Monday, March 11, 2002 - DPG-Tagungen

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Nuclear Physics Thursday HK48 Instrumentation and Applications VI Time: Thursday 16:00–18:00 Room: F Group Report HK 48.1 Thu 16:00 F Investigaions of scintillation detectors for relativistic heavy ion calorimetry — •Radomira Lozeva 1,2 , Jürgen Gerl 1 , Ivan Kojouharov 1 , Samit Mandal 1 ,andJuri Kopatch 1 — 1 GSI, Darmstadt, Germany — 2 Faculty of Physics, University of Sofia, Sofia, Bulgaria To gain information on the energy resolution of scintillators for heavy ion detection at high particle energy an in-beam test was performed at the Fragment Separator, FRS at GSI. Primary 197 Au beam was transported through FRSand particle identification detectors to the scintillator set-up. CsI(Tl)+PMT, CsI(Tl)+PIN diode, NaI(Tl), BGO and Plastic scintillation detectors were selected for investigation. The results of the in-beam test analysis showed satisfactory results for the CsI(Tl)+PMT scintillator. An energy resolution of 0.46% FWHM for 197 Au ions of 306 MeV/n ion energy was achieved with appropriate analysis conditions. The obtainable resolution is sufficient for further mass determination of heavy ions by calorimetry and will therefore be chosen for the fast beam RISING [1] campaign at GSI. [1] http://www-aix.gsi.de/ ∼ wolle/EB at GSI/rising.html HK 48.2 Thu 16:30 F Performance of the Pre-Shower System in the HADES Spectrometer — •Jerzy Pietraszko for the HADEScollaboration — GSI, Darmstadt The Pre–Shower detector system of the HADES spectrometer is applied to electron identification with emphasis on fast pion rejection at forward angles. The detector is operated in the self–quenching streamer mode (SQS) to simplify on-line recognition of electromagnetic showers. Stable electronics at low noise guarantee robust pattern recognition through the experimental runs. On-line analysis results delivered by dedicated pattern recognition units show perfect agreement with results derived in the off-line analysis. The performance of the detector and readout system will be presented. HK 48.3 Thu 16:45 F HADES Drift Chambers (MDC III) — •Kalliopi Kanaki, Frank Dohrmann, Rugard Dressler, Wolfgang Enghardt, Eckart Grosse, Klaus Heidel, Jochen Hutsch, Burkhard Kämpfer, Roland Kotte, Lothar Naumann, Alexandre Sadovski, Joachim Seibert, and Manfred Sobiella for the HADEScollaboration — Forschungszentrum Rossendorf, Institut für Kern- und Hadronenphysik, Dresden, Germany The starting experiments with the High Acceptance Di-Electron Spectrometer (HADES) at GSI/Darmstadt require a momentum resolution of about 1%, i.e. the determination of particle tracks with a precision better than 100 µm. The tracking is accomplished mainly by largearea Multiwire Drift Chambers. Four of the MDC’s of the third plane (MDC III), produced in the Research Centre Rossendorf, have been already installed in the HADESspectrometer. In this talk, the technical aspects of the MDC III construction, the operational characteristics, and several tests performed are discussed. We also presented simulations of the electrical field configurations and resulting drift velocity patterns which are aimed at an optimision of the chamber performance. HK 48.4 Thu 17:00 F Measurement of π 0 -induced leptons in the HADES RICH ∗ — •T. Eberl, L. Fabbietti, J. Friese, R. Gernhäuser, J. Homolka, H.-J. Körner, M. Münch, B. Sailer, andS. Winkler — Technische Universität München, James-Franck-Strasse 1,D-85748 Garching A fast Ring Imaging Cherenkov detector (RICH) is the central device of the new dilepton spectrometer HADESat GSI, Darmstadt. It serves as a hadron blind trigger device for e + e − pairs in hadron and heavy ion induced collisions at 1-2 AGeV incident energy, in which π 0 are produced abundantly. The main sources of lepton pairs with small opening angles (1-15 degrees) are π 0 -Dalitz decays (π 0 → e ± γ) and photo conversion pairs (π 0 → 2γ; γ → e ± ) from the target, the C4F10 gas radiator and the VUV transparent CaF2 window. These lepton signals contribute significantly to the combinatorial background, if they are not identified properly. We