33634938
Standardlike models as type IIB flux vacua
We construct new semirealistic type IIB flux vacua on ${Z}_{2}\ifmmode\times\else\texttimes\fi{}{Z}_{2}$ orientifolds with three- and four-standard model families and up to three units of quantized flux. The open string sector is comprised of magnetized D-branes and is T-dual to supersymmetric intersecting D6-brane constructions. The standard model sector contains magnetized D9-branes with negative D3-brane charge contribution. There are large classes of such models and we present explicit constructions for representative ones. In addition to models with one and two units of quantized flux, we also construct the first three- and four-family standard-like models with supersymmetric fluxes, i.e. comprising three units of quantized flux. Supergravity fluxes are due to the self-dual Neveu-Schwarz-Neveu-Schwarz and Ramond-Ramond three-form field strength and they fix the toroidal complex structure moduli and the dilaton. The supersymmetry conditions for the D-brane sector fix in some models all three toroidal K\"ahler moduli. We also provide examples where toroidal K\"ahler moduli are fixed by strong gauge dynamics on the ``hidden sector'' D7-brane. Most of the models possess Higgs doublet pairs with Yukawa couplings that can generate masses for quarks and leptons. The models have (mainly right-) chiral exotics.
118316245
Exotic Higgs Decay h to 2a at the International Linear Collider: a Snowmass White Paper
A Higgs factory like the International Linear Collider (ILC) can play a significant role in searching for exotic decays of Higgs bosons. As an illustration, we investigate the ILC sensitivity for the decay topology $h\to a_1 a_1 \to \tau\bar \tau\tau \bar \tau$ in the Next-to-Minimal-Supersymmetric-Standard-Model (NMSSM). Here $h$ can be either Standard-Model-like or non-standard, and $a_{1}$ is the lightest CP-odd Higgs boson. We also compare results to expectations for this channel at the LHC.
17752635
Quasi-supersymmetric G3 unification from intersecting D6-branes on Type IIA orientifolds
Abstract We construct three quasi-supersymmetric G 3 GUT models with S 3 symmetry and gauge coupling unification from intersecting D6-branes on Type IIA orientifolds. The Standard Model fermions and Higgs doublets can be embedded into the bifundamental representations in these models, and there is no any other unnecessary massless representation. Especially in Model I with gauge group U (4) 3 , we just have three-family SM fermions and three pairs of Higgs particles. The G 3 gauge symmetry in these models can be broken down to the Standard Model gauge symmetry by introducing light open string states. And 1 TeV scale supersymmetry breaking soft masses imply the reasonable intermediate string scale.
118634638
Flavor transition mechanisms of propagating astrophysical neutrinos: A model independent parametrization
One of the important goals for future neutrino telescopes is to identify the flavors of astrophysical neutrinos and therefore determine the flavor ratio. The flavor ratio of astrophysical neutrinos observed on the Earth depends on both the initial flavor ratio at the source and flavor transitions taking place during propagations of these neutrinos. We propose a model independent parametrization for describing the above flavor transitions. A few flavor transition models are employed to test our parametrization. The observational test for flavor transition mechanisms through our parametrization is discussed.
122670904
The design of 8-Gbps VCSEL drivers for ATLAS liquid Argon calorimeter upgrade
We present designs and preliminary test results of LOCld1 and LOCld4, VCSEL drivers in a commercial 0.25-mu m m Silicon-on-Sapphire (SoS) CMOS process for ATLAS liquid Argon calorimeter upgrade. Active shunt peaking, multiple-stage amplification and higher voltage supply are used to achieve the data rate of 8 Gbps. LOCld1 is a single channel VCSEL driver with a differential output, while LOCld4 has four channels with single-ended open-drain outputs. Both drivers have tunable modulation and peaking strength. Bias current for VCSEL is also embedded.
118430959
Quark angular momentum in a spectator model
Abstract We investigate the quark angular momentum in a model with the nucleon being a quark and a spectator. Both scalar and axial-vector spectators are included. We perform the calculations in the light-cone formalism where the parton concept is well defined. We calculate the quark helicity and canonical orbital angular momentum. Then we calculate the gravitational form factors which are often related to the kinetic angular momentums, and find that even in a no gauge field model we cannot identify the canonical angular momentums with half the sum of gravitational form factors. In addition, we examine the model relation between the orbital angular momentum and pretzelosity, and find it is violated in the axial-vector case.
117322725
Determination of the Source Flavor Ratio of Ultrahigh Energy Neutrinos
We discuss the reconstruction of neutrino flavor neutrino at a distant source in the very high en- ergy regime. This reconstruction procedure is relevant to the confirmation of detecting cosmogenic neutrinos, for example. To facilitate such a reconstruction, it is imperative to achieve effective flavor discriminations in terrestrial neutrino telescopes. We note that, for energies beyond few tens of PeV, a tau-lepton behaves like a track similar to a muon. Hence, while it is rather challenging to separate {\nu}{\mu} from {\nu}{\tau} in this case, one can expect to isolate {\nu}e from the rest by a distinctive shower signature. We present the result of flavor ratio reconstruction given the anticipated accuracies of flavor measurement in neutrino telescopes and current uncertainties of neutrino mixing parame- ters. It is shown that the further separation between {\nu}{\mu} and {\nu}{\tau} events does not improve the flavor reconstruction due to the approximate {\nu}{\mu} - {\nu}{\tau} symmetry.
17176468
Status report on the LOC ASIC
Based on a commercially available 0.25 μm Silicon on Sapphire CMOS technology, we are developing the LOC ASIC for high speed serial data transmission in the front-end electronics systems of the ATLAS upgrade for the SLHC 1 . Evaluation of this technology for applications in the SLHC, based on a dedicated test chip, has been performed with irradiation tests in gamma (Co-60) and in 230 MeV proton beams. Test results indicate that this may be a candidate technology of ASIC developments for the SLHC. More thorough evaluation tests will be carried out under another R&D program supported through the Advanced Detector Research (ADR) from the Department of Energy. Characterization tests on the first prototype serializer, LOC1, have been carried out in lab. Based on the lessons learned from this chip, we propose a new architecture design of the second prototype, LOC2, aiming for a serial data rate in the range of 5 Gbps. Simulation on key components of LOC2 are being carried out and the results we have so far are presented in this note. LOC2 is scheduled to be submitted for fabrication in the first half of 2009.