The DIRAC spectrometer installed at CERN PS was upgraded in order to study simultaneously A2π and AπK atoms, namely the bound states of two π mesons, and of π and K mesons, respectively. The detector ...system can now accept a high intensity beam of 2–6×1011 primary protons per second. The electronics and the data-acquisition system can handle a very large amount of data to identify π, K, p, e and µ, allowing the selection of ππ and πK pairs in the offline analysis. The resolution of the longitudinal and transverse components of the relative momentum Q of each meson pair in their center-of-mass system with respect to the direction of the pair was substantially improved. The analysis of their distributions allowed an reliable separation between the meson pairs originating from hadronic atoms and the backgrounds permitting the measurement of the lifetimes of hadronic atoms in the ground state and π–π, π–K s-wave scattering lengths. The upgraded setup also allowed the study of the long-lived excited states of ππ atoms.
A large area transition radiation detector for the NOMAD experiment Bassompierre, G.; Bermond, M.; Berthet, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/1998, Letnik:
403, Številka:
2
Journal Article
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A transition radiation detector to identify electrons at 90% efficiency with a rejection factor against pions of 10
3 on an area of 2.85 × 2.85 m
2 has been constructed for the NOMAD experiment. Each ...of its 9 modules includes a 315 plastic foil radiator and a detector plane of 176 vertical straw tubes filled with a xenon-methane gas mixture. Details of the design, construction and operation of the detector are given.
The goal of the DIRAC experiment at CERN (PS212) is to measure the π+π− atom lifetime with 10% precision. Such a measurement would yield a precision of 5% on the value of the S-wave ππ scattering ...lengths combination |a0−a2|. Based on part of the collected data we present a first result on the lifetime, τ=2.91−0.62+0.49×10−15 s, and discuss the major systematic errors. This lifetime corresponds to |a0−a2|=0.264−0.020+0.033mπ−1.
Evidence for πK-atoms with DIRAC Adeva, B.; Afanasyev, L.; Allkofer, Y. ...
Physics letters. B,
04/2009, Letnik:
674, Številka:
1
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We present evidence for the first observation of electromagnetically bound π±K∓-pairs (πK-atoms) with the DIRAC experiment at the CERN-PS. The πK-atoms are produced by the 24 GeV/c proton beam in a ...thin Pt-target and the π± and K∓-mesons from the atom dissociation are analyzed in a two-arm magnetic spectrometer. The observed enhancement at low relative momentum corresponds to the production of 173±54πK-atoms. The mean life of πK-atoms is related to the s-wave πK-scattering lengths, the measurement of which is the goal of the experiment. From these first data we derive a lower limit for the mean life of 0.8 fs at 90% confidence level.
DIRAC: A high resolution spectrometer for pionium detection Adeva, B.; Afanasyev, L.; Benayoun, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2003, Letnik:
515, Številka:
3
Journal Article
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Odprti dostop
The DIRAC spectrometer has been commissioned at CERN with the aim of detecting π+π− atoms produced by a 24GeV/c high intensity proton beam in thin foil targets. A challenging apparatus is required to ...cope with the high interaction rates involved, the triggering of pion pairs with very low relative momentum and the measurement of the latter with resolution around 0.6MeV/c. The general characteristics of the apparatus are explained and each part is described in some detail. The main features of the trigger system, data-acquisition, monitoring and set-up performances are also given.
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