Search

We present analytic expressions for three-flavor neutrino oscillations in presence of invisible neutrino decay and matter effects. Using the well-known Cayley-Hamilton formalism, the leading-order terms are derived for oscillation probabilities in all major channels assuming the neutrino mass eigenstate $\nu_3$ to decay into sterile neutrinos. Our work extends and complements previous studies utilizing the Cayley-Hamilton theorem, providing the series expansions for $\nu_e \rightarrow \nu_e$, $\nu_e \rightarrow \nu_\mu$, $\nu_e \rightarrow \nu_\tau$, $\nu_\mu \rightarrow \nu_\mu$, $\nu_\mu \rightarrow \nu_\tau$ and $\nu_\tau \rightarrow \nu_\tau$. The accuracy of the analytical formulas is investigated by comparing the results with numerically calculated probabilities. We also comment on the implications on unitarity violation., Comment: 18 pages, 6 figures and 1 table. Comments are welcome!

Proton decay is a hypothetical form of particle decay in which protons are assumed to decay into lighter particles. This form of decay has yet to be detected. In this contribution to the proceedings of Neutrino 2022, we review the current status of proton decay, covering both experimental results and theoretical models, including their predictions., Comment: 8 pages, 7 figures, REVTeX 4.2. Invited plenary talk presented at the XXXth International Conference on Neutrino Physics and Astrophysics (Neutrino 2022), (virtual) Seoul, Republic of Korea, June 4, 2022. Final version published in Nucl. Phys. B

We investigate matching conditions and threshold corrections between full and effective theories based on the type I seesaw mechanism. In general, using an intuitive Feynman diagrammatical approach, we compute the amplitudes before and after integrating out heavy right-handed neutrinos at the matching scale. In particular, we derive the one-loop matching conditions between the full and the effective theories. The matching conditions of the parameters are influenced by one-loop corrections to the corresponding vertices as well as wave function corrections for the Higgs and the lepton fields. Our results are comparable to earlier results based on a functional approach., Comment: 38 pages, 19 figures. Final version published in Nucl. Phys. B

We investigate the options for imposing flavor symmetries on a minimal renormalizable non-supersymmetric $\mathrm{SU}(5)$ grand unified theory, without introducing additional flavor-related fields. Such symmetries reduce the number of free parameters in the model and therefore lead to more predictive models. We consider the Yukawa sector of the Lagrangian, and search for all possible flavor symmetries. As a result, we find 25 distinct realistic flavor symmetry cases, with $\mathbb{Z}_2$, $\mathbb{Z}_3$, $\mathbb{Z}_4$, and $\mathrm{U}(1)$ symmetries, and no non-Abelian cases., Comment: 20 pages. Final version published in JHEP

We consider a class of $\text{SO}(10)$ models with flavor symmetries in the Yukawa sector and investigate their viability by performing numerical fits to the fermion masses and mixing parameters. The fitting procedure involves a top-down approach in which we solve the renormalization group equations from the scale of grand unification down to the electroweak scale. This allows the intermediate scale right-handed neutrinos and scalar triplet, involved in the type I and II seesaw mechanisms, to be integrated out at their corresponding mass scales, leading to a correct renormalization group running. The result is that, of the 14 models considered, only two are able to fit the known data well. Both these two models correspond to $\mathbb{Z}_2$ symmetries. In addition to being able to fit the fermion masses and mixing parameters, they provide predictions for the sum of light neutrino masses and the effective neutrinoless double beta decay mass parameter, which are both within current observational bounds., Comment: 19 pages, 4 tables. Final version published in JHEP

We investigate the mass spectra of exotic hadrons known as hexaquarks in the form of dibaryons. We use a phenomenological model based on an extended version of the G\"ursey-Radicati mass formula for hadrons to include non-charmed baryons, charmed baryons, and non-strange dibaryons to be able to predict masses of potential dibaryon states. We perform six numerical fits of this model to input data for three different sets of masses of baryons and dibaryons. We find that the model can fit some of the data sets well, especially the sets including charmed baryons and non-strange dibaryons, and observe that the predicted mass of one of the dibaryons is close to the measured mass of the observed hexaquark candidate $d^*(2380)$ reported by the WASA-at-COSY experiment. The predicted mass of the deuteron is slightly larger than its measured mass. Finally, for the data sets including charmed baryon and non-strange dibaryon masses, we find that the predicted masses of potential dibaryon states are all in the range from 1900 MeV to 3700 MeV., Comment: 6 pages, 3 figures. Final version published in Nucl. Phys. B

We explore invisible neutrino decay in which a heavy active neutrino state decays into a light sterile neutrino state and present a comparative analysis of two baseline options, $540~$km and $360~$km, for the ESSnuSB experimental setup. Our analysis shows that ESSnuSB can put a bound on the decay parameter $\tau_3/m_3 = 2.64~(1.68) \times 10^{-11}~$s/eV for the baseline option of $360~(540)~$km at $3 \sigma$. The expected bound obtained for $360~$km is slightly better than the corresponding one of DUNE for a charged current (CC) analysis. Furthermore, we show that the capability of ESSnuSB to discover decay, and to measure the decay parameter precisely, is better for the baseline option of $540~$km than that of $360~$km. Regarding effects of decay in $\delta_{\rm CP}$ measurements, we find that in general the CP violation discovery potential is better in the presence of decay. The change in CP precision is significant if one assumes decay in data but no decay in theory., Comment: 22 pages, 10 figures, 4 tables, Version accepted for publication in JHEP

