119000563
New measurement of the altitude dependence of the atmospheric muon intensity
We present a new measurement of atmospheric muons made during an ascent of the High Energy Antimatter Telescope balloon experiment. The muon charge ratio {mu}{sup +}/{mu}{sup -} as a function of atmospheric depth in the momentum interval 0.3-0.9 GeV/c is presented. The differential {mu}{sup -} intensities in the 0.3-50 GeV/c range and for atmospheric depths between 4-960 g/cm{sup 2} are also presented. We compare these results with other measurements and model predictions. We find that our charge ratio is {approx}1.1 for all atmospheric depths and is consistent, within errors, with other measurements and the model predictions. We find that our measured {mu}{sup -} intensities are also consistent with other measurements, and with the model predictions, except at shallow atmospheric depths.
122083477
Evidence against ''anomalon'' production in high-energy heavy-ion collisions
Results are presented from an electronic experiment to check directly the anomalous mean-free-path phenomena observed in high-energy heavy-ion collisions. The mean-free-path measurements presented are based on interactions of 1.25 \ifmmode\times\else\texttimes\fi{} ${10}^{5}$ secondary fragments produced by interactions of $1.8A$-GeV $^{40}\mathrm{Ar}$ in Lucite. The result is consistent with no anomalon phenomena and rules out (95% confidence limit) anomalons being more than 2% abundant if they have interaction lengths between 0.4 and 3 cm.
117398705
Measurement of the Cosmic-Ray Antiproton Energy Spec- trum with HEAT-pbar
The absolute intensities of cosmic-ray antiprotons have been measured in the energy range between 4.5 and 50 GeV. The data were obtained by the HEAT-pbar instrument, a balloon borne superconducting magnet spectrometer with precise rigidity and multiple energy loss measurement capability. The instrument was flown in the Spring 2000 from Ft. Sumner, NM, at an average atmospheric depth of 7.2 g/cm. Here we briefly describe the instrument and the measurement and outline the analysis of the data which is still ongoing at this time. We will present the result of our analysis and discuss the implications for cosmic-ray propagation models at the conference.
118827396
Measurement of neutrino oscillations in MACRO experiment
15013492
Cosmic-ray positrons: Are there primary sources?
Abstract Galactic cosmic rays consist of primary and secondary particles. Primary cosmic rays are thought to be energized by first order Fermi acceleration processes at supernova shock fronts within our Galaxy. The cosmic rays that eventually reach the Earth from this source are mainly protons and atomic nuclei, but also include electrons. Secondary cosmic rays are created in collisions of primary particles with the diffuse interstellar gas. They are relatively rare but carry important information on the Galactic propagation of the primary particles. The secondary component includes a small fraction of antimatter particles, positrons and antiprotons. In addition, positrons and antiprotons may also come from unusual sources and possibly provide insight into new physics. For instance, the annihilation of heavy supersymmetric dark matter particles within the Galactic halo could lead to positrons or antiprotons with distinctive energy signatures. With the High-Energy Antimatter Telescope (HEAT) balloon-borne instrument, we have measured the abundances of positrons and electrons at energies between 1 and 50 GeV. The data suggest that indeed a small additional antimatter component may be present that cannot be explained by a purely secondary production mechanism. Here we describe the signature of the effect and discuss its possible origin.
120330554
Searching for TeV cosmic electrons with the CREST experiment
The Cosmic Ray Electron Synchrotron Telescope (CREST) high-altitude balloon experiment is a pathfinding effort to detect for the first time multi-TeV cosmic-ray electrons. Such would be the markers of nearby cosmic accelerators, as energetic electrons from distant Galactic sources are expected to be depleted by radiative losses during interstellar transport. Electrons will be detected indirectly by the characteristic signature of their geomagnetic synchrotron losses, in the form of a burst of coaligned x-ray photons intersecting the plane of the instrument. Since the primary electron itself need not traverse the payload, an effective detection area is achieved that is several times the nominal 6.4 m 2 instrument. The payload is composed of an array of 1024 BaF2 crystals surrounded by a set of veto scintillator detectors. A long-duration balloon flight in Antarctica is planned for the 2011-12 season.
32444546
Measurement of the Michel parameter rho in muon decay.
The TWIST Collaboration has measured the Michel parameter rho in normal muon decay, mu(+)--> e(+)nu(e)nu (mu). In the standard model, rho = 3/4. Deviations from this value imply mixing of left- and right-handed muon and electron couplings. We find rho=0.750 80+/-0.000 32(stat) +/- 0.000 97(syst) +/- 0.000 23, where the last uncertainty represents the dependence of rho on the Michel parameter eta. This result sets new limits on the W(L)-W(R) mixing angle in left-right symmetric models.
37256736
Drift chambers for a precision measurement of the Michel parameters in muon decay
Planar drift chambers will be used in a solenoidal magnetic field to measure the Michel parameters in muon decay. The chamber manufacture procedure uses flat glass tables and precise ceramic glass spacers to provide precise anode– cathode spacing. Results of bench and beam tests of the prototype chambers are discussed. # 2001 Elsevier Science B.V. All rights reserved.
119378848
Measurement of P(mu)xi in polarized muon decay
The quantity P_{mu}^{pi}xi, where xi is one of the muon decay parameters and $P_{\mu}^{\pi}$ is the degree of muon polarization in pion decay, has been measured. The value P_{mu}^{pi}xi = 1.0003 +- 0.0006 stat. +- 0.0038 syst. was obtained. This result agrees with previous measurements but is over a factor of two more precise. It also agrees with the Standard Model prediction for P_{mu}^{pi}xi and thus leads to restrictions on left-right symmetric models.
119708470
TWIST- The TRIUMF weak interaction symmetry test the Michel parameters from μ+ decay
Abstract We propose to make the first high precision measurements of nearly the entire differential spectrum (in energy and angle) of positrons from the decay of polarized muons. The main goal of the experiment is the precise testing of the ( V - A ) structure of electroweak interactions in the framework of the SU (2) L × U (1) model. Highly polarized “surface” μ + from the TRIUMF M13 beamline will enter a large volume, high field superconducting magnet on axis and will stop in a thin target at its center. The e + from the muon decay will be precisely tracked in the magnetic field using small-cell planar drift chambers. This spectrometer has been simulated with GEANT and EGS4 and has been demonstrated to meet the precision requirements.
122945711
A precision measurement of muon decay