11130703
Fermion mass hierarchy from the soft wall
We develop a five-dimensional model for electroweak physics based on a noncompact warped extra dimension of finite length, known as the soft wall scenario, where all the dynamical degrees of freedom propagate in the five-dimensional bulk. We solve the equations of motion and find the allowed spectra, showing that the mass of the lightest fermionic mode behaves as a power law of the effective four-dimensional Yukawa coupling constant, with the exponent being the corresponding fermionic five-dimensional bulk mass. Precisely this nonuniversal behavior allows us to reproduce the hierarchy between the standard model fermion masses (from neutrinos to the top quark) with nonhierarchical fermionic bulk masses.
119113677
Cornering a hyper Higgs boson: Angular kinematics for boosted Higgs bosons with top pairs
In the wake of the Higgs discovery and over the long haul of the LHC run, one should keep a lookout for kinematic anomalies in the most massive known trio of coupled particles, $t \bar{t} h$. After surveying the scope of prior constraints on chromomagnetic dipole and Higgs-gluon kinetic couplings, we focus on surpluses of boosted-$p_T$ Higgs bosons fomented by these momentum dependent dimension-six operators in $t \bar{t} h$ final states. We uncover a number of simple, $p_T$ weighted angular variables useful for discriminating Standard Model from dimension-6 boosted Higgs distributions, and make headway arguing that one of these variables may improve the reach of existing Standard Model top-Higgs searches. The approach we take is model independent, because we just consider a set of effective operators that contribute to the same three-body final state.
14532761
Brane-assisted Scherk-Schwarz supersymmetry breaking in orbifolds
We have analyzed the interplay between Scherk-Schwarz supersymmetry breaking and general fermion (gaugino or gravitino) mass terms localized on the fixed point branes of the S1/2 orbifold. Analytic solutions for eigenfunctions and eigenvalues are found in all cases. All results are checked by numerical calculations that make use of regularized δ-functions. Odd and generically also even fermions are discontinuous at the brane fixed points, but in all cases the combination that couples to the brane is continuous. For CP-even brane mass terms supersymmetry restoration can take place when their effects are cancelled by those of Scherk-Schwarz compactification. However such a cancellation can not occur for CP-odd brane mass terms.
15511076
Gauge coupling renormalization in RS1
Abstract We compute the 4D low energy effective gauge coupling at one-loop order in the compact Randall–Sundrum scenario with bulk gauge fields and charged matter, within controlled approximations. While such computations are subtle, they can be important for studying phenomenological issues such as grand unification. Ultraviolet divergences are cut-off using Pauli–Villars regularization so as to respect 5D gauge and general coordinate invariance. The structure of these divergences on branes and in the bulk is elucidated by a 5D position-space analysis. The remaining finite contributions are obtained by a careful analysis of the Kaluza–Klein spectrum. We comment on the agreement between our results and expectations based on the AdS/CFT correspondence, in particular logarithmic sensitivity to the 4D Planck scale.
118541613
Electroweak and supersymmetry breaking from the Higgs boson discovery
We will explore the consequences on the electroweak breaking condition, the mass of supersymmetric partners and the scale at which supersymmetry breaking is transmit- ted, for arbitrary values of the supersymmetric parameters tanand the stop mixing Xt, which follow from the Higgs discovery with a mass mH ≃ 126 GeV at the LHC. Within the present uncertainty on the top quark mass we deduce that radiative break- ing requires tan� & 8 for maximal mixing Xt ≃ √ 6, and tan� & 20 for small mixing Xt . 1.8. The scale at which supersymmetry breaking is transmitted M can be of order the unification or Planck scale only for large values of tanand negligible mixing Xt ≃ 0. On the other hand for maximal mixing and large values of tansupersymme- try should break at scales as low as M ≃ 10 5 GeV. The uncertainty in those predictions stemming from the uncertainty in the top quark mass, i.e. the top Yukawa coupling, is small (large) for large (small) values of tan�. In fact for tan� = 1 the uncertainty on the value of M is several orders of magnitude.
