Department of Physics

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Nuclear Structure, Nuclear Decays, Rare and Exotic Processes

The nuclear-theory group of JYFL engages in development of nuclear-structure models and their application to topics of weak-interaction physics. The topics include neutrino-nucleus interactions at supernova energies, rare weak decays like high-forbidden beta decays and double beta decays, and direct dark-matter detection. The group is theory member of large experimental underground collaborations, like SUPERNEMO and COBRA. The group has strong theory collaboration with La Plata in Argentina, Bucharest in Romania and Yale University in USA. The group hosts currently one professor, one post-doctoral researcher and four graduate students.

Contact person: Jouni Suhonen

  • Group members »
    • Jouni Suhonen, professor
    • Jenni Kotila, postdoctoral researcher
    • Wafa Almosly, doctoral student
    • Mikko Haaranen, doctoral student
    • Juhani Hyvärinen, doctoral student
    • Pekka Pirinen, doctoral student
    • Lotta Jokiniemi, MSc student
  •  Recent research
    • Rare weak decays, neutrino mass and effective weak coupling constants »


      Rare weak-decay processes owe their slow decay rates to (a) tiny decay energies (Q values), (b) large differences in spins of the initial and final states of decay and (c) decay channels of second order in weak interactions [1,2]. Decays with tiny Q values can be used for detection of the neutrino mass [1,2]. The decays of category (b) can be used, e.g., to probe the effective values of the vector coupling coefficient gV and axial-vector coupling coefficient gA as proposed in [3]. There the electron-spectrum shape of the high-forbidden non-unique beta-decay transitions is shown to be very sensitive to the values of gA and gV, thus enabling the extraction of these values by comparing with the present and future experimental data on the spectrum shape. The degree of sensitivity is shown in Figure 1 for the sample case of the ground-state-to-ground-state decay of 113Cd to 113Sn. The used nuclear-theory framework is the nuclear shell model.

      The effective value of gA can also be studied by comparing the computed results with the data for the Gamow-Teller type of single and double beta decays as discussed in [4-6]. The study of Ref. [7] shows that contributions from the Gamow-Teller 1+ and spin-dipole 2- states are conspicuous in the nuclear matrix elements related to neutrinoless double beta decays. It is thus of paramount importance to study the quenching effects of these contributions through the renormalization of gA. Higher contributions can be addressed through the already mentioned spectrum-shape method of [3].

      Fourth-forbidden non-unique beta-decay transition
      Fourth-forbidden non-unique beta-decay transition from the ground state of Cd-113 to the ground state of Sn-113. Comparison ofthe calculated shape of the electron spectrum with the one measured experimentally.


      [1] J. Suhonen, Phys. Scripta 89 (2014) 054032
      [2] J. Suhonen, EPJ Web of Conferences 66 (2014) 08007
      [3] M. Haaranen, P.C. Srivastava and J. Suhonen, Phys. Rev. C, submitted

    • Neutrinoless double beta decays mediated by various mechanisms »


      In the search for massive Majorana neutrinos and their absolute mass scale the process of neutrinoless double beta (0νββ) decay of atomic nuclei plays a leading role, and once observed would offer new information on many fundamental aspects of elementary particle physics. As major experimental efforts are being made for the observation of this process, another essential step in the study of 0νββ decay is the calculation of nuclear matrix elements and phase-space factors, which are crucial for extracting information on physics beyond the standard model, like the neutrino mass, from the experimental half-lives.

      Several scenarios of neutrinoless double-beta decay have been considered, most notably, light neutrino exchange, heavy neutrino exchange, and Majoron emission. Lately, a comprehensive calculation of the nuclear matrix elements of the neutrinoless double beta decay, mediated by light or heavy Majorana neutrinos, was carried out in [1] by exploiting fast recursive methods [2] to allow computational feasibility. At the same time the effect of deformation on the rates of two-neutrino double beta decay was studied in [3] by using a consistent deformed approach. Possible extension to calculations of the neutrinoless mode are foreseen. These modes of decay were studied experimentally by the NEMO (Neutrino Ettore Majorana Observatory) collaboration for 100Mo in [4]. Majorons were introduced years ago as massless Nambu-Goldstone bosons arising from a global B − L symmetry, broken spontaneously in the low-energy regime. These bosons couple to the Majorana neutrinos and give rise to neutrinoless double-beta decay, accompanied by Majoron emission. Besides neutrinoless double beta decay the Majorons are of great interest since they may play important role also in cosmology and dark-matter searches. Recently we have done an extensive investigation of neutrinoless double beta decay proceeding through emission of one or two Majorons. Combining the obtained predictions with experimental lower bounds, limits on the effective Majoron-neutrino coupling constant can be set [5].