report on the analysis and classification of measured lepton-induced ring patterns on the RICH photocathode from a dedicated low magnetic field measurement in correlation with data from the HADEStracking (MDC) and time-of-flight (TOF wall) subdetectors. ∗ supported by BMBF (6TM970I) and GSI (TM-FR1). HK 48.5 Thu 17:15 F Charged Particle Detection with PbWO4 — •Matthias Hoek 1 , Werner Döring 1 , Volker Hejny 2 , Herbert Löhner 3 , Volker Metag 1 , Rainer Novotny 1 , and Heinrich Wörtche 3 — 1 II. Physikalisches Institut, Universität Giessen, Germany — 2 Institut für Kernphysik, FZ-Jülich, Germany — 3 Kernfysich Versneller Instituut, Groningen, The Netherlands TheresponseofPbWO4 to high energy charged hadrons has been investigated in two test experiments at the proton beam facilities COSY, FZ-Jülich (E=1.2 GeV) and AGOR, KVI, Groningen (E=85MeV). For the first time, the energy resolution for protons and deuterons below 360 MeV energy, which were stopped within 150 mm of PbWO4, has been determined to σ/E=0.97%/ √ E + 3.33%. The result is comparable to the previously deduced photon response. Energy spectra of inelastically scattered protons below 85MeV measured with pure and doped PbWO4crystals are compared to similar distributions obtained for BaF2- and CeF3-detectors. The comparison to the response of charged pions indicates a strong quenching factor (¿3) of the scintillation light for hydrogen isotopes. The obtained results document the applicability of PbWO4 in photon and particle detection at medium energies. HK 48.6 Thu 17:30 F Large-Area Glass Resistive Plate Chambers (GRPC) as Fast Timing Detector — •Zbigniew Tyminski — Gesellschaft für Schwerionenforschung, Darmstadt, Germany In the framework of the FOPI upgrade project our collaboration is planning to build another time-of-flight detector shell capable of coping with the expected multiplicity of 80-100 charged particles (central Au+Au collisions at 1.5A GeV) at time resolutions below 100 ps. A possible solution are Glass Resistive Plate Chambers [1]. We have studied several prototypes of such detectors (400 cm 2 big) with 4 gaps of 300µm between glass plates of 0.5-2 mm thickness and intermediate strip electrodes formed of 12 or 16 parallel strips (pitch ≈ 3mm) which are read out on each side. The time is obtained by mean timing of the 2 signals, their difference delivers the position along the strip; charge averaging over neighbouring strips yields the perpendicular position. We describe details of the prototypes as well as tests in which we have obtained σ ≈ 70 ps at efficiencies above 95%. [1] P.Fonte et al., NIM A449(2000)295 HK 48.7 Thu 17:45 F The potential of in-beam PET for proton therapy monitoring: first experimental investigation — •Katia Parodi 1 , Wolfgang Enghardt 1 ,andThomas Haberer 2 — 1 Forschungszentrum Rossendorf e.V., Postfach 510119, 01314 Dresden — 2 Gesellschaft für Schwerionenforschung, Planckstr. 1, 64291 Darmstadt On the basis of the positive clinical impact of in-beam PET on the quality assurance of carbon ion therapy at GSI Darmstadt [1] we started to investigate the potential extension of the technique to proton therapy. This is non-trivial, since protons cannot suffer the projectile fragmentation process which leads to a pronounced maximum of the β + activity in close vicinity to the dose maximum in the carbon ion case. In our experiment three monoenergetic proton beams in the energy and intensity range of therapeutic interest were stopped in targets of PMMA (C5H8O2) placed in the centre of the field of view of the in-beam positron camera installed at the GSI heavy ion therapy facility. The β + activity signal was found to be three times larger than that induced by carbon ions at the same range and applied physical dose. The reconstructed spatial β + activity distributions were well reproduced in shape by a calculation based on experimental cross-sections and on the proton flux given by the FLUKA Monte Carlo code. Despite the weaker spatial correlation between activity and dose depth-distributions in the proton case, our experiment supports the feasibility of in-beam PET for the monitoring of proton therapy based on a comparison between measured and calculated β + activity distributions, as already implemented for carbon ion therapy. [1] W. Enghardt et al, Nucl. Phys. A 654 1047c (1999)
