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He Zhang

Publications and source records attributed to He Zhang.

At least 307 records · Page 17Linked to original sources

Nonstandard interaction effects on neutrino parameters at medium-baseline reactor antineutrino experiments

Precision measurements of leptonic mixing parameters and the determination of the neutrino mass hierarchy are the primary goals of the forthcoming medium-baseline reactor antineutrino experiments, such as JUNO and RENO-50. In this work, we investigate the impact of nonstandard neutrino interactions (NSIs) on the measurements of {sin^2 theta_{12}, Delta m^2_{21}} and {sin^2 theta_{13}, Delta m^2_{31}}, and on the sensitivity to the neutrino mass hierarchy, at the medium-baseline reactor experiments by assuming a typical experimental setup. It turns out that the true mixing parameter sin^2 theta_{12} can be excluded at a more than 3 sigma level if the NSI parameter varepsilon_{e mu} or varepsilon_{e tau} is as large as 2% in the most optimistic case. However, the discovery reach of NSI effects has been found to be small, and depends crucially on the CP-violating phases. Finally, we show that NSI effects could enhance or reduce the discrimination power of the JUNO and RENO-50 experiments between the normal and inverted neutrino mass hierarchies.

hep-ph↗

Signatures of Extra Dimensional Sterile Neutrinos

We study a large extra dimension model with active and sterile Dirac neutrinos. The sterile neutrino masses stem from compactification of an extra dimension with radius $R$ and are chosen to have masses around eV or keV, in order to explain short-baseline anomalies or act as warm dark matter candidates. We study the effect of the sterile neutrino Kaluza-Klein tower in short-baseline oscillation experiments and in the beta spectrum as measurable by KATRIN-like experiments.

hep-ph↗

Constraining Sterile Neutrinos Using Reactor Neutrino Experiments

Models of neutrino mixing involving one or more sterile neutrinos have resurrected their importance in the light of recent cosmological data. In this case, reactor antineutrino experiments offer an ideal place to look for signatures of sterile neutrinos due to their impact on neutrino flavor transitions. In this work, we show that the high-precision data of the Daya Bay experi\-ment constrain the 3+1 neutrino scenario imposing upper bounds on the relevant active-sterile mixing angle $\sin^2 2 θ_{14} \lesssim 0.06$ at 3$σ$ confidence level for the mass-squared difference $Δm^2_{41}$ in the range $(10^{-3},10^{-1}) \, {\rm eV^2}$. The latter bound can be improved by six years of running of the JUNO experiment, $\sin^22θ_{14} \lesssim 0.016$, although in the smaller mass range $ Δm^2_{41} \in (10^{-4} ,10^{-3}) \, {\rm eV}^2$. We have also investigated the impact of sterile neutrinos on precision measurements of the standard neutrino oscillation parameters $θ_{13}$ and $Δm^2_{31}$ (at Daya Bay and JUNO), $θ_{12}$ and $Δm^2_{21}$ (at JUNO), and most importantly, the neutrino mass hierarchy (at JUNO). We find that, except for the obvious situation where $Δm^2_{41}\sim Δm^2_{31}$, sterile states do not affect these measurements substantially.

hep-ph↗

Renormalization Group Running of the Neutrino Mass Operator in Extra Dimensions

We study the renormalization group (RG) running of the neutrino masses and the leptonic mixing parameters in two different extra-dimensional models, namely, the Universal Extra Dimensions (UED) model and a model, where the Standard Model (SM) bosons probe an extra dimension and the SM fermions are confined to a four-dimensional brane. In particular, we derive the beta function for the neutrino mass operator in the UED model. We also rederive the beta function for the charged-lepton Yukawa coupling, and confirm some of the existing results in the literature. The generic features of the RG running of the neutrino parameters within the two models are analyzed and, in particular, we observe a power-law behavior for the running. We note that the running of the leptonic mixing angle θ_{12} can be sizable, while the running of θ_{23} and θ_{13} is always negligible. In addition, we show that the tri-bimaximal and the bimaximal mixing patterns at a high-energy scale are compatible with low-energy experimental data, while a tri-small mixing pattern is not. Finally, we perform a numerical scan over the low-energy parameter space to infer the high-energy distribution of the parameters. Using this scan, we also demonstrate how the high-energy θ_{12} is correlated with the smallest neutrino mass and the Majorana phases.

