Collective modes excited in inelastic scattering of fast protons studied at Cyclotron Centre Bronowice - (CCB) Maria Kmiecik IFJ PAN Krakow Shapes and Symmetries in Nuclei: from Experiment to Theory (SSNET'17)

Collaboration M. Kmiecik, B. Wasilewska, A. Maj, M. Ziębliński, M. Ciemała, J. Grębosz, J. Łukasik, P. Pawłowski, P. Lasko, P. Bednarczyk, B. Fornal, M. Krzysiek, Ł. Iskra, B. Sowicki, A. Szperłak, K. Mazurek, W. Parol, I. Ciepał, N. Cieplicka-Oryńczak, M. Jastrząb, K. Guguła – IFJ PAN Kraków F.C.L. Crespi, A. Bracco, S. Brambilla, S. Bottoni, F. Camera, S. Leoni, A. Giaz - Università degli Studi di Milano and INFN, Milano M. Matejska-Minda, P. Napiorkowski, M. Saxena – SLCJ Warszawa Tamii, J. Isaak - RCNP, Osaka M. Harakeh - KVI Groningen Krasznahorkay - ATOMKI, Debrecen M. Lewitowicz – GANIL, Caen V. Guadilla – IFIC Valencia Ch. Schmitt, S. Kihel – IPHC Strasbourg LiQuiang Qi – IPN Orsay M. Stanoiu – NIPNE Bucharest Maria Kmiecik SSNET17

Collective excitations gamma decay E* IVGDR (Giant Dipole Resonance) proton and nutron oscillations - almost all nuclei take part in excitation ISGQR ( Giant Quadrupole Resonance) Bn „pygmy” states - PDR (Pygmy Dipole Resonance) few percent nucleons take part in excitation g.s. Maria Kmiecik SSNET17

Motivation GQR not well known, studied mainly using (p,p’) and (e,e’) reactions small yield (~10-4) of GQR gamma decay – studied so far only in 208Pb J.Beene et al PRC39(1989)1307 Shevchenko PRL93(2004)122501-1 decay to g.s. 381 MeV 17O on 208Pb target g-ray gated E* spectra GDR rather well known – information on nuclear shape „pygmy” states (PDR) – still under investigations (p,p’) Tamii PRL107(2011)062502 γ – decay from excited states and giant resonances, excited by different probes, can deliver information on decay mechanism, nuclear properties and provide data for verification of theoretical models Maria Kmiecik SSNET17

Idea of the experiment proton beam from the CCB Krakow cyclotron used for medical treatment p @ 85 MeV on 208Pb target 48 mm (54.5 mg/cm2) thick p beam target HECTOR gamma rays KRATTA protons p’ coincidence measurement of gamma rays and scattered protons Maria Kmiecik SSNET17

Experimental setup HECTOR (8 BaF2) LaBr3 (large volume 8”x3.5”) PARIS (cluster of 9 „phoswiches” LaBr3/CeBr3 + NaI) KRATTA (16 CsI telescopes) Maria Kmiecik SSNET17

Experimental setup HECTOR (8 BaF2) LaBr3 (large volume 3.5”x8”) PARIS (cluster of 9 „phoswiches” LaBr3/CeBr3 + NaI) KRATTA (16 CsI telescopes, at 8-15.3°) fast plastic scintillators in the front of KRATTA beam target Maria Kmiecik SSNET17

Preliminary results gamma decay for different excitation energy ranges Eg [MeV] E* [MeV] HECTOR gamma energy vs. excitation energy background subtracted gated by: proton proton and gamma times Maria Kmiecik SSNET17

Preliminary results gamma decay to different final states HECTOR Eg [MeV] E* [MeV] HECTOR 208Pb 2+ 4.085 MeV 3- 2.614 MeV g.s. 0 MeV selection of GDR decaying to different states (g.s.,3-,2+) consistent with D. Brink hypothesis: „GDR can be built on any state” „pygmy” PDR GQR GDR 3- 2+ analysis: Basia Wasilewska Maria Kmiecik SSNET17

Preliminary results - decay to different final states Spectra show gamma decay of giant resonances (GDR and GQR) and „pygmy” states But still more quantitative analysis has to be done. Especially extracting the GQR/GDR yield by taking into account: branchings cross sections detection efficiency angular distributions 3- 2+ „pygmy” PDR GQR GDR preliminary analysis: Basia Wasilewska Maria Kmiecik SSNET17

Decay to ground state as a function of proton scattering angle increase of „pygmy” strength at forward angles – consistent with other experiments 8° - 9.8° 9.8° - 11.6° 11.6° - 13.5° 13.5° - 15.3° preliminary Maria Kmiecik SSNET17

Decay to different final states - PARIS discrete transitions in „pygmy” region Eγ [MeV] PARIS spectra decay to g.s. decay to 3- decay to 2+ preliminary F.C.L. Crespi et al.,PRL113(2014)012501 To be done: cross sections EWSR angular distributions Maria Kmiecik SSNET17

Future plans big reaction chamber KRATTA inside, (p,p’γ) on 208Pb at ~150 MeV (GQR enhancement) (p,p’γ) on 90Zr big reaction chamber KRATTA inside, gamma detectors outside – holders are designed Maria Kmiecik SSNET17

Summary nuclear physics experiment has been performed using proton beam at Cyclotron Center Bronowice IFJ PAN in Krakow gamma decay of giant resonances and „pygmy” states in 208Pb excited using inelastic scattering (p,p’g) reaction have been observed preliminary qualitative results are promising, but to get final information further more quantitative analysis is necessary. It will concern extraction of GQR, GDR and PDR strengths by taking into account branching, cross sections, detector efficiency, angular distribution, etc. the planned continuation concerns experiments using beam at 150 MeV energy on 208Pb target (to compare results for different energies and enhance GQR) and similar reaction for 90Zr target we hope that data obtained at CCB will be complementary to the results obtained at KVI Groningen, iThemba LABS Capetown, RCNP Osaka, LNL Legnaro, University ofCologne Maria Kmiecik SSNET17