3,638 research outputs found
QCD corrections to e+ e- --> 4 jets
We report on the next-to-leading order QCD calculation for e+ e- --> 4 jets.
We explain some modern techniques which have been used to calculate the
one-loop amplitudes efficiently. We further report on the general purpose
numerical program ``Mercutio'', which can be used to calculate any infrared
safe four-jet quantity in electron-positron annihilation at next-to-leading
order.Comment: 4 pages, talk given at the UK Phenomenology Workshop on Collider
Physics, Durham, 19-24 September 199
Strong Interaction Effects in Scalar Top Production
We discuss effects of fragmentation and hard gluon radiation on the signal
for the pair production of the lighter scalar top eigenstate at
e^+e^- colliders. The main emphasis is on scenarios with small stop--LSP mass
splitting, where strong interaction effects can considerably modify kinematical
properties of the final state.Comment: 4 pages, 2 figures, uses sprocl.sty. Proceedings of the LCWS99,
International Workshop on Linear Colliders, Sitges, Spain (May 1999) and
Particles in Astrophysics and Cosmology: From Theory to Observation,
Valencia, Spain (May 1999
Non-perturbative non-locality: correlators in euclidean position space
Using an OPE modification, which takes non-perturbative non-locality into
account, the difference and sum of vector and axial-vector correlators are
evaluated in euclidean position space. For distances up to 0.8 fm the
calculated behavior is close to the instanton liquid result and the ALEPH data,
in contrast to the implications of the conventional OPE.Comment: 4 pages, 2 figure
Investigation of Quark-Antiquark Interaction Properties using Leading Particle Measurements in e+e- Annihilation
Measurements of heavy quark production in electron-positron collisions are
used to analyse the strong interactions between quarks and anti-quarks. A
scaling behaviour is observed in distributions of the rapidity change of D*,
B*, and B mesons. From these distributions information is obtained on the
hadron formation time, effective quark masses, and the potential between
quark-antiquark pairs. Predictions for fragmentation functions are presented.Comment: 10 pages, 4 figures, fig.2 references added, revised version accepted
by Physics Letters
Prospects for New Physics at the LHC
High-energy collisions at the LHC are now starting. The new physics agenda of
the LHC is reviewed, with emphasis on the hunt for the Higgs boson (or whatever
replaces it) and supersymmetry. In particular, the prospects for discovering
new physics in the 2010-2011 run are discussed.Comment: 13 pages, 9 figures, Invited Talk at Conference in Honor of Murray
Gell-Mann's 80th Birthday, on Quantum Mechanics, Elementary Particles,
Quantum Cosmology and Complexity, Nanyang Executive Centre, NTU, Singapore,
24th-26th February 201
Measurements of the QCD Colour Factors at LEP
A summary of the measurements of the QCD colour factors at LEP is presented.
Such measurements provide a test of the gauge group structure underlying the
theory of strong interactions. A variety of methods have been applied by the
various experiments, and perfect consistency with the expectation of QCD with
SU(3) as gauge group is found.Comment: 9 pages, Latex, Talk presented at the 5th Topical Seminar on The
Irresistible Rise of the Standard Model, San Miniato, Italy, April 199
Experimental Summary on Hadronic Decays: A TAU98 Review
Selected results on hadronic decays of the tau lepton from the TAU98 Workshop
are reviewed. A comprehensive picture emerges for strange particle branching
fractions, and exploration of resonant substructure of both strange and
non-strange decays is seen to have matured substantially.Comment: 10 pages, postscript file also available through
http://w4.lns.cornell.edu/public/CLN
Non-perturbative effective model for the Higgs sector of the Standard Model
A non-perturbative effective model is derived for the Higgs sector of the
standard model, described by a simple scalar theory. The renormalized couplings
are determined by the derivatives of the Gaussian Effective Potential that are
known to be the sum of infinite bubble graphs contributing to the vertex
functions. A good agreement has been found with strong coupling lattice
simulations when a comparison can be made
Search for the Standard Model Higgs Boson at LEP
One of the missions of the LEP program was the search for the Standard Model
Higgs Boson. The skillful operation of the machine in the year 2000, the final
year of operation, has allowed the four collaborations ALEPH, DELPHI, L3 and
OPAL to collect 536/pb of data at center-of-mass energies of 206 GeV or higher.
This data is used to probe the existence of the Higgs boson up to a mass of
around 115 GeV. Tantalizing candidates have been observed in excess over the
Standard Model predictions, but without enough statistical power to claim a
discovery. A Higgs boson lighter than 114.4 GeV is hence excluded at 95%
confidence level.Comment: 5 pages, 6 figures, to be published in the proceedings of the "5th
International Conference on Hyperons, Charm and Beauty Hadrons
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