The moderately large measured value of theta13 signals a departure from the approximate two-flavour oscillation framework. As a consequence, the relation between the value of theta23 in nature, and the mixing angle measured in muon neutrino disappearance experiments is non-trivial. In this paper, we calculate this relation analytically. We also derive the correct conversion between degenerate values of theta23 in the two octants. Through simulations of a muon neutrino disappearance experiment, we show that there are observable consequences of not using the correct relation in calculating oscillation probabilities. These include a wrong best-fit value for theta23, and spurious sensitivity to the octant of theta23.
We present the Bayesian method for evaluating the evidence for a non-zero value of the leptonic mixing angle theta_13 and CP-violation in neutrino oscillation experiments. This is an application of the well-established method of Bayesian model selection, of which we give a concise and pedagogical overview. When comparing the hypothesis theta_13 = 0 with hypotheses where theta_13 > 0 using global data but excluding the recent reactor measurements, we obtain only a weak preference for a non-zero theta_13, even though the significance is over 3 sigma. We then add the reactor measurements one by o…
Recently, MIT group found a numerical solution to non-abelian gauge fields which is shown to contain non-integer topological number. Using this fact, V.V.Khoze has argued that the vacuum theta angle is zero. Here, we study this in a complimentary way--its physical respect. The key point is MIT solution has an infinite action. Using this, we prove the vacuum theta angle is zero at semiclassical level.
When solar neutrino and KamLAND data are analyzed separately one finds that, even though allowed regions of neutrino parameters overlap, the values of $δm^2$ and the mixing angle $θ_{12}$ at the $χ^2$ minima are different. We show that a non-zero, but small value of the angle $θ_{13}$ can account for this behavior. From the joint analysis of solar neutrino and KamLAND data we find the best fit value of $\sin^2 2 θ_{13} = 0.01 ^{-0.01}_{+0.09}$.
We show that seesaw models based on flavor symmetries (such as A_4 and Z_7 X Z_3) which produce exact tribimaximal neutrino mixing, also imply a vanishing leptogenesis asymmetry. We show that higher order symmetry breaking corrections in these models can give a non-zero leptogenesis asymmetry and generically also give deviations from tribimaximal mixing and a non-zero theta13 >~ 10^(-2)
A forthcoming experiment of low-energy elastic electron proton scattering at the new MESA facility in Mainz is planned to provide a high-precision measurement of the parity-violating polarisation asymmetry. This experiment is expected to lead to a precision determination of the weak mixing angle, competitive with Z-pole data. We discuss the challenges for theory to derive predictions with the required accuracy.
We provide a short summary of three-flavour neutrino oscillation parameters as determined from a global fit to 2008 data, and we comment on possible hints in favour of a non-zero value of the mixing angle theta_{13} found in arXiv:0806.2649. We do confirm a hint from solar + KamLAND data at about 1.5 sigma, which can be understood from the recent SNO CC/NC measurment. However, we show that a claimed hint from atmospheric data is much less robust. It depends on details of event rate calculations and treatment of theoretical uncertainties. We could identify two data points showing an 'excess' (a…
We discuss the neutrino oscillations, using texture zero mass matrices for the leptons, including radiative correction. The neutrino mixing angle theta_13 is calculated and agrees with the result of the new Daya Bay experiment.
We study the effects of breaking S3 symmetry in the neutrino mass matrix for the masses and mixing matrix of neutrinos. At zeroth order the model gives degenerate neutrino masses and accommodates tribimaximal mixing. We introduce perturbations in terms of a small and complex parameter. The perturbations are introduced in a manner such that the S3 symmetry is broken by its elements in the same representation. Successive perturbations introduce mass splitting, sizable non-zero reactor mixing angle and CP violation. This scheme of breaking S3 symmetry can reproduce a relatively large reactor mixi…
Based on Friedberg and Lee's geometric picture by which the tribimaximal Pontecorvo-Maki-Nakawaga-Sakata leptonic mixing matrix is constructed, namely, corresponding mixing angles correspond to the geometric angles among the sides of a cube. We suggest that the three realistic mixing angles, which slightly deviate from the values determined for the cube, are due to a viable deformation from the perfectly cubic shape. Taking the best-fitted results of $θ_{12}$ and $θ_{23}$ as inputs, we determine the central value of $\sin^22θ_{13}$ should be 0.0238, with a relatively large error tolerance; thi…
We discuss precision measurements of the leading atmospheric parameters at a standard neutrino factory. The oscillation of the muon and electron neutrinos (anti-neutrinos) to tau neutrinos (anti-neutrinos) adds to the muon events sample (both right sign and wrong sign) via leptonic decays of the taus produced through charge-current interactions in the detector. We focus on how this contribution affects a precision measurement of the atmospheric mixing parameters and the deviation of muon neutrino -- tau neutrino mixing from maximality.
