dorsal/arxiv
View SchemaA Monte Carlo Calculation of the Pionium Break-up Probability with Different Sets of Pionium Target Cross Sections
| Authors | C. Santamarina, M. Schumann, L. G. Afanasyev, T. Heim |
|---|---|
| Categories | |
| ArXiv ID | physics/0306161 |
| URL | https://arxiv.org/abs/physics/0306161 |
| DOI | 10.1088/0953-4075/36/21/007 |
| Journal | J.Phys.B.At.Mol.Opt.Phys. 36 (2003) 4273-4287 |
Abstract
Chiral Perturbation Theory predicts the lifetime of pionium, a hydrogen-like $\pi^+ \pi^-$ atom, to better than 3% precision. The goal of the DIRAC experiment at CERN is to obtain and check this value experimentally by measuring the break-up probability of pionium in a target. In order to accurately measure the lifetime one needs to know the relationship between the break-up probability and lifetime to a 1% accuracy. We have obtained this dependence by modeling the evolution of pionic atoms in the target using Monte Carlo methods. The model relies on the computation of the pionium--target atom interaction cross sections. Three different sets of pionium--target cross sections with varying degrees of complexity were used: from the simplest first order Born approximation involving only the electrostatic interaction to a more advanced approach taking into account multi-photon exchanges and relativistic effects. We conclude that in order to obtain the pionium lifetime to 1% accuracy from the break-up probability, the pionium--target cross sections must be known with the same accuracy for the low excited bound states of the pionic atom. This result has been achieved, for low $Z$ targets, with the two most precise cross section sets. For large $Z$ targets only the set accounting for multiphoton exchange satisfies the condition.
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"abstract": "Chiral Perturbation Theory predicts the lifetime of pionium, a hydrogen-like\n$\\pi^+ \\pi^-$ atom, to better than 3% precision. The goal of the DIRAC\nexperiment at CERN is to obtain and check this value experimentally by\nmeasuring the break-up probability of pionium in a target. In order to\naccurately measure the lifetime one needs to know the relationship between the\nbreak-up probability and lifetime to a 1% accuracy. We have obtained this\ndependence by modeling the evolution of pionic atoms in the target using Monte\nCarlo methods. The model relies on the computation of the pionium--target atom\ninteraction cross sections. Three different sets of pionium--target cross\nsections with varying degrees of complexity were used: from the simplest first\norder Born approximation involving only the electrostatic interaction to a more\nadvanced approach taking into account multi-photon exchanges and relativistic\neffects. We conclude that in order to obtain the pionium lifetime to 1%\naccuracy from the break-up probability, the pionium--target cross sections must\nbe known with the same accuracy for the low excited bound states of the pionic\natom. This result has been achieved, for low $Z$ targets, with the two most\nprecise cross section sets. For large $Z$ targets only the set accounting for\nmultiphoton exchange satisfies the condition.",
"arxiv_id": "physics/0306161",
"authors": [
"C. Santamarina",
"M. Schumann",
"L. G. Afanasyev",
"T. Heim"
],
"categories": [
"physics.atom-ph"
],
"doi": "10.1088/0953-4075/36/21/007",
"journal_ref": "J.Phys.B.At.Mol.Opt.Phys. 36 (2003) 4273-4287",
"title": "A Monte Carlo Calculation of the Pionium Break-up Probability with Different Sets of Pionium Target Cross Sections",
"url": "https://arxiv.org/abs/physics/0306161"
},
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