224 research outputs found
Nontriviality of the Linear Sigma Model
We consider techniques (based on an ultraviolet cutoff) used to prove that
the pure boson ( field theory is trivial and apply them instead to
the dynamically generated quark-level linear sigma model. This cutoff approach
leads to the conclusion that the latter field theory is in fact nontrivial.Comment: To be published in Eur. Phys. J.
Prospects for probing the gluon density in protons using heavy quarkonium hadroproduction
We examine carefully bottomonia hadroproduction in proton colliders,
especially focusing on the LHC, as a way of probing the gluon density in
protons. To this end we develop some previous work, getting quantitative
predictions and concluding that our proposal can be useful to perform
consistency checks of the parameterization sets of different parton
distribution functions.Comment: LaTeX, 14 pages, 6 EPS figure
Identifying the quark content of the isoscalar scalar mesons f_0(980), f_0(1370), and f_0(1500) from weak and electromagnetic processes
The assignments of the isoscalar scalar mesons f0(980), f0(1370), and
f0(1500) in terms of their qqbar substructure is still a matter of heated
dispute. Here we employ the weak and electromagnetic decays D(s)(+) to f0+pi(+)
and f0 two-photon decays, respectively, to identify the f0(980) and f0(1500) as
mostly ssbar, and the f0(1370) as dominantly nonstrange, in agreement with
previous work. The two-photon decays can be satisfactorily described with quark
as well as with meson loops, though the latter ones provide a less
model-dependent and more quantitative description.Comment: v1, 15 pages, plain LaTeX, 1 eps figure. v2, 18 pages, plain LaTeX
(figure included). More discussion, especially on the f0(1370) and its
empirical two-photon widt
Limits on WWgamma and WWZ Couplings from W Boson Pair Production
The results of a search for W boson pair production in pbar-p collisions at
sqrt{s}=1.8 TeV with subsequent decay to emu, ee, and mumu channels are
presented. Five candidate events are observed with an expected background of
3.1+-0.4 events for an integrated luminosity of approximately 97 pb^{-1}.
Limits on the anomalous couplings are obtained from a maximum likelihood fit of
the E_T spectra of the leptons in the candidate events. Assuming identical
WWgamma and WWZ couplings, the 95 % C.L. limits are -0.62<Delta_kappa<0.77
(lambda = 0) and -0.53<lambda<0.56 (Delta_kappa = 0) for a form factor scale
Lambda = 1.5 TeV.Comment: 10 pages, 1 figure, submitted to Physical Review
Probing BFKL Dynamics in the Dijet Cross Section at Large Rapidity Intervals in ppbar Collisions at sqrt{s}=1800 and 630 GeV
Inclusive dijet production at large pseudorapidity intervals (delta_eta)
between the two jets has been suggested as a regime for observing BFKL
dynamics. We have measured the dijet cross section for large delta_eta in ppbar
collisions at sqrt{s}=1800 and 630 GeV using the DO detector. The partonic
cross section increases strongly with the size of delta_eta. The observed
growth is even stronger than expected on the basis of BFKL resummation in the
leading logarithmic approximation. The growth of the partonic cross section can
be accommodated with an effective BFKL intercept of
a_{BFKL}(20GeV)=1.65+/-0.07.Comment: Published in Physical Review Letter
Search for bottom squarks in pbarp collisions at sqrt(s)=1.8 TeV
We report on a search for bottom squarks produced in pbarp collisions at
sqrt(s) = 1.8 TeV using the D0 detector at Fermilab. Bottom squarks are assumed
to be produced in pairs and to decay to the lightest supersymmetric particle
(LSP) and a b quark with branching fraction of 100%. The LSP is assumed to be
the lightest neutralino and stable. We set limits on the production cross
section as a function of bottom squark mass and LSP mass.Comment: 5 pages, Latex. submitted 3-12-1999 to PRD - Rapid Communicatio
Search for Squarks and Gluinos in Events Containing Jets and a Large Imbalance in Transverse Energy
Using data corresponding to an integrated luminosity of 79 pb-1, D0 has
searched for events containing multiple jets and large missing transverse
energy in pbar-p collisions at sqrt(s)=1.8 TeV at the Fermilab Tevatron
collider. Observing no significant excess beyond what is expected from the
standard model, we set limits on the masses of squarks and gluinos and on the
model parameters m_0 and m_1/2, in the framework of the minimal low-energy
supergravity models of supersymmetry. For tan(beta) = 2 and A_0 = 0, with mu <
0, we exclude all models with m_squark < 250 GeV/c^2. For models with equal
squark and gluino masses, we exclude m < 260 GeV/c^2.Comment: 10 pages, 3 figures, Submitted to PRL, Fixed typo on page bottom of
p. 6 (QCD multijet background is 35.4 events
A Quasi-Model-Independent Search for New Physics at Large Transverse Momentum
We apply a quasi-model-independent strategy ("Sleuth") to search for new high
p_T physics in approximately 100 pb^-1 of ppbar collisions at sqrt(s) = 1.8 TeV
collected by the DZero experiment during 1992-1996 at the Fermilab Tevatron.
Over thirty-two e mu X, W+jets-like, Z+jets-like, and 3(lepton/photon)X
exclusive final states are systematically analyzed for hints of physics beyond
the standard model. Simultaneous sensitivity to a variety of models predicting
new phenomena at the electroweak scale is demonstrated by testing the method on
a particular signature in each set of final states. No evidence of new high p_T
physics is observed in the course of this search, and we find that 89% of an
ensemble of hypothetical similar experimental runs would have produced a final
state with a candidate signal more interesting than the most interesting
observed in these data.Comment: 28 pages, 17 figures. Submitted to Physical Review
Search for Charged Higgs Bosons in Decays of Top Quark Pairs
We present a search for charged Higgs bosons in decays of pair-produced top
quarks using 109.2 +- 5.8 pb^-1 of data recorded from ppbar collisions at
sqrt{s} = 1.8 TeV by the D0 detector during 1992-96 at the Fermilab Tevatron.
No evidence is found for charged Higgs production, and most parts of the
[m(H+),tan(beta)] parameter space where the decay t -> bH+ has a branching
fraction close to or larger than that for t -> bW+ are excluded at 95%
confidence level. Assuming m(t) = 175 GeV and sigma(ppbar -> ttbar) = 5.5 pb,
for m(H+) = 60 GeV, we exclude tan(beta) 40.9.Comment: 11 pages, 3 figures, submitted to PR
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