How can we test the neutrino mass seesaw mechanism experimentally?

The seesaw mechanism for the small neutrino mass has been a popular paradigm, yet it has been believed that there is no way to test it experimentally. We present a conceivable outcome from future experiments that would convince us of the seesaw mechanism. It would involve data from the CERN Large Hadron Collider, International Linear Collider, cosmology, underground, and low-energy flavor experiments to establish the case.     

Realistic neutrino masses from multi-brane extensions of the Randall-Sundrum model?

Scenarios based on the existence of large or warped (Randall-Sundrum model) extra dimensions have been proposed for addressing the long standing puzzle of the gauge hierarchy problem. Within the contexts of both those scenarios, a novel and original type of mechanism generating small (Dirac) neutrino masses, which relies on the presence of additional right-handed neutrinos that propagate in the bulk, has arisen. The main objective of the present study is to determine whether this geometrical mechanism can produce reasonable neutrino masses also in the interesting multi-brane extensions of the Randall-Sundrum model. We demonstrate that, in some multi-brane extensions, neutrino masses in agreement with all relevant experimental bounds can indeed be generated but at the price of a constraint (stronger than the existing ones) on the bulk geometry, and that the other multi-brane models even conflict with those experimental bounds.Received: 16 December 2004, Published online: 9 March 2005PACS: 14.60.Pq, 14.60.St, 11.10.Kk     

Direct mass measurements of Hg and Au: A new route to the neutrino mass determination?

The study of nuclear electron capture (EC) offers an exciting alternative for the determination of the neutrino mass. Whereas only tritium and ¹⁸⁷Re can be used in the case of β-decay experiments involving the anti-neutrino, a potentially large number of EC-nuclides can be used in experiments involving the monochromatic neutrino. This alternative to β  -decay experiments requires an accurate measurement of QEC$Q_{\mathit{EC}}$-values of appropriate candidates. In the present work we initiate a search for such a candidate and determined the QEC$Q_{\mathit{EC}}$-value of the electron capture in ¹⁹⁴Hg by direct mass measurements of ¹⁹⁴Hg and ¹⁹⁴Au. The new QEC$Q_{\mathit{EC}}$-value of 29(4) keV determined by the ISOLTRAP Penning-trap mass spectrometer at ISOLDE/CERN forbids the K-capture for ¹⁹⁴Hg. However, it allows a determination of the neutrino mass by a combination of a micro-calorimetric measurement of the de-excitation spectrum from L-capture in ¹⁹⁴Hg and a comparable QEC$Q_{\mathit{EC}}$-value remeasurement by high-precision Penning trap mass spectrometry.     

Is the “missing mass” really missing?

We have no experimental evidence for the validity of the inverse square law for gravitation at distances significantly larger than the diameter of the solar system. This raises the very real possibility that the missing mass (dark matter) may not exist. Instead, the inverse square law may be breaking down at distances of the order of tens of kiloparsecs. I discuss this possibility within the framework of Scalar-Vector-Tensor (SVT) theories of gravity. It appears to be relatively easy to account for up to approximately 10% of the galactic halo dark matter via SVT theories of gravity. With some fine-tuning of parameters, it is conceivable that all of the dark matter can be accounted for in this way.This essay received an honorable mention from the Gravity Research Foundation for the year 1987.Supported by the U.S. Department of Energy under grant #DE-FG03-84ER-40168.     

Geometry of the effective Majorana neutrino mass in the 0νββ decay

The neutrinoless double-beta (0νββ) decay is a unique process used to identify the Majorana nature of massive neutrinos, and its rate depends on the size of the effective Majorana neutrino mass <m>_ee. We put forward a novel ‘coupling-rod’ diagram to describe <m>_ee in the complex plane, by which the effects of the neutrino mass ordering and CP-violating phases on <m>_ee are intuitively understood. We show that this geometric language allows us to easily obtain the maximum and minimum of |<m>_ee|. It remains usable even if there is a kind of new physics contributing to <m>_ee, and it can also be extended to describe the effective Majorana masses <m>_eμ, <m>_eτ, <m>_μμ, <m>_μτ and <m>_ττ which may appear in some other lepton-number violating processes.     

Can sterile neutrinos be ruled out as warm dark matter candidates?

We present constraints on the mass of warm dark matter (WDM) particles from a combined analysis of the matter power spectrum inferred from the Sloan Digital Sky Survey Lyman-alpha flux power spectrum at 2.2相似文献   

Is the unitarity of the quark-mixing CKM matrix violated in neutron beta-decay?

We report on a new measurement of neutron beta-decay asymmetry. From the result A(0) = -0.1189(7), we derive the ratio of the axial vector to the vector coupling constant lambda = g(A)/g(V) = -1.2739(19). When included in the world average for the neutron lifetime tau = 885.7(7) s, this gives the first element of the Cabibbo-Kobayashi-Maskawa (CKM) matrix V(ud). With this value and the Particle Data Group values for V(us) and V(ub), we find a deviation from the unitarity condition for the first row of the CKM matrix of Delta = 0.0083(28), which is 3.0 times the stated error.     

How random are matrix elements of the nuclear shell model Hamiltonian?

In this paper we study the general behavior of matrix elements of the nuclear shell model Hamiltonian.We find that nonzero off-diagonal elements exhibit a regular pattern,if one sorts the diagonal matrix elements from smaller to larger values.The correlation between eigenvalues and diagonal matrix elements for the shell model Hamiltonian is more remarkable than that for random matrices with the same distribution unless the dimension is small.     

Is the standard model saved asymptotically by conformal symmetry?

Journal of Experimental and Theoretical Physics - It is pointed out that the top-quark and Higgs masses and the Higgs VEV with great accuracy satisfy the relations 4m 2 = 2m 2 = v 2, which are very...     

How can the neutrino interact with the electromagnetic field?

Maxwell electrodynamics in the fixed Minkowski space-time background can be described in an equivalent way in a curved Riemannian geometry that depends on the electromagnetic field and that we call the electromagnetic metric(e-metric for short). After showing such geometric equivalence we investigate the possibility that new processes dependent on the e-metric are allowed. In particular, for very high values of the field, a direct coupling of uncharged particles to the electromagnetic field may appear.     

Is it possible to estimate the Higgs mass from the CMB power spectrum?

General Relativity and Standard Model are considered as a theory of dynamical scale symmetry with definite initial data compatible with the accepted Higgs mechanism. In this theory the Early Universe behaves like a factory of electroweak bosons and Higgs scalars, and it gives a possibility to identify three peaks in the Cosmic Microwave Background power spectrum with the contributions of photonic decays and annihilation processes of primordial Higgs, W and Z bosons in agreement with the QED coupling constant, Weinberg’s angle, and Higgs’ particle mass of about 118 GeV. The text was submitted by the authors in English.