1,197 research outputs found
The Use of the Scattering Phase Shift in Resonance Physics
The scattering phase shift encodes a good amount of physical information
which can be used to study resonances from scattering data. Among others, it
can be used to calculate the continuum density of states and the collision time
in a resonant process. Whereas the first information can be employed to examine
the evolution of unstable states directly from scattering data, the second one
serves as a tool to detect resonances and their properties. We demonstrate both
methods concentrating in the latter case on 'exotic' resonances in pi-pi and
pi-K scattering.Comment: Talk given at the International Workshop PENTAQUARK04, July 20-23 at
Spring-8, Japan (new references added
Faraday's law in the presence of magnetic monopoles
We show that if we consider the full statement of Faraday's law for a closed
physical circuit, the standard Maxwell's equations in the presence of electric
and magnetic charges have to include in their integral form a mixed term of the
form where is the magnetic charge density
and the perpendicular component of the velocity
of the electric charge.Comment: 9 page
Pentaquark Resonances from Collision Times
Having successfully explored the existing relations between the S-matrix and
collision times in scattering reactions to study the conventional baryon and
meson resonances, the method is now extended to the exotic sector. To be
specific, the collision time in various partial waves of K+ N elastic
scattering is evaluated using phase shifts extracted from the K+ N --> K+ N
data as well as from model dependent T-matrix solutions. We find several
pentaquark resonances including some low-lying ones around 1.5 to 1.6 GeV in
the P_01, P_03 and D_03 partial waves of K+ N elastic scattering.Comment: Talk given at the International Workshop PENTAQUARK04, July 20-23 at
Spring-8, Japa
Extraction of the proton charge radius from experiments
Static properties of hadrons such as their radii and other moments of the
electric and magnetic distributions can only be extracted using theoretical
methods and not directly measured from experiments. As a result, discrepancies
between the extracted values from different precision measurements can exist.
The proton charge radius, , which is either extracted from electron proton
elastic scattering data or from hydrogen atom spectroscopy seems to be no
exception. The value fm extracted from muonic hydrogen
spectroscopy is about 4% smaller than that obtained from electron proton
scattering or standard hydrogen spectroscopy. The resolution of this so called
proton radius puzzle has been attempted in many different ways over the past
six years. The present article reviews these attempts with a focus on the
methods of extracting the radius.Comment: Mini review, 14 pages, 1 figur
Development of generalized block correction procedures for the solution of discretized Navier-Stokes equations
Effort is directed towards developing a solution method which combines advantages of both the iterative and the direct methods. It involves iterative solution on the fine grid, convergence of which is enhanced by a direct solution for correction quantities on a coarse grid. The proposed block correction procedure was applied to compute recirculating flow in a driven cavity
Mechanical behavior of polycrystalline ceramics: Brittle fracture of SiC-Si3N4 materials
The first study area involved magnesium oxide and the role of anion impurities, while the second area was directed toward slow crack growth in silicon nitride-silicon carbide ceramics. The oxide program involved development of fabrication techniques for anion doped materials and evaluation of the role of these anions in the hot pressing response, grain boundary diffusion of nickel doped material, grain boundary microhardness, and grain growth
Small eta-N scattering lengths favour eta-d and eta-alpha states
Unstable states of the eta meson and the 3He nucleus predicted using the time
delay method were found to be in agreement with a recent claim of eta-mesic 3He
states made by the TAPS collaboration. Here, we extend this method to a
speculative study of the unstable states occurring in the eta-d and eta-4He
elastic scattering. The T-matrix for eta-4He scattering is evaluated within the
Finite Rank Approximation (FRA) of few body equations. For the evaluation of
time delay in the eta-d case, we use a parameterization of an existing Faddeev
calculation and compare the results with those obtained from FRA. With an eta-N
scattering length, fm, we find an eta-d unstable
bound state around -16 MeV, within the Faddeev calculation. A similar state
within the FRA is found for a low value of , namely, fm. The existence of an eta-4He unstable bound state close to
threshold is hinted by fm, but is ruled out by
large scattering lengths.Comment: 21 pages, LaTex, 7 Figure
Determining the size of the proton
A measurement of the Lamb shift of 49,881.88(76) GHz in muonic hydrogen in
conjunction with theoretical estimates of the proton structure effects was
recently used to deduce an accurate but rather small radius of the proton. Such
an important shift in the understanding of fundamental values needs
reconfirmation. Using a different approach with electromagnetic form factors of
the proton, we obtain a new expression for the transition energy, , in muonic hydrogen and deduce
a proton radius, fm.Comment: 20 pages LaTe
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