18th Conference of Czech and Slovak Physicists, Olomouc, Czech Republic, September 16–19, 2014
Electromagnetic Calorimeter for the HADES Spectrometer Ondřej Svoboda1 , Christoph Blume2 , Wojciech Czyžycki3 , Eliane Epple4 , Laura Fabbietti4 , Tetyana Galatyuk5 , Marina Golubeva6 , Fedor Guber6 , Stanislav Hlaváč7 , Alexander Ivashkin6 , Marcin Kajetanowic8 , Behruz Kardan2 , Wolfgang Koenig9 , Andrej Kugler1 , Kirill Lapidus4 , Sergey Linev9 , Edward Lisowski3 , Oleg Petukhov6 , Jerzy Pietraszko9 , Andrei Reshetin6 , Pablo Rodríguez-Ramos1 , Adrian Rost5 , Piotr Salabura8 , Yuri Gennadievich Sobolev1 , Pavel Tlustý1 , and Michael Traxler9 (on behalf of the HADES collaboration) 1
[email protected], Nuclear Physics Institute, Academy of Sciences of the Czech Republic, Řež, 250 68, Czech Republic Institut für Kernphysik, Goethe-Universität, 60438 Frankfurt, Germany 3 Institute of Technology Cracow, 31-155 Cracow, Poland 4 Excellence Cluster ‘Origin and Structure of the Universe’, Technische Universität München, 85748 Garching, Germany 5 Technische Universität Darmstadt, 64289 Darmstadt, Germany 6 Institute for Nuclear Research, Russian Academy of Sciences, 117312 Moscow, Russia 7 Institute of Physics, Slovak Academy of Sciences, 845 11 Bratislava, Slovakia 8 Smoluchowski Institute of Physics, Jagiellonian University of Kraków, 30-059 Cracow, Poland 9 GSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt, Germany 2
Abstract. The HADES spectrometer currently operating on the beam of SIS18 accelerator in GSI will be moved to a new position in the CBM/HADES cave of the future FAIR complex. Electromagnetic calorimeter (ECAL) will enable the HADES@FAIR experiment to measure data on neutral meson production in heavy ion collisions at the energy range of 2–10 AGeV on the beam of the new accelerator SIS100@FAIR. Calorimeter will be based on 978 massive lead glass modules read out by photomultipliers and a novel front-end electronics. Layout of the ECAL detector as well as beam test of single modules and electronics are shortly described.
be investigated (the latter being of importance for the still unsettled question of the ω electromagnetic transition form factor). Last but not least the photon measurements are of large interest for the HADES strangeness program which addresses spectroscopy of neutral Λ(1405) and Σ(1385) resonances in elementary and HI reactions.
1 Motivation The High Acceptance DiElectron Spectrometer (HADES) focuses on dielectron measurements to study in-medium modifications. An extensive study of proton – proton, pion – proton, proton – nucleus, pion – nucleus, and nucleus – nucleus collisions up to
[email protected] [1] have been done in the past decade. HADES is currently operating on the beamline of SIS18 accelerator at GSI Darmstadt, Germany. The current setup consist of a diamond start detector (START), Ring Imaging Cherenkov detector (RICH), four layers of multiwire drift chambers (MDC), a superconducting toroidal magnet (ILSE), time of flight walls from resistive plate chambers (RPC) and plastic scintillators (TOF), pre-shower detector (SHOWER) and Forward Wall detector [2]. After build-up of FAIR the Hades spectrometer will be moved to a newly build cave shared with the CBM experiment and will continue with the studies at higher energies. Electromagnetic calorimeter (ECAL) is developed to be included into HADES and measure the respective π 0 and η meson two gamma decay yields together with the dielectron data measured in HADES spectrometer for the knowledge of dielectron cocktail at incident heavy ion energies 2–10 AGeV. ECAL will also offer better electron/pion suppression for large momenta (p>400 MeV/c) as compared to the present situation (at lower momenta the electron/hadron identification is provided by the RICH and RPC detectors from HADES spectrometer). Furthermore the ω production via the π 0 π + π − and the π 0 e+ e− decays can
Figure 1. Layout of the electromagnetic calorimeter for the HADES spectrometer.
2 ECAL layout The ECAL is following basic HADES geometry – six separate sectors covering almost full azimuthal angle and polar angle 18◦ to 45◦ , see Figure 1 or [3]. 83
Svoboda O. et al.: Electromagnetic Calorimeter for the HADES Spectrometer
Beam tests of ECAL modules were performed on secondary gamma beam from MAMI Mainz facility. Relative energy resolution was measured to be 5.5 % for modules with 3” photomultiplier and 1 GeV photons, respectively 5.8 % for 1.5” photomultiplier. Energy leakage between the neighbour modules was tested with parallel and declined beams and energy of original photon was successfully recovered.
Calorimeter will consist of 978 modules of lead glass read out by a photomultiplier. The lead glass crystal of CEREN 25 type has dimensions 92×92×420 mm3 . Two sizes of photomultipliers (PMT) will be used to read out the modules, 1.5” EMI 9903KB and 3” Hamamatsu R6091. Two independent read-out systems named “Cracow” and “PaDiWa Amps” are being developed for the calorimeter.
3 In-beam tests of single modules Secondary gamma beam at MAMI Mainz facility was used to test relative energy resolution of the modules and electronics. Dedicated measurements were done with declined beams to test energy leakage between the modules. Modules with 1”, 1.5” and 3” PMTs were tested at eight different energies and with MA8000 shaper and CAEN DT5742 ADC. Module with 1” PMT Hamamatsu R8619 was proved to be not suitable because of non-linear response and worse relative energy resolution, see Figure 2.
Figure 3. Energy deposited in one module hit by the gamma beam (upper) and sum of energies deposited in both neighboring modules (lower). Case of 1217.8 MeV and different “path-length” of the photon inside the module (measured with declined beam and different hit position).
Figure 2. Relative energy resolution of calorimeter modules equipped with different photomultipliers (numbers behind the names stand for resolution at 1 GeV).
Acknowledgments
Tests of the two front-end boards showed that they are fully comparable in terms of energy resolution. Their results were even better than with the standard CAEN ADC. Energy leakage between two modules was examined hitting one module with the gamma beam closer and closer to the common boarder. The 6◦ and 12◦ declined beams with respect to the module axis were also used. As shown in Figure 3, original energy of the photon can be reconstructed for all studied cases. Relative energy resolution does not significantly depend neither on the gamma position nor the incoming angle.
This work has been supported by Czech MSMT LG 12007, GACR 13-067595, AS CR M100-481202 and by the European Community FP7 – Capacities, contract HadronPhysics3 n° 283286. We would like to thank to A. Neiser, P. Ott, P. Otte, A. Thomas, and P. Skott from IK-JGU, for their help with measurements.
References [1] G. Agakishiev et al. (HADES collaboration), Hades experiments: investigation of hadron inmedium properties, J. Phys.: Conf. Ser. 420, 012013 (2013). [2] G. Agakishiev et al. (HADES collaboration), The high-acceptance dielectron spectrometer HADES, Eur. Phys. J. A 41, 243 (2009). [3] A. Kugler et al. (HADES collaboration), Electromagnetic Calorimeter for HADES Experiment, Proceedings of the 14th ICATPP Conference, vol. 8 (2013).
4 Summary Electromagnetic calorimeter ECAL is being built to enhance experimental possibilities and physics program of the HADES spectrometer. The ECAL will enable to measure gamma photons coming from various decays as well as neutral pions. 84