hep-ph↗

Status of the Zee-Babu model for neutrino mass and possible tests at a like-sign linear collider

We provide an updated scan of the allowed parameter space of the two-loop Zee-Babu model for neutrino mass. Taking into account most recent experimental data on $μ\to eγ$ as well as the mixing angle $θ_{13}$ we obtain lower bounds on the masses of the singly and doubly charged scalars of between 1 to 2 TeV, with some dependence on perturbativity and fine-tuning requirements. This makes the scalars difficult to observe at LHC with 14 TeV even with optimistic assumptions on the luminosity, and would require a multi-TeV linear collider to see the scalar resonances. We point out, however, that a sub-TeV linear collider in the like-sign mode may be able to observe lepton flavour violating processes such as $e^- e^- \to μ^- μ^-$ due to contact interactions induced by the doubly charged scalar with masses up to around 10 TeV. We investigate the possibility to distinguish the Zee-Babu model from the Higgs triplet model using such processes.

hep-ph↗

Reducing θ_13 to 9 degrees

We propose to consider the possibility that the observed value of $θ_{13}$ is not the result of a correction from an initially vanishing value, but rather the result of a correction from an initially larger value. As an explicit example of this approach, we consider analytically and numerically well-known CKM-like charged lepton corrections to a neutrino diagonalization matrix that corresponds to a certain mixing scheme. Usually this results in generating $θ_{13} = 9^\circ$ from zero. We note here, however, that 9 is not only given by $0 + 9$, but also by $18 - 9$. Hence, the extreme case of an initial value of 18 degrees, reduced by charged lepton corrections to 9 degrees, is possible. For some cases under study new sum rules for the mixing parameters, and correlations with CP phases are found.

hep-ph↗

The Cloud's Cloudy Moment: A Systematic Survey of Public Cloud Service Outage

Inadequate service availability is the top concern when employing Cloud computing. It has been recognized that zero downtime is impossible for large-scale Internet services. By learning from the previous and others' mistakes, nevertheless, it is possible for Cloud vendors to minimize the risk of future downtime or at least keep the downtime short. To facilitate summarizing lessons for Cloud providers, we performed a systematic survey of public Cloud service outage events. This paper reports the result of this survey. In addition to a set of findings, our work generated a lessons framework by classifying the outage root causes. The framework can in turn be used to arrange outage lessons for reference by Cloud providers. By including potentially new root causes, this lessons framework will be smoothly expanded in our future work.

cs.DC↗

Effects of nonstandard neutrino interactions at PINGU

Neutrino oscillation experiments in the past decades have greatly improved our knowledge on neutrinos by measuring the fundamental neutrino parameters. The ongoing and upcoming neutrino oscillation experiments are intended to pin down the neutrino mass hierarchy and to discover the leptonic CP violation. By means of neutrino oscillograms, we analyze the impact of non-standard neutrino interactions on neutrino oscillations in the Earth matter. The standard neutrino oscillation probabilities may be significantly changed by non-standard interaction parameters, and in particular, the CP-violating effects in the energy range E = 1 ~ 20 GeV are greatly enhanced. In addition, the event rates of muon neutrinos in the proposed huge atmospheric neutrino experiment, PINGU at the South Pole, have been estimated in the presence of non-standard neutrino interactions. It has been found that the PINGU experiment has very good sensitivities to the non-standard neutrino interaction parameters.

hep-ph↗

Exotic Charges, Multicomponent Dark Matter and Light Sterile Neutrinos

Generating small sterile neutrino masses via the same seesaw mechanism that suppresses active neutrino masses requires a specific structure in the neutral fermion mass matrix. We present a model where this structure is enforced by a new U(1)' gauge symmetry, spontaneously broken at the TeV scale. In order not to spoil the neutrino structure, the additional fermions necessary for anomaly cancellations need to carry exotic charges, and turn out to form multicomponent cold dark matter. The active-sterile mixing then connects the new particles and the Standard Model---opening a new portal in addition to the usual Higgs- and kinetic-mixing portals---which leads to dark matter annihilation almost exclusively into neutrinos.

