119442708
Gauge-invariant variational methods for Hamiltonian lattice gauge theories
This paper develops variational methods for calculating the ground-state and excited-state spectrum of Hamiltonian lattice gauge theories defined in the A/sub 0/ = 0 gauge. The scheme introduced in this paper has the advantage of allowing one to convert more familiar tools such as mean-field, Hartree-Fock, and real-space renormalization-group approximation, which are by their very nature gauge-noninvariant methods, into fully gauge-invariant techniques. We show that these methods apply in the same way to both Abelian and non-Abelian theories, and that they are at least powerful enough to describe correctly the physics of periodic quantum electrodynamics (PQED) in (2+1) and (3+1) space-time dimensions. This paper formulates the problem for both Abelian and non-Abelian theories and shows how to reduce the Rayleigh-Ritz problem to that of computing the partition function of a classical spin system. We discuss the evaluation of the effective spin problem which one derives the PQED and then discuss ways of carrying out the evaluation of the partition function for the system equivalent to a non-Abelian theory. The explicit form of the effective partition function for the non-Abelian theory is derived, but because the evaluation of this function is considerably more complicated than the one derived in the Abelianmore » theory no explicit evaluation of this function is presented. However, by comparing the gauge-projected Hartree-Fock wave function for PQED with that of the pure SU(2) gauge theory, we are able to show that extremely interesting differences emerge between these theories even at this simple level. We close with a discussion of fermions and a discussion of how one can extend these ideas to allow the computation of the glueball and hadron spectrum.« less
109663075
Using a neural network approach for muon reconstruction and triggering
The extremely high rate of events that will be produced in the future Large Hadron Collider requires the triggering mechanism to take precise decisions in a few nano-seconds. We present a study which used an artificial neural network triggering algorithm and compared it to the performance of a dedicated electronic muon triggering system. Relatively simple architecture was used to solve a complicated inverse problem. A comparison with a realistic example of the ATLAS first level trigger simulation was in favour of the neural network. A similar architecture trained after the simulation of the electronics first trigger stage showed a further background rejection.
119545141
MANY PARTICLE PRODUCTION
Abstract Recent developments in the theoretical and experimental analysis of many-particle production are discussed. After a summary of the main characteristics of the high energy reactions, we discuss the features of the multiperipheral model as an introduction to the recent theoretical developments. The longitudinal kinematics and some of their manifestations in the behaviour of cross-sections are reviewed before turning to the concepts of scaling and limiting fragmentation. The implications of these approaches are compared with available experimental data. This leads to the Reggeistic picture developed in Mueller's analysis. Its results are reviewed and analyzed in the regions of limiting fragmentation and pionization. Separate sections are then devoted to the triple-Regge limit and to diffraction dissociation. We close with a section on correlations, pointing out open problems for future research.
120471536
Analysis of the Mueller-Regge model☆
Abstract Asymptotic results of the Mueller-Regge model (MRM) are obtained in the fixed n limit and in the fixed n / Y limit. A two-component MRM is analyzed and its predictions, in particular for semi-inclusive correlations, are compared with the asymptotic expressions. The deficiencies of the various approximations are discussed.
39663223
Frustrated spin Hamiltonians with binary input vectors.
Structures of composite spin operators are analyzed which appear in models of neural networks of the type which Amit et al. have recently investigated. A binary basis of size N${=2}^{M}$ is introduced to study a problem of N quantum-mechanical spin operators. The [Z${(2)]}^{M}$ group structure of the binary basis allows for many decompositions of the [SU(2)${]}^{\mathrm{N}}$ spin algebra. These become useful in studying and solving generalized frustrated Heisenberg as well as Ising models. Using these techniques for quantum-mechanical generalized spin operators, we derive an explicit representation of the partition function of classical statistical-mechanics models, in terms of a series summation over components of collective spin variables.
122621587
MESON AND BARYON RESONANCES IN RELATIVISTIC SU(6)
118159758
Study of $B^{0}_{s} \rightarrow D_s^{(*)+}D_s^{(*)-}$ and $B^{0}_{s} \rightarrow \phi\phi$ Decays at CDF
Under certain theoretical assumptions, the branching fraction of B{sub s}{sup 0} {yields} D{sub s}{sup (*)+}D{sub s}{sup (*)-} is directly sensitive to the relative decay width difference {Delta}{Lambda}{sub s}{sup CP}/{Lambda}{sub s} in the B{sub s}{sup 0} system, which is predicted to be sizable in the standard model. Using approximately 4 fb{sup -1} of data collected by the CDF II detector at the Tevatron p{bar p} collider, the CDF collaboration is currently performing an exclusive selection of B{sub s}{sup 0} {yields} D{sub s}{sup (*)+}D{sub s}{sup (*)-} signal candidates in several hadronic modes in order to provide a new branching fraction measurement. In contrast to former analyses, we start to have sensitivity in disentangling D{sub s}{sup (*)+}D{sub s}{sup (*)-}, enabling us to measure the branching fractions of B{sub s}{sup 0} {yields} D{sub s}{sup +}D{sub s}{sup -}, B{sub s}{sup 0} {yields} D{sub s}{sup (*)+}D{sub s}{sup -} and B{sub s}{sup 0} {yields} D{sub s}{sup (*)+}D{sub s}{sup (*)-} separately. Yet another interesting mode is the decay of the B{sub s}{sup 0} into a {phi} pair. This is a vector-vector decay dominated by the b {yields} s{ovr ss} penguin transition, which is a sensitive probe for possible new physics effects. Here we present a new measurement ofmore » the branching fraction based on a clean sample of about 300 B{sub s}{sup 0} {yields} {phi}{phi} signal events in a dataset with an integrated luminosity of 2.9 fb{sup -1}.« less
125542777
Measurement of the Exclusive and Inclusive Branching Fractions of $B^{0}_{s} \to D^{(*)+}_{s}D^{(*)-}_{s}$ Decays at CDF and its Implications on the Decay Width Difference in the $B^{0}_{s}-B^{-0}_{s}$ Meson System