27 research outputs found
Faessler, Joseph (Death, 1899-07-19)
No full textAddress: 449 Bank St.Age at death: 1 hr.Pg 80/1899/293/M W S/City/Dr. Geo. Eger/F. M. Westerman/St. Mary'sOriginal record filed in drawer labeled 'EWRY-FARRICK'
Faessler, George (Birth, 1893-02-19)
No full textAddress: Ninth St.1316/Pg. 32/1893/M. W./CincinnatiOriginal record filed in drawer labeled 'EWRY-FARRICK'
Messung der e⁺e⁻-Paarproduktion in 2AGeV-C-C-Kollisionen mit HADES
No full textThe search for a modification of hadron properties inside nuclear matter at normal and/or high temperature and density is one of the more interesting issues of modern nuclear physics. Dilepton experiments, by providing interesting results, give insight into the properties of strong interaction and the nature of hadron mass generation. One of these research tools is the HADES spectrometer. HADES is a high acceptance dilepton spectrometer installed at the heavy-ion synchrotron (SIS) at GSI, Darmstadt. The main physics motivation of HADES is the measurement of e+e- pairs in the invariant-mass range up to 1 GeV/c2 in pion- and proton-induced reactions, as well as in heavy-ion collisions. The goal is to investigate the properties of the vector mesons rho, omega and of other hadrons reconstructed from e+e- decay pairs. Dileptons are penetrating probes allowing to study the in-medium properties of hadrons. However, the measurement of such dilepton pairs is difficult because of a very large background from other processes in which leptons are created. This thesis presents the analysis of the data provided by the first physic run done with the HADES spectrometer. For the first time e+e- pairs produced in C+C collisions at an incident energy of 2 GeV per nucleon have been collected with sufficient statistics. This experiment is of particular importance since it allows to address the puzzling pair excess measured by the former DLS experiment at 1.04 AGeV. The thesis consists of five chapters. The first chapter presents the physics case which is addressed in the work. In the second chapter the HADES spectrometer is introduced with the characteristic of specific detectors which are part of the spectrometer. Chapter three focusses on the issue of charged-particle identification. The fourth chapter discusses the reconstruction of the di-electron spectra in C+C collisions. In this part of the thesis a comparison with theoretical models is included as well. The conclusion and final remarks are given in chapter five.Eines der Hauptziele der modernen Kernphysik ist die Untersuchung der Modifikation von Eigenschaften von Hadronen bei normaler und hoher Temperatur und Dichte. Dileptonen-Experimente liefern interessante Ergebnisse und geben einen Einblick in die Eigenschaften der starken Wechselwirkung und in die Natur der Massenerzeugung von Hadronen. Eines dieser Forschungswerkzeuge ist das HADES Spektrometer. HADES ist ein Dileptonen Spektrometer mit hoher Akzeptanz am Schwerionensynchroton der GSI in Darmstadt. Die wesentliche physikalische Motivation des Experiments ist, e+e- -Paare im invarianten Massenbereich bis GeV/c2, sowohl in pion- und protoninduzierten Reaktionen, als auch in Schwerionenkollisionen zu messen. Das Ziel ist die Untersuchung der Eigenschaften der Vektormesonen rho, omega und anderer Hadronen, welche aus e+e- -Paare rekonstruiert werden. Da Dileptonen nicht durch die starke Wechselwirkung beeinflusst werden, machen sie das Studium der Eigenschaften von Hadronen in Kernmaterie möglich. Allerdings ist die Messung dieser Dileptonenpaare schwierig, da Leptonen, die in anderen Prozessen erzeugt werden, einen grossen Untergrund erzeugen. In dieser Arbeit werden die Analyse von Daten, die mit dem HADES Spektrometer aufgenommen wurden, so wie Resultate derselben, diskutiert. Zum ersten Mal wurden mit ausreichender Statistik e+e- -Paare aufgezeichnet, die in der Kollision C+C bei einer Projektilenergie von 2 GeV per Nukleon erzeugt wurden. Dieses erste Experiment der HADES Kollaboration, da es ermöglicht, den von der DLS Kollaboration bei 1.04 AGeV gemessenen Paar-Überschuss zu verifizieren. Diese Arbeit besteht aus fünf Kapiteln. Das erste Kapitel beschreibt die dieser Arbeit zugrunde liegende Physik. Im zweiten Kapitel wird das HADES Spektrometer mit den typischen Eigenschaften der einzelnen Komponenten vorgestellt. Kapitel 3 fokussiert das Thema der Identifikation von geladenen Teilchen. Das 4. Kapitel präsentiert die Rekonstruktion von Dielektronen-Spektren in C+C Kollisionen. In diesem Teil der Arbeit wird auch der Vergleich mit theoretischen Modellen berücksichtigt. Die Schlussfolgerungen befinden sich im Kapitel 5
