Multijet Discriminators for New Physics in Leptonic Signals at the LHC

Some of the cleanest signals for new physics in the early runs of the LHC will involve strongly-produced particles which give rise to multiple leptons by undergoing cascade decays through weakly-interacting states to stable particles. Some of the most spectacular final states will involve three or more leptons, multiple jets and generally missing energy-momentum as well. A triad of the most interesting models of new physics which induce such signals is known to consist of (i) supersymmetry with R-parity conservation, (ii) a universal extra dimension with conservation of KK-parity and (iii) little Higgs models with conserved T-parity. Similar signals could also arise if the Standard Model is augmented with a fourth sequential generation of heavy fermions. We study all these possibilities and show that a judiciously chosen set of observables, critically involving the number of identifiable jets and leptons, can collectively provide distinct footprints for each of these models. In fact, simple pairwise correlation of such observables can enable unambiguous identification of the underlying model, even with a relatively small data sample.Comment: 43 pages, LaTex2e, 8 embedded eps figure

The PseudoDojo: Training and grading a 85 element optimized norm-conserving pseudopotential table

First-principles calculations in crystalline structures are often performed with a planewave basis set. To make the number of basis functions tractable two approximations are usually introduced: core electrons are frozen and the diverging Coulomb potential near the nucleus is replaced by a smoother expression. The norm-conserving pseudopotential was the first successful method to apply these approximations in a fully ab initio way. Later on, more efficient and more exact approaches were developed based on the ultrasoft and the projector augmented wave formalisms. These formalisms are however more complex and developing new features in these frameworks is usually more difficult than in the norm-conserving framework. Most of the existing tables of norm- conserving pseudopotentials, generated long ago, do not include the latest developments, are not systematically tested or are not designed primarily for high accuracy. In this paper, we present our PseudoDojo framework for developing and testing full tables of pseudopotentials, and demonstrate it with a new table generated with the ONCVPSP approach. The PseudoDojo is an open source project, building on the AbiPy package, for developing and systematically testing pseudopotentials. At present it contains 7 different batteries of tests executed with ABINIT, which are performed as a function of the energy cutoff. The results of these tests are then used to provide hints for the energy cutoff for actual production calculations. Our final set contains 141 pseudopotentials split into a standard and a stringent accuracy table. In total around 70.000 calculations were performed to test the pseudopotentials. The process of developing the final table led to new insights into the effects of both the core-valence partitioning and the non-linear core corrections on the stability, convergence, and transferability of norm-conserving pseudopotentials. ...Comment: abstract truncated, 17 pages, 25 figures, 8 table

Side-Information For Steganography Design And Detection

Today, the most secure steganographic schemes for digital images embed secret messages while minimizing a distortion function that describes the local complexity of the content. Distortion functions are heuristically designed to predict the modeling error, or in other words, how difficult it would be to detect a single change to the original image in any given area. This dissertation investigates how both the design and detection of such content-adaptive schemes can be improved with the use of side-information. We distinguish two types of side-information, public and private: Public side-information is available to the sender and at least in part also to anybody else who can observe the communication. Content complexity is a typical example of public side-information. While it is commonly used for steganography, it can also be used for detection. In this work, we propose a modification to the rich-model style feature sets in both spatial and JPEG domain to inform such feature sets of the content complexity. Private side-information is available only to the sender. The previous use of private side-information in steganography was very successful but limited to steganography in JPEG images. Also, the constructions were based on heuristic with little theoretical foundations. This work tries to remedy this deficiency by introducing a scheme that generalizes the previous approach to an arbitrary domain. We also put forward a theoretical investigation of how to incorporate side-information based on a model of images. Third, we propose to use a novel type of side-information in the form of multiple exposures for JPEG steganography

Planet Formation in Binary Stars: The case of Gamma Cephei

Over 30 planetary systems have been discovered to reside in binary stars. For small separations gravitational perturbation of the secondary star has a strong influence on the planet formation process. It truncates the protoplanetary disk, may shortens its lifetime, and stirs up the embedded planetesimals. Due to its small semi-major axis (18.5 AU) and large eccentricity (e=0.35) the binary $\gamma$ Cephei represents a particularly challenging example. In the present study we model the orbital evolution and growth of embedded protoplanetary cores of about 30 earth masses in the putative protoplanetary disk surrounding the primary star in the $\gamma$ Cep system. We assume coplanarity of the disk, binary and planet and perform two-dimensional hydrodynamic simulations of embedded cores in a protoplanetary disk. The presence of the eccentric secondary star perturbs the disk periodically and generates strong spiral arms at periapse which propagate toward the disk centre. The disk also becomes slightly eccentric (with e_d = 0.1-0.15), and displays a slow retrograde precession in the inertial frame. For all initial separations (2.5 to 3.5 AU) we find inward migration of the cores. For initial semi-major axes (a_p \gsim 2.7), we find a strong increase in the planetary eccentricity despite the presence of inward migration. Only cores which are initially far from the disk outer edge have a bounded orbital eccentricity which converges, roughly to the value of the planet observed in the $\gamma$ Cep system. We have shown that under the condition protoplanetary cores can form at around 2.5 AU, it is possible to evolve and grow such a core to form a planet with final outcome similar to that observed.Comment: 12 pages, 17 figures, accepted by Astronomy & Astrophysic

Risk factors associated with healthcare utilization for spine pain

OBJECTIVE: This study examined potential risk factors associated with healthcare utilization among patients with spine (i.e., neck and back) pain. METHODS: A two-stage sampling approach examined spine pain episodes of care among veterans with a yearly outpatient visit for six consecutive years. Descriptive and bivariate statistics, followed by logistic regression analyses, examined baseline characteristics of veterans with new episodes of care who either continued or discontinued spine pain care. A multivariable logistic regression model examined correlates associated with seeking continued spine pain care. RESULTS: Among 331,908 veterans without spine pain episodes of care during the two-year baseline observation period, 16.5% (n = 54,852) had a new episode of care during the following two-year observation period. Of those 54,852 veterans, 37,025 had an outpatient visit data during the final two-year follow-up period, with 53.7% (n = 19,865) evidencing continued spine pain care. Those with continued care were more likely to be overweight or obese, non-smokers, Army veterans, have higher education, and had higher rates of diagnoses of all medical and mental health conditions examined at baseline. Among several important findings, women had 13% lower odds of continued care during the final two-year observation period, OR 0.87 (0.81, 0.95). CONCLUSIONS: A number of important demographics and clinical correlates were associated with increased likelihood of seeking new and continued episodes of care for spine pain; however, further examination of risk factors associated with healthcare utilization for spine pain is indicated