F. Costantini

Glueball masses and string tension in lattice QCD

We study glueball masses in lattice QCD. We present the first numerical determination of the mass of the lowest spin 2 state in the scaling region, and find that it is close to the lowest spin 0 state. We present very precise results for the string tension and for the spin 0 state, obtained by analyzing a large set of operators. We find that finite size effects are significant.

The APE computer: An array processor optimized for lattice gauge theory simulations

Abstract The APE computer is a high performance processor designed to provide massive computational power for intrinsically parallel and homogeneous applications. APE is a linear array of processing elements and memory boards that execute in parallel in SIMD mode under the control of a CERN/SLAC 3081/E. Processing elements and memory boards are connected by a ‘circular’ switchnet. The hardware and software architecture of APE, as well as its implementation are discussed in this paper. Some physics results obtained in the simulation of lattice gauge theories are also presented.

GLUEBALL MASSES AND THE LOOP LOOP CORRELATION-FUNCTIONS

Abstract We analyse the pure gauge lattice QCD by measuring loop-loop correlation functions on a 12 3 ×32 lattice at β =5.9. We select a set of operators given by the smearing procedure. We obtain a good estimate of the mass of the 0 ++ state and for the string tension, and upper bounds for the masses of the 2 ++ and the 1 +− states.

SPACE CHARGE IN IONIZATION DETECTORS AND THE NA48 ELECTROMAGNETIC CALORIMETER

Abstract The subject of space charge due to positive ions slowly moving in parallel plate ionization chambers is considered. A model for the degradation of the detector response is developed, with particular emphasis on electromagnetic calorimeters.The topics discussed include: (a) the stationary; (b) the time dependent cases; (c) the limit of very large space charge; (d) the electric field dependence of the electron drift velocity; (e) the effect of longitudinal development of showers; (f) the behaviour of the average reductions of response; (g) the non-uniformity of response for different positions of the shower axis inside the cell defined by the electrodes. The NA48 calorimeter is used as application and for comparison of results.

The trigger for K0→π0π0 decays of the NA48 experiment at CERN

The trigger used for the collection of the samples of K0→π0π0 decays in the NA48 experiment at CERN uses a novel pipeline design in order to satisfy the demanding specifications of a high rate kaon beam. The trigger algorithms, architecture and performance are described.

Evidence for a resonant structure of the hadron production from e+e− annihilations in the 1700–1950 cm energy region

Abstract We present experimental evidence for a resonant behaviour of the hadron production from e + e − annihilations at the e + e − storage ring ADONE. A Breit-Wigner fit to the enhancement present between 1800 and 1850 MeV gives the following parameters M = 1812 −13 +7 MeV, Γ = 34 −15 +21 MeV.

Total cross section for hadron production by electron-positron annihilation at adone

Abstract The total cross section for electron-positron annihilation into three or more hadrons has been measured for centre of mass energies between 1.4 and 2.0 GeV. The data were obtained at ADONE by the BB experiment.

The PeakSum Processing System for the NA48 experiment: a VLSI based processor

The PeakSum Processing System (PSS) is an element of the neutral trigger of the NA48 experiment at CERN. The PSS is a pipelined processor based on a VLSI semi-custom device, containing all the processing blocks needed in the system. The PSS provides information on the energy pattern released in the electromagnetic calorimeter of the NA48 experiment, used to identify K/sub 0//spl rArr//spl pi//sup 0//spl pi//sup 0//spl rArr/4/spl gamma/ decays.

A 40 MHz-pipelined trigger for K0→2π0 decays for the CERN NA48 experiment

A first level trigger system based on a 40 MHz digital pipeline has been developed for the CERN NA48 [l] experiment, aiming at measuring CP violation in KO -+ 2n decays. The outputs of the 13340 cells of the 10 m3 liquid krypton calorimeter are summed into 64 X and 64 Y projection strips and continuously digitised with 40 MHz FADCs. This information is used to reconstruct at each clock cycle and for the two calorimeter projections, the number of clusters, the impact time of each of them (with a precision of about 3 ns), their total energy and the first and second moments of the energy distribution. Based on the quantities listed above, a programmable look-up table system subsequently computes online the longitudinal position of the kaon decay vertex and performs an event selection. The system is described.

A 40 MHz pipelined trigger for K/sup 0//spl rarr/2/spl pi//sup 0/ decays for the CERN NA48 experiment

A first level trigger system based on a 40 MHz digital pipeline has been developed for the CERN NA48 experiment, aiming at measuring CP violation in K/sup 0//spl rarr/2/spl pi/ decays. The outputs of the 13340 cells of the 10 m/sup 3/ liquid krypton calorimeter are summed into 64 X and 64 Y projection strips and continuously digitised with 40 MHz FADCs. This information is used to reconstruct at each clock cycle and for the two calorimeter projections, the number of clusters, the impact time of each of them (with a precision of about 3 ns), their total energy and the first and second moments of the energy distribution. Based on the quantities listed above, a programmable look-up table system subsequently computes online the longitudinal position of the kaon decay vertex and performs an event selection. The system is described.