Phenomenology Of Sterile Neutrinos At Different Mass Scales: Neutrinoless Double Beta Decay And Neutrino Oscillations

The existence of neutrino oscillation is the first evidence of physics beyond the Standard Model. It proves that neutrinos are massive and motivates the study of the neutrino nature, mixings and mass generation models. To have a better understanding of neutrino masses and mixings, the existence and character of sterile neutrinos would be an important factor. In this thesis, we will describe the phenomena of neutrinoless double beta decay and sterile neutrino oscillations. The studies of these two topics will contribute to understanding the properties of sterile neutrinos in the heavy and light mass regime. We first study the neutrinoless double beta decay process to tackle the issue about the nature of neutrino. Establishing the nature of neutrinos, whether they are Dirac or Majorana particles is one of the fundamental questions we need to answer in particle physics, and is related to the conservation of lepton number. Neutrinoless double beta decay is the tool of choice for testing the Majorana nature of neutrinos. However, up to now, this process has not been observed, but a wide experimental effort is taking place worldwide and soon new results will become available. Different mechanisms can induce neutrinoless double beta decay and might interfere with each other, potentially leading to suppressed contributions to the decay rate. This possibility would become of great interest if upcoming neutrino mass measurements from KATRIN and cosmological observations found that neutrino mass is larger than 0.2 eV but no positive signal was observed in neutrinoless double beta decay experiments. We focus on the possible interference between light Majorana neutrino exchange with other mechanisms, such as heavy sterile neutrinos and R-parity violating supersymmetric models. We show that in some cases the use of different nuclei would allow to disentangle the different contributions and allow to test the hypothesis of destructive interference. Finally, we present a model in which such interference can emerge and we discuss the range of parameters which would lead to a significant suppression of the decay rate. Heavy sterile neutrino is involved in the studies of neutrinoless double beta decay and mass generation involve. On the other hand, the effect of light sterile neutrino may be present in the oscillation experiments. To measure the light sterile neutrino mixing, high statistics measurements are necessary. A neutrino factory has been suggested as a powerful tool for studying new physics, for example, sterile neutrinos, exploiting its near detectors. Here, we use the new version of GLoBES to study the potential of a low energy neutrino factory (LENF) in constraining the sterile mixing angles and the mass-square difference. Unlike in conventional long baseline neutrino experiments, the electron neutrino disappearance and appearance channels are also included, since they have been proved helpful in constraining some of the mixing angles. We will explore the dependence of the performance of the LENF depending on different experimental setups, such as the detector type (TASD and LiAr), the energy range, the systematic errors. etc. Moreover, the re-analysis of reactor neutrino experiments suggests the presence of neutrino oscillations due to large sterile neutrino mixing with electron neutrino. We show that, with a near detector, LENF can constrain the sterile parameter values in a very small range and helps us to check the recent Reactor Anomaly

Wave-packet treatment of neutrino oscillations and its implications on determining the neutrino mass hierarchy

We derive the neutrino flavor transition probabilities with the neutrino treated as a wave packet. The decoherence and dispersion effects from the wave-packet treatment show up as damping and phase-shifting of the plane-wave neutrino oscillation patterns. If the energy uncertainty in the initial neutrino wave packet is larger than around 0.01 of the neutrino energy, the decoherence and dispersion effects would degrade the sensitivity of reactor neutrino experiments to mass hierarchy measurement to lower than 3 $\sigma$ confidence level

Fluid Antenna System—Part II: Research Opportunities

The promising performance of fluid antenna systems (FAS) relies on activating the optimal port to access the spatial opportunity for favourable channel conditions for wireless communications. This nevertheless can imply enormous overheads in channel estimation and signal reception as the resolution of fluid antenna could be arbitrarily high. There is also the challenge of optimizing jointly the selected ports and beamforming when FAS combines with multiple-input multiple-output (MIMO) systems. This letter discusses some of these obstacles in FAS. Moreover, we present several research opportunities that, if addressed properly, FAS could synergize with other enabling mobile technologies for meeting the requirements of the sixth generation (6G)

Compact Ultra Massive Antenna Array: A Simple Open-Loop Massive Connectivity Scheme

