arXiv subjects

He Zhang

Publications and source records attributed to He Zhang.

At least 343 records · Page 19Linked to original sources

arXiv2010

Non-unitarity of the leptonic mixing matrix in the TeV-scale type-I seesaw model

The non-unitarity effects in the leptonic flavor mixing are regarded as one of the generic features of the type-I seesaw model. Therefore, we explore these effects in the TeV-scale type-I seesaw model, and show that there exist non-trivial correlations among the non-unitarity parameters, stemming from the typical flavor structure of the low-scale seesaw model. In general, it follows from analytical discussions and numerical results that all the six non-unitarity parameters are related to three model parameters, while the widely studied parameters η_{eτ} and η_{μτ} cannot be phenomenologically significant

hep-ph↗

arXiv2010

Dynamical Jumping Real-Time Fault-Tolerant Routing Protocol for Wireless Sensor Networks

In time-critical wireless sensor network (WSN) applications, a high degree of reliability is commonly required. A dynamical jumping real-time fault-tolerant routing protocol (DMRF) is proposed in this paper. Each node utilizes the remaining transmission time of the data packets and the state of the forwarding candidate node set to dynamically choose the next hop. Once node failure, network congestion or void region occurs, the transmission mode will switch to jumping transmission mode, which can reduce the transmission time delay, guaranteeing the data packets to be sent to the destination node within the specified time limit. By using feedback mechanism, each node dynamically adjusts the jumping probabilities to increase the ratio of successful transmission. Simulation results show that DMRF can not only efficiently reduce the effects of failure nodes, congestion and void region, but also yield higher ratio of successful transmission, smaller transmission delay and reduced number of control packets.

cs.NI↗

arXiv2009

The Minimal Seesaw Model at the TeV Scale

We point out that the minimal seesaw model can provide a natural framework to accommodate tiny neutrino masses, while its experimental testability and notable predictiveness are still maintained. This possibility is based on the observation that two heavy right-handed Majorana neutrinos in the minimal seesaw model may naturally emerge as a pseudo-Dirac fermion. In a specific scenario, we show that the tri-bimaximal neutrino mixing can be produced, and only the inverted neutrino mass hierarchy is allowed. The low-energy phenomena, including non-unitarity effects in neutrino oscillations, neutrinoless double-beta decays and rare lepton-flavor-violating decays of charged leptons l_alpha to l_beta + gamma, have been explored. The collider signatures of the heavy singlet neutrino are also briefly discussed.

hep-ph↗

arXiv2009

Non-standard neutrino interactions in the Zee-Babu model

We investigate non-standard neutrino interactions (NSIs) in the Zee--Babu model. The size of NSIs predicted by this model is obtained from a full scan over the parameter space, taking into account constraints from low-energy experiments such as searches for lepton flavor violation (LFV) and the requirement to obtain a viable neutrino mass matrix. The dependence on the scale of new physics as well as on the type of the neutrino mass hierarchy is discussed. We find that NSIs at the source of a future neutrino factory may be at an observable level in the nu_e to nu_tau and/or nu_mu to nu_tau channels. In particular, if the doubly charged scalar of the model has a mass in reach of the LHC and if the neutrino mass hierarchy is inverted, a highly predictive scenario is obtained with observable signals at the LHC, in upcoming neutrino oscillation experiments, in LFV processes, and for NSIs at a neutrino factory.

hep-ph↗

arXiv2009

Non-unitary neutrino mixing and CP violation in the minimal inverse seesaw model

We propose a simplified version of the inverse seesaw model, in which only two pairs of the gauge-singlet neutrinos are introduced, to interpret the observed neutrino mass hierarchy and lepton flavor mixing at or below the TeV scale. This minimal inverse seesaw scenario (MISS) is technically natural and experimentally testable. In particular, we show that the effective parameters describing the non-unitary neutrino mixing matrix are strongly correlated in the MISS, and thus, their upper bounds can be constrained by current experimental data in a more restrictive way. The Jarlskog invariants of non-unitary CP violation are calculated, and the discovery potential of such new CP-violating effects in the near detector of a neutrino factory is discussed.

hep-ph↗

arXiv2009

Exact and Approximate Formulas for Neutrino Mixing and Oscillations with Non-Standard Interactions

We present, both exactly and approximately, a complete set of mappings between the vacuum (or fundamental) leptonic mixing parameters and the effective ones in matter with non-standard neutrino interaction (NSI) effects included. Within the three-flavor neutrino framework and a constant matter density profile, a full set of sum rules is established, which enables us to reconstruct the moduli of the effective leptonic mixing matrix elements, in terms of the vacuum mixing parameters in order to reproduce the neutrino oscillation probabilities for future long-baseline experiments. Very compact, but quite accurate, approximate mappings are obtained based on series expansions in the neutrino mass hierarchy parameter η\equiv Δm^2_{21}/Δm^2_{31}, the vacuum leptonic mixing parameter s_{13} \equiv \sinθ_{13}, and the NSI parameters ε_{αβ}. A detailed numerical analysis about how the NSIs affect the smallest leptonic mixing angle θ_{13}, the deviation of the leptonic mixing angle θ_{23} from its maximal mixing value, and the transition probabilities useful for future experiments are performed using our analytical results.