hep-ph↗

Meta-Analysis of Gene Level Association Tests

The vast majority of connections between complex disease and common genetic variants were identified through meta-analysis, a powerful approach that enables large samples sizes while protecting against common artifacts due to population structure, repeated small sample analyses, and/or limitations with sharing individual level data. As the focus of genetic association studies shifts to rare variants, genes and other functional units are becoming the unit of analysis. Here, we propose and evaluate new approaches for meta-analysis of rare variant association. We show that our approach retains useful features of single variant meta-analytic approaches and demonstrate its utility in a study of blood lipid levels in ~18,500 individuals genotyped with exome arrays.

stat.ME↗

A(4) Flavor Symmetry Model for Dirac-Neutrinos and Sizable U(e3)

Models based on flavor symmetries are the most often studied approaches to explain the unexpected structure of lepton mixing. In many flavor symmetry groups a product of two triplet representations contains a symmetric and an anti-symmetric term. If this product of two triplets corresponds to a Majorana mass term, then the anti-symmetric part vanishes, and in economic models tri-bimaximal mixing is achieved. If neutrinos are Dirac particles, the anti-symmetric part is however present and leads to deviations from tri-bimaximal mixing, in particular non-zero U(e3). Thus, the non-vanishing value of U(e3) and the nature of the neutrino are connected. We illustrate this with a model based on A(4) within the framework of a neutrinophilic 2 Higgs doublet scenario.

hep-ph↗

Probing the leptonic Dirac CP-violating phase in neutrino oscillation experiments

The discovery of leptonic CP violation is one of the primary goals of next-generation neutrino oscillation experiments, which is feasible due to the recent measurement of a relatively large leptonic mixing angle θ_{13}. We suggest two new working observables ΔA^{\rm m}_{αβ} \equiv \max[A^{\rm CP}_{αβ}(δ)] - \min[A^{\rm CP}_{αβ}(δ)] and ΔA^{\rm CP}_{αβ}(δ) \equiv A^{\rm CP}_{αβ}(δ) - A^{\rm CP}_{αβ}(0) to describe the CP-violating effects in long-baseline and atmospheric neutrino oscillation experiments. The former signifies the experimental sensitivity to the leptonic Dirac CP-violating phase $δ$ and can be used to optimize the experimental setup, while the latter measures the intrinsic leptonic CP violation and can be used to extract $δ$ directly from the experimental observations. Both analytical and numerical analyses are carried out to illustrate their main features. It turns out that an intense neutrino beam with sub-GeV energies and a baseline of a few 100 km may serve as an optimal experimental setup for probing leptonic CP violation.

hep-ph↗

Circumstantial-Evidence-Based Judgment for Software Effort Estimation

Expert judgment for software effort estimation is oriented toward direct evidences that refer to actual effort of similar projects or activities through experts' experiences. However, the availability of direct evidences implies the requirement of suitable experts together with past data. The circumstantial-evidence-based judgment proposed in this paper focuses on the development experiences deposited in human knowledge, and can then be used to qualitatively estimate implementation effort of different proposals of a new project by rational inference. To demonstrate the process of circumstantial-evidence-based judgment, this paper adopts propositional learning theory based diagnostic reasoning to infer and compare different effort estimates when implementing a Web service composition project with some different techniques and contexts. The exemplar shows our proposed work can help determine effort tradeoff before project implementation. Overall, circumstantial-evidence-based judgment is not an alternative but complementary to expert judgment so as to facilitate and improve software effort estimation.

