Weak decays of {sub {lambda}}{sup 4}He

Journal Article · Sat Sep 15 00:00:00 EDT 2007 · Physical Review. C, Nuclear Physics

DOI:https://doi.org/10.1103/PHYSREVC.76.035501· OSTI ID:21064378

Parker, J D; Athanas, M J; Barnes, P D; Diebold, G; Franklin, G B; Quinn, B; Rozon, F; Schumacher, R A; Sukaton, I; Zeps, V J ^[1]; Bart, S; Chrien, R; Pile, P; Sawafta, R; Sutter, R ^[2]; Bassalleck, B ^[3]; Johnston, K ^[4]; Stearns, R ^[5]; Szymanski, J J ^[6]

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1. Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 (United States)
2. Brookhaven National Laboratory, Upton, New York 11973 (United States)
3. University of New Mexico, Albuquerque, New Mexico 87131 (United States)
4. University of Houston, Houston, Texas 77004 (United States)
5. Vassar College, Poughkeepsie, New York 12604 (United States)
6. Indiana University Cyclotron Facility, Bloomington, Indiana 47408 (United States)

We measured the lifetime and the mesonic and nonmesonic decay rates of the {sub {lambda}}{sup 4}He hypernucleus. The hypernuclei were created using a 750 MeV/c momentum K{sup -} beam on a liquid {sup 4}He target by the reaction {sup 4}He (K{sup -},{pi}{sup -}){sub {lambda}}{sup 4}He. The {sub {lambda}}{sup 4}He lifetime was directly measured using protons from {lambda}p{yields}np nonmesonic decay (also referred to as proton-stimulated decay) and was found to have a value of {tau}=245{+-}24 ps. The mesonic decay rates were determined from the observed numbers of {pi}{sup -}'s and {pi}{sup circle}'s as {gamma}{sub {pi}{sup -}}/{gamma}{sub tot}=0.270{+-}0.024 and {gamma}{sub {pi}}/{gamma}{sub tot}=0.564{+-}0.036, respectively, and the values of the proton- and neutron-stimulated decay rates were extracted as {gamma}{sub p}/{gamma}{sub tot}=0.169{+-}0.019 and {gamma}{sub n}/{gamma}{sub tot}{<=}0.032 (95% CL), respectively. The effects of final-state interactions and possible three-body {lambda}NN decay contributions were studied in the context of a simple model of nucleon-stimulated decay. Nucleon-nucleon coincidence events were observed and were used in the determination of the nonmesonic branching fractions. The implications of the results of this analysis were considered for the empirical {delta}I=(1/2) rule and the decay rates of the {sub {lambda}}{sup 4}H hypernucleus.

• OSTI ID: 21064378
• Journal Information: Physical Review. C, Nuclear Physics, Journal Name: Physical Review. C, Nuclear Physics Journal Issue: 3 Vol. 76; ISSN 0556-2813; ISSN PRVCAN
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
BRANCHING RATIO
FINAL-STATE INTERACTIONS
HELIUM 4
HELIUM 4 TARGET
HYPERNUCLEI
KAON MINUS REACTIONS
LAMBDA BARYONS
LIFETIME
MEV RANGE
NEUTRONS
NUCLEAR DECAY
PARTICLE DECAY
PIONS MINUS
PROTONS
THREE-BODY PROBLEM