56570203
Diffuse Ultra-High Energy Neutrino Fluxes and Physics Beyond the Standard Model
Abstract We study spectral distortions of diffuse ultra-high energy (UHE) neutrino flavour fluxes resulting due to physics beyond the Standard Model (SM). Even large spectral differences between flavours at the source are massaged into a common shape at earth by SM oscillations, thus, any significant observed spectral differences are an indicator of new physics present in the oscillation probability during propagation. Lorentz symmetry violation (LV) and neutrino decay are examples, and result in significant distortion of the fluxes and of the well-known bounds on them, which may allow UHE detectors to probe LV parameters, lifetimes and the mass hierarchy over a broad range.
15261294
Twisted flavors and tribimaximal neutrino mixing.
A new framework for handling flavor symmetry breaking in the neutrino sector is discussed where the source of symmetry breaking is traced to the global property of right-handed neutrinos in extra-dimensional space. Light neutrino phenomenology has rich and robust predictions such as the tribimaximal form of generation mixing, controlled mass spectrum, and no need of flavor mixing couplings in the theory.
2665857
Asymmetry and Minimality of Quark Mass Matrices
We systematically investigate general forms of mass matrices for three-generation up and down quarks, including asymmetrical ones in generation space. Viable zero matrix elements are explored which are compatible with the current observation of masses and mixing angles, and also with the recent measurement of CP violation in the B-meson system. The simplest form with the maximal number of vanishing matrix elements is found to be almost consistent with the experimental data, but has an unsatisfactory point that one of the mixing angles is slightly large. At the next-to-minimal level, it is found with help of leptonic generation mixing that only six patterns of mass matrices well describe the experimental data. These sets of mass textures predict all the properties of quarks, including the CP violation, as well as the large (charged) lepton mixing, which may be appropriate for the atmospheric neutrino in the grand unification scheme.
7969385
Hybrid textures in minimal seesaw mass matrices
Abstract In the context of the minimal seesaw framework, we discuss the implications of Dirac and Majorana mass matrices in which two properties coexist, namely, equalities among matrix elements and texture zeros. Among the large number of general possibilities, only 12 patterns are found to be consistent with the global neutrino oscillation data at the level of the most minimal number of free parameters. The predictions of the allowed textures for mass hierarchy, θ 13 and effective mass governing neutrino-less double beta decay are discussed. We also explore the possibility of having non-zero CP violation for each allowed solution. We find that only one allowed solution can accommodate both low and high energy CP violation. We discuss the prediction of this solution for leptogenesis and explore the correlation, between leptogenesis and low energy CP violation.
118565569
Atmospheric sterile neutrinos
A bstractWe study production of sterile neutrinos in the atmosphere and their detection at Super-Kamiokande. A sterile neutrino in the mass range $ 1\;{\text{MeV}} \lesssim {M_{\text{N}}} \lesssim {1}0{5}\;{\text{MeV}} $ is produced by muon or pion decay, and decays to an electron-positron pair and an active neutrino. Such a decay of the sterile neutrino leaves two electron-like Cherenkov rings in the detector. We estimate the sterile neutrino flux from the well-established active neutrino fluxes and study the number of the decay events in the detector. The upper bounds for the active-sterile mixings are obtained by comparing the 2e-like events from the sterile neutrino decays and the observed data by Super-Kamiokande. The upper bound for the muon type mixing Θμ is found to be $ {\left| {{\Theta_{\mu }}} \right|^2} \lesssim 5 \times {10^{{ - 5}}} $ for $ 20\;{\text{MeV}} \lesssim {M_N} \lesssim 80\;{\text{MeV}} $, which is significantly loosened compared to the previous estimation. We demonstrate that the opening angle and the total energy of the rings may serve as diagnostic tools to discover the sterile neutrinos in further data accumulation and future upgraded facilities. The directional asymmetry of the events is a sensitive measure of the diminishment of the sterile neutrino flux due to the decays on the way to the detector.
11888215
The Role and Detectability of the Charm Contribution to Ultra High Energy Neutrino Fluxes
It is widely believed that charm meson production and decay may play an important role in high energy astrophysical sources of neutrinos, especially those that are baryon-rich, providing an environment conducive to pp interactions. Using slow-jet supernovae (SJS) as an example of such a source, we study the detectability of high-energy neutrinos, paying particular attention to those produced from charmed-mesons. We highlight important distinguishing features in the ultra-high energy neutrino flux which would act as markers for the role of charm in the source. In particular, charm leads to significant event rates at higher energies, after the conventional (π,K) neutrino fluxes fall off. We calculate event rates both for a nearby single source and for diffuse SJS fluxes for an IceCube-like detector. By comparing muon event rates for the conventional and prompt fluxes in different energy bins, we demonstrate the striking energy dependence in the rates induced by the presence of charm. We also show that it leads to an energy dependant flux ratio of shower to muon events, providing an additional important diagnostic tool for the presence of prompt neutrinos. Motivated by the infusion of high energy anti-electron neutrinos into the flux by charm decay, we also study the detectability of the Glashow resonance due to these sources.
119232581
Pomeron dynamics in the AdS space and structure functions of hadrons at small x
The Pomeron dynamics is investigated via deep inelastic scattering (DIS) at small x in the framework of holographic quantum chromodynamics. The small x DIS process is assumed to be described by the graviton exchange between external vector current and hadron in the AdS space. Our calculations for Fp2, Fπ2, as well as the longitudinal counterpart FpL are consistent with the experimental data. We discuss origins of a difference between F2 and FL in our approach.
119097645
Nucleon structure functions at small $x$ via the Pomeron exchange in AdS space with a soft infrared wall
We present analyses on nucleon structure functions at the small Bjorken-$x$ in the framework of holographic QCD. In this study, we improve the description of the target nucleon in the current setup of the holographic model by introducing a soft-wall AdS/QCD model, in which the AdS geometry is smoothly cut off at IR. Combining the improved Pomeron-nucleon coupling and the wave function of the 5D U(1) vector field with the BPST Pomeron exchange kernel, then we obtain the structure functions. Here we focus on the nonperturbative kinematical region, where $10^{-6} \leq x \leq 10^{-2}$ and $0.1 \leq Q^2 \leq 10$ [GeV$^2$], and show that our calculations for $F_2^p$ and $F_L^p$ are consistent with experimental data of the deep inelastic scattering at HERA. Furthermore, we find that the resulting longitudinal-to-transverse ratio of the structure functions, $F_L^p/F_T^p$, depends on both of $x$ and $Q^2$.
119262648
Transition from soft- to hard-Pomeron in the structure functions of hadrons at small-$x$ from holography
We study the nucleon and pion structure functions at small Bjorken-$x$ region in the framework of holographic QCD with a special emphasis on the roles of AdS space wave functions. Using the BPST kernel for the Pomeron exchange and calculating its coupling to target hadrons in the AdS space, we obtain $F_2$ structure functions at the small-$x$. Results for the proton $F^p_2$ as well as the pion $F^\pi_2$ are consistent with experimental data of the deep inelastic scattering and the forward electroproduction of a neutron. Observed $Q^2$ dependence of the Pomeron intercept is well reproduced from soft non-perturbatibve $(Q^2 \sim 0)$ to hard perturbative $(Q^2 \gg 1 GeV^2)$ region. We find the interplay between soft and hard Pomerons is closely related with behavior of AdS wave functions of hadrons and the virtual photon.