4,718 research outputs found
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
New results in rho^0 meson physics
We compare the predictions of a range of existing models based on the Vector
Meson Dominance hypothesis with data on e^+ e^- -> pi^+ pi^$ and e^+ e^- ->
mu^+ mu^- cross-sections and the phase and near-threshold behavior of the
timelike pion form factor, with the aim of determining which (if any) of these
models is capable of providing an accurate representation of the full range of
experimental data. We find that, of the models considered, only that proposed
by Bando et al. is able to consistently account for all information, provided
one allows its parameter "a" to vary from the usual value of 2 to 2.4. Our fit
with this model gives a point-like coupling (gamma pi^+ \pi^-) of magnitude ~
-e/6, while the common formulation of VMD excludes such a term. The resulting
values for the rho mass and pi^+ pi^- and e^+e^- partial widths as well as the
branching ratio for the decay omega -> pi^+ pi^- obtained within the context of
this model are consistent with previous results.Comment: 34 pages with 7 figures. Published version also available at
http://link.springer.de/link/service/journals/10052/tocs/t8002002.ht
Exploratory spectrum calculations using overlap valence quarks on a staggered sea
We present exploratory results for the hadron mass spectrum and pseudoscalar
meson decay constants using mixed actions. We use improved staggered sea quarks
and HYP-smeared overlap valence quarks. We obtain good signals on 10
configurations at one lattice spacing and two different sets of sea quark
masses.Comment: Lattice2004(spectrum), 3pages, 4 figure
decays
Effective chiral theory of mesons is applied to study the four decay modes of
. Theoretical values of the branching ratios are in
agreement with the data. The theory predicts that the resonance plays a
dominant role in these decays. There is no new parameter in this study.Comment: 12 pages and one figur
MesonNet Workshop on Meson Transition Form Factors
The mini-proceedings of the Workshop on Meson Transition Form Factors held in
Cracow from May 29th to 30th, 2012 introduce the meson transition form factor
project with special emphasis on the interrelations between the various form
factors (on-shell, single off-shell, double off-shell). Short summaries of the
talks presented at the workshop follow.Comment: 69 pages, 14 figures; all talks can be found at
https://sites.google.com/site/mesonnetwork/home/activities/form-factor-workshop-2012;
v2: workshop link updated (as the page had to be moved to a commercial
server), table 6 correcte
The running of the electromagnetic coupling alpha in small-angle Bhabha scattering
A method to determine the running of alpha from a measurement of small-angle
Bhabha scattering is proposed and worked out. The method is suited to high
statistics experiments at e+e- colliders, which are equipped with luminometers
in the appropriate angular region. A new simulation code predicting small-angle
Bhabha scattering is also presentedComment: 15 pages, 3 Postscript figure
Static observables of relativistic three-fermion systems with instantaneous interactions
We show that static properties like the charge radius and the magnetic moment
of relativistic three-fermion bound states with instantaneous interactions can
be formulated as expectation values with respect to intrinsically defined
wavefunctions. The resulting operators can be given a natural physical
interpretation in accordance with relativistic covariance. We also indicate how
the formalism may be generalized to arbitrary moments. The method is applied to
the computation of static baryon properties with numerical results for the
nucleon charge radii and the baryon octet magnetic moments. In addition we make
predictions for the magnetic moments of some selected nucleon resonances and
discuss the decomposition of the nucleon magnetic moments in contributions of
spin and angular momentum, as well as the evolution of these contributions with
decreasing quark mass.Comment: 13 pages, including 2 figures and 3 tables, submitted to Eur.Phys.J.
Correlation between Leptonic CP Violation and mu-tau Symmetry Breaking
Considering the - symmetry, we discuss a direct linkage between
phases of flavor neutrino masses and leptonic CP violation by determining three
eigenvectors associated with for a complex
flavor neutrino mass matrix in the flavor basis. Since the Dirac CP
violation is absent in the - symmetric limit, leptonic CP violation
is sensitive to the - symmetry breaking, whose effect can be
evaluated by perturbation. It is found that the Dirac phase () arises
from the - symmetry breaking part of and
an additional phase () is associated with the - symmetric part
of , where stands for an matrix
element (=). The phase is redundant and can be removed
but leaves its effect in the Dirac CP violation characterized by . The perturbative results suggest the exact formula of mixing
parameters including that of and , which turns out to be free
from the effects of the redundant phases. As a result, it is generally shown
that the maximal atmospheric neutrino mixing necessarily accompanies either
or , the latter of which indicates
maximal CP violation, where is the - mixing
angle.Comment: 16 pages, ReVTeX, references updated, typos corredcted, published
version in Physical Reviews
Radiative muon pair production in high energy electron-positron annihilation process
The lowest order radiative correction to the differential cross-section of
process of muon pair production with emission of hard photon at high energy
electron-positron annihilation are calculated. Taking into account the emission
of additional soft and hard photon the cross-section can be put in the form of
Drell-Yan process in leading logarithmical approximation. Applying the crossing
transformation we obtain the cross section of radiative electron-muon
high-energy scattering process. Virtual and soft photon emission contributions
of non-leading form are tabulated for several typical kinematical points. The
limit of small invariant mass of muon pair is in agreement with our previous
analysis.Comment: 9 pages, 2 figure
- …