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Measurement of the Dalitz Plot Distribution for η→π+ππ0 with KLOE
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Nuclear Physics.
2015 (English)Doctoral thesis, monograph (Other academic)
Abstract [en]

The mechanism of the isospin violating η→π+ππ0 decay is studied in a high precision experiment using a Dalitz plot analysis. The process is sensitive to the difference between up and down quark masses. The measurement provides an important input for the determination of the light quark masses and for the theoretical description of the low energy strong interactions.

The measurement was carried out between 2004 and 2005 using the KLOE detector at the DAΦNE e+e collider located in Frascati, Italy. The data was collected at a center of mass energy corresponding to the φ-meson peak (1019.5 MeV) with an integrated luminosity of 1.6 fb−1. The source of the η-mesons is the radiative decay of the φ-meson: e+e→φ→ηγ, resulting in the world’s largest data sample of about 4.7·106 η→π+ππ0 decay events.

In this thesis, the KLOE Monte Carlo simulation and reconstruction programs are used to optimize the background rejection cuts and to evaluate the signal efficiency. The background contamination in the final data sample is below 1%. The data sample is used to construct the Dalitz plot distribution in the normalized dimensionless variables X and Y. The distribution is parametrized by determining the coefficients of the third order polynomial in the X and Y variables (so called Dalitz plot parameters). The statistical accuracy of the extracted parameters is two times better than any of the previous measurements. In particular the contribution of the X2Y term is found to be different from zero with a significance of approximately 3σ. The systematic effects are studied and found to be of the same size as the statistical uncertainty. The contribution of the terms related to charge conjugation violation (odd powers of the X variable) and the measured charge asymmetries are consistent with zero.

The background subtracted and acceptance corrected bin contents of the Dalitz plot distribution are provided to facilitate direct comparison with other experiments and with theoretical calculations.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. , 146 p.
Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-2516 ; 118
Keyword [en]
Hadron physics, Quark masses, Hadronic decays, Light mesons, Meson-meson interactions
National Category
Subatomic Physics
Research subject
Physics with specialization in Nuclear Physics
URN: urn:nbn:se:uu:diva-266871ISBN: 978-91-554-9427-8OAI: oai:DiVA.org:uu-266871DiVA: diva2:873803
Public defence
2016-01-22, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Available from: 2015-12-18 Created: 2015-11-12 Last updated: 2016-01-14

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Caldeira Balkeståhl, Li
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