A search for neutron to mirror-neutron oscillations using the nEDM apparatus at PSI

Abel, C.; Ayres, N. J.; Ban, G.; Bison, G.; Bodek, K.; Бондар, В. М.; Chanel, E.; Chiu, P.-J.; Crawford, Christopher; Daum, M.; Dinani, R. Tavakoli; Emmenegger, S.; Flaux, P.; Ferraris-Bouchez, L.; Griffith, William C.; Grujić, Zoran; Hild, Nora; Kirch, K.; Koch, H.-C.; Koss, P.; Kozela, A.; Krempel, J.; Lauss, B.; Lefort, T.; Leredde, A.; Mohanmurthy, Prajwal; Naviliat‐Cuncic, O.; Pais, D.; Piegsa, F. M.; Pignol, G.; Rawlik, M.; Rebreyend, D.; Rienäcker, I.; Ries, D.; Roccia, S.; Rozpędzik, D.; Schmidt-Wellenburg, P.; Severijns, N.; Thorne, Jacob; Weis, A.; Wursten, E.; Zejma, J.; Zsigmond, G.

doi:10.1016/j.physletb.2020.135993

“…The NiMo-coated aluminum guide inserts have a small surface fraction, and were assumed to be highly polished and thus not to increase the overall fraction of diffuse reflections above 2%. For the loss-per-bounce parameter of the precession chambers, we use a value of 2.8 × 10 −4 , extracted from storage measurements with the single chamber [32] (with a 1σ error added) . This was very close to the values reported in [33] for DLC (on aluminum foil at 300 K), and in [34] for dPS.…”

Section: Ucn Counts Nmentioning

confidence: 99%

The design of the n2EDM experiment

Ayres

¹

,

Ban

²

,

Bienstman

³

et al. 2021

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We present the design of a next-generation experiment, n2EDM, currently under construction at the ultracold neutron source at the Paul Scherrer Institute (PSI) with the aim of carrying out a high-precision search for an electric dipole moment of the neutron. The project builds on experience gained with the previous apparatus operated at PSI until 2017, and is expected to deliver an order of magnitude better sensitivity with provision for further substantial improvements. An overview is of the experimental method and setup is given, the sensitivity requirements for the apparatus are derived, and its technical design is described.

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“…This phenomenon may manifest in neutron disappearance (n → n ) and regeneration (n → n → n) experiments perfectly accessible to present experimental capabilities [18,22]. In fact, several dedicated experiments were performed [23][24][25][26][27][28][29], and it is rather intriguing that some of them show anomalous deviations from null hypothesis indicating to τ nn ∼ 20 s or so [28,30].…”

mentioning

confidence: 99%

“…Namely, for t 1, oscillations can be averaged and one gets P nn = 2ε 2 nn / 2 , P nn = 2ε 2 nn / 2 and P nn = P nn P nn = 4ε 2 nn ε 2 nn / 4 . Independent limits on oscillation times can be obtained from dedicated experiments [23][24][25][26][27][28][29] searching for anomalous losses of ultra-cold neutrons (UCN) in different magnetic fields. In the presence of both n − n and n − n transitions, the neutron disappearance probability P nn + P nn is proportional to the sum ε 2 nn + ε 2 nn .…”

mentioning

confidence: 99%

“…Under the minimal hypothesis (B = 0), experiments measuring the UCN losses in the conditions of small ( t 1) and large ( t 1) magnetic fields [23][24][25][26][27][28][29] give rather stringent limits on the effective time τ . Namely, experiments [24,26] performed at the ILL by Serebrov's group give a combined lower bound τ > 448 s (90% CL) [26].…”

mentioning

confidence: 99%

“…|B − B | < 0.1 mG for t = 0.1 s), oscillation probabilities become maximal. Namely, neglecting contributions of + dependent terms in (22) we get: For non-vanishing B , the limits on the effective oscillation time τ were obtained by experiments [26][27][28][29] which measured the UCN loss rates for different values and orientations of magnetic field B. Since the neutron disappearance probability is contributed by both n − n and n − n oscillations, these experiments measure the sum of probabilities P nn + P nn .…”

mentioning

confidence: 99%

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A possible shortcut for neutron–antineutron oscillation through mirror world

Berezhiani

¹

2021

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Existing bounds on the neutron-antineutron mass mixing, $$\epsilon _{n{\bar{n}}} < \mathrm{few} \times 10^{-24}$$ ϵ n n ¯ < few × 10 - 24 eV, impose a severe upper limit on $$n - {\bar{n}}$$ n - n ¯ transition probability, $$P_{n{\bar{n}}}(t) < (t/0.1 ~\mathrm{s})^2 \times 10^{-18}$$ P n n ¯ ( t ) < ( t / 0.1 s ) 2 × 10 - 18 or so, where t is the neutron flight time. Here we propose a new mechanism of $$n- {\bar{n}}$$ n - n ¯ transition which is not induced by direct mass mixing $$\epsilon _{n{\bar{n}}}$$ ϵ n n ¯ but is mediated instead by the neutron mass mixings with the hypothetical states of mirror neutron $$n'$$ n ′ and mirror antineutron $${{\overline{n}}} '$$ n ¯ ′ . The latter can be as large as $$\epsilon _{nn'}, \epsilon _{n\bar{n}'} \sim 10^{-15}$$ ϵ n n ′ , ϵ n n ¯ ′ ∼ 10 - 15 eV or so, without contradicting present experimental limits and nuclear stability bounds. The probabilities of $$n-n'$$ n - n ′ and $$n-\bar{n}'$$ n - n ¯ ′ transitions, $$P_{nn'}$$ P n n ′ and $$P_{n\bar{n}'}$$ P n n ¯ ′ , depend on environmental conditions in mirror sector, and they can be resonantly amplified by applying the magnetic field of the proper value. This opens up a possibility of $$n-{\bar{n}}$$ n - n ¯ transition with the probability $$P_{n{\bar{n}}} \simeq P_{nn'} P_{n\bar{n}'}$$ P n n ¯ ≃ P n n ′ P n n ¯ ′ which can reach the values $$\sim 10^{-8} $$ ∼ 10 - 8 or even larger. For finding this effect in real experiments, the magnetic field should not be suppressed but properly varied. These mixings can be induced by new physics at the scale of few TeV which may also originate a new low scale co-baryogenesis mechanism between ordinary and mirror sectors.

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