Expected sensitivity to 128Te neutrinoless double beta decay with the CUORE TeO2 cryogenic bolometers

Abstract The CUORE experiment is a ton-scale array of $$\hbox {TeO}_2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mtext>TeO</mml:mtext> <mml:mn>2</mml:mn> </mml:msub> </mml:math> cryogenic bolometers located at the underground Laboratori Nazionali del Gran Sasso of Istituto Nazionale di Fisica Nucleare (INFN), in Italy. The CUORE detector consists of 988 crystals operated as source and detector at a base temperature of $$\sim 10$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>∼</mml:mo> <mml:mn>10</mml:mn> </mml:mrow> </mml:math> mK. Such cryogenic temperature is reached and maintained by means of a custom built cryogen-free dilution cryostat, designed with the aim of minimizing the vibrational noise and the environmental radioactivity. The primary goal of CUORE is the search for neutrinoless double beta decay of $$^{130}\hbox {Te}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mrow/> <mml:mn>130</mml:mn> </mml:msup> <mml:mtext>Te</mml:mtext> </mml:mrow> </mml:math> , but thanks to its large target mass and ultra-low background it is suitable for the study of other rare processes as well, such as the neutrinoless double beta decay of $$^{128}\hbox {Te}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mrow/> <mml:mn>128</mml:mn> </mml:msup> <mml:mtext>Te</mml:mtext> </mml:mrow> </mml:math> . This tellurium isotope is an attractive candidate for the search of this process, due to its high natural isotopic abundance of 31.75%. The transition energy at (866.7 ± 0.7) keV lies in a highly populated region of the energy spectrum, dominated by the contribution of the two-neutrino double beta decay of $$^{130}\hbox {Te}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msup> <mml:mrow/> <mml:mn>130</mml:mn> </mml:msup> <mml:mtext>Te</mml:mtext> </mml:mrow> </mml:math> . As the first ton-scale infrastructure operating cryogenic $$\hbox {TeO}_2$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mtext>TeO</mml:mtext> <mml:mn>2</mml:mn> </mml:msub> </mml:math> bolometers in stable conditions, CUORE is able to achieve a factor $$&gt;10$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>&gt;</mml:mo> <mml:mn>10</mml:mn> </mml:mrow> </mml:math> higher sensitivity to the neutrinoless double beta decay of this isotope with respect to past direct experiments.