NUMEN_2017. Abstract: Within the NUMEN project it is proposed to study the 130 Te( 20 Ne, 20 O) 130 Xe reaction at

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2 NUMEN_2017 C. Agodi, J. Bellone, R. Bijker, D. Bonanno, D. Bongiovanni, V. Branchina, M.P. Bussa, L. Busso, L. Calabretta, A. Calanna, D. Calvo, F. Cappuzzello, D. Carbone, M. Cavallaro, M. Colonna, G. D Agostino, N. Deshmukh, S. Ferrero, A. Foti, P. Finocchiaro, G. Giraudo, V. Greco, F. Iazzi, R. Introzzi, G. Lanzalone, A. Lavagno, F. La Via, J.A. Lay, G. Litrico, D. Lo Presti, F. Longhitano, A. Muoio, L. Pandola, F. Pinna, S. Reito, D. Rifuggiato, M.V. Ruslan, G. Santagati, E. Santopinto, L. Scaltrito, S. Tudisco INFN - Laboratori Nazionali del Sud, Catania, Italy INFN - Sezione di Catania, Catania, Italy Dipartimento di Fisica e Astronomia, Università di Catania, Catania, Italy INFN - Sezione di Torino, Torino, Italy Politecnico di Torino, Italy INFN - Sezione di Genova, Genova, Italy CNR-IMM, Sezione di Catania, Italy Università degli Studi di Enna "Kore", Enna, Italy T. Borello-Lewin, P. N. de Faria, J.L. Ferreira, R. Linares, J. Lubian, N.H. Medina, J.R.B. Oliveira, M.R.D. Rodrigues, D.R. Mendes Junior, V. Zagatto Instituto de Física, Universidade Federal Fluminense, Niterói, RJ, Brazil Instituto de Física, Universidade de São Paulo, São Paulo, SP, Brazil X. Aslanoglou, A. Pakou, O. Sgouros, V. Soukeras, G. Souliotis, Department of Physics and HINP, The University of Ioannina, Ioannina, Greece Department of Chemistry and HINP, National and Kapodistrian University of Athens, Greece E. Aciksoz, I. Boztosun, A. Hacisalihoglu, S.O. Solakcı, Akdeniz University, Antalya, Turkey L. Acosta, E.R. Chávez Lomelí, Universidad Nacional Autónoma de México S. Boudhaim, M.L. Bouhssa, Z. Housni, A. Khouaja, J. Inchaou Université Hassan II Casablanca, Morocco N. Auerbach, School of Physics and Astronomy Tel Aviv University, Israel H. Lenske, University of Giessen, Germany Spokespersons: F. Cappuzzello (cappuzzello@lns.infn.it) and C. Agodi (agodi@lns.infn.it) Abstract: Within the NUMEN project it is proposed to study the 130 Te( 20 Ne, 20 O) 130 Xe reaction at 15 MeV/u, using the MAGNEX spectrometer at zero degree.

