13 research outputs found
Implications of a solar-system population of massive 4th generation neutrinos for underground searches of monochromatic neutrino-annihilation signals
It has been recently pointed out that any primary galactic population of
Weakly Interacting Massive Particles (WIMP) generates, through collisions with
solar matter, a secondary population of ``slow'' WIMPs trapped in the inner
solar system. We show that taking into account this ``slow'' solar-system
population dramatically enhances the possibility to probe the existence of
stable massive neutrinos (of a 4th generation) in underground neutrino
experiments. Our work suggests that a reanalysis of existing underground
neutrino data should be able to bring extremely tight constraints on the
possible existence of a stable massive 4th neutrino.Comment: 15 pages, 4 figure
Invisible Higgs Boson Decay into Massive Neutrinos of 4th Generation
Results from several recent experiments provide inderect evidences in the
favor of existence of a 4th generation neutrino. Such a neutrino of mass about
50 GeV is compatible with current physical and astrophysical constraints and
well motivated in the framework of superstring phenomenology. If sufficiently
stable the existence of such a neutrino leads to the drastic change of Higgs
boson physics: for a wide range of Higgs boson masses the dominant mode of
Higgs boson decay is invisible and the branching ratios for the most promising
modes of Higgs boson search are significantly reduced. The proper strategy of
Higgs boson searches in such a framework is discussed. It is shown that in the
same framework the absence of a signal in the search for invisible Higgs boson
decay at LEP means either that the mass of Higgs is greater than 113.5 GeV or
that the mass difference between the Higgs mass and doubled neutrino mass is
small.Comment: 8 pages, 2 figure
Flavor Changing Neutral Currents involving Heavy Quarks with Four Generations
We study various FCNC involving heavy quarks in the Standard Model (SM) with
a sequential fourth generation. After imposing , and constraints, we find can be enhanced by an order of magnitude to ,
while decays can reach , which are orders of magnitude
higher than in SM. However,these rates are still not observable for the near
future.With the era of LHC approaching, we focus on FCNC decays involving
fourth generation and quarks. We calculate the rates for
loop induced FCNC decays , as well as
t^\prime\to tZ,\tH, tg, t\gamma. If is of order , tree level decay would dominate, posing a challenge
since -tagging is less effective. For ,
would tend to dominate, while could also open for heavier
, leading to thepossibility of quadruple- signals via . The FCNC decays could still dominate if
is just above 200 GeV. For the case of , ingeneral would be dominant, hence it behaves like a heavy top. For both and
, except for the intriguing light case, FCNC decays are in the
range, and are quite detectable at the LHC.For a possible
future ILC, we find the associated production of FCNC ,
are below sensitivity, while
and can be better probed.Tevatron Run-II can still probe the
lighter or scenario. LHC would either discover the fourth generation
and measure the FCNC rates, or rule out the fourth generation conclusively.Comment: 31 pages, 15 eps figures, version to appear in JHE
May heavy neutrinos solve underground and cosmic ray puzzles?
Primordial Heavy neutrinos of 4th generation might explain different astrophysical puzzles: indeed the simplest 4th neutrino scenario may be still consistent with known 4th neutrino physics, cosmic ray anti-matter and gamma fluxes and signals in underground detectors for a very narrow neutrino mass windows (46-47 GeV). We have analyzed extended Heavy neutrino models related to the clumpiness of neutrino density, new interactions in Heavy neutrino annihilation, neutrino asymmetry, neutrino decay. We found that in these models the underground signals maybe better combined with the cosmic ray imprint leading to a wider windows for neutrino mass (46-75 GeV) coinciding with the whole range allowed from uncertainties of electro-weak parameters
Dark Coulomb binding of heavy neutrinos of fourth family
International audienceDirect dark matter searches put severe constraints on the weakly interacting massive particles (WIMPs). These constraints cause serious troubles for the model of stable neutrino of fourth generation with mass around 50GeV. Though the calculations of primordial abundance of these particles make them in the charge symmetric case a sparse subdominant component of the modern dark matter, their presence in the universe would exceed the current upper limits by several orders of the magnitude. However, if quarks and leptons of fourth generation possess their own Coulomb-like y-interaction, recombination of pairs of heavy neutrinos and antineutrinos and their annihilation in the âneutriniumâ atoms can play important role in their cosmological evolution, reducing their modern abundance far below the experimental upper limits. The model of stable fourth generation assumes that the dominant part of dark matter is explained by excessive ĆȘ antiquarks, forming (ĆȘĆȘĆȘ)ââ charged clusters, bound with primordial helium in nuclear-interacting O-helium (OHe) dark atoms. The y charge conservation implies generation of the same excess of fourth generation neutrinos, potentially dangerous WIMP component of this scenario. We show that due to y-interaction recombination of fourth neutrinos with OHe hides these WIMPs from direct WIMP searches, leaving the negligible fraction of free neutrinos, what makes their existence compatible with the experimental constraints