Latest documents http://publikationen.ub.uni-frankfurt.de/index/index/ Thu, 13 Dec 2012 14:59:23 +0100 Thu, 13 Dec 2012 14:59:23 +0100 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/27309 We present measurements of exclusive ensuremathπ+,0 and η production in pp reactions at 1.25GeV and 2.2GeV beam kinetic energy in hadron and dielectron channels. In the case of π+ and π0 , high-statistics invariant-mass and angular distributions are obtained within the HADES acceptance as well as acceptance-corrected distributions, which are compared to a resonance model. The sensitivity of the data to the yield and production angular distribution of Δ (1232) and higher-lying baryon resonances is shown, and an improved parameterization is proposed. The extracted cross-sections are of special interest in the case of pp → pp η , since controversial data exist at 2.0GeV; we find \ensuremathσ=0.142±0.022 mb. Using the dielectron channels, the π0 and η Dalitz decay signals are reconstructed with yields fully consistent with the hadronic channels. The electron invariant masses and acceptance-corrected helicity angle distributions are found in good agreement with model predictions. Geydar Agakishiev; Alvarez-Pol; Balanda; Bassini; Michael Böhmer; Bokemeyer; Boyard; Cabanelas; Chernenko; Christ; Destefanis; Dohrmann; Dybczak; Eberl; Laura Fabbietti; Oleg Fateev; Finocchiaro; Jürgen Friese; Ingo Fröhlich; Tetyana Galatyuk; Juan A. Garzón; Roman Gernhäuser; Camilla Gilardi; Marina Golubeva; Diego González-Dıaz; Fedor Guber; Gumberidze; Hennino; Holzmann; Holzmann; Ierusalimov; Iori; Alexander Ivashkin; Martin Jurkovic; Kämpfer; Kanaki; Tatiana Karavicheva; Ilse Koenig; Wolfgang Koenig; Burkhard W. Kolb; Kotte; Kozuch; Krizek; Wolfgang Kühn; Andrej Kugler; Alexei Kurepin; S Lang; Kirill Lapidus; T. Liu; Ludwig Maier; Jochen Markert; Volker Metag; Beata Michalska; Emilie Morinière; Jehad Mousa; Mathias Münch; Christian Münch; Naumann; Jacek Tomasz Otwinowski; Yvonne C. Pachmayer; Vladimir Pechenov; Olga Pechenova; Tiago Pérez Cavalcanti; Jerzy Pietraszko; Vladimir Pospısil; Witold Przygoda; Béatrice Ramstein; Andrey Reshetin; M. Roy-Stephan; Anar Rustamov; Alexander Sadovsky; Benjamin Sailer; Piotr Salabura; M. Sánchez; Alexander Schmah; Erwin Schwab; Yuri Sobolev; Stefano Spataro; Björn Spruck; Herbert Ströbele; Joachim Stroth; Christian Sturm; Attilio Tarantola; Khaled Teilab; Pavel Tlusty; Alberica Toia; Michael Traxler; Radoslaw Trebacz; Haralabos Tsertos; Vladimir Wagner; Marcin Wisniowski; Tomasz Wojcik; Jörn Wüstenfeld; Sergey Yurevich; Yuri Zanevsky; Peter Zumbruch article http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/27309 Thu, 13 Dec 2012 14:59:23 +0100 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/26796 The CBM experiment will investigate heavy-ion collisions at beam energies from 8 to 45 AGeV at the future accelerator facility FAIR. The goal of the experiment is to study the QCD phase diagram in the vincinity of the QCD critical point. To do so, CBM aims at measuring rare probes among them open charm. In order to identify those rare and short lived particles despite the rich combinatorial background generated in heavy ion collisions, a micro vertex detector (MVD) providing an unprecedented combination of high rate capability and radiation hardness, very light material budget and excellent granularity is required. In this work, we will discuss the concept of this detector and summarize the status of the R&D. Michael Deveaux; Samir Amar-Youcef; Norbert Bialas; Dennis Doering; Melissa Domachowski; Horst Düring; Ingo Fröhlich; Tetyana Galatyuk; Jan Michael; Christian Müntz; Sarah Ottersbach; Paul Scharrer; Christoph Schrader; Joachim Stroth; Tobias Tischler; Christian Trageser; Bernhard Wiedemann; Jérome Baudot; Grégory Bertolone; Nathalie Chon-Sen; Claude Colledani; Rita De Masi; Andrei Dorokhov; Wojchiech Dulinski; Jean-Charles Fontaine; Mathieu Goffe; Abdelkader Himmi; Christine Hu; Kimmo Jaaskelainen; Michal Koziel; Frédéric Morel; Fouad Rami; Mathieu Specht; Isabelle Valin; Marc Winter; Christina Dritsa; Selim Seddiki; Franz M. Wagner conferenceobject http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/26796 Tue, 16 Oct 2012 16:20:55 +0200 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/26625 We have developed a versatile software package for the simulation of di-electron production in pp and dp collisions at moderate beam kinetic energies (1-2GeV). Particular attention has been paid to incorporate different descriptions of the Dalitz decay Δ rightarrow Ne + e - via a common interface. In addition, suitable parameterizations for the virtual bremsstrahlung process NN rightarrow NNe + e - based on one-boson exchange models have been implemented. Such simulation tools with high flexibility of the framework are important for the interpretation of the di-electron data taken with the HADES spectrometer and demonstrates the wide applicability within the field of nuclear and hadronic physics. Frank Dohrmann; Ingo Fröhlich; Tetyana Galatyuk; Romain Holzmann; Philipp K. Kählitz; Burkhard Kämpfer; Emilie Moriniere; Yvonne C. Pachmayer; Beatrice Ramstein; Piotr Salabura; Joachim Stroth; Radoslaw Trebacz; Jacques Van de Wiele article http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/26625 Tue, 16 Oct 2012 14:49:01 +0200 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/7201 The study of the electromagnetic structure of hadrons plays an important role in understanding the nature of matter. In particular the emission of lepton pairs out of the hot and dense collision zone in heavy-ion reactions is a promising probe to investigate