Challenges in Double Beta Decay

Table 15

List of sensitivity parameters for some of the most advanced 𝛽𝛽(0𝜈) projects. 𝐵_iso is the background per tonne of isotope mass in units of counts/(keV⋅tonne⋅yr). The column labeled “Perf.” reports the performance index (11) in units of 10⁻³ counts/(𝑛_𝛽𝛽⋅yr). The column labeled “Sc.” reports the scale of the experiment (11) in units of 𝑛_𝛽𝛽 (number of effective moles of isotope × yr). The status of the experiment, R (running), C (construction), and D (development), is shown in the column labelled “Status.” Sensitivities (in unit 10²⁵ yr) are evaluated according to (9) and (10) as appropriate, assuming 5 years of running time. |⟨𝑚_𝜈⟩| values (meV) are calculated using NME and phase space factors from [38, 44], respectively. Asterisks label ZB conditions; in the case of GERDA II we report two different sensitivities according to the two hypotheses discussed in Section 10.

	Isotope	𝐵iso	FWHM (keV)	Perf.	Sc.	Status	𝐹^0𝜈68%C.L. (5 yr)	|⟨𝑚𝜈⟩|
CUORE-0 [106]	130Te	266	5.6	0.2	66	R	1.5	224
CUORE [101, 162, 163]	130Te	36	5	27	1390	C	21	60
GERDA I [126]	76Ge	21	4.8	9.2	119	R	9.4	165
GERDA II [120, 164, 165]	76Ge	20/1.1	3.2	5.7/0.3	328	C	22/60*	107/65*
LUCIFER [116, 117]	82Se	1.9	13	2.7	86	D	16*	76*
MJD [127–129, 166]	76Ge	0.9	4	0.4	238	C	44*	77*
SNO+ [138]	130Te	0.9	240	27	1253	D	20	62
EXO [160]	136Xe	1.9	96	30	482	R	12	97
SND [91–93]	82Se	0.6	120	18	23	D	3.3	166
SuperNEMO [91–93]	82Se	0.6	130	20	366	D	13	85
KamLAND-Zen [132, 134]	136Xe	7.4	243	243	1320	R	6.9	127
NEXT [87, 167]	136Xe	0.8	13	5.4	165	D	16	82