557 research outputs found
E835 at FNAL: Charmonium Spectroscopy in Annihilations
I present preliminary results on the search for in its
and decay modes. We observe an excess of \eta_c\gamma{\cal P} \sim 0.001M=3525.8 \pm 0.2 \pm 0.2
\Gamma\leq10.6\pm 3.7\pm3.4(br) <
\Gamma_{\bar{p}p}B_{\eta_c\gamma} < 12.8\pm 4.8\pm4.5(br) J/\psi\pi^0$ mode.Comment: Presented at the 6th International Conference on Hyperons, Charm and
Beauty Hadrons (BEACH 2004), Chicago(Il), June 27-July 3,200
Interference Study of the chi_c0 (1^3P_0) in the Reaction Proton-Antiproton -> pi^0 pi^0
Fermilab experiment E835 has observed proton-antiproton annihilation
production of the charmonium state chi_c0 and its subsequent decay into pi^0
pi^0. Although the resonant amplitude is an order of magnitude smaller than
that of the non-resonant continuum production of pi^0 pi^0, an enhanced
interference signal is evident. A partial wave expansion is used to extract
physics parameters. The amplitudes J=0 and 2, of comparable strength, dominate
the expansion. Both are accessed by L=1 in the entrance proton-antiproton
channel. The product of the input and output branching fractions is determined
to be B(pbar p -> chi_c0) x B(chi_c0 -> pi^0 pi^0)= (5.09 +- 0.81 +- 0.25) x
10^-7.Comment: 4 pages, 4 figures, Accepted by PRL (July 2003
Precision measurements of the total and partial widths of the psi(2S) charmonium meson with a new complementary-scan technique in antiproton-proton annihilations
We present new precision measurements of the psi(2S) total and partial widths
from excitation curves obtained in antiproton-proton annihilations by Fermilab
experiment E835 at the Antiproton Accumulator in the year 2000. A new technique
of complementary scans was developed to study narrow resonances with
stochastically cooled antiproton beams. The technique relies on precise
revolution-frequency and orbit-length measurements, while making the analysis
of the excitation curve almost independent of machine lattice parameters. We
study the psi(2S) meson through the processes pbar p -> e+ e- and pbar p ->
J/psi + X -> e+ e- + X. We measure the width to be Gamma = 290 +- 25(sta) +-
4(sys) keV and the combination of partial widths Gamma_e+e- * Gamma_pbarp /
Gamma = 579 +- 38(sta) +- 36(sys) meV, which represent the most precise
measurements to date.Comment: 17 pages, 3 figures, 3 tables. Final manuscript accepted for
publication in Phys. Lett. B. Parts of the text slightly expanded or
rearranged; results are unchange
Spacings of Quarkonium Levels with the Same Principal Quantum Number
The spacings between bound-state levels of the Schr\"odinger equation with
the same principal quantum number but orbital angular momenta
differing by unity are found to be nearly equal for a wide range of power
potentials , with . Semiclassical approximations are in accord with this behavior. The
result is applied to estimates of masses for quarkonium levels which have not
yet been observed, including the 2P states and the 1D
states.Comment: 20 pages, latex, 3 uuencoded figures submitted separately (process
using psfig.sty
Highlights from the Pierre Auger Observatory
The Pierre Auger Observatory is the world's largest cosmic ray observatory.
