Constraining neutrino mass remains an elusive challenge in modern physics.Precision measurements are expected from several upcoming cosmological probes of large-scale structure.Achieving this goal relies on an equal level of precision from theoretical predictions of neutrino clustering.Numerical simulations of the non-linear evolution of cold dark matter and neutrinos play a pivotal role in this process.We incorporate neutrinos into the cosmological N-body code CUBEP3M and discuss the challenges associated with pushing to the extreme scales demanded by the neutrino problem.We highlight code optimizations made to exploit modern high performance computing architectures and present a novel method of data compression that reduces the phase-space particle footprint from 24 bytes in single precision to roughly 9 bytes.We scale the neutrino problem to the Tianhe-2 supercomputer and provide details of our production run,named Tian Nu,which uses 86%of the machine(13 824 compute nodes).With a total of 2.97 trillion particles,Tian Nu is currently the world’s largest cosmological N-body simulation and improves upon previous neutrino simulations by two orders of magnitude in scale.We finish with a discussion of the unanticipated computational challenges that were encountered during the Tian Nu runtime.
The T2K Collaboration has recently reported a remarkable indication of the υμ＋ υe oscillation which is consistent with a relatively large value of θ13 in the three-flavor neutrino mixing scheme. We show that it is possible to account for such a result of θ13 by introducing a natural perturbation to the democratic neutrino mixing pattern, without or with CP violation. A testable correlation between θ13 and θ23 is predicted in this ansatz. We also discuss the Wolfenstein-like parametrization of neutrino mixing, and comment on other possibilities of generating sufficiently large θ13 at the electroweak scale.
The neutrinoless double-beta （0vββ） decay is a unique process used to identify the Majorana nature of massive neutrinos, and its rate depends on the size of the effective Majorana neutrino mass （m）ee- We put forward a novel ＇coupling-rod＇ diagram to describe （m）ee in the complex plane, by which the effects of the neutrino mass ordering and CP-violating phases on （m）ee are intuitively understood. We show that this geometric language allows us to easily obtain the maximum and minimum of I（m）eel. It remains usable even if there is a kind of new physics contributing to （m）ee, and it can also be extended to describe the effective Majorana masses （m）eμ, （m）eτ, （m）μμ, （m）,μτ and （m）ττ which may appear in some other lepton-number violating processes.
We propose to understand the mixing angles and CP-violating phases from the A（48） family symmetry combined with the generalized CP symmetry. A model-independent analysis is performed by scanning all the possible symmetry breaking chains. We find a new mixing pattern with only one free parameter, excellent agreement with the observed mixing angles can be achieved and all the CP-violating phases are predicted to take nontrivial values. This mixing pattern is testable in the near future neutrino oscillation and neutrinoless double-beta decay experiments. Finally, a flavor model is constructed to realize this mixing pattern.
The recent measurements on Rκ and Rπ imply that there exists a possible violation of the leptonic flavor universality which is one of the cornerstones of the Standard Model. It is suggested that a mixing between sterile and active neutrinos might induce such a violation. In this work we consider the scenarios with one or two sterile neutrinos to explicitly realize the data while the constraints from the available experiments have been taken into account. Moreover, as indicated in literature, the deviation of the real PMNS matrix from the symmetric patterns may be due to a μ-τ asymmetry, therefore the measurements on RD（Ds）eμ=F（D（Ds）→e＋νe）/Г（D（Ds）→μ＋νμ） and RD（Ds）μτ=Г（D（Ds）→μ＋νμ）Г（D（Ds）→ι＋ντ） （and for some other heavy mesons B± and Bc etc.） may shed more light on the physics responsible for the violation of the leptonic flavor universality. The data of BESⅢ are available to test the universality and that of future charm-tau factories will provide more accurate information. In this work, we will discuss RD（Ds）eμ and RD（Ds）μτ in detail and also briefly consider the cases for B± and Bc.
