422 research outputs found
CP violation and electric-dipole-moment at low energy production with polarized electrons
The new proposals for high luminosity B/Flavor factories, near and on top of
the resonances, allow for a detailed investigation of CP-violation
in the -pair production. In particular, bounds on the tau electric dipole
moment can be obtained from genuine CP-odd observables related to the
-pair production. We perform an independent analysis from low energy (10
GeV) data by means of linear spin observables. We show that, for a
longitudinally polarized electron beam, a CP-odd asymmetry, associated to the
normal polarization term, can be measured at these low energy facilities both
at resonant and non resonant energies. In this way, stringent and independent
bounds to the tau electric dipole moment, which are orders of magnitude below
other high or low energy bounds, can be obtained.Comment: 12 pages, 2 figure
CP violation and electric-dipole-moment at low energy tau-pair production
CP violation at low energy is investigated at the tau electromagnetic vertex.
High statistics at B factories, and on top of the Upsilon resonances, allows a
detailed investigation of CP-odd observables related to the tau-pair
production. The contribution of the tau electric dipole moment is considered in
detail. We perform an analysis independent from the high energy data by means
of correlation and linear spin observables at low energy. We show that
different CP-odd asymmetries, associated to the normal-transverse and
normal-longitudinal correlation terms can be measured at low energy
accelerators, both at resonant and non resonant energies. These observables
allow to put stringent and independent bounds to the tau electric dipole moment
that are competitive with other high or low energy results.Comment: 18 pages, 2 figures, references added, minor changes in section 3 and
5, to be published in Nucl.Phys.
Der Einfluss symbiotischer Bodenpilze auf den Stickstoffzyklus
To increase nutrient use efficiency and reduce nutrient losses are key aspects for sustainable agriculture. Arbuscular mycorrhizal fungi (AMF) are an import and widespread group of plant-symbiotic soil fungi. Here we investigate the role of those soil microorganisms, for effective nutrient recycling. We conducted greenhouse and lysimeter experiments to compare the cycling of important plant nutrients in systems with high and low abundance of AMF. AMF increased plant N nutrition, reduced leaching losses of mineral N, and prevented emissions of N2O, an important greenhouse gas. The results show the importance of AMF for an effective nutrient management. Farmers should implement strategies to promote AMF in the soil, as they are an indispensable compound of sustainable agriculture
The Effect of Shadowing on Initial Conditions, Transverse Energy and Hard Probes in Ultrarelativistic Heavy Ion Collisions
The effect of shadowing on the early state of ultrarelativistic heavy ion
collisions is investigated along with transverse energy and hard process
production, specifically Drell-Yan, , and production. We
choose several parton distributions and parameterizations of nuclear shadowing,
as well as the spatial dependence of shadowing, to study the influence of
shadowing on relevant observables. Results are presented for Au+Au collisions
at GeV and Pb+Pb collisions at TeV.Comment: Submitted to Phys. Rev.
Cosmological Dynamics of Phantom Field
We study the general features of the dynamics of the phantom field in the
cosmological context. In the case of inverse coshyperbolic potential, we
demonstrate that the phantom field can successfully drive the observed current
accelerated expansion of the universe with the equation of state parameter
. The de-Sitter universe turns out to be the late time attractor
of the model. The main features of the dynamics are independent of the initial
conditions and the parameters of the model. The model fits the supernova data
very well, allowing for at 95 % confidence level.Comment: Typos corrected. Some clarifications and references added. To appear
in Physical Review
A Phenomenological Analysis of Gluon Mass Effects in Inclusive Radiative Decays of the and $\Upsilon
The shapes of the inclusive photon spectra in the processes \Jp \to \gamma
X and \Up \to \gamma X have been analysed using all available experimental
data.
Relativistic, higher order QCD and gluon mass corrections were taken into
account in the fitted functions. Only on including the gluon mass corrections,
were consistent and acceptable fits obtained. Values of
GeV and GeV were found for the
effective gluon masses (corresponding to Born level diagrams) for the \Jp and
\Up respectively. The width ratios \Gamma(V \to {\rm hadrons})/\Gamma(V \to
\gamma+ {\rm hadrons}) V=\Jp, \Up were used to determine and . Values consistent with the current world
average were obtained only when gluon mass correction factors,
calculated using the fitted values of the effective gluon mass, were applied. A
gluon mass GeV, as suggested with these results, is consistent with
previous analytical theoretical calculations and independent phenomenological
estimates, as well as with a recent, more accurate, lattice calculation of the
gluon propagator in the infra-red region.Comment: 50 pages, 11 figures, 15 table
Parametrization of nonlinear and chaotic oscillations in driven beam-plasma diodes
Nonlinear phenomena in a driven plasma diode are studied using a fluid code and the particle-in-cell simulation code XPDPI. When a uniform electron beam is injected to a bounded diode filled with uniform ion background, the beam is destabilized by the Pierce instability and a perturbation grows to exhibit nonlinear oscillations including chaos. Two standard routes to chaos, period doubling and quasiperiodicity, are observed. Mode lockings of various winding numbers are observed in an ac driven system. A new diagnostic quantity is used to parametrize various nonlinear oscillations.open10
A measurement of the tau mass and the first CPT test with tau leptons
We measure the mass of the tau lepton to be 1775.1+-1.6(stat)+-1.0(syst.) MeV
using tau pairs from Z0 decays. To test CPT invariance we compare the masses of
the positively and negatively charged tau leptons. The relative mass difference
is found to be smaller than 3.0 10^-3 at the 90% confidence level.Comment: 10 pages, 4 figures, Submitted to Phys. Letts.
Measurement of the ratio of branching fractions BR(B0 -> K*0 gamma)/BR(Bs0 -> phi gamma) and the direct CP asymmetry in B0 -> K*0 gamma
The ratio of branching fractions of the radiative B decays B0 -> K*0 gamma
and Bs0 phi gamma has been measured using an integrated luminosity of 1.0 fb-1
of pp collision data collected by the LHCb experiment at a centre-of-mass
energy of sqrt(s)=7 TeV. The value obtained is BR(B0 -> K*0 gamma)/BR(Bs0 ->
phi gamma) = 1.23 +/- 0.06(stat.) +/- 0.04(syst.) +/- 0.10(fs/fd), where the
first uncertainty is statistical, the second is the experimental systematic
uncertainty and the third is associated with the ratio of fragmentation
fractions fs/fd. Using the world average value for BR(B0 -> K*0 gamma), the
branching fraction BR(Bs0 -> phi gamma) is measured to be (3.5 +/- 0.4) x
10^{-5}.
The direct CP asymmetry in B0 -> K*0 gamma decays has also been measured with
the same data and found to be A(CP)(B0 -> K*0 gamma) = (0.8 +/- 1.7(stat.) +/-
0.9(syst.))%.
Both measurements are the most precise to date and are in agreement with the
previous experimental results and theoretical expectations.Comment: 21 pages, 3 figues, 4 table
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