14532209
Split extended supersymmetry from intersecting branes
Abstract We study string realizations of split extended supersymmetry, recently proposed in [I. Antoniadis, et al. hep-ph/0507192 ]. Supersymmetry is broken by small (ϵ) deformations of intersection angles of D-branes giving tree-level masses of order m 0 2 ∼ ϵ M s 2 , where M s is the string scale, to localized scalars. We show through an explicit one-loop string amplitude computation that gauginos acquire hierarchically smaller Dirac masses m 1 / 2 D ∼ m 0 2 / M s . We also evaluate the one-loop higgsino mass, μ , and show that, in the absence of tree-level contributions, it behaves as μ ∼ m 0 4 / M s 3 . Finally we discuss an alternative suppression of scales using large extra dimensions. The latter is illustrated, for the case where the gauge bosons appear in N = 4 representations, by an explicit string model with Standard Model gauge group, three generations of quarks and leptons and gauge coupling unification.
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.
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.
118980897
Two-loop Higgs mass in supersymmetric Kaluza-Klein theories
We perform an explicit two-loop computation of the Higgs mass in a five-dimensional supersymmetric theory compactified on the orbifold S^1/Z_2, with superpotential localized on a fixed-point brane and supersymmetry broken in the bulk of the extra dimension by Scherk-Schwarz boundary conditions. At one-loop, the Higgs mass is finite and proportional to 1/R^2, R being the radius of the extra dimension. The two-loop corrections contain finite proportional to 1/R^2 and linearly divergent Lambda/R terms, where Lambda is the cutoff of the five-dimensional theory. The divergent terms are cancelled by diagrams containing one-loop wave-function renormalization counterterms, i.e. by linear threshold effects of Yukawa (and gauge) couplings, at the scale 1/R. As a result there is no counterterm for the Higgs mass, which is finite and calculable to the considered order.
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.
15082396
Multiwavelength Analysis of the Young Open Cluster NGC 2362
We present a multiwavelength analysis of the young open cluster NGC 2362; UBVRCIC CCD photometric observations, together with available data in the Chandra database, near-infrared data from the Two Micron All Sky Survey (2MASS), and recently published Hα spectroscopy were used to get information about the evolutionary stage of the cluster and the main physical properties of its stellar content. Cluster membership is estimated for every individual star by means of zero-age main sequence (ZAMS) and isochrone fitting. The cluster is confirmed to host a rich population of pre-main-sequence (PMS) objects and to contain a large number of X-ray-emitting stars, which reach from the PMS members of GK spectral type up to the most luminous OB main-sequence (MS) members. The PMS cluster members show no significant age spread, and the comparison to both PMS and post-MS isochrones suggests an homogeneous age for all cluster members. The analysis allows us to assess the validity of currently used PMS evolutionary models and supports the suggestion of a well-defined positive correlation of the X-ray emission from PMS stars with their bolometric luminosity. Clear differences are found between the X-ray activity properties of MS and PMS cluster members, both in the relation between X-ray luminosity and bolometric luminosity, and in spectral properties as well.
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