Oblique Parameter Constraints on Large Extra Dimensions

We consider the Kaluza-Klein scenario in which gravity propagates in the $4+n$ dimensional bulk of spacetime and the Standard Model particles are confined to a 3-brane. We calculate the gauge boson self-energy corrections arising from the exchange of virtual gravitons and present our results in the $STU$-formalism. We find that the new physics contributions to $S$, $T$ and $U$ decouple in the limit that the string scale $M_S$ goes to infinity. The oblique parameters constrain the lower limit on $M_S$. Taking the quantum gravity cutoff to be $M_S$, $S$-parameter constraints impose $M_S>1.55$ TeV for $n=2$ at the 1$\sigma$ level. $T$-parameter constraints impose $M_S>1.25 (0.75)$ TeV for $n=3 (6)$.Comment: Version to appear in PR

Gut mobilization improves behavioral symptoms and modulates urinary p-cresol in chronically constipated autistic children: A prospective study

Chronic constipation is common among children with ASD and is associated with more severe hyperactivity, anxiety, irritability, and repetitive behaviors. Young autistic children with chronic constipation display higher urinary, and foecal concentrations of p-cresol, an aromatic compound produced by gut bacteria, known to negatively affect brain function. Acute p-cresol administration to BTBR mice enhances anxiety, hyperactivity and stereotypic behaviors, while blunting social interaction. This study was undertaken to prospectively assess the behavioral effects of gut mobilization in young autistic children with chronic constipation, and to verify their possible correlation with urinary p-cresol. To this aim, 21 chronically constipated autistic children 2–8 years old were evaluated before (T0), 1 month (T1), and 6 months (T2) after intestinal mobilization, recording Bristol stool scale scores, urinary p-cresol concentrations, and behavioral scores for social interaction deficits, stereotypic behaviors, anxiety, and hyperactivity. Gut mobilization yielded a progressive and highly significant decrease in all behavioral symptoms over the 6-month study period. Urinary p-cresol levels displayed variable trends not significantly correlated with changes in behavioral parameters, mainly increasing at T1 and decreasing at T2. These results support gut mobilization as a simple strategy to ameliorate ASD symptoms, as well as comorbid anxiety and hyperactivity, in chronically constipated children. Variation in p-cresol absorption seemingly provides limited contributions, if any, to these behavioral changes. Further research will be needed to address the relative role of reduced abdominal discomfort following mobilization, as compared to specific modifications in microbiome composition and in gut bacteria-derived neuroactive compounds

Indirect Collider Signals for Extra Dimensions

A recent suggestion that quantum gravity may become strong near the weak scale has several testable consequences. In addition to probing for the new large (submillimeter) extra dimensions associated with these theories via gravitational experiments, one could search for the Kaluza Klein towers of massive gravitons which are predicted in these models and which can interact with the fields of the Standard Model. Here we examine the indirect effects of these massive gravitons being exchanged in fermion pair production in \epem annihilation and Drell-Yan production at hadron colliders. In the latter case, we examine a novel feature of this theory, which is the contribution of gluon gluon initiated processes to lepton pair production. We find that these processes provide strong bounds, up to several TeV, on the string scale which are essentially independent of the number of extra dimensions. In addition, we analyze the angular distributions for fermion pair production with spin-2 graviton exchanges and demonstrate that they provide a smoking gun signal for low-scale quantum gravity which cannot be mimicked by other new physics scenarios.Comment: Corrected typos, added table and reference

Mediation of supersymmetry breaking in extra dimensions

We review the mechanisms of supersymmetry breaking mediation that occur in sequestered models, where the visible and the hidden sectors are separated by an extra dimension and communicate only via gravitational interactions. By locality, soft breaking terms are forbidden at the classical level and reliably computable within an effective field theory approach at the quantum level. We present a self-contained discussion of these radiative gravitational effects and the resulting pattern of soft masses, and give an overview of realistic model building based on this set-up. We consider both flat and warped extra dimensions, as well as the possibility that there be localized kinetic terms for the gravitational fields.Comment: LaTex, 15 pages; brief review prepared for MPLA. v2: minor correction

Compact Hyperbolic Extra Dimensions: Branes, Kaluza-Klein Modes and Cosmology

We reconsider theories with low gravitational (or string) scale M_* where Newton's constant is generated via new large-volume spatial dimensions, while Standard Model states are localized to a 3-brane. Utilizing compact hyperbolic manifolds (CHM's) we show that the spectrum of Kaluza-Klein (KK) modes is radically altered. This allows an early universe cosmology with normal evolution up to substantial temperatures, and completely negates the constraints on M_* arising from astrophysics. Furthermore, an exponential hierarchy between the usual Planck scale and the true fundamental scale of physics can emerge with only order unity coefficients. The linear size of the internal space remains small. The proposal has striking testable signatures.Comment: 4 pages, no figure

