119676532
Development of a cylindrical scintillating fiber tracker for experiment E835 at FNAL
Abstract A tracking detector made of scintillating fibers wound on a cylinder is being developed at FNAL, for the experiment E835 (study of the spectroscopy of charmonium formed in p p annihilations, at the Fermilab Antiproton Accumulator). The tracker will be used for the measurement of the polar angle, i.e. of the longitudinal coordinate. The small amount of light from the fibers will be detected by solid state devices (Visible Light Photon Counters) with very high QE, currently being developed and tested by the D0 Fiber Tracking Group at FNAL. This paper reports the performance of a prototype fiber tracker, as measured at FNAL. We present results on light yield/mip, attenuation, efficiency, homogeneity of response and cross-talk. The data are then compared with Monte Carlo predictions. We measured an average number of 14 photoelectrons per mip and a very low noise level. An efficiency greater than 99% is foreseen for the future double layered tracker.
125331327
The Fermilab anti-p accumulator ring for the charmonium experiment
123064237
The charged trigger of the experiment E835 at Fermilab
Abstract Fermilab experiment E835 studies the charmonium states primarily through their electromagnetic decays. A kinematical charged trigger has been designed to select the electromagnetic final states e + e − and e + e − X and the hadronic decay c c → φφ →4 K ± . A detailed description of the charged trigger is presented here. The design, its implementation and the performances are given.
108986863
Performance measurements of histe-V VLPC photon detectors for E835 at FNAL
A set of 144 VLPC chips has been used by experiment E835 at FNAL for the readout of its scintillating fiber detector. During the data taking, the fibers have been exposed to rates up to 2.5×104 mips/sec, corresponding to 3.5×106 photons/sec on each VLPC pixel surface. This paper reports about a study on rate dependence of gain and quantum efficiency throughout the run, as well as VLPC failure statistics during operation. No significant aging effects are observed. A review about the overall system performance is given.
119627299
HIGH-RESOLUTION SILICON DETECTORS FOR COLLIDING BEAM PHYSICS
Abstract Resolution and linearity of the position measurement of Pisa multi-electrode silicon detectors are presented. The detectors are operated in slightly underdepleted mode and take advantage of their intrinsic resistivity for resistive charge partition between adjacent strips. 22 μm resolution is achieved with readout lines spaced 300 μm. Possible applications in colliding beam experiments for the detection of secondary vertices are discussed.
119936495
Hadronic Physics with Antiprotons at FAIR
The physics program of the future FAIR facility covers a wide range of topics that address central issues of strong interactions and QCD. The antiproton beam of unprecedented quality in the momentum range from 1 GeV/c to 15 GeV/c will allow to make high precision, high statistics measurements, from charmonium spectroscopy to the search for exotic hadrons and the study of nucleon structure, from the study of in-medium modifications of hadron masses to the physics of hypernuclei. These topics form the scientific program of the PANDA experiment. In addition to that the possibility to polarize antiprotons will provide the possibility to perform new, unique measurements of single- and double-spin observables, which are part of the experimental program of PAX.
11244261
Rotation curves and metallicity gradients from HII regions in spiral galaxies
In this paper we study long slit spectra in the region of H emission line of a sample of 111 spiral galaxies with recognizable and well defined spiral morphology and with a well determined environmental status, ranging from isolation to non-disruptive interaction with satellites or companions. The form and properties of the rotation curves are considered as a function of the isolation degree, morphological type and luminosity. The line ratios are used to estimate the metallicity of all the detected HII regions, thus producing a composite metallicity profile for dierent types of spirals. We have found that isolated galaxies tend to be of later types and lower luminosity than the interacting galaxies. The outer parts of the rotation curves of isolated galaxies tend to be flatter than in interacting galaxies, but they show similar relations between global parameters. The scatter of the Tully-Fisher relation defined by isolated galaxies is significantly lower than that of interacting galaxies. The (NII)/H ratios, used as a metallicity indicator, show a clear trend between Z and morphological type, t, with earlier spirals showing higher ratios; this trend is tighter when instead of t the gradient of the inner rotation curve, G, is used; no trend is found with the change in interaction status. The Z-gradient of the disks depends on the type, being almost flat for early spirals, and increasing for later types. The (NII)/H ratios measured for disk HII regions of interacting galaxies are higher than for normal/isolated objects, even if all the galaxy families present similar distributions of H Equivalent Width.
