Coherent Radiative Parton Energy Loss beyond the BDMPS-Z Limit

It is widely accepted that a phenomenologically viable theory of jet quenching for heavy ion collisions requires the understanding of medium-induced parton energy loss beyond the limit of eikonal kinematics formulated by Baier-Dokshitzer-Mueller-Peigne-Schiff and Zakharov (BDMPS-Z). Here, we supplement a recently developed exact Monte Carlo implementation of the BDMPS-Z formalism with elementary physical requirements including exact energy-momentum conservation, a refined formulation of jet-medium interactions and a treatment of all parton branchings on the same footing. We document the changes induced by these physical requirements and we describe their kinematic origin.Comment: 8 pages, 4 figure

Estimating the COGARCH(1,1) model - a first go

We suggest moment estimators for the parameters of a continuous time GARCH(1,1) process based on equally spaced observations. Using the fact that the increments of the COGARCH(1,1) process are ergodic, the resulting estimators are consistent. We investigate the quality of our estimators in a simulation study based on the compound Poisson driven COGARCH model. The estimated volatility with corresponding residual analysis is also presented

Jet quenching pattern at LHC in PYQUEN model

The first LHC data on high transverse momentum hadron and dijet spectra in PbPb collisions at center-of-mass energy 2.76 TeV per nucleon pair are analyzed in the frameworks of PYQUEN jet quenching model. The presented studies for the nuclear modification factor of high-pT hadrons and the imbalance in dijet transverse energy support the supposition that the intensive wide-angular ("out-of-cone") medium-induced partonic energy loss is seen in central PbPb collisions at the LHC.Comment: 5 pages including 4 figures as EPS-files; prepared using LaTeX package for publication in the European Physical Journal

Design and Characterization of Surface‐Crosslinked Gelatin Nanoparticles for the Delivery of Hydrophilic Macromolecular Drugs

For nanotechnology enabled delivery of hydrophilic protein‐based drugs, several polymer‐based carrier systems have been used in the past to protect the sensitive load and to facilitate cellular uptake and crossing of biological barriers. This study uses gelatin, a natural and biodegradable macromolecule, as carrier material which is approved for several applications. Nanoprecipitation is used to form nanoparticles and to maintain the physicochemical integrity of gelatin, hydrophilic crosslinkers, e.g., paraformaldehyde, glutaraldehyde, carbodiimide, and transglutaminase are employed. However, these crosslinkers diffuse homogenously into the carrier matrix also crosslinking the polymeric matrix with the entrapped protein‐based molecules thus rendering it inactive. Hence a hydrophobic zero‐length crosslinker, diisopropylcarbodiimide, is applied to avoid diffusion into the particles. This will provide an opportunity to encapsulate protein‐based drugs in the non‐crosslinked matrix. The hypothesis of surface crosslinking is proven by the extent of crosslinking and more importantly by encapsulation and the release of lysozyme as a model hydrophilic protein. Furthermore, essential process parameters are evaluated such as crosslinker concentration, crosslinking time and crosslinking reaction temperature with regard to the effect on particle size, size distribution and zeta‐potential of gelatin nanoparticles. The optimum formulation results in the production of gelatin nanoparticles with 200‐300 nm and a polydispersity index < 0.2

What Threats to Human Health Does Space Radiation Pose in Orbit

The Space Shuttle program spanned more than the entire length of a solar cycle. Investigations aimed towards understanding the health risks of the astronauts from exposures to space radiation involved mostly physical measurements of the dose and the linear energy transfer (LET) spectrum. Measurement of the dose rate on the Shuttle provided invariable new data for different periods of the solar cycle, whereas measurement of the LET spectrum using the tissue equivalent proportional counter (TEPC) produced the most complete mapping of the radiation environment of the low Earth orbits (LEO). Exposures to the Shuttle astronauts were measured by the personal dosimeter worn by the crewmembers. Analysis of over 300 personal dosimeter readings indicated a dependence on the mission duration, the altitude and inclination of the orbit, and the solar cycle, with the crewmembers on the launch and repair of the Hubble telescope receiving the highest doses due to the altitude of the mission. Secondary neutrons inside the Shuttle were determined by recoil protons or with Bonner spheres, and may contribute significantly to the risks of the crewmembers. In addition, the skin dose and the doses received at different organs were compared using a human phantom onboard a Shuttle mission. A number of radiobiology investigations wer e also performed. The biological doses were determined on six astronauts/cosmonauts on long-duration Shuttle/Mir missions and on two crewmembers on a Hubble repair mission by analyzing the damages in the chromosomes of the crewmembers? white blood cells. Several experiments were also conducted to address the question of possible synergistic effects of spaceflight, microgravity in particular, on the repair of radiation-induced DNA damages. The experimental design included exposure of cells before launch, during flight, or after landing. These physical and biological studies were invaluable in predicting the health risks for astronauts on ISS and future exploration missions. Educational Objectives: A group of high school students flew color negative films on tw o Shuttle missions to detect the radiation environment in orbit. This and other experiments onboard of the Shuttle were aimed at educating the general public of the space program

Jets in QCD media: from color coherence to decoherence

We investigate soft gluon radiation off a quark-antiquark antenna in both color singlet and octet configurations traversing a dense medium. We demonstrate that, in both cases, multiple scatterings lead to a gradual decoherence of the antenna radiation as a function of the medium density. In particular, in the limit of an completely opaque medium, total decoherence is obtained, i.e., the quark and the antiquark radiate as independent emitters in vacuum, thus losing memory of their origin. We comment on possible implications on intrajet observables in heavy-ion collisions.Comment: 4 pages, 1 figur

Transport Theoretical Description of Collisional Energy Loss in Infinite Quark-Gluon Matter

We study the time evolution of a high-momentum gluon or quark propagating through an infinite, thermalized, partonic medium utilizing a Boltzmann equation approach. We calculate the collisional energy loss of the parton, study its temperature and flavor dependence as well as the the momentum broadening incurred through multiple interactions. Our transport calculations agree well with analytic calculations of collisional energy-loss where available, but offer the unique opportunity to address the medium response as well in a consistent fashion.Comment: 12 pages, updated with additional references and typos correcte

Estimation of group structures in panel models with individual fixed effects

The fixed effects (FE) panel model is one of the main econometric tools in empirical economic research. A major practical limitation is that the parameters on time-constant covariates are not identifiable. This paper presents a new approach to grouping FE in the linear panel model to reduce their dimensionality and ensure identifiability. By using unsupervised nonparametric density based clustering, cluster patterns including their location and number are not restricted. The approach works with large data structures (units and groups) and only clusters units that are sufficiently similar, while leaving others as unclustered atoms. Asymptotic theory and rates of convergence are presented. With the help of simulations and an application to economic data it is shown that the suggested method performs well and gives more insightful and efficient results than conventional panel models

Medium-induced emissions of hard gluons

We present a derivation of the medium-induced gluon radiation spectrum beyond the current limitation of soft gluon emission. Making use of the path integral approach to describe the propagation of high-energy particles inside a medium, we study the limiting case of a hard gluon emission. Analytical and numerical results are presented and discussed within the multiple soft scattering approximation. An ansatz interpolating between soft and hard gluon emissions is provided. The Landau-Pomeranchuk-Migdal effect is observed in the expected kinematic region.Comment: 17 pages, 6 figures. Minor corrections, references updated. Accepted by Phys. Lett.

Decoherence and energy loss in QCD cascades in nuclear collisions

The medium modifications in the properties of QCD cascades are considered. In particular, the changes in the intrajet rapidity distributions due to medium-induced decoherence, collisional losses of cascade gluons and those of final prehadrons are analyzed