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Measurement of the Ke2+ Branching Ratio

Journal Article · · Physical Review
 [1];  [1];  [1];  [2];  [2];  [2];  [2];
  1. Univ. of Pennsylvania, Philadelphia, PA (United States)
  2. Princeton Univ., NJ (United States)
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The Ke2+ branching ratio has been measured in a spark-chamber and counter experiment at the Princeton-Pennsylvania accelerator. A 𝐾+ beam which yielded an average of 500 stopped, identified 𝐾+ mesons per second was used. Particles which left the stopping region approximately at right angles to the incident beam passed through a series of six thin-plate chambers situated in a 7.5-kG magnetic field which permitted measurement of the particle momentum with a standard deviation of 1.9%. Positrons were identified by a threshold gas Čerenkov counter placed behind the magnetic field. A thick-plate spark chamber was placed behind the Čerenkov counter to permit observation of a particle emerging from that counter and measurement of the particle's total range. The time interval between the 𝐾+ stop and decay was recorded for each event. Discrimination against background events, arising principally from the Kμ2+ decay mode, was provided by selection criteria on momentum, range, the time between the 𝐾+ stop and decay, and by a requirement that the measured position of the track at the entrance to the thick-plate chamber match the extrapolated momentum chamber track. After applying these criteria, we obtain a total of seven events in the momentum interval 242-252 MeV/c in which positrons from Ke2+ should fall, with 2.8 of these events estimated to be background. This gives a Ke2+ branching ratio of ($$2.1^{+1.8}_{−1.3}$$)×10−5, in agreement with the prediction of 𝑉 −𝐴 theory, which, including a radiative correction, is 1.44×10−5.

Research Organization:
Univ. of Pennsylvania, Philadelphia, PA (United States)
Sponsoring Organization:
USDOE; US Atomic Energy Commission (AEC)
NSA Number:
NSA-21-018888
OSTI ID:
4454240
Report Number(s):
NYO--2171-212
Journal Information:
Physical Review, Journal Name: Physical Review Journal Issue: 5 Vol. 154; ISSN 0031-899X
Publisher:
American Physical Society (APS)Copyright Statement
Country of Publication:
United States
Language:
English

References (9)

Positron spectrum in the K+ → π0 + ν decay journal September 1964
Positron momentum spectrum and branching ratio of K+e3 journal May 1966
Chirality Invariance and the Universal Fermi Interaction journal March 1958
Theory of the Fermi Interaction journal January 1958
Branching Ratio of the Electronic Mode of Positive Pion Decay journal September 1960
Study of the Decayπ→e+ν journal March 1964
Electron Decay of the Pion journal October 1958
βDecay of the Pion journal October 1958
Radiative Corrections to Pion Beta Decay journal December 1958

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Related Subjects

BRANCHING RATIO
COUNTERS
DECAY
INTERACTIONS
KAONS
KAONS-PLUS
MEASUREMENT
N34120* --Physics (High Energy)--Particle Interactions & Properties (Experimental)--Weak
NEUTRINOS
POSITRONS
SPARK CHAMBERS
V-A THEORY
WEAK INTERACTIONS