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تسجيل مستخدم جديدSearch for neutron - mirror neutron oscillations in a laboratory experiment with ultracold neutrons
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Mirror matter is considered as a candidate for dark matter. In connection with this an experimental search for neutron - mirror neutron (nn) transitions has been carried out using storage of ultracold neutrons in a trap with different magnetic fields. As a result, a new limit for the neutron - mirror neutron oscillation time has been obtained, tau_osc >= 448 s (90% C.L.), assuming that there is no mirror magnetic field larger than 100 nT. Besides a first attempt to obtain some restriction for mirror magnetic field has been done.
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It has been proposed that there could be a mirror copy of the standard model particles, restoring the parity symmetry in the weak interaction on the global level. Oscillations between a neutral standard model particle, such as the neutron, and its mi
rror counterpart could potentially answer various standing issues in physics today. Astrophysical studies and terrestrial experiments led by ultracold neutron storage measurements have investigated neutron to mirror-neutron oscillations and imposed constraints on the theoretical parameters. Recently, further analysis of these ultracold neutron storage experiments has yielded statistically significant anomalous signals that may be interpreted as neutron to mirror-neutron oscillations, assuming nonzero mirror magnetic fields. The neutron electric dipole moment collaboration performed a dedicated search at the Paul Scherrer Institute and found no evidence of neutron to mirror-neutron oscillations. Thereby, the following new lower limits on the oscillation time were obtained: $tau_{nn} > 352~$s at $B=0$ (95% C.L.), $tau_{nn} > 6~text{s}$ for all $0.4~mutext{T}<B<25.7~mutext{T}$ (95% C.L.), and $tau_{nn}/sqrt{cosbeta}>9~text{s}$ for all $5.0~mutext{T}<B<25.4~mutext{T}$ (95% C.L.), where $beta$ is the fixed angle between the applied magnetic field and the local mirror magnetic field which is assumed to be bound to the Earth. These new constraints are the best measured so far around $Bsim10~mu$T, and $Bsim20~mu$T.
In case a mirror world with a copy of our ordinary particle spectrum would exist, the neutron n and its degenerate partner, the mirror neutron ${rm n}$, could potentially mix and undergo ${rm nn}$ oscillations. The interaction of an ordinary magnetic
field with the ordinary neutron would lift the degeneracy between the mirror partners, diminish the ${rm n}$-amplitude in the n-wavefunction and, thus, suppress its observability. We report an experimental comparison of ultracold neutron storage in a trap with and without superimposed magnetic field. No influence of the magnetic field is found and, assuming negligible mirror magnetic fields, a limit on the oscillation time $tau_{rm nn} > 103$ s (95% C.L.) is derived.
We performed ultracold neutron (UCN) storage measurements to search for additional losses due to neutron (n) to mirror-neutron (n) oscillations as a function of an applied magnetic field B. In the presence of a mirror magnetic field B, UCN losses wou
ld be maximal for B = B. We did not observe any indication for nn oscillations and placed a lower limit on the oscillation time of tau_{nn} > 12.0 s at 95% C.L. for any B between 0 and 12.5 uT.
Neutron lifetime is one of the most important physical constants which determines parameters of the weak interaction and predictions of primordial nucleosynthesis theory. There remains the unsolved problem of a 3.9{sigma} discrepancy between measurem
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