4,384 research outputs found
Precision Measurements of the Semileptonic Charm Decays and
We investigate the decays and ,
where is or , using approximately 7 of data
collected with the CLEO III detector. We find . Fits to
the kinematic distributions of the data provide parameters describing the form
factor of each mode. Combining the form factor results and gives
.Comment: 5 pages, 2 figures, talk given at DPF'04, UC Riverside, C
Theoretical precision in estimates of the hadronic contributions to (g-2)_mu and alpha_QED(M_Z)
I review recent estimates of the non-perturbative hadronic vacuum
polarization contributions. Since these at present can only be evaluated in
terms of experimental data of limited precision, the related uncertainties pose
a serious limitation in our ability to make precise predictions. Besides e+e- -
annihilation data also tau decay spectra can help to get better predictions.
Here, it is important to account for all possible iso-spin violations in tau -
decay spectra, from which e+e- cross sections may be obtained by an iso-spin
rotation. The observed 10% discrepancy in the region above the rho may be
understood as a so far unaccounted iso-spin breaking effect.Comment: 10 pages, 2 tables, 4 figure
Colliding neutrino beams
From several neutrino oscillation experiments, we understand now that
neutrinos have mass. However, we really don't know what mechanism is
responsible for producing this neutrino mass. Current or planned neutrino
experiments utilize neutrino beams and long-baseline detectors to explore
flavor mixing but do not address the question of the origin of neutrino mass.
In order to answer that question, neutrino interactions need to be explored at
much higher energies. This paper outlines a program to explore neutrinos and
their interactions with various particles through a series of experiments
involving colliding neutrino beams.Comment: 29 pages, submitted to Phys. Rev. D; updated contents, added 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
Dark Matter Constraints on Gaugino/Higgsino Masses in Split Supersymmetry and Their Implications at Colliders
In split supersymmetry, gauginos and Higgsinos are the only supersymmetric
particles which are possibly accessible at foreseeable colliders. While the
direct experimental searches, such as LEP and Tevatron experiments, gave robust
lower bounds on the masses of these particles, the cosmic dark matter can give
some upper bounds and thus have important implications for the searches at
future colliders. In this work we scrutinize such dark matter constraints and
show the allowed mass range for charginos and neutralinos (the mass eigenstates
of gauginos and Higgsinos). We find that the lightest chargino must be lighter
than about 1 TeV under the popular assumption M_1=M_2/2 and about 2 or 3 TeV in
other cases. The corresponding production rates of the lightest chargino at the
CERN Large Hadron Collider (LHC) and the International Linear Colldier (ILC)
are also shown. While in some parts of the allowed region the chargino pair
production rate can be larger than 1 pb at LHC and 100 fb at the ILC, other
parts of the region correspond to very small production rates and thus there is
no guarantee to find the charginos of split supersymmetry at future colliders.Comment: version in EPJC (refs added
Forward dispersion relations and Roy equations in pi-pi scattering
We review results of an analysis of pipi interactions in S, P and D waves for
two-pion effective mass from threshold to about 1.4 GeV. In particular we show
a recent improvement of this analysis above the K anti-K threshold using more
data for phase shifts and including the S0 wave inelasticity from pipi -> K
anti-K. In addition, we have improved the fit to the f2(1270) resonance and
used a more flexible P wave parametrization above the K anti-K threshold and
included an estimation of the D2 wave inelasticity. The better accuracy thus
achieved also required a refinement of the Regge analysis above 1.42 GeV. We
have checked that the pipi scattering amplitudes obtained in this approach
satisfy remarkably well forward dispersion relations and Roy's equations.Comment: 6 pages, invited talk to the IV International Conference on Quarks
and Nuclear Physics QNP06, Madrid 5th-10th June 200
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
Hadronic Contributions to the Photon Vacuum Polarization and their Role in Precision Physics
I review recent evaluations of the hadronic contribution to the shift in the
fine structure constant and to the anomalous magnetic moment of the muon.
Substantial progress in a precise determination of these important observables
is a consequence of substantially improved total cross section measurement by
the CMD-2 and BES II collaborations and an improved theoretical understanding.
Prospects for further possible progress is discussed.Comment: 17 pages 7 figures 2 tables, update: incl. CMD-2 data, reference
Signatures of HyperCharge Axions in Colliders
If in addition to the standard model fields, a new pseudoscalar field that
couples to hypercharge topological number density, the hypercharge axion,
exists, it can be produced in colliders in association with photons or Z
bosons, and detected by looking for its decay into photons or Z's. For a range
of masses below a TeV and coupling above a fraction of 1/TeV, existing data
from LEP II and the Tevatron can already put interesting constraints, and in
future colliders accessible detection range is increased significantly. The
hypercharge axion can help in explaining the matter-antimatter asymmetry in the
universe.Comment: 11 pages, 8 figures, uses axodraw.st
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