√s NN = 5.02 TeV using the ALICE detector at the LHC. The measurement covers the p T interval 0.5 < p T < 12 GeV/c and the rapidity range −1.065 < y cms < 0.135 in the centre-of-mass reference frame. The contribution of electrons from background sources was subtracted using an invariant mass approach. The nuclear modification factor R pPb was calculated by comparing the p T -differential invariant cross section in p-Pb collisions to a pp reference at the same centre-of-mass energy, which was obtained by interpolating measurements at √ s = 2.76 TeV and √ s = 7 TeV. The R pPb is consistent with unity within uncertainties of about 25%, which become larger for p T below 1 GeV/c. The measurement shows that heavy-flavour production is consistent with binary scaling, so that a suppression in the high-p T yield in Pb-Pb collisions has to be attributed to effects induced by the hot medium produced in the final state. The data in p-Pb collisions are described by recent model calculations that include cold nuclear matter effects. IntroductionThe Quark-Gluon Plasma (QGP) [1,2], a colour-deconfined state of strongly-interacting matter, is predicted to exist at high temperature according to lattice Quantum Chromodynamics (QCD) calculations [3]. These conditions can be reached in ultra-relativistic heavy-ion collisions [4][5][6][7][8][9][10]. Charm and beauty (heavy-flavour) quarks are mostly produced in initial hard scattering processes on a very short time scale, shorter than the formation time of the QGP medium [11], and thus experience the full temporal and spatial evolution of the collision. While interacting with the QGP medium, heavy quarks lose energy via elastic and radiative processes [12][13][14]. Heavy-flavour hadrons are therefore well-suited probes to study the properties of the QGP. The effect of energy loss on heavy-flavour production can be characterised via the nuclear modification factor (R AA ) of heavy-flavour hadrons. The R AA is defined as the ratio of the heavy-flavour hadron yield in nucleusnucleus (A-A) collisions to that in proton-proton (pp) collisions scaled by the average number of binary nucleon-nucleon collisions. The R AA is studied differentially as a function of transverse momentum (p T ), rapidity ( y) and collision centrality. It was measured at the Relativistic Heavy Ion Collider (RHIC) [15][16][17][18] and at the Large Hadron Collider (LHC) [19][20][21][22]. At RHIC, in central The interpretation of the measurements in A-A collisions requires the study of heavy-flavour production in p-A collisions, which provides access to cold nuclear matter (CNM) effects. These effects are not related to the formation of a colour-deconfined medium, but are present in case of colliding nuclei (or protonnucleus). An important CNM effect in the initial state is partondensity shadowing or saturation, which can be described using modified parton distribution functions (PDF) in the nucleus [23] or using the Color Glass Condensate (CGC) effective theory [24]. Further CNM effects include energy loss [25] in...
We investigate the thermodynamic properties and the lattice stability of two-dimensional crystalline membranes, such as graphene and related compounds, in the low temperature quantum regime T → 0. A key role is played by the anharmonic coupling between in-plane and out-of-plane lattice modes that, in the quantum limit, has very different consequences from those in the classical regime. The role of retardation, namely of the frequency dependence, in the effective anharmonic interactions turns out to be crucial in the quantum regime. We identify a crossover temperature, T * , between classical and quantum regimes, which is ∼ 70 − 90 K for graphene. Below T * , the heat capacity and thermal expansion coefficient decrease as power laws with decreasing temperature, tending to zero for T → 0 as required by the third law of thermodynamics.
Sub-laser cycle time scale of electronic response to strong laser fields enables attosecond dynamical imaging in atoms, molecules and solids 1-4 . Optical tunneling and high harmonic generation 2, 5-7 are the hallmarks of attosecond imaging in optical domain, including imaging of phase transitions in solids 8, 9 . Topological phase transition yields a state of matter intimately linked with electron dynamics, as manifested via the chiral edge currents in topological insulators 10 . Does topological state of matter leave its mark on optical tunnelling 1 arXiv:1806.11232v2 [physics.optics]
Out of plane vibrations are suppressed in graphene layers placed on a substrate. These vibrations, in suspended samples, are relevant for the understanding of properties such as the electrical resistivity, the thermal expansion coefficient, and others. We use a general framework to study the properties of the out of plane mode in graphene on different substrates, taking into account the dynamics of the substrate. We discuss broadening of this mode and how it hybridizes with the substrate Rayleigh mode, comparing our model with experimental observations. We use the model to estimate the substrate induced changes in the thermal expansion coefficient and in the temperature dependence of the electrical resistivity.
We theoretically and experimentally investigated wasp-waisted magnetic hysteresis curves at a low temperature for CoFe2O4 nanopowders.
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