Search

We studied the star formation rate (SFR) in cosmological hydrodynamical simulations of galaxy (proto-)clusters in the redshift range $0, Comment: 20 pages, 19 figures. Accepted for publication in A&A

Recently, relations connecting the SMBH mass of central galaxies and global properties of the hosting cluster, such as temperature and mass, were observed. We investigate the correlation between SMBH mass and cluster mass and temperature, their establishment and evolution. We compare their scatter to that of the classical $M_{\rm BH}-M_{\rm BCG}$ relation. We study how gas accretion and BH-BH mergers contribute to SMBH growth across cosmic time. We employed 135 groups and clusters with a mass range $1.4\times 10^{13}M_{\odot}-2.5\times 10^{15} M_{\odot}$ extracted from a set of 29 zoom-in cosmological hydro-dynamical simulations where the baryonic physics is treated with various sub-grid models, including feedback by AGN. In our simulations we find that $M_{\rm BH}$ correlates well with $M_{500}$ and $T_{500}$, with the scatter around these relations compatible within $2\sigma$ with the scatter around $M_{\rm BH}-M_{\rm BCG}$ at $z=0$. The $M_{\rm BH}-M_{500}$ relation evolves with time, becoming shallower at lower redshift as a direct consequence of hierarchical structure formation. On average, in our simulations the contribution of gas accretion to the total SMBH mass dominates for the majority of the cosmic time ($z>0.4$), while in the last 2 Gyr the BH-BH mergers become a larger contributor. During this last process, substructures hosting SMBHs are disrupted in the merger process with the BCG and the unbound stars enrich the diffuse stellar component rather than increase BCG mass. From the results obtained in our simulations with simple sub-grid models we conclude that the scatter around the $M_{\rm BH}-T_{500}$ relation is comparable to the scatter around the $M_{\rm BH}-M_{\rm BCG}$ relation and that, given the observational difficulties related to the estimation of the BCG mass, clusters temperature and mass can be a useful proxy for the SMBHs mass, especially at high redshift., Comment: 16 pages, 17 figures, 3 tables

We report a detailed CO(1-0) survey of a galaxy protocluster field at $z=2.16$, based on 475 hours of observations with the Australia Telescope Compact Array. We constructed a large mosaic of 13 individual pointings, covering an area of 21 arcmin$^2$ and $\pm6500$ km/s range in velocity. We obtain a robust sample of 46 CO(1-0) detections spanning $z=2.09-2.22$, constituting the largest sample of molecular gas measurements in protoclusters to date. The CO emitters show an overdensity at $z=2.12-2.21$, suggesting a galaxy super-protocluster or a protocluster connected to large-scale filaments with ~120 cMpc size. We find that 90% CO emitters have distances $>0'.5-4'$ to the center galaxy, indicating that small area surveys would miss the majority of gas reservoirs in similar structures. Half of the CO emitters have velocities larger than escape velocities, which appears gravitationally unbound to the cluster core. These unbound sources are barely found within the $R_{200}$ radius around the center, which is consistent with a picture in which the cluster core is collapsed while outer regions are still in formation. Compared to other protoclusters, this structure contains relatively more CO emitters with relatively narrow line width and high luminosity, indicating galaxy mergers. We use these CO emitters to place the first constraint on the CO luminosity function and molecular gas density in an overdense environment. The amplitude of the CO luminosity function is 1.6$\pm$0.5 orders of magnitudes higher than observed for field galaxy samples at $z\sim2$, and one order of magnitude higher than predictions for galaxy protoclusters from semi-analytical SHARK models. We derive a high molecular gas density of $0.6-1.3\times10^{9}$ $M_\odot$ cMpc$^{-3}$ for this structure, consistent with predictions for cold gas density of massive structures from hydro-dynamical DIANOGA simulations., 21 pages + Appendices, 9 figures, 6 tables. Accepted for publication in A&A

