Ratio-Based Pulse Shape Discrimination: Analytic Results for Gaussian and Poisson Noise Models

In experiments in a range of felds including fast neutron spectroscopy and astroparticle physics, one can discriminate events of interest from background events based on the shapes of electronic pulses produced by energy deposits in a detector. Here, I focus on a well-known pulse shape discrimination method based on the ratio of the temporal integral of the pulse over an early interval Xp and the temporal integral over the entire pulse Xt . For both event classes, for both a Gaussian noise model and a Poisson noise model, I present analytic expressions for the conditional distribution of Xp given knowledge of the observed value of Xt and a scaled energy deposit corresponding to the product of the full energy deposit and a relative yield factor. I assume that the energy-dependent theoretical prompt fraction for both classes are known exactly. With a Bayesian approach that accounts for imperfect knowledge of the scaled energy deposit, I determine the posterior mean background acceptance probability given the target signal acceptance probability as a function of the observed value of Xt . My method enables one to determine receiver-operating-characteristic curves by numerical integration rather than by Monte Carlo simulation for these two noise models.

Simulating fusion alpha heating in a stellarator reactor

Gyrocenter following simulations of fusion born alpha particles in a stellarator reactor are preformed using the BEAMS3D code. The Wendelstein 7-X high mirror configuration is scaled in geometry and magnetic field to reactor relevant parameters. A 2×1020 m−3 density plasma with 20 keV core temperatures is assumed and fusion birth rates calculated for various fusion products assuming a 50/50 deuterium-tritium mixture. It is found that energetic He4 ions comprise the vast majority of the energetic particle inventory. Slowing down simulations of the He4 population suggest plasma heating consistent with scaled energy confinement times for a stellarator reactor. Losses for this configuration appear large suggesting optimization beyond the scope of the W7-X device is key to a future fusion reactor. These first simulations are designed to demonstrate the capability of the BEAMS3D code to provide fusion alpha birth and heating profiles for stellarator reactor designs.

Two Empirical Double-Corner-Frequency Source Spectra and Their Physical Implications

ABSTRACT We introduce double-corner-frequency (DCF) source spectral models JA19 and JA19_2S, which, in conjunction with a stochastic ground-motion model, can reproduce the mean peak ground acceleration (PGA) and mean peak ground velocity (PGV) of the Next Generation Attenuation-West 2 database for magnitudes 3.3–7.3. Their displacement amplitude spectrum remains constant for frequencies less than fc1, decays as f−1 between fc1 and fc2, and decays as f−2 for frequencies greater than fc2. The model JA19 is self-similar. Its two corner frequencies fc1 and fc2 scale with moment magnitude (M) as (1) log(fc1(M))=1.754−0.5M and (2) log(fc2(M))=3.250−0.5M. We find that relation (1) is consistent with the known self-similar scaling relations of the rupture duration (Td), in which Td=1/(πfc1). Relation (2) may reflect the scaling relation of the average rise time (TR), where TR∼0.8/(fc2). Stochastic simulations of ground motion using JA19 cannot reproduce the sharp change in magnitude dependence of PGA and PGV at M 5.3, suggesting a breakdown of self-similarity. The magnitude dependence of PGA and PGV and this change in slope is well explained by JA19_2S, which results from perturbing the fc1 scaling relationship in JA19. For JA19_2S: log(fc1(M))=1.474−0.415M for M≤5.3; log(fc1(M))=2.375−0.585M for M>5.3. The scaling relation for fc2 is unchanged. When fc1≪fc2, the scaled energy (ratio of radiated energy and seismic moment) scales with M0fc12fc2. The scaled energy of JA19 is 2.2×10−5, independent of magnitude. Because JA19_2S is not self-similar, its scaled energy is 2.2–4.7×10−5, increasing 2.2 times, when magnitude increases from 3.3 to 5.3, and, subsequently decreasing 2.2 times, as magnitude further increases from 5.3 to 7.3. Both agree with the global average (∼3×10−5) reported previously. Using our proposed empirical models, the standard deviation of average static stress drop from seismological studies can be significantly greater than the standard deviation of the stress parameter used to estimate PGA and PGV.

Local regularity and compactness for the p-harmonic map heat flows

We study a geometric analysis and local regularity for the evolution of {{p}}-harmonic maps, called {{p}}-harmonic map heat flows. Our main result is to establish a criterion for a uniform local regularity estimate for regular {{p}}-harmonic map heat flows, devising some new monotonicity-type formulas of a local scaled energy. The regularity criterion obtained is almost optimal, comparing with that of the corresponding stationary case. As application we show a compactness of regular {{p}}-harmonic map heat flows with energy bound.

Global analysis of π± and K± fragmentation functions and their application to top quark decays considering new BABAR and Belle experimental data

Recently, the Belle and BABAR collaborations published the single-inclusive electron–positron annihilation data at the center of mass energies ([Formula: see text]) of 10.52 and 10.54 GeV, respectively. These new data offer one the possibility to determine the nonperturbative initial conditions of fragmentation functions (FFs) much more accurately. Here, we extract the FFs of π± and K± particles at next-to-leading order (NLO) including these new data, which are in the regions of larger scaled-energy z and lower [Formula: see text]. However, the π± and K± FFs were calculated previously, but our new analysis shows that adding these new data, for instance, changes the (u, s) → π+ FFs in the large-z region while the s → π+ FF is also changed at low z. These new data also change the u → K+ FF at low z (z < 0.2) more than at large z, but the d → K+ FF is affected at z > 0.07. The FF of g → K+ is decreased everywhere, for example, about 25% at z = 0.01. We also apply, for the first time, the extracted FFs to make our predictions for the scaled-energy distributions of π± and K± inclusively produced in top quark decays at NLO.

Photoionization microscopy of hydrogen in magnetic and quadrupolar electric fields

The photoionization microscopy of hydrogen in magnetic and quadrupolar electric fields is studied on the basis of the semiclassical theory. Potential for the studied system possesses saddle points lying in the [Formula: see text]-direction, rather than the [Formula: see text]-direction in the common case, such as atom in the electric field. We find the electron current recorded by cylindrical surface detector shows symmetric interference patterns along [Formula: see text]-direction, and predict that the interference pattern presents the list structure, instead of the cyclic structure observed in the electric field. Besides, the interference structures are assigned to different types of trajectories. As the scaled energy increases, the structure of the interference pattern evolves smoothly and more types of trajectories emerge.