We derive the threshold corrections in $\mathrm{SO}(10)$ grand unified models with the intermediate symmetry being flipped $\mathrm{SU}(5)\times\mathrm{U}(1)$ or $\mathrm{SU}(3)\times\mathrm{SU}(2)\times\mathrm{U}(1)\times\mathrm{U}(1)$, with the masses of the scalar fields set by the survival hypothesis. These models do not achieve gauge coupling unification if the matching conditions do not take threshold corrections into account. We present results showing the required size of threshold corrections for any value of the intermediate and unification scales. In particular, our results demonstrate that both of these models are disfavored since they require large threshold corrections to allow for unification with a predicted proton lifetime above current experimental bounds., Comment: 6 pages, 5 figures. Final version published in Eur. Phys. J. C

We investigate a nonrelativistic model of tetraquarks, which are assumed to be compact and to consist of diquark-antidiquark pairs. We fit, for the first time, basically all currently known values for the measured masses of 45 mesons, including both charmed and bottom mesons, to the model and predict masses of tetraquarks as well as diquarks. In particular, we find masses of four axial-vector diquarks, i.e., $qc$, $cc$, $qb$, and $bb$, where $q = u,d$, and 24 ground-state tetraquarks, including both heavy-light tetraquarks ($qc\overline{qc}$ and $qb\overline{qb}$) and heavy tetraquarks ($cc\overline{cc}$ and $bb\overline{bb}$). In general, our results for the masses of $qb\overline{qb}$, $cc\overline{cc}$, and $bb\overline{bb}$ are largely comparable with other reported results, whereas our results for the masses of $qc\overline{qc}$ are slightly larger than what has been found earlier. Finally, we identify some of the obtained predictions for masses of tetraquarks with masses of experimental tetraquark candidates, and especially, we find that $\psi(4660)$, $Z_b(10610)$, and $Z_b(10650)$ could be described by the model., Comment: 12 pages, 1 figure. Final version published in Phys. Rev. D

In the presence of Lindblad decoherence, i.e. dissipative effects in an open quantum system due to interaction with an environment, we examine the transition probabilities between the eigenstates in the two-level quantum system described by non-Hermitian Hamiltonians with the Lindblad equation, for which the parity-time-reversal (PT) symmetry is conserved. First, the density matrix formalism for PT-symmetric non-Hermitian Hamiltonian systems is developed. It is shown that the Lindblad operators $L^{}_j$ are pseudo-Hermitian, namely, $\eta L^{}_j \eta^{-1} = L^\dagger_j$ with $\eta$ being a linear and positive-definite metric, and respect the PT symmetry as well. We demonstrate that the generalized density matrix $\rho^{}_{\rm G}(t) \equiv \rho(t) \eta$, instead of the normalized density matrix $\rho^{}_{\rm N}(t) \equiv \rho(t)/{\rm tr}\left[\rho(t)\right]$, should be implemented for the calculation of the transition probabilities in accordance with the linearity requirement. Second, the density matrix formalism is used to derive the transition probabilities in general cases of PT-symmetric non-Hermitian Hamiltonians. In some concrete examples, we calculate compact analytical formulas for the transition probabilities and explore their main features with numerical illustrations. We also make a comparison between our present results and our previous ones using state vectors in the absence of Lindblad decoherence., Comment: 36 pages, 10 figures. Published in Phys. Rev. A

Non-Abelian discrete symmetries provide an interesting opportunity to address the flavor puzzle in the lepton sector. However, the number of currently viable models based on such symmetries is rather large. High-precision measurements of the leptonic mixing parameters by future neutrino experiments, including ESSnuSB, T2HK, DUNE, and JUNO, will be crucial to test such models. We show that the complementarity among these experiments offers a powerful tool for narrowing down this broad class of lepton flavor models., Comment: 7 pages, 3 figures, 1 table; several comments and references added; matches version published in PRD

We review and investigate lepton flavor models, stemming from discrete non-Abelian flavor symmetries, described by one or two free model parameters. First, we confront eleven one- and seven two-parameter models with current results on leptonic mixing angles from global fits to neutrino oscillation data. We find that five of the one- and five of the two-parameter models survive the confrontation test at $3\sigma$. Second, we investigate how these ten one- and two-parameter lepton flavor models may be discriminated at the proposed ESSnuSB experiment in Sweden. We show that the three one-parameter models that predict $\sin\delta_{\rm CP}=0$ can be distinguished from those two that predict $|\sin\delta_{\rm CP}|=1$ by at least $7\sigma$. Finally, we find that three of the five one-parameter models can be excluded by at least $5\sigma$ and two of the one-parameter as well as at most two of the five two-parameter models can be excluded by at least $3\sigma$ with ESSnuSB if the true values of the leptonic mixing parameters remain close to the present best-fit values., Comment: 38 pages, 12 figures, 10 tables; several comments added; typos corrected; matches version published in JHEP

We investigate the transition probabilities for the "flavor" eigenstates in the two-level quantum system, which is described by a non-Hermitian Hamiltonian with the parity and time-reversal (PT) symmetry. Particularly, we concentrate on the so-called PT-broken phase, where two eigenvalues of the non-Hermitian Hamiltonian turn out to be a complex conjugate pair. In this case, we find that the transition probabilities will be unbounded in the limit of infinite time $t \to +\infty$. However, after performing a connection between a non-Hermitian system, which exhibits passive PT-symmetry and global decay, and the neutral-meson system in particle physics, we observe that the diverging behavior of the transition probabilities is actually applicable to the gauge-transformed neutral-meson states, whereas the transition probabilities for physical states are exponentially suppressed by the global decay. We also present a brief review on the situation at the so-called exceptional point, where both the eigenvalues and eigenvectors of the Hamiltonian coalesce., Comment: 21 pages, 1 figure. Final version published in J. Math. Phys

