2,433 research outputs found
A new approach to calculate the transport matrix in RF cavities
A realistic approach to calculate the transport matrix in RF cavities is
developed. It is based on joint solution of equations of longitudinal and
transverse motion of a charged particle in an electromagnetic field of the
linac. This field is a given by distribution (measured or calculated) of the
component of the longitudinal electric field on the axis of the linac. New
approach is compared with other matrix methods to solve the same problem. The
comparison with code ASTRA has been carried out. Complete agreement for
tracking results for a TESLA-type cavity is achieved. A corresponding algorithm
will be implemented into the MARS15 code.Comment: 4 pp. Particle Accelerator, 24th Conference (PAC'11) 2011. 28 Mar - 1
Apr 2011. New York, US
The new Magnetic Measurement System at the Advanced Photon Source
A new system for precise measurements of the field integrals and multipole
components of the APS magnetic insertion devices is described. A stretched coil
is used to measure magnetic field characteristics. The hardware includes a
number of servomotors to move (translate or rotate) the coil and a fast data
acquisition board to measure the coil signal. A PC under Linux is used as a
control workstation. The user interface is written as a Tcl/tk script. The
hardware is accessed from the script through a shared C-library. A description
of the hardware system and the control program is given.Comment: 3 pages, 5 figures, paper 3271 submitted to ICALEPCS 2001 Conferenc
Gravitational Corrections to the Energy-Levels of a Hydrogen Atom
The first order perturbations of the energy levels of a hydrogen atom in
central internal gravitational field are investigated. The internal
gravitational field is produced by the mass of the atomic nucleus. The energy
shifts are calculated for the relativistic 1S, 2S, 2P, 3S, 3P, 3D, 4S and 4P
levels with Schwarzschild metric. The calculated results show that the
gravitational corrections are sensitive to the total angular momentum quantum
number.Comment: 7 page
The running mass at low scalefrom the heavy-light meson decay constants
It is shown that a 25(20)% difference between the decay constants
and occurs due to large differences in the pole
masses of the and quarks. The values , recently observed in the CLEO experiment, and
, obtained in unquenched lattice QCD, can be
reached only if the running mass at low scale is GeV) MeV. Our results follow from the analytical expression for the
pseudoscalar decay constant based on the path-integral
representation of the meson Green's function.Comment: 6 pages, no figures; revtex
Regarding the axial-vector mesons
The implications of the mixing for the
mixing angle is investigated. Based on the
mixing angle suggested from the analysis
for a substantial body of data concerning the and , the
masses of the and are determined to be MeV and MeV, respectively, which therefore
suggests that the mixing angle is about . Also, it is found that the mass of the
(mostly of ) state is about MeV. Comparison of the
predicted results and the available experimental information of the
shows that without further confirmation on the , the assignment of
the as the member of the meson nonet may be
premature.Comment: 11 pages, some typos corrected, accepted for publication in Eur.
Phys. J.
A tracking algorithm for the stable spin polarization field in storage rings using stroboscopic averaging
Polarized protons have never been accelerated to more than about GeV. To
achieve polarized proton beams in RHIC (250GeV), HERA (820GeV), and the
TEVATRON (900GeV), ideas and techniques new to accelerator physics are needed.
In this publication we will stress an important aspect of very high energy
polarized proton beams, namely the fact that the equilibrium polarization
direction can vary substantially across the beam in the interaction region of a
high energy experiment when no countermeasure is taken. Such a divergence of
the polarization direction would not only diminish the average polarization
available to the particle physics experiment, but it would also make the
polarization involved in each collision analyzed in a detector strongly
dependent on the phase space position of the interacting particle. In order to
analyze and compensate this effect, methods for computing the equilibrium
polarization direction are needed. In this paper we introduce the method of
stroboscopic averaging, which computes this direction in a very efficient way.
Since only tracking data is needed, our method can be implemented easily in
existing spin tracking programs. Several examples demonstrate the importance of
the spin divergence and the applicability of stroboscopic averaging.Comment: 39 page
Measurement of the neutron lifetime using a gravitational trap and a low-temperature Fomblin coating
We present a new value for the neutron lifetime of 878.5 +- 0.7 stat. +- 0.3
syst. This result differs from the world average value (885.7 +- 0.8 s) by 6.5
standard deviations and by 5.6 standard deviations from the previous most
precise result. However, this new value for the neutron lifetime together with
a beta-asymmetry in neutron decay, Ao, of -0.1189(7) is in a good agreement
with the Standard Model.Comment: 11 pages, 9 figures; extended content with some correction
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