Double Beta Decay(A,Z+1)Even-even nucleus2vβ(A,Z)β(A,Z+2)2vββ:T1/2≥1018y(A,Z)1935M.Goeppert-Mayer(A,Z+2)(A,Z) →(A,Z+2) + 2e + 2 v
e – e – (A,Z) (A,Z+2) W W (A,Z) → (A,Z+2) + 2e – + 2ne 2nbb: T1/2 ≥ 1018y (A,Z) (A,Z+2) (A,Z+1) bb Even-even nucleus 2nbb 1935 Double Beta Decay M. Goeppert-Mayer
Dirac or Majorana Neutrinos?Ovβ19370vββ:T1/2≥1025y(A,Z)WVeSuneiW2V帘0.8(A,Z+2)DLE(A,Z) → (A,Z+2) + 2e0.2Off2000500100015002500Energy (kev)Majorana →neutrino=anti-neutrinoLepton Number violation!
Dirac or Majorana Neutrinos? 0nbb n e e – e n e – (A,Z) (A,Z+2) W W (A,Z) → (A,Z+2) + 2e – 0nbb: T1/2 ≥ 1025y 1937 Majorana → neutrino = anti-neutrino Lepton Number violation !
Measuring Neutrino Masses101)DirectMeasurementconst.offset~m2(ve)8tritium decaysE0=18.6keV6[n'e]3my=0eV4Z?<mZIm~2*10-132i=1mv=1eVo2)EffectiveMajoranaMass-20-3-13E-E,[eV]ZIUei<mββm,8ii=-1&;- CP phase for neutrinos3)Precise Cosmological Measurement3Zmi<mS> =i=1
Measuring Neutrino Masses = 3 1 2 2 | | i Uei mi = 3 1 2 | | i Uei mi i 1) Direct Measurement tritium decays E0 = 18.6 keV <mb> = 2) Effective Majorana Mass <mbb> = 3) Precise Cosmological Measurement <mS> = = 3 i 1 mi i – CP phase for neutrinos
DoubleBeta Decay CandidatesNormal beta-decayisenergeticallyforbidden,whiledoublebeta-decayfrom(A,Z)→(A,Z+2)is energeticallyallowed:(A=even,Z=even)A, Z+1A, Z+30tA, Zβ0tA, Z+2Somecandidates:48Ca, 70Zn, 76Ge, 80Se, 86Kr, 96Zr, 100Mo, 116Cd, 130Te, 136Xe, 150Nd
Double Beta Decay Candidates Normal beta-decay is energetically forbidden, while double beta-decay from (A,Z) → (A, Z+2) is energetically allowed: A, Z A, Z+1 A, Z+2 0 + A, Z+3 0 + bb (A=even, Z=even) 48Ca, 70Zn, 76Ge, 80Se, 86Kr, 96Zr, 100Mo, 116Cd, 130Te, 136Xe, 150Nd Some candidates:
CandidateforDouble beta DecaysQ(MeV)Abund.(%)48Ca48Ti4.2710.18776Ge →76Se7.82.04082Se82Kr9.22.99596Zr-→96Mo2.83.350100Mo-100Ru9.63.034110Pd→110Cd11.82.013116Cd-116Sn7.52.802124Sn→124Te2.2285.64130Te→130Xe2.52834.5136Xe→136Ba8.92.479150Nd-150Sm5.63.367
48Ca→48Ti 4.271 0.187 76Ge →76Se 2.040 7.8 82Se→82Kr 2.995 9.2 96Zr→96Mo 3.350 2.8 100Mo→100Ru 3.034 9.6 110Pd→110Cd 2.013 11.8 116Cd→116Sn 2.802 7.5 124Sn→124Te 2.228 5.64 130Te→130Xe 2.528 34.5 136Xe→136Ba 2.479 8.9 150Nd→150Sm 3.367 5.6 Candidate for Double beta Decays Q (MeV) Abund.(%)