119097432
The light stop window
We show that a right-handed stop in the 200–400 GeV mass range, together with a nearly degenerate neutralino and, possibly, a gluino below 1.5 TeV, follows from reasonable assumptions, is consistent with present data, and offers interesting discovery prospects at the LHC. Triggering on an extra jet produced in association with stops allows the experimental search for stops even when their mass difference with neutralinos is very small and the decay products are too soft for direct observation. Using a razor analysis, we are able to set stop bounds that are stronger than those published by ATLAS and CMS.
16422495
A young double stellar cluster in a HII region, emerging from its parent molecular cloud ⋆
Aims. We investigate the star formation occurring in the region towards IRAS 07141-0920 contained in the HII region Sh2-294 (S294). We report the discovery ��� of a new young double stellar cluster, and we describe its properties. Methods. High-resolution optical UBVRI and Hα images obtained with ALFOSC mounted on the Nordic Optical Telescope (NOT), near-infrared JHKS images obtained with NOTCam at the Nordic Optical Telescope, and VLT/ISAAC images obtained through the H2 (2.12 µm) filter were all used to make photometric and morphological studies of the point sources and the nebula seen towards Sh2-294. Identification of PMS members was done using three different methods: comparison with isochrones in optical colour−magnitude diagrams and detection of either near-IR excess or Hα emission. Results. The optical images reveal an emission nebula rich in morphological details. The nebula is composed mainly of ultraviolet scattered light and of Hα emission with local morphological features conveying an impression of strong dynamical complexity. Contrasting with the bright parts of the nebula, opaque patches are seen. They appear elongated, filamentary, or clumpy. Our optical photometry confirms that the identification of the illuminator of the nebula is likely to be a B0.5V star located at a distance of about 3.2 kpc. Our high-resolution near-IR images reveal an embedded cluster, extending about 2 pc and exhibiting sub-clustering: a denser, more condensed, subcluster surrounding the optical high-mass B0.5V illuminator star; and a more embedded, optically invisible, subcluster located towards the eastern, dark part of the nebula and including the luminous MSX source G224.1880+01.2407, a massive protostellar candidate that could be the origin of jets and extended features seen at 2.12 µm. The double cluster appears to be clearing the remaining molecular material of the parent cloud, creating patches of lower extinction and allowing some of the least reddened members to be detected in the optical images. We find 12 main-sequence (MS) and 143 pre-main sequence(PMS) members. The most massive star fits a 4 Myr, post-MS isochrone. The age of the optically selected PMS population is estimated to be 7− 8M yr. The IR-excess population shows sub-clustering on scales as small as 0.23 pc and is probably much younger.
73684220
Analysis of the stellar population in the central area of the HII region Sh 2-284
Context. There is a lack of state-of-the-art information on very young open clusters with implications for determining the structure of the Galaxy. Aims. Our main objective is to study the timing and location of the star formation processes which yielded the generation of the giant HII region Sh 2-284. This includes the determination of different physical variables of the stars, such as distance, reddening, age and evolutionary stage, including pre-main-sequence (PMS) stars. Methods. The analysis is based on UBVRCIC CCD measurements of a field of 6.5 � × 6.5 � containing the cluster, and JHKs photometry in the 3.5 � × 3.5 � subfield, centered in the apparent higher condensation. The determination of cluster distance, reddening and age is carried out through a comparison with ZAMS, post-MS and PMS isochrones. The reference lines used are obtained from theoretical post-MS and PMS isochrones from the Geneva and Yale groups for a metallicity of Z = 0.004, which agrees with the spectroscopic metallicity determination published for several cluster members. Results. The results amount to E(B −V) = 0.78 ± 0.02, DM = 12.8 ± 0.2 (3.6 kpc), Log Age(yr) = 6.51 ± 0.07 (3.2 Myr). The distance result critically depends on the use of low metallicity ZAMS and isochrones. A PMS member sequence is proposed, with an age of Log Age(yr) = 6.7 ± 0.2 (4.7 Myr) which is therefore coeval within the errors with the post-MS cluster age. The mass function for this