Azimuthal anisotropy of charged jet production in root s(NN)=2.76 TeV Pb-Pb collisions

We present measurements of the azimuthal dependence of charged jet production in central and semi-central root s(NN) = 2.76 TeV Pb-Pb collisions with respect to the second harmonic event plane, quantified as nu(ch)(2) (jet). Jet finding is performed employing the anti-k(T) algorithm with a resolution parameter R = 0.2 using charged tracks from the ALICE tracking system. The contribution of the azimuthal anisotropy of the underlying event is taken into account event-by-event. The remaining (statistical) region-to-region fluctuations are removed on an ensemble basis by unfolding the jet spectra for different event plane orientations independently. Significant non-zero nu(ch)(2) (jet) is observed in semi-central collisions (30-50% centrality) for 20 <p(T)(ch) (jet) <90 GeV/c. The azimuthal dependence of the charged jet production is similar to the dependence observed for jets comprising both charged and neutral fragments, and compatible with measurements of the nu(2) of single charged particles at high p(T). Good agreement between the data and predictions from JEWEL, an event generator simulating parton shower evolution in the presence of a dense QCD medium, is found in semi-central collisions. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).Peer reviewe

Pseudorapidity and transverse-momentum distributions of charged particles in proton-proton collisions at root s=13 TeV

The pseudorapidity (eta) and transverse-momentum (p(T)) distributions of charged particles produced in proton-proton collisions are measured at the centre-of-mass energy root s = 13 TeV. The pseudorapidity distribution in vertical bar eta vertical bar <1.8 is reported for inelastic events and for events with at least one charged particle in vertical bar eta vertical bar <1. The pseudorapidity density of charged particles produced in the pseudorapidity region vertical bar eta vertical bar <0.5 is 5.31 +/- 0.18 and 6.46 +/- 0.19 for the two event classes, respectively. The transverse-momentum distribution of charged particles is measured in the range 0.15 <p(T) <20 GeV/c and vertical bar eta vertical bar <0.8 for events with at least one charged particle in vertical bar eta vertical bar <1. The evolution of the transverse momentum spectra of charged particles is also investigated as a function of event multiplicity. The results are compared with calculations from PYTHIA and EPOS Monte Carlo generators. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).Peer reviewe

Interaction between redox-based resistive switching mechanisms

Memory concepts based on resistive switching (RRAM) make use of simple metal-isolatormetal (MIM) structures despite the steady progress in thin film preparation and patterning. Recently, this approach has attracted considerable interest due to the prospect of nonvolatile data storage combining low power consumption with fast write and read operation. The integration of resistive switching memory elements in crossbar arrays is a favorable approach because in this configuration the data can be stored within the minimum area of 4 F$^{2}$. Promising materials include a wide range of binary and ternary oxides. However, the underlying mechanisms are still under discussion. Among the binary transition metal oxides TiO$_{2}$ has turned out to be a very attractive CMOS compatible material. Bipolar resistive switching in this material is based on a modulation of a Schottky-like interface formed at the metal-TiO$_{2}$ interface. This modulation is due to the drift of oxygen vacancies under an applied electric field and subsequent redox processes at the electrode. These processes create conducting channels that either short-circuit or recover the barrier during the resistive switching. Memory concepts relying on these processes are called valence change mechanism (VCM) memory. In practice these processes are steered to one specific interface of the layer stack by incorporation an asymmetric device structure. In this thesis mainly TiO$_{2}$ based memory elements were investigated in two different device structures for the possible use in future RRAM based memory technologies, or even logic applications. The initial electroforming step was subject of detailed study by in-situ SEM and cross-sectional SEM and TEM on the formed devices. Electroforming results in considerable electric and mechanical stress that lead to partly recrystallization and other changes of the film morphology. Locally very high temperatures due to Joule heating is expected to be the reason. The insight gained from the stress investigations was considered to identify and overcome the need of this electroforming step. To achieve this goal Interface engineering is proposed. The high workfunction material Pt was replaced by the low workfunction metal W. With the release of a Schottky interface the need of the electrical and mechanical stressing electroforming step could be avoided. Beside the structural stress induced by electroforming a further challenge for ultimately scalable passive Nano-Crossbar architectures are the sneak paths limiting the maximum array size. Here a wide range of voltage pulse signals were used to test the feasibility of voltage write/read schemes. These voltage schemes with a special biasing of the memory elements will be used to properly address resistive memories in a crossbar array. An ultra non-linear switching kinetic is needed for these biasing data operation schemes. To test these kinetics an RF measurement setup with the ability of transient current mapping during fast pulse data operation was designed and constructed. The measurement results in combination with electrothermal simulations confirm the thermally activated fast oxygen vacancy movement needed for the ultra-fast switching process. In contrast to next generation reconfigurable logic applications high speed memories will use select devices. Memory devices with a select transistor were fabricated and electrically characterized in respect of fast pulse driven electroforming and resistive switching. The select transistor was able to decrease the transient current during ultra-fast resistive switching by the factor of 10 to a range below 10 μA. This result in combination with the fast switching is a very promising step towards a low power RRAM technology

Analysis of transient currents during ultrafast switching of TiO2 nanocrossbar devices

In this letter, bipolar fast-pulse switching in TiO2-based nanocrossbar devices was investigated. A dedicated measurement setup was used to measure the transient currents during 5-ns resistive switching. Transient peak currents for the SET and RESET processes were as high as 200 and 230 mu A, respectively. The currents observed during fast-pulse switching are explained and simulated by Joule heating, which is needed for fast oxygen-vacancy movement. The measured transient currents enable a further optimization of resistive switches based on TiO

Where Brain, Body and World Collide

The production cross section of electrons from semileptonic decays of beauty hadrons was measured at mid-rapidity (|y| &lt; 0.8) in the transverse momentum range 1 &lt; pt &lt; 8 Gev/c with the ALICE experiment at the CERN LHC in pp collisions at a center of mass energy sqrt{s} = 7 TeV using an integrated luminosity of 2.2 nb^{-1}. Electrons from beauty hadron decays were selected based on the displacement of the decay vertex from the collision vertex. A perturbative QCD calculation agrees with the measurement within uncertainties. The data were extrapolated to the full phase space to determine the total cross section for the production of beauty quark-antiquark pairs

生産增加と貨幣需要

We report on two-particle charge-dependent cor- relations in pp, p\u2013Pb, and Pb\u2013Pb collisions as a function of the pseudorapidity and azimuthal angle difference, \u3b7 and \u3c6 respectively. These correlations are studied using the balance function that probes the charge creation time and the develop- ment of collectivity in the produced system. The dependence of the balance function on the event multiplicity as well as on the trigger and associated particle transverse momentum ( pT ) in pp, p\u2013Pb, and Pb\u2013Pb collisions at 1asNN = 7, 5.02, and 2.76 TeV, respectively, are presented. In the low transverse momentum region, for 0.2 < pT < 2.0 GeV/c, the balance function becomes narrower in both \u3b7 and \u3c6 directions in all three systems for events with higher multiplicity. The experimental findings favor models that either incorporate some collective behavior (e.g. AMPT) or different mecha- nisms that lead to effects that resemble collective behavior (e.g. PYTHIA8 with color reconnection). For higher values of transverse momenta the balance function becomes even narrower but exhibits no multiplicity dependence, indicating that the observed narrowing with increasing multiplicity at low pT is a feature of bulk particle production