hep-ph↗

arXiv2009

Non-unitarity effects in a realistic low-scale seesaw model

We analyze the structure of the non-unitary leptonic mixing matrix in the inverse seesaw model with heavy singlets accessible at the LHC. In this model, unlike in the usual TeV seesaw scenarios, thelow-scale right-handed neutrinos do not suffer from naturalness issues. Underlying correlations among various parameters governing the non-unitarity effects are established, which leads to a considerable improvement of the generic non-unitarity bounds. In view of this, we study the discovery potential of the non-unitarity effects at future experiments, focusing on the sensitivity limits at a neutrino factory.

hep-ph↗

arXiv2008

Non-Standard Interaction Effects at Reactor Neutrino Experiments

We study non-standard interactions (NSIs) at reactor neutrino experiments, and in particular, the mimicking effects on θ_13. We present generic formulas for oscillation probabilities including NSIs from sources and detectors. Instructive mappings between the fundamental leptonic mixing parameters and the effective leptonic mixing parameters are established. In addition, NSI corrections to the mixing angles θ_13 and θ_12 are discussed in detailed. Finally, we show that, even for a vanishing θ_13, an oscillation phenomenon may still be observed in future short baseline reactor neutrino experiments, such as Double Chooz and Daya Bay, due to the existences of NSIs.

hep-ph↗

arXiv2008

Non-Standard Neutrino Interactions from a Triplet Seesaw Model

We investigate non-standard neutrino interactions (NSIs) in the triplet seesaw model featuring non-trivial correlations between NSI parameters and neutrino masses and mixing parameters. We show that sizable NSIs can be generated as a consequence of a nearly degenerate neutrino mass spectrum. Thus, these NSIs could lead to quite significant signals of lepton flavor violating decays such as μ^- \to e^- ν_e antiν_μand μ^+ \to e^+ antiν_e ν_μat a future neutrino factory, effects adding to the uncertainty in determination of the Earth matter density profile, as well as characteristic patterns of the doubly charged Higgs decays observable at the Large Hadron Collider.

hep-ph↗

arXiv2008

Updated Values of Running Quark and Lepton Masses

Reliable values of quark and lepton masses are important for model building at a fundamental energy scale, such as the Fermi scale M_Z \approx 91.2 GeV and the would-be GUT scale Λ_GUT \sim 2 \times 10^16 GeV. Using the latest data given by the Particle Data Group, we update the running quark and charged-lepton masses at a number of interesting energy scales below and above M_Z. In particular, we take into account the possible new physics scale (μ\sim 1 TeV) to be explored by the LHC and the typical seesaw scales (μ\sim 10^9 GeV and μ\sim 10^12 GeV) which might be relevant to the generation of neutrino masses. For illustration, the running masses of three light Majorana neutrinos are also calculated. Our up-to-date table of running fermion masses are expected to be very useful for the study of flavor dynamics at various energy scales.

hep-ph↗

arXiv2008

Electronic Conductivity Upturn of HOPG Contrast to Transport Properties of Polycrystal Graphite

The transport properties of highly oriented pyrolitic graphite (HOPG) and polycrystal graphite have been studied. The electric conductivity of HOPG is several times larger than that of the polycrystal graphite. Along with the large magnetoresistances (MR), the polycrystal graphite show the accordant semiconductor-like character in a wide temperature (roughly range from 20K to 120K) under 0, 4, 8, 12 T applied magnetic field, while the magnetic-field-induced metal-semiconductor-like transition was only found in HOPG. The difference of transport properties originates from the Coulomb interaction quasipartical in HOPG graphite layers in contrast with the grain boundary scattering in the polycrystal graphite.

cond-mat.mtrl-sci↗

arXiv2007

Generalized Friedberg-Lee model for neutrino masses and leptonic CP violation from mu-tau symmetry breaking

Assuming the Majorana nature of massive neutrinos, we generalize the Friedberg-Lee neutrino mass model to include CP violation in the neutrino mass matrix M_ν. The most general case with all the free parameters of M_νbeing complex is discussed. We show that a favorable neutrino mixing pattern (with θ_12 \approx 35.3^\circ, θ_23=45^\circ, θ_13 \neq 0^\circ and δ=90^\circ) can naturally be derived from M_ν, if it has an approximate or softly-broken μ-τsymmetry. We also point out a different way to obtain the nearly tri-bimaximal neutrino mixing pattern with δ=0^\circ and non-vanishing Majorana phases.