3 Physics case The NUMEN project [1] proposes an innovative technique [2] to access the nuclear matrix elements entering the expression of the life time of the neutrinoless double beta decay by relevant cross sections of double charge exchange reactions. Last year a detailed document describing the main aspects of the project was presented to the INFN-LNS PAC Committee and beam time requests were addressed accordingly. In particular, 45 BTU were assigned by the LNS for the exploration of the 116 Sn( 18 O, 18 Ne) 116 Cd at 15 MeV/u, 60 BTU for the same reaction at 25 MeV/u and 12 BTU for the feasibility test of the ( 20 Ne, 20 O) reaction on 116 Cd target at 15 and 22 MeV/u. In the Status Report document, attached to this Proposal, we give some preliminary results of these experiments. Based on the NUMEN research plan, presented last year (see Table 1 at page 3), the next step would have been the measurement in 2017 of the ( 20 Ne, 20 O) reaction on 116 Cd, 130 Te and 76 Ge. Following the PAC recommendation, the long experiment on 116 Cd was postponed after the positive results of the tests. A new element to be considered now is the approval of the NURE project from the European Research Council to one of the members of the NUMEN collaboration (namely M. Cavallaro). Moreover, the NURE project has a large overlap with the foreseen activity of NUMEN Phase 2 experimental activity. In particular, the ( 20 Ne, 20 O) reaction on 116 Cd and 76 Ge are foreseen by NURE, as a consequence we will not propose such experiments to the PAC in order to avoid duplications. Therefore, taking also into account the results of the feasibility tests of the ( 20 Ne, 20 O) reaction, we propose to submit to the PAC the remaining experiment on 130 Te( 20 Ne, 20 O) 130 Xe reaction at 15 MeV/u for The 130 Te gs 130 Xe gs transition is indeed very interesting, since it represents the basic nuclear process explored by the CUORE experiment [3] at the Gran Sasso Laboratory and it is one of the hottest cases for the 0 decay research. Experimental procedure The experiment will be performed using the beam accelerated at 15 MeV/u by the LNS K800 Superconducting Cyclotron which, according to our previous experiments, can be tuned in order to guarantee an energy resolution of about 1/1000 and can be efficiently transported to the MAGNEX experimental room. MAGNEX will be positioned with its optical axis located at θ opt = -3, which includes zero degree, with magnetic fields set in order to transport the beam into the focal plane Faraday cup, for charge collection. The beam current will be kept at the maximum tolerated by the focal plane detector, which from our previous experience is about 50 ena. The count rate was estimated on the basis of the results of the tests with 20 Ne beam on 116 Cd target of 1.3 mg/cm 2, where the collected dataset was about 6 counts for the ground to ground state transition integrated from 0 to about 8 in the laboratory frame. Assuming a similar cross section for the 130 Te and a target thickness of about 300 g/cm 2, we can estimate a yield of about 120 counts in 60 BTU collection time with a beam intensity of about 40 ena. This includes the study of the other interesting reaction channels, as one- and two-proton stripping, single charge exchange, elastic and inelastic scattering. 6 BTU will be necessary for the spectrometer set-up and detectors optimization. Taking this into account, we propose to perform a run of 66 BTU.

4 Bibliography [1] F. Cappuzzello, C. Agodi et al. NUMEN: Determining the Nuclear Matrix Elements of Neutrinoless Double Beta Decays by Heavy-Ion Double Charge Exchange Reactions. Proposal of the project submitted to INFN. [2] F. Cappuzzello, M. Cavallaro et al., Heavy-ion double charge-exchange reactions: a tool towards 0νββ nuclear matrix elements Eur. Phys. J. A (2015) 51: 145. [3] K. Alfonso et al. (CUORE Collaboration). Search for Neutrinoless Double-Beta Decay of Te-130 with CUORE-0. Phys. Rev. Lett. 115, (2015).