Our current exposure reaches nearly 40,000 km str and provides us with an
unprecedented quality data set. The performance and stability of the detectors
and their enhancements are described. Data analyses have led to a number of
major breakthroughs. Among these we discuss the energy spectrum and the
searches for large-scale anisotropies. We present analyses of our X
data and show how it can be interpreted in terms of mass composition. We also
describe some new analyses that extract mass sensitive parameters from the 100%
duty cycle SD data. A coherent interpretation of all these recent results opens
new directions. The consequences regarding the cosmic ray composition and the
properties of UHECR sources are briefly discussed.Comment: 9 pages, 12 figures, talk given at the 33rd International Cosmic Ray
Conference, Rio de Janeiro 201
The Pierre Auger Observatory III: Other Astrophysical Observations
Astrophysical observations of ultra-high-energy cosmic rays with the Pierre
Auger ObservatoryComment: Contributions to the 32nd International Cosmic Ray Conference,
Beijing, China, August 201
Measurement of the Depth of Maximum of Extensive Air Showers above 10^18 eV
We describe the measurement of the depth of maximum, Xmax, of the
longitudinal development of air showers induced by cosmic rays. Almost four
thousand events above 10^18 eV observed by the fluorescence detector of the
Pierre Auger Observatory in coincidence with at least one surface detector
station are selected for the analysis. The average shower maximum was found to
evolve with energy at a rate of (106 +35/-21) g/cm^2/decade below 10^(18.24 +/-
0.05) eV and (24 +/- 3) g/cm^2/decade above this energy. The measured
shower-to-shower fluctuations decrease from about 55 to 26 g/cm^2. The
interpretation of these results in terms of the cosmic ray mass composition is
briefly discussed.Comment: Accepted for publication by PR
The Luminosities and Distance Scales of Type II Cepheid and RR Lyrae variables
Infrared and optical absolute magnitudes are derived for the type II Cepheids
kappa Pav and VY Pyx from revised Hipparcos parallaxes and for kappa Pav, V553
Cen and SW Tau from pulsation parallaxes. Phase-corrected JHK mags are given
for 142 RR Lyrae variables based on 2MASS data. RR Lyrae itself is overluminous
compared with LMC RR Lyraes at the classical Cepheid modulus (18.39) consistent
with a prediction of Catalan and Cortes. V553 Cen and SW Tau deviate by only
0.02 mag in the mean from the Matsunaga PL(K) relation for globular cluster
type II Cepheids with a zero-point based on the same LMC modulus. Comparing
directly these two stars with type II Cepheids in the LMC and in the Galactic
Bulge leads to an LMC modulus of 18.37\pm0.09 and a distance to the Galactic
Centre of 7.64\pm 0.21kpc. Kappa Pav may be a binary. V553 Cen and SW Tau show
that at optical wavelengths PL relations are wider for field stars than for
those in globular clusters (abridged).Comment: 29 pages, 13 figures, accepted for MNRA
A search for point sources of EeV photons
Measurements of air showers made using the hybrid technique developed with
the fluorescence and surface detectors of the Pierre Auger Observatory allow a
sensitive search for point sources of EeV photons anywhere in the exposed sky.
A multivariate analysis reduces the background of hadronic cosmic rays. The
search is sensitive to a declination band from -85{\deg} to +20{\deg}, in an
energy range from 10^17.3 eV to 10^18.5 eV. No photon point source has been
detected. An upper limit on the photon flux has been derived for every
direction. The mean value of the energy flux limit that results from this,
assuming a photon spectral index of -2, is 0.06 eV cm^-2 s^-1, and no celestial
direction exceeds 0.25 eV cm^-2 s^-1. These upper limits constrain scenarios in
which EeV cosmic ray protons are emitted by non-transient sources in the
Galaxy.Comment: 28 pages, 10 figures, accepted for publication in The Astrophysical
Journa
Reconstruction of inclined air showers detected with the Pierre Auger Observatory
We describe the method devised to reconstruct inclined cosmic-ray air showers
with zenith angles greater than detected with the surface array of
the Pierre Auger Observatory. The measured signals at the ground level are
fitted to muon density distributions predicted with atmospheric cascade models
to obtain the relative shower size as an overall normalization parameter. The
method is evaluated using simulated showers to test its performance. The energy
of the cosmic rays is calibrated using a sub-sample of events reconstructed
with both the fluorescence and surface array techniques. The reconstruction
method described here provides the basis of complementary analyses including an
independent measurement of the energy spectrum of ultra-high energy cosmic rays
using very inclined events collected by the Pierre Auger Observatory.Comment: 27 pages, 19 figures, accepted for publication in Journal of
Cosmology and Astroparticle Physics (JCAP
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