      In recent years, the possible occurrence of sterile massive neutrinos has attracted considerable attention, and searches are under way to detect their presence in oscillation experiments and in accelerator experiments. Several suggestions have been made for the presence of sterile neutrinos with masses from the eV mass all the way up to TeV mass range. Recently we have calculated the nuclear matrix elements and phase-space factors for the exchange of arbitrary mass sterile neutrinos [6] in double beta decay. The thus deduced theoretical 0νββ half-lives can be used to guide planning of future experiments.

      [1] J. Hyvärinen and J. Suhonen, Phys. Rev. C 91 (2015) 024613
      [2] J. Hyvärinen and J. Suhonen, Phys. Rev. C 91 (2015) 054308
      [3] D. S. Delion and J. Suhonen, Phys. Rev. C 91 (2015) 054329
      [4] R. Arnold et al., Phys. Rev. D 92 (2015) 072011
      [5] J. Kotila, J. Barea and F. Iachello, Phys. Rev. C 91 (2015) 064310
      [6] J. Barea, J. Kotila and F. Iachello, Phys. Rev. D 92 (2015) 093001

    • Neutrino-nucleus scattering at supernova energies »
    • Direct WIMP detection rates in 83Kr and 125Te »

      Presently, there exists plenty of evidence of the existence of dark matter. One of the candidate constituents for dark matter is the weakly interacting massive particle (WIMP), motivated by various theoretical models going beyond the standard model. Currently, there are many experimental setups which search for the WIMP signal. In the recent work [1] we analyzed the possibility to use 83Kr as a detector material. The nucleus 83Kr would offer strong kinematic advantages over many other nuclei in the inelastic channel, due to its very low-lying excited state. We found that 83Kr would make a feasible detector material, although the nuclear-structure considerations seem to slightly weaken the promise of the nucleus as a WIMP target. Recently we have extended this work to 125Te target nucleus and specified the WIMP to be the supersymmetry-predicted stable particle, LSP (lightest supersymmetric particle) [2].

      [1] J.D. Vergados, F.T. Avignone III, P. Pirinen, P.C. Srivastava, M. Kortelainen and J. Suhonen, Phys. Rev. D 92 (2015) 015015
      [2] P. Pirinen, P.C. Srivastava, J. Suhonen and M. Kortelainen, Phys. Rev. D, submitted

    • Left-right mixing angle in the left-right extensions of the standard model »

      The minimal extension of the standard model of electroweak interactions allows for massive neutrinos, a massive right-handed boson and a left-right mixing angle. While an estimate of the light (electron) neutrino can be extracted from the non-observation of the neutrinoless double beta decay, the limits on the mixing angle and the mass of the right-handed boson may be extracted from a combined analysis of the double beta decay measurements (GERDA, EXO-200 and KamLAND-Zen collaborations) and ATLAS data on the two-jets two-leptons signals following the excitation of a virtual right-handed boson coupled to a heavy neutrino [1].

      [1] O. Civitarese, J. Suhonen and K. Zuber, J. Phys.: Conf. Series 630 (2015) 012055

  • Recent publications »


    J. Kotila, J. Barea and F. Iachello, Recent theoretical results for 0νββ-decay including R0νECEC and 0νββM, AIP Conf. Proc. 1686 (2015) 020013

    O. Civitarese, J. Suhonen and K. Zuber, Testing left-right extensions of the standard model of electroweak
    interactions with double-beta decay and LHC measurements, J. Phys.: Conf. Series 630 (2015) 012055

    W. Almosly, E. Ydrefors and J. Suhonen, Neutrino scattering off the stable cadmium isotopes: neutral-current processes, J. Phys. G: Nucl. Part. Phys. 42 (2015) 025106

    W. Almosly, E. Ydrefors and J. Suhonen, Neutrino scattering off the stable cadmium isotopes II: charged-current
    processes, J. Phys. G: Nucl. Part. Phys. 42 (2015) 095106