We argue that gauge transformations with arbitrary fractional winding numbers should be allowed in a non-Abelian gauge theory. This eliminates the topological distinction between large and small gauge transformations. We prove that the states which satisfy the Gauss's law constraint are strictly invariant under gauge transformations, i.e. no phase shift occurs. In other words, the vacuum theta-angle is zero. Our observation does not resolve the strong CP problem.
We present a new class of models which produce zero theta (QCD} angle at the tree and one-loop level due to hermiticity of sub-blocks in the extended quark mass matrices. The structure can be maintained typically by non-abelian generation symmetry. Two examples are given for this class of solutions.
We discuss nuclear effects in the Paschos-Wolfenstein relationship in the context of extraction of the weak mixing angle. We point out that the neutron excess correction to the Paschos-Wolfenstein relationship for a neutron-rich target is negative and large on the scale of experimental errors of a recent NuTeV measurement. We found a larger neutron excess correction to the Paschos-Wolfenstein relationship for total cross sections than that discussed by the NuTeV collaboration. Phenomenological applications of this observation are discussed in the context of the NuTeV deviation. Uncertainties i…
We argue that a high precision measurement of the neutrino mixing parameter $θ_{13}$, within a three neutrino seesaw framework can throw important light on the question of whether the quarks and leptons unify into a single matter at high scales. Based on a number of examples, we conclude that a value of $θ_{13} \leq {\frac{Δm^2_{\odot}}{Δm^2_A}}\simeq 0.04$ would require at the minimum a pure leptonic interchange symmetry between $μ$ and $τ$ generations for its natural theoretical understanding and will disfavor a quark-lepton unification type theory such as those based on $SU(4)_c$ or SO(10) …
We study the effects that a non zero strong-CP-violating parameter theta would have on the deuteron and diproton binding energies and on the triple-alpha process. Both these systems exhibit fine tuning, so it is plausible that a small change in the nuclear force would produce catastrophic consequences. Such a nuclear force is here understood in the framework of an effective Lagrangian for pions and nucleons, and the strength of the interaction varies with theta. We find that the effects are not too dramatic.
In view of the latest T2K and MINOS neutrino oscillation data which hint at a relatively large theta_13, we perform a systematic study of the Majorana neutrino mass matrix M_nu with two independent texture zeros. We show that three neutrino masses (m_1, m_2, m_3) and three CP-violating phases (delta, rho, sigma) can fully be determined from two neutrino mass-squared differences (delta m^2, Delta m^2) and three flavor mixing angles (theta_12, theta_23, theta_13). We find that seven patterns of M_nu (i.e., A_{1,2}, B_{1,2,3,4} and C) are compatible with current experimental data at the 3-sigma l…
Solar and KamLAND data are in slight tension when interpreted in the standard two-flavor oscillations framework and this may be alleviated allowing for a non-zero value of the mixing angle theta_13. Here we show that, likewise, non-standard flavor-changing interactions (FCI), possibly intervening in the propagation of solar neutrinos, are equally able to alleviate this tension and therefore constitute a potential source of confusion in the determination of theta_13. By performing a full three-flavor analysis of solar and KamLAND data in presence of FCI we provide a quantitative description of …
We discuss the bounds on the cosmological lepton number from Big Bang Nucleosynthesis (BBN), in light of recent evidences for a large value of the neutrino mixing angle theta13. The largest asymmetries for electron and muon or tau neutrinos compatible with 4He and 2H primordial yields are computed versus the neutrino mass hierarchy and mixing angles. The flavour oscillation dynamics is traced till the beginning of BBN and neutrino distributions after decoupling are numerically computed. The latter contains in general, non thermal distortion due to the onset of flavour oscillations driven by so…
