L. Di Noto

Exploring the WEP with a pulsed cold beam of antihydrogen

The AEGIS experiment, currently being set up at the Antiproton Decelerator at CERN, has the objective of studying the free fall of antimatter in the Earth?s gravitational field by means of a pulsed cold atomic beam of antihydrogen atoms. Both duration of free fall and vertical displacement of the horizontally emitted atoms will be measured, allowing a first test of the WEP with antimatter.

A moiré deflectometer for antimatter

The precise measurement of forces is one way to obtain deep insight into the fundamental interactions present in nature. In the context of neutral antimatter, the gravitational interaction is of high interest, potentially revealing new forces that violate the weak equivalence principle. Here we report on a successful extension of a tool from atom optics—the moiré deflectometer—for a measurement of the acceleration of slow antiprotons. The setup consists of two identical transmission gratings and a spatially resolving emulsion detector for antiproton annihilations. Absolute referencing of the observed antimatter pattern with a photon pattern experiencing no deflection allows the direct inference of forces present. The concept is also straightforwardly applicable to antihydrogen measurements as pursued by the AEgIS collaboration. The combination of these very different techniques from high energy and atomic physics opens a very promising route to the direct detection of the gravitational acceleration of neutral antimatter.

AEgIS experiment commissioning at CERN

The AEgIS Experiment is an international collaboration based at CERN whose aim is to perform the first direct measurement of the gravitational acceleration g of antihydrogen in the gravitational field of the Earth. Cold antihydrogen will be produced with a pulsed charge exchange reaction in a cylindrical Penning trap where antiprotons will be cooled to 100mK. The cold antihydrogen will be produced in an excited Rydberg state and subsequently formed into a beam. The deflection of the antihydrogen beam will be measured by using Moire deflectometer gratings. After being approved in late 2008, AEgIS started taking data in a commissioning phase early 2012. This report presents an overview of the AEgIS experiment, describes its current status and shows the first measurements on antiproton catching and cooling in the 5 T Penning catching trap. We will also present details on the techniques needed for the 100mK antihydrogen production, such as pulsed positronium production and its excitation with lasers.

Detection of low energy antiproton annihilations in a segmented silicon detector

The goal of the AEIS experiment at the Antiproton Decelerator (AD) at CERN, is to measure directly the Earths gravitational acceleration on antimatter by measuring the free fall of a pulsed, cold antihydrogen beam. The final position of the falling antihydrogen will be detected by a position sensitive detector. This detector will consist of an active silicon part, where the annihilations take place, followed by an emulsion part. Together, they allow to achieve 1% precision on the measurement of with about 600 reconstructed and time tagged annihilations. We present here the prospects for the development of the AEIS silicon position sentive detector and the results from the first beam tests on a monolithic silicon pixel sensor, along with a comparison to Monte Carlo simulations.

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.

Measuring

experiments main goal is to measure the local gravitational acceleration of antihydrogen and thus perform a direct test of the weak equivalence principle with antimatter. In the first phase of the experiment the aim is to measure with 1% relative precision. This paper presents the antihydrogen production method and a description of some components of the experiment, which are necessary for the gravity measurement. Current status of the experimental apparatus is presented and recent commissioning results with antiprotons are outlined. In conclusion we discuss the short-term goals of the collaboration that will pave the way for the first gravity measurement in the near future.

\bar{g}

A magnetic transport line, a magnetic field terminator and a positron buncher were designed and built to focus low-energy positron pulses from a Surko-type accumulator on a porous target. The 25 electrodes buncher, which produces a parabolic potential, was designed to implant 5 ns positron bunches with a spot of 3 mm into a target held at cryogenic temperature. These pulses will be used to obtain cooled Ps clouds into vacuum for laser excitation in spectroscopy experiments. By using high-voltage fast switches and a proper mu-metal shield the requirement to form Ps in a free (magnetic and electric) field region was satisfied compatibly with the request of injecting positrons at energies of 5-9 keV. The optical design, the electrical circuitry of the buncher and the construction solutions of the whole apparatus will be presented and explained.

with

The principal aim of the AEgIS experiment at CERN is to measure the acceleration of antihydrogen due to Earths gravitational field. This would be a test of the Weak Equivalence Principle, which states that all bodies fall with the same acceleration independently of their mass and composition. The effect of Earths gravitational field on antimatter will be determined by measuring the deflection of the path of the antihydrogen from a straight line. The position of the antihydrogen will be found by detecting its annihilation on the surface of a silicon detector. The gravitational measurement in AEgIS will be performed with a gravity module, which includes the silicon detector, an emulsion detector and a scintillating fibre time-of-flight detector. As the experiment attempts to determine the gravitational acceleration with a precision of 1%, a position resolution better than 10 μm is required. Here we present the results of a study of antiproton annihilations in a 3D silicon pixel sensor and compare the results with a previous study using a monolithic active pixel sensor. This work is part of a larger study on different silicon sensor technologies needed for the development of a silicon position detector for the AEgIS experiment. The 3D detector together with its readout electronics have been originally designed for the ATLAS detector at the LHC. The direct annihilation of low energy antiprotons ( ~ 100 keV) takes place in the first few μm of the silicon sensor and we show that the charged products of the annihilation can be detected with the same sensor. The present study also aims to understand the signature of an antiproton annihilation event in segmented silicon detectors and compares it with a GEANT4 simulation model. These results will be used to determine the geometrical and process parameters to be adopted by the silicon annihilation detector to be installed in AEgIS.

{\rm AE\bar{g}IS}

Measurement of the Solar pp-neutrino flux completed the measurement of Solar neutrino fluxes from the pp-chain of reactions in Borexino experiment. The result is in agreement with the prediction of the Standard Solar Model and the MSW/LMA oscillation scenario. A comparison of the total neutrino flux from the Sun with Solar luminosity in photons provides a test of the stability of the Sun on the 10(5) years time scale, and sets a strong limit on the power production by the unknown energy sources in the Sun.

, progress and perspectives

Neutrino produced in a chain of nuclear reactions in the Sun starting from the fusion of two protons, for the first time has been detected in a real-time detector in spectrometric mode. The unique properties of the Borexino detector provided an oppurtunity to disentangle pp-neutrino spectrum from the background components. A comparison of the total neutrino flux from the Sun with Solar luminosity in photons provides a test of the stability of the Sun on the 105 years time scale, and sets a strong limit on the power production in the unknown energy sources in the Sun of no more than 4% of the total energy production at 90% C.L.