We present a comprehensive analysis in the 3+1 active-sterile neutrino oscillation scenario for the sensitivity of the ESSnuSB experiment in the presence of light sterile neutrinos assuming both a far (FD) and a near (ND) detector. Our analysis show that when the ND is included, the results are significantly different compared to the ones obtained with the FD only. We find that the capability of ESSnuSB to constrain the sterile mixing parameters is $\sin^22\theta_{\mu e} \sim 10^{-4}$ for $\Delta m^2 = 1$ eV$^2$ if the ND is included and it becomes $\sin^22\theta_{\mu e} \sim 10^{-2}$ without the ND. Furthermore, we show that the sensitivity can go down to $\sin^22\theta_{\mu e} \sim 10^{-3}$ for the most conservative choice of the systematics on the ND. Comparing the sensitivity with T2HK, T2HKK, and DUNE by considering the FD only, we find that the sensitivity of ESSnuSB is smaller for most of the parameter space. Studying the CP violation sensitivity, we find that if the ND is included, it can be larger in the 3+1 scenario than in the standard one. However, if the ND is not included, the sensitivity is smaller compared to the one in the standard scenario. We also find that the CP violation sensitivity due to $\delta_{13}$ is larger compared to the one induced by $\delta_{24}$. The sensitivities are slightly better for the dominant neutrino running ratio of ESSnuSB., Comment: 17 pages, 6 figures, 2 tables, Final version published in JHEP

Despite the successes of the Standard Model of particle physics, it is known to suffer from a number of deficiencies. Several of these can be addressed within non-supersymmetric theories of grand unification based on $\mathrm{SO}(10)$. However, achieving gauge coupling unification in such theories is known to require additional physics below the unification scale, such as symmetry breaking in multiple steps. Many such models are disfavored due to bounds on the proton lifetime. Corrections arising from threshold effects can, however, modify these conclusions. We analyze all seven relevant breaking chains with one intermediate symmetry breaking scale, assuming the "survival hypothesis" for the scalar masses. Two are allowed by proton lifetime and two are disfavored by a failure to unify the gauge couplings. The remaining three unify at a too low scale, but can be salvaged by various amounts of threshold corrections. We parametrize this and thereby rank the models by the size of the threshold corrections required to save them., Comment: 37 pages, 3 figures, 8 tables. Final version published in Eur. Phys. J. C

We investigate the mass spectra of exotic hadrons known as pentaquarks. We extend a simple phenomenological model based on the G\"ursey-Radicati mass formula for hadrons to include both charmed and bottom baryons as well as to be able to predict masses of pentaquark states including both charm and bottom quark-antiquark pairs. In particular, we perform numerical fits of this model, which includes seven free parameters, to masses of 21 baryons. We find that the model can be well fitted to the experimental values of the baryon masses and observe that the predicted value of about 4400 MeV for the mass of the pentaquark $P_c(4380)^+$ lies within the experimental range reported by the LHCb experiment. In addition, the predicted value of about 4500 MeV for the mass of the pentaquark $P_c(4450)^+$ is close to the experimental value. Finally, in the future, other predicted values for masses of additional pentaquarks could be shown to agree with upcoming experimental results., Comment: 6 pages, 2 figures. Final version published in Phys. Lett. B

In this paper, we perform a comparative analysis between the future proposed long-baseline experiments ESSnuSB and T2HK in measuring the leptonic CP phase $\delta_{\rm CP}$. In particular, we study the effect of the neutrino mass ordering degeneracy and the leptonic mixing angle $\theta_{23}$ octant degeneracy in the measurement of leptonic CP violation and precision for both experiments. Since the ESSnuSB (T2HK) experiment probes the second (first) oscillation maximum to study neutrino oscillations, the effect of these degeneracies are significantly different in both experiments. Our main conclusion is that for the ESSnuSB experiment, the information on the neutrino mass ordering does not play a major role in the determination of $\delta_{\rm CP}$, which is not the case for the T2HK experiment. However, the information on the true octant compromises the CP sensitivity of the ESSnuSB experiment as compared to T2HK if $\theta_{23}$ lies in the lower octant. These conclusions are true for both the 540~km and 360~km baseline options for the ESSnuSB experiment. In addition, we investigate the effect of different running times in neutrino and antineutrino modes and the effect of $\theta_{23}$ precision in measuring $\delta_{\rm CP}$., Comment: 10 pages, 9 figures. Final version published in Mod. Phys. Lett. A

We investigate how to define in a consistent way the probabilities of the transitions between the "flavor" states of the two-level quantum system, which is described by a non-Hermitian but parity and time-reversal (PT) symmetric Hamiltonian. Explicit calculations are carried out to demonstrate the conservation of probability if a proper definition of the final state is adopted. Finally, this formalism is applied to two-flavor neutrino oscillations $\nu^{}_\mu \to \nu^{}_\mu$ and $\nu^{}_\mu \to \nu^{}_\tau$ in vacuum, where the exact PT symmetry requires the vacuum mixing angle to be maximal, which is compatible with current neutrino oscillation experiments. A possible generalization to the three-flavor case is briefly discussed., Comment: 23 pages, 1 figure. Final version published in J. Math. Phys

We consider numerical fits to non-supersymmetric $\mathrm{SO}(10)$-based models in which neutrino mass is generated by the type-I or type-II seesaw mechanism or a combination of both. The fits are performed with a sophisticated top-down procedure, taking into account the renormalization group equations of the gauge and Yukawa couplings, integrating out relevant degrees of freedom at their corresponding mass scales, and using recent data for the Standard Model observables. We find acceptable fits for normal neutrino mass ordering only and with neutrino mass generated by either type-I seesaw only or a combination of types I and II seesaw in which type-I seesaw is dominant. Furthermore, we find predictions from the best fit regarding the small neutrino masses, the effective neutrinoless double beta decay mass, and the leptonic CP-violating phase. Finally, we show that the fits are rather insensitive to the chosen value of the unification scale., Comment: 22 pages, 3 figures, 3 tables. Final version published in JHEP