The lepton mixing angle theta_13, the only unknown angle in the standard three-flavor neutrino mixing scheme, is finally measured by the recent reactor and accelerator neutrino experiments. We perform a combined analysis of the data coming from T2K, MINOS, Double Chooz, Daya Bay and RENO experiments and find sin^2 2theta_13 = 0.096 \pm 0.013 (\pm 0.040) at 1 sigma (3 sigma) CL and that the hypothesis theta_13 = 0 is now rejected at a significance level of 7.7 sigma. We also discuss the near future expectation on the precision of the theta_13 determination by using expected data from these ongo…
In a previous paper [Phys. Rev. D 83, 113013 (2011)] we have shown that the solar sector data (solar and KamLAND) are sensitive to the parameter theta_14, encoding the admixture of the electron neutrino with a fourth (essentially) sterile mass eigenstate. In that work we evidenced that such data prefer a non-zero value of theta_14 and that such a preference is completely degenerate with that of non-zero theta_13. In this report we show how the evidence of theta_13 > 0, recently emerged from global neutrino data analyses, lifts such a degeneracy and disfavors the case of sterile neutrino mixing…
The scalar top discovery potential has been studied for the TESLA project with a full-statistics background simulation at sqrt(s)=500 GeV and L=500 fb-1. The beam polarization is very important to measure the scalar top mixing angle and to determine its mass. The latest estimation of the beam polarization parameters is applied. This study includes e+ polarization, which improves the sensitivity. For a 180 GeV scalar top at minimum production cross section, we obtain Delta(m)=0.8 GeV and Delta(cos(Theta))=0.008 in the neutralino channel, and Delta(m)=0.5 GeV and Delta(cos(Theta))=0.004 in the c…
We consider QED on a two-dimensional Euclidean torus with $f$ flavors of massless fermions and flavor-dependent chemical potentials. The dependence of the partition function on the chemical potentials is reduced to a $(2f-2)$-dimensional theta function. At zero temperature, the system can exist in an infinite number of phases characterized by certain values of traceless number densities and separated by first-order phase transitions. Furthermore, there exist many points in the $(f-1)$-dimensional space of traceless chemical potentials where two or three phases can coexist for $f=3$ and two, th…
We perform a systematic study of the modifications to the QCD vacuum energy density $ε_{vac}$ in the zero-temperature case ($T=0$) caused by a small, but non-zero, value of the parameter $θ$, using different effective Lagrangian models which include the flavour-singlet meson field and implement the $U(1)$ axial anomaly of the fundamental theory. In particular, we derive the expressions for the topological susceptibility $χ$ and for the second cumulant $c_4$ starting from the $θ$ dependence of $ε_{vac}(θ)$ in the various models that we have considered. Moreover, we evaluate numerically our resu…
To realize the condition of sin^2(2theta_{12})>>sin^2(theta_{13}), we find constraints on flavor neutrino masses M_{ij} (ij=e,μ,τ): C1) c_{23}^2 M_{μμ} + s_{23}^2 M_{ττ} \approx 2 s_{23} c_{23}M_{μτ} + M_{ee} and/or C2) |c_{23}M_{eμ} -s_{23}M_{eτ}|>> |s_{23}M_{eμ} +c_{23}M_{eτ}|, where c_{23}=cos(theta_{23}) (s_{23}=sin(theta_{23})) and theta_{12}, theta_{13} and theta_{23} are the mixing angles for three flavor neutrinos. The applicability of C1) and C2) is examined in models with one massless neutrino and two massive neutrinos suggested by \det(M)=0, where M is a mass matrix constructed from…
The residual Z^s_2(k) and bar Z^s_2(k) symmetries induce a direct and unique phenomenological relation with theta_x (= theta_13) expressed in terms of the other two mixing angles, theta_s (= theta_12) and theta_a (= theta_23), and the Dirac CP phase delta_D. Z^s_2(k) predicts a theta_x probability distribution centered around 3^o ~ 6^o with an uncertainty of 2^o to 4^o while those from bar Z^s_2(k) are approximately a factor of two larger. Either result fits the T2K, MINOS and Double CHOOZ measurements. Alternately a prediction for the Dirac CP phase delta_D results in a peak at +-74^o (+-106^…
