Flavor Mediation Delivers Natural SUSY

If supersymmetry (SUSY) solves the hierarchy problem, then naturalness considerations coupled with recent LHC bounds require non-trivial superpartner flavor structures. Such "Natural SUSY" models exhibit a large mass hierarchy between scalars of the third and first two generations as well as degeneracy (or alignment) among the first two generations. In this work, we show how this specific beyond the standard model (SM) flavor structure can be tied directly to SM flavor via "Flavor Mediation". The SM contains an anomaly-free SU(3) flavor symmetry, broken only by Yukawa couplings. By gauging this flavor symmetry in addition to SM gauge symmetries, we can mediate SUSY breaking via (Higgsed) gauge mediation. This automatically delivers a natural SUSY spectrum. Third-generation scalar masses are suppressed due to the dominant breaking of the flavor gauge symmetry in the top direction. More subtly, the first-two-generation scalars remain highly degenerate due to a custodial U(2) symmetry, where the SU(2) factor arises because SU(3) is rank two. This custodial symmetry is broken only at order (m_c/m_t)^2. SUSY gauge coupling unification predictions are preserved, since no new charged matter is introduced, the SM gauge structure is unaltered, and the flavor symmetry treats all matter multiplets equally. Moreover, the uniqueness of the anomaly-free SU(3) flavor group makes possible a number of concrete predictions for the superpartner spectrum.Comment: 17 pages, 7 figures, 2 tables. v2 references added, minor changes to flavor constraints and a little discussion adde

The Hubble Space Telescope Treasury Program on the Orion Nebula Cluster

The Hubble Space Telescope (HST) Treasury Program on the Orion Nebula Cluster has used 104 orbits of HST time to image the Great Orion Nebula region with the Advanced Camera for Surveys (ACS), the Wide-Field/Planetary Camera 2 (WFPC2) and the Near Infrared Camera and Multi Object Spectrograph (NICMOS) instruments in 11 filters ranging from the U-band to the H-band equivalent of HST. The program has been intended to perform the definitive study of the stellar component of the ONC at visible wavelengths, addressing key questions like the cluster IMF, age spread, mass accretion, binarity and cirumstellar disk evolution. The scanning pattern allowed to cover a contiguous field of approximately 600 square arcminutes with both ACS and WFPC2, with a typical exposure time of approximately 11 minutes per ACS filter, corresponding to a point source depth AB(F435W) = 25.8 and AB(F775W)=25.2 with 0.2 magnitudes of photometric error. We describe the observations, data reduction and data products, including images, source catalogs and tools for quick look preview. In particular, we provide ACS photometry for 3399 stars, most of them detected at multiple epochs, WFPC2 photometry for 1643 stars, 1021 of them detected in the U-band, and NICMOS JH photometry for 2116 stars. We summarize the early science results that have been presented in a number of papers. The final set of images and the photometric catalogs are publicly available through the archive as High Level Science Products at the STScI Multimission Archive hosted by the Space Telescope Science Institute.Comment: Accepted for publication on the Astrophysical Journal Supplement Series, March 27, 201

The Spectrum of Goldstini and Modulini

When supersymmetry is broken in multiple sectors via independent dynamics, the theory furnishes a corresponding multiplicity of "goldstini" degrees of freedom which may play a substantial role in collider phenomenology and cosmology. In this paper, we explore the tree-level mass spectrum of goldstini arising from a general admixture of F-term, D-term, and almost no-scale supersymmetry breaking, employing non-linear superfields and a novel gauge fixing for supergravity discussed in a companion paper. In theories of F-term and D-term breaking, goldstini acquire a mass which is precisely twice the gravitino mass, while the inclusion of no-scale breaking renders one of these modes, the modulino, massless. We argue that the vanishing modulino mass can be explained in terms of an accidental and spontaneously broken "global" supersymmetry.Comment: 10 pages, 2 figures; v2: typo corrected, references updated; v3: version to appear in JHE

