Dilepton Signal of a Type-II Seesaw at CERN LHC: Reveals a TeV Scale B-L Symmetry

We explore the discovery potential of doubly charged Higgs bosons (\xi^{\pm\pm}) at the CERN Large Hadron Collider (LHC). For moderate values of the coupling constants in the original Type-II seesaw model, these doubly-charged Higgs bosons are not accessible by any present or near future collider experiments. In a gauged B-L symmetric model we introduce two triplet scalars to execute a variant of type-II seesaw at the TeV scale. This leads to a clear like-sign dilepton signal in the decay mode of \xi^{\pm\pm} for a small vacuum expectation value (\lsim 10^5 \eV) of the triplet scalar \xi= (\xi^{++}, \xi^+, \xi^0) of mass \lsim 1 \TeV. To be specific, for a mass range of 200-1000 GeV of \xi^{\pm\pm}, the like-sign dilepton signal can be detected at CERN LHC at a center of mass energy 14 TeV with an integrated luminosity > 30 {\rm fb}^{-1}. The same analysis is also pursued with center of mass energies 7 TeV and 10 TeV as well. We also comment on the decay mode of singly charged scalars and neutral B-L gauge boson in this model.Comment: Minor change in Introduction, Z' contribution to the production of doubly charged scalars are explicitly shown, new figures added, new references added. To appear in Physical Review

The U(1) symmetry of the non-tribimaximal pattern in the degenerate mass spectrum case of the neutrino mass matrix

On account of the new neutrino oscillation data signalling a non-zero value for the smallest mixing angle ($\theta_z$), we present an explicit realization of the underlying U(1) symmetry characterizing the maximal atmospheric mixing angle ($\theta_y = \pi / 4$) pattern with two degenerate masses but now with generic values of $\theta_z$. We study the effects of the form invariance with respect to U(1), and/or $Z_3$, $Z_2$ subgroups, on the Yukawa couplings and the mass terms. Later on, we specify $\theta_z$ to its experimental best fit value ($\sim 8^o$), and impose the symmetry in an entire model which includes charged leptons, and many Higgs doublets or standard model singlet heavy scalars, to show that it can make room for the charged lepton mass hierarchies. In addition, we show for the non-tribimaximal value of $\theta_z \neq 0$ within type-I seesaw mechanism enhanced with flavor symmetry that neutrino mass hierarchies can be generated. Furthermore, lepton/baryogenesis can be interpreted via type-II seesaw mechanism within a setup meeting the flavor U(1)-symmetry.Comment: latex, 1 table, 20 pages. Typos are corrected, shortened version to appear in Phys. Rev.

Small neutrino masses due to R-symmetry breaking for a small cosmological constant

We describe a class of supersymmetric models in which neutrinos are kept light by an R-symmetry. In supergravity, R-symmetry must be broken to allow for a small cosmological constant after supersymmetry breaking. In the class of models described here, this R-symmetry breaking results in the generation of Dirac neutrino masses, connecting the tuning of the cosmological constant to the puzzle of neutrino masses. Surprisingly, under the assumption of low-scale supersymmetry breaking and superpartner masses close to a TeV, these masses are independent of the fundamental supersymmetry-breaking scale, and accommodate the correct magnitude. This offers a novel explanation for the vastly different scales of neutrino and charged fermion masses. These models require that R-symmetric supersymmetry exists at the TeV scale, and predict that neutrino masses are purely Dirac, implying the absence of neutrino-less double beta-decay. Interesting collider signals can arise due to charged scalars which decay leptonically, with branching ratios determined by the neutrino mixing matrix.Comment: 6 pages, 2 figures. v2 matches published versio

Nonlinear Dynamics in Distributed Systems

We build on a previous statistical model for distributed systems and formulate it in a way that the deterministic and stochastic processes within the system are clearly separable. We show how internal fluctuations can be analysed in a systematic way using Van Kanpen's expansion method for Markov processes. We present some results for both stationary and time-dependent states. Our approach allows the effect of fluctuations to be explored, particularly in finite systems where such processes assume increasing importance.Comment: Two parts: 8 pages LaTeX file and 5 (uuencoded) figures in Postscript forma

Classical predictability and coarse-grained evolution of the quantum baker's map

We investigate how classical predictability of the coarse-grained evolution of the quantum baker's map depends on the character of the coarse-graining. Our analysis extends earlier work by Brun and Hartle [Phys. Rev. D 60, 123503 (1999)] to the case of a chaotic map. To quantify predictability, we compare the rate of entropy increase for a family of coarse-grainings in the decoherent histories formalism. We find that the rate of entropy increase is dominated by the number of scales characterising the coarse-graining.Comment: 28 pages, 1 figur

A little inflation at the cosmological QCD phase transition

We reexamine the recently proposed "little inflation" scenario that allows for a strong first order phase-transition of QCD at non-negligible baryon number in the early universe and its possible observable consequences. The scenario is based on the assumptions of a strong mechanism for baryogenesis and a quasistable QCD-medium state which triggers a short inflationary period of inflation diluting the baryon asymmetry to the value observed today. The cosmological implications are reexamined, namely effects on primordial density fluctuations up to dark matter mass scales of M_{max} \sim 1 M_{\astrosun}, change in the spectral slope up to M_{max} \sim 10^6 M_{\astrosun}, production of seeds for the present galactic and extragalactic magnetic fields and a gravitational wave spectrum with a peak frequency around $\nu_{peak} \sim 4 \cdot 10^{-8} Hz$. We discuss the issue of nucleation in more detail and employ a chiral effective model of QCD to study the impact on small scale structure formation.Comment: 18 pages, 12 figures, several extensions to the text and structure formation part was rephrased for better readabilit