in-medium properties of hadrons and in general the properties of matter under such extreme conditions. The first experimental observation of an enhanced di-electron yield in the invariant-mass region 0:3 - 0:7 GeV/c2 in p+Be collisions at 4:9 GeV/u beam energy [2] was announced by the DLS collaboration [1]. Recent results of the HADES collaboration show a moderate enhancement above n Dalitz decay contributions for 12C+12C at 1 and 2 GeV/u [3, 4] confirming the DLS results. There are several theoretical explanations of this observation, most of them focusing on possible in-medium modifications of the properties of vector mesons. At low beam energies the question whether the observed excess is related to any in-medium effects remains open because of uncertainties in the description of elementary di-electron sources. In this work the di-electron production in p+p and d+p reactions at a kinetic beam energy of 1:25 GeV/u measured by the HADES spectrometer is discussed. At Ekin = 1:25 GeV/u, i.e. below the n meson production threshold in proton-proton reactions, the delta Dalitz decay is expected to be the most abundant source above the pi 0 Dalitz decay region. The observed large difference in di-electron production in p+p and d+p collisions suggests that di-electron production in the d+p system is dominated by the n+p interaction. In order to separate delta Dalitz decays and np bremsstrahlung the di-electron yield observed in p+p and n+p reactions, both measured at the same beam energy, has been compared. The main interest here is the investigation of iso-spin effects in baryonic resonance excitations and the off-shell production of vector mesons [5]. We indeed observe a large difference in di-electron production in p+p and n+p reactions. Results of these studies will be compared to recent calculations. We will also present our experimentally defined cocktail for heavy-ion data. At much higher beam energies experimental results of the CERES [6] and NA60 [7] collaborations also show an enhancement in the invariant mass region 0:3 - 0:7 GeV/c2, in principle similar to the situation in DLS. A strong excess of lepton pairs observed by recent high energy heavy-ion dilepton experiments hint to a strong influence of baryons, however no data exist at highly compressed baryonic matter, achievable in heavy-ion collisions from 8 - 45 GeV/u beam energy. These conditions would allow to study the expected restoration of chiral symmetry by measuring in-medium modifications of hadronic properties, an experimental program which is foreseen by the future CBM experiment at FAIR. The experimental challenge is to suppress the large physical background on the one hand and to provide a clean identification of electrons on the other hand. In this work, strategies to reduce the combinatorial background in electron pair measurements with the CBM detector are discussed. The main goal is to study the feasibility of effectively reducing combinatorial background with the currently foreseen experimental setup, which does not provide electron identification in front of the magnetic field. Tetyana Galatyuk doctoralthesis http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/7201 Fri, 23 Oct 2009 10:35:15 +0200 http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/6019 Pluto is a Monte-Carlo event generator designed for hadronic interactions from Pion production threshold to intermediate energies of a few GeV per nucleon, as well as for studies of heavy ion reactions. The package is entirely based on ROOT, without the need of additional packages, and uses the embedded C++ interpreter of ROOT to control the event production. The generation of events based on a single reaction chain and the storage of the resulting particle objects can be done with a few lines of a ROOT-macro. However, the complete control of the package can be taken over by the steering macro and user-defined models may be added without a recompilation of the framework. Multi-reaction cocktails can be facilitated as well using either mass-dependent or user-defined static branching ratios. The included physics uses resonance production with mass-dependent Breit-Wigner sampling. The calculation of partial and total widths for resonances producing unstable particles is performed recursively in a coupled-channel approach. Here, particular attention is paid to the electromagnetic decays, motivated by the physics program of HADES. The thermal model supports 2-component thermal distributions, longitudinal broadening, radial blast, direct and elliptic flow, and impact-parameter sampled multiplicities. The interface allows angular distribution models (e.g. for the primary meson emission) to be attached by the user as well as descriptions of multi-particle correlations using decay chain templates. The exchange of mass sampling or momentum generation models is also possible. The first feature allows for consistent coupled-channel calculations, needed for a correct description of hadronic interactions. For elementary reactions, angular distribution models for selected channels are already part of the framework, based on parameterizations of existing data. This report gives an overview of the design of the package, the included models and the user interface. Ingo Fröhlich; Lorenzo Cazon Boado; Tetyana Galatyuk; Volker Hejny; Romain Holzmann; Marios Kagarlis; Wolfgang Kuehn; Johannes G. Messchendorp; Volker Metag; Marc-André Pleier; Witold Przygoda; Beatrice Ramstein; James Ritman; Piotr Salabura; Joachim Stroth; Malgorzata Sudol other http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/6019 Wed, 12 Nov 2008 15:17:56 +0100