Keeping in mind the possibility of large theta(13), which will be soon explored by reactor and accelerator experiments, I formulate a perturbation theory of neutrino oscillation under the ansatz, sin^2(theta_{13}) \simeq Delta m^2_{21}/Δm^2_{31} \simeq 0.03, which is comparable to the Chooz limit. Under the framework, I derive the perturbative formula of the nu_{e} appearance probability valid to order ε^2 in which effects of arbitrary matter density profile is taken into account. I use the formula to analyze problem of possible obstruction to detecting lepton CP violation by effects of asymme…
We study the impact of very light sterile neutrinos (Delta m^2_new around 1 to 10 times 10^(-2) eV^2, sin^2 2theta_new<10^(-1)) on upcoming theta_13-driven reactor antineutrino experiments like Double-CHOOZ and Daya Bay. Oscillations driven by these vales of Delta m^2_new affect data in the near and far detectors differently and hence potentially modify the capability of these experimental setups to constrain and measure sin^2 2theta_13. We find that the hypothesis theta_new different from zero negatively impacts one's ability to either place an upper bound on sin^2 2theta_13 in the advent of …
If the lepton mixing angle theta_{23} is not maximal, there arises a problem of ambiguity in determining theta_{23} due to the existence of two degenerate solutions, one in the first and the other in the second octant. We discuss an experimental strategy for resolving the theta_{23} octant degeneracy by combining reactor measurement of theta_{13} with accelerator nu_{mu} disappearance and nu_{e} appearance experiments. The robustness of the theta_{23} degeneracy and the difficulty in lifting it only by accelerator experiments with conventional nu_{mu} (and nu_{mu}-bar) beam are demonstrated by…
The leptonic mixing angle theta_13 is currently a high-priority topic in the field of neutrino physics, with five experiments under way, searching for neutrino oscillations induced by this angle. We review the phenomenology of theta_13 and discuss the information from present global oscillation data. A description of the upcoming reactor and accelerator experiments searching for a non-zero value of theta_13 is given, and we evaluate the sensitivity reach within the next few years.
We consider chiral perturbation theory (ChPT) with a non-zero theta term. Due to the CP violating term, the vacuum of chiral fields is shifted to a non-trivial element on the SU(N_f) group manifold. The CP violation also provides mixing of different CP eigenstates, between scalar and pseudoscalar, or vector and axialvector operators. We investigate upto O(theta^2) effects on the mesonic two point correlators of ChPT to the one-loop order. We also address the effects of fixing topology, by using saddle point integration in the Fourier transform with respect to theta.
Theta vacuum effects on the QCD phase structure in the μ-T plane are studied by using the Polyakov-loop extended Nambu-Jona-Lasinio model and its extension, where μis the quark chemical potential and T is temperature, respectively. As the parameter θof the theta vacuum increases, the chiral transition becomes stronger. For large θ, it eventually becomes first order even at zero μ.
We examine accuracy of theta_{23} determination in future long-baseline (LBL) nu_{mu} disappearance experiments in the three-flavor mixing scheme of neutrinos. Despite that the error of sin^2{2theta_{23}} is indeed a few % level at around the maximal mixing, we show that the error of physics variable s^2_{23} is large, delta(s^2_{23})/s^2_{23} \simeq 10-20%, depending upon regions of theta_{23}. The errors are severely affected by the octant degeneracy of theta_{23}, and delta(s^2_{23}) is largely amplified by the Jacobian factor relating these two variables in a region near to the maximal mix…
We suggest that the topological susceptibility in gluodynamics can be found in terms of the gluon condensate using renormalizability and heavy fermion representation of the anomaly. Analogous relations can be also obtained for other zero momentum correlation functions involving the topological density operator. Using these relations, we find the theta dependence of the condensates <GG>, <G \tilde{G}> and of the partition function for small theta and an arbitrary number of colors.
