A sample of 7253 K+/- -> pi(+/-)e(+)e(-)(gamma) decay candidates with 1.0% background contamination has been collected by the NA48/2 experiment at the CERN SPS, which allowed a precise measurement of the decay properties. The branching ratio in the full kinematic range was measured to be BR = (3.11 +/- 0.12) x 10(-7), where the uncertainty includes also the model dependence. The shape of the form factor W(z), where z = (M-ee/M-K)(2) was parameterized according to several models, and, in particular, the slope delta of the linear form factor W(z) = W-0(1 + delta z) was determined to be delta = 2.32 +/- 0.18. A possible CP violating asymmetry of K+ and K- decay widths was investigated, and a conservative upper limit of 2.1 X 10(-2) at 90% CL was established. (C) 2009 Elsevier B.V. All rights reserved.
Precise measurement of the K ± → π ± e + e - decay / J. R., B., A. J., C., G., K., C., L., D. J., M., M. W., S., S. A., W., R., A., G., B., N., C., A., C., D., C., V., F., M., F., L., G., A., G., W., K., A., N., A., M., M., P., et al.. - In: PHYSICS LETTERS. SECTION B. - ISSN 0370-2693. - STAMPA. - 677:5(2009), pp. 246-254. [10.1016/j.physletb.2009.05.040]
Precise measurement of the K ± → π ± e + e - decay
BIZZETI, Andrea;
2009
Abstract
A sample of 7253 K+/- -> pi(+/-)e(+)e(-)(gamma) decay candidates with 1.0% background contamination has been collected by the NA48/2 experiment at the CERN SPS, which allowed a precise measurement of the decay properties. The branching ratio in the full kinematic range was measured to be BR = (3.11 +/- 0.12) x 10(-7), where the uncertainty includes also the model dependence. The shape of the form factor W(z), where z = (M-ee/M-K)(2) was parameterized according to several models, and, in particular, the slope delta of the linear form factor W(z) = W-0(1 + delta z) was determined to be delta = 2.32 +/- 0.18. A possible CP violating asymmetry of K+ and K- decay widths was investigated, and a conservative upper limit of 2.1 X 10(-2) at 90% CL was established. (C) 2009 Elsevier B.V. All rights reserved.
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