hep-ph↗

arXiv2007

Flavor S_4 times Z_2 symmetry and neutrino mixing

We present a model of the lepton masses and flavor mixing based on the discrete group $S_4 \times Z_2$. In this model, all the charged leptons and neutrinos are assigned to the $3_α$ representation of $S_4$ in the Yamanouchi bases. The charged lepton and neutrino masses are mainly determined by the vacuum expectation value structures of the Higgs fields. A nearly tri-bimaximal lepton flavor mixing pattern, which is in agreement with the current experimental results, can be accommodated in our model. The neutrino mass spectrum takes the nearly degenerate pattern, and thus can be well tested in the future precise experiments.

hep-ph↗

arXiv2007

One-loop renormalization group equations of the neutrino mass matrix in the triplet seesaw model

Within the framework of the standard model plus one heavy Higgs triplet, we derive a full set of one-loop renormalization group equations of the neutrino mass matrix and Higgs couplings in both full and effective theories. The explicit RGEs of neutrino masses, flavor mixing angles and CP-violating phases are also obtained, and their non-trivial running behaviors around the Higgs triplet mass threshold are numerically illustrated.

hep-ph↗

arXiv2006

A Minimal Type II Seesaw Model

We propose a minimal type II seesaw model by introducing only one right-handed neutrino besides the $SU(2)_{L}$ triplet Higgs to the standard model. In the usual type II seesaw models with several right-handed neutrinos, the contributions of the right-handed neutrinos and the triplet Higgs to the CP asymmetry, which stems from the decay of the lightest right-handed neutrino, are proportional to their respective contributions to the light neutrino mass matrix. However, in our minimal type II seesaw model, this CP asymmetry is just given by the one-loop vertex correction involving the triplet Higgs, even though the contribution of the triplet Higgs does not dominate the light neutrino masses. For illustration, the Fritzsch-type lepton mass matrices are considered.

hep-ph↗

arXiv2006

Nearly Tri-bimaximal Neutrino Mixing and CP Violation from mu-tau Symmetry Breaking

Assuming the Majorana nature of massive neutrinos, we generalize the Friedberg-Lee neutrino mass model to include CP violation in the neutrino mass matrix $M^{}_ν$. We show that a favorable neutrino mixing pattern (with $θ^{}_{12} \approx 35.3^\circ$, $θ^{}_{23} = 45^\circ$, $θ^{}_{13} \neq 0^\circ$ and $δ= 90^\circ$) can naturally be derived from $M^{}_ν$, if it has an approximate or softly-broken $μ$-$τ$ symmetry. We point out a different way to obtain the nearly tri-bimaximal neutrino mixing with $δ= 0^\circ$ and non-vanishing Majorana phases. The most general case, in which all the free parameters of $M^{}_ν$ are complex and the resultant neutrino mixing matrix contains both Dirac and Majorana phases of CP violation, is also discussed.

hep-ph↗

arXiv2006

Sum rules of four-neutrino mixing in matter

Assuming the existence of one light sterile neutrino, we investigate the neutrino flavor mixing matrix in matter. Sum rules between the mixing parameters in vacuum and their counterparts in matter are derived. By using these new sum rules, we obtain the simple but exact expressions of the effective flavor mixing matrix in matter in terms of neutrino masses and the mixing parameters in vacuum. The rephasing invariants, sides of unitarity quadrangles and oscillation probabilities in matter are also achieved. Our model-independent results will be very helpful for analyzing flavor mixing and CP violation in the future long-baseline neutrino oscillation experiments.

hep-ph↗

arXiv2006

On the Koide-like Relations for the Running Masses of Charged Leptons, Neutrinos and Quarks

Current experimental data indicate that the Koide relation for the pole masses of charged leptons, which can be parametrized as $Q^{pole}_l = 2/3$, is valid up to the accuracy of $O(10^{-5})$. We show that the running masses of charged leptons fail in satisfying the Koide relation (i.e., $Q_l(μ) \neq 2/3$), but the discrepancy between $Q_l (μ)$ and $Q^{pole}_l$ is only about 0.2% at $μ=M_Z$. The Koide-like relations for the running masses of neutrinos ($1/3 < Q_ν(M_Z) < 0.6$), up-type quarks ($Q_{U}(M_Z) \sim 0.89$) and down-type quarks ($Q_{D}(M_Z) \sim 0.74$) are also examined from $M_Z$ up to the typical seesaw scale $M_R \sim 10^{14}$ GeV, and they are found to be nearly stable against radiative corrections. The approximate stability of $Q_{U}(μ)$ and $Q_{D}(μ)$ is mainly attributed to the strong mass hierarchy of quarks, while that of $Q_l(μ)$ and $Q_ν(μ)$ is essentially for the reason that the lepton mass ratios are rather insensitive to radiative corrections.

hep-ph↗