-
The HADES Collaboration,
S. Spataro,
G. Agakishiev,
C. Agodi,
A. Balanda,
G. Bellia,
D. Belver,
A. Belyaev,
A. Blanco,
M. Böhmer, [......],
I. Veretenkin,
V. Wagner,
H. Wen,
M. Wisniowski,
T. Wojcik,
J. Wüstenfeld,
S. Yurevich,
Y. Zanevsky,
P. Zhou,
P. Zumbruch
[show abstract]
[hide abstract]
ABSTRACT: 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 12C + 12C collisions at 1 and 2AGeV, and on preliminary results from p+p/d+p collisions at 1.25AGeV.
European Physical Journal A 04/2012; 38(2):163-166. · 2.19 Impact Factor
-
M. Sudol,
G. Agakishiev,
C. Agodi,
A. Balanda,
G. Bellia,
D. Belver,
A. Belyaev,
J. Bielcik,
A. Blanco,
A. Bortolotti, [......],
H. Tsertos,
V. Wagner,
M. Weber,
M. Wisniowski,
T. Wojcik,
J. Wüstenfeld,
S. Yurevich,
Y. Zanevsky,
P. Zhou,
P. Zumbruch
[show abstract]
[hide abstract]
ABSTRACT: HADES is a secondary generation experiment operated at GSI Darmstadt with the main goal to study dielectron production in
proton, pion and heavy ion induced reactions. The first part of the HADES mission is to reinvestigate the puzzling pair excess
measured by the DLS collaboration in C + C and Ca + Ca collisions at 1 AGeV. For this purpose dedicated measurements with the C + C system at 1 and 2 AGeV were performed. The pair excess above a cocktail of free hadronic decays has been extracted and compared to the one measured
by DLS. Furthermore, the excess is confronted with predictions of various model calculations.
European Physical Journal C 04/2012; 62(1):81-84. · 3.63 Impact Factor
-
The HADES Collaboration,
G. Agakichiev,
C. Agodi,
H. Alvarez-Pol,
E. Atkin,
E. Badura,
A. Balanda,
A. Bassi,
R. Bassini,
G. Bellia, [......],
M. Wisniowski,
T. Wojcik,
J. Wüstenfeld,
S. Yurevich,
Y. V. Zanevsky,
K. Zeitelhack,
A. Zentek,
P. Zhou,
D. Zovinec,
P. Zumbruch
[show abstract]
[hide abstract]
ABSTRACT: HADES is a versatile magnetic spectrometer aimed at studying dielectron production in pion, proton and heavy-ion-induced collisions.
Its main features include a ring imaging gas Cherenkov detector for electron-hadron discrimination, a tracking system consisting
of a set of 6 superconducting coils producing a toroidal field and drift chambers and a multiplicity and electron trigger
array for additional electron-hadron discrimination and event characterization. A two-stage trigger system enhances events
containing electrons. The physics program is focused on the investigation of hadron properties in nuclei and in the hot and
dense hadronic matter. The detector system is characterized by an 85% azimuthal coverage over a polar angle interval from
18° to 85° , a single electron efficiency of 50% and a vector meson mass resolution of 2.5%. Identification of pions, kaons and protons
is achieved combining time-of-flight and energy loss measurements over a large momentum range ( 0.1 < p < 1.0 GeV/c . This paper describes the main features and the performance of the detector system.
European Physical Journal A 04/2012; 41(2):243-277. · 2.19 Impact Factor
-
HADES Collaboration,
P. K. Kurilkin,
G. Agakishiev,
A. Balanda,
D. Belver,
A. Belyaev,
A Blanco,
M. Böhmer,
J. L. Boyard,
P. Cabanelas, [......],
P. Tlusty,
M. Traxler,
R. Trebacz,
H. Tsertos,
T. Vasiliev,
V. Wagner,
M Weber,
J. Wüstenfeld,
S. Yurevich,
Y. Zanevsky
[show abstract]
[hide abstract]
ABSTRACT: First results of the differential cross section in dp elastic scattering at
1.25 GeV/u measured with the HADES over a large angular range are reported. The
obtained data corresponds to large transverse momenta, where a high sensitivity
to the two-nucleon and three-nucleon short-range correlations is expected.
