Search for Lepton Flavour Violation in the Decay tau -> mu gamma

A search for the lepton flavour violating decay tau -> mu gamma has been performed using 221.4/fb of data collected at an e+e- centre-of-mass energy of 10.58 GeV with the BABAR detector at the PEP-II storage ring. The search has an efficiency of (7.45+/-0.65)% for an expected background level of 6.2+/-0.5 events. In the final sample 4 candidate events are selected. As there is no evidence for a signal in this data, for this preliminary result we set an upper limit of BR(tau -> mu gamma) < 9 x 10^-8 at 90%CL using the method of Feldman and Cousins.Comment: 7 pages, 3 encapsulated postscript figures, uses espcrc2.st

Advanced Integration in Multi-Scale Mechanics and Welding Process Simulation in Weld Integrity Assessment

In this project, mathematical models that predict the microstructure in pipeline steel welds were to be developed. These models were to be integrated with thermal models that describe the time-temperature history in the weld as a function of location in order to derive the spatial variation of microstructure in the weld. The microstructure predictions were also to be combined with microstructure-hardness relations, based on the additivity principle, to determine the spatial variation of hardness in the weld. EMC2 also developed microstructural models based on empirical relationships. ORNL was to pursue the development of more fundamental, theoretically based models. ORNL applied a previously developed model for inclusion formation to predict the extent and nature of inclusions that form during weld cooling from the liquid. This inclusion model was directly integrated with computational thermodynamics capability. A convenient user interface was developed for both the inclusion model and the thermodynamic phase-stability calculations. The microstructure model was based on the simultaneous transformation theory analysis as applied to the transformation of austenite to various ferrite constituents during weld cooling. The model available on the Materials Algorithm Project web site was used. Extensive modification of this model was required to correct problems with compilation and calculations as a function of the computational platform (Unix, Linux, Windows, etc.) that was used. The user interface for the inclusion model and thermodynamic phase-stability calculations was delivered to EMC2 along with the modified and correct microstructure model. Evaluation of the theoretically based model will be carried out and the predictions will be compared with experimental results as well as predictions based on the empirical models developed by EMC2

Dynamic assembly of Hda and the sliding clamp in the regulation of replication licensing

Regulatory inactivation of DnaA (RIDA) is one of the major regulatory mechanisms of prokaryotic replication licensing. In RIDA, the Hda-sliding clamp complex loaded onto DNA directly interacts with adenosine triphosphate (ATP)-bound DnaA and stimulates the hydrolysis of ATP to inactivate DnaA. A prediction is that the activity of Hda is tightly controlled to ensure that replication initiation occurs only once per cell cycle. Here, we determined the crystal structure of the Hda-�� clamp complex. This complex contains two pairs of Hda dimers sandwiched between two �� clamp rings to form an octamer that is stabilized by three discrete interfaces. Two separate surfaces of Hda make contact with the �� clamp, which is essential for Hda function in RIDA. The third interface between Hda monomers occludes the active site arginine finger, blocking its access to DnaA. Taken together, our structural and mutational analyses of the Hda-�� clamp complex indicate that the interaction of the �� clamp with Hda controls the ability of Hda to interact with DnaA. In the octameric Hda-�� clamp complex, the inability of Hda to interact with DnaA is a novel mechanism that may regulate Hda function. ? The Author(s) 2017.113Ysciescopu

Finite SU(N)^k Unification

We consider N=1 supersymmetric gauge theories based on the group SU(N)_1 x SU(N)_2 x ... x SU(N)_k with matter content (N,N*,1,...,1) + (1,N,N*,...,1) + >... + (N*,1,1,...,N) as candidates for the unification symmetry of all particles. In particular we examine to which extent such theories can become finite and we find that a necessary condition is that there should be exactly three families. We discuss further some phenomenological issues related to the cases (N,k) = (3,3), (3,4), and (4,3), in an attempt to choose those theories that can become also realistic. Thus we are naturally led to consider the SU(3)^3 model which we first promote to an all-loop finite theory and then we study its additional predictions concerning the top quark mass, Higgs mass and supersymmetric spectrum.Comment: 15 page

Bilinear R-parity Violation and Small Neutrino Masses: a Self-consistent Framework

We study extensions of supersymmetric models without R-parity which include an anomalous U(1)_H horizontal symmetry. Bilinear R-parity violating terms induce a neutrino mass at tree level of approximately $(\theta^2)^\delta$ eV where $\theta\approx 0.22$ is the U(1)_H breaking parameter and $\delta$ is an integer number that depends on the horizontal charges of the leptons. For $\delta=1$ a unique self-consistent model arises in which i) all the superpotential trilinear R-parity violating couplings are forbidden by holomorphy; ii) the tree level neutrino mass falls in the range suggested by the atmospheric neutrino problem; iii) radiative contributions to neutrino masses are strongly suppressed resulting in a squared solar mass difference of few 10^{-8} eV^2 which only allows for the LOW (or quasi-vacuum) solution to the solar neutrino problem; iv) the neutrino mixing angles are not suppressed by powers of $\theta$ and can naturally be large.Comment: Latex, 15 pages including 1 figure, some typos correcte