We carry out a comprehensive Bayesian correlation analysis between hot halos and direct masses of supermassive black holes (SMBHs), by retrieving the X-ray plasma properties (temperature, luminosity, density, pressure, masses) over galactic to cluster scales for 85 diverse systems. We find new key scalings, with the tightest relation being the $M_\bullet-T_{\rm x}$, followed by $M_\bullet-L_{\rm x}$. The tighter scatter (down to 0.2 dex) and stronger correlation coefficient of all the X-ray halo scalings compared with the optical counterparts (as the $M_\bullet-\sigma_{\rm e}$) suggest that plasma halos play a more central role than stars in tracing and growing SMBHs (especially those that are ultramassive). Moreover, $M_\bullet$ correlates better with the gas mass than dark matter mass. We show the important role of the environment, morphology, and relic galaxies/coronae, as well as the main departures from virialization/self-similarity via the optical/X-ray fundamental planes. We test the three major channels for SMBH growth: hot/Bondi-like models have inconsistent anti-correlation with X-ray halos and too low feeding; cosmological simulations find SMBH mergers as sub-dominant over most of the cosmic time and too rare to induce a central-limit-theorem effect; the scalings are consistent with chaotic cold accretion (CCA), the rain of matter condensing out of the turbulent X-ray halos that sustains a long-term self-regulated feedback loop. The new correlations are major observational constraints for models of SMBH feeding/feedback in galaxies, groups, and clusters (e.g., to test cosmological hydrodynamical simulations), and enable the study of SMBHs not only through X-rays, but also via the Sunyaev-Zel'dovich effect (Compton parameter), lensing (total masses), and cosmology (gas fractions)., Comment: 40 pages, 27 figures, 3 tables; ApJ accepted version (minor revision) - Reviewer: "The authors are to be congratulated on a very interesting paper that deserves to be read by anyone interested in the connection between the SMBH and host galaxy."

A demanda por fibras de algodao de alta qualidade para atender a demanda da industria textil e a busca incessante para reduzir a presenca de contaminantes no momento da colheita de forma a contribuir para a reducao dos custos. O objetivo da pesquisa foi avaliar a eficiencia da plataforma Picker VRS (unidades de espacamento variavel) de colheita do algodao adensado no Estado de Mato Grosso, com e sem placas de raspagem, variando a velocidade de deslocamento, quantificando as impurezas nesse processo e avaliando a qualidade extrinseca e intrinseca da fibra colhida. A pesquisa foi dividida em 3 experimentos (Exp. I, II e III). As variedades de algodao utilizadas foram FM 975 WS, IMA 5672 B2 RF e IMA 5675 B2 RF, com espacamentos entre linhas de 0,45 m. O delineamento experimental utilizado foi de blocos casualizados, em esquema fatorial 2x3, sendo presenca e ausencia da placa e tres velocidades de trabalho (0,61; 1,0 e 1,42m.s-¹), com sete repeticoes, totalizando 42 parcelas experimentais. A dimensao das parcelas foi de 108m² (3,6 x 30m). Os resultados obtidos foram submetidos a analise de variância por meio do Teste de F, e quando significativos submetidos ao teste de Tukey, a 5 % de probabilidade. As placas de raspagem aumentaram a quantidade de caule, casquinhas e reduziu a eficiencia na colheita do algodao adensado na regiao de Sorriso-MT na safra 2013/2014. Para a safra 2014/2015 a maior velocidade e a presenca das placas de raspagem aumentaram a quantidade de casquinhas nas amostras de algodao em caroco. No experimento realizado na Serra da Petrovina a retirada das placas de raspagem diminuiu a quantidade de cascas no algodao colhido.

International audience; The elliptic-flow ratio of neutrons with respect to protons or light complex particles in reactions of heavy ions at pre-relativistic energies has been proposed as an observable sensitive to the strength of the symmetry term of the nuclear equation of state at supra-saturation densities. In the ASY-EOS experiment at the GSI laboratory, flows of neutrons and light charged particles were measured for ^197Au+^197Au collisions at 400 MeV/nucleon. Flow results obtained for the Au+Au system, in comparison with predictions of the UrQMD transport model, confirm the moderately soft to linear density dependence of the symmetry energy deduced from the earlier FOPI-LAND data.

