110524479
Experimental study of a cylindrical scintillating fiber detector
A tracking detector made of scintillating fibers is being developed at FNAL, for the experiment E835. The tracker will be used for the measurement of the polar angle /spl theta/, i.e. of the coordinate along the beam. The small amount of light from the fibers will be detected by solid state devices (visible light photon counters) with very high quantum efficiency. This paper reports the performance of a fiber tracker prototype, as measured at FNAL. We present results on light yield/mip, efficiency and homogeneity of response. We measured an average number of about 14 photoelectrons per mip and an efficiency higher than 99%. >
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.
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.
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.
125331327
The Fermilab anti-p accumulator ring for the charmonium experiment
118665124
The innermost region of the NGC 1023 Group: Insight into its evolution
The NGC 1023 group is one of the most studied nearby groups. We want to give an insight into the evolution of its innermost region by means of ultraviolet observations and proper models. We used the FUV and NUV GALEX archival data as well as a large set of SPH simulations with chemo-photometric implementation. From the UV observations we found that several, already known, dwarf galaxies very close to NGC 1023 are also detected in UV and two more objects (with no optical counterpart) can be added to the group. Using these data we construct exhaustive models to account for their formation. We find that the whole SED of NGC 1023 and its global properties are well matched by a simulation which provides a minor merger with a companion system 5 times less massive. The strong interaction phase started 7.7Gyr ago and the final merger 1.8Gyr ago.
14276856
The fundamental plane of early-type galaxies in nearby clusters from the WINGS database
By exploting the data of three large surveys (WINGS, NFPS, and SDSS), we analyze the fundamental plane (FP) of early-type galaxies (ETGs) in 59 nearby clusters ( -->0.04 < z < 0.07). We show that the variances of the FP coefficients for our clusters are just marginally consistent with the hypothesis of universality of the FP. We found they are influenced by the distribution of photometric/kinematic properties of galaxies in the particular sample under analysis, suggesting that the FP is actually a bent surface. We also find a strong correlation between the local density and the FP coefficients, while they appear to be poorly correlated with the global properties of clusters. The relation between luminosity and mass of our galaxies, computed by assuming Sersic luminosity profiles, indicates that, for a given mass, the greater the light concentration, the higher the luminosity, while, for a given luminosity, the lower the light concentration, the greater the mass. Moreover, the M/L versus mass relation (again with Sersic profile fitting) turns out to be steeper and broader than that obtained for the Coma Cluster sample with de Vaucouleurs profile fitting. This broadness, together with the FP bending, might reconcile the FP phenomenology with the expectations from the ΛCDM cosmology. We conclude that the claimed universality of the FP of ETGs is still far from being proved and that systematic biases might affect the studies of luminosity evolution of ETGs, since data sets at different redshifts and with different distributions of the photometric/kinematic galaxy properties are compared each other.
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.
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.
18512375
GALEX UV properties of the polar ring galaxy MCG-05-07-001 and the shell galaxies NGC 1210 and NGC 5329
Context. Systems of shells and polar rings in early-type galaxies are considered “bona fide” tracers of mass accretion and/or mergers. Their high frequency in low density environments suggests that these processes could drive the evolution of at least a fraction of the early-type galaxy population. Aims. We investigate the star formation histories of this type of galaxies. Their UV emission is important for testing whether these galaxies host ongoing or recent star formation and how this formation varies across the galaxy. Methods. We used far- and near- ultraviolet, optical, near-infrared images, neutral hydrogen HI maps, and line-strength indices to investigate the nuclear and outer regions of these galaxies as well as the regions where fine structures are present. Results. The GALEX near UV (NUV) and far UV (FUV) images of MCG-05-07-001 and NGC 1210 show complex tidal tails and debris structures. The far UV morphology of both galaxies appears so different from the optical morphology that the early-type classification may not apply. In both GALEX bands, the polar ring of MCG-05-07-001 is the dominant feature, whereas an extended tidal tail dominates the FUV bands of NGC 1210. In MCG-05-07-001 and NGC 1210, there is a strong correlation between structures detected in the FUV and NUV bands and in HI. In contrast, NGC 5329 does not show evidence of shells in the GALEX bands. We try to constrain the age of the accretion episode or merger that produced the shells and polar rings with the aid of composite stellar populations that take the presence of dust into account. The presence of HI in both MCG-05-07-001 and NGC 1210 argues in favour of wet mergers. Models suggest the presence of very young stellar populations in MCG-05-07-001: the observations could be explained in the framework of a conspicuous burst of star formation that occurred ≤1 Gyr ago and involved a large fraction of the galaxy mass. Our models suggest that also the nuclei of NGC 1210 and NGC 5329 could have been rejuvenated by an accretion episode about 2–4 Gyr ago.