We present a minimal non-supersymmetric SO(10) GUT breaking directly to the Standard Model gauge group. Precise gauge coupling unification is achieved due to the presence of two color-octet scalars, one of which is accessible to LHC searches. Proton lifetime is predicted to be below $4.5\times 10^{34}$ years, which is within the projected five-year sensitivity of the proposed Hyper-Kamiokande experiment. We find that the Standard Model observables are reproduced to a reasonable accuracy in a numerical fit, which also predicts the unknown neutrino parameters. Finally, the two scalar representations stabilize the electroweak vacuum and the dark matter is comprised of axions., Comment: 7 pages, 3 figures. Final version published in Phys. Lett. B. Corrected units in Eq. (13)

This document summarizes the conclusions of the Neutrino Town Meeting held at CERN in October 2018 to review the neutrino field at large with the aim of defining a strategy for accelerator-based neutrino physics in Europe. The importance of the field across its many complementary components is stressed. Recommendations are presented regarding the accelerator based neutrino physics, pertinent to the European Strategy for Particle Physics. We address in particular i) the role of CERN and its neutrino platform, ii) the importance of ancillary neutrino cross-section experiments, and iii) the capability of fixed target experiments as well as present and future high energy colliders to search for the possible manifestations of neutrino mass generation mechanisms., Comment: 10+6 pages; Summary Document of the European Neutrino Town Meeting, Oct 22-24 at CERN; editors: Alain Blondel, Albert De Roeck, Joachim Kopp; v2: references added

We investigate photon signatures of general decaying dark-matter particles in halos of primordial black holes. We derive the halo-profile density and the total decay rate for these combined dark-matter scenarios. For the case of axion-like particles of masses below $\mathcal{O}( 1 )\,$keV, we find strong bounds on the decay constant which are several orders of magnitude stronger than the strongest existing bounds, for all halo masses above $\mathcal{O}( 10^{-5} )$ solar masses. Using future X-ray measurements, it will be possible to push these bounds on such combined dark-matter scenarios even further., Comment: 5 pages, 3 figures; v2: revised in order to match published version

We investigate the complete renormalization group running of fermion observables in two different realistic non-supersymmetric models based on the gauge group $\textrm{SO}(10)$ with intermediate symmetry breaking for both normal and inverted neutrino mass orderings. Contrary to results of previous works, we find that the model with the more minimal Yukawa sector of the Lagrangian fails to reproduce the measured values of observables at the electroweak scale, whereas the model with the more extended Yukawa sector can do so if the neutrino masses have normal ordering. The difficulty in finding acceptable fits to measured data is a result of the added complexity from the effect of an intermediate symmetry breaking as well as tension in the value of the leptonic mixing angle $\theta^\ell_{23}$., Comment: 15 pages, 3 figures, 4 tables. Final version published in JHEP

We derive constraints on mixed dark-matter scenarios consisting of primordial black holes (PBHs) and weakly interacting massive particles (WIMPs). In these scenarios, we expect a density spike of the WIMPs that are gravitationally bound to the PBHs, which results in an enhanced annihilation rate and increased indirect detection prospects. We show that such scenarios provide strong constraints on the allowed fraction of PBHs that constitutes the dark matter, depending on the WIMP mass $m_{\chi}$ and the velocity-averaged annihilation cross-section $\langle \sigma v \rangle$. For the standard scenario with $m_{\chi} = 100\,{\rm GeV}$ and $\langle \sigma v \rangle = 3 \times 10^{-26}\,{\rm cm}^{3} / {\rm s}$, we derive bounds that are stronger than all existing bounds for PBHs with masses $10^{-12}\,M_{\odot} \lesssim M_{\rm BH} \lesssim 10^{4}\,M_{\odot}$, where $M_{\odot}$ is the solar mass, and mostly so by several orders of magnitude., Comment: 17 pages, 4 figures; v2: minor changes to match published version

We investigate possible interactions between neutrinos and massive scalar bosons via $g^{}_{\phi} \overline{\nu} \nu \phi$ (or massive vector bosons via $g^{}_V \overline{\nu} \gamma^\mu \nu V^{}_\mu$) and explore the allowed parameter space of the coupling constant $g^{}_{\phi}$ (or $g^{}_V$) and the scalar (or vector) boson mass $m^{}_\phi$ (or $m^{}_V$) by requiring that these secret neutrino interactions (SNIs) should not spoil the success of Big Bang nucleosynthesis (BBN). Incorporating the SNIs into the evolution of the early Universe in the BBN era, we numerically solve the Boltzmann equations and compare the predictions for the abundances of light elements with observations. It turns out that the constraint on $g^{}_{\phi}$ and $m^{}_\phi$ in the scalar-boson case is rather weak, due to a small number of degrees of freedom. However, in the vector-boson case, the most stringent bound on the coupling $g^{}_V \lesssim 6\times 10^{-10}$ at $95~\%$ confidence level is obtained for $m^{}_V \simeq 1~{\rm MeV}$, while the bound becomes much weaker $g^{}_V \lesssim 8\times 10^{-6}$ for smaller masses $m^{}_V \lesssim 10^{-4}~{\rm MeV}$. Moreover, we discuss in some detail how the SNIs affect the cosmological evolution and the abundances of the lightest elements., Comment: 18 pages, 5 figures

