122772869
Quantum dynamical aspects of two-dimensional spaces of constant negative curvature
The authors study the quantum mechanics of two-dimensional spaces of constant negative curvature. The connection between different formulations is analysed. They derive the propagator and find that in the semiclassical approximation, the time evolution of observables exhibits similar features as in the classical case.
118355615
Hadronic top-quark pair production in association with two jets at Next-to-Leading Order QCD
We report on the calculation of the next-to-leading order QCD corrections to the production of t¯ pairs in association with two hard jets at the Fermilab TeVatron and CERN Large Hadron Collider. Results for the integrated and differential cross sections are given. The corrections with respect to leading order are negative and moderate. A study of the scale dependence of our NLO predictions indicates that the residual theoretical uncertainty, due to higher order corrections, is 21% for the TeVatron and 15% for the LHC. In case of the TeVatron, the forward-backward asymmetry of the top quark is calculated for the first time at next-to-leading order. With the inclusive selection of cuts, this asymmetry amounts to A t,LO = 10.3% at leading order and A t,NLO = 4.6% at next-to-leading order. All results presented in this paper have been obtained with the help of the Helac-Nlo package.
19377341
Intermittency in high-energy collisions and a phase transition in the Feynman-Wilson fluid.
We study the intermittency effect in multihadron production processes as a critical phenomenon reflecting a higher-order quark-hadron phase transition in the hadronization process. We show that the production of a critical Feynman-Wilson fluid, representing the hadronized system at the critical temperature, has a fractal structure in a wide range of scales in the rapidity space. The intermittency pattern is specified by the critical exponent alone and, for each factorial moment, a minimal scale in rapidity emerges below which the power-law behavior breaks down. The relevance of the model for quark-gluon-plasma physics in present and future experiments is also discussed.
40433366
Unusual phenomena in the rapidity distribution and the phase transition of the quark-gluon plasma.
Meson as well as baryon production as a phase transition of a quark-gluon plasma is discussed in the context of a two-dimensional (rapidity, proper time) model with Kadanoff scaling. Unusual features of the model, not met in perturbative QCD or in the dual parton model, are the possible appearance in the fragmentation region below an energy limit of events with exceptionally high-multiplicity, meson cluster production appearing as secondary maxima of the fixed-n central meson distribution, as well as sharp baryon spikes near the target and projectile-fragmentation regions.
17220343
Multiscalar production amplitudes beyond threshold
We present exact tree-order amplitudes for H ∗ ! n H, for final states containing one or two particles with non-zero three-momentum, for various interaction potentials. We show that there are potentials leading to tree amplitudes that satisfy unitarity, not only at threshold but also in the above kinematical configurations and probably beyond. As a by-product, we also calculate 2 ! n tree amplitudes at threshold and show that for the unbroken φ 4 theory they vanish for n > 4 , for the Standard Model Higgs they vanish for n � 3 and for a model potential, respecting tree-order unitarity, for n even and n > 4 . Finally, we calculate the imaginary part of the one-loop 1 ! n amplitude in both symmetric and spontaneously broken φ 4 theory.
40356704
Hadronic intermittency and chaotic motion in rapidity space.
We show that the Hamiltonian dynamics of the effective two-particle potential, describing an additional component of the hadronic S matrix and corresponding to the Feynman-Wilson fluid in one dimension, leads to trapped chaotic and/or diffusive intermittent motion. We argue that the strong density fluctuations in rapidity space, generated by this motion, are related to the intermittency of the multihadron distributions at high energies
2491688
Modeling skew quadruple effects on the UMER beam
This is a numerical and experimental study of the effects of skew quadrupoles on the beam used in University of Maryland Electron Ring (UMER). As this beam is space- charge dominated, we expect new phenomena to be present compared to the emittance-dominated case. In our studies we find that skew quadrupoles can severely affect the halo of the beam and cause emittance growth, even in the first turn of the beam. For our simulations we use the WARP particle-in-cell code and we compare the results with the experimental study of skew quadrupole effects.
117846326
The Zr-92(n,gamma) reaction and its implications for stellar nucleosynthesis
Because the relatively small neutron capture cross sections of the zirconium isotopes are difficult to measure, the results of previous measurements are often not adequate for a number of problems in astrophysics and nuclear technology. Therefore, the Zr-92(n,gamma) cross section has been remeasured at the CERN n_TOF facility, providing a set of improved parameters for 44 resonances in the neutron energy range up to 40 keV. With this information the cross-section uncertainties in the keV region could be reduced to 5% as required for s-process nucleosynthesis studies and technological applications.
121078454
Astrophysics at n_TOF Facility at CERN
The neutron time of flight (n_TOF) facility at CERN is a spallation neutron source with white neutron energy spectrum (from thermal to several GeV), covering the full energy range of interest for nuclear astrophysics, in particular for measurements of the neutron capture cross section required in s-process nucleosynthesis. This contribution presents an overview on the astrophysical program carried on at the n_TOF facility, the main results and their implications.
118856700
Numerical investigations of mismatch induced halos in intense charged particle beams
In this paper, we discuss the parametric resonance model of halo creation, and compare it with self consistent simulation results. In particular, we employ two different initial distribution functions, and we find agreement with the particle‐core model, within the limitations of the latter. Furthermore, using a simple particle tracking algorithm, we are able to follow the trajectories of the halo particles, noting that a large number of them go through the core and re‐emerge later.
54968955
Nuclear Physics for the Re/Os Clock
Dating the age of the universe by the β-decay of 187Re (t1/2 = 41.2 Gyr) 
requires the accurate assessment of the s-process reaction flow. The daughter 
nucleus 187Os as well as its immediate s-only neighbor 186Os are shielded from 
the r-process. Therefore, the radiogenic contribution to 187Os can be derived 
via the local approximation of the s-process, which is well justified in this 
mass region: ( σ Ns)187 = ( σ Ns)186. Accordingly, accurate Maxwellianaveraged 
(n, γ ) cross sections have to be known for 186Os and 187Os over the 
full range of s-process temperatures. Because 187Os has low-lying excited 
states, which are significantly populated during the s-process, neutron captures 
on these excited states have to be properly taken into account. The input 
for the corresponding Hauser–Feshbach calculations can be constrained by 
deriving the strength functions from a detailed resonance analysis of the 
measured (n, γ ) cross sections as well as by an additional measurement of 
the inelastic scattering cross section for the first exited level, which dominates 
the competition between the capture and scattering channels. This contribution 
reports on measurements of the neutron capture cross sections of 186Os, 187Os 
and 188Os from the eV region to 1MeV at the CERN/n TOF facility and of the 
inelastic scattering cross section of 187Os around 30 keV at the Karlsruhe 
3.7 MV Van de Graaff accelerator. Based on these results and on a 
detailed resonance analysis, improved Maxwellian-averaged cross sections 
were obtained for thermal energies between 5 keV and 100 keV. The 
implications of these results for the Re/Os clock are discussed.