Nuclear matter under extreme conditions can be studied in the laboratory with heavy-ion collisions. In this case one can indeed vary the incident energy and explore different impact parameter and rapidity regions to access densities that extend above and below saturation. This opportunity allows one to learn about the nuclear equation of state and its implications in astrophysics phenomena such as supernovae explosions and neutron stars properties. All these phenomena involve time scales that need to be accessed with two- and multi-particle correlation measurements. In this contribution a brief report of the FARCOS array will be presented. In particular, tests with alpha sources and beams and preliminary results from a recent experiment INKIISSY performed using a FARCOS prototype made of four telescopes will be presented.

Isotopic effects in projectile fragmentation at relativistic energies have been studied with the ALADIN forward spectrometer at SIS. Stable and radioactive Sn and La beams with an incident energy of 600 MeV per nucleon have been used in order to explore a wide range of isotopic compositions. Chemical freeze-out temperatures are found to be nearly invariant with respect to the A/Z ratio of the produced spectator sources, consistent with predictions for expanded systems. Consequences for the proposed interpretation of chemical breakup temperatures as representing the limiting temperatures predicted by microscopic models are discussed., Comment: 7 pages, 4 figures, contribution to proceedings of International School of Nuclear Physics, 30th Course, Heavy-Ion Collisions from the Coulomb Barrier to the Quark-Gluon Plasma, Erice-Sicily: 16 - 24 September 2008

The emission of e+ e- pairs from C + C collisions at an incident energy of 1 GeV per nucleon has been investigated. The measured production probabilities, spanning from the π0-Dalitz to the ρ / ω invariant-mass region, display a strong excess above the cocktail of standard hadronic sources. The bombarding-energy dependence of this excess is found to scale like pion production, rather than like eta production. The data are in good agreement with results obtained in the former DLS experiment. © 2008 Elsevier B.V. All rights reserved.

The properties of a cylindrical 1 00 � 1 00 LaBr3:Ce scintillator (Brillance 380) were investigated. The energy resolution at g-ray energy of 662 keV was measured to be smaller than 3% and the intrinsic time resolution was found to be E230 ps. Two different aspects were investigated. The first is the detailed study of the crystal self-activity, emitting a and b particles and g-rays, by measuring coincidences with g-rays in HPGe, BGO and BaF2 detectors. In particular, the coincidence with an HPGe detector allowed to isolate clearly the different contributions from 227 Ac (chemical homologue of lanthanum) and its daughter nuclei down to the stable 207 Pb. The second aspect is the determination of the efficiency for g-ray detection, measured at 1 MeV and simulated using GEANT4 up to 15 MeV as a function of the detector size.

A systematic study of isotopic effects in the break-up of projectile spectators at relativistic energies has been performed with the ALADiN spectrometer at the GSI laboratory. Searching for signals of criticality in the fragment production we have applied the model independent universal fluctuations theory already proposed to track criticality signals in multifragmentation to our data. The fluctuation of the largest fragment charge and of the asymmetry of the two and three largest fragments and their bimodal distribution have also been analysed., Comment: 6 pages, 4 figures, IX International Conference on Nucleus-Nucleus Collisions, Rio de Janeiro, Brazil, August 28 - September 1, 2006

A fast gateless pulse stretcher has been developed for an easy acquisition of pulse-shape information of BaF/sub 2/ scintillator signals. Commonly, this information is obtained by the use of two QDCs with different integration windows. This technique becomes complex and rather inconvenient when signals need to be delayed. The developed circuit uses a fast-stretcher technique to generate pulse-shape information, which requires no delay lines or gate signals. The outputs consist of two Gaussian signals whose amplitudes are proportional to the height of the BaF/sub 2/ fast component and to the total energy deposited into the scintillator. These outputs are easily acquired with a standard peak ADC with no gate-timing problems. An excellent Fast-Slow separation has been obtained even with small input signals of only few millivolts. This technology is general purpose and can be used with any other scintillator whose light emission is characterized by two components with different lifetimes.

