Neutron lifetime, dark matter and search for sterile neutrino

Serebrov, A. P.; Samoilov, R. M.; Mitropolsky, I. A.; Gagarsky, A. M.

doi:10.48550/arxiv.1802.06277

2018

DOI: 10.48550/arxiv.1802.06277

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Neutron lifetime, dark matter and search for sterile neutrino

A. P. Serebrov¹,

R. M. Samoilov²,

I. A. Mitropolsky³

et al.

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Cited by 11 publications

(25 citation statements)

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“…This case has been already pointed to by Fornal and Grinstein [3]. The neutron separation energy in 11 Li of S n = 396 (13) keV is favorite for the search of the dark decay producing the unbound 10 Li which would promptly decay to 9 Li by emission of a neutron. So in fact the allowed energy window for the dark decay in this case is given by the two-neutron separation energy equal to 369.3 (6) keV.…”

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confidence: 54%

“…So in fact the allowed energy window for the dark decay in this case is given by the two-neutron separation energy equal to 369.3 (6) keV. However, the short half-life of 11 Li, T 1/2 = 8.75 ms, yields the branching ratio B X = 1.3 × 10 −7 . Unfortunately, this value is by three orders of magnitude smaller than the branching ratio for the β-delayed deuteron emission from 11 Li, B d = 1.30(13) × 10 −4 [7], which leads to the same final nucleus 9 Li.…”

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confidence: 89%

“…However, the short half-life of 11 Li, T 1/2 = 8.75 ms, yields the branching ratio B X = 1.3 × 10 −7 . Unfortunately, this value is by three orders of magnitude smaller than the branching ratio for the β-delayed deuteron emission from 11 Li, B d = 1.30(13) × 10 −4 [7], which leads to the same final nucleus 9 Li. In addition, the β-delayed proton emission of 11 Li, leading to 10 Li, is energetically allowed, although not yet observed.…”

mentioning

confidence: 99%

“…Unfortunately, this value is by three orders of magnitude smaller than the branching ratio for the β-delayed deuteron emission from 11 Li, B d = 1.30(13) × 10 −4 [7], which leads to the same final nucleus 9 Li. In addition, the β-delayed proton emission of 11 Li, leading to 10 Li, is energetically allowed, although not yet observed. Experimental disproval of this channel at the level of 10 −7 or lower, will be extremely difficult.…”

mentioning

confidence: 99%

“…Experimental disproval of this channel at the level of 10 −7 or lower, will be extremely difficult. Therefore, 11 Li can not be considered as a practical candidate for the nuclear dark decay.…”

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confidence: 99%

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Examining the possibility to observe neutron dark decay in nuclei

Pfützner

Riisager

2018

Phys. Rev. C

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As proposed recently by Fornal and Grinstein, neutrons can undergo a dark matter decay mode which was not observed before. Such a decay could explain the existing discrepancy between two different methods of neutron lifetime measurements. If such neutron decay is possible, then it should occur also is nuclei with sufficiently low neutron binding energy. We examine a few nuclear candidates for the dark neutron decay and we consider possibilities of their experimental identification. In more detail we discuss the case of 11 Be which appears as the most promising nucleus for the observation of the neutron dark decay. PACS numbers:The neutron lifetime remains one of the most remarkable open questions in fundamental physics [1,2]. After decades of experimental struggle two different experimental methods appear to yield two lifetime values with the discrepancy between them on the level of about 4.0σ. The first type of measurements, referred to as the bottle essentially counts the number of neutrons in the container as a function of time. In the second method, called the beam, one counts protons resulting from beta decay of known number of neutrons in the beam. On average, the latter method yields the longer neutron lifetime by about 1% [1]. Strictly speaking, however, both method measure different observables. While the bottle method provides the total lifetime of the neutron, the beam method is sensitive to the partial neutron lifetime related to beta decay. The former value being smaller indicates that other decay channels may contribute to the total lifetime. In a recent paper, Fornal and Grinstein [3] formulate a hypothesis that the neutron undergoes a yet unobserved decay mode involving dark sector particles in the final state. If such a new dark decay channel occurs with the branching ratio of 1%, it would explain the neutron lifetime puzzle. Fornal and Grinstein discuss the energy constrains for the dark decay and proceed by investigating a few theoretical scenarios for the postulated dark channel [3]. They observe that neutrons bound in nuclei can also decay by the dark channel, if allowed by energy conditions.In this paper we examine the possibility of nuclear dark neutron decay. First, we recall the definitions, energy conditions, and specify our assumptions. Then, a few nuclear candidates will be presented and their experimental prospects will be briefly discussed. Finally, the most promising case will be described in more detail.Let the sum of masses of particles in the final state of the free neutron dark decay be m X . From the stability of 9 Be, Fornal and Grinstein give the following condition * Electronic address: pfutzner@fuw.edu.pl for m X [3]:where the lower limit is the atomic mass difference of 9 Be and 8 Be, and the upper limit is the neutron mass m n . However, 8 Be is not bound and it promptly disintegrates into two α particles. In consequence, the lower limit for the m X is actually given by the mass difference of 9 Be and two α particles, which is 93 keV larger that the limit in Eq.1 [4]. Whe...

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confidence: 54%

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confidence: 89%

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confidence: 99%

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confidence: 99%

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confidence: 99%

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Examining the possibility to observe neutron dark decay in nuclei

Pfützner

Riisager

2018

Phys. Rev. C

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Exotic decay channels are not the cause of the neutron lifetime anomaly

et al. 2019

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Since long neutron lifetimes measured with a beam of cold neutrons are significantly different from lifetimes measured with ultracold neutrons bottled in atrap. It is often speculated that this "neutron anomaly" is due to an exotic dark neutron decay channel of unknown origin. We show that this explanation of the neutron anomaly can be excluded with a high level of confidence when use is made of our new result for the neutron decay β asymmetry. Furthermore, data from neutron decay now compare well with Ft-data derived from nuclear β decays.

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New physics searches in nuclear and neutron β decay

González–Alonso

Naviliat‐Cuncic

Severijns

2019

Progress in Particle and Nuclear Physics

246

282

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The status of tests of the standard electroweak model and of searches for new physics in allowed nuclear β decay and neutron decay is reviewed including both theoretical and experimental developments. The sensitivity and complementarity of recent and ongoing experiments are discussed with emphasis on their potential to look for new physics. Measurements are interpreted using a model-independent effective field theory approach enabling to recast the outcome of the analysis in many specific new physics models. Special attention is given to the connection that this approach establishes with high-energy physics. A new global fit of available β-decay data is performed incorporating, for the first time in a consistent way, superallowed 0 + → 0 + transitions, neutron decay and nuclear decays. The constraints on exotic scalar and tensor couplings involving left-or right-handed neutrinos are determined while a constraint on the pseudoscalar coupling from neutron decay data is obtained for the first time as well. The values of the vector and axial-vector couplings, which are associated within the standard model to V ud and g A respectively, are also updated. The ratio between the axial and vector couplings obtained from the fit under standard model assumptions is C A /C V = −1.27510(66). The relevance of the various experimental inputs and error sources is critically discussed and the impact of ongoing measurements is studied. The complementarity of the obtained bounds with other low-and high-energy probes is presented including ongoing searches at the Large Hadron Collider.

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Neutron lifetime, dark matter and search for sterile neutrino

Cited by 11 publications

References 9 publications

Examining the possibility to observe neutron dark decay in nuclei

Examining the possibility to observe neutron dark decay in nuclei

Exotic decay channels are not the cause of the neutron lifetime anomaly

New physics searches in nuclear and neutron β decay

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