Summary
Negative muon star production in nuclear emulsion is studied, with particular reference to its use in determining pion contamination in beams with π/μ ≲ 10−3. Of 9.3 · 104 muon endings examined (1.95±0.07)% gave visible stars. The existence of muon stars of ≥ 3 prongs is ascertained, and the fraction of endings giving such stars is found to be (5.8±1.2) · 10−4. The results are compared and found in agreement with a simple model of muon capture through the weak interaction with a subsequent nuclear excitation energy of about (15 ÷ 20) MeV. Evidence for capture near the nuclear surface is found. The results lead to a multiprong star detection efficiency for muons relative to pions of (1.7±0.4) · 10−3, which combined with exploitation of the range difference of the two kinds of particles permits contamination measurements much simpler than those performed by counters, and yet just as accurate.
Riassunto
Si studia la produzione di stelle muoniche negative in emulsione nucleare, con particolare riferimento al loro uso nella determinazione della contaminazione pionica in fasci con π/μ <10−3. Di 9.3 · 104 terminazioni muoniche esaminate il (1.95±0.07)% diedero stelle visibili. Si è accertata l’esistenza di stelle muoniche con ≥ 3 rami, e si trova che la frazione di terminazioni che danno queste stelle è (5.8±1.2) · 104. Facendo un confronto dei risultati si trova che concordano con un semplice modello di cattura di muoni tramite l’interazione debole con una successiva energia di eccitazione nucleare di circa (15 ÷ 20) MeV. Si trovano prove della cattura presso la superficie nucleare. I risultati portano ad una efficienza di rivelazione delle stelle a molti rami per i muoni rispetto ai pioni di (1.7±0.4) · 10−3, che combinata allo sfruttamento della differenza di percorso delle due particelle permette misure della contaminazione molto più semplici di quelle effettuate con contatori e pure altrettanto accurate.
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Work supported in part by the National Science Foundation.
This work was financed in part by the National Science Foundation, and in part by a grant from the Natural Science Committee of Vanderbilt University.
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Kotelchuck, D. Negative muon star production in nuclear emulsion. Nuovo Cim 34, 27–39 (1964). https://doi.org/10.1007/BF02725866
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DOI: https://doi.org/10.1007/BF02725866