The elliptic-flow ratio of neutrons with respect to protons in reactions of neutron rich heavy-ions systems at intermediate energies has been proposed as an observable sensitive to the strength of the symmetry term in the nuclear Equation Of State (EOS) at supra-saturation densities. The recent results obtained from the existing FOPI/LAND data for $^{197}$Au+$^{197}$Au collisions at 400 MeV/nucleon in comparison with the UrQMD model allowed a first estimate of the symmetry term of the EOS but suffer from a considerable statistical uncertainty. In order to obtain an improved data set for Au+Au collisions and to extend the study to other systems, a new experiment was carried out at the GSI laboratory by the ASY-EOS collaboration in May 2011., Comment: Talk given by P. Russotto at the 11th International Conference on Nucleus-Nucleus Collisions (NN2012), San Antonio, Texas, USA, May 27-June 1, 2012. To appear in the NN2012 Proceedings in Journal of Physics: Conference Series (JPCS)

We investigated the merits of different event parameters in the identification of Light Charged Particles (LCPs) with CsI(Tl) scintillators read out by photodiodes at high incident energy (400 MeV/u). This investigation is made possible by digital signal processing the output signals. As in the conventional analogue case, the digitized signals allow the discrimination of light charged particles by computing the fast and slow components. In addition other identification parameters as the rise time of the output pulses of the CsI(Tl) come out nearly for free. Aim of this paper is the investigation of novel identification plots and the probe of their merits, in particular at relativistic energies. When the energies of the light charged particles exceed those corresponding to their ranges in CsI(Tl), the points related to the punching-through particles gather in the corresponding scatter plots giving rise to a cusp. The punch-through energies provide a complete set of data for the energy calibration of the reaction products stopped in the CsI(Tl). The obtained results suggest that at relativistic beam energies the energy vs. rise time computation provide an efficient figure for the discrimination in charge and mass of LCPs.

Detector telescopes having a Δ E – E configuration, consisting of either a Si surface barrier detector or a Si strip detector followed by a NaI(Tl) stopping detector, are described for measuring intermediate mass fragments in 12 C-induced reactions to the continuum. These include the stable break-up fragments 7 Be and 9 Be, as well as the resonant fragment 8 Be. Energy calibration of the stopping detectors is based on a scintillation light-response model. Empirical approximating functions have been selected for inverting the theoretical functions relating light output to particle energy, in order to achieve calibration during rapid data sorting. The detector efficiency for resonant fragments is obtained by means of a Monte Carlo simulation. A dedicated eight-channel preamplifier module with good operational stability in vacuum, specifically designed for Si-strip detectors, is also described.

The Rare ISotopes INvestigation at GSI project combines the former EUROBALL Ge-Cluster detectors, the MINIBALL Ge detectors, BaF2--HECTOR detectors, and the fragment separator at GSI for high-resolution in-beam gamma-ray spectroscopy measurements with radioactive beams. These secondary beams produced at relativistic energies are used for Coulomb excitation or secondary fragmentation experiments in order to explore the nuclear structure of the projectiles or projectile like nuclei by measuring de-excitation photons. The newly designed detector array is described and the performance characteristics are given. Moreover, particularities of the experimental technique are discussed.

We suggest that some key physical parameters of high-purity germanium (HPGe) segmented detectors, including segment capacitance and leakage current, can be derived from standard noise measurements. These parameters are relevant when designing and optimizing the front-end electronics.

A new hybrid charge-sensitive preamplifier with a sensitivity of 5 mV/MeV has been specifically designed to operate in conjunction with high-capacitance silicon detectors. The shape of the leading edge of its impulse response remains fast (20 ns) and unchanged over the full output voltage range (7 V), as is required in nuclear-physics experiments in which pulse-shape analysis is used for particle identification. The circuit is miniaturized onto two sides of a ceramic substrate as small as 17/spl times/23 mm/sup 2/. A low-noise fast discharge technique is used: the return to the high-value feedback resistor (R/sub F/) comes from a noninverting low-gain (A) amplifier cascaded to the principal charge-amplifier loop. This yields a reduction of the fall time of a factor A, with no changes of C/sub F/ and R/sub F/ and no added noise. The shorter fall time reduces the pileup effects in presence of high event rates. Special care has been devoted to the matching between the high capacitance of the detector and that of the input stage of the preamplifier. To match a high capacitance, four BF862 field-effect transistors have been connected in parallel.

