4,606 research outputs found
Hadroproduction of the Chi1 and Chi2 States of Charmonium in 800 GeV/c Proton-Silicon Interactions
The cross sections for the hadroproduction of the Chi1 and Chi2 states of
charmonium in proton-silicon collisions at sqrt{s}=38.8 GeV have been measured
in Fermilab fixed target Experiment 771. The Chi states were observed via their
radiative decay to J/psi+gamma, where the photon converted to e+e- in the
material of the spectrometer. The measured values for the Chi1 and Chi2 cross
sections for x_F>0 are 263+-69(stat)+-32(syst) and 498+-143(stat)+-67(syst) nb
per nucleon respectively. The resulting sigma(Chi1}/sigma(Chi2) ratio of
0.53+-0.20(stat)+-0.07(syst), although somewhat larger than most theoretical
expectations, can be accomodated by the latest theoretical estimates.Comment: 4 pages, 4 figure
B Physics at the Tevatron: Run II and Beyond
This report provides a comprehensive overview of the prospects for B physics
at the Tevatron. The work was carried out during a series of workshops starting
in September 1999. There were four working groups: 1) CP Violation, 2) Rare and
Semileptonic Decays, 3) Mixing and Lifetimes, 4) Production, Fragmentation and
Spectroscopy. The report also includes introductory chapters on theoretical and
experimental tools emphasizing aspects of B physics specific to hadron
colliders, as well as overviews of the CDF, D0, and BTeV detectors, and a
Summary.Comment: 583 pages. Further information on the workshops, including
transparencies, can be found at the workshop's homepage:
http://www-theory.lbl.gov/Brun2/. The report is also available in 2-up
http://www-theory.lbl.gov/Brun2/report/report2.ps.gz or chapter-by-chapter
http://www-theory.lbl.gov/Brun2/report
Observation of Double cc bar Production in e+ e- Annihilation at sqrt{s} ~ 10.6 GeV
We report the observation of prompt J/psi via double ccbar production from
the e+e- continuum. In this process one ccbar pair fragments into a J/psi meson
while the remaining pair either produces a bound charmonium state or fragments
into open charm. Both cases have been observed: the first by studying the mass
spectrum of the system recoiling against the J/psi, and the second by
reconstructing the J/psi together with a charmed meson. We find cross-sections
of \sigma(e+ e- -> J/psi eta_c (gamma)) * BR (eta_c -> >=4 charged) = 0.033
(+0.007 -0.006)(stat) \pm 0.009(syst)pb and \sigma(e+ e- -> J/psi D*+ X) = 0.53
(+0.19 -0.15)(stat) \pm 0.14(syst) pb, and infer \sigma(e+ e- -> J/psi c cbar)
/ \sigma(e+ e- -> J/psi X) = 0.59 (+0.15 -0.13)(stat) \pm 0.12(syst). These
results are obtained from a 46.2/fb data sample collected near the Upsilon(4S)
resonance, with the Belle detector at the KEKB asymmetric energy e+ e-
collider.Comment: 7 pages, 2 figures, to be submitted to Physical Review Letter
Production of Prompt Charmonia in Annihilation at GeV
The production of prompt , , and is
studied using a data sample collected with the Belle detector at
the and 60 MeV below the resonance. The yield of prompt
mesons in the sample is compatible with that of continuum
production; we set an upper limit at the 95% confidence level, and find pb. The cross-sections for prompt
and direct are measured. The momentum spectrum, production
angle distribution and polarization are studied.Comment: submitted to Phys. Rev. Let
Observation of Mixing-induced CP Violation in the Neutral B Meson System
This report describes an observation of mixing-induced CP violation and a
measurement of the CP violation parameter, sin(2phi_1), with the Belle detector
at the KEKB asymmetric e+e- collider. Using a data sample of 29.1 fb-1 recorded
on the Upsilon(4S) resonance that contains 31.3 million BBbar pairs, we
reconstruct decays of neutral B mesons to the following CP eigenstates: J/psi
K_S^0, psi(2S) K_S^0, chi_c1 K_S^0, eta_c K_S^0, J/psi K_L^0 and J/psi K^*0.
The flavor of the accompanying B meson is identified by combining information
from primary and secondary leptons, K+/- mesons, lambda baryons, slow and fast
pions. The proper-time interval between the two B meson decays is determined
from the distance between the two decay vertices measured with a silicon vertex
detector. The result sin(2phi_1) = 0.99 +/- 0.14(stat) +/- 0.06(syst) is
obtained by applying a maximum likelihood fit to the 1137 candidate events. We
conclude that there is large CP violation in the neutral B meson system. A zero
value for sin(2phi_1) is ruled out by more than six standard deviations.Comment: 25 pages, 16 figures, accepted for publication in Physical Review
Study of CP-Violating Asymmetries in B0 -> pi+pi- Decays
We present a measurement of CP-violating asymmetries in B0 -> pi+pi- decays
based on a 41.8 fb-1 data sample collected at the Upsilon(4S) resonance with
the Belle detector at the KEKB asymmetric-energy e+e- collider. We fully
reconstruct one neutral B meson as a B0 -> pi+pi- CP eigenstate and identify
the flavor of the accompanying B meson from its decay products. From the
asymmetry in the distribution of the time intervals between the two B meson
decay points, we obtain the CP-violating asymmetry parameters Spipi = -1.21
+0.38/-0.27(stat) +0.16/-0.13(syst) and Apipi = +0.94 +0.25/-0.31(stat) +/-
0.09(syst).Comment: 9 pages, 2 figures, accepted for publication in Physical Review
Letter
Measurement of the lepton charge asymmetry in W-boson decays produced in p-pbar collisions
We describe a measurement of the charge asymmetry of leptons from W boson
decays in the rapidity range 0 enu, munu events from
110+/-7 pb^{-1}of data collected by the CDF detector during 1992-95. The
asymmetry data constrain the ratio of d and u quark momentum distributions in
the proton over the x range of 0.006 to 0.34 at Q2 \approx M_W^2. The asymmetry
predictions that use parton distribution functions obtained from previously
published CDF data in the central rapidity region (0.0<|y_l|<1.1) do not agree
with the new data in the large rapidity region (|y_l|>1.1).Comment: 13 pages, 3 tables, 1 figur
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