Terahertz spin-orbital excitations in the paramagnetic state of multiferroic Sr2FeSi2O7

We studied the novel multiferroic material Sr2FeSi2O7 and found three absorption modes above the magnetic ordering transition temperature using time-domain terahertz spectroscopy. These absorption modes can be explained as the optical transitions between the spin-orbit coupling and crystal-field split 3d(6) Fe2+ ground-state term in this material. Consideration of the compressed tetrahedral environment of the Fe2+ site is crucial to understand the excitations. We point out, however, discrepancies between the single-site atomic picture and the experimental results.1133Ysciescopu

Light MSSM Higgs boson mass to three-loop accuracy

The light CP even Higgs boson mass, Mh, is calculated to three-loop accuracy within the Minimal Supersymmetric Standard Model (MSSM). The result is expressed in terms of DRbar parameters and implemented in the computer program H3m. The calculation is based on the proper approximations and their combination in various regions of the parameter space. The three-loop effects to Mh are typically of the order of a few hundred MeV and opposite in sign to the two-loop corrections. The remaining theory uncertainty due to higher order perturbative corrections is estimated to be less than 1 GeV.Comment: 39 pages, 13 figures. v2: minor changes, typos fixe

Higgs production as a probe of anomalous top couplings

The LHC may be currently seeing the first hints of the Higgs boson. The dominant production mode for the Higgs at the LHC involves a top-quark loop. An accurate measurement of Higgs production cross-sections and decay widths can thus be used to obtain limits on anomalous top couplings. We find that such an exercise could potentially yield constraints that are stronger than those derived from low-energy observables as well as direct bounds expected from the top pair-production process.Comment: Version published in JHE

The Custodial Randall-Sundrum Model: From Precision Tests to Higgs Physics

We reexamine the Randall-Sundrum (RS) model with enlarged gauge symmetry SU(2)_L x SU(2)_R x U(1)_X x P_LR in the presence of a brane-localized Higgs sector. In contrast to the existing literature, we perform the Kaluza-Klein (KK) decomposition within the mass basis, which avoids the truncation of the KK towers. Expanding the low-energy spectrum as well as the gauge couplings in powers of the Higgs vacuum expectation value, we obtain analytic formulas which allow for a deep understanding of the model-specific protection mechanisms of the T parameter and the left-handed Z-boson couplings. In particular, in the latter case we explain which contributions escape protection and identify them with the irreducible sources of P_LR symmetry breaking. We furthermore show explicitly that no protection mechanism is present in the charged-current sector confirming existing model-independent findings. The main focus of the phenomenological part of our work is a detailed discussion of Higgs-boson couplings and their impact on physics at the CERN Large Hadron Collider. For the first time, a complete one-loop calculation of all relevant Higgs-boson production and decay channels is presented, incorporating the effects stemming from the extended electroweak gauge-boson and fermion sectors.Comment: 74 pages, 13 figures, 3 tables. v2: Matches version published in JHE

Genetic prediction of complex traits: integrating infinitesimal and marked genetic effects

Genetic prediction for complex traits is usually based on models including individual (infinitesimal) or marker effects. Here, we concentrate on models including both the individual and the marker effects. In particular, we develop a ''Mendelian segregation'' model combining infinitesimal effects for base individuals and realized Mendelian sampling in descendants described by the available DNA data. The model is illustrated with an example and the analyses of a public simulated data file. Further, the potential contribution of such models is assessed by simulation. Accuracy, measured as the correlation between true (simulated) and predicted genetic values, was similar for all models compared under different genetic backgrounds. As expected, the segregation model is worthwhile when markers capture a low fraction of total genetic variance. (Résumé d'auteur

Collaborative Enhancement of Antibody Binding to Distinct PECAM-1 Epitopes Modulates Endothelial Targeting

Antibodies to platelet endothelial cell adhesion molecule-1 (PECAM-1) facilitate targeted drug delivery to endothelial cells by “vascular immunotargeting.” To define the targeting quantitatively, we investigated the endothelial binding of monoclonal antibodies (mAbs) to extracellular epitopes of PECAM-1. Surprisingly, we have found in human and mouse cell culture models that the endothelial binding of PECAM-directed mAbs and scFv therapeutic fusion protein is increased by co-administration of a paired mAb directed to an adjacent, yet distinct PECAM-1 epitope. This results in significant enhancement of functional activity of a PECAM-1-targeted scFv-thrombomodulin fusion protein generating therapeutic activated Protein C. The “collaborative enhancement” of mAb binding is affirmed in vivo, as manifested by enhanced pulmonary accumulation of intravenously administered radiolabeled PECAM-1 mAb when co-injected with an unlabeled paired mAb in mice. This is the first demonstration of a positive modulatory effect of endothelial binding and vascular immunotargeting provided by the simultaneous binding a paired mAb to adjacent distinct epitopes. The “collaborative enhancement” phenomenon provides a novel paradigm for optimizing the endothelial-targeted delivery of therapeutic agents

Precise measurement of the W-boson mass with the CDF II detector

We have measured the W-boson mass MW using data corresponding to 2.2/fb of integrated luminosity collected in proton-antiproton collisions at 1.96 TeV with the CDF II detector at the Fermilab Tevatron collider. Samples consisting of 470126 W->enu candidates and 624708 W->munu candidates yield the measurement MW = 80387 +- 12 (stat) +- 15 (syst) = 80387 +- 19 MeV. This is the most precise measurement of the W-boson mass to date and significantly exceeds the precision of all previous measurements combined

X-ray emission from the Sombrero galaxy: discrete sources

We present a study of discrete X-ray sources in and around the bulge-dominated, massive Sa galaxy, Sombrero (M104), based on new and archival Chandra observations with a total exposure of ~200 ks. With a detection limit of L_X = 1E37 erg/s and a field of view covering a galactocentric radius of ~30 kpc (11.5 arcminute), 383 sources are detected. Cross-correlation with Spitler et al.'s catalogue of Sombrero globular clusters (GCs) identified from HST/ACS observations reveals 41 X-rays sources in GCs, presumably low-mass X-ray binaries (LMXBs). We quantify the differential luminosity functions (LFs) for both the detected GC and field LMXBs, whose power-low indices (~1.1 for the GC-LF and ~1.6 for field-LF) are consistent with previous studies for elliptical galaxies. With precise sky positions of the GCs without a detected X-ray source, we further quantify, through a fluctuation analysis, the GC LF at fainter luminosities down to 1E35 erg/s. The derived index rules out a faint-end slope flatter than 1.1 at a 2 sigma significance, contrary to recent findings in several elliptical galaxies and the bulge of M31. On the other hand, the 2-6 keV unresolved emission places a tight constraint on the field LF, implying a flattened index of ~1.0 below 1E37 erg/s. We also detect 101 sources in the halo of Sombrero. The presence of these sources cannot be interpreted as galactic LMXBs whose spatial distribution empirically follows the starlight. Their number is also higher than the expected number of cosmic AGNs (52+/-11 [1 sigma]) whose surface density is constrained by deep X-ray surveys. We suggest that either the cosmic X-ray background is unusually high in the direction of Sombrero, or a distinct population of X-ray sources is present in the halo of Sombrero.Comment: 11 figures, 5 tables, ApJ in pres