A 100 Msamples/s 14-bit sampling analog-to-digital converter has been used to perform digital pulse-shape acquisition of signals collected from CHIMERA telescopes. Two different kinds of tests have been carried out to check the performances. The signals from a typical CHIMERA detection cell have been collected using both a standard CHIMERA electronic chain up to the amplifier, and a very simple analog front end, basically reduced to the preamplifier. The obtained on-beam and on-line results are presented.

In this paper, we propose a new add-on circuit structure that swiftly desaturates a digitized charge preamplifier for ionizing-radiation detectors when an energetic event occurs, or when a burst of piled up events puts it into saturation. The amplitude of the energetic event can even be reconstructed with a time-over-threshold (TOT) measurement of the fast-reset transient. With an analog-to-digital converter (ADC) range of 10 MeV, we were able to measure events of up to 100 MeV. The circuit is conceived for experiments where a spurious background of energetic particles and photons exists, such those with exotic beams in the new generation of nuclear-physics research facilities.

We report the results obtained by applying digital pulse shape acquisition and digital signal processing to the signals from CsI(Tl) scintillators read out by photodiodes at high incident energy (400 MeV/u). The digitized signals allows the discrimination of light charged particles by computing the Fast and Slow components and the Rise Time of the output pulses of the CsI(Tl). When the energies of the light charged particles exceed those corresponding to their ranges in CsI(Tl), the points related to the punching-through particles gather in the corresponding scatter plots giving rise to a cusp. The punching-through points are used as energy calibration points for the reaction products stopped in the CsI(Tl). The obtained results suggest that at relativistic beam energies it is possible to perform efficient discrimination in charge and mass of light charged particles by using the energy vs. rise time computation. © 2011 IEEE.

Two-point charge division is a typical technique for position measurements in linear multi electrode detectors (microstrips, multiwire proportional counters, silicon drift-detector arrays, and scintillators coupled to photodetectors). Only two preamplifiers, located at the right and the left ends of the detection array, are used, each of which receives a fraction of the charge produced by the ionizing event. Position is reconstructed comparing these charge fractions. In principle, either a resistive or a capacitive divider may be used to split the charge. The choice between such two different setups is not obvious. In fact, each of them shows advantages and disadvantages in terms of noise, signal propagation, and linearity. In this paper, we present a unified treatment for the capacitive and the resistive mechanisms of charge division that addresses the issues of this choice. As an example, the realistic setup of the multiwire position-sensitive proportional counter to be used in the TP-MUSIC III chamber of the ALADiN experiment at GSI is considered.

A new hybrid, low-noise, wide-bandwidth charge amplifier, using a new active discharge mechanism, has been designed and built primarily for gamma-ray tracking detectors, where a fast rise time is required. In order to realize the discharge of the feedback capacitance, a noninverting low-gain (A) stage has been inserted between the output of a conventional charge preamplifier and the high-value feedback resistance. This technique allows to make the discharge time constant shorter (by factor A), while keeping the feedback resistor as the feedback capacitance unchanged. Special care has been devoted realizing the hybrid layout to reduce the stray capacitance of the feedback resistor and particular attention has been dedicated to assure a good signal-to-noise ratio and a fast rise time. A low-power consumption allows the use of this charge-sensitive preamplifier in vacuum chamber without cooling system. The noise level is equivalent to less than 880-eV full width half maximum for an input capacitance of 22 pF, using 3-/spl mu/s shaping time. The noise grows with a slope of less than 10 eV/pF in the range of 20-60 pF input capacitance. This suggests that the preamplifier can be operated at room temperature maintaining a good noise usually reachable with a cooled setup.

