1,558 research outputs found
New GUT predictions for quark and lepton mass ratios confronted with phenomenology
Group theoretical factors from GUT symmetry breaking can lead to predictions
for the ratios of quark and lepton masses (or Yukawa couplings) at the
unification scale. Due to supersymmetric (SUSY) threshold corrections the
viability of such predictions can depend strongly on the SUSY parameters. For
three common minimal SUSY breaking scenarios with anomaly, gauge and gravity
mediation we investigate which GUT scale ratios , ,
and are allowed when phenomenological constraints from
electroweak precision observables, physics, , mass-limits on
sparticles from direct searches as well as, optionally, constraints from the
observed dark matter density are taken into account. We derive possible new
predictions for the GUT scale mass ratios and compare them with the
phenomenologically allowed ranges. We find that new GUT scale predictions such
as or 6 and or 2 are often favoured
compared to the ubiquitous relations or . They
are viable for characteristic SUSY scenarios, testable at the CERN LHC and
future colliders.Comment: 33 pages, 5 figures; references added; version to appear in Phys.
Rev.
Measurement of inclusive electron cross section in collisions at TRISTAN
We have studied open charm production in collisions with the
TOPAZ detector at the TRISTAN collider. In this study, charm
quarks were identified by electrons (and positrons) from semi-leptonic decays
of charmed hadrons. The data corresponded to an integrated luminosity of 95.3
pb at a center-of-mass energy of 58 GeV. The results are presented as
the cross sections of inclusive electron production in
collisions with an anti-tag condition, as well as the subprocess cross
sections, which correspond to resolved-photon processes. The latter were
measured by using a sub-sample with remnant jets. A comparison with various
theoretical predictions based on direct and resolved-photon processes showed
that our data prefer that with relatively large gluon contents in a photon at
small , with the next-to-leading order correction, and with a
charm-quark mass of 1.3 GeV.Comment: 26 pages, Latex format (article), 5 figures included, to be published
in Phys. Lett.
A Measurement of the Cross Section in Two-Photon Processes
We have measured the inclusive production cross section in a
two-photon collision at the TRISTAN collider. The mean of
the collider was 57.16 GeV and the integrated luminosity was 150 . The
differential cross section () was obtained in the
range between 1.6 and 6.6 GeV and compared with theoretical predictions, such
as those involving direct and resolved photon processes.Comment: 8 pages, Latex format (article), figures corrected, published in
Phys. Rev. D 50 (1994) 187
Production in Two-Photon Processes at TRISTAN
We have carried out an inclusive measurement of production
in two-photon processes at TRISTAN. The mean was 58 GeV and the
integrated luminosity was 199 pb. High-statistics samples were
obtained under such conditions as no-, anti-electron, and remnant-jet tags. The
remnant-jet tag, in particular, allowed us, for the first time, to measure the
cross sections separately for the resolved-photon and direct processes.Comment: 20 pages, Latex format, 4 figures and KEK-mark included. Table 1
revised. To be published in Phys. Lett.
Search for neutrinoless tau decays tau -> 3l and tau -> l K0S
Neutrinoless tau-lepton decays into either three leptons (tau- -> l1- l2 l3)
or one lepton and one K0S meson(tau- -> l- K0S) where lepton l means either an
electron or muon, have been searched for using 48.6 fb^{-1} of data collected
with the Belle detector at the KEKB e+e- collider. No evidence for candidate
decays are found in any channel. Therefore we set 90% confidence level upper
limits on the branching fraction for 8 different decay modes. These limits are
more stringent than those set previously and reach to the 10^{-7} level.Comment: Invited talk at the Seventh International Workshop on Tau Lepton
Physics (TAU02), Santa Cruz, Ca, USA, Sept 2002, 7 pages, LaTeX, 3 eps
figure
Multiple Interactions in Two-Photon Collisions
We compute cross sections for events where two pairs of partons scatter off
each other in the same reaction, giving rise to at least 3
high--{\mbox{}} jets. Unlike in {\mbox{}}\ collisions we find
the signal to lie well above the background from higher order QCD processes. If
the usual ``eikonaliztion" assumption is correct, the signal should be readily
observable at LEP2, and might already be detectable in data taken at TRISTAN.Comment: 8 pages, plain LaTeX, 2 figures (not included). A compressed PS file
of the entire paper, including figures, can be obtained via anonymous ftp
from ftp://phenom.physics.wisc.edu/pub/preprints/1995/madph-95-921.ps.
Measurement of the cross-section and forward-backward charge asymmetry for the b and c-quark in e+e- annihilation with inclusive muons at sqrt(s) = 58 GeV
We have studied inclusive muon events using all the data collected by the
TOPAZ detector at sqrt(s)=58 GeV with an integrated luminosity of 273pb-1. From
1328 inclusive muon events, we measured the ratio R_qq of the cross section for
qq-bar production to the total hadronic cross section and forward-backward
asymmetry A^q_FB for b and c quarks. The obtained results are R_bb =
0.13+-0.02(stat)+-0.01(syst), R_cc = 0.36+-0.05(stat)+-0.05(syst), A^b_FB =
-0.20+-0.16(stat)+-0.01(syst) and A^c_FB = -0.17+-0.14(stat)+-0.02(syst), in
fair agreement with a prediction of the standard model.Comment: To be published in EPJ C. 24 pages, 12 figure
Complete Next to Leading Order QCD Corrections to the Photon Structure Functions and
We present the complete NLO QCD analysis of the photon structure functions
and for a real photon target. In
particular we study the heavy flavor content of the structure functions which
is due to two different production mechanisms, namely collisions of a virtual
photon with a real photon, and with a parton. We observe that the charm
contributions are noticeable for as well as
in the x-region studied.Comment: Latex 34 pages, 24 figures, uuencoded, attached at end, ITP-SB-93-46,
FERMILAB-Pub-93/240-T, SMU HEP 93-1
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