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At least 235 records · Page 13

Light and Strange Vector Resonances from Lattice QCD at Physical Quark Masses

We present the first ab initio calculation at physical quark masses of scattering amplitudes describing the lightest pseudoscalar mesons interacting via the strong force in the vector channel. Using lattice quantum chromodynamics, we postdict the defining parameters for two short-lived resonances, the ρ(770) and K*(892) which manifest as complex energy poles in ππ and Kπ scattering amplitudes, respectively. The calculation proceeds by first computing the finite-volume energy spectrum of the two-hadron systems and then determining the amplitudes from the energies using the Lüscher formalism. The error budget includes a data-driven systematic error, obtained by scanning possible fit ranges and fit models to extract the spectrum from Euclidean correlators, as well as the scattering amplitudes from the latter. The final results, obtained by analytically continuing multiple parametrizations into the complex energy plane, are M ρ = 796(5)(50)MeV, Γ ρ = 192(10)(31) MeV, M K* = 893(2)(54) MeV, and Γ K = 51(2)(11) MeV, where the subscript indicates the resonance and M and Γ stand for the mass and width, respectively, and where the first bracket indicates the statistical and the second bracket the systematic uncertainty.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Mott-Anderson freeze-out and the strange matter “horn”

We discuss the √s-dependence of the K {sup +}/π{sup +} ratio in heavy-ion collisions (the “horn” effect) within a Mott-Anderson localization model for chemical freeze-out. The different response of pion and kaon radii to the hot and dense hadronic medium results in different freeze-out conditions. We demonstrate within a simple model that this circumstance enhances the “horn” effect relative to statistical models with universal chemical freeze-out.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

Phloem Loading and Unloading of Sucrose: What a Long, Strange Trip from Source to Sink

Sucrose is transported from sources (mature leaves) to sinks (importing tissues such as roots, stems, fruits, and seeds) through the phloem tissues in veins. In many herbaceous crop species, sucrose must first be effluxed to the cell wall by a sugar transporter of the SWEET family prior to being taken up into phloem companion cells or sieve elements by a different sugar transporter, called SUT or SUC. The import of sucrose into these cells is termed apoplasmic phloem loading. In sinks, sucrose can similarly exit the phloem apoplasmically or, alternatively, symplasmically through plasmodesmata into connecting parenchyma storage cells. Recent advances describing the regulation and manipulation of sugar transporter expression and activities provide stimulating new insights into sucrose phloem loading in sources and unloading processes in sink tissues. Additionally, new breakthroughs have revealed distinct subpopulations of cells in leaves with different functions pertaining to phloem loading. These and other discoveries in sucrose transport are discussed.

Plant Sciences↗

Strangeness Production in Jets with ALICE at the LHC

At this laboratory Physicists and Engineers study fundamental particles using the world’s largest and most complex instruments. Here particles are made to collide at close to the speed of light to see how they interact and help to discover the basic laws of nature. One type of instrument used at CERN is a particle accelerator that boosts beams of particles to high energies and make them collide with either stationary particles or each other. Other types of instruments are the detectors which observe and record the collisions. CERN was founded in 1954 and sits by the France-Swiss border near Geneva. It was one of Europe’s first joint ventures and now has 20 member states. The name CERN is an acronym for the French "Conseil Européen pour la Recherche Nucléaire", or European Council for Nuclear Research, a provisional body founded in 1952 with the mandate of establishing a world-class fundamental physics research organization in Europe. At that time, pure physics research concentrated on understanding the inside of the atom. CERN's main area of research is particle physics the study of the fundamental constituents of matter and the forces acting between them. The laboratory operated by CERN is often referred to as the European Laboratory for Particle Physics.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