Solitonic supersymmetry restoration

Q-balls are a possible feature of any model with a conserved, global U(1) symmetry and no massless, charged scalars. It is shown that for a broad class of models of metastable supersymmetry breaking they are extremely influential on the vacuum lifetime and make seemingly viable vacua catastrophically short lived. A net charge asymmetry is not required as there is often a significant range of parameter space where statistical fluctuations alone are sufficient. This effect is examined for two supersymmetry breaking scenarios. It is found that models of minimal gauge mediation (which necessarily have a messenger number U(1)) undergo a rapid, supersymmetry restoring phase transition unless the messenger mass is greater than 10^8 GeV. Similarly the ISS model, in the context of direct mediation, quickly decays unless the perturbative superpotential coupling is greater than the Standard Model gauge couplings.Comment: 17 pages, 3 figures, minor comments added, accepted for publication in JHE

Ab-initio calculation of the electronic and optical excitations in polythiophene: effects of intra- and interchain screening

We present an calculation of the electronic and optical excitations of an isolated polythiophene chain as well as of bulk polythiophene. We use the GW approximation for the electronic self-energy and include excitonic effects by solving the electron-hole Bethe-Salpeter equation. The inclusion of interchain screening in the case of bulk polythiophene drastically reduces both the quasi-particle band gap and the exciton binding energies, but the optical gap is hardly affected. This finding is relevant for conjugated polymers in general.Comment: 4 pages, 1 figur

Deep MMT Transit Survey of the Open Cluster M37 IV: Limit on the Fraction of Stars With Planets as Small as 0.3 R_J

We present the results of a deep (15 ~< r ~< 23), 20 night survey for transiting planets in the intermediate age open cluster M37 (NGC 2099) using the Megacam wide-field mosaic CCD camera on the 6.5m MMT. We do not detect any transiting planets among the ~1450 observed cluster members. We do, however, identify a ~ 1 R_J candidate planet transiting a ~ 0.8 Msun Galactic field star with a period of 0.77 days. The source is faint (V = 19.85 mag) and has an expected velocity semi-amplitude of K ~ 220 m/s (M/M_J). We conduct Monte Carlo transit injection and recovery simulations to calculate the 95% confidence upper limit on the fraction of cluster members and field stars with planets as a function of planetary radius and orbital period. Assuming a uniform logarithmic distribution in orbital period, we find that < 1.1%, < 2.7% and < 8.3% of cluster members have 1.0 R_J planets within Extremely Hot Jupiter (EHJ, 0.4 < T < 1.0 day), Very Hot Jupiter (VHJ, 1.0 < T < 3.0 days) and Hot Jupiter (HJ, 3.0 < T < 5.0 days) period ranges respectively. For 0.5 R_J planets the limits are < 3.2%, and < 21% for EHJ and VHJ period ranges, while for 0.35 R_J planets we can only place an upper limit of < 25% on the EHJ period range. For a sample of 7814 Galactic field stars, consisting primarily of FGKM dwarfs, we place 95% upper limits of < 0.3%, < 0.8% and < 2.7% on the fraction of stars with 1.0 R_J EHJ, VHJ and HJ assuming the candidate planet is not genuine. If the candidate is genuine, the frequency of ~ 1.0 R_J planets in the EHJ period range is 0.002% < f_EHJ < 0.5% with 95% confidence. We place limits of < 1.4%, < 8.8% and < 47% for 0.5 R_J planets, and a limit of < 16% on 0.3 R_J planets in the EHJ period range. This is the first transit survey to place limits on the fraction of stars with planets as small as Neptune.Comment: 61 pages, 19 figures, 5 tables, replaced with the version accepted for publication in Ap