New physics from ultrahigh energy cosmic rays

Cosmic rays from outer space enter the atmosphere with energies of up to 10^{11} GeV. The initial particle or a secondary hadron inside the shower may then interact with an air nucleon to produce nonstandard particles. In this article we study the production of new physics by high energy cosmic rays, focusing on the long-lived gluino of split-SUSY models and a WIMP working as dark matter. We first deduce the total flux of hadron events at any depth in the atmosphere, showing that secondary hadrons can not be neglected. Then we use these results to find the flux of gluinos and WIMPs that reach the ground after being produced inside air showers. We also evaluate the probability of producing these exotic particles in a single proton shower of ultrahigh energy. Finally we discuss the possible signal in current and projected experiments. While the tiny flux of WIMPs does not seem to have any phenomenological consequences, we show that the gluinos could modify substantially the profile of a small fraction of extensive air showers. In particular, they could produce a distinct signal observable at AUGER in showers of large zenith angle.Comment: 9 pages, version to appear in PR

Unification via intermediate symmetry breaking scales with the quartification gauge group

The idea of quark-lepton universality at high energies has been introduced as a natural extension to the standard model. This is achieved by endowing leptons with new degrees of freedom -- leptonic colour, an analogue of the familiar quark colour. Grand and partially unified models which utilise this new gauge symmetry SU(3)_\ell have been proposed in the context of the quartification gauge group SU(3)^4. Phenomenologically successful gauge coupling constant unification without supersymmetry has been demonstrated for cases where the symmetry breaking leaves a residual SU(2)_\ell unbroken. Though attractive, these schemes either incorporate ad hoc discrete symmetries and non-renormalisable mass terms, or achieve only partial unification. We show that grand unified models can be constructed where the quartification group can be broken fully [i.e. no residual SU(2)_\ell] to the standard model gauge group without requiring additional discrete symmetries or higher dimension operators. These models also automatically have suppressed nonzero neutrino masses. We perform a systematic analysis of the renormalisation-group equations for all possible symmetry breaking routes from SU(3)^4 --> SU(3)_q x SU(2)_L x U(1)_Y. This analysis indicates that gauge coupling unification can be achieved for several different symmetry breaking patterns and we outline the requirements that each gives on the unification scale. We also show that the unification scenarios of those models which leave a residual SU(2)_\ell symmetry are not unique. In both symmetry breaking cases, some of the scenarios require new physics at the TeV scale, while others do not allow for new TeV phenomenology in the fermionic sector.Comment: 25 page

A Survey of Lepton Number Violation Via Effective Operators

We survey 129 lepton number violating effective operators, consistent with the minimal Standard Model gauge group and particle content, of mass dimension up to and including eleven. Upon requiring that each one radiatively generates the observed neutrino masses, we extract an associated characteristic cutoff energy scale which we use to calculate other observable manifestations of these operators for a number of current and future experimental probes, concentrating on lepton number violating phenomena. These include searches for neutrinoless double-beta decay and rare meson, lepton, and gauge boson decays. We also consider searches at hadron/lepton collider facilities in anticipation of the LHC and the future ILC. We find that some operators are already disfavored by current data, while more are ripe to be probed by next-generation experiments. We also find that our current understanding of lepton mixing disfavors a subset of higher dimensional operators. While neutrinoless double-beta decay is the most promising signature of lepton number violation for the majority of operators, a handful is best probed by other means. We argue that a combination of constraints from various independent experimental sources will help to pinpoint the ``correct'' model of neutrino mass, or at least aid in narrowing down the set of possibilities.Comment: 34 pages, 10 eps figures, 1 tabl

Phenomenology of 10^32 Dark Sectors

We postulate an exact permutation symmetry acting on 10^32 Standard Model copies as the largest possible symmetry extension of the Standard Model. This setup automatically lowers the fundamental gravity cutoff down to TeV, and thus, accounts for the quantum stability of the weak scale. We study the phenomenology of this framework and show that below TeV energies the copies are well hidden, obeying all the existing observational bounds. Nevertheless, we identify a potential low energy window into the hidden world, the oscillation of the neutron into its dark copies. At the same time, proton decay can be suppressed by gauging the diagonal baryon number of the different copies. This framework offers an alternative approach to several particle physics questions. For example, we suggest a novel mechanism for generating naturally small neutrino masses that are suppressed by the number of neutrino species. The mirror copies of the Standard Model naturally house dark matter candidates. The general experimentally observable prediction of this scenario is an emergence of strong gravitational effects at the LHC. The low energy permutation symmetry powerfully constrains the form of this new gravitational physics and allows to make observational predictions, such as, production of micro black-holes with very peculiar properties.Comment: 36 pages. v2, note added on oscillation of neutral state, Refs. adde