We investigate compact halos of sterile-neutrino dark matter and examine observable signatures with respect to neutrino and photon emission. Primarily, we consider two cases: primordial black-hole halos and ultra-compact mini-halos. In both cases, we find that there exists a broad range of possible parameter choices such that detection in the near future with X-ray and gamma-ray telescopes might be well possible. In fact, for energies above $10\,{\rm TeV}$, the neutrino telescope IceCube would be a splendid detection machine for such macroscopic dark-matter candidates., Comment: 6 pages, 2 figures, 2 tables; v2: minor modifications to match published version

We study the general Zee model, which includes an extra Higgs scalar doublet and a new singly-charged scalar singlet. Neutrino masses are generated at one-loop level, and in order to describe leptonic mixing, both the Standard Model and the extra Higgs scalar doublets need to couple to leptons (in a type-III two-Higgs doublet model), which necessarily generates large lepton flavor violating signals, also in Higgs decays. Imposing all relevant phenomenological constraints and performing a full numerical scan of the parameter space, we find that both normal and inverted neutrino mass orderings can be fitted, although the latter is disfavored with respect to the former. In fact, inverted ordering can only be accommodated if $\theta_{23}$ turns out to be in the first octant. A branching ratio for $h \to \tau \mu$ of up to $10^{-2}$ is allowed, but it could be as low as $10^{-6}$. In addition, if future expected sensitivities of $\tau\to \mu\gamma$ are achieved, normal ordering can be almost completely tested. Also, $\mu e$ conversion is expected to probe large parts of the parameter space, excluding completely inverted ordering if no signal is observed. Furthermore, non-standard neutrino interactions are found to be smaller than $10^{-6}$, which is well below future experimental sensitivity. Finally, the results of our scan indicate that the masses of the additional scalars have to be below $2.5$ TeV, and typically they are lower than that and therefore within the reach of the LHC and future colliders., Comment: 45 pages, 12 figures, 7 tables. Final version published in JHEP

We investigate the renormalization group evolution of fermion masses, mixings and quartic scalar Higgs self-couplings in an ${\it extended}$ non-supersymmetric SO(10) model, where the Higgs sector contains the ${\bf 10}_{\rm H}$, ${\bf 120}_{\rm H}$, and ${\bf 126}_{\rm H}$ representations. The group SO(10) is spontaneously broken at the GUT scale to the Pati-Salam group and subsequently to the Standard Model (SM) at an intermediate scale $M_{\rm I}$. We explicitly take into account the effects of the change of gauge groups in the evolution. In particular, we derive the renormalization group equations for the different Yukawa couplings. We find that the computed physical fermion observables can be successfully matched to the experimental measured values at the electroweak scale. Using the same Yukawa couplings at the GUT scale, the measured values of the fermion observables cannot be reproduced with a SM-like evolution, leading to differences in the numerical values up to around 80 %. Furthermore, a similar evolution can be performed for a ${\it minimal}$ SO(10) model, where the Higgs sector consists of the ${\bf 10}_{\rm H}$ and ${\bf 126}_{\rm H}$ representations only, showing an equally good potential to describe the low-energy fermion observables. Finally, for both the extended and the minimal SO(10) models, we present predictions for the three Dirac and Majorana CP-violating phases as well as three effective neutrino mass parameters., Comment: 24 pages, 3 figures, 3 tables. Final version published in JHEP

We simultaneously investigate source, detector and matter non-standard neutrino interactions at the proposed DUNE experiment. Our analysis is performed using a Markov Chain Monte Carlo exploring the full parameter space. We find that the sensitivity of DUNE to the standard oscillation parameters is worsened due to the presence of non-standard neutrino interactions. In particular, there are degenerate solutions in the leptonic mixing angle $\theta_{23}$ and the Dirac CP-violating phase $\delta$. We also compute the expected sensitivities at DUNE to the non-standard interaction parameters. We find that the sensitivities to the matter non-standard interaction parameters are substantially stronger than the current bounds (up to a factor of about 15). Furthermore, we discuss correlations between the source/detector and matter non-standard interaction parameters and find a degenerate solution in $\theta_{23}$. Finally, we explore the effect of statistics on our results., Comment: 21 pages, 7 figures. Version accepted for publication in JHEP

We investigate the possibility of gauge coupling unification in various radiative neutrino mass models, which generate neutrino masses at one- and/or two-loop level. Renormalization group running of gauge couplings is performed analytically and numerically at one- and two-loop order, respectively. We study three different classes of neutrino mass models: (I) minimal ultraviolet completions of the dimension-7 $\Delta L=2$ operators which generate neutrino masses at one- and/or two-loop level without and with dark matter candidates, (II) models with dark matter which lead to neutrino masses at one-loop level and (III) models with particles in the adjoint representation of $\mathrm{SU}(3)$. In class (I), gauge couplings unify in a few models and adding dark matter amplifies the chances for unification. In class (II), about a quarter of the models admit gauge coupling unification. In class (III), none of the models leads to gauge coupling unification. Regarding the scale of unification, we find values between $10^{14}$ GeV and $10^{16}$ GeV for models belonging to class (I) without dark matter, whereas models in class (I) with dark matter as well as models of class (II) prefer values in the range $5 \cdot 10^{10}-5 \cdot 10^{14}$ GeV., Comment: 28 pages, 2 figures. Updated to match journal version

We introduce and develop a novel approach to extend the ordinary two-flavor neutrino oscillation formalism in matter using a non-Hermitian PT symmetric effective Hamiltonian. The condition of PT symmetry is weaker and less mathematical than that of hermicity, but more physical, and such an extension of the formalism can give rise to sub-leading effects in neutrino flavor transitions similar to the effects by so-called non-standard neutrino interactions. We derive the necessary conditions for the spectrum of the effective Hamiltonian to be real as well as the mappings between the fundamental and effective parameters. We find that the real spectrum of the effective Hamiltonian will depend on all new fundamental parameters introduced in the non-Hermitian PT symmetric extension of the usual neutrino oscillation formalism and that either i) the spectrum is exact and the effective leptonic mixing must always be maximal or ii) the spectrum is approximate and all new fundamental parameters must be small., Comment: 6 pages, 1 figure. Final version (author's post-print version) published in Europhysics Letters

