We revisit neutrino oscillations in matter considering the open quantum system framework, which allows to introduce possible decoherence effects generated by New Physics in a phenomenological manner. ...We assume that the decoherence parameters
γ
ij
may depend on the neutrino energy, as
γ
ij
=
γ
ij
0
(
E
/
GeV
)
n
(
n
=
0
,
±
1
,
±
2
)
. The case of non-uniform matter is studied in detail and, in particular, we develop a consistent formalism to study the non-adiabatic case dividing the matter profile into an arbitrary number of layers of constant densities. This formalism is then applied to explore the sensitivity of IceCube and DeepCore to this type of effects. Our study is the first atmospheric neutrino analysis where a consistent treatment of the matter effects in the three-neutrino case is performed in presence of decoherence. We show that matter effects are indeed extremely relevant in this context. We find that IceCube is able to considerably improve over current bounds in the solar sector (
γ
21
) and in the atmospheric sector (
γ
31
and
γ
32
) for
n
=
0
,
1
,
2
and, in particular, by several orders of magnitude (between 3 and 9) for the
n
=
1
,
2
cases. For
n
=
0
we find
γ
32
,
γ
31
<
4.0
×
10
-
24
(
1.3
×
10
-
24
)
GeV
and
γ
21
<
1.3
×
10
-
24
(
4.1
×
10
-
24
)
GeV
at the 95% CL, for normal (inverted) mass ordering.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A
bstract
We perform a detailed analysis of the one-loop corrections to the light neutrino mass matrix within low scale type I seesaw extensions of the Standard Model and their implications in ...experimental searches for neutrinoless double beta decay. We show that a sizable contribution to the effective Majorana neutrino mass from the exchange of heavy Majorana neutrinos is always possible, provided one requires a fine-tuned cancellation between the tree-level and one-loop contribution to the light neutrino masses. We quantify the level of fine-tuning as a function of the seesaw parameters and introduce a generalisation of the Casas-Ibarra parametrization of the neutrino Yukawa matrix, which easily allows to include the one-loop corrections to the light neutrino masses.
We study whether a dominant contribution to neutrinoless double beta decay coming from extra heavy degrees of freedom, introduced to generate the light neutrino masses, can dominate over the light ...neutrino contribution. It has been shown that this may occur at tree level if the light neutrino contribution partially cancels out. Here we focus on this case, specifically in the context of type-I seesaw models, paying special attention to the one-loop corrections to light neutrino masses, their contribution to the process and correlation with the heavy sector. We perform a general analysis without restricting the study to any particular region of the parameter space, although interesting limits associated with inverse and extended seesawlike models are discussed in more detail. It turns out that the heavy neutrinos can dominate the process only in those limits. For the inverse seesaw limit, we find a very constrained allowed region of the parameter space, with heavy neutrino masses around 5 GeV. The extended seesaw case allows for a larger region, but in general, a hierarchical spectrum of heavy neutrinos with masses above and below ~ 100 MeV is required.
Looking at the axionic dark sector with ANITA Esteban, I.; Lopez-Pavon, J.; Martinez-Soler, I. ...
The European physical journal. C, Particles and fields,
03/2020, Letnik:
80, Številka:
3
Journal Article
Recenzirano
Odprti dostop
The ANITA experiment has recently observed two anomalous events emerging from well below the horizon. Even though they are consistent with tau cascades, a high-energy Standard Model or Beyond the ...Standard Model explanation is challenging and in tension with other experiments. We study under which conditions the reflection of generic radio pulses can reproduce these signals. Furthermore, we propose that these pulses can be resonantly produced in the ionosphere via axion–photon conversion. This naturally explains the direction and polarization of the events and avoids other experimental bounds.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We evaluate the contribution to N sub(eff) of the extra sterile states in low-scale type I seesaw models (with three extra sterile states). We explore the full parameter space and find that at least ...two of the heavy states always reach thermalization in the early Universe, while the third one might not thermalize provided the lightest neutrino mass is below scriptO(10 super(-3) eV). Constraints from cosmology therefore severely restrict the spectra of heavy states in the range 1 eV-100 MeV. The implications for neutrinoless double beta decay are also discussed.
