| Time | Title | Speaker |
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Session I (09:30-10:30)
Chair:---- (----) |
| 09:30 | Towards next-generation nuclear matrix elements for double-beta decay (09:30-10:30)
Abstract:
I will give a review on recent advances in the evaluation of the nuclear matrix elements (NMEs) of neutrinoless double-beta decay. The calculation of the NMEs requires knowledge of both the structure of the involved nuclei and the operators mediating the decay. First, I will discuss the evaluation of recent effective-field-theory corrections to the double-beta-decay operators and their effect on the theory predictions in medium-heavy to heavy nuclei. I will also discuss how the theory predictions can be constrained by other nuclear observables that can be or have been measured.
| Lotta Jokiniemi (TRIUMF) |
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| 10:00 |
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| 10:30 | Coffee Break(10:30-10:50) |
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Session II (10:50-11:50)
Chair:---- (----) |
| 10:50 | Double beta decay in the EDF-mapped IBM (10:50-11:20)
Abstract:
Recent applications of the interacting boson model that is based on the energy density functional to the calculations of double beta decay nuclear matrix elements are presented. By using as microscopic input the results of the self-consistent mean-field calculations employing a universal EDF, the nuclear wave functions for the even-even and odd-odd nuclei, and the Gamow-Teller and Fermi transition operators are obtained. This procedure allows for a consistent description of the low-lying structure of each nucleus and double beta decay NMEs without the closure approximation, reducing significantly the phenomenological adjustments. Parameter sensitivity of this framework is also discussed toward an improved description of the NMEs.
| Kosuke Nomura (Hokkaido University) |
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| 11:00 |
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Uncertainty quantification of nuclear double-beta decay with a covariant energy density functional (11:20-11:50)
Abstract:
We present a statistical analysis of nuclear low-lying states within the framework of multireference covariant density functional theory using a relativistic point-coupling energy density functional. This study is made possible by the newly developed subspace-projected-CDFT, where the wave functions of nuclear low-lying states for target EDF parameter sets are expanded in a subspace spanned by the wave functions of low-lying states from training parameter sets. We analyze the global sensitivity of excitation energies, electric quadrupole transition strengths, and the nuclear matrix element of neutrinoless double-beta decay in Xe136 and Nd150 to EDF parameters, and explore the correlations between these quantities and nuclear matter properties.
| Chenrong Ding (Sun Yat-sen University) |
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| 11:30 |
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| Break(Refreshments)(11:50-13:00) |
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| 12:00 |
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| 12:30 |
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Session III (13:00-14:45)
Chair:---- (----) |
| 13:00 | Double beta decay physics with PandaX-4T liquid xenon detector (13:00-14:00)
Abstract:
PandaX-4T is a liquid xenon time projection chamber (TPC) that searches for dark matter particles and neutrinoless double beta decay of xenon isotopes. In this talk, I will present our latest work on the double beta decay half-life limit established by PadnaX-4T for Xe-136(-134), as well as the effort to utilize the spectral information of Xe-136 decay for NME and new physics analysis.
| Ke Han (Shanghai Jiao Tong University) |
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| 13:30 |
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| 14:00 | Exploring Delayed Gamma-Ray following Ordinary Muon Capture: Insights into Double Beta Decays and Antineutrino Nuclear Responses (14:00-14:30)
Abstract:
The present work examines double beta decay (DBD) through ordinary muon capture (OMC). OMC offers a unique probe into antineutrino nuclear responses (ANR). The delayed gamma rays emitted following OMC provide crucial information about nuclear transitions, enabling precise studies of the nuclear structure for understanding of DBD nuclear matrix elements (NME). The work highlights the unique features of ANR by analyzing OMC rates and nuclear strength function by emphasizing the experimental techniques for detecting delayed gamma rays and their role in mapping nuclear strength functions. Additionally, it explores the potential of OMC experiments by addressing current challenges in experimental design and data interpretation, advancing DBD NME studies and neutrino physics research.
| Izyan Hazwani Hashim (Universiti Teknologi Malaysia) |
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| 14:30 | Double beta decay phase space factor calculation using Coulomb potential determined by density functional theory (14:30-14:45)
Abstract:
The phase space factors include the information on the emitted electron wave functions. They have been calculated by solving the Dirac equation for the emitted electrons by including the finite-size effect (the nuclear charge distribution assuming a uniform charge distribution or derived from Woods-Saxon potential) and the electron screening effect based on the Thomas-Fermi equation.