At intermediate energies, the (d, He-2) charge-exchange reaction can be used to observe Gamow-Teller strength in the direction. He-2 denotes the two-proton system being in the singlet S-1(0) state. In the present experiment the two protons, which in the laboratory frame are emitted into the forward direction, have been momentum analyzed and detected in coincidence by the same spectrometer and detector. Protons from deuteron breakup processes can induce a large accidental coincidence background because of the much larger breakup cross-section as compared to the (d, He-2) cross-section. Nevertheless, background-free He-2 spectra with a resolution of 145 keV at an incident energy of 170 MeV are obtained, allowing the identification of many levels with high precision in the residual nuclei. The essential features of the detection system and the data-acquisition and analysis techniques which make our (d 2 He) experiments possible are described. Two nuclei, C-12 and Mg-24, have been used as a test case. (C) 2002 Elsevier Science B.V. All rights reserved.

We present a new discharge mechanism for low-noise fast preamplifiers for /spl gamma/-ray spectroscopy. Such circuital solution has been conceived in the framework of the INFN Mars experiment, which imposes stringent requirements for both the signal-to-noise ratio and the rise time of the front-end preamplifiers. Basically, a noninverting low-gain (G) stage is interposed between the output of a conventional charge amplifier and the high-value feedback resistor. It can be easily found that this adds no noise but the discharge time constant is reduced by a factor G, because the voltage drop across the resistor is G times as high, and such is the discharge current. A similar effect could also be obtained in the standard charge amplifier by diminishing the feedback resistor by a factor G. But this would yield an increase of a factor G of its thermal current noise. In this sense our equivalent discharge resistor is "cold", because it carries a current noise G times as low. This permits us to use a relatively large feedback capacitance which inherently yields a fast risetime. A rise time of 15 ns and an overall electronic noise of 1.03 keV FWNM at 3 /spl mu/s shaping time have been obtained, with an input capacitance of 33 pF, and 1.5 pF feedback capacitor, 150 /spl mu/s discharge time constant.

For the medium-energy proton polarimeter mounted at the focal-plane of the Big-Bite Spectrometer at Kernfysisch Versneller Instituut Groningen, a new wire-chamber readout has been developed. The charge-sensitive preamplifier is based on the ASD-8 B chip which has an input impedance of 115 /spl Omega/. This low impedance and the short integration time of 6 ns at a usable sensitivity of 5 fC allow high readout rates and low gas amplifications. This front-end circuit is mounted on all four multi-wire proportional chambers and on two vertical-drift chambers with 3872 wires in total. Measurements have been made using sources and intermediate energy protons. Special attention was given to determine the time-over-threshold properties of the circuit. The time-over-threshold capabilities of the readout system extend future applications to particle discrimination, or, in connection with other detector types, to energy-resolving readout. The operational performance of the readout system is presented.

It is suggested that the spectra of the 8Be ground-state (gs) nuclei produced in the interaction of 12C with 59Co at incident energies varying from 8.3 to 33.3MeV/amu can be explained by introducing a dissipative friction interaction mechanism preceding projectile break-up.

Temperature-excitation energy correlation measurements on several systems at different incident energies are discussed in the framework of the investigation on possible liquid-gas phase transition in nuclear matter. Results are compared to the presently available experimental caloric curves. Moreover theisotope and theexcited states temperatures, extracted from double ratios of isotope yields and population ratios of fragment unbound states, respectively, are compared. p ]The differences on the temperatures deduced from the two methods cannot be accounted for by the sequential feeding corrections. Instead, they seem to be related to the space-time evolution of the fragmentation process.

In the framework of the HADES (High Acceptance DiElectron Spectrometer) collaboration we are developing the Time Of Flight (TOF) wall subdetector. In order to efficiently select events with e/sup +/e/sup -/ pairs produced in the nuclear matter, the TOF wall must be able to resolve electrons from pions up to 0.5 GeV/c and from protons up to 2 GeV/c. Because the short flight path of about 2 m requires a 100-150 ps time resolution, we are building a granular system made of scintillator rods readout on both ends by means of photomultipliers, capable of such performance.

