High-precision measurements of flow coefficients
v
n
(
n
=
1
-
4
) for protons, deuterons and tritons relative to the first-order spectator plane have been performed in Au+Au collisions at
s
NN
=
2.4
... GeV with the High-Acceptance Di-Electron Spectrometer (HADES) at the SIS18/GSI. Flow coefficients are studied as a function of transverse momentum
p
t
and rapidity
y
cm
over a large region of phase-space and for several classes of collision centrality. A clear mass hierarchy, as expected by relativistic hydrodynamics, is found for the slope of
v
1
,
d
v
1
/
d
y
′
|
y
′
=
0
where
y
′
is the scaled rapidity, and for
v
2
at mid-rapidity. Scaling with the number of nucleons is observed for the
p
t
dependence of
v
2
and
v
4
at mid-rapidity, which is indicative for nuclear coalescence as the main process responsible for light nuclei formation.
v
2
is found to scale with the initial eccentricity
⟨
ϵ
2
⟩
, while
v
4
scales with
⟨
ϵ
2
⟩
2
and
⟨
ϵ
4
⟩
. The multi-differential high-precision data on
v
1
,
v
2
,
v
3
, and
v
4
provides important constraints on the equation-of-state of compressed baryonic matter.
We investigate identical pion HBT intensity interferometry in central Au+Au collisions at 1.23A GeV. High-statistics π−π− and π+π+ data are measured with HADES at SIS18/GSI. The radius parameters, ...derived from the correlation function depending on relative momenta in the longitudinally comoving system and parametrized as three-dimensional Gaussian distribution, are studied as function of transverse momentum. A substantial charge-sign difference of the source radii is found, particularly pronounced at low transverse momentum. The extracted source parameters agree well with a smooth extrapolation of the center-of-mass energy dependence established at higher energies, extending the corresponding excitation functions down towards a very low energy.
.
This paper summarises a comprehensive Monte Carlo simulation study for precision resonance energy scan measurements. Apart from the proof of principle for natural width and line shape measurements ...of very narrow resonances with PANDA, the achievable sensitivities are quantified for the concrete example of the charmonium-like
X
(3872) state discussed to be exotic, and for a larger parameter space of various assumed signal cross-sections, input widths and luminosity combinations. PANDA is the only experiment that will be able to perform precision resonance energy scans of such narrow states with quantum numbers of spin and parities that differ from
J
P
C
=
1
-
-
.
In this letter we report the first multi-differential measurement of correlated pion-proton pairs from 2 billion Au+Au collisions at sNN=2.42 GeV collected with HADES. In this energy regime the ...population of Δ(1232) resonances plays an important role in the way energy is distributed between intrinsic excitation energy and kinetic energy of the hadrons in the fireball. The triple differential d3N/dMπ±pdpTdy distributions of correlated π±p pairs have been determined by subtracting the πp combinatorial background using an iterative method. The invariant-mass distributions in the Δ(1232) mass region show strong deviations from a Breit-Wigner function with vacuum width and mass. The yield of correlated pion-proton pairs exhibits a complex isospin, rapidity and transverse-momentum dependence. In the invariant mass range 1.1<Minv(GeV/c2)<1.4, the yield is found to be similar for π+p and π−p pairs, and to follow a power law 〈Apart〉α, where 〈Apart〉 is the mean number of participating nucleons. The exponent α depends strongly on the pair transverse momentum (pT) while its pT-integrated and charge-averaged value is α=1.5±0.08st±0.2sy.
Many QCD based and phenomenological models predict changes of hadron properties in a strongly interacting environment. The results of these models differ significantly and the experimental ...determination of hadron properties in nuclear matter is essential. In this paper we present a review of selected physics results obtained at GSI Helmholtzzentrum fur Schwerionenforschung GmbH by HADES (High-Acceptance Di-Electron Spectrometer). The e super(+)e super(-) pair emission measured for proton and heavy-ion induced collisions is reported together with results on strangeness production. The future HADES activities at the planned FAIR facility are also discussed.
In 2014 the HADES collaboration performed two successful physics production runs with secondary pion beams. Since secondary pion beams are strongly defocussed in position and momentum, two fast ...tracking stations were installed along the pion beam chicane following the pion production target providing the momentum measurement of each individual pion. The momentum is reconstructed using the position information of every hit detected by the tracking stations and the beam optics transport calculation with a resolution below 0.5% playing an important role in terms of the exclusive analysis of investigated reactions.
Both tracking stations consist of a double-sided silicon strip sensor with a large active area (10×10cm2). To guarantee fast tracking, the sensors are read out with the n-XYTER ASIC chip. Due to its self-triggering architecture and local storage capability, the chip enables on-line tracking at high rates (dN/dt>106part/s). The TRB3 read out board on which the trigger logic is implemented integrates the system into the HADES DAQ.
In this report we are showing the results obtained during the calibration experiment with a monochromatic proton beam set at seven different momenta centred around 2.68GeV/c. Also the excellent performance achieved during the production campaign with a pion beam are presented.
Hadron production (
π
±
, proton,
Λ
,
K
S
0
,
K
±
) in
π
-
+
C
and
π
-
+
W
collisions is investigated at an incident pion beam momentum of
1.7
GeV
/
c
. This comprehensive set of data measured with ...HADES at SIS18/GSI significantly extends the existing world data on hadron production in pion induced reactions and provides a new reference for models that are commonly used for the interpretation of heavy-ion collisions. The measured inclusive differential production cross-sections are compared with state-of-the-art transport model (GiBUU, SMASH) calculations. The (semi-) exclusive channel
π
-
+
A
→
Λ
+
K
S
0
+
X
, in which the kinematics of the strange hadrons are correlated, is also investigated and compared to a model calculation. Agreement and remaining tensions between data and the current version of the considered transport models are discussed.
A feasibility study has been performed in order to investigate the performance of the HADES detector to measure the electromagnetic decays of the hyperon resonances
Σ
(
1385
)
0
,
Λ
(
1405
)
and
...Λ
(
1520
)
as well as the production of double strange baryon systems
Ξ
-
and
Λ
Λ
in p + p reactions at a beam kinetic energy of
4.5
GeV
. The existing HADES detector will be upgraded by a new Forward Detector, which extends the detector acceptance into a range of polar angles that plays a crucial role for these investigations. The analysis of each channel is preceded by a consideration of the production cross-sections. Afterwards the expected signal count rates using a target consisting of either liquid hydrogen or polyethylene are summarized.
The High Acceptance DiElectron Spectrometer HADES 1 is installed at the Helmholtzzentrum fur Schwerionenforschung (GSI) accelerator facility in Darmstadt. It investigates dielectron emission and ...strangeness production in the 1-3 AGeV regime. A recent experiment series focusses on medium-modifications of light vector mesons in cold nuclear matter. In two runs, p+p and p+Nb reactions were investigated at 3.5 GeV beam energy; about 9 times 10 super(9) events have been registered. In contrast to other experiments the high acceptance of the HADES allows for a detailed analysis of electron pairs with low momenta relative to nuclear matter, where modifications of the spectral functions of vector mesons are predicted to be most prominent. Comparing these low momentum electron pairs to the reference measurement in the elementary p+p reaction, we find in fact a strong modification of the spectral distribution in the whole vector meson region.
Recent results obtained with the HADES experimental set-up at GSI are presented with a focus on dielectron production and strangeness in pp and quasi-free np reactions. Perspectives related to the ...very recent experiment using the pion beam at GSI are also discussed.
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