We are performing a precise calculation of the phase space factor based on the nuclear and electron density functional theory (DFT); nuclear charge distribution based on the nuclear DFT and the electron screening effect based on the electron DFT.
In this presentation, I will show the results of the phase space factor calculation for double-beta decaying nuclei based on the nuclear/electron DFT.
| Atsuya Kanai (University of Tsukuba) |
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| Coffee Break(14:45-15:05) |
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| 15:00 |
Session IV (15:05-17:05)
Chair:--- (---) |
| 15:05 | Improved description of double beta decay (15:05-15:35)
Abstract:
We present the Taylor expansion formalism for describing the two-neutrino double-beta (2νββ)-decay. In predicting the 2νββ-decay spectra we include the radiative and atomic exchange correction. We also investigate the impact of the electron phase shift on the angular correlation between the emitted electrons. Additionally, we examine the contribution of all s-wave electrons available for capture in the two-neutrino double electron capture (2νECEC) processes, going beyond the K and L1 orbitals considered in prior studies. Finally, we propose a semi-empirical formula (SEF) for calculating the nuclear matrix elements (NMEs) for both the 2νββ-decay and 2νECEC process. Compared with the previous phenomenological and nuclear models, the SEF yields the best agreement with the experimental NMEs.
| Ovidiu Nitescu (FMFI, Comenius University in Bratislava) |
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| 15:30 |
Two neutrino double beta decay search by the PIKACHU experiment (15:35-16:05)
Abstract:
The PIKACHU experiment is a search for the double beta decay of ^{160}Gd using Ce:Gd_3Al_2Ga_3O_12 (GAGG) large single crystals. In particular, we aim to discover the undiscovered ^{160}Gd 2ν2β by searching for the half-life predicted by theory. Currently, we are developing high-purity GAGG crystals and preparing a low-background experimental environment in the Kamioka underground, and long-term data acquisition started in December 2024. In this talk, an overview of the PIKACHU experiment and a status report will be given.
| Takashi Iida (University of Tsukuba) |
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| 16:00 |
Double Gamow–Teller giant resonance in 48Ca studied by (12C, 12Be(0+2)) reaction at 250 MeV/u (16:05-16:35)
Abstract:
The nuclear response of the double Gamow–Teller (DGT) transition in the high excitation energy region is hardly known. Especially, the existence of DGT giant resonance (DGTGR) is expected but it has not yet been experimentally established. The observables of the DGTGR is suggested to have a correlation with the nuclear matrix element of neutrino-less double β decay. We performed an experiment with a double charge exchange reaction of the (12C, 12Be(0+2)) aiming at the observation of the DGTGR. We measured the differential cross section for 48Ca target with the energy resolution of 1.5 MeV and the angular resolution of 0.2º. We observed a forward-peaking structure around 20 MeV, which is a candidate for the DGTGR. In this talk, the outlines of the experiment and the analysis are presented.
| Akane Sakaue (CNS, The University of Tokyo) |
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| 16:30 |
Precision neutrinoless double-beta decay NMEs (16:35-17:05)
Abstract:
Neutrinoless double-beta decay (0νββ) is a nuclear process where two neutrons transform into two protons, emitting only two electrons. Its observation would confirm that neutrinos are Majorana particles, provide evidence of massive neutrinos, and help explain the matter-antimatter asymmetry in the universe. The half-lives depend on the square of the nuclear matrix elements (NMEs), which must be computed since 0νββ remains unobserved. This talk explores NME calculations with next-to-next-to-leading order (N2LO) corrections in the NSM and QRPA frameworks, aiming to reduce uncertainties. We discuss ultrasoft neutrino contributions, significant in light sterile neutrino scenarios, and present novel full N2LO results, previously uncomputed.
