Evidence for new interference phenomena in the decay D+→K−π+μ+ν

Physical Review Letters, 2001

Using a large sample of photoproduced charm mesons from the FOCUS experiment at Fermilab (FNAL-E831), we observe the decay D 0 → K + π − with a signal yield of 149 ± 31 events compared to a similarly cut sample consisting of 36 760±195 D 0 → K − π + events. We use the observed ratio of D 0 → K + π − to D 0 → K − π + (0.404 ± 0.085 ± 0.025)% to obtain a relationship between the D 0 mixing and doubly Cabibbo suppressed decay parameters. 13.25.Ft, 12.15.Ff, 14.40.Lb Typeset using REVT E X

Physics Letters B, 1999

The NA48 experiment at CERN has performed a new measurement of direct CP violation, based on data taken in 1997 by simultaneously collecting K L and K S decays into 0 0 and + . The result for the CP violating parameter Re (" 0 =") is (18:5 4:5(stat) 5:8(syst)) 10 4 .

Physical Review Letters, 2005

International Journal of Modern Physics A, 2001

We have examined the physics and the experimental feasibility of studying various kaon decay processes in which the polarization of a muon in the final state is measured. Valuable information on CP violation, the quark mixing (CKM) matrix, and new physics can be obtained from such measurements. We have considered muon polarization in KL→μ+μ- and K→πμ+μ- decays. Although the effects are small, or difficult to measure because of the small branching ratios involved, these studies could provide clean measurements of the CKM parameters. The experimental difficulty appears comparable to the observation of [Formula: see text]. New sources of physics, involving nonstandard CP violation, could produce effects observable in these measurements. Limits from new results on the neutron and electron electric dipole moment, and [Formula: see text] in neutral kaon decays, do not eliminate certain models that could contribute to the signal. A detailed examination of muon polarization out of the decay...

1997

The CPLEAR experiment measured time-dependent decay-rate asymmetries of K 0 and K 0 decaying to + 0 in order to study the interference between the decay amplitudes of K 0 S-either CP-violating or CP-conserving-and the CP-conserving K 0 L decay amplitude. From the analysis of the complete data set we find for the CP-violating parameter + 0 , Re + 0 = 2 7 stat. +4 1 syst. 10 3 ; Im + 0 = 2 9 stat. +2 1 syst. 10 3 and for the CP-conserving parameter , Re = +28 7 stat. 3 syst. 10 3 ; Im = 10 8 stat. 2 syst. 10 3 : From the latter, the branching ratio of the CPconserving K 0 S ! + 0 decay is deduced to be B =

Zeitschrift f�r Physik, 1963

The enhancement of the K+~-decay compared to the K~ is discussed on the basis of the I~l = 89

2009

Physical Review Letters, 2002

Additional evidence for the rare kaon decay K + → π + νν has been found in a new data set with comparable sensitivity to the previously reported result. One new event was observed in the pion momentum region examined, 211 < P < 229 MeV/c, bringing the total for the combined data set to two. Including all data taken, the backgrounds were estimated to contribute 0.15 ± 0.05 events.

Physics Letters B, 2003

The radiative decay K + → π + π 0 γ (K π2γ) has been measured with stopped positive kaons. A K π2γ sample containing 4k events was analyzed, and the K π2γ branching ratio of the direct photon emission process was determined to be [6.1 ± 2.5(stat) ± 1.9(syst)]×10 −6. No interference pattern with internal bremsstrahlung was observed.

Physical Review D, 2001

Using data from the E791 fixed-target hadroproduction experiment at Fermilab we have studied the Cabibbo-favored but phase-space suppressed decay, D 0 → K − K − K + π +. We find the decay rate for this mode to be (0.54 ± 0.16 ± 0.08) × 10 −2 times that for the normalization mode D 0 → K − π − π + π +. We observe a clear signal for D 0 → φK − π + which is consistent with producing 0.7 ± 0.3 of the D 0 → K − K − K + π + signal. In the context of simple models, we use our measurements to estimate the importance of decay amplitudes that produce extra quark-antiquark pairs from the vacuum relative to those that do not.

2011