Abstract

Since 2010, the Gerda experiment at Laboratori Nazionali del Gran Sasso (LNGS) operates searching for neutrinoless double beta decay ( 0 ν β β ) of 76 Ge to the ground and excited states of 76 Se. 0 ν β β is an ultra-rare process whose detection would directly establish the Majorana nature of the neutrino and provide a direct measurement of its mass. Since the apparatus upgrade in 2013–2015, the collaboration released the third update of the achieved results at the Neutrino 2018 Conference. The hardware upgrade and the fine tuning of the powerful analysis tools to reconstruct the event energy and to discriminate the background allowed the achievement of the energy resolution of 3 keV and 3.6 keV for Broad Energy Germanium (BEGe) and Coaxial Germanium (Coax) detectors, respectively, and an unprecedented low background index of 0.6

Highlights

  • The last two decades of particle experimental physics have showed that neutrinos, while propagating, oscillate one into the other: this is because they have a finite mass, and the three neutrino flavor eigenstates do not coincide with the three mass eigenstates

  • Four data sets in Phase I: (i) GOLDEN-C OAX: all the coaxial data but two runs after the insertion of BEG E pilot string in July 2012; (ii) SILVER-C OAX: the coaxial data from the two runs just after the BEG E string deployment; (iii) BEG E: all the BEG E data, (iv) Extra: the C OAX data collected after the Phase I unblinding, and before the setup upgrade to Phase II

  • M2e where < mee > is the effective Majorana Neutrino Mass, me is the electron mass, F0ν ( Q, Z ) is the transition phase space [22], M0ν is the Nuclear Matrix Element of the 76 Ge→76 Se transition: Nuclear Matrix Elements (NME) calculations provide values ranging within a factor of 2–4 depending on adopted nuclear models [23]: a range of values for M0ν leads to a range for the neutrino mass limit

Read more

Summary

Introduction

The last two decades of particle experimental physics have showed that neutrinos, while propagating, oscillate one into the other: this is because they have a finite mass, and the three neutrino flavor eigenstates do not coincide with the three mass eigenstates. The parameters driving the oscillations, i.e., the three neutrino mass differences (∆m2 ) and the three oscillation mixing angles, have been measured with improving accuracy [1] not at the 1% level as in the quark sector: the Majorana CP-violating phases instead are still unknown, as well as the octant of θ23. These experiments cannot establish if the neutrino is a Dirac or Majorana particle and measure its absolute mass, and so far have not provided information on the eigenstates mass order (hierarchy). The G ERDA sensitivity on the 0νββ half-life

The Setup
Data Treatment
Background
Discussion and Results
Conclusions
Full Text
Paper version not known

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.