CBM Progress Report 2006 - GSI

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Simulations CBM Progress Report 2006 Dielectron Detection Capabilities of HADES for Beam Energies accessible at FAIR B. Bannier 1 , F. Dohrmann 1 , E. Grosse 1,2 , B. Kämpfer 1 , R. Kotte 1 , L. Naumann 1 , and J. Wüstenfeld 1 For the FAIR project considerable updates of existing accelerator facilities at the GSI Darmstadt are projected. The available beam energies of the new SIS100 and SIS300 accelerators will be in the range of 2 AGeV to 45 AGeV. Experiments with both elementary probes as well as heavyions at beam energies ≤ 3.5 AGeV have been performed with the HADES detector at SIS18. The possible dielectron detection capabilities of HADES at the new facilities, focusing on Carbon–Carbon collisions at beam energies of 8 − 25 AGeV were studied. Simulations were carried out using an event generator based on the state of the art relativistic transport code UrQMDv1.3p1 [1] together with a generic interface for additional decays simulated with the PLUTO phase space generator on top of UrQMD. In particular, this is used for implanting dielectron decay channels into UrQMD events. The dielectron sources considered are π 0 , η, ∆ + , ω, ρ 0 and φ. A considerable source of background is photon conversionγ → e + e − . Important sources of photons are the decays of π 0 and η mesons, therefore these decays have been processed independently of other sources to allow for a correct event structure. Based on this event generator dielectron spectra for 8 AGeV and 25 AGeV are shown in Fig. 1 taking into account only the geometrical acceptance of the HADES detector as it is currently installed. Tracking of particles through the magnetic field has not been included in these studies. For both energies a peak in the ρ, ω mass region is visible, although the background situation at the higher energy deteriorates considerably. While the combinatorial background was found to be an important source of dielectrons, in our simulation distributions of like-sign pairs gave a good description of the combinatorial background. The yield of true pairs from ω → e + e − decays was found to be above the combinatorial background in the respective invariant pair mass region. The like-sign method allows subtraction of the combinatorial background from spectra and the yield of true pairs from ρ 0 → e + e − is larger than the fluctuations of the combinatorial background. The φ meson yield found was too low compared to the expected ρ 0 yield in the respective invariant mass region to allow reliable studies. In summary, the simulations indicate that a determination of the yield of true pairs from particle decays in the ρ − ω mass region after one week of beam time seems feasible. Further investigations have to consider the HADES acceptance (possibly with modified hardware setups); tracking of the particles through the magnetic field and the detector material should be taken into account. This study [2] has to be seen in line with other studies [3,4] on this subject. 1 FZD, Dresden; 2 TU Dresden 26 ] -1 counts per week [(32MeV) ] -1 counts per week [(32MeV) 5 10 4 10 3 10 2 10 10 1 -1 10 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 M + - [GeV] 5 10 4 10 3 10 2 10 10 1 -1 e e all π0 η + Δ Dalitz 0 ρ ω ω Dalitz φ γ conv. 10 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 M + - [GeV] e e comb. bg. all π0 η + Δ Dalitz 0 ρ ω ω Dalitz φ γ conv. comb. bg. Fig. 1: Invariant mass spectra for central Carbon-Carbon collisions at beam energies of 8 AGeV (upper panel) and 25 AGeV (lower panel) after one week of beamtime. Pairs are created from all e + and e − emitted into the geometrical HADES acceptance with momenta p > 50 MeV. Leptons from pairs with opening angles smaller than 9 o are excluded. Particle momenta have been convolved with a momentum dependent error following the procedure given in [5]. Details on how to subtract combinatorial background using the like-sign method are given in [2]. References [1] http://www.th.physik.uni-frankfurt.de/∼urqmd [2] B. Bannier, Diploma Thesis, Technische Universität Dresden, Sep. 2006 [3] T. Galatyuk and J. Stroth, CBM-PHYS-note-2006-001, internal report, GSI Darmstadt 2006 [4] A. Kugler, Talk at CBM meeting, GSI Darmstadt 2004; Proc. Nucl. Phys. Winter meeting, Bormio 2006 [5] R. Holzmann, HAFT: Hades Acceptance Filter for Theorists, internal report, GSI Darmstadt 2006, http://hades-wiki.gsi.de/cgi-bin/view/SimAna/HadesAcceptanceFilter
