36,960 research outputs found
Couplings in coupled channels versus wave functions: application to the X(3872) resonance
We perform an analytical study of the scattering matrix and bound states in
problems with many physical coupled channels. We establish the relationship of
the couplings of the states to the different channels, obtained from the
residues of the scattering matrix at the poles, with the wave functions for the
different channels. The couplings basically reflect the value of the wave
functions around the origin in coordinate space. In the concrete case of the
X(3872) resonance, understood as a bound state of \ddn and \ddc (and
), with the \ddn loosely bound, we find that the couplings to the two
channels are essentially equal leading to a state of good isospin I=0
character. This is in spite of having a probability for finding the \ddn
state much larger than for \ddc since the loosely bound channel extends
further in space. The analytical results, obtained with exact solutions of the
Schr\"odinger equation for the wave functions, can be useful in general to
interpret results found numerically in the study of problems with unitary
coupled channels methods.Comment: 14 pages, 4 figure
Isospin breaking effects in the dynamical generation of the X(3872)
We have studied isospin breaking effects in the X(3872) resonance and found a
natural explanation for the branching fraction of the X decaying to
with two and three pions being close to unit. Within our framework the X(3872)
is a dynamically generated resonance in coupled channels. We also study the
relationship between the couplings of the resonance to the coupled channels
with its wave function, which further helps us to understand the isospin
structure of the resonance.Comment: 5 pages, 1 figure. To appear in the Proceedings of XIII International
Conference on Hadron Spectroscopy, November 29 - December 4, 2009, Florida
State Universit
Properties of Gamma-Ray Burst Time Profiles Using Pulse Decomposition Analysis
The time profiles of many gamma-ray bursts consist of distinct pulses, which
offers the possibility of characterizing the temporal structure of these bursts
using a relatively small set of pulse shape parameters. This pulse
decomposition analysis has previously been performed on a small sample of
bright long bursts using binned data from BATSE, which comes in several data
types, and on a sample of short bursts using the BATSE Time-Tagged Event (TTE)
data type. We have developed an interactive pulse-fitting program using the
phenomenological pulse model of Norris, et al. and a maximum-likelihood fitting
routine. We have used this program to analyze the Time-to-Spill (TTS) data for
all bursts observed by BATSE up through trigger number 2000, in all energy
channels for which TTS data is available. We present statistical information on
the attributes of pulses comprising these bursts, including relations between
pulse characteristics in different energy channels and the evolution of pulse
characteristics through the course of a burst. We carry out simulations to
determine the biases that our procedures may introduce. We find that pulses
tend to have shorter rise times than decay times, and tend to be narrower and
peak earlier at higher energies. We also find that pulse brightness, pulse
width, and pulse hardness ratios do not evolve monotonically within bursts, but
that the ratios of pulse rise times to decay times tend to decrease with time
within bursts.Comment: 40 pages, 19 figures. Submitted to Astrophysical Journal. PostScript
and PDF with un-bitmapped figures available at
http://www.slac.stanford.edu/pubs/slacpubs/8000/slac-pub-8364.html .
Accompanying paper astro-ph/0002218 available at
http://www.slac.stanford.edu/pubs/slacpubs/8000/slac-pub-8365.htm
- …