5 Report on the experiment and data reduction activity NUMEN 2016 In 2016, 45 Beam Time Units (BTU) were assigned by the LNS to the NUMEN project for the exploration of the 116 Sn( 18 O, 18 Ne) 116 Cd at 15 MeV/u, 60 BTU for the same reaction at 25 MeV/u and 12 BTU for feasibility tests of the ( 20 Ne, 20 O) reaction on 116 Cd target at 15 and 22 MeV/u. We briefly report here on the preliminary results of the experiment 116 Sn( 18 O, 18 Ne) 116 Cd at 15 MeV/u and the tests of the ( 20 Ne, 20 O) reaction on 116 Cd target at 15 and 22 MeV/u. The experiment 116 Sn( 18 O, 18 Ne) 116 Cd at 22 MeV/u is scheduled from next November 16 th ) Study of the 18 O Sn at 15 MeV/u This experiment was performed in June 2016, based on the results of a feasibility test of the same experiment performed in October The 18 O 4+ ions accelerated by the CS were fully stripped by a thin carbon foil mounted just after the accelerator extraction channel. The obtained 18 O 8+ ions were transmitted to the MAGNEX spectrometer with good efficiency and halo-free. The latter is a crucial requirement for the zero-degree measurement foreseen by NUMEN. A maximum beam current of about 8 ena on a 323 ug/cm Sn target was tolerated by the MAGNEX focal plane detector. The average current was about 5 ena. In these conditions, a total of about 2.7 mc of electric charge was integrated in the Faraday cup, located beside the focal plane detector. An energy resolution of about 500 kev FWHM was achieved for the detected Neon ejectiles, estimated by isolated transitions populated in the ( 18 O, 19 Ne) proton pick-up channel. The measured resolution is in agreement with that expected by simulations and it is enough to separate the transitions to 116 Cd g.s. populated in the double charge exchange channel from those to the excited states of the ejectile and residual nucleus. The following channels were explored: Double charge exchange (DCE) 116 Sn( 18 O, 18 Ne) 116 Cd Single charge exchange (CEX) 116 Sn( 18 O, 18 F) 116 In Two-proton transfer 116 Sn( 18 O, 20 Ne) 114 Cd Two-neutron transfer 116 Sn( 18 O, 16 O) 118 Sn Despite the experiment is very recent, some preliminary data is already available for initial considerations. Fig. 1 shows an example of the identification of the Ne isotopes by the focal plane detector. 20 Ne (two-proton channel) and 18 Ne (DCE channel) loci are indicated. The details of the identification technique are published in Ref. [F. Cappuzzello et al., Nucl. Instr. And Meth. A 621 (2019) 419]. Fig. 2 shows an example of identification plots in the case of 18 F ejectile (CEX channel).

6 Fig. 1. Typical identification plot for the 18 O Sn experiment at 15 MeV/A. (Top panel) E - E resid plot, a graphical gate in the region corresponding to the Ne 10+ ions is drawn. (Bottom panel) X foc - E resid plot gated under the graphical condition drawn in the top panel. Fig. 2. Typical identification plot for the 18 O Sn experiment at 15 MeV/A. (Top panel) E - E resid plot, a graphical gate in the region corresponding to the F 9+ ions is drawn. (Bottom panel) X foc - E resid plot gated under the graphical condition drawn in the top panel.

7 Fig. 3 shows a preliminary plot of the parameters θ foc (horizontal angle) and X foc (horizontal position), measured at the focal plane for the selected 20 Ne ejectiles (two-proton transfer channel). The red points in the figure represent the simulated events of the transitions due to 12 C contaminant in the target. The events which are at the right side of the transition to the 12 C( 18 O, 20 Ne) 10 Be g.s. are due to the 116 Sn and are free from contamination. A supplementary run on carbon target was also performed for background subtraction. We notice a clear suppression of the L = 0 two-proton transfer transition to the residual ground state for both 116 Sn and 12 C target. Interestingly, this resembles what observed in Ref. [F. Cappuzzello et al. EPJ A (2015) 51: 145] for the same reaction on 40 Ca target. However only after the extraction of the absolute cross section we will be able to discuss this point on a quantitative ground. Fig.4 shows a θ foc - X foc plot for a partial data-set in the case of identified 18 Ne ejectiles (DCE channel). Counts are observed in the region of the expected DCE transition to 116 Cd ground state around zero degree. The next step of the analysis with ray-reconstruction and extraction of energy spectra, angular distributions and absolute cross-section is in progress. Fig. 3. θ foc - X foc correlation for the identified two-proton transfer channel: ( 18 O, 20 Ne) at 15 MeV/u. The red points are the results of simulation with a narrow cut in the vertical phase space for the transition to 12 C( 18 O, 20 Ne gs) 10 Be gs and excited states, due to the presence of 12 C contamination in the target. Fig. 4. θ foc - X foc correlation for the identified DCE channel: 116 Sn( 18 O, 18 Ne) 116 Cd at 15 MeV/u. The red line is the result of simulation with a narrow cut in the vertical phase space for the transition to the 116 Cd gs

