1,792 research outputs found
Is the anomalous decay ratio of D_{sJ}(2632) due to isospin breaking?
Quark pair annihilation into gluons is suppressed at large momenta due to the
asymptotic freedom. As a consequence, mass eigenvalues of heavy states should
be almost diagonal with respect to up and down quark masses, thereby breaking
isospin. We suggest the particle observed by the SELEX Collaboration,
D_{sJ}(2632) to be to a good extent a [cd][dbar sbar] state, which would
explain why its D^0 K^+ mode is anomalously suppressed with respect to D_s eta.
Predictions for the rates of the yet unobserved modes D_s pi^0 and D^+ K^0 are
given.Comment: 3 pages, 1 figur
Four-Quark Mesons in Non-leptonic B Decays--Could They Resolve Some Old Puzzles?
We point out that non-leptonic B decays driven by b-->ccbar s should provide
a favourable environment for the production of hidden charm diquark-antidiquark
bound states that have been suggested to explain the resonances with masses
around 4 GeV recently observed by BaBar and BELLE. Studying their relative
abundances in non-leptonic B decays can teach us novel lessons about their
structure and the strong interactions. Through their decay into psi they can
provide a natural explanation of the excess of B-->psi X observed for p_psi < 1
GeV. Other phenomenological consequences are mentioned as well.Comment: 6 pages, 2 figures, revte
Seismic Noise by Wind Farms: A Case Study from the Virgo Gravitational Wave Observatory, Italy
We present analyses of the noise wave field in the vicinity of Virgo, the Italian–French gravitational wave observatory located close to Pisa, Italy, with special reference to the vibrations induced by a nearby wind farm. The spectral contribution of the wind turbines is investigated using (1) onsite measurements, (2) correlation of spectral amplitudes with wind speed, (3) directional properties determined via multichannel measurements, and (4) attenuation of signal amplitude with distance. Among the different spectral peaks thus discriminated, the one at frequency 1.7 Hz is associated with the greatest power, and under particular conditions it can be observed at distances as large as 11 km from the wind farm. The spatial decay of amplitudes exhibits a complicated pattern, which we interpret in terms of the combination of direct surface waves and body waves refracted at a deep (≈800 m) interface between the Plio-Pleistocenic marine, fluvial, and lacustrine sediments and the Miocene carbonate basement. We develop a model for wave attenuation that allows determining the amplitude of the radiation from individual turbines, which is estimated on the order of 300–400 μms_1/ √Hz for wind speeds over the 8–14 m=s range. On the basis of this model, we then develop a predictive relationship for assessing the possible impact of future wind farm projects
Geração de coordenadas UTM usando azimutes e distâncias para delimitação da área da unidade da Embrapa em Sinop, Mato Grosso.
O objetivo desse trabalho é delimitar a área da fazenda onde será construÃda a nova unidade e gerar um mapa da cobertura vegetal da área e seu entorno.Poster. Trabalho apresentado na V Mostra de Trabalhos de Estagiários e Bolsistas, Campinas, out. 2009
Seismic Noise by Wind Farms: A Case Study from the VIRGO Gravitational Wave Observatory, Italy.
We present analyses of the noise wavefield in the vicinity of VIRGO, the Italy-France gravitational wave observatory located close to Pisa, Italy, with special reference to the vibrations induced by a nearby wind park. The spectral contribution of the wind turbines is investigated using (i) on-site measurements, (ii) correlation of spectral amplitudes with wind speed, (iii) directional properties determined via multichannel measurements, and (iv) attenuation of signal amplitude with distance. Among the different spectral peaks thus discriminated, the one at frequency 1.7 Hz has associated the greatest power, and under particular conditions it can be observed at distances as large as 11 km from the wind park. The spatial decay of amplitudes exhibits a complicate pattern, that we interpret in terms of the combination of direct surface waves and body waves refracted at a deep (_ 800 m) interface between the plio-pleistocenic marine, fluvial and lacustrine sediments and the Miocene carbonate basement. We develop a model for wave attenuation which allows determining the amplitude of the radiation from individual turbines, which is estimated on the order of 300-400 μms−119 /pHz for wind speeds over the 8-14 m/s range. On the base of this model, we then develop a predictive relationship for assessing the possible impact of future, project wind farms
Diquark-Antidiquarks with Hidden or Open Charm and the Nature of X(3872)
