679836
Constraints and tests of the OPERA superluminal neutrinos.
The superluminal neutrinos detected by OPERA indicate Lorentz invariance violation (LIV) of the neutrino sector at the order of 10(-5). We study the implications of the result in this work. We find that such a large LIV implied by OPERA data will make the neutrino production process π → μ + ν(μ) kinematically forbidden for a neutrino energy greater than about 5 GeV. The OPERA detection of neutrinos at 40 GeV can constrain the LIV parameter to be smaller than 3×10(-7). Furthermore, the neutrino decay in the LIV framework will modify the neutrino spectrum greatly. The atmospheric neutrino spectrum measured by the IceCube Collaboration can constrain the LIV parameter to the level of 10(-12). The future detection of astrophysical neutrinos of galactic sources is expected to be able to give an even stronger constraint on the LIV parameter of neutrinos.
118441224
Probing light stop pairs at the LHC
In this work, we study the light stop pair signals at the LHC. We explore the supersymmetry parameter space with nonuniversal gaugino and third-generation masses at the grand unified theory scale. Recent LHC supersymmetry search results based on 35 pb(-1) and 1 fb(-1) of data are implemented to put the limits on stop pair events. The dark matter relic density and direct detection constraints are also taken into account. Detailed simulations on the signals and background for some benchmark points are performed, and it is found that the stop pair signals usually escape the LHC search if the present cut conditions are used. We also explore the potential and sensitivity of ILC to probe such scenarios. It is found that the ILC can detect them with an integrated luminosity of a few tens of fb(-1).
118487966
Detecting interactions between dark matter and photons at high energy e(+)e(-) colliders
We investigate the sensitivity to the effective operators describing interactions between dark matter particles and photons at future high energy e+e(-) colliders via the gamma + is not an element of channel. Such operators could be useful to interpret the potential gamma-ray line signature observed by the Fermi-LAT. We find that these operators can be further tested at e(+)e(-) colliders by using either unpolarized or polarized beams. We also derive a general unitarity condition for 2 -> n processes and apply it to the dark matter production process e(+)e(-) -> chi chi gamma.
49215683
PAMELA data and leptonically decaying dark matter
Recently PAMELA released their first results on the positron and antiproton ratios. Stimulated by the new data, we studied the cosmic ray propagation models and calculated the secondary positron and antiproton spectra. The low energy positron ratio can be consistent with data in the convection propagation model. Above similar to 10 GeV PAMELA data shows a clear excess on the positron ratio. However, the secondary antiproton is roughly consistent with the data. The positron excess may be evidence of dark matter annihilation or decay. We compare the positron and antiproton spectra with the data by assuming that dark matter annihilates or decays into different final states. The PAMELA data actually excludes quark pairs being the main final states, and disfavors gauge boson final states. Only in the case of leptonic final states can the positron and antiproton spectra be explained simultaneously. We also compare the decaying and annihilating dark matter scenarios which can account for the PAMELA results and find that the decaying dark matter is preferred. Finally, we consider a decaying neutralino dark matter model in the frame of supersymmetry with R-parity violation. The PAMELA data is well fitted with a neutralino mass of 600 similar to 2000 GeV and a lifetime of similar to 10(26) seconds. We also demonstrate that a neutralino with mass around 2 TeV can fit PAMELA and ATIC data simultaneously.
118365937
Three-body force effect on nucleon momentum distributions in asymmetric nuclear matter within the framework of the extended Brueckner-Hartree-Fock approach
We have investigated the three-body force (TBF) effect on the neutron and proton momentum distributions in asymmetric nuclear matter within the framework of the extended Brueckner-Hartree-Fock approach by adopting the $AV18$ two-body interaction plus a microscopic TBF. In asymmetric nuclear matter, it is shown that the neutron and proton momentum distributions become different from their common distribution in symmetric nuclear matter. The predicted depletion of the proton hole states increases while the neutron one decreases as a function of isospin asymmetry. The TBF effect on the neutron and proton momentum distributions turns out to be negligibly weak at low densities around and below the normal nuclear density. The TBF effect is found to become sizable only at high densities well above the saturation density, and inclusion of the TBF leads to an overall enhancement of the depletion of the neutron and proton Fermi seas.
119110371
Three-body force effect on off-shell mass operator and spectral functions in nuclear matter
Within the framework of the Brueckner theory, the off-shell behaviors of the mass operator $M(k,\omega)=V(k,\omega)+iW(k,\omega)$, i.e., its dependence upon the momentum $k$ and upon the nucleon frequency $\omega$, are investigated by including nuclear three-body force (TBF). The first two terms of the hole-line expansion of the mass operator are taken into account. The TBF effects on their off-shell properties are discussed. A comparison is made between the on-shell and off-shell values of $M_{1}$. The nucleon spectral function and nucleon momentum distribution are also calculated, and the calculation shows that they are hardly affected by the TBF effect at the saturation density. At a high density two times greater than the saturation density, inclusion of the TBF may lead to a visible effect on the spectral function and may enhance the depletion of the hole states.