02/2011;
-
G. Agakishiev,
A. Balanda,
B. Bannier,
R. Bassini,
D. Belver,
A. V. Belyaev,
A Blanco,
M. Böhmer,
J. L. Boyard,
P. Cabanelas, [......],
H. Tsertos,
V. Wagner,
M Weber,
M. Wisniowski,
T. Wojcik,
J. Wüstenfel,
S. Yurevich,
Y. V. Zanevsky,
P Zhou,
P. Zumbruch
[show abstract]
[hide abstract]
ABSTRACT: We present the transverse momentum spectra and rapidity distributions of $\pi^{-}$ and K$^0_S$ in Ar+KCl reactions at a beam kinetic energy of 1.756 A GeV measured with the spectrometer HADES. The reconstructed K$^0_S$ sample is characterized by good event statistics for a wide range in momentum and rapidity. We compare the experimental $\pi^{-}$ and K$^0_S$ distributions to predictions by the IQMD model. The model calculations show that K$^0_S$ at low tranverse momenta constitute a particularly well suited tool to investigate the kaon in-medium potential. Our K$^0_S$ data suggest a strong repulsive in-medium K$^0$ potential of about 40 MeV strength. Comment: 10 pages, 10 figures, accepted by Phys. Rev. C
04/2010;
-
G. Agakishiev,
A. Balanda,
R. Bassini,
D. Belver,
A. V. Belyaev,
A Blanco,
M. Böhmer,
J. L. Boyard,
P. Braun-Munzinger,
P. Cabanelas, [......],
V. Wagner,
M Weber,
C. Wendisch,
M. Wisniowski,
T. Wojcik,
J. Wüstenfeld,
S. Yurevich,
Y. V. Zanevsky,
P Zhou,
P. Zumbruch
[show abstract]
[hide abstract]
ABSTRACT: Results on $\Lambda$p femtoscopy are reported at the lowest energy so far. At a beam energy of 1.76A~GeV, the reaction Ar+KCl was studied with the High Acceptance Di-Electron Spectrometer (HADES) at SIS18/GSI. A high-statistics and high-purity $\Lambda$ sample was collected, allowing for the investigation of $\Lambda$ p correlations at small relative momenta. The experimental correlation function is compared to corresponding model calculations allowing the determination of the space-time extent of the $\Lambda$p emission source. The $\Lambda$p source radius is found slightly smaller than the pp correlation radius for a similar collis ion system. The present $\Lambda$p radius is significantly smaller than that found for Au+Au/Pb+Pb collisio ns in the AGS, SPS and RHIC energy domains, but larger than that observed for electroproduction from He. Taking into account all available data, we find the $\Lambda$p source radius to increase almost linearly with the number of participants to the power of one-third. Comment: 5 pages, 3 figures, submitted to Phys. Rev. C
04/2010;
-
The HADES Collaboration,
T. Galatyuk,
G. Agakishiev,
A. Balanda,
D. Belver,
A. V. Belyaev,
A Blanco,
M. Böhmer,
J. L. Boyard,
P. Braun-Munzinger, [......],
R. Trebacz,
H. Tsertos,
V. Wagner,
M Weber,
M. Wisniowski,
T. Wojcik,
J. Wüstenfeld,
S. Yurevich,
Y. V. Zanevsky,
P Zhou
[show abstract]
[hide abstract]
ABSTRACT: Systematic investigations of dilepton production are performed at the SIS accelerator of GSI with the HADES spectrometer. The goal of this program is a detailed understanding of di-electron emission from hadronic systems at moderate temperatures and densities. New results obtained in HADES experiments focussing on electron pair production in elementary collisions are reported here. They pave the way to a better understanding of the origin of the so-called excess pairs earlier on observed in heavy-ion collisions by the DLS collaboration and lately confirmed in two measurements of the HADES collaboration using C+C and Ar+KCl collisions. Results of these studies are discussed. Comment: 8 pages, 5 figures, To appear in the proceedings of 5th International Workshop on Critical Point and Onset of Deconfinement (CPOD), Brookhaven, Upton, New York, 8-12 Jun 2009
11/2009;
-
K. Piasecki,
T. Matulewicz,