Physics of high-energy heavy-ion collisions
No full textThis a review of the present status of heavy-ion collisions at intermediate energies. The main goal of heavy-ion physics in this energy regime is to shed some light on the nuclear equation of state (EOS), hence we present the basic concept of the EOS in nuclear matter as well as of nuclear shock waves which provide the key mechanism for the compression of nuclear matter. The main part of this article is devoted to the models currently used for describing heavy-ion reactions theoretically and to the observables useful for extracting information about the EOS from experiments. A detailed discussion of the flow effects with a broad comparison with the avaible data is presented. The many-body aspects of such reactions are investigated via the multifragmentation break up of excited nuclear systems and a comparison of model calculations with the most recent multifragmentation experiments is presented
Neutron- and neutrino-induced reactions : their physical description and influence on r-process calculations
No full textWhen I started this thesis my supervisors F. K. Thielemann and T. Rauscher
spoke to me enthusiastically about the exciting and interesting field of nuclear astrophysics
at our very first meeting. A field actually consisting of several branches
of physics: thermodynamics, quantum mechanics, hydrodynamics, astrophysics,
nuclear physics and numerics, just to mention some. During my thesis I had
the opportunity to get deeper insights in nuclear physics, and astrophysics. Nuclear
astrophysics and nuclear physics are inseparably connected. Astrophysical
simulations, such as the modelling of supernova explosions or nucleosynthesis calculations,
depend directly on nuclear physics information, like nuclear masses,
half-lives, or nuclear reaction rates which can impose some constraints on the
astrophysical parameter space. On the other side astrophysical simulations can
provide constraints on nuclear models, such as the prediction of nuclear masses.
Current accelerator facilities are able to provide this information for stable nuclei
and for a broad range of neutron-rich nuclei. However, extremely neutron-rich
nuclei still cannot be investigated due to their extremely small half-lives. Experimental
information for these nuclei will be available at the earliest from the
next generation of accelerators, which are currently under construction and will
provide experimental information for such neutron-rich nuclei starting in a couple
of years.
The first part of this thesis is dedicated to nuclear physics. The calculation
of reaction rates which enter nucleosynthesis calculations in astrophysical simulations
is an important ingredient. The way these rates are calculated depends,
among other things, on the projectile energy and the mass region where the reaction
takes place. For intermediate and heavy masses the reaction rate can
be described by the so-called compound nucleus picture. In this model the the
projectile and target nucleus form a compound state which de-excites by various
particle evaporation modes. The compound nucleus picture describes the
reaction mechanisms well if there are enough levels at the energy at which the
compound nucleus is formed so that an average over individual resonances can
be performed. This model is called the Hauser Feshbach or statistical model. In
the case of absence of the described levels at the formation energy, other reaction
mechanisms have to be utilized to calculate the reaction rates, like direct reactions
for example. The nuclear level density (NLD) is an important ingredient
in the calculation of nuclear cross sections. In Chapter 2 the derivation of the
NLD is reviewed. It will be shown that the NLD can be decomposed into three
parts: a spin-, an excitation-energy-, and a parity dependent part. It will be
assumed that the odd and even parity states are equally distributed. Chapter 3
is devoted to the calculation of the NLD - but this time without the assumption
of equally distributed parities. An energy dependent parity-distribution function
will be derived.
Nuclei heavier than iron are predominantly made by neutron-capture processes.
