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Register a new userDivalent lanthanoid ions in crystals for neutrino mass spectroscopy
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Electron spin flip in atoms or ions can cause neutrino pair emission, which provides a method to explore still unknown important neutrino properties by measuring spectrum of emitted photon in association, when electroweak rates are amplified by a phase coherence among participating atoms. Two important remaining neutrino issues to be determined are the absolute neutrino mass (or the smallest neutrino mass in the three-flavor scheme) and the nature of neutrino masses, either of Dirac type or of Majorana type. Use of Raman scattered photon was recently proposed as a promising tool for this purpose. In the present work we continue along this line to further identify promising ion targets in crystals, calculate neutrino pair emission rates, and study how to extract neutrino properties from Raman scattered photon angular distribution. Divalent lanthanoid ions in crystals, in particular Sm$^{2+}$, are the most promising, due to (1) its large number density, (2) sharp optical lines, (3) a variety of available ionic levels. Rejection of amplified quantum electrodynamic backgrounds is made possible to controllable levels by choosing a range of Raman trigger direction, when Sm$^{2+}$ sites are at O$_h$ inversion center of host crystals such as SrF$_2$.
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We propose neutrino mass spectroscopy using Er$^{3+}$:Cs$_2$NaYF$_6$ or :Y$_2$O$_3$ crystal placed in hollow of a Bragg fiber as a target system. Unknown neutrino parameters and properties such as the lightest neutrino mass, Majorana/Dirac distinction, and CP violating phases can be explored by measuring scattered photons ($gamma$) along the excitation (and fiber) axis by varying Raman trigger ($gamma_0$) directions, in Er$^{3+}$ de-excitation process from $|erangle $ state to $|grangle $ state; $|erangle ,, | erangle + gamma_0 rightarrow | grangle + gamma + u_ibar{ u}_j$, $ u_i,, i = 1, 2,3$ being a mass-resolved neutrino state. Rates and required level of QED background rejection are calculated using measured data of the target system.
A new, indirect detection method of neutrino pairs $ ubar{ u}$ using magnetization generated at triggered radiative emission of neutrino pair (RENP), $ |e rangle rightarrow | g rangle + gamma + u bar{ u} $ (atomic de-transition from state $|e rangle $ to state $|g rangle$ accompanied by a photon $gamma$), is investigated in order to determine unknown neutrino properties; Majorana/Dirac distinction and absolute neutrino masses. Magnetization associated with RENP events has parity violating component intrinsic to weak interaction enforced by crystal field effect in solids, and greatly helps background rejection of quantum electrodynamic (QED) origin even when these backgrounds are amplified. In proposed experiment we prepare a coherently excited body of trivalent lanthanoid ions, Er$^{3+}$ (a best candidate ion so far found), doped in a transparent dielectric crystal. The magnetic moment $mu langle vec{S}cdotvec{k} rangle/k $ arising from generated electron spin $vec{S}$ parallel to trigger photon direction $vec{k}/k$ is parity odd, and is absent in QED processes. The generated magnetic field of order nano gauss or larger is stored in crystals long after pair emission event till spin relaxation time. An improved calculation method of coherent rate and angular distribution of magnetization is developed in order to incorporate finite size effect of crystal target beyond the infinite size limit in previous calculations.
We have studied the absorption spectra of x-ray irradiation-induced Ce2+ and Pr2+ ions in crystals of alkaline-earth fluorides. We have calculated absorption spectra of divalent praseodymium ions in SrF2 crystals doped with Pr2+ for the first time. The calculated spectra agree rather well with the experimental data. In crystals containing induced Ce2+ ions we have found strong electron-phonon coupling. In BaF2, we do not observe bands corresponded to divalent Ce or Pr ions.
Strongly correlated electrostatics of DNA systems has drawn the interest of many groups, especially the condensation and overcharging of DNA by multivalent counterions. By adding counterions of different valencies and shapes, one can enhance or reduce DNA overcharging. In this papers, we focus on the effect of multivalent co-ions, specifically divalent co-ions such as SO$_4^{2-}$. A computational experiment of DNA condensation using Monte$-$Carlo simulation in grand canonical ensemble is carried out where DNA system is in equilibrium with a bulk solution containing a mixture of salt of different valency of co-ions. Compared to system with purely monovalent co-ions, the influence of divalent co-ions shows up in multiple aspects. Divalent co-ions lead to an increase of monovalent salt in the DNA condensate. Because monovalent salts mostly participate in linear screening of electrostatic interactions in the system, more monovalent salt molecules enter the condensate leads to screening out of short-range DNA$-$DNA like charge attraction and weaker DNA condensation free energy. The overcharging of DNA by multivalent counterions is also reduced in the presence of divalent co$-$ions. Strong repulsions between DNA and divalent co-ions and among divalent co-ions themselves leads to a {em depletion} of negative ions near DNA surface as compared to the case without divalent co-ions. At large distance, the DNA$-$DNA repulsive interaction is stronger in the presence of divalent co$-$ions, suggesting that divalent co$-$ions role is not only that of simple stronger linear screening.
We perform a statistical analysis with the prospective results of future experiments on neutrino-less double beta decay, direct searches for neutrino mass (KATRIN) and cosmological observations. Realistic errors are used and the nuclear matrix element uncertainty for neutrino-less double beta decay is also taken into account. Three benchmark scenarios are introduced, corresponding to quasi-degenerate, inverse hierarchical neutrinos, and an intermediate case. We investigate to what extend these scenarios can be reconstructed. Furthermore, we check the compatibility of the scenarios with the claimed evidence of neutrino-less double beta decay.
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