N. Yahlali,
H Delagrange, J Díaz,
D G D'Enterria,
F. Fernández,
A. Kugler,
H Löhner,
G Martínez García,
R. W. Ostendorf,
Y Schutz,
P Tlustý,
R. Turrisi,
V. Wagner,
H. W. Wilschut
[show abstract]
[hide abstract]
ABSTRACT: Differential cross sections of neutral pions emitted in 181Ta + 197Au collisions at a beam energy of 39.5A MeV have been measured with the photon spectrometer TAPS. The kinetic energy and transverse momentum spectra of neutral pions cannot be properly described in the framework of the thermal model, nor when the reabsorption of pions is accounted for in a phenomenological model. However, high energy and high momentum tails of the pion spectra can be well fitted through thermal distributions with unexpectedly soft temperature parameters below 10 MeV. Comment: 16 pages (double-spaced), 5 figures; corrections after referee's comments and suggestions
09/2009;
-
G Agakishiev,
A Balanda,
R Bassini,
D Belver,
A V Belyaev,
A Blanco,
M Böhmer,
J L Boyard,
P Braun-Munzinger,
P Cabanelas, [......],
H Tsertos,
V Wagner,
M Weber,
M Wisniowski,
T Wojcik,
J Wüstenfeld,
S Yurevich,
Y V Zanevsky,
P Zhou,
P Zumbruch
[show abstract]
[hide abstract]
ABSTRACT: We report first results on a deep subthreshold production of the doubly strange hyperon Xi;{-} in a heavy-ion reaction. At a beam energy of 1.76A GeV the reaction Ar + KCl was studied with the High Acceptance Di-Electron Spectrometer at SIS18/GSI. A high-statistics and high-purity Lambda sample was collected, allowing for the investigation of the decay channel Xi;{-} --> Lambdapi;{-}. The deduced Xi;{-}/(Lambda + Sigma;{0}) production ratio of (5.6 +/- 1.2_{-1.7};{+1.8}) x 10;{-3} is significantly larger than available model predictions.
Physical Review Letters 09/2009; 103(13):132301. · 7.37 Impact Factor
-
G. Agakishiev,
A. Balanda,
R. Bassini,
D. Belver,
A. V. Belyaev,
A Blanco,
M. Böhmer,
J. L. Boyard,
P. Braun-Munzinger,
P. Cabanelas, [......],
R. Trebacz,
H. Tsertos,
V. Wagner,
M Weber,
M. Wisniowski,
T. Wojcik,
J. Wüstenfeld,
S. Yurevich,
Y. V. Zanevsky,
P Zhou
[show abstract]
[hide abstract]
ABSTRACT: We report first results on a deep sub-threshold production of the doubly strange hyperon $\Xi^-$ in a heavy-ion reaction. At a beam energy of 1.76A GeV the reaction Ar+KCl was studied with the High Acceptance Di-Electron Spectrometer (HADES) at SIS18/GSI. A high-statistics and high-purity $\Lambda$ sample was collected, allowing for the investigation of the decay channel $\Xi^- \to \Lambda \pi^-$. The deduced $\Xi^-/(\Lambda+\Sigma^0)$ production ratio of $(5.6 \pm 1.2 ^{+1.8}_{-1.7})\cdot 10^{-3}$ is significantly larger than available model predictions. Comment: 4 pages, including 4 figures
07/2009;
-
J Markert,
G Agakishiev,
C Agodi,
A Balanda,
G Bellia,
D Belver,
A Belyaev,
A Blanco,
M Böhmer,
J L Boyard, [......],
H Tsertos,
I Veretenkin,
V Wagner,
H Wen,
M Wisniowski,
T Wojcik,
J Wüstenfeld,
S Yurevich,
Y Zanevsky,
P Zumbruch
[show abstract]
[hide abstract]
ABSTRACT: We report on a measurement of electron pair production in 12C+12C collisions at an incident energy of 2 GeV per nucleon with the HADES spectrometer. The measured pair production probabilities span over five orders of magnitude from the π0-Dalitz to the ρ/ω invariant-mass region. Dalitz decays of π0 and η account for all the yield up to 0.15 GeV/c2, but for only about 50% above this mass. The excess yield is in agreement with the former DLS result if one assumes that it scales with beam energy like pion production. A preliminary analysis of 12C+12C collisions at an incident energy of 1 A GeV, measured with the HADES detector, supports this scenario.
