6,202 research outputs found
Quasi-particle functional Renormalisation Group calculations in the two-dimensional half-filled Hubbard model at finite temperatures
We present a highly parallelisable scheme for treating functional
Renormalisation Group equations which incorporates a quasi-particle-based
feedback on the flow and provides direct access to real-frequency self-energy
data. This allows to map out the boundaries of Fermi-liquid regimes and to
study the effect of quasi-particle degradation near Fermi liquid instabilities.
As a first application, selected results for the two-dimensional half-filled
perfectly nested Hubbard model are shown
Spectral function at high missing energies and momenta
The nuclear spectral function at high missing energies and momenta has been
determined from a self-consistent calculation of the Green's function in
nuclear matter using realistic nucleon-nucleon interactions. The results are
compared with recent experimental data derived from () reactions on
. A rather good agreement is obtained if the Green's functions are
calculated in a non-perturbative way.Comment: 10 pages, 3 figure
Fluence Dependence of Charge Collection of irradiated Pixel Sensors
The barrel region of the CMS pixel detector will be equipped with ``n-in-n''
type silicon sensors. They are processed on DOFZ material, use the moderated
p-spray technique and feature a bias grid. The latter leads to a small fraction
of the pixel area to be less sensitive to particles. In order to quantify this
inefficiency prototype pixel sensors irradiated to particle fluences between
and 2.6\times 10^{15} \Neq have been bump bonded to
un-irradiated readout chips and tested using high energy pions at the H2 beam
line of the CERN SPS. The readout chip allows a non zero suppressed analogue
readout and is therefore well suited to measure the charge collection
properties of the sensors.
In this paper we discuss the fluence dependence of the collected signal and
the particle detection efficiency. Further the position dependence of the
efficiency is investigated.Comment: 11 Pages, Presented at the 5th Int. Conf. on Radiation Effects on
Semiconductor Materials Detectors and Devices, October 10-13, 2004 in
Florence, Italy, v3: more typos corrected, minor changes required by the
refere
Test Beam Results of Geometry Optimized Hybrid Pixel Detectors
The Multi-Chip-Module-Deposited (MCM-D) technique has been used to build
hybrid pixel detector assemblies. This paper summarises the results of an
analysis of data obtained in a test beam campaign at CERN. Here, single chip
hybrids made of ATLAS pixel prototype read-out electronics and special sensor
tiles were used. They were prepared by the Fraunhofer Institut fuer
Zuverlaessigkeit und Mikrointegration, IZM, Berlin, Germany. The sensors
feature an optimized sensor geometry called equal sized bricked. This design
enhances the spatial resolution for double hits in the long direction of the
sensor cells.Comment: Contribution to Proceedings of Pixel2005 Workshop, Bonn Germany 200
Tests of silicon sensors for the CMS pixel detector
The tracking system of the CMS experiment, currently under construction at
the Large Hadron Collider (LHC) at CERN (Geneva, Switzerland), will include a
silicon pixel detector providing three spacial measurements in its final
configuration for tracks produced in high energy pp collisions. In this paper
we present the results of test beam measurements performed at CERN on
irradiated silicon pixel sensors. Lorentz angle and charge collection
efficiency were measured for two sensor designs and at various bias voltages.Comment: Talk presented at 6th International Conference on Large Scale
Applications and Radiation Hardness of Semiconductor Detectors, September
29-October 1, 2003, Firenze, Italy. Proceedings will be published in Nuclear
Instr. & Methods in Phys. Research, Section
Doprinosi dodatnih raspršenja međudjelovanju u konačnom stanju u (e, e ˇ ′p) reakcijama
A semiclassical model is employed to study the effects of rescattering on (e,e˘p) cross sections. We consider a two-step process with the propagation of an intermediate nucleon and use Glauber theory to account for the effects of N-N scattering. This calculation has relevance for the analysis of data at high missing energies. Of particular interest is the E97-006 experiment done at JLab. It is found that rescattering is strongly reduced in parallel kinematics and that the excitation of nucleon resonances is likely to give important contributions to the final-state interactions in the correlated region.Primjenjujemo poluklasičan model za proučavanje učinaka dodatnih raspršenja u udarnim presjecima reakcija (e,e′p). Razmatramo dvostruki proces s gibanjem međunukleona, a učinke N–N raspršenja uključujemo prema Glauberovoj teoriji. Ovi su računi važni za analize podataka pri velikim manjkovima energije. Posebno je zanimljivo mjerenje E97-006 u JLaboratoriju. Nalazimo jako smanjenje dodatnih raspršenja u usporednoj kinematici te vjerojatno velike doprinose od uzbude nukleonskih rezonancija međudjelovanju u konačnom stanju u koreliranom području
High-performance functional renormalization group calculations for interacting fermions
We derive a novel computational scheme for functional Renormalization Group
(fRG) calculations for interacting fermions on 2D lattices. The scheme is based
on the exchange parametrization fRG for the two-fermion interaction, with
additional insertions of truncated partitions of unity. These insertions
decouple the fermionic propagators from the exchange propagators and lead to a
separation of the underlying equations. We demonstrate that this separation is
numerically advantageous and may pave the way for refined, large-scale
computational investigations even in the case of complex multiband systems.
Furthermore, on the basis of speedup data gained from our implementation, it is
shown that this new variant facilitates efficient calculations on a large
number of multi-core CPUs. We apply the scheme to the , Hubbard model on
a square lattice to analyze the convergence of the results with the bond length
of the truncation of the partition of unity. In most parameter areas, a fast
convergence can be observed. Finally, we compare to previous results in order
to relate our approach to other fRG studies.Comment: 26 pages, 9 figure
Effect of kinematics on final state interactions in (e,e'p) reactions
Recent data from experiment E97-006 at TJNAF using the 12C(e,e'p) reaction at
very large missing energies and momenta are compared to a calculation of
two-step rescattering.
A comparison between parallel and perpendicular kinematics suggests that the
effects of final state interactions can be strongly reduced in the former case.Comment: 10 pages, 3 figures, submitted to LP
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