New structures in the proton-antiproton system

In the most recent measurements of the reaction $e^+e^- \rightarrow p\bar{p}$ by the BABAR collaboration, new structures have been found with unknown origin. We examine a possible relation of the most distinct peak to the recently observed $\Phi(2170)$. Alternatively, we analyse possible explanations due to the nucleon$\,\bar{\Delta}$ and $\Delta\bar{\Delta}$ thresholds. The latter could explain a periodicity found in the data

B→γγB \to \gamma \gamma in an ACD model

We present a full calculation of the amplitudes for $B_{d[s]} \to \gamma \gamma$ in a simple ACD model that extends an incomplete one in a previous paper. We find cancellations between the contributions from different KK towers and a small decrease relative to the SM predictions. It is conjectured that radiative QCD corrections might actually lead to an enhancement in the branching ratios and {\bf CP} asymmetries, but no more than modest ones.Comment: 3 pages, 2 figure

Theoretical Constraints and Systematic Effects in the Determination of the Proton Form Factors

We calculate the two-photon exchange corrections to electron-proton scattering with nucleon and $\Delta$ intermediate states. The results show a dependence on the elastic nucleon and nucleon-$\Delta$-transition form factors used as input which leads to significant changes compared to previous calculations. We discuss the relevance of these corrections and apply them to the most recent and precise data set and world data from electron-proton scattering. Using this, we show how the form factor extraction from these data is influenced by the subsequent inclusion of physical constraints. The determination of the proton charge radius from scattering data is shown to be dominated by the enforcement of a realistic spectral function. Additionally, the third Zemach moment from the resulting form factors is calculated. The obtained radius and Zemach moment are shown to be consistent with Lamb shift measurements in muonic hydrogen.Comment: minor changes, added references, version to appear in PR

Modellierung zeitabhängiger 3D-Modelle in der Geotechnik

Aufgrund der steigenden quantitativen und qualitativen Anforderungen an den Bauplanungsprozeß wird in den letzten Jahren nach neuen Lösungsansätzen gesucht, mit deren Hilfe der Bauplanungsprozeß den gestiegenen Anforderungen angepaßt werden kann. Ein Lösungsansatz hierzu stellt die durchgängig computergestützte, dreidimensionale und zeitabhängige Modellierung und Verwaltung des Bauplanungsprozesses beginnend bei der Vorplanung bis hin zum Recycling des Bauobjektes am Ende seiner Lebensdauer dar. Der vorliegende Beitrag zeigt auf, daß gerade der zeitliche Verlauf innerhalb einer geotechnischen Aufgabenstellung einen nicht unerheblichen Einfluß auf die verwendeten Modelle bzw. die Durchführung von Sicherheitsnachweisen ausübt. Für die Entwicklung geotechnischer Softwaresysteme ergibt sich daraus schon innerhalb der Analysephase die Anforderung, die zeitkritischen Abhängigkeiten zu modellieren und entsprechend im Entwurf zu berücksichtigen. Hierfür hat sich die objektorientierte Methode in Form des Objektmodells und des dynamischen Modells nach Rumbaugh als ein geeignetes Werkzeug herausgestellt. Die dabei gewonnenen Erkenntnisse und Ergebnisse können bereits sehr früh in die Konzeption des Gesamtsystems mit einbezogen werden. Am Beispiel des Geotechnischen Informationssystems (GTIS) führte dies zu einer raum- und zeitabhängigen Verwaltung des Boden- und Konstruktionsmodells und zu einer Bauablaufsteuerung, innerhalb derer die einzelnen Bauzustände verwaltet und mit den entsprechenden Ausprägungen innerhalb des dreidimensionalen Boden- und Konstruktionsmodells verknüpft werden können

Reduction of the proton radius discrepancy by 3 sigma

We show that in previous analyses of electron-proton scattering, the uncertainties in the statistical procedure to extract the proton charge radius are underestimated. Using a fit function based on a conformal mapping, we can describe the scattering data with high precision and extract a radius value in agreement with the one obtained from muonic hydrogen.Comment: minor changes, matches the accepted versio

Electromagnetic corrections in hadronic processes

In quantum field theory, the splitting of the Hamiltonian into a strong and an electromagnetic part cannot be performed in a unique manner. We propose a convention for disentangling these two effects: one matches the parameters of two theories -- with and without electromagnetic interactions -- at a given scale mu_1, referred to as the matching scale. This procedure enables one to analyze the separation of strong and electromagnetic contributions in a transparent manner. We illustrate the method -- in the framework of the loop expansion -- in a Yukawa model, as well as in the linear sigma model, where we also investigate the corresponding low-energy effective theory.Comment: 19 pages (LaTex), 5 figures, published version. References in the introduction added, discussion shortened, 1 figure removed, conclusions unchange

Critical Analysis of Baryon Masses and Sigma-Terms in Heavy Baryon Chiral Perturbation Theory

We present an analysis of the octet baryon masses and the $\pi N$ and $KN$ $\sigma$--terms in the framework of heavy baryon chiral perturbation theory. At next-to-leading order, ${\cal O}(q^3)$, knowledge of the baryon masses and $\sigma_{\pi N}(0)$ allows to determine the three corresponding finite low--energy constants and to predict the the two $KN$ $\sigma$--terms $\sigma^{(1,2)}_{KN} (0)$. We also include the spin-3/2 decuplet in the effective theory. The presence of the non--vanishing energy scale due to the octet--decuplet splitting shifts the average octet baryon mass by an infinite amount and leads to infinite renormalizations of the low--energy constants. The first observable effect of the decuplet intermediate states to the baryon masses starts out at order $q^4$. We argue that it is not sufficient to retain only these but no other higher order terms to achieve a consistent description of the three--flavor scalar sector of baryon CHPT. In addition, we critically discuss an SU(2) result which allows to explain the large shift of $\sigma_{\pi N}(2M_\pi^2) - \sigma_{\pi N}(0)$ via intermediate $\Delta (1232)$ states.Comment: 18 pp, TeX, BUTP-93/05 and CRN-93-0

Ab initio calculation of the Hoyle state and a new look at clustering in nuclei

I present an ab initio calculation of the spectrum of carbon-12, including also the famous Hoyle state. Its structure is discussed and a new interpretation of clustering in nuclear physics is given.Comment: Plenary talk, The Rutherford Centennial Conference on Nuclear Physics, Manchester, August 8-12, 201