High-resolution Studies of Charge Exchange on 47,48Ti in comparison with Shell Model Calculations Ela Ganioğlu Istanbul University E. Ganioglu, Stockholm , June 2017

Outline Charge exchange (CE) reactions High resolution (3He,t) experiments @ RCNP : 47,48Ti(3He,t)47,48V B(GT) derivation Interpretion of the results using Shell Model description Comparison with mirror beta decay Summary The outline of my talk as follows….. E. Ganioglu, Stockholm , June 2017

*T.N. Taddeucci et. al., NPA469 (1987) 125. Charge – Exchange Reactions Strong interaction process Reaction is governed by στ operator No restriction in excitation energy of states populated in Gamow-Teller transitions unlike beta-decay Proportionality: at incident beam energies >100 MeV/u at the scattering angle 0 ° 3He Target 3t *T.N. Taddeucci et. al., NPA469 (1987) 125. E. Ganioglu, Stockholm , June 2017

Y. Fujita et al., EPJA 13 (‘02) J. Rapaport et al. NPA (‘83) 40 years before  individual transitions were poorly studied due to the limited energy resolution ( 300 keV) in (p,n) reactions.  Not easy to calibrate the unit cross section by using standard B(GT) values from -decay studies on a level-by-level base.* With the development of full beam matching techniques realized an energy resolution of  30 keV in (3He,t) reactions can be obtained at an intermediate energy of 420 MeV and 0°.  One order-of-magnitude better energy resolution  In the pioneering (p,n) reactions it was not possible to resolve states populated in GT transitions. Y. Fujita et al., EPJA 13 (‘02) H. Fujita et al., PRC75 (‘07) 034310 J. Rapaport et al. NPA (‘83)

Dispersion Matching Techniques RCNP LAS Spectrometer Target Tritium 3H 3He++ Dispersion Matching Techniques were applied! WS Beam Line The experiment were performed at 140 MeV/n and at 0 degree. WS (West Experimental Hall-South Inlet Port) And then beam goes to the beamline. which is made like a S shape to make energy spread of the beam as small as possible. In the beam line beam bends with dipol magnets and focus with quadrupole magnets. It comes to target position. and outgoing particle (t) goes through the Grand-Raiden spectrometer. GrRspectormeter consists of (D1,D2,DSR) magnets,two quadrupoles,a sextupole and multipole.But we don’t use DSR magnet in our experiments because it is needed only for the mesurement of spin rotation. And then particles comes to the MWDC. MWDC helps us to get position information of particle and finally it detects with plastic scintillators. Using the high quality beam and the detector system of the highest resolution in the world enable us to accumulate the knowledge of nuclear reactions and structures. T. Wakasa et al., NIM A482 (’02) 79. Ring Cyclotron E. Ganioglu

(3He,t) type CE reactions @ RCNP 47Ti → 0.85 mg/cm2 48Ti → 0.50 mg/cm2 @ 140 MeV/n There is a programme of measurements in the fp-shell looking at how their properties change with Z and N. In this talk I will focus on (He3,t) type Charge Exchange reactions on the stable 46,47,48Ti targets that lead to their V isobars….. These studies make use of the high resolution facility at RCNP. N=Z E. Ganioglu, Stockholm , June 2017

E. Ganioğlu et al., Phy. Rev. C 87, 014321 (2013) Resolution 20 keV Here we see the energy spectrum of 47V . As seen from the spectrum the Jπ= 3/2−, ground state (g.s) of 47V was well separated from the near-by 5/2−, Ex = 88 keV state and the 7/2−, 146 keV state. In 47V, the proton separation energy Sp is at 5.17MeV, and the main part of the GT strength is distributed above this energy of Ex = 5 MeV. In addition, the strength is much fragmented and wide spread. Therefore it is interesting to see that there are clear sharp peaks even at excitation energies more than 6 − 7 MeV. In the spectra he labeled energies are in agreement with the values of NNDC within 5 keV. Sp=5.17 MeV The main part of the GT strengths is distributed above this energy E. Ganioğlu et al., Phy. Rev. C 87, 014321 (2013) E. Ganioglu, Stockholm , June 2017

Resolution 21 keV Sp= 6.83 MeV Here we see the energy spectrum of 48V. The resolution is 21 keV in this case. From these one can derive the bgts Given the excellent high resolution – quality- the next step is from the measured intensities of the observed allowed gt transitions to derive values of the B(GT)s. E. Ganioğlu et al., PRC 93,064326 (2016) E. Ganioglu, Stockholm , June 2017

B(GT) Derivation R2 for 48V = 8.2±0.4 In the A=47 system, a standard B(GT) is obtained from b-decay of 47V Y. Fujita et al., Prog. In Part. And Nucl. Phys. 66, (2011) For the case of 47V B-decay info can be obtained indirectly. In order to derive the B(F) value in A = 48 nucleus the the ratio of (GT and Fermi unit cross-sections) R2 was used assuming all the Fermi transition strength concentrates in the IAS, and it consumes the complete sum rule value of B(F) = N − Z, Recently, the A dependence of R2 was systematically studied, and a smooth increase of R2 was observed as a function of A. A value of 8.2±0.4 can be deduced for the A = 47 nuclei by quadratically interpolating the experimentally obtained R2 values for the A =7~178 nuclei respectively. R2 for 48V = 8.2±0.4 E. Ganioglu, Stockholm , June 2017

