Abstract
The overarching goal of the ALPHA collaboration is to magnetically confine antihydrogen atoms for spectroscopic studies. An outline of the trapping experiment procedure was already presented in Sect 3.6. Moreover, Chap. 6 demonstrated that the cosmic background is under control, and the vast majority of cosmic events can be identified and rejected. However, cosmic rays are not the only background competing with the antihydrogen signal. As described in Sect. 6.1.2, mirror-trapped antiprotons can also be confined in the magnetic field of the neutral-atom trap. This chapter will start by describing the mirror-confined antiproton background, along with the methods used to attempt to remove the bare antiprotons and/or to discriminate out the signals associated with them. To assist the background identification and neutral-atom trapping effort, careful Monte Carlo simulations were performed, and will be described below. Several control and cross-check measurements, which complement the trapping experiments, are also detailed.
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Notes
- 1.
Note that the electrodes at the ends of the trap decrease in radius. This radial step occurs at \({\pm }13\) cm, and is coincident with the four red triangles in the upper right-hand section of Fig. 7.3. The antiproton simulations take into account this feature, and a small number of simulated antiproton annihilations can be seen at \({\pm }13\) cm. It is also of note that all four late-time annihilations occur to the right, which may be the result of small field errors not included in the simulations.
- 2.
The initial analysis gave 6 events that satisfied all selection criteria [1]. The new number is based on the reconstruction routines described in Chap. 5, which are updated and improved from the routines used in the initial analysis. It should be noted that the author performed both the original and improved analyses, as well as implemented the improvements to the reconstruction routines.
- 3.
The validation of the Monte Carlo simulations shown in Sect. 7.2 for mirror-confined antiprotons was completed in the Summer of 2010.
- 4.
A total of 38 events were reported in [3]. The results presented here follow the reconstruction routines described in Chap. 5, which are updated and improved from the routines used in the original publication. It should be noted that the author performed both the original and improved analyses, as well as implemented the improvements to the reconstruction routines.
References
G.B. Andresen et al. (ALPHA collaboration), Phys. Lett. B 695, 95 (2011)
E. Butler, Ph.D. thesis, Swansea University, 2011
G.B. Andresen et al. (ALPHA collaboration), Nature 468, 673 (2010)
OPERA-3D Reference Manual, Cobham, Vector Fields Ltd, UK
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Hydomako, R. (2013). The Trapping of Antihydrogen. In: Detection of Trapped Antihydrogen. Springer Theses. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-34484-8_7
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DOI: https://doi.org/10.1007/978-3-642-34484-8_7
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