R. W. Rusack

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 hadronic mass spectrum in quenched lattice QCD: β=5.7

Abstract We compute the QCD hadronic mass spectrum in quenched lattice QCD at β=5.7 with small statistical and systematic errors by using the APE computer.

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.

A photomultiplier tube incorporating an avalanche photodiode

Abstract A photomultiplier tube incorporating an avalanche photodiode operated in the electron bombardment mode has been developed and tested. It has a large linear dynamic range, can operate with gains up to 10 6 , is unaffected by axial magnetic fields and has been measured to have excellent timing properties. Different versions of the tube were made with bialkali, multi-alkali, and negative electron affinity photocathodes, in this paper we will report on results obtained with these different types of photocathodes. This type of PMT will be useful for applications where large dynamic range and high quantum efficiencies are required. The extension of this concept to a multichannel device with a segmented APD array will provide an economical readout for both fiber tracking and calorimetry applications. A tube equipped with such an array is being developed currently as a readout option for the SDC shower maximum detector.

The deconfining phase transition in lattice gauge SU(3)

Abstract By using a source method and improved measuring techniques, we study the decay of the Polyakov loop in SU(3) lattice gauge theory at finite temperature. Our aim is to measure the correlation length of the system in the neighbourhood of the critical point. We work with lattices of size up to 162×64×4. We found that the maximum correlation length is only bounded by the spatial dimension of the lattice. This result is the one expected in a second order phase transition and appears to be incompatible with the presence of the strong first order transition claimed in the literature.

Observation of jet structure in high transverse energy events at the CERN intersecting storage rings

Abstract The spectrum d N d E T 0 ( E T 0 = neutral transverse energy) has been measured with an electromagnetic calorimeter covering 90% of 2 π in azimuth. The measurement, performed in pp collisions at s = 62 GeV , covered the E T 0 range from 10 to 30 GeV. Evidence is presented that a large fraction of these events are jet-like, the fraction increasing with E T 0 .

A measurement of the inclusive π0 and η production cross sections at high pT in p̄p and pp collisions at s = 24.3 GeV

Abstract Inclusive π 0 and η production at large transverse momentum were studied in both pp and pp interactions at √ s = 24.3 GeV. The experiment was performed using an internal molecular hydrogen gas jet target in the CERN SPS collider. No significant differences between production in pp and pp were observed in the transverse momentum range 2.5 P T c .

The total neutral energy spectra in the central region of α−α, d−d and p−p interactions at sNN = 31 GeV per nucleon pair at the CERN ISR

The spectra in total neutral energy, ETOT0, have been measured in pp, dd and αα collisions at centre-of-mass energy per nucleon pair, sNN, of 31 GeV. The range in ETOT0 covered was 1 to 19 GeV in pp, 18 to 24 GeV in dd and 1 to 34 GeV in αα interactions. The ratio of the αα to the pp spectra rises monotonically from 7 at ETOT0 = 1.5 GeV to 105 at ETOT 0 = 19 GeV. Since ETOT0 is the sum over many particles in the detector, it is directly sensitive to multiple nucleon-nucleon collisions in the interacting α particles. The αα spectrum in the range 8 < ETOT0 < 17 GeV is consistent with being described by a simple model of 4 simultaneous nucleon-nucleon collisions with a cross section about equal to 10% of the observed αα interaction cross section. The spectrum of ETOT0 above 17 GeV is even flatter than this extreme case where four nucleon pairs are interacting.

Observation of KNO scaling in the neutral energy spectra from αα and pp collisions at ISR energies

Abstract Neutral transverse energy spectra in pp and αα interactions are analyzed in terms of the wounded nucleon model. Analysis of the αα spectrum by application of a multiple nucleon-nucleon collision mechanism is conveniently performed when a gamma distribution is used to represent the pp spectral shape. The wounded nucleon model provides a reasonable description of the αα spectrum for the first three orders of magnitude, but completly fails to account for the slope of the high energy tail of the distribution. However, the pp and αα spectra can both be fitted to the same gamma distribution when scaled by their respective mean values and thus exhibit KNO scaling.