cs.SE↗

Towards Technology Independent Strategies for SOA Implementations

Benefiting from the technology based strategies, Service-Oriented Architecture (SOA) has been able to achieve the general goals such as agility, flexibility, reusability and efficiency. Nevertheless, technical conditions alone cannot guarantee successful SOA implementations. As a valuable and necessary supplement, the space of technology independent strategies should also be explored. Through treating SOA system as an instance of organization and identifying the common ground on the similar process of SOA implementation and organization design, this paper uses existing work in organization theory area to inspire the research into technology independent strategies of SOA implementation. As a result, four preliminary strategies that can be applied to organizational area we identify to support SOA implementations. Furthermore, the novel methodology of investigating technology independent strategies for implementing SOA is revealed, which encourages interdisciplinary research across service-oriented computing and organization theory.

cs.SE↗

Building an Expert System for Evaluation of Commercial Cloud Services

Commercial Cloud services have been increasingly supplied to customers in industry. To facilitate customers' decision makings like cost-benefit analysis or Cloud provider selection, evaluation of those Cloud services are becoming more and more crucial. However, compared with evaluation of traditional computing systems, more challenges will inevitably appear when evaluating rapidly-changing and user-uncontrollable commercial Cloud services. This paper proposes an expert system for Cloud evaluation that addresses emerging evaluation challenges in the context of Cloud Computing. Based on the knowledge and data accumulated by exploring the existing evaluation work, this expert system has been conceptually validated to be able to give suggestions and guidelines for implementing new evaluation experiments. As such, users can conveniently obtain evaluation experiences by using this expert system, which is essentially able to make existing efforts in Cloud services evaluation reusable and sustainable.

cs.DC↗

A Factor Framework for Experimental Design for Performance Evaluation of Commercial Cloud Services

Given the diversity of commercial Cloud services, performance evaluations of candidate services would be crucial and beneficial for both service customers (e.g. cost-benefit analysis) and providers (e.g. direction of service improvement). Before an evaluation implementation, the selection of suitable factors (also called parameters or variables) plays a prerequisite role in designing evaluation experiments. However, there seems a lack of systematic approaches to factor selection for Cloud services performance evaluation. In other words, evaluators randomly and intuitively concerned experimental factors in most of the existing evaluation studies. Based on our previous taxonomy and modeling work, this paper proposes a factor framework for experimental design for performance evaluation of commercial Cloud services. This framework capsules the state-of-the-practice of performance evaluation factors that people currently take into account in the Cloud Computing domain, and in turn can help facilitate designing new experiments for evaluating Cloud services.

cs.DC↗

Towards a Taxonomy of Performance Evaluation of Commercial Cloud Services

Cloud Computing, as one of the most promising computing paradigms, has become increasingly accepted in industry. Numerous commercial providers have started to supply public Cloud services, and corresponding performance evaluation is then inevitably required for Cloud provider selection or cost-benefit analysis. Unfortunately, inaccurate and confusing evaluation implementations can be often seen in the context of commercial Cloud Computing, which could severely interfere and spoil evaluation-related comprehension and communication. This paper introduces a taxonomy to help profile and standardize the details of performance evaluation of commercial Cloud services. Through a systematic literature review, we constructed the taxonomy along two dimensions by arranging the atomic elements of Cloud-related performance evaluation. As such, this proposed taxonomy can be employed both to analyze existing evaluation practices through decomposition into elements and to design new experiments through composing elements for evaluating performance of commercial Cloud services. Moreover, through smooth expansion, we can continually adapt this taxonomy to the more general area of evaluation of Cloud Computing.

cs.DC↗

On a Catalogue of Metrics for Evaluating Commercial Cloud Services

Given the continually increasing amount of commercial Cloud services in the market, evaluation of different services plays a significant role in cost-benefit analysis or decision making for choosing Cloud Computing. In particular, employing suitable metrics is essential in evaluation implementations. However, to the best of our knowledge, there is not any systematic discussion about metrics for evaluating Cloud services. By using the method of Systematic Literature Review (SLR), we have collected the de facto metrics adopted in the existing Cloud services evaluation work. The collected metrics were arranged following different Cloud service features to be evaluated, which essentially constructed an evaluation metrics catalogue, as shown in this paper. This metrics catalogue can be used to facilitate the future practice and research in the area of Cloud services evaluation. Moreover, considering metrics selection is a prerequisite of benchmark selection in evaluation implementations, this work also supplements the existing research in benchmarking the commercial Cloud services.

cs.DC↗