We report the results of an improved determination of the triple correlation $D P cdot(p_{e}times p_{ u})$ that can be used to limit possible time-reversal invariance in the beta decay of polarized neutrons and constrain extensions to the Standard Model. Our result is $D=(-0.96pm 1.89 (stat)pm 1.01 (sys))times 10^{-4}$. The corresponding phase between g_A and g_V is $phi_{AV} = 180.013^circpm0.028^circ$ (68 % confidence level). This result represents the most sensitive measurement of D in beta decay.
We report new results from the search for neutrinoless double-beta decay in $^{130}$Te with the CUORE detector. This search benefits from a four-fold increase in exposure, lower trigger thresholds and analysis improvements relative to our previous results. We observe a background of $(1.38pm0.07)cdot10^{-2}$ counts$/($keV$cdot$kg$cdot$yr$)$ in the $0 ubetabeta$ decay region of interest and, with a total exposure of 372.5 kg$cdot$yr, we attain a median exclusion sensitivity of $1.7cdot10^{25}$ yr. We find no evidence for $0 ubetabeta$ decay and set a $90%$ CI Bayesian lower limit of $3.2cdot10^{25}$ yr on the $^{130}$Te half-life for this process. In the hypothesis that $0 ubetabeta$ decay is mediated by light Majorana neutrinos, this results in an upper limit on the effective Majorana mass of 75-350 meV, depending on the nuclear matrix elements used.
We describe an experiment that has set new limits on the time reversal invariance violating D coefficient in neutron beta-decay. The emiT experiment measured the angular correlation J . p_e x p_p using an octagonal symmetry that optimizes electron-proton coincidence rates. The result is D=[-0.6+/-1.2(stat)+/-0.5(syst)]x10^(-3). This improves constraints on the phase of g_A/g_V and limits contributions to T violation due to leptoquarks. This paper presents details of the experiment, data analysis, and the investigation of systematic effects.
Double-beta processes in $^{184}$Os and $^{192}$Os were searched for over 15851 h at the Gran Sasso National Laboratory (LNGS) of the I.N.F.N. by using a 118 g ultra-pure osmium sample installed on the endcap of a 112 cm$^3$ ultra-low-background broad-energy germanium detector. New limits on double-electron capture and electron capture with positron emission in $^{184}$Os were set at the level of $lim T_{1/2} sim 10^{16}-10^{17}$ yr. In particular the $2 u$2K and $2 u$KL decays of $^{184}$Os to the ground state of $^{184}$W are restricted as $T_{1/2}geq3.0times 10^{16}$ yr and $T_{1/2}geq2.0times 10^{16}$ yr, respectively. A lower limit on the half-life for the double-beta decay of $^{192}$Os to the first excited level of $^{192}$Pt was set as $lim T_{1/2}=2.0times 10^{20}$ yr at 90% C.L.
The CUPID-Mo experiment at the Laboratoire Souterrain de Modane (France) is a demonstrator for CUPID, the next-generation ton-scale cryogenic $0 ubetabeta$ experiment. It consists of a 4.2 kg array of 20 enriched Li$_{2}$$^{100}$MoO$_4$ scintillating bolometers to search for the lepton number violating process of $0 ubetabeta$ decay in $^{100}$Mo. With more than one year of operation (2.16 kg$times$yr of physics data), no event in the region of interest and hence no evidence for $0 ubetabeta$ is observed. We report a new limit on the half-life of $0 ubetabeta$ decay in $^{100}$Mo of $T_{1/2} > 1.5 times 10^{24},$yr at 90 % C.I. The limit corresponds to an effective Majorana neutrino mass $langle m_{betabeta} rangle$ $<$ (0.31--0.54)$,$eV, dependent on the nuclear matrix element in the light Majorana neutrino exchange interpretation.
In the standard model of particle physics, the weak interaction is described by vector and axial-vector couplings only. Non-zero scalar or tensor interactions would imply an additional contribution to the differential decay rate of the neutron, the Fierz interference term. We derive a limit on this hypothetical term from a measurement using spin polarized neutrons. This method is statistically less sensitive than the determination from the spectral shape but features much cleaner systematics. We obtain a limit of b = 0.017(21) at 68.27 C.L., improving the previous best limit from neutron decay by a factor of four.