The naturalness criterion applied to the cosmological constant implies a new-physics threshold at 10^-3 eV. Either the naturalness criterion fails, or this threshold does not influence particle dynamics at higher energies. It has been suggested that the Higgs naturalness problem may follow the same fate. We investigate this possibility and, abandoning the hierarchy problem, we use unification and dark matter as the only guiding principles. The model recently proposed by Arkani-Hamed and Dimopoulos emerges as a very interesting option. We study it in detail, analysing its structure, and the conditions for obtaining unification and dark matter.
Proton boron capture therapy offers a promising enhancement to conventional proton therapy by leveraging the 11B(p,a)3a nuclear reaction for localized dose amplification. This study systematically investigates the Bragg curve characteristics of proton beams using the Geant4 Monte Carlo toolkit, with a particular focus on the dosimetric impact of ??B. The introduction of a pure ??B target induced a consistent forward shift in the Bragg peak position, attributed to increased stopping power and nuclear reactions. Furthermore, Proton boron capture therapy demonstrated enhanced local energy deposition along the central axis due to the generation of high linear energy transfer alpha particles, with minimal lateral broadening. To facilitate precise treatment planning, Bragg curve data for 800 distinct proton energies (0-80 MeV) in water were generated. Various machine learning algorithms were subsequently employed to develop predictive models for the Bragg peak position. Comparative analysis identified gaussian process regression as the optimal model, achieving an R? of 0.999997 and a root mean squared error of approximately 0.0273 mm for predicting Bragg peak positions in water. Crucially, this research pioneers a novel pathway for proton boron capture therapy treatment planning by combining high-accuracy machine learning-based prediction of the initial Bragg peak (in water) with a characterized correction for the ??B-induced forward shift, enabling more precise determination of the actual treatment depth. This work provides critical dosimetric characterization, quantifies key ??B-induced phenomena, and offers a validated predictive framework, thereby establishing a theoretical foundation and technical support for dose optimization in this emerging therapeutic modality.
We discuss issues raised by Serebrov, et al. in a recent paper regarding systematic effects in the beam neutron lifetime experiment performed at NIST. We show that these effects were considered in the original analyses and that our corrections and systematic uncertainties were appropriate. We point out some misconceptions and erroneous assumptions in the analysis of Serebrov, et al. None of the issues raised in Serebrov, et al lead us to alter the value of the neutron lifetime reported previously.
This paper presents results of the development of a small-sized free release monitor designed for the release of materials, various hand tools, equipment and instruments of nuclear enterprises and laboratories staff that weight up to 50 kg, from radiation control. To increase the registration sensitivity of controlled radionuclides, 12 scintillation units based on a 3"x3" sized NaI (Tl) crystal were used as gamma-radiation detectors. Volume of the measuring chamber of the monitor amounted to 200 L, the chosen thickness of the low-back ground shielding was 50 mm. The values of the minimum detect able activity of the designed monitor for the point sources 123I, 131I, 99mTc, 18F were better than 100 Bq with measurement time not exceeding 60 seconds.
The atomic masses of the isotopes $^{206,207}$Ra have been measured via decay-correlated mass spectroscopy using a multi-reflection time-of-flight mass spectrograph equipped with an $α$-TOF detector. The Ra isotopes were produced as fusion-evaporation products in the $^{51}$V+$^{159}$Tb reaction system and delivered by the gas-filled recoil ion separator GARIS-II at RIKEN. The $α$-TOF detector provides for high-accuracy mass measurements by correlating time-of-flight signals with subsequent $α$-decay events. The masses of $^{206}$Ra and $^{207g,m}$Ra were directly measured using a multi-reflection time-of-flight mass spectrograph equipped with an $α$-TOF detector. A mass excess of ME = 3538(15) keV/c$^2$ and an excitation energy of E$_{\rm ex}$ = 552(42) keV were determined. The $α$-decay branching ratio of $^{207m}$Ra, b$α$ = 0.26(20), was directly determined from decay-correlated time-of-flight signals, and the reduced alpha width of $^{207m}$Ra was calculated to be $δ^2$ = 50+62-41 keV from the branching ratio. The spin-parity of $^{207m}$Ra was confirmed to be $J^π$ = 13/2$^-$ from decay correlated mass measurement results.
The spectrometric systems, especially based on NaI(Tl) and HPGe detectors, are used for nuclide identification and calculation of their activities from the ground measurements and air-borne monitoring. The determination of the air kerma (dose) rates is also very important for environmental measurements. In such cases, the detectors should be calibrated for air kerma (dose) rates in nGyh?1 or ?Gyh?1. A simple calibration of NaI(Tl), HPGe as well as plastic detectors for the low-level air kerma rates is presented in this contribution. This calibration is based on comparing the relative absorbed energy rate in detectors (MeVs?1) calculated from spectra with the air kerma rates calculated by the Monte Carlo simulation and supplementary to the data from the RSS Reuter&Stokes high pressure ion chamber. This method also eliminates the conversion from the non-air kerma rates in crystals to the air kerma rates. Three different types of small cylindrical detectors were calibrated for the air kerma rates from the background of 26 nGyh?1 to some tens of ?Gyh?1 in the energy range to the maximum of 3 MeV. The results of calibrations of the 3" x 3" NaI(Tl), HPGe detector and a small plastic detector (made of polystyrene) including soxme examples of environmental measurements are presented.
The radiological hazard of building materials originating from clay, rock and other mineral wastes has attracted more attention because they contain natural radionuclides (226Ra, 232Th, and 40K). The activity concentration of radionuclides in red-clay brick samples obtained from three different brickyards in Shangluo, China waHs measured. Various indexes, including radium equivalent activities, Raeq, external hazard index, Hex, internal hazard index, Hin, indoor air absorbed dose rate, D, and annual effective dose, AED, of the aforementioned radionuclides in the bricks were used to assess the radiation hazard for people. The average activity concentrations of 226Ra, 232Th, and 40K were respectively 34.5 ? 1.9, 62.5 ? 2.1, and 713.7 ? 19.8 Bqkg?1 for the studied red-clay bricks. The Raeq values of the red-clay brick samples varied from 167.0 to 184.7 Bqkg?1, which are lower than the limit of 370 Bqkg?1. Moreover, the activity concentrations of natural radionuclides in unfired brick, clay and coal were also determined and the results were compared with that in the red-clay brick samples. This study shows that the red-clay bricks produced in Shangluo, China can be used safely in construction industries.
From a homeland security point of view, it is important to detect the transportation of radioactive materials or potential radioactive contamination. The most commonly used devices are radiation portal monitors with plastic scintillation detectors. A signal from such detectors is processed by an amplitude analyser which can separate pulses into several mutually independent energy windows (representing energy intervals of gamma radiation). Therefore, the most appropriate method of evaluation is by the use of algorithms for multidimensional processing. This article describes a novel generalised approach designed with respect to the properties of radiation portal monitors. It includes a description of formulas and a whole algorithm as well as the procedure for determining the appropriate critical and detection limits. The predicted probability distribution for the proposed method of calculation was verified by simulations and experimental measurements. The algorithm was also compared with a commonly used gross counting algorithm.