CBM Progress Report 2006 Detector Developments Results on timing properties of SCCVD diamond detectors for MIPs M. Petrovici, M. Petris¸, G. Caragheorgheopol, V. Simion, D. Moisă National Institute for Physics and Nuclear Engineering, Bucharest, Romania E. Berdermann, M. Ciobanu, A. Martemiyanov, M. Pomorski Gesellschaft für Schwerionenforschung, Darmstadt, Germany First encouraging results on timing performance of diamond detectors for MIPs were obtained using policrystal diamond detectors (PC) [1]. The timing properties of two single crystal diamond detectors (SCCVD-DD)with a thickness of 300 µm and 500 µm using a 90 Sr source and an applied electric field of∼1V/µm are presented in this report. The diamonds were placed in the collimated beam of beta particles, the reference signal being delivered by a NE102 plastic scintillator. In the first measurements the signals delivered by the SCCVD-DD were amplified by fast amplifiers developed for multistrip multigap resistive plate counters (MSM- GRPC) [2] and a FTA810L amplifier. The amplified signals of the SCCVD-DD and the signal of the plastic scintillator coupled with a phototube were split and processed for charge and timing information. The start signals were delivered by the overlap coincidence between the signals of the diamond detector and the plastic scintillator. Fig.1 shows the charge distribuitions for the 300 µm thickness diamond detector (Fig.1a) and for the plastic scintillator (Fig.1b). Figure 1: Charge distribution for: a) 300 µm diamond detector and b) plastic scintillator The obtained time of flight spectrum after walk correction can be followed in Fig 2a. Subtracting the contribution of the plastic scintillator of 125 ps, measured between two identical plastic scintillators coupled to identical phototubes, a time resolution of 147 ps is obtained. The time of flight spectrum obtained using the SCCVD- DD of 500 µm thickness and the same experimental setup is shown in Fig.2b. The time resolution under this condition, after subtracting the contribution of the reference detector, was 214ps. In the second part of the measurements the signals delivered by the SCCVD-DD were amplified by a charge sensitive preamplifier (CSA) with a 0.7 ns rise 27 a) b) Figure 2: The time of flight spectra after walk correction: a) 300 µm and b)500 µm SCCVD-DD time. The rest of the experimental setup was the same. The results are presented in Fig.3. The time resolution obtained using the SCCVD-DD of 300 µm thickness and a CSA with 0.7 ns rise time is 374 ps, while for SCCVD-DD of 500 µm thickness a time resolution of 1.14 ns is obtained. a) b) Figure 3: Time of flight spectra using charge sensitive preamplifier with 0.7 ns rise time: a) 300 µm abd b)500 µm SCCVD-DD Based on the results presented in this report one could conclude that better results were obtained using the thinner detector for the same FEE used for the amplification of the signals delivered by the SCCVD-DD. Better performance in terms of time resolution gives the fast FEE electronics developed for MSMGRPC. Detailed efficiency studies and in-beam tests are in progress. References [1] M. Petrovici, E. Berdermann, M. Petris¸, G. Caragheorgheopol, D. Moisă, NIPNE Scientific Report, 2001, p. 43 [2] M. Ciobanu, A. Schüttauf, E. Cordier, N. Herrmann, K.D. Hildenbrand, Y.J. Kim, Y. Leifels, M. Marquardt, M.Kis, P.Koczon, M. Petrovici, J. Weinert, X. Zhang, will be published
Page 1 and 2: CBM Progress Report 2006 1
Page 3 and 4: Contents Preface i Overview 1 Simul
Page 5 and 6: CBM Progress Report 2006 Overview C
Page 7 and 8: CBM Progress Report 2006 Simulation
Page 29: CBM Progress Report 2006 Simulation
Page 33 and 34: CBM Progress Report 2006 Detector D
Page 53 and 54: CBM Progress Report 2006 FEE and DA
Page 61 and 62: CBM Progress Report 2006 Appendices
Page 63 and 64: Contacts CBM Spokesperson: Peter Se

CBM Progress Report 2006 - GSI

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