.
We present measurements of exclusive
and
production in pp reactions at 1.25GeV and 2.2GeV beam kinetic energy in hadron and dielectron channels. In the case of
and
, 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
(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
pp
, since controversial data exist at 2.0GeV; we find
mb. Using the dielectron channels, the
and
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.
Development of a fast pad readout system for the HADES shower detector Bałanda, A; Dębowski, M; Jaskuła, M ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/1998, Letnik:
417, Številka:
2
Journal Article
Recenzirano
The paper presents the readout system for the 18432 channels of the HADES shower detector. The readout system consists of an analog front-end ASIC for the readout of the pad multiwire chamber, a ...readout controller board, the so-called readout board for collection and digitization of the analog information from the ASIC and an optical link system for the data transfer. The readout system is designed to cope with event rate of 10
5
events/s and a data transfer rate of 1.9
Gbyte/s. Utilizing a multistage fast multiplexing system, the cost per channel is kept on the level of $5. Recent results from a test experiment confirm the intended performance of the readout system.
Results on pp, π
+
π
+
, and π
−
π
−
intensity interferometry are reported for collisions of Ar+KCl at 1.76
A
GeV beam energy, studied with the High Acceptance Di-Electron Spectrometer (HADES) at ...SIS18/GSI. The experimental correlation functions as a function of the relative momentum are compared to model calculations allowing the determination of the space-time extent of the corresponding emission sources. The ππ source radii are found significantly larger than the pp emission radius. The present radii do well complement the beam-energy dependences of Gaussian source radii of the collision system of size
A
+
A
≃ 40 + 40 . The pp source radius at fixed beam energy is found to increase linearly with the cube root of the number of participants. From this trend, a lower limit of the pp correlation radius is deduced.
.
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
and the K*(892)
0
/K
0
ratio of
are determined at the lowest energy so far (
i.e.
deep below the threshold for the corresponding production in nucleon-nucleon collisions,
MeV). The K*
0
/K
0
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
/K
0
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.
PANDA is a new universal detector for antiproton physics at the HESR facility at FAIR/GSI. The PANDA data acquisition system has to handle interaction rates of the order of 107/s and data rates of ...several 100 Gb/s. FPGA based compute nodes with multi-Gb/s bandwidth capability using the ATCA architecture are designed to handle tasks such as event building, feature extraction and high level trigger processing. Data connectivity is provided via optical links as well as multiple Gb Ethernet ports. The boards will support trigger algorithms such us pattern recognition for RICH detectors, EM shower analysis, fast tracking algorithms and global event characterization. Besides VHDL, high level C-like hardware description languages will be considered to implement the firmware.
The aim of the present analysis is to determine the relative production cross sections of the Λ(1405) and Σ(1385)
0
resonances in p+p collisions at E
kin
= 3.5 GeV measured with HADES. Upper and ...lower limits have been determined for the ratio
. The knowledge of this ratio is an essential input for the analysis of the decay Λ(1405)→Σ
±
π
∓
, where an unambiguous separation of the Λ(1405) and Σ(1385)
0
signals is not possible.
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.
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 pi0-Dalitz to the rho/omega! ...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.
Dielectron spectroscopy at 1-2 AGeV with HADES Spataro, S.; Agodi, C.; Belver, D. ...
European physical journal. A, Hadrons and nuclei (Print),
11/2008, Letnik:
38, Številka:
2
Journal Article, Conference Proceeding
Recenzirano
The HADES spectrometer at GSI (Darmstadt) is investigating the
e
+
e
-
pair production in p+p,
p
+
A
and
A
+
A
collisions. In this contribution we would like to highlight the physics motivations and ...the experiments performed so far, focusing mainly on the first results coming from
12
C +
12
C collisions at 1 and 2AGeV, and on preliminary results from
p
+
p
/
d
+
p
collisions at 1.25AGeV.
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