Nuclear Physics Friday HK49 Plenary Session Time: Friday 08:30–10:30 Room: Plenarsaal Plenary Talk HK 49.1 Fri 08:30 Plenarsaal New Results from HERMES — •Michael Düren for the HERMES Kollaboration collaboration — II. Phys. Inst. Univ. Giessen The HERMESexperiment at DESY studies the spin and flavor structure of nucleons using the 27 GeV polarized electron beam at HERA scattered off longitudinally polarized gas targets. After 6 years of data taking HERMEShas produced a large variety of physics results. An overview of the recent results is given. This year HERMESstarts to take data on transversely polarized targets to study the transversity distributions of quarks in nucleons. In a new proposal HERMESplans to complete the spectrometer by a large angle recoil detector to allow for a precision measurment of hard exclusive processes. Plenary Talk HK 49.2 Fri 09:00 Plenarsaal New Results from the BaBar Experiment — •Stefan Spanier for the BABAR collaboration — SLAC The BaBar collaboration has observed a significant CP violation in the neutral B-meson system and is able to search for physics beyond the Standard Model. The experiment is situated at the asymmetric e + e − collider, PEP II of the Stanford Linear Accelerator Center (SLAC). More than 120 million B mesons have been collected at the Υ(4S) resonance. This allows for precision studies of lifetime-time dependent properties and for the observation of many rare decays. A review of the rich physics program of BaBar, which also includes the study of D-mesons, charmed baryons, τ-leptons, and radiative processes will be presented. Emphasis will be placed on measurements of CP violation in the B system. Plenary Talk HK 49.3 Fri 09:30 Plenarsaal Nuclear quests in astrophysics — •Karlheinz Langanke —University of Aarhus (DEnmark) Willy Fowler once jokingly refered to astrophysics as applied nuclear physics. Indeed nuclear physics plays a keyrole in many astrophysical models and observations ranging from big bang to supernovae and the astrophysical simulations cannot be better than their nuclear inputs. Very HK50 Plenary Session often this involves radioactive short-lived nuclei matching optimally recent experimental and theoretical developments in nuclear physics. The nuclear input required to model astrophysical processes should ultimatively come from experiment. In reality, however, data have to be supplemented by theoretical models which in turn must be constrained and guided by experiment. There has been significant progress in modelling nuclei, as they, for example, are important in supernovae. Much of this is due to recent advances in modern shell model techniques. The talk will highlight some of this progress, but also future needs in selected important astrophysical processes. These include core-collapse supernovae, r-process nucleosynthesis and neutron stars in binary systems. Plenary Talk HK 49.4 Fri 10:00 Plenarsaal Acceleration of radioactive ion beams at REX-ISOLDE — •O. Kester for the REX-ISOLDE collaboration — Sektion Physik der LMU München, Am Coulombwall 1, D-85748 Garching In 2001 the linear accelerator of the Radioactive beam Experiment (REX-ISOLDE) delivered for the first time accelerated radioactive ion beams with a beam energy of 2 MeV/u. REX-ISOLDE uses the method of charge state breeding, in order to enhance the charge state of the ions before injection into the LINAC. Radioactive singly charged ions delivered by the on-line mass separator ISOLDE are first accumulated in a Penning trap, then charge bred to an A/q = 4.5 in an electron beam ion source (EBIS) and finally accelerated in a LINAC from 5 keV/u to the final energy between 0.8 and 2.2 MeV/u. Measurements of the interplay between the REXTRAP, the transfer line and the EBIShave been done as well as the first commissioning of the accelerator. Therewith the properties of the different elements could be determined and a first optimization of the system