Spectator decay was studied for the system Au + Au at an energy of 1000 A·MeV and the decay of the interaction region at energies between 50 and 200 A·MeV. In both cases temperatures were derived from several double-ratios of neighboring isotopes and from the population of excited states in 5 Li and 4 He. Agreement was found among the different isotope temperatures and also among the two excited state temperatures. The comparison of isotope and excited state temperatures, however, reveals large differences, which cannot be explained by feeding corrections. At incident energies between 600 and 1000 A·MeV the energy spectra of fragments and also neutrons of the decaying projectile spectator were measured. Whereas the slope parameters of the energy spectra and mean energies for fragments with Z ≥ 2 are independent of the incident energy, a strong dependence is found for the lightest particles, so that preequilibrium contributions to the spectator decay should be taken into account.

Heavy ion studies with stable and exotic beams require the identification of nuclear frag- ments in a broad range of mass and atomic numbers. Recent progresses of the Pulse Shape Discrimination (PSD) method applied to the current signals of silicon detectors have en- couraged new studies in this field. The aim of our experimental study was to progress in this technique by applying PSD to charge signals produced in planar silicon detectors of large capacitance (1nF). A new electronic design based on a double constant-fraction discrimination of timing signals, was applied to some of the CHIMERA Si detectors, by using Tandem and Cyclotron beams delivered by the LNS in Catania. We obtained charge identification with energy threshold of about 4 AMeV from Z=1 up to fluorine and with good timing performances (direct injection mode). Our recent results strongly encourage for further application to 4π detection systems in the field of exotic beams.

Breakup temperatures were deduced from double ratios of isotope yields for target spectators produced in the reaction Au + Au at 1000 MeV per nucleon. Pairs of $^{3,4}$He and $^{6,7}$Li isotopes and pairs of $^{3,4}$He and H isotopes (p, d and d, t) yield consistent temperatures after feeding corrections, based on the quantum statistical model, are applied. The temperatures rise with decreasing impact parameter from 4 MeV for peripheral to about 10 MeV for the most central collisions. The good agreement with the breakup temperatures measured previously for projectile spectators at an incident energy of 600 MeV per nucleon confirms the observed universality of the spectator decay at relativistic bombarding energies. The measured temperatures also agree with the breakup temperatures predicted by the statistical multifragmentation model. For these calculations a relation between the initial excitation energy and mass was derived which gives good simultaneous agreement for the fragment charge correlations. The energy spectra of light charged particles, measured at $\theta_{lab}$ = 150$^{\circ}$, exhibit Maxwellian shapes with inverse slope parameters much higher than the breakup temperatures. The statistical multifragmentation model, because Coulomb repulsion and sequential decay processes are included, yields light-particle spectra with inverse slope parameters higher than the breakup temperatures but considerably below the measured values. The systematic behavior of the differences suggests that they are caused by light-charged-particle emission prior to the final breakup stage. PACS numbers: 25.70.Mn, 25.70.Pq, 25.75.-q

An apparatus for cyclic charged particle activation was designed, built and connected to the 7 MV Van de Graaff CN accelerator of the Laboratori Nazionali dell'Istituto Nazionale di Fisica Nucleare di Legnaro (Italy). It mainly consists of a two-sample transverse moving system controlled by a Cycle Control Module (CCM). This module is based on a Programmable Logic Device (PLD) for the definition of the requested flow-maps and functions. The CCM operates the cc motor for sample movements by means of a power width modulation technique. It also controls the beam switch and the setting mode of the acquisition system which is connected to two HPGe detectors. As a feasibility test, the best experimental conditions for aluminium determination in complex. Al-doped biological samples were found to be an irradiation time of 3.5 minutes and a measuring time of 6 minutes. The signal to background ratio is reported as a function of the number of cycles.

A 100 MS/s 14-bit Sampling Analog-to-Digital converter has been used to perform digital pulse-shape acquisition. The signals from a typical CHIMERA detector cell are collected both using a standard CHIMERA electronic chain, up to the amplifier, and directly from the preamplifier. The preliminary on-beam results are presented.

