First measurement of proton-induced low-momentum dielectron radiation off cold nuclear matter
G. AgakishievJoint Institute of Nuclear Research, 141980 Dubna, RussiaA. BałandaSmoluchowski Institute of Physics, Jagiellonian University of Cracow, 30-059 Kraków, PolandD. BelverLabCAF, Dpto. Física de Partículas, Univ. de Santiago de Compostela, 15706 Santiago de Compostela, SpainA. BelyaevJoint Institute of Nuclear Research, 141980 Dubna, RussiaJ. C. Berger-ChenExcellence Cluster ‘Origin and Structure of the Universe’, 85748 Garching, GermanyA. BlancoLIP-Laboratório de Instrumentação e Física Experimental de Partículas, 3004-516 Coimbra, PortugalM. BöhmerPhysik Department E12, Technische Universität München, 85748 Garching, GermanyJ. L. BoyardInstitut de Physique Nucléaire (UMR 8608), CNRS/IN2P3, Université Paris Sud, F-91406 Orsay Cedex, FranceP. CabanelasLabCAF, Dpto. Física de Partículas, Univ. de Santiago de Compostela, 15706 Santiago de Compostela, SpainS. ChernenkoJoint Institute of Nuclear Research, 141980 Dubna, RussiaA. DybczakSmoluchowski Institute of Physics, Jagiellonian University of Cracow, 30-059 Kraków, PolandE. EppleExcellence Cluster ‘Origin and Structure of the Universe’, 85748 Garching, GermanyL. FabbiettiExcellence Cluster ‘Origin and Structure of the Universe’, 85748 Garching, GermanyO. FateevJoint Institute of Nuclear Research, 141980 Dubna, RussiaP. FinocchiaroIstituto Nazionale di Fisica Nucleare, Laboratori Nazionali del Sud, 95125 Catania, ItalyP. FonteLIP-Laboratório de Instrumentação e Física Experimental de Partículas, 3004-516 Coimbra, PortugalJ. FriesePhysik Department E12, Technische Universität München, 85748 Garching, GermanyI. FröhlichInstitut für Kernphysik, Goethe-Universität, 60438 Frankfurt, GermanyT. GalatyukInstitut für Kernphysik, Goethe-Universität, 60438 Frankfurt, GermanyJ. A. GarzónLabCAF, Dpto. Física de Partículas, Univ. de Santiago de Compostela, 15706 Santiago de Compostela, SpainR. GernhäuserTechnical University of Munich, Munich, GermanyK. GöbelGoethe University Frankfurt, Frankfurt am Main, GermanyM. GolubevaRussian Academy of Sciences, Moscow, RussiaD. González-DíazTechnical University of Darmstadt, Darmstadt, GermanyF. GuberRussian Academy of Sciences, Moscow, RussiaM. GumberidzeUniversité Paris-Sud, Orsay, FranceT. HeinzInstitut für Kernphysik, Goethe-Universität, 60438 Frankfurt, GermanyT. HenninoUniversité Paris-Sud, Orsay, FranceR. HolzmannLabCAF, Dpto. Física de Partículas, Univ. de Santiago de Compostela, 15706 Santiago de Compostela, SpainA. IerusalimovJoint Institute for Nuclear Research, Dubna, RussiaI. IoriIstituto Nazionale di Fisica Nucleare, Rome, ItalyA. IvashkinRussian Academy of Sciences, Moscow, RussiaM. JurkovicTechnical University of Munich, Munich, GermanyB. KämpferExcellence Cluster 'Origin and Structure of the Universe', 85748 Garching, GermanyT. KaravichevaRussian Academy of Sciences, Moscow, RussiaI. KöenigInstitut für Kernphysik, Goethe-Universität, 60438 Frankfurt, GermanyWolfgang KöenigGSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt, GermanyB. W. KolbGSI Helmholtzzentrum für Schwerionenforschung GmbH, 64291 Darmstadt, GermanyG. KornakovLabCAF, Dpto. Física de Partículas, Univ. de Santiago de Compostela, 15706 Santiago de Compostela, SpainR. KotteLabCAF, Dpto. Física de Partículas, Univ. de Santiago de Compostela, 15706 Santiago de Compostela, SpainA. KrásaCzech Academy of Sciences, Prague, CzechiaF. KrizekCzech Academy of Sciences, Prague, CzechiaR. KrückenTechnical University of Munich, Munich, GermanyH. KucJagiellonian University, Krakow, PolandW. KühnUniversity of Giessen, Giessen, GermanyA. KuglerCzech Academy of Sciences, Prague, CzechiaA. KurepinRussian Academy of Sciences, Moscow, RussiaV. P. LadyginJoint Institute for Nuclear Research, Dubna, RussiaR. LalikLabCAF, Dpto. Física de Partículas, Univ. de Santiago de Compostela, 15706 Santiago de Compostela, SpainStephan LangPhysik Department E12, Technische Universität München, 85748 Garching, GermanyK. LapidusInstitut für Kernphysik, Goethe-Universität, 60438 Frankfurt, GermanyA. LebedevInstitute