776 research outputs found

    Quasi-Degenerate Neutrinos in Type II Seesaw Models

    Full text link
    We present an analysis of normal and inverted hierarchical neutrino mass models within the framework of tri-bi-maximal (TBM) mixing. Considering the neutrinos to be quasi-degenerate (QDN), we study two different neutrino mass models with mass eigenvalues (m1,−m2,m3)(m_1, -m_2, m_3) and (m1,m2,m3)(m_1, m_2, m_3) for both normal hierarchical (NH) and inverted hierarchical (IH) cases. Parameterizing the neutrino mass matrix using best fit oscillation and cosmology data for a QDN scenario, we find the right-handed Majorana mass matrix using type I seesaw formula for two types of Dirac neutrino mass matrices: charged lepton (CL) type and up quark (UQ) type. Incorporating the presence of type II seesaw term which arises naturally in generic left-right symmetric models (LRSM) along with type I term, we compare the predictions for neutrino mass parameters with the experimental values. Within such a framework and incorporating both oscillation as well as cosmology data, we show that QDN scenario of neutrino masses can still survive in nature with some minor exceptions. A viable extension of the standard model with an abelian gauged flavor symmetry is briefly discussed which can give rise to the desired structure of the Dirac and Majorana mass matrices.Comment: Version 2: Typos corrected, texts+tables rearranged, conclusion unchanged. Accepted for publication in Physical Review

    Reactor mixing angle from hybrid neutrino masses

    Get PDF
    In terms of its eigenvector decomposition, the neutrino mass matrix (in the basis where the charged lepton mass matrix is diagonal) can be understood as originating from a tribimaximal dominant structure with small deviations, as demanded by data. If neutrino masses originate from at least two different mechanisms, referred to as "hybrid neutrino masses", the experimentally observed structure naturally emerges provided one mechanism accounts for the dominant tribimaximal structure while the other is responsible for the deviations. We demonstrate the feasibility of this picture in a fairly model-independent way by using lepton-number-violating effective operators, whose structure we assume becomes dictated by an underlying A4A_4 flavor symmetry. We show that if a second mechanism is at work, the requirement of generating a reactor angle within its experimental range always fixes the solar and atmospheric angles in agreement with data, in contrast to the case where the deviations are induced by next-to-leading order effective operators. We prove this idea is viable by constructing an A4A_4-based ultraviolet completion, where the dominant tribimaximal structure arises from the type-I seesaw while the subleading contribution is determined by either type-II or type-III seesaw driven by a non-trivial A4A_4 singlet (minimal hybrid model). After finding general criteria, we identify all the ZN\mathbb{Z}_N symmetries capable of producing such A4A_4-based minimal hybrid models.Comment: 18 pages, 5 figures. v3: section including sum rules added, accepted by JHE

    Lowering solar mixing angle in inverted hierarchy without charged lepton corrections

    Full text link
    In the present work, the inverted hierarchical neutrino mass model which is characterised by opposite CP parity in the first two mass eigenvalues (m1,−m2,m3)(m_1,-m_2,m_3), is studied in order to lower the predicted value of solar mixing angle tan⁡2ξ12\tan^2\theta_{12}, from the tri-bimaximal mixing (TBM), without sacrificing the conditions of maximal atmospheric mixing angle and zero reactor angle. The present attempt is different from the earlier approach where the correction from the charged lepton mass matrix is included in the leptonic mixing matrix to lower the prediction on solar mixing angle. The lowering of the solar mixing angle without charged lepton correction, can be obtained through the variation of the input value of a flavour twister term present in the texture of neutrino mass matrix having a 2-3 symmetry. The present analysis agrees with the latest experimental bounds on neutrino mass parameters and also represents an important result on the survival of the inverted hierarchical neutrino mass models having opposite CP parity in the first two eigenvalues.Comment: 10 pages, two figures. Accepted for publication in Journal of Physics G:Nuclear and Particle Physic

    Deviation from tri-bimaximal mixings in two types of inverted hierarchical neutrino mass models

    Full text link
    An attempt is made to explore the possibility for deviations of solar mixing angle (Ξ12\theta_{12}) from tri-bimaximal mixings, without sacrificing the predictions of maximal atmospheric mixing angle (Ξ23=π/4\theta_{23}=\pi/4) and zero reactor angle (Ξ13=0\theta_{13}=0). We find that the above conjecture can be automatically realised in the inverted hierarchical neutrino mass model having 2-3 symmetry, in the basis where charged lepton mass matrix is diagonal. For the observed ranges of △m212\bigtriangleup m^2_{21} and \bigtriangleup m^2_{23], we calculate the predictions on tan⁥2Ξ12=0.5,0.45,0.35\tan^2\theta_{12}=0.5, 0.45, 0.35 for different input values of the parameters in the neutrino mass matrix. We also observe a possible crossing over from one type of inverted hierarchical model having same CP parity (Type-IHA) to other type having opposite CP parity (Type-IHB). Such neutrino mass matrices can be obtained from the canonical seesaw formula using diagonal form of Dirac neutrino mass matrix and non-diagonal texture of right-handed Majorana mass matrix, and may have important implications in model building using discrete as well as non-abelian symmetry groups.Comment: 13 pages, 7 figure

    Empowerment or Engagement? Digital Health Technologies for Mental Healthcare

    Get PDF
    We argue that while digital health technologies (e.g. artificial intelligence, smartphones, and virtual reality) present significant opportunities for improving the delivery of healthcare, key concepts that are used to evaluate and understand their impact can obscure significant ethical issues related to patient engagement and experience. Specifically, we focus on the concept of empowerment and ask whether it is adequate for addressing some significant ethical concerns that relate to digital health technologies for mental healthcare. We frame these concerns using five key ethical principles for AI ethics (i.e. autonomy, beneficence, non-maleficence, justice, and explicability), which have their roots in the bioethical literature, in order to critically evaluate the role that digital health technologies will have in the future of digital healthcare

