An array of four 87 Rb vector magnetometers are used to detect nuclear quadrupole resonance (NQR) signals in an unshielded environment at 1 MHz. With a baseline of 25 cm, the length of the array, radio-frequency interference mitigation (RFIM) is also demonstrated; a radio-station signal is suppressed by a factor of 20 without degradation to the signal of interest. With these compact sensors, in which the probe beam passes through twice, the fundamental limit to detection sensitivity is found to be photon shot noise. More passes of the probe beam overcome this limitation. With a sensor of similar effective volume, 0.25 cm 3 , but 25 times more passes, the sensitivity is improved by an order of magnitude to 1.7 ± 0.2 fT/ √ Hz.

We have observed a signal of 55 isolated /-conversion pairs produced in a wide-band neutrino beam using the Fermilab 15-ft bubble chamber filled with a heavy Ne-H2 mixture. The signal is consistent with coherent neutral-current single-/* 0 production followed by decay of the /r° with one of the decay ys being lost. This signal corresponds to a rate of (2.0 ± 0.4) x 10~* 4 of the total v^ charged-current cross section at our average E v of 20 GeV. From this result, we obtain a value of /J~0.98±0.24 for the weak-neutral-current isovector axial-vector coupling.PACS numbers: 13.15.Cj Neutral-current coherent K° production, first suggested by Nachtmann 1 and Lackner 2 and later refined by Rein and Sehgal, 3 occurs predominantly through the interaction of the isovector axial-vector current, the longitudinal part of which behaves like a /r° and scatters elastically from a nucleus exchanging a pomeronlike particle. The importance of coherent x° production is that a precise measurement of the cross section can provide a direct measurement of the isovector axial-vector neutral-current coupling. Using the notation of Hung and Sakurai, 4 one can write the axial-vector weak current as Ja^PAlT 1 + SAl' m0 , where P is the isovector axialvector coupling constant and S is the isoscalar axialvector coupling constant. The standard model of electroweak interactions predicts that ^ = 1 and 5=0.Evidence for neutral-current coherent single-/r° production by neutrinos has been reported by three groups. 5 " 8 Weak coherent x° production was first observed by the Aachen-Padova group, 5 who reconstructed K°ys at an average neutrino energy of 2 GeV. This has been confirmed by Gargamelle data with single fs at a similar low neutrino energy. The third group used a high-energy neutrino beam along with a highly segmented calorimeter. They were forced to rely on a statistical method to identify candidate events. We have directly observed a signal of isolated photon-conversion pairs in a heavy-liquid bubble chamber exposed to a wide-band neutrino beam «£' v >=20 GeV). This signal can be explained by coherent TT 0 production with only one of the 7t° decay photons being observable.The data for the present experiment were taken in the Fermilab 15-ft bubble chamber filled with a heavy Ne-H2 mixture and exposed to a single horn-focused wide-band v^ beam. The heavy neon mixture is ideal for identifying electrons and /s since its radiation length is -40 cm.In the heavy mixture a n can sometimes appear to be a single y. This occurs when a y either fails to convert in the visible volume or converts inside the radiation shower caused by the earlier conversion of the other y. The short conversion length in our liquid ensures that the probability for a ;r°-decay y to convert in the visible volume is large ( -95%); however, as the energy of the it 0 increases, the opening angle between the two decay fs decreases thus increasing the probability for the two conversions to overlap. From examining a large sample of converted y's, criteria were deduced concerning...

to be pub-Various authors have investigated 1 the possibility of neutrino oscillations, i.e., the time-dependent mixing between different types of neutrinos. These oscillations can only occur if there is a nonzero mass difference between the neutrinos involved and the lepton numbers of the neutrinos are not rigorously conserved. With three or more neutrino types, the situation is quite complex, and depends on many parameters. In this paper, we consider only oscillations between two types of neutrinos at a time. In this case, the observed neutrino types, say v a and ^0, are quantum mechanical mixtures of the neutrino lished.14 Theoretieal error for a" 1 (a e ) is the combined error of C 3 and C 4 . The effect of composite structure of leptons on the muonium hfs is at most of the order of 10" n of the hfs interval and hence completely negligible; G. P. Lepage, private communication. mass eigenstates, v 1 and v 2 :where 9 is the mixing angle between the two types of neutrinos. The probability of the appearance of a neutrino v B , when initially a neutrino v a was created, is P(^a^^0)=sin 2 (26')sin 2 (1.27Am 2 Z/£),where Aw2 2 = m/ -m 2 2 is in units of electronvolts squared, E is the neutrino energy in megaelec-

I. INTRODUCTION. Neutral strange particle production in charged-current v interactions have been studied in the Fermilab 15-foot neon bubble chamber. The reactions studied included: i/ + Ne-> iu"K°X, K°-> x + n~ 2279 decays v + Ne-> ,u"A X, A°-> *•" p 1843 decays v + Ne-> p.'K X, A 0-> JT + p 93 decays Associated production is expected to be the major source of strange particles in charged-current neutrino interactions since the d-quark is the only valence quark the neutrino interacts with, and makes a strange quark only via a Cabibbo disfavored process; strange quarks must be ejected from the sea. Other processes, such as charm production and interactions with sea quarks are expected to be small. The sample described here, from 61,800 charged-current events, is used to provide insight into these ideas. Other topics include: UlSTmBUTTON OF THIS DOCUMENT t& Strange Particle Production v 2%^ R. Piano/Rutgers U.

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