We investigate source and detector non-standard neutrino interactions at the proposed ESS$\nu$SB experiment. We analyze the effect of non-standard physics at the probability level, the event-rate level and by a full computation of the ESS$\nu$SB setup. We find that the precision measurement of the leptonic mixing angle $\theta_{23}$ at ESS$\nu$SB is robust in the presence of non-standard interactions, whereas that of the leptonic CP-violating phase $\delta$ is worsened at most by a factor of two. We compute sensitivities to all the relevant source and decector non-standard interaction parameters and find that the sensitivities to the parameters $\varepsilon^s_{\mu e}$ and $\varepsilon^d_{\mu e}$ are comparable to the existing limits in a realistic scenario, while they improve by a factor of two in an optimistic scenario. Finally, we show that the absence of a near detector compromises the sensitivity of ESS$\nu$SB to non-standard interactions., Comment: 26 pages, 10 figures. Final version published in JHEP

Non-standard neutrino interactions (NSI) involved in neutrino propagation inside Earth matter could potentially alter atmospheric neutrino fluxes. In this work, we look at the impact of these NSI on the signal at the ICAL detector to be built at the India-based Neutrino Observatory (INO). We show how the sensitivity to the neutrino mass hierarchy of ICAL changes in the presence of NSI. The mass hierarchy sensitivity is shown to be rather sensitive to the NSI parameters $\epsilon_{e\mu}$ and $\epsilon_{e\tau}$, while the dependence on $\epsilon_{\mu\tau}$ and $\epsilon_{\tau\tau}$ is seen to be very mild, once the $\chi^2$ is marginalised over oscillation and NSI parameters. If the NSI are large enough, the event spectrum at ICAL is expected to be altered and this can be used to discover new physics. We calculate the lower limit on NSI parameters above which ICAL could discover NSI at a given C.L. from 10 years of data. If NSI were too small, the null signal at ICAL can constrain the NSI parameters. We give upper limits on the NSI parameters at any given C.L. that one is expected to put from 10 years of running of ICAL. Finally, we give C.L. contours in the NSI parameter space that is expected to be still allowed from 10 years of running of the experiment., Comment: 24 pages, minor improvements

We investigate the impact of non-standard neutrino interactions (NSIs) on atmospheric neutrinos using the proposed PINGU experiment. In particular, we focus on the matter NSI parameters $\varepsilon_{\mu\tau}$ and $|\varepsilon_{\tau\tau} - \varepsilon_{\mu\mu}|$ that have previously been constrained by the Super-Kamiokande experiment. First, we present approximate analytical formulas for the difference of the muon neutrino survival probability with and without the above-mentioned NSI parameters. Second, we calculate the atmospheric neutrino events at PINGU in the energy range (2-100) GeV, which follow the trend outlined on probability level. Finally, we perform a statistical analysis of PINGU. Using three years of data, we obtain bounds from PINGU given by $-0.0043~(-0.0048) < \varepsilon_{\mu\tau} < 0.0047~(0.0046)$ and $-0.03~(-0.016) < \varepsilon_{\tau\tau} < 0.017~(0.032)$ at 90 % confidence level for normal (inverted) neutrino mass hierarchy, which improve the Super-Kamiokande bounds by one order of magnitude. In addition, we show the expected allowed contour region in the $\varepsilon_{\mu\tau}$-$\varepsilon_{\tau\tau}$ plane if NSIs exist in Nature and the result suggests that there is basically no correlation between $\varepsilon_{\mu\tau}$ and $\varepsilon_{\tau\tau}$., Comment: 19 pages, 7 figures. Final version published in Phys. Lett. B

In the context of non-supersymmetric SO(10) models, we analyze the renormalization group equations for the fermions (including neutrinos) from the GUT energy scale down to the electroweak energy scale, explicitly taking into account the effects of an intermediate energy scale induced by a Pati--Salam gauge group. To determine the renormalization group running, we use a numerical minimization procedure based on a nested sampling algorithm that randomly generates the values of 19 model parameters at the GUT scale, evolves them, and finally constructs the values of the physical observables and compares them to the existing experimental data at the electroweak scale. We show that the evolved fermion masses and mixings present sizable deviations from the values obtained without including the effects of the intermediate scale., Comment: Comments: 20 pages, 3 figures. Final version published in JHEP

We reconsider the extrinsic and possible intrinsic CPT violation in neutrino oscillations, and point out an identity, i.e., $A^{\rm CP}_{\alpha \beta} = A^{\rm CPT}_{\beta \alpha} + A^{\rm T}_{\alpha \beta}$, among the CP, T, and CPT asymmetries in oscillations. For three-flavor oscillations in matter of constant density, the extrinsic CPT asymmetries $A^{\rm CPT}_{ee}$, $A^{\rm CPT}_{e\mu}$, $A^{\rm CPT}_{\mu e}$, and $A^{\rm CPT}_{\mu \mu}$ caused by Earth matter effects have been calculated in the plane of different neutrino energies and baseline lengths. It is found that two analytical conditions can be implemented to describe the main structure of the contours of vanishing extrinsic CPT asymmetries. Finally, without assuming intrinsic CPT symmetry in the neutrino sector, we investigate the possibility to constrain the difference of the neutrino CP-violating phase $\delta$ and the antineutrino one $\overline{\delta}$ using a low-energy neutrino factory and the super-beam experiment ESS$\nu$SB. We find that $|\delta - \overline{\delta}| \lesssim 0.35\pi$ in the former case and $|\delta - \overline{\delta}| \lesssim 0.7\pi$ in the latter case can be achieved at the $3\sigma$ confidence level if $\delta = \overline{\delta} = \pi/2$ is assumed., Comment: 26 pages, 6 figures, more discussions added, matches the published version

