17,079 research outputs found
Rapidity and energy dependence of average transverse momentum and particle density in saturation models
Saturation models -- colour glass condensate and string percolation -- impose
a strict relation between the average transverse momentum, , and the
rapidity particle densities, dn/dy. By combining this relation with an
appropriate evolution equation for dn/dy, and imposing energy-momentum
conservation, we obtain a fair description of data, for generic AB collisions
(hadron-hadron, hadron-nucleus and nucleus-nucleus) at all rapidities and
(high) energies. Predictions are given for the LHC.Comment: 16 pages, 4 figures, 2 table
Closing the Symmetry at Electroweak Scale
We show that some models with gauge
symmetry can be realized at the electroweak scale and that this is a
consequence of an approximate global symmetry. This symmetry
implies a condition among the vacuum expectation value of one of the neutral
Higgs scalars, the 's coupling constant, , the sine of the weak
mixing angle , and the mass of the boson, . In the limit
in which this symmetry is valid it avoids the tree level mixing of the
boson of the Standard Model with the extra boson. We have verified
that the oblique parameter is within the allowed range indicating that the
radiative corrections that induce such a mixing at the 1-loop level are small.
We also show that a custodial symmetry implies that in some of
the models we have to include sterile (singlets of the 3-3-1 symmetry)
right-handed neutrinos with Majorana masses, being the see-saw mechanism
mandatory to obtain light active neutrinos. Moreover, the approximate
symmetry implies that the extra non-standard
particles of these 3-3-1 models can be considerably lighter than it had been
thought before so that new physics can be really just around the corner.Comment: 32 pages, no figure, RevTeX. Some typos correcte
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