Possible Gauge Theoretic Origin for Quark-Lepton Complementarity

Similarity between the weak interaction properties of quarks and leptons has led to suggestions that the origin of lepton mixing angles may be related to those of quarks. In this paper, we present a gauge model based on $SU(2)_L \times SU(2)_R\times SU(4)_c$ group that leads to a new form for the quark lepton complementarity which predicts the solar neutrino mixing angle in terms of the Cabibbo angle for the case of inverted mass hierarchy for neutrinos. We also indicate how these ideas can be implemented in an $E_6$ inspired trinification $SU(3)_C \times SU(3)_L \times SU(3)_R$ model, which is more closely allied to string theory by the AdS/CFT correspondence.Comment: 9 pages, latex, no figures; presentation improved; results unchanged; minor typos correcte

b-physics signals of the lightest CP-odd Higgs in the NMSSM at large tan beta

We investigate the low energy phenomenology of the lighter pseudoscalar $A_1^0$ in the NMSSM. The $A_1^0$ mass can naturally be small due to a global $U(1)_R$ symmetry of the Higgs potential, which is only broken by trilinear soft terms. The $A_1^0$ mass is further protected from renormalization group effects in the large $\tan \beta$ limit. We calculate the $b \to s A_1^0$ amplitude at leading order in $\tan \beta$ and work out the contributions to rare $K$, $B$ and radiative $\Upsilon$-decays and $B -\bar B$ mixing. We obtain constraints on the $A_1^0$ mass and couplings and show that masses down to ${\cal{O}}(10)$ MeV are allowed. The $b$-physics phenomenology of the NMSSM differs from the MSSM in the appearance of sizeable renormalization effects from neutral Higgses to the photon and gluon dipole operators and the breakdown of the MSSM correlation between the $B_s \to \mu^+ \mu^-$ branching ratio and $B_s - \bar B_s$ mixing. For $A_1^0$ masses above the tau threshold the $A_1^0$ can be searched for in $b \to s \tau^+ \tau^-$ processes with branching ratios \lsim 10^{-3}.Comment: 18 pages, 3 figures; references adde

Higgs-boson production associated with a bottom quark at hadron colliders with SUSY-QCD corrections

The Higgs boson production p p (p\bar p) -> b h +X via b g -> b h at the LHC, which may be an important channel for testing the bottom quark Yukawa coupling, is subject to large supersymmetric quantum corrections. In this work the one-loop SUSY-QCD corrections to this process are evaluated and are found to be quite sizable in some parameter space. We also study the behavior of the corrections in the limit of heavy SUSY masses and find the remnant effects of SUSY-QCD. These remnant effects, which are left over in the Higgs sector by the heavy sparticles, are found to be so sizable (for a light CP-odd Higgs and large \tan\beta) that they might be observable in the future LHC experiment. The exploration of such remnant effects is important for probing SUSY, especially in case that the sparticles are too heavy (above TeV) to be directly discovered at the LHC.Comment: Results for the Tevatron adde

Top-quark rare decay t→cht\to c h in R-parity-violating SUSY

The flavor-changing top-quark decay $t\to c h$, where $h$ is the lightest CP-even Higgs boson in the minimal supersymmetric standard model, is examined in the R-parity-violating supersymmetric model. Within the existing bounds on the relevant R-parity-violating couplings, the branching fraction for $t\to c h$ can be as large as about $10^{-5}$ in some part of the parameter space.Comment: version to appear in Phys. Lett.

Gauge and Scheme Dependence of Mixing Matrix Renormalization

We revisit the issue of mixing matrix renormalization in theories that include Dirac or Majorana fermions. We show how a gauge-variant on-shell renormalized mixing matrix can be related to a manifestly gauge-independent one within a generalized ${\bar {\rm MS}}$ scheme of renormalization. This scheme-dependent relation is a consequence of the fact that in any scheme of renormalization, the gauge-dependent part of the mixing-matrix counterterm is ultra-violet safe and has a pure dispersive form. Employing the unitarity properties of the theory, we can successfully utilize the afore-mentioned scheme-dependent relation to preserve basic global or local symmetries of the bare Lagrangian through the entire process of renormalization. As an immediate application of our study, we derive the gauge-independent renormalization-group equations of mixing matrices in a minimal extension of the Standard Model with isosinglet neutrinos.Comment: 31 pages, LaTeX, uses axodraw.st