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SUMMARY:Nuclear Deformations Relevant for Neutrinoless Double-Beta Decay
DTSTART:20260305T153000Z
DTEND:20260305T173000Z
DTSTAMP:20260511T012400Z
UID:indico-event-51067@agenda.infn.it
CONTACT:alain.goasduff@lnl.infn.it
DESCRIPTION:Speakers: Marco Siciliano (Argonne National Laboratory)\n\nNeu
 trinoless double-beta decay (0νββ) is a speculated and extremely rare p
 rocess in which a nucleus undergoes two simultaneous beta decays without e
 mitting neutrinos. Observation of this decay would demonstrate that neutri
 nos are Majorana particles and provide direct evidence of lepton number vi
 olation – an essential ingredient for explaining the matter-antimatter 
 asymmetry in the universe. As such\, 0νββ decay is a central focus of m
 odern nuclear and particle physics\, with numerous experimental efforts wo
 rldwide dedicated to its detection. Since the interpretation of any future
  signal depends critically on the Nuclear Matrix Element (NME)\, understan
 ding the nuclear structure of the involved decay partners is essential.\nI
 n this context\, recent theoretical studies have highlighted the strong im
 pact of the nuclear deformation of the decay partners on the NME magnitude
 . In particular\, shape differences between the initial and final nuclei c
 an introduce significant suppression of the decay probability. However\, t
 heoretical models currently disagree on the structure of many 0νββ cand
 idates and predict divergent NME values. Therefore\, new experimental cons
 traints on nuclear structures and shapes of the decay partners are crucial
  to validate and guide theoretical efforts.\nIn this contribution\, I will
  present recent Coulomb-excitation measurements aimed at determining the g
 round-state deformation of 116Sn and 130Te\, two key nuclei for double-bet
 a decay studies. The 130Te experiment was performed at ATLAS (USA) using t
 he GRETINA+CHICO2 setup and complemented by an independent measurement wit
 h AGATA+SPIDER at INFN-LNL (Italy). The 116Sn campaign\, instead\, was car
 ried out at INFN-LNL with GALILEO+SPIDER and recently followed by a second
  experiment at ATLAS employing the GRETINA+CHICO-X setup to extend the lev
 el scheme toward higher-lying states.\nThe analysis of the 116Sn data has 
 revealed that\, in addition to a near-spherical ground state\, multiple ex
 cited 0+ states with distinct deformations coexist within the same nucleu
 s—an indication ⁺ of multiple-shape coexistence. These findings provid
 e important input for structure models used in NME calculations.\nPrelimin
 ary data from additional studies on other 0νββ candidates\, including 8
 2Se and 116Cd\, will also be briefly discussed.\nThese results highlight t
 he role of precision Coulomb-excitation studies in mapping shape evolution
  across 0νββ decay partners and in constraining the nuclear-structure i
 ngredients necessary for reliable matrix element predictions.\nThis resear
 ch was partially supported by the European Union’s Seventh Framework Pro
 gramme for Research and Technological Development (grant no. 262010)\, and
  by the U.S. Department of Energy\, Office of Science\, Office of Nuclear 
 Physics\, under contract number DE-AC02-06CH11357. This study used resourc
 es of ANL’s ATLAS facility\, which is a DOE Office of Science User Facil
 ity.\n\nhttps://agenda.infn.it/event/51067/
LOCATION:C. Villi meeting room
URL:https://agenda.infn.it/event/51067/
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