The flow of light charged particles from the Au+Au reaction at 400 AMeV measured with the KRATTA detector is presented. The results are compared with the FOPI data

Brzychczyk, Janusz

Kupny, Sebastian

Pawłowski, P.

Łukasik, J.

EPJ Web of Conferences

English

Jagiellonian Univeristy Repository

Charged-particle flow measured with theKRATTA detector in the ASY-EOSexperimentS. Kupny1, J. Brzychczyk1, J. Lukasik2, P. Pawlowski1 andthe ASY-EOS Collaboration1 Institute of Physics, Jagiellonian University, Kraków, Poland2 Institute of Nuclear Physics, PAN, Kraków, PolandAbstractThe flow of light charged particles from the Au+Au reaction at400 AMeV measured with the KRATTA detector is presented. Theresults are compared with the FOPI data.The KRATTA detector (Krakow Triple Telescope Array) [1] has beenused to measure the energy, emission angles and isotopic composition of lightcharged reaction products in the ASY-EOS experiment at GSI laboratory [2].This versatile, low threshold, broad energy range system consists of 38independent modules which can be arranged in an arbitrary configuration -Fig. 1 presents the used 7×5 array. A single module, covering actively about4.5 msr of the solid angle at the optimal distance of 40 cm from the target,consists of three identical, 500 μm thick, large area photodiodes, used alsofor direct detection, and of two CsI(1500 ppm Tl) crystals of 2.5 and 12.5cm length, respectively. The presented results come from the analysis of theexperimental data for Au+Au at 400 MeV/nucleon incident energy.Signals from the KRATTA modules have been stored for the off-lineanalysis using the 100 MHz V1724 CAEN digitizers. The pulse shape anal-ysis allowed to decompose the complex signals from the middle photodiode(Single Chip Telescope [3] segment, SCT) into the ionization and scintil-DOI: 10.1051/C© Owned by the authors, published by EDP Sciences/01010 2015)201epjconfEPJ Web of Conferences01010588,88, 2015- SIF(	 !Article available at http://www.epj-conferences.org or http://dx.doi.org/10.1051/epjconf/20158801010Figure 1: KRATTA detector during theASY-EOS experiment (May 2011). Figure 2: Acceptance for protons andangular range used for comparisons withFOPI.lation components and to obtain a satisfactory isotopic resolution with asingle readout channel.Scintillation signal of SCT  [channels]0 2000 4000 6000 8000 10000 12000 14000 16000 18000 20000Ionization signal of SCT  [channels]05001000150020002500300035004000H1,2,3 He3,4,6Li6,7,8,9Be7,9,10B10,11,12,13C12,13N15Figure 3: Identification spectrum for theSCT segment.PD2 Scintillation [channels]0 2000 4000 6000 8000 10000 12000PD1 Scintillation [channels]020004000600080001000012000Figure 4: ΔE − E map for the thin vsthick CsI(Tl) crystals.The isotopic resolution obtained using a single readout channel was foundto compete very well with that obtained using the standard two channelreadout (Fig. 3). The applied pulse shape analysis permitted also the iden-tification of particles stopped in the first photodiode and the reduction ofthe identification threshold, due to the thickness of the first photodiode, bya factor of three. Thanks to the pulse shape analysis, it was also possibleto obtain the ballistic deficit free amplitudes, which allowed for easy energyEPJ Web of Conferences01010-p.2 calibration and identification based on the predictions of the range-energytables. For further analysis the parameters of the decomposed pulses wereused in order to speed up the calculations.In the identification maps, the isotopic lines are clearly visible, eventhough the background due to the secondary reactions in the long CsI(Tl)crystals is substantial (Fig. 4). In order to identify the events contributingto the background, a recognition procedure based on the self- organizingneural network has been developed [4]. This method groups together eventswith similar pulse shape descriptors. It allows to identify up to 90% of thebackground events. The efficiency of this method is presented in Fig. 5.Real A2 3 4 5 6 7Yield210310Background reduced by 81.19%Signal/(Signal+Noise):He  75.28% --> 