| Daniel Castillo Garcia (University of Barcelona) |
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| 17:00 |
| Time | Title | Speaker |
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Session V (09:30-10:30)
Chair:---- (----) |
| 09:30 | Using the atomic nucleus as a probe for BSM physics (09:30-10:30)
Abstract:
As experiments searching for neutrinoless double beta decay are in the planning phase of a next generation with hopes to completely probe the inverted mass hierarchy, the need for reliable nuclear matrix elements is stronger than ever. Since a large discrepancy is found when computing this quantity with different nuclear models, a large unknown still exists on the sensitivity of these experiments to the effective neutrino mass. In this talk I will present how, using ab initio methods relying on systematic expansions, a rigorous statistical uncertainty can be achieved. I will further discuss the new machine learning emulator that I have developed to allow for uncertainty quantification and discuss the future applications of this emulator to other nuclear physics problems.
| Antoine Belley (MIT) |
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| 10:00 |
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| 10:30 | Coffee Break(10:30-10:50) |
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Session VI (10:50-11:50)
Chair:---- (----) |
| 10:50 | Approaching Neutrinoless double beta decay matrix elements via double gamma decay (10:50-11:20)
Abstract:
The yet undiscovered neutrinoless double beta decay (0νββ) has a unique physics potential. It is sensitive to the way of describing neutrinos, helping to establish whether neutrinos are their own antiparticles, and more fundamentally to the symmetries of nature, since its observation constitute a laboratory probe of lepton number violation.
In this talk I will discuss the relation we have found between double gamma decay from the double isobaric analog state (DIAS) of the initial double beta decay nucleus and 0νββ decay within nuclear shell model. Additionally, I will present our latest results of its experimental feasibility, where the main competing channels have been analyzed.
| Beatriz Romeo (University of North Carolina at Chapel Hill) |
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| 11:00 |
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NME for LR symmetric model (11:20-11:50)
Abstract:
LR symmetric model is one of the interesting new physics models with rich phenomenon, and one of which is the neutrinoless double beta decay. Besides the normal neutrino mass mechanism, we have also contributions from the so-called q term of the neutrino propagator which is not suppressed by helicity. Besides the decay to the ground states, these mechanisms can also contribute to the decay to the first excite state. I will discuss the NME calculations for both decay modes and comparison between different methods.
| Dong-Liang Fang (Institute of Modern Physics, China Academy of Sciences) |
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| 11:30 |
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| Break(Refreshments)(11:50-13:30) |
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| 12:00 |
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| 12:30 |
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| 13:00 |
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Session VII (13:30-15:00)
Chair:---- (----) |
| 13:30 | The impact of different NME calculations on neutrino-less double beta experiments (13:30-14:00)
Abstract:
In this talk, I will discuss the neutrino mass dependent nuclear matrix element (NME) of the neutrinoless double beta decay process and derive the limit on the parameter space of the minimal Type-I seesaw model from the current available experimental data as well as the future sensitivities from the next-generation experiments. The extension to B-L symmetric model will also be included.
| Jing-yu Zhu (Institute of Modern Physics, Chinese Academy of Sciences) |
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| 14:00 | Non-nucleonic correlations in DBD NMEs (14:00-14:30)
Abstract:
Non-nucleonic correlations affect much DBD NMEs. Among them the $\Delta$ isobar, which is the quark spin isospin excitation, plays a crucial role for the axial-vector NME of DBD. We report for the first time the effect of the $\Delta$ isobar giant resonsnce on the axial-vector DBD NMEs on the basis of experimental results on GT and SD NMEs in the low-excitation region. They are analysed in the frame work of the QRPA including both the NN and N-$\Delta$ interactions. The $\Delta$ giant resonance is shown to reduce uniformly the axial-vector DBD NME. This effect is incorpolated by using an effective coupling of $g^{eff}_A=0.7 in units of the coupling for a free nucleon.
| Hiroyasu Ejiri (RCNP Osaka Univ.) |
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| 14:30 | Renormalization of the electroweak current within the realistic shell model (14:30-15:00)
Abstract:
The understanding of the renormalization mechanisms of electroweak currents is nowadays a cornerstone of the nuclear structure research. It is motivated by the need of calculating reliable nuclear matrix elements for the neutrinoless double- decay. Our approach to the problem is the realistic nuclear shell model. It provides a consistent framework to derive effective Hamiltonians and decay operators, the only parameter that is involved being the nuclear force one starts from.
