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 ($e,e'p$) reactions on $^{12}C$. 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 $4.7\times 10^{13}$ 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

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 $t$,$t'$ 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