Search

The tagged quasi-free np→npπ+π- reaction has been studied experimentally with the High Acceptance Di-Electron Spectrometer (HADES) at GSI at a deuteron incident beam energy of 1.25 GeV/nucleon (s~2.42 GeV/c for the quasi-free collision). For the first time, differential distributions of solid statistics for π+π- production in np collisions have been collected in the region corresponding to the large transverse momenta of the secondary particles. The invariant mass and angular distributions for the np→npπ+π- reaction are compared with different models. This comparison confirms the dominance of the t-channel with δδ contribution. It also validates the changes previously introduced in the Valencia model to describe two-pion production data in other isospin channels, although some deviations are observed, especially for the π+π- invariant mass spectrum. The extracted total cross section is also in much better agreement with this model. Our new measurement puts useful constraints for the existence of the conjectured dibaryon resonance at mass M~2.38 GeV and with width Γ~70 MeV.

The reaction p ( @ 3.5 GeV ) + p → p + Λ + K + can be studied to search for the existence of kaonic bound states like p p K − leading to this final state. This effort has been motivated by the assumption that in p + p collisions the Λ ( 1405 ) resonance can act as a doorway to the formation of the kaonic bound states. The status of this analysis within the HADES Collaboration, with particular emphasis on the comparison to simulations, is shown in this work and the deviation method utilized by the DISTO Collaboration in a similar analysis is discussed. The outcome suggests the employment of a partial wave analysis do disentangle the different contributions to the measured p K + Λ final state.

We study the production of Σ ± π ∓ p K + particle quartets in p + p reactions at 3.5 GeV kinetic beam energy. The data were taken with the HADES experiment at GSI. This report evaluates the contribution of resonances like Λ ( 1405 ) , Σ ( 1385 ) 0 , Λ ( 1520 ) , Δ ( 1232 ) , N ⁎ and K ⁎ 0 to the Σ ± π ∓ p K + final state. The resulting simulation model is compared to the experimental data in several angular distributions and it shows itself as suitable to evaluate the acceptance corrections properly.

The study of the properties of primary cosmic rays with energies above 100 TeV is only accessible indirectly through the use of detector arrays at the Earth surface. Despite the extremely high multiplicity of the air showers produced in their interactions at the highest layers of the atmosphere, only a fraction of those particles arrive to the ground over surfaces from ∼ 0.1 to ∼ 100 km 2 . The lack of information on the primary interaction and the low density of particles at the detection plane make the event by event analysis very complicated and usually only mean analysis are possible, sometimes with the help of simulation programs. The necessity of covering big surfaces to gather a significant sample of information usually leads to the use of big volume detectors with limited performances, giving only access to a small part of the information carried out by the swarm of secondary particles of the shower. In this article, we propose the development of an affordable detector, the TRASGO, based on timing RPCs (Resistive Plate Chambers) offering at the same time very good timing and tracking performances. TRASGO would allow a better and more accurate reconstruction of the air shower properties either working stand-alone or in big surface arrays.

An easy and fast matrix formalism for the tracking of charged particles through timing detectors is presented. The method is based on the least squares method and works directly with the first level data, that is, positions and readout times provided by timing detectors. In one step it provides the coordinates, the slopes, the velocity and an offset time at a given reference plane. The formalism is applied to some examples.

In this work we present results concerning the cosmic ray test, prior to the final installation and commissioning of the new Resistive Plate Chamber (RPC) Time of Flight (TOF) wall for the High-Acceptance DiElectron Spectrometer (HADES) at GSI. The TOF wall is composed of six equal sectors, each one constituted by 186 individual 4-gaps glass-aluminium shielded RPC cells distributed in six columns and 31 rows in two partially overlapping layers, covering an area of 1.26 m2. All sectors were tested with the final Front End Electronic (FEE) and Data AcQuisition system (DAQ) together with Low Voltage (LV) and High Voltage (HV) systems. Results confirm a very uniform average system time resolution of 77 ps sigma together with an average multi-hit time resolution of 83 ps. Crosstalk levels below 1% (in average), moderate timing tails along with an average longitudinal position resolution of 8.4 mm sigma are also confirmed.

