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SUMMARY:Towards the discovery of 0vbb: first results from LEGEND - William
  Quinn (University College London)
DTSTART:20260224T110000Z
DTEND:20260224T120000Z
UID:TALK241897@talks.cam.ac.uk
CONTACT:Dr Paul Swallow
DESCRIPTION:The sheer abundance of neutrinos all around us makes it hard t
 o believe that we still don’t understand so much about them. It is this 
 allusiveness that makes research into neutrino physics so fascinating\, an
 d within this unknown\, many mysteries about the universe could be unfolde
 d.\n\nA discovery of the hypothetical neutrinoless double beta decay (0vbb
 ) process would have profound implications. It would prove that lepton num
 ber is not a conserved quantity\, prove that neutrinos are Majorana in nat
 ure\, and constrain the mass hierarchy.\n\nThe LEGEND experiment is design
 ed to search for 0vbb using Ge-76 enriched high purity germanium detectors
  that are immersed in liquid argon. LEGEND-200 (L200)\, operating at LNGS 
 in Italy\, builds on the successes in background suppression and analysis 
 techniques from the Majorana Demonstrator and GERDA experiments. L200’s 
 first results are based on 61 kgyr of exposure with an estimated backgroun
 d index of $0.5^{+0.3}_{-0.2}$ cts/(keV ton yr). Data from GERDA and the M
 ajorana Demonstrator were combined with L200’s for a joint analysis\, yi
 elding a 90% CL sensitivity of $2.8x10^{26}$ yr and setting a new lower li
 mit of > $1.9\\times10^{26}$ yr\, for the half-life of 0vbb. Assuming the 
 decay mechanism is mediated by the exchange of a light Majorana neutrino\,
  this half-life limit corresponds to an upper limit on the effective Major
 ana mass of mbb < 75-200 meV. In an attempt to encourage our nuclear theor
 y colleagues\, an additional limit has been set\, with mbb < 320 meV\, uti
 lising the recent developments in uncertainty-quantified nuclear matrix el
 ements.\n\nIn this talk\, I will present L200’s first results published 
 in the recently released paper (https://arxiv.org/pdf/2505.10440) with som
 e added detail about the detector technology. I will also briefly showcase
  the outlook for the next phase of the LEGEND experiment\, L1000\, with so
 me context for the UK double beta decay community.
LOCATION:Ray Dolby Center -- Seminar Room: D2.002 
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