3,573 research outputs found
Laboratory Bounds on Electron Lorentz Violation
Violations of Lorentz boost symmetry in the electron and photon sectors can
be constrained by studying several different high-energy phenomenon. Although
they may not lead to the strongest bounds numerically, measurements made in
terrestrial laboratories produce the most reliable results. Laboratory bounds
can be based on observations of synchrotron radiation, as well as the observed
absences of vacuum Cerenkov radiation. Using measurements of synchrotron energy
losses at LEP and the survival of TeV photons, we place new bounds on the three
electron Lorentz violation coefficients c_(TJ), at the 3 x 10^(-13) to 6 x
10^(-15) levels.Comment: 18 page
Measurements of heavy ion beam losses from collimation
The collimation efficiency for Pb ion beams in the LHC is predicted to be
lower than requirements. Nuclear fragmentation and electromagnetic dissociation
in the primary collimators create fragments with a wide range of Z/A ratios,
which are not intercepted by the secondary collimators but lost where the
dispersion has grown sufficiently large. In this article we present
measurements and simulations of loss patterns generated by a prototype LHC
collimator in the CERN SPS. Measurements were performed at two different
energies and angles of the collimator. We also compare with proton loss maps
and find a qualitative difference between Pb ions and protons, with the maximum
loss rate observed at different places in the ring. This behavior was predicted
by simulations and provides a valuable benchmark of our understanding of ion
beam losses caused by collimation.Comment: 12 pages, 20 figure
El Dios del rico y el Dios del pobre : (cuadros desde ángulos distintos sobre cosas que más que a medias se saben pero que a la palabra nos saltan solo a medias) cuasi-poemas
Erinnern um dazuzugehören. Kulturelles Gedächtnis, Zugehörigkeitsstruktur und normative Vergangenheit
Produção de gado de corte e acúmulo de matéria seca em sistemas de integração lavoura: pecuária em presença e ausência de trevo branco e nitrogênio.
O trabalho foi conduzido com o objetivo de verificar a influência da adubação nitrogenada em uma pastagem de azevém (Lolium multiflorium L.) e aveia (Avena strigosa Scherb) em presença e ausência de trevo branco (Trifolium repens L.), conferida pelo acúmulo e produção de matéria seca, ganho médio diário, ganho de peso vivo e carga animal no sistema de integração lavoura-pecuária sob sistema de plantio direto. A cultura antecessora da pastagem foi a soja (Glycine Max L.). O delineamento experimental foi em blocos completos ao acaso, com parcelas subdivididas e três repetições. Nas parcelas, foram testadas quatro doses de nitrogênio (0, 100, 200 e 300 kg.ha-1) e nas subparcelas, a combinação de presença e ausência de trevo branco. A elevação das doses crescentes de N aumentaram de forma linear crescente o acúmulo e a produção de matéria seca da pastagem. A carga animal e o ganho de peso vivo por hectare de bovinos aumentaram com o incremento de nitrogênio. Os resultados demonstram o efeito da adubação nitrogenada no acúmulo diário, na produção de matéria seca, carga animal e no ganho de peso vivo
Development of hollow electron beams for proton and ion collimation
Magnetically confined hollow electron beams for controlled halo removal in
high-energy colliders such as the Tevatron or the LHC may extend traditional
collimation systems beyond the intensity limits imposed by tolerable material
damage. They may also improve collimation performance by suppressing loss
spikes due to beam jitter and by increasing capture efficiency. A hollow
electron gun was designed and built. Its performance and stability were
measured at the Fermilab test stand. The gun will be installed in one of the
existing Tevatron electron lenses for preliminary tests of the hollow-beam
collimator concept, addressing critical issues such as alignment and
instabilities of the overlapping proton and electron beams.Comment: 3 pp. 1st International Particle Accelerator Conference: IPAC'10,
23-28 May 2010: Kyoto, Japa
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