Search for a heavy neutrino in the β-decay of 35S

Datar, V. M.; Baba, C.V.K.; Bhattacherjee, S.K.; Bhuinya, C. R.; Roy, A.

doi:10.1038/318547a0

Cited by 65 publications

(14 citation statements)

References 7 publications

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“…In the following two negative results, [11] and [,,19], are not studied, because it is not clear whether shape factors were used or not, and because their shape factor seems significantly not flat between the kink and the end point. The follow up of [,19], [241, contains a quadratic shape factor so the analysis of Sects.…”

Section: Evidence For a Heavy Neutrinomentioning

confidence: 87%

Statistical issues in the 17-keV neutrino experiments

Bonvicini

1993

Z. Physik A - Hadrons and Nuclei

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Section: Evidence For a Heavy Neutrinomentioning

confidence: 87%

Statistical issues in the 17-keV neutrino experiments

Bonvicini

1993

Z. Physik A - Hadrons and Nuclei

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“…While all reported evidence for a 17 keV neutrino is based on experiments with Si and Ge detectors (notwithstanding the negative results of Refs. [14,15]), no evidence for a heavy neutrino in the mass range of about 5-50 keV has been reported from magnetic spectrometer experiments [1][2][3][4][5][6][7]. The subject has been reviewed recently by Hime [16], Boehm and Vogel [17], and Morrison [18].…”

Section: New Limits On the 17 Kev Neutrinomentioning

confidence: 97%

New limits on the 17 keV neutrino

et al. 1992

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We present results of new measurements of the p spectrum of ^^S, using the Caltech double-focusing, iron-free p spectrometer. Our data show no evidence for a heavy neutrino with a mass between 12 and 22 keV admixed to the usual light neutrino. In particular, we rule out, at the do level, a 17 keV neutrino admixed at 0.85%, and give an upper limit (90% C.L.) of 0.2% for such a neutrino admixture. To demonstrate that our experiment is sensitive to spectral features such as those from heavy neutrinos we have induced an artificial kink by means of an absorber foil covering part of the source.PACS numbers: 23.40. Bw, 14.60.Gh, 27.30.+t In recent years, a number of studies using magnetic spectrometers have aimed at measuring, with high precision, the shapes of p spectra in the decays of ^^S [1-4] and ^^Ni [5][6][7]. These experiments were triggered in response to a paper by Simpson in 1985 [8] in which evidence is presented for a heavy neutrino with a mass of 17 keV. This claim has been reiterated in subsequent papers by Hime and Simpson [9], by Hime and Jelley [10], and by others [11-13]. While all reported evidence for a 17 keV neutrino is based on experiments with Si and Ge detectors (notwithstanding the negative results of Refs. [14,15]), no evidence for a heavy neutrino in the mass range of about 5-50 keV has been reported from magnetic spectrometer experiments [1-7]. The subject has been reviewed recently by Hime [16], Boehm and Vogel [17], and Morrison [18].In an effort to shed light on the controversy over the existence of a 17 keV neutrino we have reexamined the ^^S p spectrum with the help of the Caltech doublefocusing spectrometer. This spectrometer had been employed already in 1985 for a similar heavy neutrino search [2], albeit with a different detector (different backscatter corrections and, consequently, different shape factor). In our recent study we measure the magnetic field rather than the current and we pay careful attention to possible systematic effects. In addition, we demonstrate the sensitivity of our apparatus with the help of a simulated "kink" feature. A preliminary communication was presented in Ref. [4].The 35-cm-radius, iron-free double-focusing yfln magnetic spectrometer at Caltech (momentum resolution 0.27%) employed at its focus a silicon surface barrier detector cooled by Peltier elements to approximately 5°C. Its energy spectrum is shown in Fig. 1 (top); the energy resolution between 120 and 160 keV is =^4 keV FWHM. The detector has an active surface layer of 300 //m and an area of 4 mmx25 mm. A pulser was used to monitor the stability of the electronics.The spectrometer was calibrated using a 100-/iCi ^''Co source vapor deposited onto a 0.9-/im-thick Mylar backing (gold coated). Two ^^S sources were prepared using a technique that is a combination of vapor deposition and aqueous deposition. A layer of barium was first deposited on the gold-coated Mylar through a mask in the shape of the desired source (2 mmx20 mm). An aqueous solution of ammonium sulfate containing carrier-free ...

