The equation of state for a degenerate gas of fermions at zero temperature in the non relativistic case is a polytrope, i.e. $p=gamma rho^{5/3}/m_F^{8/3}$. If dark matter is modelled by such non interacting fermion, this dependence in the mass of the
fermion $m_F$ explains why if dark matter is very heavy the effective pressure of dark matter is negligible. Nevertheless, if the mass of the dark matter is very small, the effective pressure can be very large, and thus, a system of self-gravitating fermions can be formed. In this work we model the dark matter halo of the Milky-Way by solving the Tolman-Oppenheimer-Volkoff equations, with the equation of state for a partially degenerate ultralight non interacting fermion. It is found that in order to fit its rotational velocity curve of the Milky Way, the mass of the fermion should be in the range $29 ~mbox{eV} < m_F < 33~$eV. Moreover, the central density is constrained to be in the range of $46 < rho_0<61$ GeV/cm$^3$. The fermionic dark matter halo has a very different profile as compared with the standard Navarro-Frenk-White profile, thus, the possible indirect signals for annihilating dark matter may change by orders of magnitude. We found bounds for the annihilation cross section in this case by using the Saggitarius A* spectral energy distribution. Those limits are very strong confirming the idea that the lighter the dark matter particle is, the darkest it becomes.
Massive neutrinos can have helicity $s_{parallel} eq -1$. Neutrino helicity changes when the neutrino interacts with an external magnetic field and it is possible that the left-handed neutrinos born inside the Sun or a supernova could leave their sou
rces with a different helicity. Since Dirac and Majorana neutrinos have different cross sections in the scattering on electrons for different neutrino helicities, a change in the final neutrino helicity may generate a different number of events and spectra in terrestrial detectors when astrophysical neutrinos have travelled regions with strong magnetic fields. In this work, we show that looking for these effects in solar neutrinos, it could be possible to set bounds in the neutrino properties such as the neutrino magnetic moment. Furthermore, for neutrinos coming from a supernova, we show that even in the case of an extremely small neutrino magnetic moment, $mu_ u sim 10^{-19}mu_B$, there will be measurable differences in both the number of events and in the spectra of Majorana and Dirac neutrinos.
It is well known that Majorana neutrinos have a pure axial neutral current interaction while Dirac neutrinos have the standard vector-axial interaction. In spite of this crucial difference, usually Dirac neutrino processes differ from Majorana proces
ses by a term proportional to the neutrino mass, resulting in almost unmeasurable observations of this difference. In the present work we show that once the neutrino polarization evolution is considered, there are clear differences between Dirac and Majorana scattering on electrons. The change of polarization can be achieved in astrophysical environments with strong magnetic fields. Furthermore, we show that in the case of unpolarized neutrino scattering onto polarized electrons, this difference can be relevant even for large values of the neutrino energy.
If dark matter is mainly composed of axions, the density distribution can be nonuniformly distributed, being clumpy instead. By solving the Einstein-Klein-Gordon system of a scalar field with the potential energy density of an axionlike particle, we
obtain the maximum mass of the self-gravitating system made of axions, called axion stars. The collision of axion stars with neutron stars may release the energy of axions due to the conversion of axions into photons in the presence of the neutron stars magnetic field. We estimate the energy release and show that it should be much less than previous estimates.Future data from femtolensing should strongly constrain this scenario.
Motivated by the stringent flux limits for UHE neutrinos coming from gamma ray burst or active galactic nuclei, we explore the possibility that the active neutrinos generated in such astrophysical objects could oscillate to sterile right handed state
s due to a neutrino magnetic moment mu_nu. We find that a value as small as mu_nu ~1E-15 mu_B could produce such a transition thanks to the intense magnetic fields that are expected in these objects.
We analyze the different parametrizations of a general four-zero texture mass matrices for quarks and leptons, that are able to reproduce the CKM and PMNS mixing matrices. This study is done through a Chi-Square analysis. In quark sector, only four s
olutions are found to be compatible with CKM mixing matrix. In leptonic sector, using the last experimental results about the mixing angles in the neutrino sector, our Chi-Square analysis shows a preferred value for m_nu_3 to be around 0.05 eV independently of the parametrization of the four-zero texture mass matrices chosen for the charged leptons and neutrinos.
The emittance preservation in the Beam Delivery System (BDS) is one of the major challenges in CLIC. The fast detuning of the final focus optics requires an on-line tuning procedure in order to keep luminosity close to the maximum. Different tuning t
echniques have been applied to the CLIC BDS and in particular to the Final Focus System (FFS) in order to mitigate static and dynamic imperfections. Some of them require a fast luminosity measurement. Here we study the possibility to use beam-beam backgrounds processes at CLIC 3 TeV CM energy as fast luminosity signal. In particular the hadrons multiplicity in the detector region is investigated.
We have analyzed the electron anti-neutrino scattering off electrons and the electron anti-neutrino-nuclei coherent scattering in order to obtain constraints on tensorial couplings. We have studied the formalism of non-standard interactions (NSI), as
well as the case of Unparticle physics. For our analysis we have focused on the recent TEXONO collaboration results and we have obtained current constraints to possible electron anti-neutrino-electron tensorial couplings in both new physics formalisms. The possibility of measuring for the first time electron anti-neutrino-nucleus coherent scattering and its potential to further constrain electron anti-neutrino-quark tensorial couplings is also discussed.
Constraints to the mass of a scalar field and the strength of its self-interacting coupling constant are obtained. This was done using observations of stellar dynamics at the center of our galaxy and by assuming that the dark compact object responsib
le of such dynamics is a boson star and not a supermassive black hole. We show that if such scalar field represents a spin-zero particle with cross section high enough to be considered collisional dark matter, there is a region of parameters compatible with both conditions: that the scalar field play the role of collisional dark matter and that it can form objects with the mass and compactness compatible with stellar kinematics.
We study the possible suppression of the extragalactic neutrino flux due to a nonstandard interaction during its propagation. In particular, we study neutrino interaction with an ultra-light scalar field dark matter. It is shown that the extragalacti
c neutrino flux may be suppressed by such an interaction, leading to a new mechanism to reduce the ultra-high energy neutrino flux. We study both the cases of non-self-conjugate as well as self-conjugate dark matter. In the first case, the suppression is independent of the neutrino and dark matter masses. We conclude that care must be taken when explaining limits on the neutrino flux through source acceleration mechanisms only, since there could be other mechanisms for the reduction of the neutrino flux.
