18967452
The Spin-statistics connection in classical field theory
The spin-statistics connection is obtained for a simple formulation of a classical field theory containing even and odd Grassmann variables. To that end, the construction of irreducible canonical realizations of the rotation group corresponding to general causal fields is reviewed. The connection is obtained by imposing local commutativity on the fields and exploiting the parity operation to exchange spatial coordinates in the scalar product of classical field evaluated at one spatial location with the same field evaluated at a distinct location. The spin-statistics connection for irreducible canonical realizations of the Poincare group of spin j is obtained in the form: classical fields and their conjugate momenta satisfy fundamental field-theoretic Poisson bracket relations for 2j even and fundamental Poisson antibracket relations for 2j odd.
119416196
Parity and the spin—statistics connection
A simple demonstration of the spin—statistics connection for general causal fields is obtained by using the parity operation to exchange spatial coordinates in the scalar product of a locally commuting field operator, evaluated at position x, with the same field operator evaluated at − x, at equal times.
14422873
Neutrino Propulsion for Interstellar Spacecraft
An exotic spacecraft propulsion technology is described which exploits parity violation in weak interactions. Anisotropic neutrino emission from a polarized assembly of weakly interacting particles converts rest mass directly to spacecraft impulse.
107773393
Proposed Magnet Alignment Changes for AP-1
AP-1 was built to connect the Antiproton Source with the Main Ring accelerator. The beamline was designed to support modes of operation at both 8 GeV and 120 GeV kinetic energy. During the days of Main Ring operation, 120 GeV beam was extracted through the field region of a Lambertson at F-17 and transported approximately 174 meters to the production target. This 'pbar production' mode required a lattice that would focus the proton beam to a small spot size on the target to maximize antiproton yield. The AP-1 line would also be reconfigured to operate at 8 GeV to support antiproton transfers and tuning cycles with protons. The AP-1 line is also connected to the Accumulator via AP-3, so the lattices of these beamlines needed to be compatible. After the Main Injector was built to replace the Main Ring, a beamline was required to connect it with the Antiproton Source. Designers chose to combine beam transfers of 150 GeV protons to the Tevatron, 120 GeV protons to AP-1, 120 GeV protons to Switchyard and 8 GeV proton tune-up or antiproton transfers via AP-1 into the P1 and P2 lines. The P2 line resides in the Main Ring tunnel enclosure betweenmore » F-0 and F-17 and utilizes original Main Ring magnets. The lattice was designed to duplicate the Twiss parameters of the old Main Ring at F-17, including the large horizontal beta and dispersion functions. The addition of the P1 and P2 lines add almost an additional 1,000 meters and an extra Lambertson magnet (at F0) to beam transfers to and from the Main Injector versus the Main Ring. Although Lambertson magnets are still used to extract beam from the Main Injector, the Lambertson at F-17 was no longer required. Unfortunately, the limited aperture C-magnets at F-17 remained, necessitated by the P3 line which is intended to provide beam to Switchyard for future 'Meson 120' operation. The C-magnets are one of the limiting horizontal apertures in the AP-1 line due to the combination of small physical aperture and the large horizontal beta and dispersion functions. Most of the AP-1 magnets were originally used in Switchyard. Apertures of these magnets are adequate for high energy operation, but have apertures that are smaller than magnets traditionally used in other 8 GeV transfer lines. This makes the AP-1 line unusually sensitive to alignment and steering errors. In addition, the lattice constraints imposed by the beamlines attached to AP-1 does not allow much freedom in suppressing the lattice functions at key locations to reduce the beam size.« less
119252361
First Results from Pan-STARRS1: Faint, High Proper Motion White Dwarfs in the Medium-Deep Fields
The Pan-STARRS1 survey has obtained multi-epoch imaging in five bands (Pan-STARRS1 g P1, r P1, i P1, z P1, and y P1) on 12 "Medium-Deep fields," each of which spans a 33 circle. For the period between 2009 April and 2011 April these fields were observed 50-200 times. Using a reduced proper motion diagram, we have extracted a list of 47 white dwarf (WD) candidates whose Pan-STARRS1 astrometry indicates a non-zero proper motion at the 6σ level, with a typical 1σ proper motion uncertainty of 10 mas yr–1. We also used astrometry from the Sloan Digital Sky Survey (when available) and USNO-B to assess our proper motion fits. None of the WD candidates exhibits evidence of statistically significant parallaxes, with a typical 1σ uncertainty of 8 mas. Twelve of these candidates are known WDs, including the high proper motion (17 yr–1) WD LHS 291. We confirm seven more objects as WDs through optical spectroscopy. Based on the Pan-STARRS1 colors, ten of the stars are likely to be cool WDs with 4170 K <T eff < 5000 K and cooling ages ≈ 8 Gyr. Based on their kinematics, these objects are likely thick disk WDs, but a subset may belong to the halo. Our current sample represents only a small fraction of the Pan-STARRS1 data. With continued coverage from the Medium-Deep Field Survey and the 3π survey, Pan-STARRS1 should find many more high proper motion WDs that are part of the old thick disk and halo.