Models of neutrino mixing involving one or more sterile neutrinos have resurrected their importance in the light of recent cosmological data. In this case, reactor antineutrino experiments offer an ideal place to look for signatures of sterile neutrinos due to their impact on neutrino flavor transitions. In this work, we show that the high-precision data of the Daya Bay experi\-ment constrain the 3+1 neutrino scenario imposing upper bounds on the relevant active-sterile mixing angle $\sin^2 2 \theta_{14} \lesssim 0.06$ at 3$\sigma$ confidence level for the mass-squared difference $\Delta m^2_{41}$ in the range $(10^{-3},10^{-1}) \, {\rm eV^2}$. The latter bound can be improved by six years of running of the JUNO experiment, $\sin^22\theta_{14} \lesssim 0.016$, although in the smaller mass range $ \Delta m^2_{41} \in (10^{-4} ,10^{-3}) \, {\rm eV}^2$. We have also investigated the impact of sterile neutrinos on precision measurements of the standard neutrino oscillation parameters $\theta_{13}$ and $\Delta m^2_{31}$ (at Daya Bay and JUNO), $\theta_{12}$ and $\Delta m^2_{21}$ (at JUNO), and most importantly, the neutrino mass hierarchy (at JUNO). We find that, except for the obvious situation where $\Delta m^2_{41}\sim \Delta m^2_{31}$, sterile states do not affect these measurements substantially., Comment: 23 pages, 9 figures, more discussions added, matches the published version

Neutrinos are the most elusive particles in our universe. They have masses at least one million times smaller than the electron mass, carry no electric charge, and very weakly interact with other particles, meaning they are rarely captured in terrestrial detectors. Tremendous efforts in the past two decades have revealed that neutrinos can transform from one type to another as a consequence of neutrino oscillations---a quantum mechanical effect over macroscopic distances---yet the origin of neutrino masses remains puzzling. The physical evolution of neutrino parameters with respect to energy scale may help elucidate the mechanism for their mass generation., Comment: 33 pages, 3 figures, 2 tables. Final version (authors' post-print version) published in Nature Communications

Precision measurements of leptonic mixing parameters and the determination of the neutrino mass hierarchy are the primary goals of the forthcoming medium-baseline reactor antineutrino experiments, such as JUNO and RENO-50. In this work, we investigate the impact of nonstandard neutrino interactions (NSIs) on the measurements of {sin^2 theta_{12}, Delta m^2_{21}} and {sin^2 theta_{13}, Delta m^2_{31}}, and on the sensitivity to the neutrino mass hierarchy, at the medium-baseline reactor experiments by assuming a typical experimental setup. It turns out that the true mixing parameter sin^2 theta_{12} can be excluded at a more than 3 sigma level if the NSI parameter varepsilon_{e mu} or varepsilon_{e tau} is as large as 2% in the most optimistic case. However, the discovery reach of NSI effects has been found to be small, and depends crucially on the CP-violating phases. Finally, we show that NSI effects could enhance or reduce the discrimination power of the JUNO and RENO-50 experiments between the normal and inverted neutrino mass hierarchies., Comment: 18 pages, 7 figures, references updated, matches the published version

In Phys. Rev. Lett. 109 (2012) 231301, van den Aarssen et al. attempt to solve all the small-scale structure problems in the cold-dark-matter scenario by introducing interaction between the dark-matter particle and an MeV-mass vector boson. In addition, the latter is coupled to ordinary neutrinos, and the neutrino-vector boson coupling constant 10^{-5} < g_nu < 0.1 is required for that purpose. We show that this dark-matter scenario is subject to restrictive constraints from Big Bang Nucleosynthesis., Comment: 2 pages, 1 figure

Neutrino oscillation experiments in the past decades have greatly improved our knowledge on neutrinos by measuring the fundamental neutrino parameters. The ongoing and upcoming neutrino oscillation experiments are intended to pin down the neutrino mass hierarchy and to discover the leptonic CP violation. By means of neutrino oscillograms, we analyze the impact of non-standard neutrino interactions on neutrino oscillations in the Earth matter. The standard neutrino oscillation probabilities may be significantly changed by non-standard interaction parameters, and in particular, the CP-violating effects in the energy range E = 1 ~ 20 GeV are greatly enhanced. In addition, the event rates of muon neutrinos in the proposed huge atmospheric neutrino experiment, PINGU at the South Pole, have been estimated in the presence of non-standard neutrino interactions. It has been found that the PINGU experiment has very good sensitivities to the non-standard neutrino interaction parameters., Comment: 20 pages, 7 figures, minor changes, matches the published version in Phys. Rev. D

