R. Santoro

Particle tracking at cryogenic temperatures: the Fast Annihilation Cryogenic Tracking (FACT) detector for the AEgIS antimatter gravity experiment

The AEgIS experiment is an interdisciplinary collaboration between atomic, plasma and particle physicists, with the scientific goal of performing the first precision measurement of the Earths gravitational acceleration on antimatter. The principle of the experiment is as follows: cold antihydrogen atoms are synthesized in a Penning-Malmberg trap and are Stark accelerated towards a moire deflectometer, the classical counterpart of an atom interferometer, and annihilate on a position sensitive detector. Crucial to the success of the experiment is an antihydrogen detector that will be used to demonstrate the production of antihydrogen and also to measure the temperature of the anti-atoms and the creation of a beam. The operating requirements for the detector are very challenging: it must operate at close to 4 K inside a 1 T solenoid magnetic field and identify the annihilation of the antihydrogen atoms that are produced during the 1 μs period of antihydrogen production. Our solution—called the FACT detector—is based on a novel multi-layer scintillating fiber tracker with SiPM readout and off the shelf FPGA based readout system. This talk will present the design of the FACT detector and detail the operation of the detector in the context of the AEgIS experiment.

AEgIS at ELENA: outlook for physics with a pulsed cold antihydrogen beam.

The efficient production of cold antihydrogen atoms in particle traps at CERN’s Antiproton Decelerator has opened up the possibility of performing direct measurements of the Earth’s gravitational acceleration on purely antimatter bodies. The goal of the AEgIS collaboration is to measure the value of g for antimatter using a pulsed source of cold antihydrogen and a Moiré deflectometer/Talbot–Lau interferometer. The same antihydrogen beam is also very well suited to measuring precisely the ground-state hyperfine splitting of the anti-atom. The antihydrogen formation mechanism chosen by AEgIS is resonant charge exchange between cold antiprotons and Rydberg positronium. A series of technical developments regarding positrons and positronium (Ps formation in a dedicated room-temperature target, spectroscopy of the n=1–3 and n=3–15 transitions in Ps, Ps formation in a target at 10 K inside the 1 T magnetic field of the experiment) as well as antiprotons (high-efficiency trapping of , radial compression to sub-millimetre radii of mixed plasmas in 1 T field, high-efficiency transfer of to the antihydrogen production trap using an in-flight launch and recapture procedure) were successfully implemented. Two further critical steps that are germane mainly to charge exchange formation of antihydrogen—cooling of antiprotons and formation of a beam of antihydrogen—are being addressed in parallel. The coming of ELENA will allow, in the very near future, the number of trappable antiprotons to be increased by more than a factor of 50. For the antihydrogen production scheme chosen by AEgIS, this will be reflected in a corresponding increase of produced antihydrogen atoms, leading to a significant reduction of measurement times and providing a path towards high-precision measurements. This article is part of the Theo Murphy meeting issue ‘Antiproton physics in the ELENA era’.

Measurement of antiproton annihilation on Cu, Ag and Au with emulsion films

The characteristics of low energy antiproton annihilations on nuclei (e.g. hadronization and product multiplicities) are not well known, and Monte Carlo simulation packages that use different models provide different descriptions of the annihilation events. In this study, we measured the particle multiplicities resulting from antiproton annihilations on nuclei. The results were compared with predictions obtained using different models in the simulation tools GEANT4 and FLUKA. For this study, we exposed thin targets (Cu, Ag and Au) to a very low energy antiproton beam from CERNs Antiproton Decelerator, exploiting the secondary beamline available in the AEgIS experimental zone. The antiproton annihilation products were detected using emulsion films developed at the Laboratory of High Energy Physics in Bern, where they were analysed at the automatic microscope facility. The fragment multiplicity measured in this study is in good agreement with results obtained with FLUKA simulations for both minimally and heavily ionizing particles.