The solar system abundance pattern of heavy nuclei indicates that two
distinct neutron-capture processes occur in nature - one at low neutron density,
called s-process, and one at high neutron density, called r-process. The r-process,
or rapid neutron-capture process will be discussed in detail in the second part
of my thesis. General aspects of nucleosynthesis calculations are reviewed in
Chapter 4 including a discussion of the mathematical framework. A discussion of
possible r-process sites, observational informations and astrophysical parameters
are presented in Chapter 5. In Chapter 6 the focus will be set on the neutrino
driven wind as a possible site for the production of elements heavier than iron. For
the first time, neutrino-induced, neutron-induced, and beta-delayed fission are included
simultaneously in a r-process nucleosynthesis calculation. Possible effects
of all fission channels on the final abundance distribution and the discussion of
the relevant nuclear physics are presented in Chapter 6, too. The thesis concludes
with a short discussion of the results and an outlook on future improvements and
investigations
Single- and low-lying-states dominance in two-neutrino double-beta decay
No full text19 pages, 5 tables, 6 figures.--Available on line on Oct 30, 2008.--ArXiv pre-print available at: http://arxiv.org/abs/0811.0319A theoretical analysis of the single-state dominance hypothesis for the two-neutrino double-beta decay rates is performed on the examples of the double-beta decays of 100Mo, 116Cd and 128Te. We also test the validity of an extended low-lying-state dominance that takes into account the contributions of the low-lying excited states in the intermediate nucleus to the double-beta decay rates. This study has been accomplished for all the double-beta emitters for which we have experimental information on their half-lives. The theoretical framework is a proton–neutron quasiparticle random-phase approximation based on a deformed Skyrme Hartree–Fock mean field with pairing correlations. Our calculations indicate that there are no clear evidences for single- or low-lying-state dominance in the two-neutrino double-beta decay. Finally, we investigate the single-electron energy distributions of the outgoing electrons in the double-beta decay processes with an exact treatment of the energy denominators, which could help for a more comprehensive analysis of NEMO-3 data.This work was supported by Ministerio de Ciencia e Innovaci´on (Spain) under contract no. FIS2005-00640. It was also supported in part by the EU ILIAS project under contract RII3-CT-2004-506222. O M and R A R thank Ministerio de Ciencia e Innovaci´on (Spain) for financial support.Peer reviewe
First Measurement of Chiral Dynamics in pi(-)gamma -> pi(-)pi(-)pi(+)
No full textAdolph C, Alekseev MG, Alexakhin VY, et al. First Measurement of Chiral Dynamics in pi(-)gamma -> pi(-)pi(-)pi(+). Physical Review Letters. 2012;108(19): 192001.The COMPASS Collaboration at CERN has investigated the pi(-)gamma -> pi(-)pi(-)pi(+) reaction at center-of-momentum energy below five pion masses, root s < 5m(pi), embedded in the Primakoff reaction of 190 GeV pions impinging on a lead target. Exchange of quasireal photons is selected by isolating the sharp Coulomb peak observed at smallest momentum transfers, t' < 0.001 GeV2/c(2). Using partial-wave analysis techniques, the scattering intensity of Coulomb production described in terms of chiral dynamics and its dependence on the 3 pi-invariant mass m(3 pi) = root s were extracted. The absolute cross section was determined in seven bins of root s with an overall precision of 20%. At leading order, the result is found to be in good agreement with the prediction of chiral perturbation theory over the whole energy range investigated
Evidence for the decay X(3872)→ψ(2S)γ
No full textEvidence for the decay mode X(3872)→ψ(2S)γ in B+→X(3872)K+ decays is found with a significance of 4.4 standard deviations. The analysis is based on a data sample of proton–proton collisions, corresponding to an integrated luminosity of 3 fb−1, collected with the LHCb detector, at centre-of-mass energies of 7 and 8 TeV. The ratio of the branching fraction of the X(3872)→ψ(2S)γ decay to that of the X(3872)→J/ψγ decay is measured to be
where the first uncertainty is statistical and the second is systematic. The measured value does not support a pure molecular interpretation of the X(3872) state
Search for the double beta decay of Zr-96 with NEMO-3 and calorimeter development for the SuperNEMO experiment
No full textUsing 9.4 g of Zr-96 and 1221 days of data from the NEMO-3 detector corresponding to 0.031 kgy, the obtained 2vbb decay half-life measurement is [2.35 \pm 0.14(stat) \pm 0.16(syst)] \times 10_{19}yr. Different characteristics of the final state electrons have been studied, such as the energy sum, individual electron energy, and angular distribution. The 2v nuclear matrix element is extracted using the measured 2vbb half-life and is 0.049 \pm 0.002. The 0vbb decay half-life is excluded at the 90% CL to > 9.2 \times 10_^{21}yr corresponding to a limit on the effective Majorana neutrino mass of < 7.2 – 19.4 eV. Limits on other mechanisms of 0vbb have also been set.
Due for commissioning in 2012, SuperNEMO is the next generation detector which improves upon the proven technology and success of NEMO-3 to achieve a half-life sensitivity of ~10_{26} yr (90% CL) for Se-82 which corresponds to a neutrino mass of 50-100 meV. An energy resolution of 7% FWHM at 1 MeV has been obtained for the calorimeter baseline design of SuperNEMO which is currently in the R&D phase. This result not only meets the requirement stipulated by the R&D proposal, but is unprecedented for this type of calorimeter design
