1,744 research outputs found
Dalitz Plot Analysis of B- --> D+ pi- pi-
We present a Dalitz plot analysis of B- --> D+ pi- pi- decays, based on a
sample of about 383 million Y(4S) --> BBbar decays collected by the BaBar
detector at the PEP-II asymmetric-energy B Factory at SLAC. The analysis has
been published previously in PRD. We measure the inclusive branching fraction
of the three-body decay to be BR(B- --> D+ pi- pi-) = (1.08 \pm 0.03\stat \pm
0.05\syst) x 10^{-3}$. We observe the established D^{*0}_2 and confirm the
existence of D^{*0}_0 in their decays to D+ pi-, where the D^{*0}_2 and
D^{*0}_0 are the 2+ and 0+ c-ubar P-wave states, respectively. We measure the
masses and widths of D^{*0}_2 and D^{*0}_0 to be: m_{D^{*}_2} = (2460.4 \pm 1.2
\pm 1.2 \pm 1.9) MeV/c^2, Gamma_{D^*_2} = (41.8 \pm 2.5 \pm 2.1 \pm 2.0) MeV,
m_{D^{*}_0} = (2297 \pm 8 \pm 5 \pm 19) MeV/c^2, Gamma_{D^*_0} = (273 \pm 12
\pm 17 \pm 45) MeV. The stated errors reflect the statistical and systematic
uncertainties, and the uncertainty related to the assumed composition of signal
events and the theoretical model.Comment: 5 pages, 7 PDF figures, uses AIP style, conference proceedings of
HADRON09, to be published in AIP Conference Proceedings, arXiv:0901.129
Quasiparticles governing the zero-temperature dynamics of the 1D spin-1/2 Heisenberg antiferromagnet in a magnetic field
The T=0 dynamical properties of the one-dimensional (1D)
Heisenberg antiferromagnet in a uniform magnetic field are studied via Bethe
ansatz for cyclic chains of sites. The ground state at magnetization
, which can be interpreted as a state with spinons or as a
state of magnons, is reconfigured here as the vacuum for a different
species of quasiparticles, the {\em psinons} and {\em antipsinons}. We
investigate three kinds of quantum fluctuations, namely the spin fluctuations
parallel and perpendicular to the direction of the applied magnetic field and
the dimer fluctuations. The dynamically dominant excitation spectra are found
to be sets of collective excitations composed of two quasiparticles excited
from the psinon vacuum in different configurations. The Bethe ansatz provides a
framework for (i) the characterization of the new quasiparticles in relation to
the more familiar spinons and magnons, (ii) the calculation of spectral
boundaries and densities of states for each continuum, (iii) the calculation of
transition rates between the ground state and the dynamically dominant
collective excitations, (iv) the prediction of lineshapes for dynamic structure
factors relevant for experiments performed on a variety of quasi-1D
antiferromagnetic compounds, including KCuF,
Cu(CHN, and CuGeO.Comment: 13 pages, 12 figure
A numerical study of the formation of magnetisation plateaus in quasi one-dimensional spin-1/2 Heisenberg models
We study the magnetisation process of the one dimensional spin-1/2
antiferromagnetic Heisenberg model with modulated couplings over j=1,2,3 sites.
It turns out that the evolution of magnetisation plateaus depends on j and on
the wave number q of the modulation according to the rule of Oshikawa, et al. A
mapping of two- and three-leg zig-zag ladders on one dimensional systems with
modulated couplings yields predictions for the occurence of magnetization
plateaus. The latter are tested by numerical computations with the DMRG
algorithm.Comment: 7 pages, 10 figures, accepted for publication in Euro. Phys. J.
Spinon excitations in the XX chain: spectra, transition rates, observability
The exact one-to-one mapping between (spinless) Jordan-Wigner lattice
fermions and (spin-1/2) spinons is established for all eigenstates of the
one-dimensional s = 1=2 XX model on a lattice with an even or odd number N of
lattice sites and periodic boundary conditions. Exact product formulas for the
transition rates derived via Bethe ansatz are used to calculate asymptotic
expressions of the 2-spinon and 4-spinon parts (for large even N) as well as of
the 1-spinon and 3-spinon parts (for large odd N) of the dynamic spin structure
factors. The observability of these spectral contributions is assessed for
finite and infinite N.Comment: 19 pages, 10 figure
Spectrum and transition rates of the XX chain analyzed via Bethe ansatz
As part of a study that investigates the dynamics of the s=1/2 XXZ model in
the planar regime |Delta|<1, we discuss the singular nature of the Bethe ansatz
equations for the case Delta=0 (XX model). We identify the general structure of
the Bethe ansatz solutions for the entire XX spectrum, which include states
with real and complex magnon momenta. We discuss the relation between the
spinon or magnon quasiparticles (Bethe ansatz) and the lattice fermions
(Jordan-Wigner representation). We present determinantal expressions for
transition rates of spin fluctuation operators between Bethe wave functions and
reduce them to product expressions. We apply the new formulas to two-spinon
transition rates for chains with up to N=4096 sites.Comment: 11 pages, 4 figure
Lattice two-body problem with arbitrary finite range interactions
We study the exact solution of the two-body problem on a tight-binding
one-dimensional lattice, with pairwise interaction potentials which have an
arbitrary but finite range. We show how to obtain the full spectrum, the bound
and scattering states and the "low-energy" solutions by very efficient and
easy-to-implement numerical means. All bound states are proven to be
characterized by roots of a polynomial whose degree depends linearly on the
range of the potential, and we discuss the connections between the number of
bound states and the scattering lengths. "Low-energy" resonances can be located
with great precission with the methods we introduce. Further generalizations to
include more exotic interactions are also discussed.Comment: 6 pages, 3 figure
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