The upgraded HADES inner TOF Wall will cover a total area of 8 m2 with 1116 variable-geometry 4-gap, symmetric, timing RPCs, readout by 2232 time and charge channels. Each RPC is individually shielded for robust multi-hit performance and optimum use of the readout channels (crosstalk minimization). The double layer configuration provides a useful degree of redundancy for very accurate timing of a large fraction of all particles crossing the detector. In this paper we describe the concept of the detector, its inner structure and the multi-hit performance.

We model the transient behaviour of an RPC exposed to intense irradiation by using as input the dielectric response function of the Resistive Plates measured experimentally. This work generalizes previous models to the (most common) case where the RPC response cannot be seen as a simple parallel RC circuit. Actually, the standard simplifying assumption that the corresponding RC constant can be estimated from the permittivity e{lunate} measured at high frequencies (e{lunate}∞) clearly fails at describing the observed RPC transients, while if using the measured dielectric response function a remarkable good agreement is obtained. © 2008 Elsevier B.V. All rights reserved.

We present a pulse generator able to generate pulses statistically similar to the ones produced by RPC cells. The device generates up to four arrays of fast and narrow random-like pulses. Polarity, maximum amplitudes, widths and pulse rate in each channel may be modified independently in order to simulate different RPC setups and environments. This portable and cost-effective pulse generator is a versatile instrument for testing FE-Electronics and different real detector features related with the signal propagation inside the detector. It has been developed in the framework of the ESTRELA 1 project of the HADES experiment at GSI.

A Front-End Electronics (FEE) chain for timing accurate measurements has been developed for the RPC wall upgrade of the High-Acceptance DiElectron Spectrometer (HADES). The wall will cover an area of around 8 m 2 with 1122 RPC cells (2244 electronic channels). The FEE chain consists of two boards: a four-channel DaughterBOard (DBO) and a 32-channel MotherBOard (MBO). The DBO uses a fast 2 GHz amplifier feeding a discriminator. The time and the charge information are encoded in the leading and the trailing edge (by a charge to width method) of an LVDS signal. Each MBO houses up to eight DBOs providing them regulated voltage supply, threshold values via DACs, test signals and collection of their trigger outputs. The MBO delivers LVDS signals to a time-to-digital converter readout board (TRB) based on HPTDC for data acquisition. In this work, we present the performance of the FEE measured using: (a) narrow electronic test pulses and (b) real signals read out in a fully instrumented RPC sextant installed in its final position at the HADES. The detector was exposed to particles coming from reactions of a 12 C beam on Be and Nb targets at 2 GeV/A kinetic energy. Results for the whole electronic chain ( DBO + MBO + TRB ) show a timing jitter of around 40 ps/channel for pulses above 100 fC and 80 ps/channel for beam data taken with the RPC.

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.

A new front-end electronics (FEE) system for RPC timing measurements has been developed for the ESTRELA project, which is part of the upgrade of the HADES experiment at GSI. The RPCs will cover an area of 8 m 2 with 2048 electronic channels. The chain consists on 2 boards: a 4-channel daughterboard (DB) and a 32-channel motherboard (MB). The DB uses a fast 2 GHz amplifier that feeds a discriminator with a constant threshold and an operational amplifier for a charge measurement by a Time-Over-Threshold (ToT) method for the integrated signal (for a slewing correction). The MB is connected to 8 DB, and provides voltage regulation, DACs for signal thresholds and a trigger logic. The MB delivers the differential output signals to an external HPTDC chip. Results are presented for (a) narrow electronic test pulses and for (b) RPC signals from gamma photons, showing a timing jitter around 15 ps/channel (for pulses above 100 fC) and 30-40 ps/channel, respectively. Tests with coincidently firing channels reveal levels of cross-talk below a 1% for a threshold of 25 fC, with a degradation of the time resolution of 10 ps at most.

