Gumberidze, M.

Schuldes, H.

Tlusty, P.

GSI Repository

Production of charged pions in the Au+Au at 1.23 AGeV reaction∗M. Gumberidze1, P. Tlusty2 and H. Schuldes3 for the HADES Collaboration1Technische Universita¨t Darmstadt, Darmstadt, Germany; 2Nuclear Physics Institute, Academy of Sciences, 25068 Rez,Czech Republic; 3Institut fur Kernphysik, Johann Wolfgang Goethe-Universitat, 60438 Frankfurt, GermanyThe High Acceptance DiElectron SpectrometerHADES [1] is devoted mainly to study production ofdielectron pairs from proton, pion and nucleus inducedreactions at 1-2 AGeV. At the same time, the spectrometerprovides detection and high quality identification ofcharged particles with a large solid angle.In this contribution we focus on the analysis of chargedpion production in Au + Au collisions at 1.23 AGeV. Theresults contribute to the data from systematic studies ofpion production in heavy ion collisions with an unprecen-dented statistics, and serve as an input for the normalizationof the dielectron data obtained in the same experiment.Figure 1: Velocity vs. charge-times-momentum of chargedparticles in HADES.In April/May 2012, HADES has measured rare and pen-etrating probes in Au+Au collisions at 1.23 AGeV. Aboutseven billion collisions have been recorded in with an eventrate of 10 kHz.For the particle identification, the velocity of particlesdetected in the time-of-flight detectors as a function of mo-mentum was used (Fig. 1). Resulting yields were correctedfor efficiency, acceptance and purity of the PID method,∗Work supported by TU Darmstadt: VH-NG-823, GSI, HelmholtzAlliance HA216/EMMI, SIP JUC Cracow: 2013/10/M/ST2/00042 andNN202198639, HIC for FAIR, NPI Rez: GACR 13-067595 and AS CRM100481202, HGS-HIRe and H-QM.as well as for the detector and tracking inefficiencies usingMonte Carlo simulations.Preliminary results on pi− production are presented inFigure 2, showing the measured transverse mass distri-butions of pi− in different intervals of rapidity. Thetransverse-mass (mt) distributions have been fitted for eachrapidity bin using the sum of two exponential functions:1m2tdN(y)dmt= C1(y)e− mtT1(y) + C2(y)e− mtT2(y)with mt = (p2t +m2)1/2, and pt as transverse momentum.C1,2 are normalizations and T1,2 the inverse slope parame-ters.Due to the wide acceptance of the present experiment wewill be able to do a direct comparison of the HADES datawith the results of previous experiments of charged pionsdone by e.g. FOPI collaboration [2].Figure 2: Transverse-mass distributions for negativelycharged pions in different slices of rapidity. Full lines showthe results of fits to the data (closed points) using the sumof two exponential functions.Our preliminary results show that the pt and y integratednegative pions yields are consistent with the FOPI data.More detailed comparisons are ongoing.References[1] G. Agakishiev et al. [HADES Collaboration], Eur. Phys. J. A41 (2009) 243.[2] W. Reisdorf et al. (FOPI Collaboration) Nucl. Phys. A 781(207) 459-508.GSI SCIENTIFIC REPORT 2014 MU-NQM-HADES-10DOI:10.15120/GR-2015-1-MU-NQM-HADES-10 11

Production of charged pions in the Au+Au at 1.23 AGeV reaction

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Production of charged pions in the Au+Au at 1.23 AGeV reaction

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