of Theoretical and Experimental Physics, 117218 Moscow, RussiaT. LiuUniversité Paris-Sud, Orsay, FranceL. LopesInstitut für Kernphysik, Goethe-Universität, 60438 Frankfurt, GermanyM. LorenzGoethe University Frankfurt, Frankfurt am Main, GermanyL. MaierTechnical University of Munich, Munich, GermanyA. MangiarottiLIP-Laboratório de Instrumentação e Física Experimental de Partículas , 3004-516 Coimbra, PortugalJ. MarkertGoethe University Frankfurt, Frankfurt am Main, GermanyV. MetagUniversity of Giessen, Giessen, GermanyB. MichalskaJagiellonian University, Krakow, PolandJ. MichelGoethe University Frankfurt, Frankfurt am Main, GermanyD. MishraUniversity of Giessen, Giessen, GermanyC. MüntzGoethe University Frankfurt, Frankfurt am Main, GermanyL. NaumannInstitut für Kernphysik, Goethe-Universität, 60438 Frankfurt, GermanyY. PachmayerGoethe University Frankfurt, Frankfurt am Main, GermanyM. PałkaJagiellonian University, Krakow, PolandY. ParpottasFrederick University, Nicosia, CyprusV. PechenovJoint Institute of Nuclear Research, 141980 Dubna, RussiaO. PechenovaGoethe University Frankfurt, Frankfurt am Main, GermanyJ. PietraszkoGoethe University Frankfurt, Frankfurt am Main, GermanyWitold Wojciech PrzygodaJagiellonian University, Krakow, PolandB. RamsteinUniversité Paris-Sud, Orsay, FranceA. ReshetinRussian Academy of Sciences, Moscow, RussiaA. RustamovGoethe University Frankfurt, Frankfurt am Main, GermanyA. SadovskyRussian Academy of Sciences, Moscow, RussiaP. SalaburaJagiellonian University, Krakow, PolandA. SchmahLawrence Berkeley National Laboratory, Berkeley, United StatesE. SchwabPhysik Department E12, Technische Universität München, 85748 Garching, GermanyJ. SiebensonLabCAF, Dpto. Física de Partículas, Univ. de Santiago de Compostela, 15706 Santiago de Compostela, SpainYu. G. SobolevCzech Academy of Sciences, Prague, CzechiaS. SpataroUniversity of Turin, Turin, ItalyB. SpruckUniversity of Giessen, Giessen, GermanyH. StröbeleGoethe University Frankfurt, Frankfurt am Main, GermanyJ. StrothGoethe University Frankfurt, Frankfurt am Main, GermanyC. SturmInstitut für Kernphysik, Goethe-Universität, 60438 Frankfurt, GermanyA. TarantolaGoethe University Frankfurt, Frankfurt am Main, GermanyK. TeilabGoethe University Frankfurt, Frankfurt am Main, GermanyP. TlustýCzech Academy of Sciences, Prague, CzechiaM. TraxlerPhysik Department E12, Technische Universität München, 85748 Garching, GermanyR. TrȩbaczJagiellonian University, Krakow, PolandH. TsertosUniversity of Cyprus, Nicosia, CyprusT. VasilievJoint Institute for Nuclear Research, Dubna, RussiaV. WagnerCzech Academy of Sciences, Prague, CzechiaM. WeberTechnical University of Munich, Munich, GermanyC. WendischInstitut für Kernphysik, Goethe-Universität, 60438 Frankfurt, GermanyJ. WüstenfeldLabCAF, Dpto. Física de Partículas, Univ. de Santiago de Compostela, 15706 Santiago de Compostela, SpainS. YurevichPhysik Department E12, Technische Universität München, 85748 Garching, GermanyY. ZanevskyJoint Institute for Nuclear Research, Dubna, Russia
2012en
ABI
Аннотация
We present data on dielectron emission in proton induced reactions on a Nb target at 3.5 GeV kinetic beam energy measured with HADES installed at GSI. The data represent the first high statistics measurement of proton-induced dielectron radiation from cold nuclear matter in a kinematic regime, where strong medium effects are expected. Combined with the good mass resolution of 2%, it is the first measurement sensitive to changes of the spectral functions of vector mesons, as predicted by models for hadrons at rest or small relative momenta. Comparing the e+e− invariant mass spectra to elementary p + p data, we observe for e+e− momenta Pee<0.8 GeV/c a strong modification of the shape of the spectrum, which we attribute to an additional ρ-like contribution and a decrease of ω yield. These opposite trends are tentatively interpreted as a strong coupling of the ρ meson to baryonic resonances and an absorption of the ω meson, which are two aspects of in-medium modification of vector mesons.
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