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(+/-)->pi(+/-)e(+)e(-) decay
LAMANNA, GIANLUCA;COSTANTINI, FLAVIO;GIUDICI, SERGIO;PIERAZZINI, GIUSEPPE;SOZZI, MARCO STANISLAO;
2009-01-01
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.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
