Beam particle tracking with a low-mass mini time projection chamber in the PEN experiment

Abstract

The international PEN collaboration aims to obtain the branching ratio for the pion electronic decay ${\pi }^{+}\to e^{+}{\nu }_e(\gamma )$, aka ${\pi }_{e2}$, to a relative precision of $5\times 10^{-4}$ or better. The PEN apparatus comprises a number of detection systems, all contributing vital information to the PEN event reconstruction. This paper discusses the design, performance, and Monte Carlo simulation of the mini time projection chamber (mTPC) used for pion, muon, and positron beam particle tracking. We also review the use of the extracted trajectory coordinates in the analysis, in particular in constructing observables critical for discriminating background processes, and in maximizing the fiducial volume of the target in which decay event vertices can be accepted for branching ratio extraction without introducing bias.

arXiv comment24 pages, 23 figures

References in corpus (8)

• The Standard Model prediction for R_{e/mu}^{(pi,K)}
• Precise Measurement of the Pi+ -> Pi0 e+ nu Branching Ratio
• Improved measurement of the $π\rightarrow \mbox{e} ν$ branching ratio
• New Precise Measurement of the Pion Weak Form Factors in the Pi+ -> e+ nu gamma Decay
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• Precise Measurement of the Pion Axial Form Factor in the Pi+ -> e+ nu gamma Decay
• Design, Commissioning and Performance of the PIBETA Detector at PSI
• Experimental study of rare charged pion decays