8 2) Test of the 20 Ne Cd reaction at 15 e 22 MeV/u This feasibility test was performed in March 2016 at two different incident energies. We remark that, to our knowledge, no available study is present in literature regarding the double charge exchange channel induced by 20 Ne beam. As in the case of 18 O ions, the accelerated 20 Ne were fully stripped at the exit of the CS. The 20 Ne 10+ ions were transmitted to MAGNEX with good efficiency and halo-free. However, we found that the thin 116 Cd target in the MAGNEX scattering chamber redistributes the beam charge states with non-negligible components of 9 + and 8 + at the exit of the target. These charge states are particularly important since 20 Ne 9+ and 20 Ne 8+ ions from the beam have a magnetic rigidity which is within the momentum acceptance of the spectrometer. As a consequence, they generate a disturbing background which could severely limit the beam current tolerated by the detector. Two aluminum shields 3 mm thick, were mounted in front of the focal plane detector, reducing the momentum acceptance just to stop these unwanted 20 Ne 9+ and 20 Ne 8+ ions. However, the background was still large, preventing to go above 1 ena beam current. For this reason, we introduced a further stripper foil (Carbon 960 g/cm 2 thick) in the MAGNEX scattering chamber just after the 116 Cd target. We found that, in these conditions, the background induced by 20 Ne 9+ and 20 Ne 8+ components of the beam is safely low, allowing to run at beam intensity as high as 15 ena. The use of poststripper foils is thus mandatory in these experiments. The data were collected with the spectrometer optical axis set at θ opt = -3, which corresponds to an accepted angular range of 0 < θ lab < 8. An average current of about 9 ena on a 1380 g/cm Cd target was measured. In these conditions, a total of about 0.35 mc of collected charge was integrated in the Faraday cup, located beside the focal plane detector. An energy resolution of about 500 kev FWHM was achieved from the detected Oxigen ejectiles, which is enough to separate the 116 Sn gs populated in the double charge exchange channel from the first excited states. This resolution is in agreement with that expected by simulations. The following channels were explored: Double charge exchange (DCE) 116 Cd( 20 Ne, 20 O) 116 Sn Single charge exchange (CEX) 116 Cd( 20 Ne, 20 F) 116 In Two-proton transfer 116 Cd( 20 Ne, 18 O) 118 Sn What described so far is common to the measurements at the two incident energies. Instead, there is an aspect that affected only the run at 22 MeV/u. In this case the ejectiles are emitted at an energy too high to be stopped by the silicon detectors 1000 m thick, used in the MAGNEX focal plane detector. Therefore, to avoid the punch-through effect, which would prevent a clear identification of the ejectiles of interest, an aluminum shield of 100 m thickness was placed just in front of the silicon detectors, after the sensitive gas section of the focal plane detector, as shown in Fig. 5. The insertion of this screen, however, produces a different energy loss of the ions according to their trajectory. The different energy loss based on the horizontal angle causes a deterioration of the resolution in the identification of the ions. We can obviate this phenomenon off-line by correcting, event to event, the energy loss in the aluminum foil, taking into account the horizontal angle measured. The reduction of these data is in progress.

9 Fig. 5. Layout of the MAGNEX focal plane detector (top view). The black line indicated by the arrow corresponds to the aluminum foil inserted in the 22 MeV/u run. The red arrows indicate two possible ion trajectories characterized by a different horizontal angle θ foc. An example of ion identification in the 20 Ne Cd test is shown in Fig. 6. Since the used technique refers to the Lorentz force acting on an ion moving in a uniform magnetic field, we are sensitive to m/q ratio (see Ref. [F. Cappuzzello et al., Nucl. Instr. And Meth. A 621 (2019) 419] for details). So in the X foc - E resid representation, the 20 O 8+ and 20 F 8+ ions will lie almost in the same locus, as you can see in the left panel of Fig. 6. The two species can be distinguished considering the ΔE - E correlation (right panel of Fig. 6) which shows the data obtained by selecting the area of 20 O 8+, 20 F 8+ and 20 Ne 8+ in Fig Ne Sn at 15 MeV/u 0 < < 20 Ne Sn at 15 MeV/u 0 < < Fig. 6. Left panel: Example of X foc E resid ion identification plot. The oxygen ions are shown in black, the fluorine ions in red and neon ions in green. The mass number and charge state are also indicated. The locus of green points indicated as 20 Ne_slit_scatt corresponds to events arising from slit-scattering of the 20 Ne beam. These particles reach the detector in a way not related to the optics of the spectrometer and, for this reason, do not follows the m/q correlation. Right panel: Example of ΔE - E resid plot after the graphical selection of the region where 20 O 8+, 20 F 8+ e 20 Ne 8+ data are observed in the plot of Fig. 8. One can see that the three ions can be easily separated after this double selection.

