arXiv subjects

Simon Dalley

Publications and source records attributed to Simon Dalley.

5 recordsLinked to original sources

arXiv2012

Optimizing Polar Angle Asymmetry Observables at Colliders

Angular asymmetries are simple, intuitive, model-independent observables used to identify spins of new elementary particles. In the case of Drell-Yan-like boson resonances, we generalize the well-known center-edge angular asymmetry to optimize spin identification when only a limited sample of events is available. By choosing simple weight functions in integrals over the polar angle theta, such as cos theta to the nth power, we can improve spin discrimination significantly in production and decays of spin 0, 1, and 2 bosons. The power n can be tuned in particular cases, but n=2 (n=1) works well for any forward-backward symmetric (non-symmetric) decay to massless particles.

hep-ph↗

arXiv2002

The Relativistic Bound State Problem in QCD: Transverse Lattice Methods

The formalism for describing hadrons using a light-cone Hamiltonian of SU(N) gauge theory on a coarse transverse lattice is reviewed. Physical gauge degrees of freedom are represented by disordered flux fields on the links of the lattice. A renormalised light-cone Hamiltonian is obtained by making a colour-dielectric expansion for the link-field interactions. Parameters in the Hamiltonian are renormalised non-perturbatively by seeking regions in parameter space with enhanced Lorentz symmetry. In the case of pure gauge theories to lowest non-trivial order of the colour-dielectric expansion, this is sufficient to determine accurately all parameters in the large-N limit. We summarize results from applications to glueballs. After quarks are added, the Hamiltonian and Hilbert space are expanded in both dynamical fermion and link fields. Lorentz and chiral symmetry are not sufficient to accurately determine all parameters to lowest non-trivial order of these expansions. However, Lorentz symmetry and one phenomenological input, a chiral symmetry breaking scale, are enough to fix all parameters unambiguously. Applications to light-light and heavy-light mesons are described.

hep-ph↗

arXiv1996

The transverse lattice in 2+1 dimensions

Based on an idea due to Bardeen and Pearson, we formulate the light-front Hamiltonian problem for SU(N) Yang-Mills theory in 2+1 dimensions using two continuous space-time dimensions with the remaining space dimension discretized on a lattice. We employ analytic and numerical methods to investigate the string tension and the glueball spectrum in the large N limit. Our preliminary results show qualitative agreement with recent Euclidean lattice Monte Carlo simulations.

hep-ph↗

arXiv1995

Polymer Collapse on Fluctuating Random Surfaces

The conformations of interacting linear polymers on a dynamical planar random lattice are studied using a random two-matrix model. An exact expression for the partition function of self-avoiding chains subject to attractive contact interactions of relative strength $1/c$, $0<c<1$, is found as a function of chain length $L$ and $c$. The number of configurations $L^a {\rm e}^{bL}$ as $L\to \infty$ is determined, showing that a chain undergoes a third-order collapse transition at $c=\sqrt{2} -1$; the universal scaling laws are found.

cond-mat↗

arXiv1991

On Loop Equations In KdV Exactly Solvable String Theory

The non-perturbative behaviour of macroscopic loop amplitudes in the exactly solvable string theories based on the KdV hierarchies is considered. Loop equations are presented for the real non-perturbative solutions living on the spectral half-line, allowed by the most general string equation $[\tilde{P},Q]=Q$, where $\tilde{P}$ generates scale transformations. In general the end of the half-line (the `wall') is a non-perturbative parameter whose rôle is that of boundary cosmological constant. The properties are compared with the perturbative behaviour and solutions of $[P,Q]=1$. Detailed arguments are given for the $(2,2m-1)$ models while generalisation to the other $(p,q)$ minimal models and $c=1$ is briefly addressed.

hep-th↗