could be carried out. In two test beam times in 2001 stable and radioactive Na isotopes ( 23 Na- 26 Na) have been accelerated and transmitted to a preliminary target station. There 58 Ni and Be targets have been used to populate exited states via Coulomb excitation and nuclear transfer reactions. First results of the commissioning and of the beam times will be presented. supported by the BMBF under 06LM974 and 06HD802I Time: Friday 11:00–12:30 Room: Plenarsaal Plenary Talk HK 50.1 Fri 11:00 Plenarsaal The Advantage of Exclusiveness — •Rainer Jakob —BUGH Wuppertal, Theoretische Physik, Gauss-Str.20, 42097 Wuppertal Exclusive hard processes provide a distinguished view on the quark and gluon substructure of hadrons. The additional constraint on the final state in exclusicve processes enforces strict requirements on possible reaction mechanisms operative at non-asymptotic momentum transfers. The event of generalized parton distribution not only has emphasized the close relationship between perturbative QCD descriptions of inclusive and exclusive processes, but has greatly contributed in putting the formalism of exclusive reactions on a sound basis in the context of Quantum Field Theory. In generalizing the well-known and well-trusted concepts of forward parton distribution to the non-forward cases it became evident that only exclusive measurements can shed light on the question about the spatial location of partons inside hadrons, and related items like the orbital angular momentum of partons. On overview about the present status in the description of hard exclusive reactions will be attempted. Where are we now, and where are we heading for ? Plenary Talk HK 50.2 Fri 11:30 Plenarsaal Neutron beta decay and the CKM matrix — •Oliver Zimmer —TUMünchen, Physik Department E18, 85748 Garching In the standard model of electroweak interactions, the quark mass eigenstates are linked to the weak eigenstates via the Cabibbo-Kobayashi- Maskawa (CKM) quark-mixing matrix. Traditionally, the first element of this matrix, Vud, is determined from well-selected, pure Fermi nuclear beta decays. An alternative derivation, which is free from corrections due to nuclear structure, employs neutron beta decay data. Thereby comparable accuracy has recently been attained, combining the values of the neutron lifetime and of the neutron beta-asymmetry. Results of most accurate determinations of Vud from both methods, including values of Vus and Vub from high-energy physics, are in contradiction to the unitarity of the CKM matrix. The origin of the discrepancy is still unresolved. A survey of the field is given, emphasizing recent and ongoing developments in neutron decay experimentation. Plenary Talk HK 50.3 Fri 12:00 Plenarsaal QUADRUPOLE AND MAGNETIC MOMENTS OF NEUTRON-RICH NUCLEI FROM PROJECTILE FRAG- MENTATION. — •Gerda Neyens for the University of Leuven, GANIL, University of Sofia, FLNR-JINR Dubna, University of Gottingen. collaboration — University of Leuven, Instituut voor Kernen Stralingsfysica, Celestijnenlaan 200 D, B-3001 Leuven, Belgium Recent advances in measuring the static moments of beams of radioactive nuclei will be presented. In particular the study of nuclei produced and spin-oriented in fragmentation reactions will be addressed [1-4]. By combining different types of spin-orientation (alignment, polarization) with different experimental techniques it is possible to measure the magnetic dipole moments, electric quadrupole moments as well as the spin of exotic nuclei. Some examples of recent results obtained at the GANIL facility, such as moments and spins of nuclei near 32Mg [5,6] will be discussed. [1] G. Neyens et al., Nuclear Instrum. and Methods, Sect. A 340, 555 (1994). [2] G. Neyens et al., Phys. Lett. B 393, 1-2, 36 (1997). [3] N. Coulier et al., Phys. Rev. C 59, 1935 (1999). [4] G. Neyens et al., Phys. Rev. Lett. 82, 497 (1999). [5] S. Teughels et al., Ph.D. thesis K.U. Leuven, 2001 [6] D. Borremans et al., submitted Phys. Lett. B.
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Monday, March 11, 2002 - DPG-Tagungen

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