283 research outputs found
A Scenario for Contact Interactions at HERA
The four fermion contact interactions, required to explain the anomalous HERA
result, could come from the exchange of new heavy (probably composite)
resonances. Depending on their charges and quantum numbers, one gets different
scenarios and finds that many of these configurations are unsuitable. For
example, new neutral resonances seems to be disfavored by the data coming from
the TEVATRON, LEP 2 and atomic parity violation. These experiments allow only
few helicity combinations that cannot arise from neutral currents in a natural
way. On the contrary, a global large symmetry SU(8) * SU(8) (which is contained
in SU(16)) embeds some lepto-quarks of spin 1 that could give suitable four
fermion interactions (compatible with all other experiments) if these
resonances are the lightest new (probably composite) states with a mass
comparable to the scale of the contact interactions.Comment: 8 pages, LaTeX, no figur
Production of gauge bosons plus jets in hadronic collisions
A computational strategy and a collection of codes are presented for studying
multiparticle final states in hard hadronic collisions.Comment: 4 pages, 2 figures, talk given at ICHEP'02 (Amsterdam, 24-31 July
2002
Electroweak Precision Tests: A Concise Review
1. Introduction 2. Status of the Data 3. Precision Electroweak Data and the
Standard Model 4. A More General Analysis of Electroweak Data
4.1 Basic Definitions and Results
4.2 Experimental Determination of the Epsilon Variables
4.3 Comparing the Data with the Minimal Supersymmetric Standard Model 5.
Theoretical Limits on the Higgs Mass 6. ConclusionComment: Submitted to Int. Journal of Modern Physics
The tau forward-backward Asymmetry within Grand Unified Theories
We will study some possible non universal corrections that could affect
single measurements of the Weinberg angle sin^2(theta) (leaving the full
average essentially unchanged). We will concentrate on the class of the models
that introduces a new light gauge boson and an extended Higgs sector, but we
restrict the Higgs charges choice in order to automatically achieve zero mixing
at the tree level between the Z_0 and the Z'. This will more naturally keep
small the universal effects with a relatively light Z', but it will imply only
vector-like coupling between this boson and the standard fermions. A SO(10)
gauge boson which distinguishes between families can have such properties and
could explain a deviation in the tau forward-backward asymmetry without
affecting the tau polarization measurements at LEP.Comment: 10 pages, Late
How to Integrate Divergent Integrals: a Pure Numerical Approach to Complex Loop Calculations
Loop calculations involve the evaluation of divergent integrals.
Usually [1] one computes them in a number of dimensions different than four
where the integral is convergent and then one performs the analytical
continuation and considers the Laurent expansion in powers of epsilon =n-4. In
this paper we discuss a method to extract directly all coefficients of this
expansion by means of concrete and well defined integrals in a five dimensional
space. We by-pass the formal and symbolic procedure of analytic continuation;
instead we can numerically compute the integrals to extract directly both the
coefficient of the pole 1/epsilon and the finite part.Comment: 13 pages, 1 Postscript figur
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