    Comparison of the clinical and economic outcomes between open and minimally invasive appendectomy and colectomy: evidence from a large commercial payer database

    Get PDF
    Background: Appendectomy and colectomy are commonly performed surgical procedures. Despite evidence demonstrating advantages with the minimally invasive surgical (MIS) approach, open procedures occur with greater prevalence. Therefore, there is still controversy as to whether the MIS approach is safer or more cost effective. Methods: A retrospective analysis was performed using a large commercial payer database. The data included information on 7,532 appendectomies and 2,745 colectomies. Data on the distribution of patient demographic and comorbidity characteristics associated with the MIS and open approaches were reviewed. The corresponding complication rates and expenditures were analyzed. Summary statistics were compared using chi-square tests, and generalized linear models were constructed to estimate expenditures while controlling for patient characteristics. Results: The patients undergoing MIS and open colectomy showed no significant variations in age distribution or marginal age differences for appendectomy. Significantly more patients experienced an infection postoperatively, and procedure-specific complications were more common in the open group for both procedures (P < 0.05). The postsurgical hospital stay was longer for the patients treated using the open techniques, differing an average of half a day for appendectomies and significantly more (4 days) for colectomy (P < 0.05). Readmission rates differed little between the two approaches. Procedures performed through an MIS approach were associated with lower expenditures than for the open technique, with differences ranging from 700forappendectomypatients(P < 0.05)to700 for appendectomy patients (P < 0.05) to 15,200 for colectomy patients (P < 0.05). Conclusions: Minimally invasive appendectomy and colectomy were associated with lower infection rates, fewer complications, shorter hospital stays, and lower expenditures than open surgery

    A Dip Into a Deep Well: Online Political Advertisements, Valence, and European Electoral Campaigning

    Full text link
    Online political advertisements have become an important element in electoral campaigning throughout the world. At the same time, concepts such as disinformation and manipulation have emerged as a global concern. Although these concepts are distinct from online political ads and data-driven electoral campaigning, they tend to share a similar trait related to valence, the intrinsic attractiveness or averseness of a message. Given this background, the paper examines online political ads by using a dataset collected from Google's transparency reports. The examination is framed to the mid-2019 situation in Europe, including the European Parliament elections in particular. According to the results based on sentiment analysis of the textual ads displayed via Google's advertisement machinery, (i) most of the political ads have expressed positive sentiments, although these vary greatly between (ii) European countries as well as across (iii) European political parties. In addition to these results, the paper contributes to the timely discussion about data-driven electoral campaigning and its relation to politics and democracy

    Maximising the availability and use of high quality evidence for policymaking:Collaborative, targeted and efficient evidence reviews

    Get PDF
    Abstract A number of barriers have been identified to getting evidence into policy. In particular, a lack of policy relevance and lack of timeliness have been identified as causing tension between researchers and policy makers. Rapid reviews are used increasingly as an approach to address timeliness, however, there is a lack of consensus on the most effective review methods and they do not necessarily address the need of policy makers. In the course of our work with the Scottish Government’s Review of maternity and neonatal services we developed a new approach to evidence synthesis, which this paper will describe. We developed a standardised approach to produce collaborative, targeted and efficient evidence reviews for policy making. This approach aimed to ensure the reviews were policy relevant, high quality and up-to-date, and which were presented in a consistent, transparent, and easy to access format. The approach involved the following stages: 1) establishing a review team with expertise both in the topic and in systematic reviewing, 2) clarifying the review questions with policy makers and subject experts (i.e., health professionals, service user representatives, researchers) who acted as review sponsors, 3) developing review protocols to systematically identify quantitative and qualitative review-level evidence on effectiveness, sustainability and acceptability; if review level evidence was not available, primary studies were sought, 4) agreeing a framework to structure the analysis of the reviews around a consistent set of key concepts and outcomes; in this case a published framework for maternal and newborn care was used, 5) developing an iterative process between policy makers, reviewers and review sponsors, 6) rapid searches and retrieval of literature, 7) analysis of identified literature which was mapped to the framework and included review sponsor input, 8) production of recommendations mapped to the agreed framework and presented as ‘summary topsheets’ in a consistent and easy to read format. Our approach has drawn on different components of pre-existing rapid review methodology to provide a rigorous and pragmatic approach to rapid evidence synthesis. Additionally, the use of a framework to map the evidence helped structure the review questions, expedited the analysis and provided a consistent template for recommendations, which took into account the policy context. We therefore propose that our approach (described in this paper) can be described as producing collaborative, targeted and efficient evidence reviews for policy makers

    The Higgs vacuum uplifted: revisiting the electroweak phase transition with a second Higgs doublet

    Get PDF
    The existence of a second Higgs doublet in Nature could lead to a cosmological first order electroweak phase transition and explain the origin of the matter-antimatter asymmetry in the Universe. We explore the parameter space of such a two-Higgs-doublet-model and show that a first order electroweak phase transition strongly correlates with a significant uplifting of the Higgs vacuum w.r.t. its Standard Model value. We then obtain the spectrum and properties of the new scalars H0, A0 and H± that signal such a phase transition, showing that the decay A0 → H0Z at the LHC and a sizable deviation in the Higgs self-coupling λhhh from its SM value are sensitive indicators of a strongly first order electroweak phase transition in the 2HDM
    • 

    corecore