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We have measured the branching ratio for K: t p + p -using our full data set obtained during running periods in 1988, 1989, and 1990. The total number of p + p -candidates after a background subtraction is 707, which represents the largest sample to date of this rare decay mode. Our result is B ( K~ t p'p-) = (6.86 z t 0.37) x 10-', which is consistent with earlier results and very near the 'Present address:

Gaussian pulse shaping is used in digital communication systems like DECT, GSM, WLAN to minimize the out of band spectral energy. The baseband rectangular pulse stream is passed through a lter with a Gaussian impulse response before frequency modulating the carrier. Traditionally this is done by storing the values of the pulse shape in a ROM and converting it to an analog waveform with a DAC followed by a smoothing lter. This paper explores a fully analog implementation of an integrated Gaussian pulse shaper, which can result in a reduced power consumption and chip area. INTRODUCTIONGaussian pulse shaping of the baseband pulse stream is resorted to in digital communication systems like DECT and GSM in order to limit the spectral energy outside the transmission band. Gaussian Frequency Shift Keying GFSK 1 is a scheme where a Gaussian ltered pulse stream is used to frequency modulate the carrier. Conceptually, this is done by passing the baseband rectangular pulse stream with values in f,1; 1g through a lter with a Gaussian impulse response. The same can be thought of as adding or subtracting delayed versions of the unit pulse one bit wide pulse of unit amplitude response of the Gaussian lter depending on the sign of the input bit. The resulting smoothed" stream is fed to a voltage controlled oscillator VCO as shown in Fig. 1. Traditionally, this pulse shaping is done digitally. In order to implement the system, the ideal unit pulse response which extends from ,1 to +1 has to be truncated to some nite duration. The samples of the truncated step response are stored in a ROM. A DAC converts this digital data to a staircase waveform which is smoothed by a continuous time lter and fed to the VCO Fig. 2.In this paper, we describe a more direct realization of Fig. 1, using a continuous time lter whose impulse response is approximately Gaussian. We present the design of this lter and show that in many cases, the complexity of this lter is the same as that of the smoothing lter used in the digital approach. E ectively, the ROM and the DAC can be eliminated from Fig. 2, resulting in a reduction in the power consumption and chip area.In the next section, we brie y discuss the GFSK system of Fig. 1. In section 3., we consider the design issues in a digital pulse shaping scheme. In section 4., we derive the continuous time Gaussian pulse shaping lter and present some simulation results demonstrating its suitability. Section 5. deals with the implementation of the pulse shaper in a 2 m n well CMOS process and the measurement results.A quadrature modulation scheme to realize the same function as Fig. 1 can be derived. In this paper, we consider only the scheme shown in Fig. 1. GAUSSIAN FREQUENCY SHIFT KEYING GFSKThe output of the system shown in Fig DIGITAL PULSE SHAPINGThe block diagram of a digital pulse shaping system is shown in Fig. 2. The input bit stream is fed into a shift register, whose length is equal to the number of bit durations over which the unit pulse response extends for BT b = 0:5, this is 3. The RO...

In a search for the decay K\ -> e + e~, no candidates have been observed. We determine the sensitivity from the detected number of CP-violating K^ -• 7r + 7r~ decays and place a 90% confidence level upper limit on the branching ratio of B(K\ -• e + e~, \MK -M ee \ < 6 MeV/c 2 ) < 4.1 x 10 -11 . This result is a significant improvement over previous measurements, although still above the standard model prediction of 3 x 10~