Continuous Monitoring of STAR\u27s Main Time Projection Chamber

STAR refers to the Solenoidal Tracking instrument At RHIC (the Relativistic Heavy Ion Collider). For momenta above 500 MeV/c charged kaons are not separated from pions within STAR\u27s Main TPC (Time Projection Chamber) by track density alone and they are poorly separated below 500 MeV/c, even when using information from other sources like the vertex tracker. Within the TPC large numbers of kaons and pions decay into muons (and undetected neutrinos). Earlier work has shown parent pions and kaons whose decays are detected within a TPC may be distinguished uniquely from each other in a two-dimensional plot of muon-emission angle versus momentum difference (between each parent meson and its decay muon). Since pions and kaons have zero spin, each muon decay-product emerges isotropically in its parent meson\u27s rest frame. Identification of particle type provides the parent meson\u27s rest mass and, thus, its total energy. This means the measurement of each decay event is kinematically complete. Thus, Lorentz Transformations may be used to transform each component of the decaying muon\u27s laboratory four-momentum into the rest frame of its parent meson, where the muon decay is isotropic. An aggregated plot of muon directions from many parent rest frames will be isotropic in each (selected) sub-volume of the TPC unless there is a problem within the TPC or in its tracking algorithms. Continuous monitoring of a TPC is possible using this subset of detected charged particles

The stability of poloidal magnetic fields in rotating stars

The stability of large-scale magnetic fields in rotating stars is explored, using 3D numerical hydrodynamics to follow the evolution of an initial poloidal field. It is found that the field is subject to an instability, located initially on the magnetic equator, whereby the gas is displaced in a direction parallel to the magnetic axis. If the magnetic axis is parallel to the rotation axis, the rotation does not affect the initial linear growth of the instability, but does restrict the growth of the instability outside of the equatorial zone. The magnetic energy decays on a timescale which is a function of the Alfv\'en crossing time and the rotation speed, but short compared to any evolutionary timescale. No evidence is found for a possible stable end state to evolve from an initial axisymmetric poloidal field. The field of an oblique rotator is similarly unstable, in both cases regardless of the rotation speed.Comment: A&A accepted. Animations available at http://www.cita.utoronto.ca/~jon/research/rp_anims.htm

Magnetic fields in non-convective regions of stars

We review the current state of knowledge of magnetic fields inside stars, concentrating on recent developments concerning magnetic fields in stably stratified (zones of) stars, leaving out convective dynamo theories and observations of convective envelopes. We include the observational properties of A, B and O-type main-sequence stars, which have radiative envelopes, and the fossil field model which is normally invoked to explain the strong fields sometimes seen in these stars. Observations seem to show that Ap-type stable fields are excluded in stars with convective envelopes. Most stars contain both radiative and convective zones, and there are potentially important effects arising from the interaction of magnetic fields at the boundaries between them. Related to this, we discuss whether the Sun could harbour a magnetic field in its core. Recent developments regarding the various convective and radiative layers near the surfaces of early-type stars and their observational effects are examined. We look at possible dynamo mechanisms that run on differential rotation rather than convection. Finally we turn to neutron stars with a discussion of the possible origins for their magnetic fields.Comment: 48 pages + 21 figures, to appear in Royal Society Open Science. This arXiv version includes internal links, external links to ADS abstracts, and uses standard astrophysical citation style. [The RSOS version uses the cumbersome numbered citations, and does without internal or external links

Infrared system studies for the earth resource program Final report

Obtaining terrain surface temperatures from radiances measured in orbi

Further infrared systems studies for the earth resources program Final report

Design of multispectral scanner for orbital earth resources detectio

Coplanarity Test for Selecting a Pair of Charged-Particle Tracks Resulting from a Single Neutral-Particle Decay

It is hard to determine directly the position of a neutral subatomic particle, but when such a particle decays into a pair of charged particles, it is easy to determine the positions of the charged decay particles and thereby infer the position of the parent particle at the time of its decay. A minimum of two coordinate points for each of the two decay particles is needed to reconstruct the position of the parent vertex. The mathematics of the reconstruction process is inherently interesting, and it can be used to demonstrate to students the utility of some of the most fundamental ideas of vector analysis

Curing a Summing Error That Occurs Automatically When Fitting a Function to Binomial or Poisson Distributed Data

