.
The centrality determination for Au + Au collisions at 1.23
A
GeV, as measured with HADES at the GSI-SIS18, is described. In order to extract collision geometry related quantities, such as the ...average impact parameter or number of participating nucleons, a Glauber Monte Carlo approach is employed. For the application of this model to collisions at this relatively low centre-of-mass energy of
s
NN
=
2
.
42
GeV special investigations were performed. As a result a well defined procedure to determine centrality classes for ongoing analyses of heavy-ion data is established.
Employing the Bonn–Gatchina partial wave analysis framework (PWA), we have analyzed HADES data of the reaction p(3.5 GeV)+p→pK+Λ. This reaction might contain information about the kaonic cluster ...“ppK−” (with quantum numbers JP=0− and total isospin I=1/2) via its decay into pΛ. Due to interference effects in our coherent description of the data, a hypothetical K‾NN (or, specifically “ppK−”) cluster signal need not necessarily show up as a pronounced feature (e.g. a peak) in an invariant mass spectrum like pΛ. Our PWA analysis includes a variety of resonant and non-resonant intermediate states and delivers a good description of our data (various angular distributions and two-hadron invariant mass spectra) without a contribution of a K‾NN cluster. At a confidence level of CLs=95% such a cluster cannot contribute more than 2–12% to the total cross section with a pK+Λ final state, which translates into a production cross-section between 0.7 μb and 4.2 μb, respectively. The range of the upper limit depends on the assumed cluster mass, width and production process.
.
The HADES data from p + Nb collisions at a center-of-mass energy of
GeV are analyzed employing a statistical hadronization model. The model can successfully describe the production yields of the ...identified hadrons
,
,
,
K
0
s
,
with parameters
MeV and
MeV, which fit well into the chemical freeze-out systematics found in heavy-ion collisions. In addition, we reanalyze our previous HADES data from Ar + KCl collisions at
GeV with an updated version of the model. We address equilibration in heavy-ion collisions by testing two aspects: the description of yields and the regularity of freeze-out parameters from a statistical model fit as a function of colliding energy and system size. Despite its success, the model fails to describe the observed
yields in both, p + Nb and Ar + KCl . Special emphasis is put on feed-down contributions from higher-lying resonance states as a possible explanation for the observed excess.
Low Gain Avalanche Detector (LGAD) technology has been used to design and construct prototypes of time-zero detector for experiments utilizing proton and pion beams with High Acceptance Di-Electron ...Spectrometer (HADES) at GSI Darmstadt, Germany. LGAD properties have been studied with proton beams at the COoler SYnchrotron facility in Jülich, Germany. We have demonstrated that systems based on a prototype LGAD operated at room temperature and equipped with leading-edge discriminators reach a time precision below 50 ps. The application in the HADES, experimental conditions, as well as the test results obtained with proton beams are presented.
Results on the production of the double strange cascade hyperon Ξ^{-} are reported for collisions of p(3.5 GeV)+Nb, studied with the High Acceptance Di-Electron Spectrometer (HADES) at SIS18 at GSI ...Helmholtzzentrum for Heavy-Ion Research, Darmstadt. For the first time, subthreshold Ξ^{-} production is observed in proton-nucleus interactions. Assuming a Ξ^{-} phase-space distribution similar to that of Λ hyperons, the production probability amounts to P_{Ξ^{-}}=2.0±0.4(stat)±0.3(norm)±0.6(syst)×10^{-4} resulting in a Ξ^{-}/(Λ+Σ^{0}) ratio of P_{Ξ^{-}}/P_{Λ+Σ^{0}}=1.2±0.3(stat)±0.4(syst)×10^{-2}. Available model predictions are significantly lower than the measured Ξ^{-} yield.
We report measurements of electron pair production in elementary p+p and d+p reactions at 1.25 GeV/u with the HADES spectrometer. For the first time, the electron pairs were reconstructed for n+p ...reactions by detecting the proton spectator from the deuteron breakup. We find that the yield of electron pairs with invariant mass Me+e−>0.15 GeV/c2 is about an order of magnitude larger in n+p reactions as compared to p+p. A comparison to model calculations demonstrates that the production mechanism is not sufficiently described yet. The electron pair spectra measured in C+C reactions are compatible with a superposition of elementary n+p and p+p collisions, leaving little room for additional electron pair sources in such light collision systems.
