اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدNeutron lifetime beam anomaly and possible explanation
111
0
0.0
(
0
)
تأليف
A. P. Serebrov
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
The review of experimental measurements of neutron lifetime is presented. Latest measurements with gravitational trap (PNPI NRC KI) and magnetic trap (LANL, USA) confirmed the result obtained by PNPI group in 2005. The results of measurements performed using UCN storing method are in good agreement; however, there is a significant discrepancy at 3.6{sigma} (1% of decay probability) level with beam method experiment. The latest most accurate measurements of the neutron decay asymmetry and neutron lifetime measurements by storage method are in agreement within the Standard Model. This article discusses the possible causes of discrepancy in the measurements of the neutron lifetime. The most probable cause, apparently, is the loss of protons in beam method experiment during storage in a magnetic trap due to charge exchange collisions of protons with the residual gas. The proton becomes neutral and leaves the trap, which leads to a decrease in the number of registered protons, i.e. to a decrease in the probability of neutron decay or to an increase in the measured neutron lifetime.
قيم البحث
اقرأ أيضاً
The results of measurements performed using UCN storing method are in good agreement. The latest most accurate measurements of the neutron decay asymmetry and neutron lifetime measurements by storage method are in agreement within the Standard Model.
However, there is a significant discrepancy at $3.6sigma$ (1% of decay probability) level with beam method experiment. This article discusses the possible causes of discrepancy in the measurements of the neutron lifetime with beam method experiment. The most probable cause, apparently, is the loss of protons in beam method experiment during storage in a magnetic trap due to charge exchange collisions of protons with the residual gas. The proton becomes neutral and leaves the trap, which leads to a decrease in the number of registered protons, i.e. to a decrease in the probability of neutron decay or to an increase in the measured neutron lifetime.
We comment on a recent manuscript by A. P. Serebrov, et al. regarding residual gas charge exchange in the beam neutron lifetime experiment
Free neutrons have a measured lifetime of 880 s, but disagreement between existing laboratory measurements of ~10 s have persisted over many years. This uncertainty has implications for multiple physics disciplines, including standard-model particle
physics and Big-Bang nucleosynthesis. Space-based neutron lifetime measurements have been shown to be feasible using existing data taken at Venus and the Moon, although the uncertainties for these measurements of tens of seconds prevent addressing the current lifetime discrepancy. We investigate the implementation of a dedicated space-based experiment that could provide a competitive and independent lifetime measurement. We considered a variety of scenarios, including measurements made from orbit about the Earth, Moon, and Venus, as well as on the surface of the Moon. For a standard-sized neutron detector, a measurement with three-second statistical precision can be obtained from Venus orbit in less than a day; a one-second statistical precision can be obtained from Venus orbit in less than a week. Similarly precise measurements in Earth orbit and on the lunar surface can be acquired in less than 40 days (three-second precision) and ~300 days (one-second precision). Systematic uncertainties that affect a space-based neutron lifetime measurement are investigated, and the feasibility of developing such an experiment is discussed.
Since long neutron lifetimes measured with a beam of cold neutrons are significantly different from lifetimes measured with ultracold neutrons bottled in a trap. 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 new data on neutron decay parameters. Furthermore, data from neutron decay now compare well with Ft data derived from nuclear b{eta} decays.
The puzzle remains in the large discrepancy between neutron lifetime measured by the two distinct experimental approaches -- counts of beta decays in a neutron beam and storage of ultracold neutrons in a potential trap, namely, the beam method versus
the bottle method. In this paper, we propose a new experiment to measure the neutron lifetime in a cold neutron beam with a sensitivity goal of 0.1% or sub-1 second. The neutron beta decays will be counted in a superfluid helium-4 scintillation detector at 0.5 K, and the neutron flux will be simultaneously monitored by the helium-3 captures in the same volume. The cold neutron beam must be of wavelength $lambda>16.5$ A to eliminate scattering with superfluid helium. A new precise measurement of neutron lifetime with the beam method of unique inherent systematic effects will greatly advance in resolving the puzzle.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