We analyze the general phenomenology of neutrinoless double beta decay in the minimal left–right symmetric model. We study under which conditions a New Physics dominated neutrinoless double beta ...decay signal can be expected in the future experiments. We show that the correlation among the different contributions to the process, which arises from the neutrino mass generation mechanism, can play a crucial role. We have found that, if no fine tuned cancelation is involved in the light–active neutrino contribution, a New Physics signal can be expected mainly from the
W
R
–
W
R
channel. An interesting exception is the
W
L
–
W
R
channel which can give a dominant contribution to the process if the right-handed neutrino spectrum is hierarchical with
M
1
≲
MeV and
M
2
,
M
3
≳
GeV. We also discuss if a New Physics signal in neutrinoless double beta decay experiments is compatible with the existence of a successful Dark Matter candidate in the left–right symmetric models. It turns out that, although it is not a generic feature of the theory, it is still possible to accommodate such a signal with a KeV sterile neutrino as dark matter.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A
bstract
A Standard Model extension with two Majorana neutrinos can explain the measured neutrino masses and mixings, and also account for the matter-antimatter asymmetry in a region of parameter ...space that could be testable in future experiments. The testability of the model relies to some extent on its minimality. In this paper we address the possibility that the model might be extended by extra generic new physics which we parametrize in terms of a low-energy effective theory. We consider the effects of the operators of the lowest dimensionality,
d
= 5, and evaluate the upper bounds on the coefficients so that the predictions of the minimal model are robust. One of the operators gives a new production mechanism for the heavy neutrinos at LHC via higgs decays. The higgs can decay to a pair of such neutrinos that, being long-lived, leave a powerful signal of two displaced vertices. We estimate the LHC reach to this process.
The amyloid cascade hypothesis is widely accepted as an explanation for the neuropathological changes in Alzheimer's disease (AD). However, the role of amyloid-beta (Aβ) as the sole cause of these ...changes is being questioned. Using the 5xFAD mouse model of AD, we investigated various factors contributing to neuropathology, including genetic load (heterozygous (HTZ) versus homozygous (HZ) condition), behavioural phenotype, neuropathology markers, metabolic physiology, and gut microbiota composition at early (5 months of age) and late (12 months of age) stages of disease onset, and considering both sexes. At 5 months of age, both HTZ and HZ mice exhibited hippocampal alterations associated with Aβ accumulation, leading to increased neuroinflammation and disrupted PI3K-Akt pathway. However, only HZ mice showed cognitive impairment in the Y-maze and Morris water maze tests, worsening with age. Dysregulation of both insulin and insulin secretion-regulating GIP peptide were observed at 5 months of age, disappearing later. Circulating levels of metabolic-regulating hormones, such as Ghrelin and resisting helped to differentiates HTZ mice from HZ mice. Differences between HTZ and HZ mice were also observed in gut microbiota composition, disrupted intestinal barrier proteins, and increased proinflammatory products in the intestine. These findings suggest that cognitive impairment in 5xFAD mice may not solely result from Aβ aggregation. Other factors, including altered PI3K-Akt signalling, disrupted insulin-linked metabolic pathways, and changes in gut microbiota, contribute to disease progression. Targeting Aβ deposition alone may not suffice. Understanding AD pathogenesis and its multiple contributing factors is vital for effective therapies.
Display omitted
•Gene dosage in the 5xFAD model worsens cognitive and hippocampal functions.•Cognitive impairment may not be due solely attributed to β-amyloid aggregation.•Premature alterations in insulin-linked metabolic pathways observed at 5-month-old 5xFAD homozygous mice.•Alteration of gut microbiota in the 5xFAD model associated with aging.•Disruption of the small intestinal epithelial layer in adult 5xFAD homozygous mice.
The seesaw path to leptonic CP violation Caputo, A.; Hernandez, P.; Kekic, M. ...
The European physical journal. C, Particles and fields,
04/2017, Letnik:
77, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Future experiments such as SHiP and high-intensity
e
+
e
-
colliders will have a superb sensitivity to heavy Majorana neutrinos with masses below
M
Z
. We show that the measurement of the mixing to ...electrons and muons of one such state could establish the existence of CP violating phases in the neutrino mixing matrix, in the context of low-scale seesaw models. We quantify in the minimal model the CP reach of these future experiments, and demonstrate that CP violating phases in the mixing matrix could be established at 5
σ
CL in a very significant fraction of parameter space.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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