Without special precautions a sum-rule error occurs automatically when a chi-squared procedure is used to fit a funtion to binomial or Poisson distributed histogram data if the function has at least one linear parameter. Since the square of the variance per channel is equal to the mean population, errors are usually approximated using (G2~=yi\u3e0)}; this choice for approximating the variance gives a per-channel error weighting of 1/yi that automatically results in a sum-rule error. This sum-rule error consistently and systematically underestimates the total sum of the data points by an amount equal to the value of %*, resulting in Zjyj-Zjfj= J& where %i = £j(vi - QVyi an^ f\u27i= f(Xj,{parameters}). In contrast, using {o\u27-f=(¦\u3e()} gives the error weighting per channel of 1/fj that automatically results in a less well known sum rule error. This sum-rule error which is only half as large but opposite insign consistently and systematically overestimates the total sum ofthe data X? points by an amount equal to half the value of %?, that is, itresults in - Zjf- =- L y ,where Xr = (vi \u27i) \u27/\u27i- The good news is a combination of error weightings may be constructed which completely eliminates the otherwise automatically cocuring sum-rule error by taking advantage of cancellations occuring between the two sum-rule errors implicit in the two above-mentioned approaches to error-weighting per channel. This fortunitous linear combination ofsum-rule error swill combine and cancel ifthe fitting funtion is a sufficiently viable choice so that Xr= Xy = v (number ofdegrees of freedom); 1 2 consequently a weighted linear combination of these two definitions may be used, X 2 = 3 Xy + !%?• This choice for X = is 1 1 2 equivalent to choosing an error weighting of „\u27_\u27 = 3yj +:\u27\u3e(; ,and it essentially eliminates summing errors so that Xjyi- Zjf-. An alternate method is presented and proven for {jLt; = f-}infitting a function using Maximum Likelihood

Relativistic models of magnetars: the twisted-torus magnetic field configuration

We find general relativistic solutions of equilibrium magnetic field configurations in magnetars, extending previous results of Colaiuda et al. (2008). Our method is based on the solution of the relativistic Grad-Shafranov equation, to which Maxwell's equations can be reduced in some limit. We obtain equilibrium solutions with the toroidal magnetic field component confined into a finite region inside the star, and the poloidal component extending to the exterior. These so-called twisted-torus configurations have been found to be the final outcome of dynamical simulations in the framework of Newtonian gravity, and appear to be more stable than other configurations. The solutions include higher order multipoles, which are coupled to the dominant dipolar field. We use arguments of minimal energy to constrain the ratio of the toroidal to the poloidal field.Comment: 13 pages, 12 figures. Minor changes to match the version published on MNRA

Separating K+/- from Pi+/- using In-Flight Decays to Mu+/- + Nu

A method is presented for completely distinguishing between charged kaons and charged pions by using their charged muon (plus neutrino) decays (with neutrinos undetected) for meson laboratory momenta up to 1000 MeV/c. When either a charged kaon or a charged pion decays into a muon and a neutrino, momentum-energy (four-momentum) conservation will be used to provide unique kinematic trajectories for distinguishing kaon decays from pion decays when the change in three-momentum of the muon from that of either parent kaon or pion is measured (or simulated). Ina magnetic field, observation of a tracked particle showing a kink and/or a change in helicity indicates the decay of the parent particle into a similarly charged muon product. Unique kinematic separation between each parent kaon and parent pion is possible for each parent particle\u27s momentum up to 1000 MeV/c. Curvature-radius of the helical path in a magnetic field is used to determine each charged particle\u27s momentum, whether it be a kaon, a pion or a muon. A weak field is adequate for making this determination since momentum (curvature radius) need only be measured to an accuracy of about 10%. Monte Carlo calculations of the kineatic trajectories have been carried out for primary meson momenta between 0 and 1000 MeV/c and for a range of emission angles (or kinks ) between 0° and 180°. Monte Carlo results from these in-flight decay kinematic calculations show a complete separation is possible for pion decays from kaon decays for laboratory momenta up to 1000 MeV/c because these two classes of meson decays cluster into completely separated 2-D regions of difference-momentum (x)muon-angle space. The most difficult region for separating primary particles occurs for small-kink decays within less than 5°. Decay halflife and time dilation require an efficient time projection chamber to be fairly large, because kaons are strongly favored over pions at the higher laboratory momenta and for the smaller time projection chamber geometries