Monday, March 11, 2002 - DPG-Tagungen

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Nuclear Physics Monday strange hadrons Λ, ¯ ΛandK 0 s are identified by reconstructing their decay topologies. The charged decay products as well as the charged Kaons were measured with 4 Time Projection Chambers (TPCs), two of them are located inside 2 large dipole magnets, the other two downstream of the magnets symmetrically to the beam line. Transverse mass spectra and rapidity distributions for Λ and charged Kaons will be shown for all three energies. The multiplicities at mid-rapidity and the total yields will be studied as a function of collision energy together with AGSand RHIC measurements and compared with model predictions. The ratio Λ/π as well as K + /π + shows a non-monotonic energy dependence and has a maximum between top AGSand 40 A·GeV. ∗ Supported by BMBF und GSI. Group Report HK 6.3 Mon 17:15 E Recent Results from the WA98-Experiment — •Henner Büsching for the WA98 collaboration — University of Münster, Münster, Germany Recent results from the WA98 experiment with p and Pb induced reactions at 158 AGeV are presented. The CERN-SPS experiment WA98 investigates the properties of hot, dense matter with the main focus on the measurement of photons and neutral mesons with the leadglass detector LEDA. Azimuthal γ-γ correlations at high pT which are influenced by jet-like structures and elliptic flow have been studied. An influence of energy loss effects (jet-quenching) should be evident in a characteristic modification of the correlation. A clear indication of back-to-back correlations can be seen with strong dependence on the pT of the photons and the size of the system. Results on transverse mass spectra of neutral pions measured at central rapidity are presented for impact parameter selected Pb+Pb collisions. In going from peripheral to medium central collisions there is a nuclear enhancement increasing with transverse mass similar to the Cronin effect, while for very central collisions this enhancement appears to be weaker than expected. Finally, results on event-by-event fluctuations of average transverse momentum of photons are presented. The magnitude of those fluctuations can indicate the equilibration level attained in the Pb+Pb collisions. HK 6.4 Mon 17:45 E Two particle correlations in STAR — •Dominik Flierl, Clemens Adler, Jens Berger, Thomas Dietel, Sören Lange, Reinhard Stock, andChristof Struck for the STAR collaboration — Universität Frankfurt The STAR detector system at RHIC is built to detect a large fraction of the hadrons produced in collisions of ultra relativistic heavy ions. The large TPC as the central detector of STAR identifies species and momentum of emitted particles. Most of the detected particles are pions, but a higher level trigger enables STAR also to search for rare particles. Those probes carry information about the early stages of the collision, but the expansion of highly compressed nuclear matter is best observed with the most abundant species : pions. Collective flow and spatial conditions at thermal freeze out when the pions leave the interaction volume are accessible by two pion correlations. We will present results from charged pion HBT studies at √ sNN = 130GeV. Supported by BMBF and GSI. HK 6.5 Mon 18:00 E Directed and Elliptical Flow Measured with the Forward-TPCs of the STAR Experiment — •Markus Oldenburg, Volker Eckardt, Andreas Gärtner, Patrizia Krok, Gaspare Lo Curto, Maria Mora, Jörn Putschke, Norbert Schmitz, Andreas Schüttauf, Frank Simon, Janet Seyboth, Peter Seyboth, and Michael Vidal — Max-Planck-Institut für Physik, Föhringer Ring 6, 80805 München, Germany The STAR detector at the Relativistic Heavy Ion Collider (RHIC) measures the hadronic observables of Au+Au collisions at √ sNN = 200 GeV per nucleon pair. The ’Max-Planck-Institut für Physik’ in Munich contributes two Forward-TPCs which expand the overall acceptance of STAR into the pseudorapidity region 2.5 < |η| < 4. Hydrodynamical models predict that in peripheral heavy-ion collisions the initial spatial anisotropy of the reaction zone is transformed into an anisotropy in the momentum distribution of the produced particles. This is caused by the pressure gradient generated at a very early stage of the collision. Anisotropic flow measures these azimuthal anisotropies by a Fourier expansion of the azimuthal angular distribution of the detected hadrons. Due to their acceptance coverage the FTPCs are suited to measure not only elliptical flow v2 (2 nd order Fourier coefficient) as the TPC already did in the region |η| < 1.5 but also directed flow v1 (1 st order Fourier coefficient). Therefore these detectors allow the determination of the (up to now) unknown sign of v2. In this talk a feasibility study and first results of the flow measurement with the FTPCs will be presented. HK 6.6 Mon 18:15 E Measurement of the Transverse Energy Distribution at Midrapidity