Journal of Physics G Nuclear and Particle Physics 07/2007; 34(8):S1041. · 4.18 Impact Factor
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G Agakichiev,
C Agodi,
H Alvarez-Pol,
A Bałanda,
D Bertini,
J Bielcik,
G Bellia,
M Böhmer,
H Bokemeyer,
J L Boyard, [......],
A Vázquez,
V Wagner,
W Waluś,
M Wiśniowski,
T Wójcik,
J Wüstenfeld,
Y Zanevsky,
K Zeitelhack,
D Zovinec,
P Zumbruch
[show abstract]
[hide abstract]
ABSTRACT: The invariant-mass spectrum of e+e- pairs produced in 12C+12C collisions at an incident energy of 2 GeV per nucleon has been measured for the first time. The measured pair production probabilities span over 5 orders of magnitude from the pi(0)-Dalitz to the rho/omega invariant-mass region. Dalitz decays of pi(0) and eta account for all the yield up to 0.15 GeV/c(2), but for only about 50% above this mass. A comparison with model calculations shows that the excess pair yield is likely due to baryon-resonance and vector-meson decays. Transport calculations based on vacuum spectral functions fail, however, to describe the entire mass region.
Physical Review Letters 03/2007; 98(5):052302. · 7.37 Impact Factor
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I. Fröhlich,
G. Agakishiev,
C. Agodi,
A. Balanda,
G. Bellia,
D. Belver,
A. Belyaev,
A. Blanco,
M. Böhmer,
J. L. Boyard, [......],
R. Trebacz,
H. Tsertos,
I. Veretenkin,
V. Wagner,
H. Wen,
M. Wisniowski,
T. Wojcik,
J. Wüstenfeld,
Y. Zanevsky,
P. Zumbruch
[show abstract]
[hide abstract]
ABSTRACT: e
+
e
− production was studied using the High Acceptance DiElectron Spectrometer (HADES). In pp collisions at 2.2 GeV kinetic beam energy, the exclusive η production and the Dalitz decay η → γe
+
e
− have been reconstructed. The electromagnetic form factor of the latter decay was found to be in good agreement with the existing
theoretical predictions. In addition, an inclusive e
+
e
− invariant-mass spectrum from the 12C + 12C reaction at 2 AGeV is presented and compared with a simplified thermal model.
12/2006: pages 541-545;
-
[show abstract]
[hide abstract]
ABSTRACT: In this paper we consider a coupled system of elastic and rigid bodies. It can be mathematically formulated as a coupled system of ordinary and partial differential equations, often written in its weak form. The discretisation is performed by a Galerkin-type ansatz in connection with a finite element approach or known eigenfunctions. Here, we demonstrate instead the use of a recently published Galerkin-wavelet method and its application to obtain a reasonable small number of elastic modes.
ZAMM Journal of applied mathematics and mechanics: Zeitschrift für angewandte Mathematik und Mechanik 09/2003; 83(10):677 - 689. · 0.86 Impact Factor
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M J van Goethem,
L Aphecetche,
J C S Bacelar,
H Delagrange, J Díaz,
D d'Enterria,
M Hoefman,
R Holzmann,
H Huisman,
N Kalantar-Nayestanaki, [......],
J G Messchendorp,
R W Ostendorf,
S Schadmand,
R H Siemssen,
R S Simon,
Y Schutz,
R Turrisi,
M Volkerts,
V Wagner,
H W Wilschut
[show abstract]
[hide abstract]
ABSTRACT: Photon energy spectra up to the kinematic limit have been measured in 190 MeV proton reactions with light and heavy nuclei to investigate the influence of the multiple-scattering process on the photon production. Relative to the predictions of models based on a quasifree production mechanism, a strong suppression of bremsstrahlung is observed in the low-energy region of the photon spectrum. We attribute this effect to the interference of photon amplitudes due to multiple scattering of nucleons in the nuclear medium.