Cross sections for the charge pickup of {sup 238}U projectiles were measured at {ital E}/{ital A}=600 and 1000 MeV for seven different targets (Be, C, Al, Cu, In, Au, and U). Events with two fission fragments with a sum charge of 93 in the exit channel were selected. Due to the significant excitation energy, the majority of the produced Np nuclei fission instead of decaying by evaporation to residues. The observed cross sections can be well reproduced by intranuclear-cascade-plus-evaporation calculations and, therefore, confirm recent results that no exotic processes are needed to explain charge-pickup processes. {copyright} {ital 1996 The American Physical Society.}

Results on the deep sub-threshold production of the short-lived hadronic resonance K*(892)0 are reported for collisions of Ar + KCl at 1.76A GeV beam energy, studied with the High Acceptance Di-Electron Spectrometer (HADES) at SIS18/GSI. The K*(892)0 production probability per central collision of \( P_{K^{*0}}=(4.4\pm 1.1 \pm 0.5)\times 10^{-4}\) and the K*(892)0/K0 ratio of \( P_{K^{*0}}/P_{K^0}=(1.9\pm 0.5\pm 0.3)\times 10^{-2}\) are determined at the lowest energy so far (i.e. deep below the threshold for the corresponding production in nucleon-nucleon collisions, \( \sqrt{s_{NN}}-\sqrt{s_{thr}}=-340\) MeV). The K*0/K0 ratio is compared with results of other experiments and with the predictions of the UrQMD transport approach and of the statistical hadronization model. The experimental K*0 yield and the K*0/K0 ratio are overestimated by the transport model by factors of about five and two, respectively. In a chemically equilibrated medium the ratio corresponds to a temperature of the thermalized system being systematically lower than the value determined by the yields of the stable and long-lived hadrons produced in Ar + KCl collisions. From the present measurement, we conclude that sub-threshold K* production either cannot be considered to proceed in a system being in thermal equilibrium or these short-lived resonances appear undersaturated, for example as a result of the rescattering of the decay particles in the ambient hadronic medium.

We present measurements of exclusive \pi^{+,0} and \eta\ production in pp reactions at 1.25 GeV and 2.2 GeV beam kinetic energy in hadron and dielectron channels. In the case of \pi^+ and \pi^0, high-statistics invariant-mass and angular distributions are obtained within the HADES acceptance as well as acceptance corrected distributions, which are compared to a resonance model. The sensitivity of the data to the yield and production angular distribution of \Delta(1232) and higher lying baryon resonances is shown, and an improved parameterization is proposed. The extracted cross sections are of special interest in the case of pp \to pp \eta, since controversial data exist at 2.0 GeV; we find \sigma =0.142 \pm 0.022 mb. Using the dielectron channels, the \pi^0 and \eta\ Dalitz decay signals are reconstructed with yields fully consistent with the hadronic channels. The electron invariant masses and acceptance corrected helicity angle distributions are found in good agreement with model predictions., Comment: 22 pages, 18 figures, to be published in EPJA

The performance of the LAND neutron detector is studied. Using an event-mixing technique based on one-neutron data obtained in the S107 experiment at the GSI laboratory, we test the efficiency of various analytic tools used to determine the multiplicity and kinematic properties of detected neutrons. A new algorithm developed recently for recognizing neutron showers from spectator decays in the ALADIN experiment S254 is described in detail. Its performance is assessed in comparison with other methods. The properties of the observed neutron events are used to estimate the detection efficiency of LAND in this experiment., 16 pages, 8 figures

After the completion of the experimental program at SIS18 the HADES setup will migrate to FAIR, where it will deliver high-quality data for heavy-ion collisions in an unexplored energy range of up to 8 A GeV. In this contribution, we briefly present the physics case, relevant detector characteristics and discuss the recently completed upgrade of HADES. © 2012 Pleiades Publishing, Ltd. 75 5 589 593 Cited By :6

Data on inclusive dielectron production are presented for the reaction p+p at 2.2 GeV measured with the high acceptance dielectron spectrometer (HADES). Our results supplemented data obtained earlier in this bombarding energy regime with the dilepton spectrometer (DLS) and HADES. The comparison with the 2.09 GeV DLS data is discussed. The reconstructed e+e- pair distributions are confronted with simulations, revealing an excess yield at invariant masses around 0.5 GeV/c2. Inclusive cross sections of neutral pion and η production are obtained. © 2012 American Physical Society. 85 5 Cited By :20