Neutrino Phenomenology of gauged L_mu - L_tau: MINOS and beyond
Julian Heeck, Werner Rodejohann
备注：
3 pages, 2 figures. Talk given at the 12th International Workshop on Neutrino Factories, Superbeams and Beta Beams (NuFact10), October 20-25, 2010, Mumbai, India
If a Z' gauge boson from a gauged L_mu - L_tau symmetry is very light, it is associated with a long-range leptonic force. In this case the particles in the Sun create via mixing of the Z' with the Standard Model Z a flavor-dependent potential for muon neutrinos in terrestrial long-baseline experiments. The potential changes sign for anti-neutrinos and hence can lead to apparent differences in neutrino and anti-neutrino oscillations without introducing CP or CPT violation. This could for instance explain the recently found discrepancy in the MINOS experiment. We obtain the associated parameters of gauged L_mu - L_tau required to explain this anomaly. The consequences for future long-baseline experiments are also discussed, and we compare the scenario to standard NSIs. When used to explain MINOS, both approaches have severe difficulties with existing limits.
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If a Z' gauge boson of a gauged L_mu - L_tau symmetry is very light, it is associated with a long-range leptonic force. In this case the particles in the Sun create via mixing of Z' with the Standard Model Z a flavor-dependent potential for muon neutrinos in terrestrial long-baseline experiments. The potential changes sign for anti-neutrinos and hence can lead to apparent differences in neutrino and anti-neutrino oscillations without introducing CP or CPT violation. This could for instance explain the recently found discrepancy in the survival probabilities of muon neutrinos and anti-neutrinos…
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The fate of R-parity is one of the central issues in the minimal supersymmetric standard model (MSSM). Gauged $B-L$ symmetry provides a natural framework for addressing this question. Recently, it was pointed out that the minimal such theory does not need any additional Higgs if the $B-L$ breaking is achieved through the VEVs of right-handed sneutrinos, which ties the new physics scale to the scale of the MSSM. We show here that this immediately leads to an important prediction of two light sterile neutrinos, which can play a significant role in the BBN and neutrino oscillations. We also discu…
The role of repulsive interactions in statistical systems of Bose particles is investigated. Three different phenomenological frameworks are considered: a mean field model, an excluded volume model, and a model with a medium dependent effective mass. All three models are tuned to yield similar equations of state, with only minor deviations from the ideal Bose gas at small chemical potentials. Our analysis indicates, however, that these models lead to qualitatively different results for the Bose-Einstein condensation phenomenon. We discuss the different aspects of this phenomenon, namely, an on…
We study the structure of the neutrino mass matrix in the minimal gauged U(1)$_{L_μ-L_τ}$ model, where three right-handed neutrinos are added to the Standard Model in order to obtain non-zero masses for active neutrinos. Because of the U(1)$_{L_μ-L_τ}$ gauge symmetry, the structure of both Dirac and Majorana mass terms of neutrinos is tightly restricted. In particular, the inverse of the neutrino mass matrix has zeros in the $(μ,μ)$ and $(τ,τ)$ components, namely, this model offers a symmetric realization of the so-called two-zero-minor structure in the neutrino mass matrix. Due to these const…
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We consider the phenomenology of the gauged abelian symmetry B + 3 (L_e - L_mu - L_tau). Right-handed neutrinos necessary to cancel triangle anomalies are used in a type-I seesaw scheme to create active neutrino masses. Breaking the B + 3 (L_e - L_mu - L_tau) symmetry spontaneously below the seesaw scale generates low energy neutrino mass matrices with the approximate symmetries L_e (leading to normal hierarchy) or L_e - L_mu - L_tau (inverted hierarchy). For the latter we need to introduce a Z_2 symmetry which decouples one of the right-handed neutrinos. If exact, this Z_2 leads to a Majorana…
The Standard Model's accidental and anomaly-free currents: $B-L$, $L_e-L_μ$, $L_e-L_τ$, and $L_μ-L_τ$, could be indicative of a hidden gauge structure beyond the Standard Model. Additionally, neutrino masses can be generated by a dimension-5 operator that generically breaks all of these symmetries. It is therefore important to investigate the compatibility of a gauged $U'(1)$ and neutrino phenomenology. We consider gauging each of the symmetries above with a minimal extended matter content. This includes the $Z'$, an order parameter to break the $U'(1)$, and three right-handed neutrinos. We fi…
The latest results of anomalous muon magnetic moment at Fermilab show a discrepancy of 4.2 $σ$ between the Standard Model (SM) prediction and experimental value. In this work, we revisit $U(1)_{L_μ-L_τ}$ symmetry with in the paradigm of scotogenic model which explains muon ($g-2$) and neutrino mass generation, simultaneously. The mass of new gauge boson $M_{Z_{μτ}}$ generated after the spontaneous symmetry breaking of $U(1)_{L_μ-L_τ}$ is constrained, solely, in light of the current neutrino oscillation data to explain muon ($g-2$). In particular, we have obtained two regions I and II, around 1…
Recent results from the MINOS accelerator neutrino experiment suggest a possible difference between nu_mu and anti-nu_mu disappearance oscillation parameters, which one may ascribe to a new long-distance potential acting on neutrinos. As a specific example, we consider a model with gauged B - L_e - 2 L_tau number that contains an extremely light new vector boson m_Z' < 10^-18 eV and extraordinarily weak coupling alpha' < 10^-52. In that case, differences between nu_mu to nu_tau and anti-nu_mu to anti-nu_tau oscillations can result from a long-range potential due to neutrons in the Earth and th…
Among the combinations $L_e-L_μ$, $L_e-L_τ$ and $L_μ-L_τ$ any one can be gauged in anomaly free way with the standard model gauge group. The masses of these gauge bosons can be so light that it can induce long-range forces on the Earth due to the electrons in the Sun. This type of forces can be constrained significantly from neutrino oscillation. As the sign of the potential is opposite for neutrinos and antineutrinos, a magnetized iron calorimeter detector (ICAL) would be able to produce strong constraint on it. We have made conservative studies of these long-range forces with atmospheric neu…