This paper aims to present a simple multiple access scheme for massive connectivity that enables a large number of mobile user equipments (UEs) to occupy the same time-frequency channel without the need of precoding and power control at the base station (BS) and interference cancellation at each UE. The proposed approach does not even require the UEs to know their signal-to-interference ratios (SIRs) and each UE also needs only two radio-frequency (RF) chains to operate. The proposed scheme is inspired by the emerging concept of fluid antenna system (FAS) which enables high-resolution position-switchable antenna to be deployed at each UE. Instead of activating only one port of FAS for reception, each UE activates an ultra massive number of ports to receive the signal. The activated ports are chosen to ensure that the in-phase and quadrature components of the desired signal at the ports are added constructively while the interference signals superimpose randomly. This approach is referred to as compact ultra massive antenna array (CUMA) which can also be realized by deploying a dense, fixed massive antenna array at each UE. We derive the exact probability density function (pdf) of the SIR of a CUMA UE which leads to the data rate analysis. Simulation results demonstrate that even with mutual coupling and under finite scattering, more than 10 UEs can be supported by having a 25×13-port FAS of size 15 cm×8 cm at each UE. Considering quadrature phase shift keying (QPSK), CUMA delivers a network data rate of 10.7 bps per channel use serving 10 UEs at 26 GHz, and the rate is risen to 15.1 bps per channel use if 20 UEs are accommodated at 40 GHz with a 40×21-port FAS at every UE. In the case without mutual coupling and under rich scattering, CUMA can even support hundreds of UEs per channel use

Fluid Antenna System—Part III: A New Paradigm of Distributed Artificial Scattering Surfaces for Massive Connectivity

Reconfigurable intelligent surface (RIS) has recently emerged as a promising technology to extend the coverage of a base station (BS) in wireless communication networks. However, the adoption of RIS comes with the challenges of highly complex joint optimization of the multiple-input multiple-output (MIMO) precoding matrix at the BS and the phase shifters of the RIS as well as estimation of the cascaded channels. To circumvent this, this letter presents a new paradigm that uses RISs as distributed artificial scattering surfaces (DASSs) to produce a rich scattering environment that enables fluid antenna system (FAS) to prevent multiuser interference at each user equipment (UE). The use of fluid antenna multiple access (FAMA) liberates MIMO and RIS and greatly simplifies their optimization. Our simulation results show that with DASS, slow FAMA can obtain a high multiplexing gain without precoding and phase shifter design when the direct link does not exist. In the presence of the direct link, nonetheless, BS precoding becomes essential. Our results further reveal that fast FAMA with 20 DASSs can accommodate 64 co-channel UEs to achieve a multiplexing gain of 59.3 without precoding at the BS nor RIS phase shifter optimization and the direct link

Application of tri-colour, dual fusion fluorescence in situ hybridization (FISH) system for the characterization of BCR-ABL1 fusion in chronic myelogenous leukaemia (CML) and residual disease monitoring

<p>Abstract</p> <p>Background</p> <p>We studied the application of the <it>BCR-ABL1 </it>+ 9q34 tri-colour dual fusion fluorescence <it>in situ </it>hybridization (FISH) system in the characterization of fusion signal pattern and the monitoring of residual disease in chronic myelogenous leukaemia (CML). The signal constellation on metaphases with the tri-colour dual fusion system was defined. The knowledge of various signal patterns obtained from the different genetic rearrangements was further applied to the analysis of hybridization signals on interphase nuclei.</p> <p>Methods</p> <p><it>BCR-ABL1 </it>dual colour, dual fusion FISH (D-FISH) was performed on diagnostic samples of 22 CML patients. The tri-colour FISH system was performed on cases that showed aberrant signal patterns other than the classical 1 green (G) 1 orange (O) 2 fusions (F). Using the aqua band-pass filter, random signal overlap in interphase nuclei would be indicated by the presence of an aqua signal (<it>ASS1</it>), while genuine fusion was represented by the absence of the <it>ASS1 </it>signal.</p> <p>Results</p> <p>Using the D-FISH system, the signal patterns could be categorized into 4 groups: group 1 (n = 17) showed the classical 1G1O2F; group 2 (n = 2) showed 2G1O1F indicating <it>ABL1 </it>deletion; group 3 (n = 1) showed 1G2O1F indicating <it>BCR </it>deletion; group 4 (n = 2) with 1G1O1F indicating reciprocal <it>ABL1-BCR </it>deletion. The tri-colour dual fusion system correlated with the D-FISH system for cases with der(9) deletion. The added aqua-labelled <it>ASS1 </it>probe was useful in differentiating random signal overlap from genuine <it>BCR-ABL1 </it>fusion in the interphase cells (group 4).</p> <p>Conclusion</p> <p>Although the D-FISH probe was valuable in establishing the different patterns of aberrant signals and monitoring patients with the classic 2-fusion signals in CML, the tri-colour dual fusion probe should be used for patients with der(9) deletion to monitor response to treatment.</p