Eric Braaten

Bio: Eric Braaten is an academic researcher from Ohio State University. The author has contributed to research in topics: Scattering length & Quantum chromodynamics. The author has an hindex of 63, co-authored 272 publications receiving 15295 citations. Previous affiliations of Eric Braaten include Brookhaven National Laboratory & University of Bonn.

Rigorous QCD analysis of inclusive annihilation and production of heavy quarkonium

Abstract: A rigorous QCD analysis of the inclusive annihilation decay rates of heavy quarkonium states is presented. The effective-field-theory framework of nonrelativistic QCD is used to separate the short-distance scale of annihilation, which is set by the heavy quark mass M, from the longer-distance scales associated with quarkonium structure. The annihilation decay rates are expressed in terms of nonperturbative matrix elements of four-fermion operators in nonrelativistic QCD, with coefficients that can be computed using perturbation theory in the coupling constant ${\mathrm{\ensuremath{\alpha}}}_{\mathit{s}}$(M). The matrix elements are organized into a hierarchy according to their scaling with v, the typical velocity of the heavy quark. An analogous factorization formalism is developed for the production cross sections of heavy quarkonium in processes involving momentum transfers of order M or larger. The factorization formulas are applied to the annihilation decay rates and production cross sections of S-wave states at next-to-leading order in ${\mathit{v}}^{2}$ and P-wave states at leading order in ${\mathit{v}}^{2}$.

Free energy of QCD at high temperature.

Abstract: Effective-field-theory methods are used to separate the free energy for a non-Abelian gauge theory at high temperature $T$ into the contributions from the momentum scales $T$, $\mathrm{gT}$, and ${g}^{2}T$, where $g$ is the coupling constant at the scale $2\ensuremath{\pi}T$. The effects of the scale $T$ enter through the coefficients in the effective Lagrangian for the three-dimensional effective theory obtained by dimensional reduction. These coefficients can be calculated as power series in ${g}^{2}$. The contribution to the free energy from the scale $\mathrm{gT}$ can be calculated using perturbative methods in the effective theory. It can be expressed as an expansion in $g$ starting at order ${g}^{3}$. The contribution from the scale ${g}^{2}T$ must be calculated using nonperturbative methods, but nevertheless it can be expanded in powers of $g$ beginning at order ${g}^{6}$. We calculate the free energy explicitly to order ${g}^{5}$. We also outline the calculations necessary to obtain the free energy to order ${g}^{6}$.

PYTHIA 6.4 Physics and Manual

Abstract: The Pythia program can be used to generate high-energy-physics ''events'', i.e. sets of outgoing particles produced in the interactions between two incoming particles. The objective is to provide as accurate as possible a representation of event properties in a wide range of reactions, within and beyond the Standard Model, with emphasis on those where strong interactions play a role, directly or indirectly, and therefore multihadronic final states are produced. The physics is then not understood well enough to give an exact description; instead the program has to be based on a combination of analytical results and various QCD-based models. This physics input is summarized here, for areas such as hard subprocesses, initial- and final-state parton showers, underlying events and beam remnants, fragmentation and decays, and much more. Furthermore, extensive information is provided on all program elements: subroutines and functions, switches and parameters, and particle and process data. This should allow the user to tailor the generation task to the topics of interest.

Theory of Bose-Einstein condensation in trapped gases

Abstract: The phenomenon of Bose-Einstein condensation of dilute gases in traps is reviewed from a theoretical perspective. Mean-field theory provides a framework to understand the main features of the condensation and the role of interactions between particles. Various properties of these systems are discussed, including the density profiles and the energy of the ground-state configurations, the collective oscillations and the dynamics of the expansion, the condensate fraction and the thermodynamic functions. The thermodynamic limit exhibits a scaling behavior in the relevant length and energy scales. Despite the dilute nature of the gases, interactions profoundly modify the static as well as the dynamic properties of the system; the predictions of mean-field theory are in excellent agreement with available experimental results. Effects of superfluidity including the existence of quantized vortices and the reduction of the moment of inertia are discussed, as well as the consequences of coherence such as the Josephson effect and interference phenomena. The review also assesses the accuracy and limitations of the mean-field approach.

Feshbach resonances in ultracold gases

Abstract: Feshbach resonances are the essential tool to control the interaction between atoms in ultracold quantum gases. They have found numerous experimental applications, opening up the way to important breakthroughs. This review broadly covers the phenomenon of Feshbach resonances in ultracold gases and their main applications. This includes the theoretical background and models for the description of Feshbach resonances, the experimental methods to find and characterize the resonances, a discussion of the main properties of resonances in various atomic species and mixed atomic species systems, and an overview of key experiments with atomic Bose-Einstein condensates, degenerate Fermi gases, and ultracold molecules.