Physical Review Letters 04/2002; 88(12):122302. · 7.37 Impact Factor
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E Sauvan,
F M Marqués,
H W Wilschut,
N A Orr,
J C Angélique,
C Borcea,
W N Catford,
N M Clarke,
P Descouvemont, J Díaz, [......],
E Lienard,
H Löhner,
W Mittig,
R W Ostendorf,
S Pietri,
P Roussel-Chomaz,
M G Saint Laurent,
H Savajols,
V Wagner,
N Yahlali
[show abstract]
[hide abstract]
ABSTRACT: Radiative capture of protons is investigated as a probe of clustering in nuclei far from stability. The first such measurement on a halo nucleus is reported here for the reaction 6He(p,gamma) at 40 MeV. Capture into 7Li is observed as the strongest channel. In addition, events have been recorded that may be described by quasifree capture on a halo neutron, the alpha core, and 5He. The possibility of describing such events by capture into the continuum of 7Li is also discussed.
Physical Review Letters 08/2001; 87(4):042501. · 7.37 Impact Factor
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D G D'Enterria,
L Aphecetche,
A. Chbihi,
H Delagrange, J Díaz,
M. J. van Goethem,
M. Hoefman,
A. Kugler,
H Löhner,
G Martínez, [......],
S. Schadmand,
Y Schutz,
R. H. Siemssen,
D. Stracener,
P. Tlusty,
R. Turrisi,
M. Volkerts,
V. Wagner,
H. Wilschut,
N. Yahlali
[show abstract]
[hide abstract]
ABSTRACT: The production of nuclear bremsstrahlung photons (E$_{\gamma}>$ 30 MeV) has been studied in inclusive and exclusive measurements in four heavy-ion reactions at 60{\it A} MeV. The measured photon spectra, angular distributions and multiplicities indicate that a significant part of the hard-photons are emitted in secondary nucleon-nucleon collisions from a thermally equilibrated system. The observation of the thermal component in multi-fragment $^{36}$Ar+$^{197}$Au reactions suggests that the breakup of the thermalized source produced in this system occurs on a rather long time-scale.
01/2001;
-
D G D'Enterria,
L Aphecetche,
A. Chbihi,
H Delagrange, J Díaz,
M. J. van Goethem,
M. Hoefman,
H. Huisman,
A. Kugler,
H. Loehner, [......],
S. Schadmand,
Y Schutz,
R. Siemssen,
D. Stracener,
P. Tlusty,
R. Turrisi,
M. Volkerts,
V. Wagner,
H. Wilschut,
N. Yahlali
[show abstract]
[hide abstract]
ABSTRACT: Inclusive and exclusive hard-photon (E$_\gamma >$ 30 MeV) production in five different heavy-ion reactions ($^{36}$Ar+$^{197}$Au, $^{107}$Ag, $^{58}$Ni, $^{12}$C at 60{\it A} MeV and $^{129}$Xe+$^{120}$Sn at 50{\it A} MeV) has been studied coupling the TAPS photon spectrometer with several charged-particle multidetectors covering more than 80% of 4$\pi$. The measured spectra, slope parameters and source velocities as well as their target-dependence, confirm the existence of thermal bremsstrahlung emission from secondary nucleon-nucleon collisions that accounts for roughly 20% of the total hard-photon yield. The thermal slopes are a direct measure of the temperature of the excited nuclear systems produced during the reaction.
08/2000;
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G. Martínez, J. Díaz,
M. Franke,
S. Hlavá,
R. Holzmann,
P. Lautridou,
F. Lefèvre,
H. Löhner,
A. Marín,
M. Marqués, [......],
J. H. G. van Pol,
J. Québert,
P. Roussel-Chomaz,
Y. Schutz,
A. Schubert,
R. H. Siemssen,
R. S. Simon,
Z. Sujkowski,
V. Wagner,
H. W. Wilschut
[show abstract]
[hide abstract]
ABSTRACT: Hard photon production was investigated in the system
68Kr+natNi at 60 A MeV for a wide range of impact
parameters. The parameters characteristic of hard photon emission such
as source velocities, angular distributions and energy spectra were
studied from peripheral to central collisions. The energy spectrum is
seen to be strongly dependent on the centrality of the collision
reflecting both a static and dynamic momentum distribution of the
nucleons inside the collision zone.
Physics Letters B 07/1994; 334:23-28. · 3.95 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: 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 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 12C 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.
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 602(3):788-791. · 1.21 Impact Factor
