We study the production of Σ±π∓pK+ 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∓pK+ 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 HADES tracking system Müntz, C.; Markert, J.; Agakichiev, G. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2004, Letnik:
535, Številka:
1
Journal Article
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The HADES dielectron spectrometer has recently launched its physics program at the heavy ion synchrotron SIS at GSI Darmstadt. The spectroscopy of vector mesons in heavy ion collisions via their ...dielectron decay channel makes great demands on the HADES tracking system regarding acceptance and spatial resolution. The tracking system is formed out of 24 low-mass, trapezoidal multi-layer drift chambers providing about
30
m
2
of active area. Low multiple scattering in the in total four planes of drift chambers before and after the magnetic field is ensured by using helium-based gas mixtures and aluminum cathode and field wires. First in-beam performance results are contrasted with expectations from simulations. Emphasis is placed on the energy loss information, exploring its relevance regarding track recognition.
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.
.
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.
Results on $\Lambda$ hyperon production 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. The transverse mass distributions in rapidity bins are well described by Boltzmann shapes with a maximum inverse slope parameter of about $90\,$MeV at a rapidity of $y=1.0$, i.e. slightly below the center-of-mass rapidity for nucleon-nucleon collisions, $y_{cm}=1.12$. The rapidity density decreases monotonically with increasing rapidity within a rapidity window ranging from 0.3 to 1.3. The $\Lambda$ phase-space distribution is compared with results of other experiments and with predictions of two transport approaches which are available publicly. None of the present versions of the employed models is able to fully reproduce the experimental distributions, i.e. in absolute yield and in shape. Presumably, this finding results from an insufficient modelling in the transport models of the elementary processes being relevant for $\Lambda$ production, rescattering and absorption. The present high-statistics data allow for a genuine two-dimensional investigation as a function of phase space of the self-analyzing $\Lambda$ polarization in the weak decay $\Lambda\rightarrow p \pi^-$. Finite negative values of the polarization in the order of $5-20\,%$ are observed over the entire phase space studied. The absolute value of the polarization increases almost linearly with increasing transverse momentum for $p_t>300\,$MeV/c and increases with decreasing rapidity for $y < 0.8$.
One of the main goals of the HADES experiment is to achieve a detailed understanding of dielectron emission from hadronic systems at moderate bombarding energies. Results obtained on electron pair ...production in elementary
N+
N collisions pave the way to a better understanding of the origin of the pair excess seen in heavy-ion collisions. This puzzling excess, reported first by the former DLS experiment, is now being investigated systematically by HADES.
The production of e+e- pairs in C+C collisions at 1 GeV/u was investigated with the HADES experiment at GSI, Darmstadt. In the invariant-mass region \( 0.15\: GeV/c^{2} \leq M_{ee} \leq 0.5\: ...GeV/c^{2}\) the measured pair yield shows a strong excess above the contribution expected from hadron decays after freeze-out. The data are in good agreement with the results of the former DLS experiment for the same system and energy.
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