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“…If one includes such an overall piece in the data analysis (as done by a number of experiments; e.g., see Ref. [2]), the correction due to the screened Fermi function from the Hulthen-Klein-Gordon equation and other effects may be absorbed. Since the analyses of both 3 5~ measurements of Guelph and Oxford and 6 3~i measurement of Oxford [3,4] do not contain C ( E ) , the impact of different Fermi functions should be carefully examined.…”

Section: R759mentioning

confidence: 99%

“…It affects the data analysis in the Kuri plot, and the shape function defined as If the neutrino is truly massless, the Kurie plot should be a linear function of Q -T following Eqs. (1) and (2). The shape function in (3) should be unity when proper normalization is taken for a fixed end point Q.…”

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confidence: 99%

Fermi theory of nuclearβdecay and heavy neutrino searches

1993

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We examine the data analysis of nuclear 1 3 decay of 3~, 14C, 3 5~, and 6 3~i , using a relativistic Fermi function for a Hulthen screened field. This Fermi function does not differ much from that used by Hime, Jelley, and Simpson in the cases of light nuclei, but in the cases of sulfur and nickel reduces significantly the claimed spectral excess and, hence, the mixing of the heavy neutrino. We also discuss radiative corrections to 35S data. PACS numberk): 23.40. Bw, 12.15.Ff, 23.40.Hc, 29.30.Dn Recent controversy regarding the existence of a heavy neutrino in nuclear p decay has attracted much attention [I-71. A t issue is the reported spectral excess in P decay which is interpreted by authors of Refs. [1,3,4] as the evidence of a 17-keV neutrino with a 0.8% to 1.6% mixing. Since the claimed mixing is of the order 1% and since many factors are involved in the data analysis, corrections of the same order ( > 0.1%) should be addressed and fully investigated.The dimensionless Fermi function is an important factor affecting p decay. It plays an important role in the decay process, and its screening is important especially in the case of heavy nuclei or low energies [8]. In this note we examine the effect of an alternative Fermi function on different decay processes in the energy regions of interest relevant to the reported heavy-neutrino signal [9]. In particular, we use a relativistic Fermi function obtained by Durand [8] based on an exact solution to the KleinGordon equation with a Hulthen potential for the screened field and compare it to the screened Fermi functions employed by Hime, Jelley, and Simpson [1,3,4]. It is found that while the two different approaches do not differ significantly in the cases of 3~ and 14c, our results reduce the spectral excess by about 0.3% and 1% for 3 5~ and 6 3~i , respectively. This undoubtedly calls for further investigation regarding theoretical uncertainties which are larger than 0.1% in order to fully understand the issue of heavy-neutrino mixing. The correction in this Rapid Communication makes the excess signal in the 6 3~i data of Ref.[4] totally vanish.The screened Fermi function was first studied by Rose [lo] using the W K B method. Further calculations have been done since then, based both on exactly solvable models [8,11] and on approximation methods [12,13]. In allowed nuclear / 3 decay, one can write the decay spectra, assuming only a zero mass neutrino, as where p, E, T, and Q are the electron momentum, total energy, kinetic energy, and its maximum allowed kinetic energy, and Z is the atomic number for the daughter nucleus. The function R (E) is for radiative corrections which we will briefly discuss toward the end. The shape correction C (E) is usually not large [14]. P, is the probability for a final state n with energy E,. For the purpose of this paper we take n = 1, P, =1, and E, -0. We shall concentrate on F ( Z , E). It affects the data analysis in the Kuri plot, and the shape function defined as If the neutrino is truly massless, the Kurie plot should be...

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Search for a heavy neutrino in the β-decay of 35S

Cited by 65 publications

References 7 publications

Statistical issues in the 17-keV neutrino experiments

Statistical issues in the 17-keV neutrino experiments

New limits on the 17 keV neutrino

Fermi theory of nuclearβdecay and heavy neutrino searches

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