29 research outputs found

    First measurement of coherent ρ0 photoproduction in ultra-peripheral Xe–Xe collisions at √sNN = 5.44 TeV

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    The first measurement of the coherent photoproduction of ρ0 vector mesons in ultra-peripheral Xe–Xe collisions at sNN=5.44 TeV is presented. This result, together with previous HERA γp data and γ–Pb measurements from ALICE, describes the atomic number (A) dependence of this process, which is particularly sensitive to nuclear shadowing effects and to the approach to the black-disc limit of QCD at a semi-hard scale. The cross section of the Xe+Xe→ρ0+Xe+Xe process, measured at midrapidity through the decay channel ρ0→π+π−, is found to be dσ/dy=131.5±5.6(stat.)−16.9+17.5(syst.) mb. The ratio of the continuum to resonant contributions for the production of pion pairs is also measured. In addition, the fraction of events accompanied by electromagnetic dissociation of either one or both colliding nuclei is reported. The dependence on A of cross section for the coherent ρ0 photoproduction at a centre-of-mass energy per nucleon of the γA system of WγA,n=65 GeV is found to be consistent with a power-law behaviour σ(γA→ρ0A)∝Aα with a slope α=0.96±0.02(syst.). This slope signals important shadowing effects, but it is still far from the behaviour expected in the black-disc limit.publishedVersio

    Genetic Diversity and Demographic History of Wild and Cultivated/Naturalised Plant Populations: Evidence from Dalmatian Sage (Salvia officinalis L., Lamiaceae)

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    Dalmatian sage (Salvia officinalis L., Lamiaceae) is a well-known aromatic and medicinal Mediterranean plant that is native in coastal regions of the western Balkan and southern Apennine Peninsulas and is commonly cultivated worldwide. It is widely used in the food, pharmaceutical and cosmetic industries. Knowledge of its genetic diversity and spatiotemporal patterns is important for plant breeding programmes and conservation. We used eight microsatellite markers to investigate evolutionary history of indigenous populations as well as genetic diversity and structure within and among indigenous and cultivated/naturalised populations distributed across the Balkan Peninsula. The results showed a clear separation between the indigenous and cultivated/naturalised groups, with the cultivated material originating from one restricted geographical area. Most of the genetic diversity in both groups was attributable to differences among individuals within populations, although spatial genetic analysis of indigenous populations indicated the existence of isolation by distance. Geographical structuring of indigenous populations was found using clustering analysis, with three sub-clusters of indigenous populations. The highest level of gene diversity and the greatest number of private alleles were found in the central part of the eastern Adriatic coast, while decreases in gene diversity and number of private alleles were evident towards the northwestern Adriatic coast and southern and eastern regions of the Balkan Peninsula. The results of Ecological Niche Modelling during Last Glacial Maximum and Approximate Bayesian Computation suggested two plausible evolutionary trajectories: 1) the species survived in the glacial refugium in southern Adriatic coastal region with subsequent colonization events towards northern, eastern and southern Balkan Peninsula; 2) species survived in several refugia exhibiting concurrent divergence into three genetic groups. The insight into genetic diversity and structure also provide the baseline data for conservation of S. officinalis genetic resources valuable for future breeding programmes

    Multiplicity dependence of charged-particle jet production in pp collisions at root s=13 TeV

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    Measurements of mixed harmonic cumulants in Pb-Pb collisions at root s(NN)=5.02 TeV

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    Correlations between moments of different flow coefficients are measured in Pb-Pb collisions at root s(NN) = 5.02 TeV recorded with the ALICE detector. These new measurements are based on multiparticle mixed harmonic cumulants calculated using charged particles in the pseudorapidity region vertical bar eta vertical bar < 0.8 with the transverse momentum range 0.2 < p(T) < 5.0 GeV/c. The centrality dependence of correlations between two flow coefficients as well as the correlations between three flow coefficients, both in terms of their second moments, are shown. In addition, a collection of mixed harmonic cumulants involving higher moments of v(2) and v(3) is measured for the first time, where the characteristic signature of negative, positive and negative signs of four-, six- and eight-particle cumulants are observed, respectively. The measurements are compared to the hydrodynamic calculations using iEBE-VISHNU with AMPT and TRENTo initial conditions. It is shown that the measurements carried out using the LHC Run 2 data in 2015 have the precision to explore the details of initial-state fluctuations and probe the nonlinear hydrodynamic response of v(2) and v(3) to their corresponding initial anisotropy coefficients epsilon(2) and epsilon(3). These new studies on correlations between three flow coefficients as well as correlations between higher moments of two different flow coefficients will pave the way to tighten constraints on initial-state models and help to extract precise information on the dynamic evolution of the hot and dense matter created in heavy-ion collisions at the LHC. (C) 2021 The Author. Published by Elsevier B.V
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