HADES is a high acceptance di-electron spectrometer operating at SIS18, GSI, Germany aimed at study of hadron-proton, hadron-nucleus and nucleus-nucleus collisions at 1-4 AGeV beam energies. The new ...electromagnetic calorimeter (ECal) was added to the experimental setup in order to measure γ-quanta and thus extend its capabilities in study of π0-, η-mesons, production of neutral hyperons and to improve electron-to-hadron separation for the partcles with momenta p > 300 MeV/c. The first data taking with the ECal detector was carried out in March 2019 when Ag+Ag collisions at 1.23 AGeV and 1.58 AGeV beam energies were studied. The methods of reconstruction of the γγ invariant mass spectra from these data are discussed. The analysis includes several steps: calibration of each module of the ECal detector, identification of γ-quanta, reconstruction of γγ invariant mass spectra and subtraction of combinatorial background. The obtained results show experimental capabilities of the new detector and, after efficiency corrections, will allow to normalize yields of other particles.
HADES (High Acceptance Di-Electron Spectrometer) is located at the GSI (Helmholtzzentrum für Schwerionenforschung) Darmstadt. It is an experiment focused on the study of the hot and dense nuclear ...matter mainly via the detection of the di-lepton pairs. Electromagnetic CALorimeter (ECAL) was recently added to the HADES setup. This new subdetector allows measuring of photons from the decay of neutral mesons and resonances. It also allows to discriminate between electrons and pions in the high-momenta region over 400 MeV/c. ECAL follows same hexagonal geometry as HADES, i.e. it consists of six sectors in azimuth. The first four sectors were finished and commissioned in 2018. The first experiment with ECAL included in HADES setup took place on March 2019, investigating the Ag+Ag reaction at beam energy of 1.65 A GeV. During the commissioning, several issues popped up and they were addressed. The issues and their solution will be described in the article.
HADES is a large acceptance spectrometer operating at SIS18, GSI, Germany. It is aimed at exploration of QCD phase diagram at the ion beam energies of 1-2 AGeV in the region of high baryonic ...densities. The new segmented electromagnetic calorimeter (ECal) was built to extend experimental opportunities of the HADES detector. The electromagnetic calorimeter will allow to study new reaction channels involving the production of neutral mesons and neu-tral resonances in elementary and heavy-ion reactions via detection of their two photon decay. An additional advantage of such a device is the resulting improvement of the electron-to-pion separation at large momenta. The detector is based on 978 Cherenkov lead glass modules divided into 6 sectors, and it covers forward angles of 12° < θ < 45° and almost full azimuthal angle. Currently four out of six sectors planned are assembled in the experimental area. The first raw beam data obtained with the ECal detector in Ag+Ag reactions at 1.65 AGeV beam are presented.
In-Beam Diamond Start Detectors Ciobanu, M.; Berdermann, E.; Herrmann, N. ...
IEEE transactions on nuclear science,
2011-Aug., 2011-08-00, 20110801, Volume:
58, Issue:
4
Journal Article
Peer reviewed
This paper describes operation principles and the in-beam performance of Start Detector (SD) assemblies consisting of Diamond Detectors (DDs) grown by Chemical Vapour Deposition (CVD) and Front End ...Electronics (FEE) which have been designed for and used in various nuclear physics experiments at GSI Helmholtz Center for Heavy Ion Research in Darmstadt. In parallel to the FEE design we have performed extensive calculations to model the dependence of the signal-to-noise ratio (S/N) and the time resolution σ t on various quantities such as the collected charge Q col , the detector capacitance C D , the temperature T, and finally the noise contribution and bandwidth of the amplifier. In combination with the new FEEs (including an application-specific integrated circuit, ASIC) we have tested both polycrystalline and single-crystal diamonds of various sizes and thicknesses with relativisticion beams ranging from protons to heaviest ions. For heavy ions all setups deliver time resolutions σ t <; 60 ps. In case of protons the small primary detector signals require single crystals as material and more elaborated designs like segmentation of the detector area and the increase of the amplifier input impedance. The best time resolution obtained for relativistic pro tons was σ t = 117 ps.
PDF