in √ sNN = 130 GeV Au + Au Collisions by the PHENIX- Experiment at RHIC — •Christian Klein-Bösing —University of Münster, Germany The Relativistic Heavy Ion Collider (RHIC) in Brookhaven/USA started operation in the summer of 2000. During the first running period of RHIC gold-gold collisions with energies up to √ sNN = 130 GeV has been created. The PHENIX detector at RHIC is able to measure the properties of nuclear matter at the highest temperatures and energy densities produced in these collisions. To allow an estimation of the energy density the measurement of energy produced transverse to the beam direction provides valuable information, which can be compared to predictions of a phase transition at energy densities of about one GeV/fm 3 . The centrality dependence of the transverse energy is compared to results at lower energies from other experiments. HK 6.7 Mon 18:30 E Neutral Pion Spectra in Au+Au collisions at √ s NN = 130 GeV — •Stefan Bathe for the PHENIX collaboration — University of Münster, Germany Transverse momentum spectra for neutral pions in the range 1 GeV/c
Nuclear Physics Monday HK7 Instrumentation and Applications I Time: Monday 16:15–19:00 Room: F Group Report HK 7.1 Mon 16:15 F The source for ultra-cold neutrons at the research neutron facility FRM-II — •F. Joachim Hartmann, Igor Altarev, Andreas Frei, Stephan Gröger, Stephan Paul, Gerd Petzoldt, Wolfgang Schott, Uwe Trinks, andOliver Zimmer —Physik- Department, Technische Universität München A source for ultra-cold neutrons (UCN) with solid deuterium is planned for the new Munich high-flux neutron source FRM-II. Ultra-cold neutrons have energies below about 250 neV and may be stored in vessels, magnetic bottles and by gravity. The new source, Mini-D2, will be installed in beam tube SR-4 of FRM-II. It consists of a so-called converter, about 170 cm 3 of solid deuterium at a temperature of 5 K, and the storage volume, an evacuated tube of 6 cm diameter and about 8 m length. The walls of the storage tube will be coated with Be. The converter is located inside the storage volume very close to the Cold Source of FRM-II. From model calculations we may expect that in pulsed mode the source will produce UCN densities of about 10 4 cm −3 , by far more than the world’s best sources existing up to now. This enhancement in density will allow to measure important properties of the free neutron like the electric dipole moment or the lifetime with strongly improved precision. The layout of the source and the first experiment planned, the magnetic confinement of UCN, will be presented. Group Report HK 7.2 Mon 16:45 F The new, high-intensity ultracold neutron source at PSI — •Reinhold Henneck for the SUNS collaboration collaboration — Paul- Scherrer-Institut, CH-5232 Villigen, Schweiz The new PSI source for ultracold neutrons (UCN) is based on an intense, pulsed proton beam with a very low duty cycle, a spallation target of heavy material which is able to stand the high beam load of 2 mA for several seconds and a large moderator (30 l) of solid deuterium at about 6 K. Recent experimental studies have revealed a large gain factor for the production of UCN in solid deuterium from which one expects UCN densities in excess of 1000 UCN/cm 3 . This improvement of about 2 orders of magnitude over existing facilities will open new prospects for studies of fundamental properties of the neutron and its decay. As a first experiment we intend to improve the sensitivity in the measurement of the neutron electric dipole moment to about 5 · 10 −28 e·cm. We will discuss the general principle of this new type of source as well as details of the most important subsystems which are now being developed: (1) proton target, (2) heavy water moderator/ reflector, (3) solid deuterium moderator, (4) storage vessel and neutron guides. Group Report HK 7.3 Mon 17:15 F First Successful Stopping, Bunching and Trapping of Radioactive Ions at the Ion Trap Facility SHIPTRAP at GSI Darmstadt — •W. Quint 1,2,3,4 , D. Ackermann 1 , F. Attallah 1 , H. Backe 2 , D. Beck 1 , A. Dretzke 2 , O. Engels 3 , D. Habs 3 , F. Herfurth 4 , F. Hessberger 1 , S. Hofmann 1 , H.-J. Kluge 1 , W. Lauth 2 , B. Lommel 1 , G. Marx 1 , G. Münzenberg 1 , M. Mukherjee 1 , J. Neumayr 3 , S. Rahaman 1 , D. Rodriguez 1 , C. Scheidenberger 1 , M. Sewtz 2 , G. Sikler 1 , M. Tarisien 1 , P. Thirolf 3 , V. Varentsov 3 ,andC. Weber 1 — 1 GSI Darmstadt — 2 Universität Mainz — 3 Universität München — 4 CERN SHIPTRAP is an ion trap facility at the separator for heavy-ion reaction products (SHIP) at GSI. The scientific programme of the SHIP- TRAP facility comprises mass spectrometry, nuclear spectroscopy, laser spectroscopy and chemistry of transeinsteinium elements. The SHIP- TRAP facility consists of a gas cell for stopping and thermalizing highenergy recoil ions from SHIP, a rf ion guide for extraction of the ions from the gas cell, a linear rf trap for accumulation and