The discovery of leptonic CP violation is one of the primary goals of next-generation neutrino oscillation experiments, which is feasible due to the recent measurement of a relatively large leptonic mixing angle \theta_{13}. We suggest two new working observables \Delta A^{\rm m}_{\alpha \beta} \equiv \max[A^{\rm CP}_{\alpha \beta}(\delta)] - \min[A^{\rm CP}_{\alpha \beta}(\delta)] and \Delta A^{\rm CP}_{\alpha \beta}(\delta) \equiv A^{\rm CP}_{\alpha \beta}(\delta) - A^{\rm CP}_{\alpha \beta}(0) to describe the CP-violating effects in long-baseline and atmospheric neutrino oscillation experiments. The former signifies the experimental sensitivity to the leptonic Dirac CP-violating phase $\delta$ and can be used to optimize the experimental setup, while the latter measures the intrinsic leptonic CP violation and can be used to extract $\delta$ directly from the experimental observations. Both analytical and numerical analyses are carried out to illustrate their main features. It turns out that an intense neutrino beam with sub-GeV energies and a baseline of a few 100 km may serve as an optimal experimental setup for probing leptonic CP violation., Comment: 7 pages, 4 figures, discussions extended, matches the published version. The neutrino oscillograms for different channels and neutrino mass hierarchies can be found at http://www.theophys.kth.se/tepp/oscillograms/

Since the smallest leptonic mixing angle theta_{13} has been measured to be relatively large, it is quite promising to constrain or determine the leptonic Dirac CP-violating phase delta in future neutrino oscillation experiments. Given some typical values of delta = pi/2, pi, and 3pi/2 at the low-energy scale, as well as current experimental results of the other neutrino parameters, we perform a systematic study of the radiative corrections to delta by using the one-loop renormalization group equations in the minimal supersymmetric standard model and the universal extra-dimensional model. It turns out that delta is rather stable against radiative corrections in both models, except for the minimal supersymmetric standard model with a very large value of tan beta. Both cases of Majorana and Dirac neutrinos are discussed. In addition, we use the preliminary indication of delta = (1.08^{+0.28}_{-0.31}) pi or delta = (1.67^{+0.37}_{-0.77}) pi from the latest global-fit analyses of data from neutrino oscillation experiments to illustrate how it will be modified by radiative corrections., Comment: 23 pages, 4 eps figures, minor changes, matches the published version

The phenomenon of neutrino oscillations has been established as the leading mechanism behind neutrino flavor transitions, providing solid experimental evidence that neutrinos are massive and lepton flavors are mixed. Here we review sub-leading effects in neutrino flavor transitions known as non-standard neutrino interactions, which is currently the most explored description for effects beyond the standard paradigm of neutrino oscillations. In particular, we report on the phenomenology of non-standard neutrino interactions and their experimental and phenomenological bounds as well as future sensitivity and discovery reach., Comment: 51 pages, 11 figures. Final version published in Rep. Prog. Phys

We investigate a six-dimensional universal extra-dimensional model in the extension of an effective neutrino mass operator. We derive the \beta-functions and renormalization group equations for the Yukawa couplings, the Higgs self-coupling, and the effecive neutrino mass operator in this model. Especially, we focus on the renormalization group running of physical parameters such as the Higgs self-coupling and the leptonic mixing angles. The recent measurements of the Higgs boson mass by the ATLAS and CMS collaborations at the LHC as well as the current three-flavor global fits of neutrino oscillation data have been taken into account. We set a bound on the six-dimensional model, using the vacuum stability criterion, that allows five Kaluza-Klein modes only, which leads to a strong limit on the cutoff scale. Furthermore, we find that the leptonic mixing angle \theta_{12} shows the most sizable running, and that the running of the angles \theta_{13} and \theta_{23} are negligible. Finally, it turns out that the findings in this six-dimensional model are comparable with what is achieved in the corresponding five-dimensional model, but the cutoff scale is significantly smaller, which means that it could be detectable in a closer future., Comment: 14 pages, 3 figures. Final version published in Phys. Lett. B

With the advent of the recent measurements in neutrino physics, we investigate the role of high-energy neutrino flux ratios at neutrino telescopes for the possibility of determining the leptonic CP-violating phase \delta and the underlying pattern of the leptonic mixing matrix. We find that the flux ratios show a dependence of O(10 %) on the CP-violating phase, and for optimistic uncertainties on the flux ratios less than 10 %, they can be used to distinguish between CP-conserving and CP-violating values of the phase at 2\sigma in a non-vanishing interval around the maximal value |\delta|=\pi/2., Comment: 10 pages, 5 figures. Final version published in Phys. Rev. D

We study the first Kaluza-Klein excitation of the Higgs boson in universal extra dimensions as a dark matter candidate. The first-level Higgs boson could be the lightest Kaluza-Klein particle, which is stable due to the conservation of Kaluza-Klein parity, in non-minimal models where boundary localized terms modify the mass spectrum. We calculate the relic abundance and find that it agrees with the observed dark matter density if the mass of the first-level Higgs boson is slightly above 2 TeV, not considering coannihilations and assuming no relative mass splitting among the first-level Kaluza-Klein modes. In the case of coannihilations and a non-zero mass splitting, the mass of the first-level Higgs boson can range from 1 TeV to 4 TeV. We study also the prospects for detection of this dark matter candidate in direct as well as indirect detection experiments. Although the first-level Higgs boson is a typical weakly interacting massive particle, an observation in any of the conventional experiments is very challenging., Comment: 16 pages, 7 figures. Final version published in Phys. Lett. B

We point out a conceptual analogy between the physics of extra spatial dimensions and the physics of carbon nanotubes which arises for principle reasons, although the corresponding energy scales are at least ten orders of magnitude apart. For low energies, one can apply the Kaluza-Klein description to both types of systems, leading to two completely different but consistent interpretations of the underlying physics. In particular, we discuss in detail the Kaluza-Klein description of armchair and zig-zag carbon nanotubes. Furthermore, we describe how certain experimental results for carbon nanotubes could be re-interpreted in terms of the Kaluza-Klein description. Finally, we present ideas for new measurements that could allow to probe concepts of models with extra spatial dimensions in table-top experiments, providing further links between condensed matter and particle physics., Comment: 5 pages, 1 figure; references updated, title changed according to referee's suggestion; content matches published version