Supersymmetry （SUSY） may be one of the most favored extensions of the Standard Model （SM）, but so far at the LHC no evidence of SUSY particles has been observed. An obvious question is whether they have already emerged but escaped our detection, or whether they do not exist at all. We propose that the future ILC may provide sufficient energy and luminosity to produce SUSY particles as long as they are not too heavy. Superflavor symmetry associates production rates of SUSY mesinos with those of regular mesons, because both contain a heavy constituent and a light one. In this work, we estimate the production rate of SUSY mesinos near their production threshold and compare it with BB production. Our analysis indicates that if SUSY mesinos with masses below √s/2 （√s is the ILC energy） exist, they could be observed at the future ILC or even the proposed CEPC in China.
We study the constraints on dark matter（DM） annihilation/decay from the Fermi-LAT Isotropic Gamma-Ray Background（IGRB） observation.We consider the contributions from both extragalactic and galactic DM components.For DM annihilation,the evolution of extragalactic DM halos is taken into account.We find that the IGRB annihilation constraints under some DM subhalo models can be comparable to those derived from the observations of dwarf spheroidal galaxies and CMB.We also use the IGRB results to constrain the parameter regions accounting for the latest AMS-02 electron-positron anomaly.We find that the majority of DM annihilation/decay channels are strongly disfavored by the latest Fermi-LAT IGRB observation;only DM decays to μ^＋μ^-and 4μ channels may be valid.
Investigating the CKM matrix in different parameterization schemes, it is noticed that those schemes can be divided into a few groups where the sine values of the CP phase for each group are approximately equal i.e. there exist several relations among the CP phases. Using those relations, several approximate equalities among the elements of CKM matrix are established. The case can also be generalized to the PMNS matrix for the lepton sector. Assuming them to be exact, there are infinite numbers of solutions and by choosing special values for the free parameters in those solutions, several textures presented in the literature are obtained. Other authors have derived several mixing textures by using presumed symmetries; amazingly, some, though not all, of their forms axe the same as those we obtained. This hints at the existence of a hidden symmetry which is broken in the practical world. Nature makes its own selection of the underlying symmetry and the way to break it, while we just guess what it is.
The Daya Bay collaboration has recently reported its first νe → νe oscillation result which points to θ13 8.8 ± 0.8 （best-fit ±1σ range） or θ13 = 0 at the 5.2σ level. The fact that this smallest neutrino mixing angle is not strongly suppressed motivates us to look into the underlying structure of lepton flavor mixing and CP violation. Two phenomenological strategies are outlined： （1） the lepton flavor mixing matrix U consists of a constant leading term U0 and a small perturbation term U ; and （2） the mixing angles of U are associated with the lepton mass ratios. Some typical patterns of U0 are reexamined by constraining their respective perturbations with current experimental data. We illustrate a few possible ways to minimally correct U0 in order to fit the observed values of three mixing angles. We point out that the structure of U may exhibit an approximate μ-τ permutation symmetry in modulus, and reiterate the geometrical description of CP violation in terms of the leptonic unitarity triangles. The salient features of nine distinct parametrizations of U are summarized, and its Wolfenstein-like expansion is presented by taking U0 to be the democratic mixing pattern.
The China Jinping Underground Laboratory（CJPL）, which has the lowest cosmic-ray muon flux and the lowest reactor neutrino flux of any laboratory, is ideal to carry out low-energy neutrino experiments. With two detectors and a total fiducial mass of 2000 tons for solar neutrino physics（equivalently, 3000 tons for geo-neutrino and supernova neutrino physics）, the Jinping neutrino experiment will have the potential to identify the neutrinos from the CNO fusion cycles of the Sun, to cover the transition phase for the solar neutrino oscillation from vacuum to matter mixing, and to measure the geo-neutrino flux, including the Th/U ratio. These goals can be fulfilled with mature existing techniques. Efforts on increasing the target mass with multi-modular neutrino detectors and on developing the slow liquid scintillator will increase the Jinping discovery potential in the study of solar neutrinos,geo-neutrinos, supernova neutrinos, and dark matter.
John F.Beacom陈少敏程建平Sayed N.Doustimotlagh高原宁龚光华宫辉郭磊韩然何红建黄性涛李荐民李金李默涵李学潜廖玮林贵林刘佐伟William Mc DonoughOndˇrej rmek唐健万林焱王元清王喆王综轶魏瀚宇习宇飞徐晔许勋杰杨振伟姚春发Minfang Yeh岳骞张黎明张洋赵志宏郑阳恒周详朱相雷Kai Zuber
