6,127 research outputs found
Inverse type II seesaw mechanism and its signature at the LHC and ILC
The advent of the LHC, and the proposal of building future colliders as the
ILC, both programmed to explore new physics at the TeV scale, justifies the
recent interest in studying all kind of seesaw mechanisms whose signature lies
on such energy scale. The natural candidate for this kind of seesaw mechanism
is the inverse one. The conventional inverse seesaw mechanism is implemented in
an arrangement involving six new heavy neutrinos in addition to the three
standard ones. In this paper we develop the inverse seesaw mechanism based on
Higgs triplet model and probe its signature at the LHC and ILC. We argue that
the conjoint analysis of the LHC together with the ILC may confirm the
mechanism and, perhaps, infer the hierarchy of the neutrino masses.Comment: 24 pages, 22 figure
Five-Dimensional QED, Muon Pair Production and Correction to the Coulomb Potential
We consider QED in five dimensions in a configuration where matter is
localized on a 3-brane while foton propagates in the bulk. The idea is to
investigate the effects of the Kaluza-Klein modes of the photon in the
relativistic regime, but in low energy, and in the nonrelativistic regime. In
the relativistic regime, we calculate the cross section for the reaction . We compare our theoretical result with a precise
measurement of this cross section at GeV. As result, we
extract a lower bound on the size of the extra dimension. In the
nonrelativistic regime, we derive the contribution for the Coulomb potential
due to the whole tower of the Kaluza-Klein excited modes of the photon. We use
the modified potential to calculate the Rutherford scattering differential
cross section.Comment: minor changes, three new refs. added, to appear in IJMP
Comment on ``Majoron emitting neutrinoless double beta decay in the electroweak chiral gauge extensions''
We point out that if the majoron-like scheme is implemented within a 331
model, there must exist at least three different mass scales for the scalar
vacuum expectation values in the model.Comment: 4 pages, no figures, Revtex. To be published in Physical Review
Proper motions of ROSAT discovered isolated neutron stars measured with Chandra: First X-ray measurement of the large proper motion of RX J1308.6+2127/RBS 1223
The unprecedented spatial resolution of the Chandra observatory opens the
possibility to detect with relatively high accuracy proper motions at X-ray
wavelengths. We have conducted an astrometric study of three of the
"Magnificent Seven", the thermally emitting radio quiet isolated neutron stars
(INSs) discovered by ROSAT. These three INSs (RX J0420.0-5022, RX J0806.4-4123
and RX J1308.6+2127/RBS 1223) either lack an optical counterpart or have one
too faint to be used for astrometric purposes. We obtained ACIS observations 3
to 5 years apart to constrain or measure the displacement of the sources on the
X-ray sky using as reference the background of extragalactic or remote galactic
X-ray sources. Upper limits of 138 mas/yr and 76 mas/yr on the proper motion of
RX J0420.0-5022 and RX J0806.4-4123, respectively, have already been presented
in Motch et al. (2007). Here we report the very significant measurement (~ 10
sigma) of the proper motion of the third INS of our program, RX
J1308.6+2127/RBS1223. Comparing observations obtained in 2002 and 2007 reveals
a displacement of 1.1 arcsec implying a yearly proper motion of 223 mas, the
second fastest measured for the ROSAT discovered INSs. The source is rapidly
moving away from the galactic plane at a speed which precludes any significant
accretion of matter from the interstellar medium. Its transverse velocity of ~
740 (d/700pc) km/s might be the largest of the "Magnificent Seven" and among
the fastest recorded for neutron stars. RX J1308.6+2127/RBS1223 is thus a young
high velocity cooling neutron star. The source may have its origin in the
closest part of the Scutum OB2 association about 0.8 Myr ago, an age consistent
with that expected from cooling curves, but significantly younger than inferred
from pulse timing measurements (1.5 Myr).Comment: 3 pages, 2 figures, proceedings of the conference "40 Years of
Pulsars", 12-17 August 2007, Montreal, Canad
Sterile neutrino dark matter, CDMS-II and a light Higgs boson
We add a singlet right handed neutrino plus a charged and a neutral singlet
scalars to the standard model. This extension includes a discrete symmetry such
that we obtain a heavy sterile neutrino which couples only to the electron and
the new scalars. In this sense the singlet neutrino does not mix with ordinary
ones and thus has no effect on Big Bang Nucleosynthesis. However, such sterile
neutrino can be in equilibrium with electroweak particles in the early Universe
due to its couplings to electrons and also because the Higgs boson mixes with
the singlet scalars. We obtain that the sterile neutrino constitutes a dark
matter candidate and analyze its direct detection in the light of current
experiments. Our results show that if such a sterile neutrino is realized in
nature, and CDMS-II experiment confirms its positive signal, dark matter
demands a rather light Higgs boson with new Physics at some 500 GeV scale.Comment: 16 pages, 13 figures, uses axodraw.st
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