Heavy-light diquarks can be the building blocks of a rich spectrum of states
which can accommodate some of the newly observed charmonium-like resonances not
fitting a pure c-cbar assignment. We examine this possibility for hidden and
open charm diquark-antidiquark states deducing spectra from constituent quark
masses and spin-spin interactions. Taking the X(3872) as input we predict the
existence of a 2++ state that can be associated to the X(3940) observed by
Belle and re-examine the state claimed by SELEX, X(2632). The possible
assignment of the previously discovered states D_s(2317) and D_s(2457) is
discussed. We predict X(3872) to be made of two components with a mass
difference related to (m_u-m_d) and discuss the production of X(3872) and of
its charged partner X^(+-) in the weak decays of B^(+,0).Comment: 11 pages, 2 figures, revtex, minor typos correcte
Caratteristiche del Rumore Sismico nei pressi del Rilevatore di Onde Gravitazionali VIRGO (Cascina, Pisa)
In questo lavoro si presentano i risultati di uno studio sulle caratteristiche del rumore sismico in prossimità del rilevatore di onde gravitazionali VIRGO (Cascina, Pisa), con particolare riferimento alle vibrazioni associate all’azione di un vicino parco eolico. La valutazione delle componenti spettrali del rumore verosimilmente indotte dagli aerogeneratori è stata effettuata mediante (i) Misure dirette alla base di una turbina, (ii) Correlazione fra le ampiezze spettrali del rumore e la velocità del vento; (iii) Determinazione delle proprietà direzionali da misure multicanale, (iv) Misura dell’attenuazione del segnale con la distanza dal parco eolico. Il disturbo provocato dagli aerogeneratori è particolarmente energetico alla frequenza di 1.7 Hz e, in particolari condizioni, è stato osservato fino a distanze di 11 km dal Parco Eolico. Il decadimento spaziale delle ampiezze ha un andamento complesso, che può essere interpretato in termini di una combinazione fra onde superficiali e onde di volume rifratte ad un’interfaccia profonda (~800 m) fra i sedimenti plio-pleistocenici ed i calcari Miocenici. La risposta locale nei dintorni dell’interferometro è stata investigata utilizzando la tecnica dei rapporti spettrali H/V. Si sono così evidenziate due bande di amplificazione imputabili ad effetti di risonanza legati alla geologia a scala locale: il primo intorno alla frequenza di 0.35 Hz, il secondo fra 0.7 e 2.0 Hz. Entrambi i picchi risultano essere essenzialmente omogenei in tutta l’area di studio, a conferma della sostanziale uniformità della struttura geologica
Positive Parity Scalar Mesons in the 1-2 GeV Mass Range
Based on the observation that K_0(1430) is lighter than its SU_3 counterpart,
a_0(1450), we examine the possibility that these particles, together with
f_0(1370), f_0(1500) and f_0(1710), fill a tetraquark recurrence of the sub-GeV
0^{++} nonet mixed with a glueball state. We find the picture to be consistent
with the known data about the three f_0 resonances, more than the q-qbar
hypothesis. Conventional spin-orbit coupling suggests the q-qbar, P-wave, nonet
to lie around 1200 MeV. We review possible experimental indications of a scalar
isovector resonance at 1.29 GeV, first observed by OBELIX in p-pbar
annihilation.Comment: 12 pages, 9 figures. Extended version. References added. Results and
conclusions unchange
Charmless Three-Body Baryonic B Decays
Motivated by recent data on B-> p pbar K decay, we study various charmless
three-body baryonic B decay modes, including Lambda pbar pi, Sigma0 pbar pi, p
pbar pi, p pbar Kbar0, in a factorization approach. These modes have rates of
order 10^{-6}. There are two mechanisms for the baryon pair production,
current-produced and transition. The behavior of decay spectra from these
baryon production mechanisms can be understood by using QCD counting rules.
Predictions on rates and decay spectra can be checked in the near future.Comment: 26 pages, 9 figures; version to appear in Phys. Rev.
Two-Fermion Production in Electron-Positron Collisions
This report summarizes the results of the two-fermion working group of the
LEP2-MC workshop, held at CERN from 1999 to 2000. Recent developments in the
theoretical calculations of the two fermion production process in the
electron-positron collision at LEP2 center of the mass energies are reported.
The Bhabha process and the production of muon, tau, neutrino and quark pairs is
covered. On the basis of comparison of various calculations, theoretical
uncertainties are estimated and compared with those needed for the final LEP2
data analysis. The subjects for the further studies are identified.Comment: 2-fermion working group report of the LEP2 Monte Carlo Workshop
1999/2000, 113 pages, 24 figures, 35 table
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