122467679
A statistical analysis of the Stanford fractional charge experiment
Abstract We report arguments indicating that the residual fractional charges observed on niobium spheres in the experiments at Stanford are consistent with a statistical distribution of one kind of fractionally-charged object among the spheres, with a large average number of charges per sphere. Our statistical analysis enables us to conclude with 96% confidence that the spheres annealed on a tungsten substrate have a substantially higher concentration of fractional charges than those annealed on a niobium substrate. We draw attention to circumstantial evidence that such fractional charges were transferred from the tungsten substrate to the surfaces of the niobium spheres. We point out that surface and grain-boundary segregation effects, which previously have not been considered in assessing this experiment, could play a major role in enhancing the concentration of fractionally charged impurities on the surface of the tungsten substrate in contact with the niobium spheres. We conclude that the Stanford experiment would be consistent with a concentration of 1 fractional charge in 10 13 to 10 14 tungsten atoms, which would not be contradicted by other searches for fractional charges in tungsten.
118650819
A Search for High Proper Motion T Dwarfs with Pan-STARRS1 + 2MASS + WISE
We have searched ≈8200 deg2 for high proper motion (≈05-27 year–1) T dwarfs by combining first-epoch data from the Pan-STARRS1 (PS1) 3π Survey, the Two Micron All Sky Survey (2MASS) All-Sky Point Source Catalog, and the WISE Preliminary Data Release. We identified two high proper motion objects with the very red (W1 – W2) colors characteristic of T dwarfs, one being the known T7.5 dwarf GJ 570D. Near-IR spectroscopy of the other object (PSO J043.5395+02.3995 ≡ WISEP J025409.45+022359.1) reveals a spectral type of T8, leading to a photometric distance of 7.2 ± 0.7 pc. The 256 year–1 proper motion of PSO J043.5+02 is the second highest among field T dwarfs, corresponding to a tangential velocity of 87 ± 8 km s–1. According to the Besancon galaxy model, this velocity indicates that its galactic membership is probably in the thin disk, with the thick disk an unlikely possibility. Such membership is in accord with the near-IR spectrum, which points to a surface gravity (age) and metallicity typical of the field population. We combine 2MASS, Sloan Digital Sky Survey, WISE, and PS1 astrometry to derive a preliminary parallax of 171 ± 45 mas (5.8+2.0 – 1.2 pc), the first such measurement using PS1 data. The proximity and brightness of PSO J043.5+02 will facilitate future characterization of its atmosphere, variability, multiplicity, distance, and kinematics. The modest number of candidates from our search suggests that the immediate (~10 pc) solar neighborhood does not contain a large reservoir of undiscovered T dwarfs earlier than about T8.
54052136
Progress in Antiproton Production at the Fermilab Tevatron Collider
Fermilab Collider Run II has been ongoing since 2001. During this time peak luminosities in the Tevatron have increased from approximately 10 x 10{sup 30} cm{sup -2}sec{sup -1} to 300 x 10{sup 30} cm{sup 02}sec{sup -1}. A major contributing factor in this remarkable performance is a greatly improved antiproton production capability. Since the beginning of Run II, the average antiproton accumulation rate has increased from 2 x 10{sup 10}{anti p}/hr to about 24 x 10{sup 10}{anti p}/hr. Peak antiproton stacking rates presently exceed 28 x 10{sup 10}{anti p}/hr. The antiproton stacking rate has nearly doubled since 2005. It is this recent progress that is the focus of this paper. The process of transferring antiprotons to the Recycler Ring for subsequent transfer to the collider has been significantly restructured and streamlined, yielding additional cycle time for antiproton production. Improvements to the target station have greatly increased the antiproton yield from the production target. The performance of the Antiproton Source stochastic cooling systems has been enhanced by upgrades to the cooling electronics, accelerator lattice optimization, and improved operating procedures. In this paper, we will briefly report on each of these modifications.