Collider signatures of goldstini in gauge mediation

We investigate the collider signatures of the multiple goldstini scenario in the framework of gauge mediation. This class of models is characterized by a visible sector (e.g. the MSSM or any extension) coupled by gauge interactions to more than one SUSY breaking sector. The spectrum consists of a light gravitino LSP, behaving as a goldstino, and a number of neutral fermions (the pseudo-goldstini) with a mass between that of the LSP and that of the lightest particle of the observable sector (LOSP). We consider the two situations where the LOSP is either a gaugino-like neutralino or a stau and we assume only one pseudo-goldstino of a mass of O(100) GeV. The coupling of the LOSP to the pseudo-goldstino can be enhanced with respect to those of the gravitino giving rise to characteristic signatures. We show that the decay modes of the LOSP into a SM particle and a pseudo-goldstino can be significant. For both LOSP scenarios we analyze (pseudo)-goldstini production at colliders. Compared to standard gauge mediation the final state spectrum is softer and more structured.Comment: v2: analysis of the stau LOSP scenario added, sections rearranged, and Introduction and Conclusions rewritten to include the added scenario. Version to appear in JHE

Pathways to ischemic neuronal cell death: are sex differences relevant?

We have known for some time that the epidemiology of human stroke is sexually dimorphic until late in life, well beyond the years of reproductive senescence and menopause. Now, a new concept is emerging: the mechanisms and outcome of cerebral ischemic injury are influenced strongly by biological sex as well as the availability of sex steroids to the brain. The principal mammalian estrogen (17 β estradiol or E2) is neuroprotective in many types of brain injury and has been the major focus of investigation over the past several decades. However, it is becoming increasingly clear that although hormones are a major contributor to sex-specific outcomes, they do not fully account for sex-specific responses to cerebral ischemia. The purpose of this review is to highlight recent studies in cell culture and animal models that suggest that genetic sex determines experimental stroke outcome and that divergent cell death pathways are activated after an ischemic insult. These sex differences need to be identified if we are to develop efficacious neuroprotective agents for use in stroke patients

Sediment-laden sea ice in southern Hudson Bay: Entrainment, transport, and biogeochemical implications

During a research expedition in Hudson Bay in June 2018, vast areas of thick (>10 m), deformed sediment-laden sea ice were encountered unexpectedly in southern Hudson Bay and presented difficult navigation conditions for the Canadian Coast Guard Ship Amundsen. An aerial survey of one of these floes revealed a maximum ridge height of 4.6 m and an average freeboard of 2.2 m, which corresponds to an estimated total thickness of 18 m, far greater than expected within a seasonal ice cover. Samples of the upper portion of the ice floe revealed that it was isothermal and fresh in areas with sediment present on the surface. Fine-grained sediment and larger rocks were visible on the ice surface, while a pronounced sediment band was observed in an ice core. Initial speculation was that this ice had formed in the highly dynamic Nelson River estuary from freshwater, but δ^{18}O isotopic analysis revealed a marine origin. In southern Hudson Bay, significant tidal forcing promotes both sediment resuspension and new ice formation within a flaw lead, which we speculate promotes the formation of this sediment-laden sea ice. Historic satellite imagery shows that sediment-laden sea ice is typical of southern Hudson Bay, varying in areal extent from 47 to 118 km2 during June. Based on an average sediment particle concentration of 0.1 mg mL^{–1} in sea ice, an areal extent of 51,924 km2 in June 2018, and an estimated regional end-of-winter ice thickness of 1.5 m, we conservatively estimated that a total sediment load of 7.8 × 106 t, or 150 t km^{–2}, was entrained within sea ice in southern Hudson Bay during winter 2018. As sediments can alter carbon concentrations and light transmission within sea ice, these first observations of this ice type in Hudson Bay imply biogeochemical impacts for the marine system

Operator theory and function theory in Drury-Arveson space and its quotients

The Drury-Arveson space $H^2_d$, also known as symmetric Fock space or the $d$-shift space, is a Hilbert function space that has a natural $d$-tuple of operators acting on it, which gives it the structure of a Hilbert module. This survey aims to introduce the Drury-Arveson space, to give a panoramic view of the main operator theoretic and function theoretic aspects of this space, and to describe the universal role that it plays in multivariable operator theory and in Pick interpolation theory.Comment: Final version (to appear in Handbook of Operator Theory); 42 page