872 research outputs found
Comparison of Different Methods to Calculate Induced Voltage in Longitudinal Beam Dynamics Codes
No full textCollective effects in longitudinal beam dynamics simulations are essential for many studies since they can perturb the RF potential, giving rise to instabilities. The beam induced voltage can be computed in frequency or time domain using a slicing of the beam profile. This technique is adopted by many codes including CERN BLonD. The slicing acts as a frequency filter and cuts high frequency noise but also physical contributions if the resolution is not sufficient. Moreover, a linear interpolation usually defines the voltage for all the macro-particles, and this can be another source of unphysical effects. The MuSiC code describes interaction between the macro-particles with the wakes generated only by resonator impedances. The complications related to the slices are avoided, but the voltage can contain high frequency noise. In addition, since the computational time scales with the number of resonators and macro-particles, having a large number of them can be cumbersome. In this paper the features of the different approaches are described together with benchmarks between them and analytical formulas, considering both single and multi-turn wakes
Observation of Isolated High-E
No full textEvents containing an isolated prompt photon with high transverse energy, together with a balancing jet, have been observed for the first time in photoproduction at HERA. The data were taken with the ZEUS detector, in a flp centre of mass energy range 120--250 GeV. The fraction of the incoming photon energy participating in the production of the prompt photon and the jet, x fl , shows a strong peak near unity, consistent with LO QCD Monte Carlo predictions. In the transverse energy and pseudorapidity range 5 E fl T ! 10 GeV, \Gamma0:7 j fl ! 0:8, E jet T 5 GeV, and \Gamma1:5 j jet 1:8, with x OBS fl ? 0:8; the measured cross section is 15.3\Sigma3.8\Sigma1.8 pb, in good agreement with a recent NLO calculation. The ZEUS Collaboration J. Breitweg, M. Derrick, D. Krakauer, S. Magill, D. Mikunas, B. Musgrave, J. Repond, R. Stanek, R.L. Talaga, R. Yoshida, H. Zhang Argonne National Laboratory, Argonne, IL, USA p M.C.K. Mattingly Andrews University, Berrien Springs, MI, U..
Response of the CALICE Si-W electromagnetic calorimeter physics prototype to electrons
No full textA prototype silicon–tungsten electromagnetic calorimeter(ECAL)for an international linear collider (ILC) detector was installed and tested during summer and autumn 2006 at CERN. The detector had 6480 silicon pads of dimension 1 1cm2. Data were collected with electron beams in the energy range 6–45 GeV.The analysis described in this paper focuses on electromagnetic shower reconstruction and characterises the ECAL response to electrons in terms of energy resolution and linearity. The detector is linear to within approximately the 1%level and has a relative energy resolution of (16.53+-0.14(stat)+-0.4(syst))/ Wurzel aus E(GeV) + (1.07+-0.07(stat)+-0.1(syst)) (%).The spatial uniformity and the time stability of the ECAL are also addresse
W production and the search for events with an isolated high-energy lepton and missing transverse momentum at HERA
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Linking supply to demand : the neuronal monocarboxylate transporter MCT2 and the alpha-amino-3-hydroxyl-5-methyl-4-isoxazole-propionic acid receptor GluR2/3 subunit are associated in a common trafficking process
No full textMCT2 is the major neuronal monocarboxylate transporter (MCT) that allows the supply of alternative energy substrates such as lactate to neurons. Recent evidence obtained by electron microscopy has demonstrated that MCT2, like alpha-amino-3-hydroxyl-5-methyl-4-isoxazole-propionic acid (AMPA) receptors, is localized in dendritic spines of glutamatergic synapses. Using immunofluorescence, we show in this study that MCT2 colocalizes extensively with GluR2/3 subunits of AMPA receptors in neurons from various mouse brain regions as well as in cultured neurons. It also colocalizes with GluR2/3-interacting proteins, such as C-kinase-interacting protein 1, glutamate receptor-interacting protein 1 and clathrin adaptor protein. Coimmunoprecipitation of MCT2 with GluR2/3 and C-kinase-interacting protein 1 suggests their close interaction within spines. Parallel changes in the localization of both MCT2 and GluR2/3 subunits at and beneath the plasma membrane upon various stimulation paradigms were unraveled using an original immunocytochemical and transfection approach combined with three-dimensional image reconstruction. Cell culture incubation with AMPA or insulin triggered a marked intracellular accumulation of both MCT2 and GluR2/3, whereas both tumor necrosis factor alpha and glycine (with glutamate) increased their cell surface immunolabeling. Similar results were obtained using Western blots performed on membrane or cytoplasm-enriched cell fractions. Finally, an enhanced lactate flux into neurons was demonstrated after MCT2 translocation on the cell surface. These observations provide unequivocal evidence that MCT2 is linked to AMPA receptor GluR2/3 subunits and undergoes a similar translocation process in neurons upon activation. MCT2 emerges as a novel component of the synaptic machinery putatively linking neuroenergetics to synaptic transmissio
Exclusive electroproduction of rho0 and J / psi mesons at HERA
No full textExclusive production of rho(0) and J/psi mesons in e(+)p collisions has been studied with the ZEUS detector in the kinematic range 0.25 < Q(2) < 50 GeV2, 20 < W < 167 GeV for the rho(0) data and 2 < Q(2) < 40 GeV2, 50 < IS' < 150 GeV for the J/psi data. Cross sections for exclusive rho(0) and J/psi, production have been measured as a function of Q2, W and t. The spin-density matrix elements r(00)(04), r(1-1)(1) and Rer(10)(5) have been determined for exclusive rho(0) production as well as r(00)(04) and r(1-1)(04) for exclusive J/psi production. The results are discussed in the context of theoretical models invoking soft and hard phenomena
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