15020766
Report of the working group on the measurement of triple gauge boson couplings
The working group discussed several aspects of triple gauge coupling analysis viewed in the light of experiences with the first high-energy data recorded at energies above the W pair threshold. Some analysis methods were reviewed briefly, and consideration given to better ways of characterizing the data. The measurement of CP-violating parameters was discussed. Results were prepared to further quantify the precision attainable on anomalous couplings in the four-quark channel using jet-charge methods, and finally the trade-off between maximum LEP energy versus luminosity was quantified.
120586857
The Gross-Neveu model near the critical temperature. A mechanism for quark-hadron phase transition in relativistic ion collisions
Abstract It is argued that the longitudinal, critical evolution of the quark-gluon system, formed in relativistic ion collisions, can be reliably studied within the framework of the Gross-Neveu two-dimensional field theory at finite temperature. In particular, the Ginzburg-Landau approximation, near the critical temperature reveals some remarkable and measurable inhomogeneities in the rapidity density of the hadronic phase, when appropriate boundary conditions, dictated by space-time causality, are imposed on the classical solutions of the model. The relevance of the results for the experiments with relativistic ions is briefly discussed.
5166537
NLO QCD corrections to tri-boson production
We present a calculation of the NLO QCD corrections for the production of three vector bosons at the LHC, namely ZZZ, W+W−Z, W+ZZ, and W+W−W+ production. The virtual corrections are computed using the recently proposed method of reduction at the integrand level (OPP reduction). Concerning the contributions coming from real emission we used the dipole subtraction to treat the soft and collinear divergences. We find that the QCD corrections for these electroweak processes are in the range between 70 and 100 percent. As such they have to be considered in experimental studies of triple vector boson production at the LHC.
16415075
Studying trilinear gauge couplings at LEP2 using optimal observables
Abstract We study the sensitivity of the processes e + e − → l ν l q q ′ at LEP2 energies on the non-standard trilinear gauge couplings (TGC), using the optimal observables method. All relevant leading logarithmic corrections to the three-order cross section, as well as experimental resolution effects have been studied. Taking into account correlations among the different TGC parameters we show that the limits on the TGC can reach the level of 0.15 (ld) at 161 GeV with 100 pb −1 , a challenge for the first LEP2 phase. At higher energies this can be improved drastically, reaching for the level of 0.02 (1 sd).
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.
14317912
Polarizing the dipoles
We extend the massless dipole formalism of Catani and Seymour, as well as its massive version as developed by Catani, Dittmaier, Seymour and Trocsanyi, to arbitrary helicity eigenstates of the external partons. We modify the real radiation subtraction terms only, the primary aim being an improved efficiency of the numerical Monte Carlo integration of this contribution as part of a complete next-to-leading order calculation. In consequence, our extension is only applicable to unpolarized scattering. Upon summation over the helicities of the emitter pairs, our formulae trivially reduce to their original form. We implement our extension within the framework of \textsc{Helac-Phegas}, and give some examples of results pertinent to recent studies of backgrounds for the LHC. The code is publicly available. Since the integrated dipole contributions do not require any modifications, we do not discuss them, but they are implemented in the software.
98058986
Measurement of the neutron induced fission cross section on transuranic (TRU) elements at the n_TOF facility at CERN
During the 2004 campaign, the n_TOF collaboration measured neutron fission cross sections for ^{233}U, ^{241,243}Am, ^{245}Cm, as well as the fission standards ^{235,238}U, using a sealed Fission Ionization Chamber (FIC). The setup included a total of 16 targets and 18 electrodes mounted together in a 50-cm length chamber, allowing the measurements of all isotopes at the same time, thus in the same experimental conditions. A brief description of the facility and of the detector setup will be presented followed by the preliminary results of the analysis of ^{235}U, ^{233}U, and ^{245}Cm from thermal energies up to some tenths of MeV.
109430895
Rotational Mismatches and Emittance Growth for the UMER Beam
This is a numerical study of the effects of a rotational mismatch of a beam at injection. A closely related type of mismatch is the presence of a skew quadrupole at some place in the transporting channel. In both cases, the initial mismatch implies that the emittance of the beam will increase as the beam is transported through an alternating focusing channel. In our simulations, we used the WARP computer code to simulate the University of Maryland Electron Ring (UMER) beam and we have indeed seen a substantial emittance growth (by a factor of 2–3) for mismatches of 10 degrees.
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.
23902126
The University of Maryland Electron Ring (UMER) enters a new regime of high-tune-shift rings
Beams with a high phase space density are useful for many modern applications such as free electron lasers, pulsed neutron sources, high-energy-density physics, and high-luminosity colliders. Production of such beams requires understanding the complex space charge dynamics at the low-energy end of the accelerator. The University of Maryland Electron Ring (UMER) has been designed and built with the purpose of investigating space charge effects using scaled low-energy electron experiments. We have recently circulated the highest- space-charge beam in a ring to date, achieving a breakthrough both in the number of turns and in the amount of current propagated. We have propagated a beam with an integer tune shift for over 100 turns, and other, even higher-current beams, for 5-50 turns albeit with some beam loss. One beam had a tune shift at injection of 5.0, which is several factors higher than anything propagated in the past. We report here as well on other interesting aspects of the UMER work.
123786004
Neutron physics of the Re/Os clock. III : Resonance analyses and stellar (n, gamma) cross sections of Os-186,Os-187,Os-188
Neutron resonance analyses have been performed for the capture cross sections of Os-186, Os-187, and Os-188 measured at the n_TOF facility at CERN. Resonance parameters have been extracted up to 5, 3, and 8 keV, respectively, using the SAMMY code for a full R-matrix fit of the capture yields. From these results average resonance parameters were derived by a statistical analysis to provide a comprehensive experimental basis for modeling of the stellar neutron capture rates of these isotopes in terms of the Hauser-Feshbach statistical model. Consistent calculations for the capture and inelastic reaction channels are crucial for the evaluation of stellar enhancement factors to correct the Maxwellian averaged cross sections obtained from experimental data for the effect of thermally populated excited states. These factors have been calculated for the full temperature range of current scenarios of s-process nucleosynthesis using the combined information of the experimental data in the region of resolved resonances and in the continuum. The consequences of this analysis for the s-process component of the Os-187 abundance and the related impact on the evaluation of the time duration of galactic nucleosynthesis via the Re/Os cosmochronometer are discussed.