94.65% 3He  83.32% --> 94.00% 4He  20.82% --> 46.13% 6Figure 5: (Colour online) Helium iso-topic distribution. Black line rawdistribution, blue after backgroundsubtraction, red the background.Yield10000125001500017500 Target rapidity 1200013000Mid-rapidity -150 -100 -50 0 50 100 150200030004000Projectile rapidityFigure 6: Azimuthal distributionsof protons measured in three re-gions of the rapidity; b =(0-7.5fm) for Au+Au collisions at 400MeV/nucleon.The energy calibration was performed using the characteristic punch-through points, curvatures of the ΔE − E lines, light-energy conversionformula and the ATIMA range-energy tables. Probabilities of the secondaryreactions for light charged particles as a function of their range in theCsI(Tl) crystals was estimated using the Monte Carlo simulations withinthe GEANT4 environment. The data analysis was performed within theFairRoot framework.The data measured with the KRATTA array in the ASY-EOS experi-ment was used to construct flow observables for light charged particles. Thereaction plane orientation and the centrality of the collision were providedby the CHIMERA and ALADIN TOF Wall detectors. The reaction planeresolution corrections have been calculated according to [5].Figure 6 shows the azimuthal distributions of protons measured withrespect to the reaction plane in three rapidity regions. Target and projectilerapidity regions are dominated by the in-plane emissions, while the mid-IWM EC 2014-01010-p.3rapidity range shows a strong squeeze-out signal.Figure 7 presents the flow parameters v1 and v2 for LCPs as a functionof the scaled center of mass rapidity measured for semi-central collisionswith the KRATTA detector (circles) and the FOPI detector [6] (stars) in acommon angular range (Fig. 2) The upper energy thresholds of KRATTA,associated with the CsI(Tl) crystal thickness, limit the range of the avail-able rapidities. The data points are corrected for the secondary reactionbackground. The agreement between these two detectors and experimentsis very satisfactory.-0.5 0 0.5-0.6-0.4-0.200.20.40.6 Z=1-0.5 0 0.5p-0.5 0 0.5d-0.5 0 0.5t-0.5 0 0.5Z=2-0.5 0 0.5He3-0.5 0 0.5-0.5 0 0.5-0.4-0.3-0.2-0.100.1KRATTAFOPI-0.5 0 0.5 -0.5 0 0.5 -0.5 0 0.5 -0.5 0 0.5 -0.5 0 0.5 -0.5 0 0.5proj(cm)/y(cm)y1v2vFigure 7: Flow of LCP measured with the KRATTA (circles) and FOPI (stars)detectors. Both measurements were performed in the polar angle range 38.5-56.5deg and for the interval of reduced impact parameter range of 0.25-0.45.The KRATTA array, together with the CHIMERA and TOF-wall detec-tors, has proven its usefulness in flow measurements of light charged reactionproducts during the ASY-EOS experiment conducted at GSI. The prelim-inary comparison with the FOPI results measured for the same reactionin a different campaign shows a remarkable agreement and quality of thedata. The results will be compared with UrQMD predictions in order toextract the information contained therein regarding the symmetry term inthe nuclear equation of state.AcknowledgmentsThe authors would like to thank W. Reisdorf for providing the FOPI flowdata. One of us (S. K.) acknowledges the support by the Foundation forPolish Science - MPD program, co-financed by the European Union withinthe European Regional Development Fund. Work made possible throughEPJ Web of Conferences01010-p.4funding by Polish Ministry of Science and Higher Education under grantNo. DPN/N108/GSI/2009.References[1] J. Lukasik et al., Nucl. Instr. Meth. A 709 (2013) 120128[2] P. Russotto et al., Journal of Physics: Conference Series, 420. 5 (2013)[3] G. Pasquali, et al., Nucl. Instr. Meth. A 301 (1991) 101[4] S. Kupny, et al Acta Phys. Polon. B Suppl. 6, 1115-1119 (2013)[5] J.-Y. Ollitrault arXiv:nucl-ex/9711003v2[6] W. Reisdorf, FOPI Collaboration, private communication.IWM EC 2014-01010-p.5

Charged-particle flow measured with the KRATTA detector in the ASY-EOS experiment

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Charged-particle flow measured with the KRATTA detector in the ASY-EOS experiment

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