The weak decay of helium hypernuclei
A [Lambda] hyperon replaces a neutron in a nucleus to form a hypernucleus via the [sup A]X(K[sup [minus]], [pi][sup [minus]]) [sub [Lambda]][sup A]X reaction at 750 MeV/c (Brookhaven Experiment 788). The free [Lambda] decay rates [Gamma]([Lambda] [yields] p[pi][sup [minus]]) and [Gamma]([Lambda] [yields] n[pi][sup 0]) are diminished due to Pauli blocking; but a non-mesonic decay mode, nucleon stimulated decay N[Lambda] [yields] Nn, is present and is detected via the energetic decay nucleon(s) ([approx] 400MeV/c). Measurements of the various hypernuclear decay rates [Gamma]([Lambda] [yields] p[pi][sup [minus]]), [Gamma]([Lambda] [yields] n[pi][sup 0]) and [Gamma]([Lambda]n [yields] nn) provides insight into the strong modification of the weak interaction such as the baryon-baryon [Delta]I =[1/2] rule. The hypernuclear state is isolated by momentum analysis of (K[sup [minus]], [pi][sup [minus]]) target reaction. Out-of-beam large volume scintillation detectors and tracking chambers axe used to make particle identification of the hypernuclear decay products by time-of-flight, dE/dx, and range. The kinetic energy of the decay neutrons are measured by time of flight using the large volume 100 element neutron detector system. The hypernuclear lifetime is directly measured using precision scintillator counters and tracking chambers. Measurements of the various decay rates as well as the total lifetime are discussed for [sub [Lambda]][sup 4]He.
- Research Organization:
- Carnegie-Mellon Univ., Pittsburgh, PA (United States)
- Sponsoring Organization:
- DOE; USDOE, Washington, DC (United States)
- DOE Contract Number:
- FG02-87ER40315
- OSTI ID:
- 6831977
- Report Number(s):
- DOE/ER/40315-196; ON: DE93003650
- Country of Publication:
- United States
- Language:
- English
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The weak decay of helium hypernuclei
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Related Subjects
663510 -- Nuclear Mass Ranges-- A=1-5-- (1992-)
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
BARYONS
BASIC INTERACTIONS
BOSONS
DATA
DECAY
ELEMENTARY PARTICLES
EVEN-EVEN NUCLEI
EXPERIMENTAL DATA
FERMIONS
HADRONS
HELIUM 4
HELIUM ISOTOPES
HYPERNUCLEI
INFORMATION
INTERACTIONS
ISOTOPES
LIFETIME
LIGHT NUCLEI
MESONS
NEUTRONS
NUCLEAR FRAGMENTS
NUCLEI
NUCLEONS
NUMERICAL DATA
PIONS
PIONS MINUS
PIONS NEUTRAL
PROBABILITY
PROTONS
PSEUDOSCALAR MESONS
SELECTION RULES
STABLE ISOTOPES
TIME-OF-FLIGHT METHOD
WEAK INTERACTIONS