1. 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)

2. 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

3. 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

4. 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)
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

5. Idea of the experiment
proton beam from the CCB Krakow cyclotron used for medical treatment
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

6. 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

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

8. 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

9. Preliminary results gamma decay to different final states HECTOR
Eg [MeV]
E* [MeV]
HECTOR
208Pb
MeV
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

10. 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

11. 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° °
13.5° °
preliminary
Maria Kmiecik SSNET17

12. 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

13. 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

14. 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