Loop-Effects in Pseudo-Supersymmetry

We analyze the transmission of supersymmetry breaking in brane-world models of pseudo-supersymmetry. In these models two branes preserve different halves of the bulk supersymmetry. Thus supersymmetry is broken although each sector of the model is supersymmetric when considered separately. The world-volume theory on one brane feels the breakdown of supersymmetry only through two-loop interactions involving a coupling to fields from the other brane. In a 5D toy model with bulk vectors, we compute the diagrams that contribute to scalar masses on one brane and find that the masses are proportional to the compactification scale up to logarithmic corrections, m^2 ~ (2 pi R)^{-2}(ln(2 pi R ms)-1.1), where ms is an ultraviolet cutoff. Thus, for large compactification radii, where this result is valid, the brane scalars acquire a positive mass squared. We also compute the three-loop diagrams relevant to the Casimir energy between the two branes and find E ~ (2 pi R)^{-4}((ln(2 pi R ms)-1.7)^2+0.2). For large radii, this yields a repulsive Casimir force.Comment: Latex, 30 pages, 6 figures, v2: minor corrections, comments on susy algebra and x^5 covariant derivative adde

Exponentially Small Supersymmetry Breaking from Extra Dimensions

The supersymmetric ``shining'' of free massive chiral superfields in extra dimensions from a distant source brane can trigger exponentially small supersymmetry breaking on our brane of order e^{-2 pi R}, where R is the radius of the extra dimensions. This supersymmetry breaking can be transmitted to the superpartners in a number of ways, for instance by gravity or via the standard model gauge interactions. The radius R can easily be stabilized at a size O(10) larger that the fundamental scale. The models are extremely simple, relying only on free, classical bulk dynamics to solve the hierarchy problem.Comment: RevTex, 1 figure. Comment on mu problem adde

Supergravity loop contributions to brane world supersymmetry breaking

We compute the supergravity loop contributions to the visible sector scalar masses in the simplest 5D `brane-world' model. Supersymmetry is assumed to be broken away from the visible brane and the contributions are UV finite due to 5D locality. We perform the calculation with N = 1 supergraphs, using a formulation of 5D supergravity in terms of N = 1 superfields. We compute contributions to the 4D effective action that determine the visible scalar masses, and we find that the mass-squared terms are negative.Comment: 12 pages, LaTeX 2

An improved method on stimulated T-lymphocytes to functionally characterize novel and known LDLR mutations.

The main causes of familial hypercholesterolemia (FH) are mutations in LDL receptor (LDLR) gene. Functional studies are necessary to demonstrate the LDLR function impairment caused by mutations and would be useful as a diagnostic tool if they allow discrimination between FH patients and controls. In order to identify the best method to detect LDLR activity, we compared continuous Epstein-Barr virus (EBV)-transformed B-lymphocytes and mitogen stimulated T-lymphocytes. In addition, we characterized both novel and known mutations in the LDLR gene. T-lymphocytes and EBV-transformed B-lymphocytes were obtained from peripheral blood of 24 FH patients and 24 control subjects. Functional assays were performed by incubation with fluorescent LDL followed by flow cytometry analysis. Residual LDLR activity was calculated normalizing fluorescence for the mean fluorescence of controls. With stimulated T-lymphocytes we obtained a better discrimination capacity between controls and FH patients compared with EBV-transformed B-lymphocytes as demonstrated by receiver operating characteristic (ROC) curve analysis (the areas under the curve are 1.000 and 0.984 respectively; P < 0.0001 both). The characterization of LDLR activity through T-lymphocytes is more simple and faster than the use of EBV-transformed B-lymphocytes and allows a complete discrimination between controls and FH patients. Therefore the evaluation of residual LDLR activity could be helpful not only for mutation characterization but also for diagnostic purposes

TOPS project: Development of new fast timing plastic scintillators.

In particle physics charged particles are measured exploiting many different detection strategies. The plastic scintillators are cheap, versatile and show good time response, thus are traditionally employed as timing detectors. TOPS (Time Of flight Plastic Scintillators) is an R&amp;D project devoted to the synthesis and characterization of a novel class of plastic scintillators. Liquid and solid sam- ples of tens of new scintillators have been tested and characterized. Some of them (2N, 1N, 2B, P2, T2) have shown a larger light output with respect to antracene, a standard benchmark material, and good timing properties. In order to improve the matching between the scintillators emission and the optimal trasmittive region in the absorption spectra, a doping material has been added as wave-shifter. The use of POPOP as doping improved the performances of a fraction of the scintillator samples. Based on the comparison of the light output values in measurements with cosmic rays, a selection of the most promising scintillators has been investigated also from the timing point of view. The scintillation time characteristics of the TOPS plastic samples have been studied with minimum ionizing particles using a commercial plastic scintillator BC-412 as a reference. The light output and timing properties have been also investigated with proton beams at different energies (70, 120, 170, 220 MeV) and show promising results providing a time of flight measure- ments accuracy of 150–300ps. In this contribution, preliminary results obtained with this new class of scintillators developed in the TOPS project will be presented