires: See paper for full list of authors - 21 pages plus author list + cover pages (34 pages total), 21 figures, 2 tables, submitted to EPJC, All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/PERF-2014-05/

Ref Arxiv: 1405.4123
DOI: 10.1103/PhysRevD.90.052005
WoS: 000342142500001
Ref. & Cit.: NASA ADS
263 Citations
Résumé:

The ATLAS detector at the Large Hadron Collider is used to search for high-mass resonances decaying to dielectron or dimuon final states. Results are presented from an analysis of proton-proton (pp) collisions at a center-of-mass energy of 8 TeV corresponding to an integrated luminosity of 20.3 fb-1 in the dielectron channel and 20.5 fb-1 in the dimuon channel. A narrow resonance with Standard Model Z couplings to fermions is excluded at 95% confidence level for masses less than 2.79 TeV in the dielectron channel, 2.53 TeV in the dimuon channel, and 2.90 TeV in the two channels combined. Limits on other model interpretations are also presented, including a grand-unification model based on the E6 gauge group, Z* bosons, Minimal Z' Models, a spin-2 graviton excitation from Randall-Sundrum models, quantum black holes and a Minimal Walking Technicolor model with a composite Higgs boson.

Commentaires: See paper for full list of authors -18 pages plus author list (31 pages total), 10 figures, 9 tables, submitted to Phys. Rev. D, All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/EXOT-2012-23/

Ref Arxiv: 1404.7035
DOI: 10.1007/JHEP07(2014)154
WoS: 000340391300001
Ref. & Cit.: NASA ADS
27 Citations
Résumé:

The prompt and non-prompt production cross-sections for the chi_c1 and chi_c2 charmonium states are measured in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector at the LHC using 4.5 fb^-1 of integrated luminosity. The chi_c states are reconstructed through the radiative decay chi_c -> J/psi gamma (with J/psi -> mu+mu-) where photons are reconstructed from gamma -> e+e- conversions. The production rate of the chi_c2 state relative to the chi_c1 state is measured for prompt and non-prompt chi_c as a function of J/psi transverse momentum. The prompt chi_c cross-sections are combined with existing measurements of prompt J/psi production to derive the fraction of prompt J/psi produced in feed-down from chi_c decays. The fractions of chi_c1 and chi_c2 produced in b-hadron decays are also measured. In addition to measurements of inclusive chi_c production, the branching fraction B(B+ -> chi_c1 K+) = (4.9 +/- 0.9 stat. +/- 0.6 syst.) * 10^-4 is measured with the same dataset and chi_c event selection.

Commentaires: See paper for full list of authors - 38 pages plus author list (62 pages total), 10 figures, 13 tables, submitted to JHEP, All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/BPHY-2013-05/