    H. Ejiri and J. Suhonen, GT neutrino-nuclear responses for double beta decays and astro neutrinos, J. Phys. G: Nucl. Part. Phys. 42 (2015) 055201

    F. Iachello, J. Barea and J. Kotila, Recent results in double beta decay, Nucl. Part. Phys. Proc. 265-266 (2015) 25

    J. Barea, J. Kotila and F. Iachello, 0νββ and 2νββ nuclear matrix elements in the interacting boson model with
    isospin restoration, Phys. Rev. C 91 (2015) 034304

    J. Kotila, J. Barea and F. Iachello, Phase-space factors and half-life predictions for Majoron emitting β-β--decay, Phys. Rev. C 91 (2015) 064310

    J. Kotila, J. Barea and F. Iachello, Erratum: Phase-space factors and half-life predictions for Majoron emitting β-β--decay, [Phys. Rev. C 91 (2015) 064310] Phys. Rev. C 92 (2015) 029903

    J. Barea, J. Kotila and F. Iachello, Limits on sterile neutrino contributions to neutrinoless double beta decay, Phys. Rev. D 92 (2015) 093001

    D. S. Delion and J. Suhonen, Double-beta decay within a consistent deformed approach, Phys. Rev. C 91 (2015) 054329

    E. Ydrefors, J. Suhonen and Y. M. Zhao, Neutrino-nucleus scattering off 136Xe, Phys. Rev. C 91 (2015) 014307

    J. Hyvärinen and J. Suhonen, Nuclear matrix elements for 0νββ decays with light or heavy Majorana-neutrino exchange, Phys. Rev. C 91 (2015) 024613

    J. Hyvärinen and J. Suhonen, Recursive method for computing matrix elements for two-body interactions, Phys. Rev. C 91 (2015) 054308

    P. Pirinen and J. Suhonen, Systematic approach to β and 2νββ decays of mass A=100-136 nuclei, Phys. Rev. C 91 (2015) 054309

    R. Arnold, C. Augier, J. D. Baker, A. S. Barabash, A. Basharina-Freshville, S. Blondel, S. Blot, M. Bongrand, V. Brudanin, J. Busto, A. J. Caffrey, S. Calvez, C. Cerna, J. P. Cesar, A. Chapon, E. Chauveau, D. Duchesneau, D. Durand, V. Egorov, G. Eurin, J. J. Evans, L. Fajt, D. Filosofov, R. Flack, X. Garrido, H. Gómez, B. Guillon, P. Guzowski, R. Hodák, A. Huber, P. Hubert, C. Hugon, S. Jullian, A. Klimenko, O. Kochetov, S. I. Konovalov, V. Kovalenko, D. Lalanne, K. Lang, Y. Lemiére, T. Le Noblet, Z. Liptak, P. Loaiza, G. Lutter, F. Mamedov, C. Marquet, F. Mauger, B. Morgan, J. Mott, I. Nemchenok, M. Nomachi, F. Nova, F. Nowacki, H. Ohsumi, R. B. Pahlka, F. Perrot, F. Piquemal, P. Povinec, P. P\v ridal, Y. A. Ramachers, A. Remoto, J. L. Reyss, B. Richards, C. L. Riddle, E. Rukhadze, R. Saakyan, X. Sarazin, Yu. Shitov, L. Simard, F. Šimkovic, A. Smetana, K. Smolek, A. Smolnikov, S. Söldner-Rembold, B. Soulé, I. Štekl, J. Suhonen, C. S. Sutton, G. Szklarz, J. Thomas, V. Timkin, S. Torre, Vl. I. Tretyak, V. I. Tretyak, V. I. Umatov, I. Vanushin, C. Vilela, V. Vorobel, D. Waters and A. Žukauskas, Results of the search for neutrinoless double-β decay in 100Mo with the NEMO-3 experiment, Phys. Rev. D 92 (2015) 072011

    J. D. Vergados, F. T. Avignone III, P. Pirinen, P. C. Srivastava, M. Kortelainen and J. Suhonen, Theoretical direct WIMP detection rates for transitions to the first excited state in 83Kr, Phys. Rev. D 92 (2015) 015015

    E. Ydrefors, W. Almosly and J. Suhonen, Nuclear structure and neutrino-nucleus reactions at supernova energies, Rom. Journ. Phys. 60 (2015) 836