The High Acceptance DiElectron Spectrometer HADES has been recently commissioned at GSI, Darmstadt. It has been designed for systematic studies of hadron properties inside nuclear matter. We report first preliminary results on invariant masses e + e - -pairs which were measured in 12 C + 12 C collisions at E kin = 2 GeV ⋅ A . The analysis methods are briefly outlined and a comparison with detailed Monte-Carlo simulations is shown.

Several recent important studies have clearly shown that a low physical fitness represents a potent risk factor and even a predictor of both cardiovascular and all-causes morbidity and mortality. As a consequence, physical fitness assessment should be performed at the clinical level since, when properly assessed, it is a highly valuable health and life expectancy indicator. Based on the results of fitness assessment in a particular person and knowing his/her life style and daily physical activity, an individually adapted training program can be prescribed. This training program will allow that person to develop his/her maximal physical potential while improving his/her physical and mental health and attenuating the deleterious consequences of aging. In fact, physical exercise is today proposed as a highly effective means to treat and prevent major morbidity and mortality causes in industrialized countries. Most of these causes are associated with the aging process. In order to be effective, this type of intervention should be directed to improve the aerobic capacity and strength. In addition, it should be complemented with work directed to improve the general coordination and flexibility. Finally, diet optimization and use of nutritional supplements and legal ergogenic aids are key elements to improve the functional capacity and health, all of which is synonymous of anti-aging interventions.

The control and monitoring system for the new HADES RPC time of flight wall installed at GSI Helmholtzzentrum fur Schwerionenforschung GmbH (Darmstadt, Germany), is described. The slow control system controls/monitors about 6000 variables from different physical devices via a distributed architecture, which uses intensively the 1-wire ® bus. The software implementation is based on the Experimental Physics and Industrial Control System (EPICS) software tool kit providing low cost, reliability and adaptability without requiring large hardware resources. The control and monitoring system attends five different subsystems: front-end electronics, low voltage, high voltage, gases, and detector.

SPb and SS interactions at 200 A GeV/c, as measured by the NA36 experiment at CERN, have been classified according to the number of participant protons of the projectile, by means of a precise identification of the charge of the projectile fragment produced. Rapidity and transverse momentum spectra of π- associated with the production of Z = 10 to Z = 15 projectile fragments are presented and compared to three models with different mechanisms of final particle production. © 1995.

The yields of Λ, Λ , and Ξ−, Ξ + have been measured close to mid-rapidity in sulphur reactions on a Pb target at 200 GeV/c per nucleon beam momentum. Fully corrected production ratios of Λ Λ , Ξ + Ξ , Ξ − Λ and Ξ Λ are presented. The ratios have been analysed both in the context of a rapidly disintegrating quark-gluon plasma and a hadronic resonance gas. Our analysis shows that the hadron gas model is sufficient to explain the observed particle yields.

The production of the strange particles Λ, \ gL and K0 S in p+Pb collisions at 200 GeV c has been measured using the NA36 TPC. Rapidity distributions and multiplicity dependences are presented and compared to model calculations. Reinteractions in the target are important to describe the observed spectra. Inverse slopes T |t200 MeV are extracted from the transverse mass distributions. © 1994.

A high speed data acquisition system was used to record events from sulphur-nucleus collisions at 200 GeV/c per nucleon at the CERN NA36 experiment. The system was designed to accept up to 12 Mbytes of raw data per beam spill. A multicrate Fastbus-CAMAC system was used to acquire the data during the beam spill and thereafter event-building and transfer to IBM 3480 cartridges were accomplished by means of two processors in a VME crate which processed data between spills. Communication between Fastbus and VME crates was provided by a fast link developed at CERN. © 1992.

p p annihilations, leading to the production of at least one neutral K meson in the final state, have been studied in the incident momentum region of 700–760 MeV/ c . Topological cross sections and cross sections for the various exclusive final states are presented. Detailed analyses of the different final states have been carried out to study the importance of resonance production and of quasi two-body and quasi three-body processes. A detailed study of the K K π system in the four-body final states shows that the F 1 meson is a spurious effect due to systematic biases. In the momentum range investigated, the C = +1 final states are strongly suppressed.