1,978 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
Scales Set by the Cosmological Constant
The cosmological constant sets certain scales important in cosmology. We show
that Lambda in conjunction with other parameters like the Schwarzschild radius
leads to scales relevant not only for cosmological but also for astrophysical
applications. Of special interest is the extension of orbits and velocity of
test particles traveling over Mpc distances. We will show that there exists a
lower and an upper cut-off on the possible velocities of test particles. For a
test body moving in a central gravitational field Lambda enforces a maximal
value of the angular momentum if we insist on bound orbits of the test body
which move at a distance larger than the Schwarzschild radius.Comment: 15 pages, 2 figures, 1 table; one reference adde
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