| 1. |
- Bakhti, Pouya, et al.
(författare)
-
Revisiting the quantum decoherence scenario as an explanation for the LSND anomaly
- 2015
-
Ingår i: Journal of High Energy Physics (JHEP). - 1126-6708 .- 1029-8479. ; :5
-
Tidskriftsartikel (refereegranskat)abstract
- We propose an explanation for the LSND anomaly based on quantum decoherence, postulating an exponential behavior for the decoherence parameters as a function of the neutrino energy. Within this ansatz decoherence effects are suppressed for neutrino energies above 200 MeV as well as around and below few MeV, restricting deviations from standard three-flavour oscillations only to the LSND energy range of 20-50 MeV. The scenario is consistent with the global data on neutrino oscillations, alleviates the tension between LSND and KARMEN, and predicts a null-result for MiniBooNE. No sterile neutrinos are introduced, conflict with cosmology is avoided, and no tension between short-baseline appearance and disappearance data arises. The proposal can be tested at planned reactor experiments with baselines of around 50 km, such as JUNO or RENO-50.
|
|
| 2. |
- Bergström, Johannes, et al.
(författare)
-
Bayesian global analysis of neutrino oscillation data
- 2015
-
Ingår i: Journal of High Energy Physics (JHEP). - 1126-6708 .- 1029-8479. ; :9, s. 1-25
-
Tidskriftsartikel (refereegranskat)abstract
- We perform a Bayesian analysis of current neutrino oscillation data. When estimating the oscillation parameters we find that the results generally agree with those of the chi (2) method, with some differences involving s (23) (2) and CP-violating effects. We discuss the additional subtleties caused by the circular nature of the CP-violating phase, and how it is possible to obtain correlation coefficients with s (23) (2) . When performing model comparison, we find that there is no significant evidence for any mass ordering, any octant of s (23) (2) or a deviation from maximal mixing, nor the presence of CP-violation.
|
|
| 3. |
- Blennow, Mattias, et al.
(författare)
-
A halo-independent lower bound on the dark matter capture rate in the Sun from a direct detection signal
- 2015
-
Ingår i: Journal of Cosmology and Astroparticle Physics. - : Institute of Physics Publishing (IOPP). - 1475-7516. ; :05
-
Tidskriftsartikel (refereegranskat)abstract
- We show that a positive signal in a dark matter (DM) direct detection experiment can be used to place a lower bound on the DM capture rate in the Sun, independent of the DM halo. For a given particle physics model and DM mass we obtain a lower bound on the capture rate independent of the local DM density, velocity distribution, galactic escape velocity, as well as the scattering cross section. We illustrate this lower bound on the capture rate by assuming that upcoming direct detection experiments will soon obtain a significant signal. When comparing the lower bound on the capture rate with limits on the high-energy neutrino flux from the Sun from neutrino telescopes, we can place upper limits on the branching fraction of DM annihilation channels leading to neutrinos. With current data from IceCube and Super-Kamiokande non-trivial limits can be obtained for spin-dependent interactions and direct annihilations into neutrinos. In some cases also annihilations into tau tau or bb start getting constrained. For spin-independent interactions current constraints are weak, but they may become interesting for data from future neutrino telescopes.
|
|
| 4. |
- Blennow, Mattias, et al.
(författare)
-
Halo-independent tests of dark matter direct detection signals : Local DM density, LHC, and thermal freeze-out
- 2015
-
Ingår i: Journal of Cosmology and Astroparticle Physics. - : IOP Publishing. - 1475-7516. ; 2015:8
-
Tidskriftsartikel (refereegranskat)abstract
- From an assumed signal in a Dark Matter (DM) direct detection experiment a lower bound on the product of the DM-nucleon scattering cross section and the local DM density is derived, which is independent of the local DM velocity distribution. This can be combined with astrophysical determinations of the local DM density. Within a given particle physics model the bound also allows a robust comparison of a direct detection signal with limits from the LHC. Furthermore, the bound can be used to formulate a condition which has to be fulfilled if the particle responsible for the direct detection signal is a thermal relic, regardless of whether it constitutes all DM or only part of it. We illustrate the arguments by adopting a simplified DM model with a Z' mediator and assuming a signal in a future xenon direct detection experiment.
|
|
| 5. |
- Elevant, Jessica, et al.
(författare)
-
On the determination of the leptonic CP phase
- 2015
-
Ingår i: Journal of High Energy Physics (JHEP). - 1126-6708 .- 1029-8479. ; :9
-
Tidskriftsartikel (refereegranskat)abstract
- The combination of data from long-baseline and reactor oscillation experiments leads to a preference of the leptonic CP phase delta(CP) in the range between pi and 2 pi. We study the statistical significance of this hint by performing a Monte Carlo simulation of the relevant data. We find that the distribution of the standard test statistic used to derive confidence intervals for delta(CP) is highly non-Gaussian and depends on the unknown true values of theta(23) and the neutrino mass ordering. Values of delta(CP) around pi/2 are disfavored at between 2 sigma and 3 sigma, depending on the unknown true values of theta(23) and the mass ordering. Typically the standard chi(2) approximation leads to over-coverage of the confidence intervals for delta(CP). For the 2-dimensional confidence region in the (delta(CP), theta(23)) plane the usual chi(2) approximation is better justified. The 2-dimensional region does not include the value delta(CP) = pi/2 up to the 86.3% (89.2%) CL assuming a true normal (inverted) mass ordering. Furthermore, we study the sensitivity to delta(CP) and theta(23) of an increased exposure of the T2K experiment, roughly a factor 12 larger than the current exposure and including also anti-neutrino data. Also in this case deviations from Gaussianity may be significant, especially if the mass ordering is unknown.
|
|
| 6. |
- Kahlhoefer, Felix, et al.
(författare)
-
Implications of unitarity and gauge invariance for simplified dark matter models
- 2016
-
Ingår i: Journal of High Energy Physics (JHEP). - 1126-6708 .- 1029-8479. ; :2
-
Tidskriftsartikel (refereegranskat)abstract
- We show that simplified models used to describe the interactions of dark matter with Standard Model particles do not in general respect gauge invariance and that perturbative unitarity may be violated in large regions of the parameter space. The modifications necessary to cure these inconsistencies may imply a much richer phenomenology and lead to stringent constraints on the model. We illustrate these observations by considering the simplified model of a fermionic dark matter particle and a vector mediator. Imposing gauge invariance then leads to strong constraints from dilepton resonance searches and electroweak precision tests. Furthermore, the new states required to restore perturbative unitarity can mix with Standard Model states and mediate interactions between the dark and the visible sector, leading to new experimental signatures such as invisible Higgs decays. The resulting constraints are typically stronger than the 'classic' constraints on DM simplified models such as monojet searches and make it difficult to avoid thermal overproduction of dark matter.
|
|
