Status of the UCN<b>τ</b> experiment

Pattie, R. W.; Callahan, Nathan; Cude-Woods, C.; Adamek, E.; Adams, M.; Barlow, D.; Blatnik, M.; Bowman, D. R.; Broussard, L. J.; Clayton, Steven; Currie, Scott; Dees, Eric; Ding, X.; Fellers, Deion Elgin; Fox, W.; Fries, E. M.; González, Francisco M.; Geltenbort, P.; Hickerson, K. P.; Hoffbauer, Mark A.; Hoffman, K.; Holley, Adam; Howard, D.C.; Ito, T. M.; Komives, A.; Liu, C.Y.; Makela, M.; Medina, J.; Morley, D. J.; Morris, C. L.; O’Connor, Thomas P.; Penttilä, S. I.; Ramsey, J.; Roberts, A.; Salvat, Daniel; Saunders, Alexander; Seestrom, S.J.; Sharapov, É. I.; Sjue, Sky; Snow, W. M.; Sprow, Aaron; Vanderwerp, J.; Vogelaar, B.; Walstrom, P. L.; Wang, Z.; Weaver, H.; Wexler, J.; Womack, T. L.; Young, A. R.; Zeck, B. A.

doi:10.1051/epjconf/201921903004

Cited by 8 publications

(11 citation statements)

References 14 publications

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“…Searches for a non-zero electric dipole moment of the neutron (nEDM), which are performed almost exclusively using UCN [5][6][7][8], probe new sources of time reversal symmetry violation [9,10] and may give clues to the puzzle of the matterantimatter asymmetry in the Universe [11,12]. The free neutron lifetime, which is measured using UCN [13,14] or beams of cold neutrons [15], is an important input parameter needed to describe Big-Bang nucleosynthesis. Measurements of neutron decay correlation parameters performed using UCN [16][17][18][19][20] as well as cold neutrons [21], along with measurement of the free neutron lifetime, test the consistency of the standard model of particle physics and probe what may lie beyond it [22].…”

mentioning

confidence: 99%

“…This was the first production UCN source based on superthermal UCN production. As the only operational UCN source in the US and as one of the two multi-experiment UCN facilities in the world (along with the ILL turbine source), it has provided UCN to various experiments including the UCNA [16][17][18][19][20], UCNB [32], and UCNτ [14] experiments as well as development efforts for the nEDM and Nab experiments at SNS [32,33].…”

mentioning

confidence: 99%

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Performance of the upgraded ultracold neutron source at Los Alamos National Laboratory and its implication for a possible neutron electric dipole moment experiment

Ito¹,

Adamek²,

Callahan³

et al. 2018

Phys. Rev. C

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The ultracold neutron (UCN) source at Los Alamos National Laboratory (LANL), which uses solid deuterium as the UCN converter and is driven by accelerator spallation neutrons, has been successfully operated for over 10 years, providing UCN to various experiments, as the first production UCN source based on the superthermal process. It has recently undergone a major upgrade. This paper describes the design and performance of the upgraded LANL UCN source. Measurements of the cold neutron spectrum and UCN density are presented and compared to Monte Carlo predictions. The source is shown to perform as modeled. The UCN density measured at the exit of the biological shield was 184(32) UCN/cm 3 , a four-fold increase from the highest previously reported. The polarized UCN density stored in an external chamber was measured to be 39(7) UCN/cm 3 , which is sufficient to perform an experiment to search for the nonzero neutron electric dipole moment with a one-standard-deviation sensitivity of σ(dn) = 3 × 10 −27 e·cm.

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mentioning

confidence: 99%

mentioning

confidence: 99%

Performance of the upgraded ultracold neutron source at Los Alamos National Laboratory and its implication for a possible neutron electric dipole moment experiment

Ito¹,

Adamek²,

Callahan³

et al. 2018

Phys. Rev. C

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“…[157] for more discussions). Several experiments are under construction to measure τ n with a precision better than 0.4 s and resolve the beam-bottle discrepancy [158,159], as well as to reach an accuracy level of 10 −4 in the λ measurement [160][161][162].…”

Section: Free Neutronmentioning

confidence: 99%

Radiative Corrections to Semileptonic Beta Decays: Progress and Challenges

Seng

2021

Particles

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We review some recent progress in the theory of electroweak radiative corrections in semileptonic decay processes. The resurrection of the so-called Sirlin’s representation based on current algebra relations permits a clear separation between the perturbatively-calculable and incalculable pieces in the O(GFα) radiative corrections. The latter are expressed as compact hadronic matrix elements that allow systematic non-perturbative analysis such as dispersion relation and lattice QCD. This brings substantial improvements to the precision of the electroweak radiative corrections in semileptonic decays of pion, kaon, free neutron and JP=0+ nuclei that are important theory inputs in precision tests of the Standard Model. Unresolved issues and future prospects are discussed.

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“…A large class of experiments employs neutrons with energy lower than the neutron optical potential of typical materials, i.e. 300 neV [7,8,[10][11][12][14][15][16][17][18][19][20][21]. These socalled ultracold neutrons (UCNs) can be trapped for many minutes in well-designed "neutron bottles" [17][18][19][20][21].…”

Section: Introductionmentioning

confidence: 99%

“…300 neV [7,8,[10][11][12][14][15][16][17][18][19][20][21]. These socalled ultracold neutrons (UCNs) can be trapped for many minutes in well-designed "neutron bottles" [17][18][19][20][21]. The gravitational interaction with a potential difference of 100 neV per meter rise plays important role in UCN storage and manipulation [14][15][16][17][18][19][20].…”

Section: Introductionmentioning

confidence: 99%

Helium film may greatly increase the storage time of ultracold neutrons in material traps

Grigoriev,

Dyugaev

2021

Preprint

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We propose a method to increase both the neutron storage time and the precision of its lifetime measurements by at least tenfold. The storage of ultracold neutrons (UCN) in material traps now provides the most accurate measurements of neutron lifetime and is used in many other experiments. The precision of these measurements is limited by the interaction of UCN with the trap walls. We show that covering of trap walls with liquid helium may strongly decrease the UCN losses from material traps. 4 He does not absorb neutrons at all. Superfluid He covers the trap walls by a thin film, ∼ 10 nm thick, due to the van der Waals attraction. However, this He film on a flat wall is too thin to protect the UCN from their absorption inside a trap material. By combining the van der Waals attraction with capillary effects we show that surface roughness may increase the thickness of this film much beyond the neutron penetration depth ∼ 33nm. Using liquid He for UCN storage requires low temperature T < 0.5 to avoid neutron interaction with He vapor, while the neutron losses because of the interaction with surface waves are small and can be accounted for using their linear temperature dependence.

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Status of the UCNτ experiment

Cited by 8 publications

References 14 publications

Performance of the upgraded ultracold neutron source at Los Alamos National Laboratory and its implication for a possible neutron electric dipole moment experiment

Performance of the upgraded ultracold neutron source at Los Alamos National Laboratory and its implication for a possible neutron electric dipole moment experiment

Radiative Corrections to Semileptonic Beta Decays: Progress and Challenges

Helium film may greatly increase the storage time of ultracold neutrons in material traps

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