1,488 research outputs found
Relativistic Expansion of Electron-Positron-Photon Plasma Droplets and Photon Emission
The expansion dynamics of hot electron-positron-photon plasma droplets is
dealt with within relativistic hydrodynamics. Such droplets, envisaged to be
created in future experiments by irradiating thin foils with
counter-propagating ultra-intense laser beams, are sources of flashes of gamma
radiation. Warm electron-positron plasma droplets may be identified and
characterized by a broadened 511 keV line
Classification of four-qubit entangled states via Machine Learning
We apply the support vector machine (SVM) algorithm to derive a set of
entanglement witnesses (EW) to identify entanglement patterns in families of
four-qubit states. The effectiveness of SVM for practical EW implementations
stems from the coarse-grained description of families of equivalent entangled
quantum states. The equivalence criteria in our work is based on the stochastic
local operations and classical communication (SLOCC) classification and the
description of the four-qubit entangled Werner states. We numerically verify
that the SVM approach provides an effective tool to address the entanglement
witness problem when the coarse-grained description of a given family state is
available. We also discuss and demonstrate the efficiency of nonlinear kernel
SVM methods as applied to four-qubit entangled state classification.Comment: 10 pages, 8 figure
Multiparticle angular correlations: a probe for the sQGP at RHIC
A novel decomposition technique is used to extract the centrality dependence
of di-jet properties and yields from azimuthal correlation functions obtained
in Au+Au collisions at =200 GeV. The width of the
near-side jet shows very little dependence on centrality. In contrast, the
away-side jet indicates substantial broadening as well as hints for for a local
minimum at for central and mid-central events. The yield of
jet-pairs (per trigger particle) slowly increases with centrality for both the
near- and away-side jets. These observed features are compatible with several
recent theoretical predictions of possible modifications of di-jet
fragmentation by a strongly interacting medium. Several new experimental
approaches, including the study of flavor permutation and higher order
multi-particle correlations, that might help to distinguish between different
theoretical scenarios are discussed.Comment: Proceedings of the MIT workshop on correlations and fluctation
Femtosecond photodissociation dynamics of 1,4-diiodobenzene by gas-phase X-ray scattering and photoelectron spectroscopy
We present a multifaceted investigation into the initial photodissociation dynamics of 1,4-diiodobenzene (DIB) following absorption of 267 nm radiation. We combine ultrafast time-resolved photoelectron spectroscopy and X-ray scattering experiments performed at the Linac Coherent Light Source (LCLS) to study the initial electronic excitation and subsequent rotational alignment, and interpret the experiments in light of Complete Active Space Self-Consistent Field (CASSCF) calculations of the excited electronic landscape. The initially excited state is found to be a bound 1B1 surface, which undergoes ultrafast population transfer to a nearby state in 35 ± 10 fs. The internal conversion most likely leads to one or more singlet repulsive surfaces that initiate the dissociation. This initial study is an essential and prerequisite component of a comprehensive study of the complete photodissociation pathway(s) of DIB at 267 nm. Assignment of the initially excited electronic state as a bound state identifies the mechanism as predissociative, and measurement of its lifetime establishes the time between excitation and initiation of dissociation, which is crucial for direct comparison of photoelectron and scattering experiments.</p
Parton energy loss limits and shadowing in Drell-Yan dimuon production
A precise measurement of the ratios of the Drell-Yan cross section per
nucleon for an 800 GeV/c proton beam incident on Be, Fe and W targets is
reported. The behavior of the Drell-Yan ratios at small target parton momentum
fraction is well described by an existing fit to the shadowing observed in
deep-inelastic scattering. The cross section ratios as a function of the
incident parton momentum fraction set tight limits on the energy loss of quarks
passing through a cold nucleus
Measurement of Angular Distributions of Drell-Yan Dimuons in Interactions at 800 GeV/c
We report a measurement of the angular distributions of Drell-Yan dimuons
produced using an 800 GeV/c proton beam on a hydrogen target. The polar and
azimuthal angular distribution parameters have been extracted over the
kinematic range GeV/c (excluding the
resonance region), GeV/c, and . The angular
distributions are similar to those of , and both data sets are compared
with models which attribute the distribution either to the
presence of the transverse-momentum-dependent Boer-Mulders structure function
or to QCD effects. The data indicate the presence of both
mechanisms. The validity of the Lam-Tung relation in Drell-Yan is also
tested.Comment: 4 pages, 3 figure
- …