142 research outputs found
The Lorentz and CPT violating effects on the Z\to l^+ l^- decay
We study the Lorentz and CPT violating effects on the branching ratio BR, the
CPT violating asymmetry A_{CPT} and the ratio of the decay width, including
only the Lorentz violating effects, to the one obtained in the standard model,
for the flavor dependent part of the lepton flavor conserving Z\to l^+ l^-
(l=e,\mu,\tau) decay. The inclusion of the Lorentz and CPT violating effects to
the standard model contribution is too small to be detected, since the
corresponding coefficients are highly suppressed at the low energy scale.Comment: 11 pages, 6 figure
Nucleon form factors, B-meson factories and the radiative return
The feasibility of a measurement of the electric and magnetic nucleon form
factors at -meson factories through the radiative return is studied. Angular
distributions allow a separation of the contributions from the two form
factors. The distributions are presented for the laboratory and the hadronic
rest frame, and the advantages of different coordinate systems are
investigated. It is demonstrated that values up to 8 or even 9 GeV
are within reach. The Monte Carlo event generator PHOKHARA is extended to
nucleon final states, and results are presented which include Next-to-Leading
Order radiative corrections from initial-state radiation. The impact of angular
cuts on rates and distributions is investigated and the relative importance of
radiative corrections is analysed.Comment: 9 pages, 11 figures. Final version to appear in Eur. Phys. J.
Time domain deBroglie wave interferometry along a magnetic guide
Time domain deBroglie wave interferometry [Cahn et al, Phys. Rev. Lett. 79,
784] is applied to Rb87 atoms in a magnetic guide. A standing wave light field
is carefully aligned along the guiding direction of the magnetic trapping
potential from a soft-ferromagnetic 4-foil structure. A sequence of two
standing wave pulses is applied to the magnetically trapped atoms. The
backscattered light at the atomic density grating revival time is collected and
detected via a heterodyning technique. In addition to the observed recoil
oscillations that fit the interferometer theory for atoms in free space, we
observe a decay of the interferometer contrast on a millisecond time scale with
unexpected millisecond-scale oscillations. We find that the oscillating decay
is explained by a residual variation of the linear trapping potential along the
standing wave direction.Comment: 22 pages, 7 figure
Triangulations and Severi varieties
We consider the problem of constructing triangulations of projective planes
over Hurwitz algebras with minimal numbers of vertices. We observe that the
numbers of faces of each dimension must be equal to the dimensions of certain
representations of the automorphism groups of the corresponding Severi
varieties. We construct a complex involving these representations, which should
be considered as a geometric version of the (putative) triangulations
Effects of ash removal by agitated aqueous washing and sedimentation on the physico-chemical characteristics and fast pyrolysis of trommel fines
A pre-treated trommel fines feedstock (DPT) with 35.1 wt% ash content and particle size range of 0.5–2 mm was processed through two (100% distilled water and 1% surfactant in distilled water) aqueous agitated washing and sedimentation procedures for ash reduction prior to fast pyrolysis in a bubbling fluidized bed reactor. The washing process led to more than 36% reduction in the ash/inorganic contents of the DPT feedstock and yielded about 78 wt% of organic-rich feedstocks denoted as WPT1 and WPT2. Characterisation and fast pyrolysis of all three feedstocks was carried out to evaluate the effect of the washing process on their physico-chemical characteristics and yields of fast pyrolysis products. Results showed that the ash reduction led to increase in the volatile matter contents of the washed feedstocks by 20%, while reducing nitrogen contents. In addition, fast pyrolysis of the feedstocks showed improved yield of liquid and gas products, with a dramatic reduction of reaction water, indicating that the ash removal reduced the catalytic effect of the ash on water formation during the fast pyrolysis process. The major organic compounds in the liquid products included phenols and furans from biogenic fraction of the feedstock as well as aromatic hydrocarbons such as those obtained from pyrolysis of plastics. More importantly, the overall energy yields from the fast pyrolysis process increased by over 35% after washing the feedstock, with washing with only distilled water alone giving the highest energy yield of 93%. Hence, coupling the water-washing ash reduction process with fast pyrolysis appeared to be a suitable technology for valorising feedstocks with high ash contents such as trommel fines for energy and chemicals
Elliptic flow of charged particles in Pb-Pb collisions at 2.76 TeV
We report the first measurement of charged particle elliptic flow in Pb-Pb
collisions at 2.76 TeV with the ALICE detector at the CERN Large Hadron
Collider. The measurement is performed in the central pseudorapidity region
(||<0.8) and transverse momentum range 0.2< < 5.0 GeV/. The
elliptic flow signal v, measured using the 4-particle correlation method,
averaged over transverse momentum and pseudorapidity is 0.087 0.002
(stat) 0.004 (syst) in the 40-50% centrality class. The differential
elliptic flow v reaches a maximum of 0.2 near = 3
GeV/. Compared to RHIC Au-Au collisions at 200 GeV, the elliptic flow
increases by about 30%. Some hydrodynamic model predictions which include
viscous corrections are in agreement with the observed increase.Comment: 10 pages, 4 captioned figures, published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/389
Observation of the TeV gamma-ray source MGRO J1908+06 with ARGO-YBJ
The extended gamma ray source MGRO J1908+06, discovered by the Milagro air
shower detector in 2007, has been observed for about 4 years by the ARGO-YBJ
experiment at TeV energies, with a statistical significance of 6.2 standard
deviations. The peak of the signal is found at a position consistent with the
pulsar PSR J1907+0602. Parametrizing the source shape with a two-dimensional
Gauss function we estimate an extension \sigma = 0.49 \pm 0.22 degrees,
consistent with a previous measurement by the Cherenkov Array H.E.S.S.. The
observed energy spectrum is dN/dE = 6.1 \pm 1.4 \times 10^-13 (E/4 TeV)^{-2.54
\pm 0.36} photons cm^-2 s^-1 TeV^-1, in the energy range 1-20 TeV. The measured
gamma ray flux is consistent with the results of the Milagro detector, but is
2-3 times larger than the flux previously derived by H.E.S.S. at energies of a
few TeV. The continuity of the Milagro and ARGO-YBJ observations and the stable
excess rate observed by ARGO-YBJ along 4 years of data taking support the
identification of MGRO J1908+06 as the steady powerful TeV pulsar wind nebula
of PSR J1907+0602, with an integrated luminosity above 1 TeV about 1.8 times
the Crab Nebula luminosity.Comment: 6 pages, accepted for pubblication by ApJ. Replaced to correct the
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