Physical Society of Japan : Overview of recent work on laser excitation of positronium for the formation of antihydrogen

P. Yzombard1, C. Amsler2, T. Ariga2, G. Bonomi3,4, P. Bräunig5, R. S. Brusa6,7, L. Cabaret1, M. Caccia8, R. Caravita9,10,14, F. Castelli8,11, G. Cerchiari12, D. Comparat1, G. Consolati8,13, A. Demetrio5, L. Di Noto9,10, M. Doser14, A. Ereditato2, C. Evans8,13, R. Ferragut8,13, J. Fesel14, A. Fontana4, S. Gerber14, M. Giammarchi8, A. Gligorova15, F. Guatieri6,7, S. Haider14, H. Holmestad16, T. Huse16, A. Kellerbauer12, D. Krasnický9,10, V. Lagomarsino9,10, P. Lansonneur17, P. Lebrun17, C. Malbrunot14,18, S. Mariazzi18, V. Matveev19,20, Z. Mazzotta8,11, G. Nebbia21, P. Nedelec17, M. Oberthaler5, N. Pacifico15, D. Pagano3,4, L. Penasa6,7, V. Petracek22, C. Pistillo2, F. Prelz8, M. Prevedelli23, L. Ravelli6,7, B. Rienaecker14, O.M. Røhne16, A. Rotondi4,24, M. Sacerdoti8,11, H. Sandaker16, R. Santoro8,25, P. Scampoli2,26, L. Smestad14,27, F. Sorrentino9,10, I. M. Strojek22, G. Testera10, I. C. Tietje14, S. Vamosi18, E. Widmann18, J. Zmeskal18, N. Zurlo4,28

The AEgIS experiment at CERN: measuring antihydrogen free-fall in earth's gravitational field to test WEP with antimatter

The AEgIS (Antimatter Experiment: Gravity, Interferometry, Spectroscopy) experiment is designed with the objective to test the weak equivalence principle with antimatter by studying the free fall of antihydrogen in the Earths gravitational field. A pulsed cold beam of antihydrogen will be produced by charge exchange between cold Ps excited in Rydberg state and cold antiprotons. Finally the free fall will be measured by a classical moire deflectometer. The apparatus being assembled at the Antiproton Decelerator at CERN will be described, then the advancements of the experiment will be reported: positrons and antiprotons trapping measurements, Ps two-step excitation and a test-measurement of antiprotons deflection with a small scale moire deflectometer.

submitter : Positron Manipulation and Positronium Laser Excitation in AEgIS

Production of antihydrogen by using the charge exchange reaction, as proposed by AEgIS (Antimatter Experiment: gravity, Interferometry, Spectroscopy), requires the formation of a dense cloud of positronium atoms excited to Rydberg states. In this work, the recent advances in AEgIS towards this result are described. Namely, the manipulation of positrons to produce bunches containing more than 108 particles and the laser excitation of positronium to Rydberg states, using n=3 as intermediate level, are presented.

The DAQ system for the AEḡIS experiment

In the sociology of small- to mid-sized (O(100) collaborators) experiments the issue of data collection and storage is sometimes felt as a residual problem for which well-established solutions are known. Still, the DAQ system can be one of the few forces that drive towards the integration of otherwise loosely coupled detector systems. As such it may be hard to complete with off-the-shelf components only. LabVIEW and ROOT are the (only) two software systems that were assumed to be familiar enough to all collaborators of the AEḡIS (AD6) experiment at CERN: working out of the GXML representation of LabVIEW Data types, a semantically equivalent representation as ROOT TTrees was developed for permanent storage and analysis. All data in the experiment is cast into this common format and can be produced and consumed on both systems and transferred over TCP and/or multicast over UDP for immediate sharing over the experiment LAN. We describe the setup that has been able to cater to all run data logging and long term monitoring needs of the AEḡIS experiment so far.

Testing the Weak Equivalence Principle with an antimatter beam at CERN

The goal of the AEgIS experiment is to measure the gravitational acceleration of antihydrogen – the simplest atom consisting entirely of antimatter – with the ultimate precision of 1%. We plan to verify the Weak Equivalence Principle (WEP), one of the fundamental laws of nature, with an antimatter beam. The experiment consists of a positron accumulator, an antiproton trap and a Stark accelerator in a solenoidal magnetic field to form and accelerate a pulsed beam of antihydrogen atoms towards a free-fall detector. The antihydrogen beam passes through a moir e deflectometer to measure the vertical displacement due to the gravitational force. A position and time sensitive hybrid detector registers the annihilation points of the antihydrogen atoms and their time-of-flight. The detection principle has been successfully tested with antiprotons and a miniature moir e deflectometer coupled to a nuclear emulsion detector.