10 After the ion identification, the trajectory reconstruction technique implemented in MAGNEX is applied and the momentum vector is reconstructed at the target position for each selected ion (see [F. Cappuzzello et al., Nucl. Instr. And Meth. A 638 (2011) 74]). Q-value and excitation energy E x = Q 0 Q (where Q 0 is the ground to ground state reaction Q-value) are then constructed based on relativistic two-body kinematics, as shown in Fig. 7 for the DCE and two-proton transfer channel. Interestingly the two-proton channel transfer cross section for the transition to 118 Sn ground and low lying state is strongly suppressed, as a consequence of kinematic mismatch for the nucleon transfer mechanism at these energies. Differently the DCE transitions to 116 Sn and first excited 2 + state at 1.29 MeV are clearly separated and characterized by a remarkable cross section of about 14 nb and 11 nb, respectively. The reduction of these data is ongoing. 116 Cd( 20 Ne, 18 O) 118 Sn at 15 MeV/u 0 < < 116 Cd( 20 Ne, 20 O) 116 Sn at 15 MeV/u 0 < < PRELIMINARY Fig. 7. Left panel: reconstructed energy spectrum (E x = Q 0 Q) of the 116 Cd( 20 Ne, 18 O) 118 Sn two-proton stripping reaction at 15 MeV/u 0 < < 8. Right panel: reconstructed energy spectrum of the 116 Cd( 20 Ne, 20 O) 116 Sn DCE reaction at 15 MeV/u 0 < < 8.