bunching of the ions, and a Penning trap for isobaric purification. In first on-line tests we successfully stopped, accumulated and trapped radioactive nuclides which were produced in fusion reactions of a 40 Ca primary beam with a cerium target. The radioactive nuclides were extracted from the ion trap and identified by time-of-flight detection. The total efficiency for stopping, accumulating and trapping the ions was about 1 %. HK 7.4 Mon 17:45 F Ein Multilayer-Detektor zum Nachweis von ultrakalten Neutronen — •Gerd Petzoldt 1 , Igor Altarev 1 , Stephan Gröger 1 , Erwin Gutsmiedl 2 , F. Joachim Hartmann 1 , Peter Maier-Komor 1 , Stephan Paul 1 , Wolfgang Schott 1 , Uwe Trinks 1 und Oliver Zimmer 1 — 1 Physik-Department, Technische Universität München — 2 FRM II, Technische Universität München Es wurde ein Halbleiterdetektor für ultrakalte Neutronen (UCN) entwickelt, der auf einer Silizium PIN-Diode basiert. Zum Nachweis der Neutronen wird die Reaktion 6 Li(n,α) 3 H in einer auf den Detektor aufgebrachten Konverterschicht aus 6 LiF verwendet. Um das optische Potential der Oberfläche für Neutronen zu verringern, wird das 6 LiF mit einem Material negativer Streulänge in einer Multilayerstruktur kombiniert; die resultierende Reflektivität für Neutronen wurde für verschiedene Multilayerstrukturen mit einem Neutronenoptik-Programm berechnet. Der Energieverlust der Reaktionsprodukte in den verschiedenen Strukturen wurde mittels eines Monte-Carlo-Programmes simuliert. Drei Strukturen wurden hergestellt und in zwei verschiedenen Experimenten am Institut Laue-Langevin (ILL) in Grenoble, Frankreich, getestet. Die Ergebnisse werden vorgestellt. HK 7.5 Mon 18:00 F Measurements at the Jyväskylä RFQ-cooler— •A. Wilfart 1 , T. Sieber 1 , O. Kester 1 , D. Habs 1 , A. Nieminen 2 ,andJ. Szerypo 2 — 1 Sektion Physik, LMU München, Am Coulombwall 1, D-85748 Garching — 2 University of Jyväskylä, PB35 YFL, FIN-40351 JYV ÄSKYLÄ In order to measure the beam emittance of cooled low energetic ion beams (30 keV) from the Jyväskylä RFQ-ion-cooler, we designed an emittance meter for very low intensities and low beam energies by SIMION. We wanted to examine the dependence of the transmission and the emittance on the beam intensity (20pA-40nA) injected into the cooler device. In addition the improvement of the beam emittance due to the cooler has been studied. Finally the effect of different beam optic elements in the beam line, e. g. ”einzellenses”and skimmer electrodes on the beam could be easily measured with the emittance meter. The results of the measurements and the emittance meter lay-out in hard and software will be presented. HK 7.6 Mon 18:15 F Messung der Ortssensitivität eines 12-fach segmentierten, gekapselten HPGe-Detektors — •D. Weißhaar, J. Eberth, J. Jolie, H.G. Thomas, T. Waasem und N. Warr — Institut für Kernphysik, Universität zu Köln Segmentierte HPGe-Detektoren ermöglichen den Aufbau kompakter γ- Spektrometer mit hoher Granularität wie das MINIBALL- Spektrometer für Messungen am radioaktiven Strahl. Die Granularität ist notwendig um die Dopplerverbreiterung von γ-Linien bei Experimenten mit hohem v/c der γ-emittierenden Kerne zu minimieren. Der 12-fach segmentierte Detektor entspricht dem 6-fach segmentierten MINIBALL-Detektor mit einer zusätzlichen Quersegmentierung, die den vorderen Bereich vom hinteren abtrennt. Der Detektor wurde mit einer kollimierten Quelle abgetastet und die Verbesserung der Ortssensitivität aufgrund der zusätzlichen Tiefeninformation im Vergleich zum 6-fach segmentierten MINIBALL-Detektor untersucht. [1]J.Eberthet al., Prog. Part. Nucl. Phys. 46, 389 (2001). gefördert durch das BMBF (06OK958) HK 7.7 Mon 18:30 F Feasability study of spin correlations in 2 He ( 1 S0) — •J. Heyse 1 , C. Bäumer 2 , A.M. van den Berg 3 , E.L. Bolster 4 , J.A. Brooke 5 , P. Busch 4 , M. Hagemann 1 , M.N. Harakeh 3 , M.A. de Huu 3 , C. Polachic 5 , C. Rangacharyulu 5 , and H.J. Wörtche 3 for the EuroSuperNova collaboration — 1 Vakgroep Subatomaire en Stralingsfysica, Universiteit Gent, Belgium — 2 Westfälische Wilhems-Universität Münster — 3 Kernfysisch Versnellerinstituut, Rijksuniversiteit Groningen, The Netherlands — 4 University of Hull, United Kingdom — 5 Univeristy of Saskatchewan, Canada We present results of a feasability study for examining the Einstein- Podolsky-Rosen type spin correlations of protons in a 1 S0 intermediate state. A deuteron beam of 170 MeV was extracted from the AGORcyclotron at KVI, producing protons in a 12 C(d, 2 He) 12 B reaction popu-
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Nuclear Physics Friday HK49 Plenary
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Friese, J. . HK 14.1, HK 14.3, HK 4
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Rusev, G. ..................HK 10.1
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Monday, March 11, 2002 - DPG-Tagungen

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