We discuss, in the context of precision measurement of Delta m^2_{31} and theta_{13}, physics capabilities enabled by the recoilless resonant absorption of monochromatic antineutrino beam enhanced by the Mössbauer effect recently proposed by Raghavan. Under the assumption of small relative systematic error of a few tenth of percent level between measurement at different detector locations, we give analytical and numerical estimates of the sensitivities to Delta m^2_{31} and sin^2 2theta_{13}. The accuracies of determination of them are enormous; The fractional uncertainty in Delta m^2_{31} ach…
We investigate theta-vacuum effects on the QCD phase diagram for the realistic 2+1 flavor system, using the three-flavor Polyakov-extended Nambu-Jona-Lasinio (PNJL) model and the entanglement PNJL model as an extension of the PNJL model. The theta-vacuum effects make the chiral transition sharper. For large theta-vacuum angle the chiral transition becomes first order even if the quark number chemical potential is zero, when the entanglement coupling between the chiral condensate and the Polyakov loop is taken into account. We finally propose a way of circumventing the sign problem on lattice Q…
Neutrinos exhibit an interesting phenomenon called 'neutrino oscillation', in which a neutrino changes its flavor after traveling some flight length. Many experiments measured the mixing angles and mass differences, but the angle $θ_{13}$ had been unmeasured due to its smallness compared to others. During 2011 and 2012, series of new-generation neutrino experiments reported positive results in $θ_{13}$ search, and its value has been determined to be just below the previous upper limit. The non-zero result of $θ_{13}$ is a very good news for future of neutrino physics, since it opens a possibil…
We investigate a possible nuclear correction to the NuTeV measurement of the weak-mixing angle sin^2 theta_W. In particular, a nuclear modification difference between u_v and d_v distributions contributes to the NuTeV measurement with the iron target. First, the modification differenceis determined by a chi^2 analysis so as to reproduce nuclear data on the structure function F_2 and Drell-Yan processes. Then, taking the NuTeV kinematics into account, we calculate a contribution to the sin^2 theta_W determination. In addition, its uncertainty is estimated by the Hessian method. Although the unc…
New generation of three reactor neutrino experiments have made definitive measurements of the smallest neutrino mixing angle theta13 in 2012, based on the disappearance of electron antineutrinos. More precise measurements of the mixing angle have been made as well as the squared mass difference between electron neutrinos. A rather large value of theta13 has opened a new window to find the CP violation phase and to determine the neutrino mass hierarchy. Future reactor experiments, JUNO and RENO50, are proposed to determine the neutrino mass hierarchy and to make highly precise measurements of t…
We discuss reactor measurement of θ_{12} which has a potential of reaching the ultimate sensitivity which surpasses all the methods so far proposed. The key is to place a detector at an appropriate baseline distance from the reactor neutrino source to have an oscillation maximum at around a peak energy of the event spectrum in the absence of oscillation. By a detailed statistical analysis the optimal distance is estimated to be \simeq (50-70) km x [8 x 10^{-5} eV^2/Δm^2_{21}], which is determined by maximizing the oscillation effect in the event number distribution and minimizing geo-neutrino …
We examine the prospects of probing nonstandard interactions (NSI) of neutrinos in the e-tau sector with upcoming long-baseline nu_mu -> nu_e oscillation experiments. First conjectured decades ago, neutrino NSI remain of great interest, especially in light of the recent 8B solar neutrino measurements by SNO, Super-Kamiokande, and Borexino. We observe that the recent discovery of large theta_13 implies that long-baseline experiments have considerable NSI sensitivity, thanks to the interference of the standard and new physics conversion amplitudes. In particular, in some parts of NSI parameter s…
We consider QCD at Theta ~ Pi with two, one and zero light flavours Nf, using the Di Vecchia-Veneziano-Witten effective lagrangian. For Nf=2, we show that CP is spontaneously broken at Theta = Pi for finite quark mass splittings, z= Md/Mu \not= 1. In the z-Theta plane, there is a line of first order transitions at Theta = Pi with two critical endpoints, z1* < z < z2*. We compute the tension of the domain walls relating the two CP violating vacua. For Mu=Md the tension of the family of equivalent domain walls agrees with the expression derived by Smilga from chiral perturbation theory at next-t…
We prove the analyticity of the finite volume QCD partition function for complex values of the theta-vacuum parameter. The absence of singularities different from Lee-Yang zeros only permits ^ cusp singularities in the vacuum energy density and never v cusps. This fact together with the Vafa-Witten diamagnetic inequality implies the vanishing of the density of Lee-Yang zeros at theta=0 and has an important consequence: the absence of a first order phase transition at theta=0. The result provides a key missing link in the Vafa-Witten proof of parity symmetry conservation in vector-like gauge th…
We perform a global analysis of neutrino oscillation data, including high-precision measurements of the neutrino mixing angle theta_13 at reactor experiments, which have confirmed previous indications in favor of theta_13>0. Recent data presented at the Neutrino 2012 Conference are also included. We focus on the correlations between theta_13 and the mixing angle theta_23, as well as between theta_13 and the neutrino CP-violation phase delta. We find interesting indications for theta_23< pi/4 and possible hints for delta ~ pi, with no significant difference between normal and inverted mass hier…
In this work, extending a previous study at zero temperature ($T=0$), we perform a systematic study of the modifications to the QCD vacuum energy density $ε_{vac}$ in the finite-temperature case, above the chiral transition at $T_c$, caused by a nonzero value of the parameter $θ$, using two different effective Lagrangian models which implement the $U(1)$ axial anomaly of the fundamental theory and which are both well defined also above $T_c$. In particular, we derive (and critically compare) the expressions for the topological susceptibility $χ$ and for the second cumulant $c_4$ starting from …