Comparison – cumulative B(GT)s of 47V and 48V Similar Behavior  2 MeV The main difference is that the jump in the accumulated B(GT), seen both in theory and experiment, is delayed in energy by ≈2 MeV in the case of the odd nucleus 47V. This can be explained in terms of the diagrams where we are concerned with the particles and interactions between them in 47V and 48V. SM calculations by M. Honma, Aizu University, Japan SM calculations: with GXPF1 interaction E. Ganioglu, Stockholm , June 2017

In case of 48Ti; should populate states in 48V at higher energy.   We populate proton-neutron excitations which are the lowest possible excitations in the odd-odd 48V nucleus. should populate states in 48V at higher energy.   f7/2 p3/2 f 5/2 should populate states in 48V at low energy. In the case of 48Ti, we start with even numbers of protons and neutrons. In a GT transition one of the neutrons in a pair in the f7/2 orbital is transformed into a proton in the 48V final nucleus, hence we populate proton-neutron excitations which are the lowest possible excitations in the odd-odd nucleus 48V. There are two possibilities for such GT transitions, see Fig. 5(c): νf7/2 → πf7/2, which should populate states lying at low energy, and (ii) νf7/2 → πf5/2, which should populate states in 48V at higher energy. E. Ganioglu, Stockholm , June 2017

In case of 47Ti – (I) should populate states in 4V at higher energy.   f7/2 p3/2 f 5/2 should populate states in 4V at low energy. Initially we have a valence neutron in the νf7/2 orbital in 47Ti. E. Ganioglu, Stockholm , June 2017

(II) if we think of GT transitions involving a neutron from the (νf7/2)2 pairs   f7/2 p3/2 f 5/2 We have to break the pair first, which typically costs ≈2 MeV ! similar to 48V case -> adding the extra odd neutron in 47V but shifted by the pairing energy of ≈2 MeV E. Ganioglu, Stockholm , June 2017

The accumulated strength of 47V up to12 MeV should be similar to the accumulated strength in 48V up to 10 MeV. Since in the 47V case there are four paired neutrons and one odd neutron and in the 48V case there are six paired neutrons, the accumulated strength of 47V up to 12 MeV should be similar to the accumulated strength in 48V up to 10 MeV. to take into account the energy shift, corrected by the number of neutron pairs and the odd neutron in the f7/2 orbital, namely, 3.5 × 5/6 = 2.9, which is close to the value of 3.2 observed. 3.5 * 5/6 = 2.9 E. Ganioglu, Stockholm , June 2017

Comparison – cumulative B(GT)s SM calculation of 47V and energy shifted 48V To verify if this effect is reproduced by the calculations, we have shifted the energy of the shell-model calculations for 48Ti → 48V by 2 MeV, scaled by a factor of 5/6 = 0.833 and compared with SM calculations for 47Ti → 47V. E. Ganioglu, Stockholm , June 2017

Comparison – cumulative B(GT)s of 47V and energy shifted 48V In the same way, we have shifted the experimental accumulated strength distribution, scaled by 0.833 and by 2 MeV and compared it with the 47V distribution in Fig. 6(b). The agreement is remarkable in both cases, which gives us some confidence in our interpretation. E. Ganioglu, Stockholm , June 2017

Complementary Study: CE reactions: Beta – decay experiments @ GANIL in mirror nuclei Tz=0 Tz=+1 Tz=+2 Tz= -1 Tz= -2 58Ni26+ (74.5 AMeV) + natNi ß-decay A weak interaction process Absolute B(GT) values ß-decay and CE reactions Both governed by στ operators CE reactions Strong interaction process Relative B(GT) values Since CE and beta decay have same operator the two beta decays are mirror processes. Beta decay is governed by the sigma-tau operator (difficult to obtain overall distributions) However, such studies are limited by the q value which mean that the range of the states accessible is limited in excitation energy. E. Ganioglu, Stockholm , June 2017

Comparison of DSSSD from GANIL and CE from RCNP S..E..A. Orrigo, et al., Phy. Rev. C 93, 044336 (2016) Sp= 2018(10) keV ! Some discrepancies In the TZ = -2 proton-rich nuclei the decay is expected to proceed mostly by proton emission However the p-decay of the T = 2 Isobaric Analogue State (IAS) is usually isospin-forbidden, making possible the gamma emission in competition. There are some discrepancies. In particular the 3864 keV 1+ state populated in the CE experiment appears to correspond to three separate states when seen in β decay. The reasons for the differences are not yet understood and will be the subject of further study. The states corresponding to those at 2288 and 2406 keV lying below the IAS and populated in the CE reaction were not seen in the β decay of 48Fe, presumably because of the background of β particles at lower energy in the spectrum. E. Ganioglu, Stockholm , June 2017

Summary and Outlook The 47,48Ti(3He ,t )47,48V reactions were studied at the intermediate beam energy of 140 MeV/nucleon and 0◦ scattering angle. B(GT) distributions for these reactions were derived for states up to 12 MeV and compared with each other and Shell Model calculations. The experimental B(GT) distributions were well reproduced up to 5 MeV for 47V and 9 MeV for 48V. Above these energies SM values exceed the measured values. E. Ganioglu, Stockholm , June 2017

The distributions follow roughly the same pattern but the one for 47Ti(3He,t)47V is shifted to higher energies by about 2 MeV. A qualitative explanation is given in terms of the interactions of the particles involved and more specifically in terms of the transformation of the paired and unpaired valence particles. The results were also compared with the beta-delayed proton spectrum from the mirror Tz = -2 beta decay E. Ganioglu, Stockholm , June 2017

Istanbul – Osaka – Valencia Debrecen – Michigan - Fukushima Tokyo – Köln – Niigata –Münster Collaboration E. Ganioglu, Stockholm , June 2017

Thanks for your attention! E. Ganioglu, Stockholm , June 2017