118188413
Disformal invariance of second order scalar-tensor theories: Framing the Horndeski action
The Horndeski action is the most general one involving a metric and a scalar field that leads to second order field equations in four dimensions. Being the natural extension of the well known Scalar-Tensor theories, its structure and properties are worth analysing along the experience accumulated in the latter context. Here we argue that disformal transformations play, for the Horndeski theory, a similar role to that of conformal transformations for Scalar-Tensor theories a l`a Brans-Dicke. We identify the most general transformation preserving second order field equations and discuss the issue of viable frames for this kind of theories, in particular the possibility to cast the action in the so called Einstein frame. Finally, we investigate the physical equivalence of such frames and their reciprocal relationship.
73623447
WINGS-SPE Spectroscopy in the WIde-field Nearby Galaxy-cluster Survey
Aims. We present the results from a comprehensive spectroscopic survey of the WINGS (Wide-field Nearby Galaxy-cluster Survey) clusters, a program called WINGS-SPE. The WINGS-SPE sample consists of 48 clusters, 22 of which are in the southern sky and 26 in the north. The main goals of this spectroscopic survey are: (1) to study the dynamics and kinematics of the WINGS clusters and their constituent galaxies, (2) to explore the link between the spectral properties and the morphological evolution in different density environments and across a wide range of cluster X-ray luminosities and optical properties. Methods. Using multi-object fiber-fed spectrographs, we observed our sample of WINGS cluster galaxies at an intermediate resolution of 6-9 A and, using a cross-correlation technique, we measured redshifts with a mean accuracy of ∼45 km s -1 . Results. We present redshift measurements for 6137 galaxies and their first analyses. Details of the spectroscopic observations are reported. The WINGS-SPE has ∼30% overlap with previously published data sets, allowing us both to perform a complete comparison with the literature and to extend the catalogs. Conclusions. Using our redshifts, we calculate the velocity dispersion for all the clusters in the WINGS-SPE sample. We almost triple the number of member galaxies known in each cluster with respect to previous works. We also investigate the X-ray luminosity vs. velocity dispersion relation for our WINGS-SPE clusters, and find it to be consistent with the form L x ∝ σ 4 v .
118464591
A new photometric investigation of the double-ringed galaxy ESO 474—G26: unveiling the formation scenario
We present a detailed photometric study of the peculiar double-ringed galaxy ESO 474−G26. Near-infrared (NIR) and optical data have been used, with the main goal of constraining the formation history of ESO 474−G26. NIR photometry is fundamental in this kind of study, because it gives better constraints on the spectral energy distribution (SED) and traces the older stellar population of the galaxy well. This galaxy presents a very complex structure with two almost orthogonal rings, one in the equatorial and another in the polar plane, around an elliptical-like object. Due to the peculiar morphology of ESO 474−G26, we used both NIR images (J and K bands) to derive accurate analysis of the stellar light distribution and optical images (in the B, V and R bands) to derive colour profiles and colour maps to study the structure of the rings. The observational characteristics of ESO 474−G26 are typical of galaxies that have experienced some kind of interaction during their evolution. We investigated two alternatives: a merging process and an accretion event.
14891588
The visible environment of galaxies with counterrotation
In this paper we present a statistical study of the environments of 49 galaxies in which there is gas- or stellar-counterrotation. The number of possible companions in the field (to apparent magnitude 22), their size and concentration were considered. All the statistical parameters were analysed by means of Kolgomorov-Smirnov tests, using a control sample of 43 galaxies without counterrotation. From our data, no significant differences between the counter-rotating and control samples appear. This is different to Seyfert or radio-loud galaxies which lie in environments with a higher density of companions. On the contrary, if a weak tendency exists, for galaxies with gas counterrotation only, it is discovered in regions of space where the large scale density of galaxies is smaller. Our results tend to disprove the hypothesis that counterrotation and polar rings derive from a recent interaction with a small satellite or a galaxy of similar size. To a first approximation, they seem to follow the idea that all galaxies are born through a merger process of smaller objects occurring very early in their life, or that they derive from a continuous, non-traumatic infall of gas that formed stars later. Whatever the special machinery is which produces counterrotation or polar rings instead of a co-planar, co-rotating distribution of gas and stars, it seems not to be connected to the present galaxy density of their environments.