In this talk I will outline the recent results obtained namely, the contribution of the 2-body currents to GT operator, calculated within the framework of chiral EFT, and the study of the shape of forbidden beta decays and their sensitivity to the renormalization of the decay operators.
| De Gregorio Giovanni (Università della Campania) |
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| 15:00 | Coffee Break(15:00-15:20) |
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Session VIII (15:20-17:05)
Chair:---- (----) |
| 15:20 | Shell-model Study of Zr isotopes and the neutrinoless-double-beta-decay nuclear matrix element of 96Zr (15:20-15:35)
Abstract:
We performed the systematic shell-model studies on Zr isotopes and their neighbouring nuclei utlizing
the Quasi-particle vacua shell model QVSM.
As the neutron number increases, the Zr isotopes show the phase transitions from spherical
to deformed shapes near 100Zr.
The spherical and deformed states coexist in the low-excitation-energy region near the transitional point
such as 96Zr, which is one of the double-beta-decay nuclei.
We demonstrate that the QVSM result well reproduces the shape transition and transition probabilities
including those between two coexisting bands.
The neutrinoless-double-beta-decay nuclear matrix element of 96Zr is evaluated based on this study.
| Noritaka Shimizu (University of Tsukuba) |
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| 15:30 |
Double-beta decay nuclear matrix elements: how to constrain them? (15:35-16:05)
Abstract:
In my talk I will discuss both theoretical progress and ideas on using experimental data (on other observables) in order to obtain reliable nuclear matrix elements for neutrinoless double-beta decay before it is hopefully measured by next-generation experiments.
| Javier Menendez (University of Barcelona) |
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| 16:00 |
Neutrinoless double-beta decay within relativistic configuration-interaction density functional theory (16:05-16:35)
abstract/pdf | Ya-kun Wang (Peking Univ.)
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| 16:30 |
Unlocking the Nuclear Matrix Elements of Neutrinoless Double-Beta Decay: A Novel Experimental Approach (16:35-16:50)
Abstract:
The detection of neutrinoless double-beta (0\nu\beta\beta) decay is a key challenge in particle and nuclear physics, with the potential to confirm that neutrinos are their own antiparticles, uncover matter-antimatter asymmetry, and provide insights into absolute neutrino mass. Despite extensive experimental efforts, 0\nu\beta\beta decay remains elusive, with significant uncertainty in the Nuclear Matrix Elements (NMEs) needed to interpret its signals. This presentation explores a novel approach using double-magnetic dipole (\gamma\gamma-M1M1) decays from double isobaric analog states (DIAS) to constrain NMEs, offering new insights into 0\nu\beta\beta decay mechanisms and fundamental physics.
| Jose Javier Valiente Dobon (CSIC-IFIC) |
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Perturbation of transition operator of double-beta decay (16:50-17:05)
Abstract:
We calculate the nuclear matrix elements of the neutrinoless and the two-neutrino double-beta decays for 136Xe to 136Ba with the higher-order corrections for the transition operators in terms of perturbation interaction. This is a study of the effects that cannot included in the initial and the final nuclear wave functions. The new terms are derived by an extension of the usual leading-order calculation using the perturbation theory. We use the lowest-order corrections of the vertex correction and the two-body current. It turned out that the absolute values of these correction terms are comparable with that of the leading term. The effective axial-vector current coupling for the two-neutrino double-beta decay with the new nuclear matrix element is obtained.
| Jun Terasaki (Czech Technical University in Prague) |
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| 17:00 |