11 List of NUMEN publications 1. The MAGNEX spectrometer: Results and perspectives F. Cappuzzello, C. Agodi, D. Carbone and M. Cavallaro, Eur. Phys. J. A (2016) 52: 167. DOI /epja/i Using double charge exchange reactions towards 0νββ nuclear matrix elements M. Cavallaro, F. Cappuzzello, C. Agodi, S. Calabrese, D. Carbone, A. Foti, G. Santagati, V. Zagatto, Acta Phys. Pol. B, 47, (2016). DOI: /APhysPolB The nuclear matrix elements of 0nbb decay and the NUMEN project at INFN-LNS F. Cappuzzello, C. Agodi, E. Aciksoz, L. Acosta, X. Aslanouglou, N. Auerbach, R. Bijker, D. Bonanno, D. Bongiovanni, T. Borello, S.Boudhaim, M.L. Bouhssa, I. Boztosun, L. Calabretta, A. Calanna, D.Carbone, M. Cavallaro, D. Calvo, E.R. Chavez Lomeli, M. Colonna, G. D'Agostino, N. Deshmukh, P.N.de Faria, A. Ferrero, A. Foti, P. Finocchiaro, P.R.S. Gomes, V. Greco, A. Hacisalihoglu, Z. Housni, A.Khouaja, J. Inchaou, G. Lanzalone, F. La Via, J.A. Lay, H. Lenske, R. Linares, J. Lubian, F. Iazzi, R.Introzzi, A. Lavagno, D. Lo Presti, N. Medina, D. R. Mendes, A. Muoio, J.R.B. Oliveira, A. Pakou, L.Pandola, D. Rifuggiato, M.R.D. Rodrigues, G. Santagati, E. Santopinto, L. Scaltrito, O. Sgouros, S.O.Solakci, V. Soukeras, S. Tudisco, R.I.M. Vsevolodovna, V. Zagatto, Journal of Physics: Conf. Series 730 (2016) Doi: / /730/1/ NUMEN LNS: Heavy Ions Double Charge Exchange as a tool towards the 0νββ nuclear matrix elements C.Agodi, F. Cappuzzello, D. L. Bonanno, D. G. Bongiovanni, V. Branchina, S. Calabrese, L. Calabretta, A. Calanna, D. Carbone, M. Cavallaro, M. Colonna, A. Foti, P. Finocchiaro, V. Greco, G. Lanzalone, D. Lo Presti, F. Longhitano, A. Muoio, L. Pandola, D. Rifuggiato and S. Tudisco Journal of Physics: Conference Series, 724, (2016). Doi: / /724/1/ The nuclear matrix elements of 0νββ decay and the NUMEN project at INFN-LNS F. Cappuzzello, C. Agodi, F. Balestra, R. Bijker, D. Bonanno, D. Bongiovanni, V. Branchina, S. Calabrese, L. Calabretta, A. Calanna, D. Calvo, D. Carbone, M. Cavallaro, M. Colonna, S. Ferrero, A. Foti, P. Finocchiaro, G. Giraudo, V. Greco, F. Iazzi, R. Introzzi, G. Lanzalone, A. Lavagno, D. Lo Presti, F. Longhitano, A. Muoio, L. Pandola, D. Rifuggiato, M.V. Ruslan, E. Santopinto, L. Scaltrito, S. Tudisco, V. Zagatto EPJ Web of Conferences 117, (2016) DOI: /epjconf/ Silicon carbide detectors study for NUMEN project A.Muoio, C. Agodi, D.L. Bonanno, D.G. Bongiovanni, S. Calabrese, L. Calcagno, D. Carbone, M. Cavallaro, F. Cappuzzello, A. Foti, P. Finocchiaro, G. Lanzalone, F. La Via, F. Longhitano, D. Lo Presti, L. Pandola, S. Privitera, S. Tudisco EPJ Web of Conferences 117, (2016) DOI: /epjconf/ Heavy-ion double charge exchange reactions: A tool toward 0νββ nuclear matrix elements F. Cappuzzello, M. Cavallaro, C. Agodi, M. Bondi, D. Carbone, A. Cunsolo and A. Foti, Eur. Phys. J. A 51:145 (2015). DOI: /epja/i

12 8. Heavy Ions Double Charge Exchange reactions: towards the 0νββ Nuclear Matrix Element determination C. Agodi, F. Cappuzzello, M. Cavallaro, M. Bondì, D. Carbone, A. Cunsolo, A. Foti, Nuclear and Particle Physics Proc. 265, (2015). DOI: /j.nuclphysbps NUMEN LNS: Heavy Ions Double Charge Exchange reactions towards the 0vββ Nuclear Matrix Element determination C. Agodi, F. Cappuzzello, D. L. Bonanno, D. G. Bongiovanni, V. Branchina, L. Calabretta, A. Calanna, D. Carbone, M. Cavallaro, M. Colonna, G. Cuttone, A. Foti, P. Finocchiaro, V. Greco, G. Lanzalone, D. Lo Presti, F. Longhitano, A. Muoio, L. Pandola, D. Rifuggiato, and S. Tudisco AIP Conf. Proc. 1686, (2015). DOI: / The role of nuclear reactions in the problem of 0 nu beta beta decay and the NUMEN project at INFN- LNS F. Cappuzzello, C. Agodi, M. Bondì, D. Carbone, M. Cavallaro, A. Foti Journal of Physics Conference Series 630, (2015). DOI: / /630/1/ ( 18 O, 18 Ne) Double Charge-Exchange with MAGNEX M. Bondí, F. Cappuzzello, C. Agodi, D. Carbone, M. Cavallaro, A. Cunsolo, M. De Napoli, A. Foti, D. Nicolosi, and S. Tropea, AIP Conf. Proc (2014) 245. Doi: /