A search for decays of heavy neutrinos in the mass range 0.5–2.8 GeV

A search for decays of heavy neutrinos was conducted by the CHARM Collaboration in a prompt neutrino beam produced by dumping 400 GeV protons in a Cu target, and in the CERN wide-band neutrino beam produced by 400 GeV primary protons. No candidate event was found. In the beam-dump experiment heavy neutrinos have been assumed to be produced by mixing in charmed D meson decays. Neutrinos decaying into e⁺e⁻v_e, μ⁺e⁻v_μ, and μ⁺μ⁻v_μ were searched for. Limits of |U_ei|², |U_μi|² < 10⁻⁷ were obtained for neutrino masses around 1.5 GeV. In the wide-band experiment heavy neutrinos were assumed to be produced by neutral-current neutrino interactions in the CHARM calorimeter. Here a search was made for neutrinos decaying into a μ and hadrons. This experiment is sensitive to decays of neutrinos with mass in the range 0.5–2.8 GeV with limits of |U_μi|² < 3 × 10⁻⁴ for masses around 2.5 GeV. These measurements extend our previous results in the mass range 10–400 MeV.     

Why is GeV physics relevant in the age of the LHC?

The contribution that Jefferson Lab has made, with its 6 GeV electron beam, and will make, with its 12 GeV upgrade, to our understanding of the way the fundamental interactions work, particularly strong coupling QCD, is outlined. This physics at the GeV scale is essential even in TeV collisions.     

On the relation of the Methagalaxy mass to the gravitation constant. 1. from Einstein’s theory to the Einstein–Cartan theory

The notion of the dimensionless gravitational charge defined through the Planck mass and the fundamental constants specifying this mass itself is introduced. The Big Bang is related to the unified physical interaction decay and the drop of Newton’s gravitational constant by 40.67 orders of magnitude in comparison with the electromagnetic constant taken as unity. This causes an increase in theMetagalaxy curvature radius by the same value and a decrease in the average density of space–time curvature sources by 122 orders of magnitude: from the maximum allowable Planck density to the observed critical density. The microphysics appears naturally related to cosmology.     

On the mass of the ss^- member of the 1^3D1 meson nonet

In the framework of Regge phenomenology and meson meson mixing, this paper estimates the mass of isoscalar state （ss^-） of the 1^3D1 meson nonet, and the results given by two different approaches are 1735.51 ± 59MeV and 1730.29 ±46.SMeV.     

Determination of an upper limit for the mass of the τ-neutrino at LEP

An upper limit for the mass is determined through the kinematic reconstruction of the decay5 ^± in the OPAL detector at LEP. The limit is obtained using a new method based on the comparison of the two-dimensional distribution of energy and invariant mass of the five-pion system with expectations from different neutrino mass hypotheses. From a sample of five events surviving the selection criteria we obtain an upper limit of 74 MeV at 95% confidence level. It is the first measurement at LEP energies, where the larger average multiplicity of events makes the suppression of this background more robust compared to lower energies.     

Probing the mass degeneracy of particles with different spins

The spin is an important property of a particle. Although it is unlikely, there is still a possibility that two particles with di erent spins share similar masses. In this paper, we propose a method to probe this kind of mass degeneracy of particles with di erent spins. We use the cascade decay B⁺→X(3872)K⁺, X(3872)→D⁺D^- to illustrate our method. It can be seen that the possible mass degeneracy of X(3872) can lead to interesting behavior in the corresponding cascade decay.     

Infrared magnetooptic — A tool for the determination of the effective mass

The analysis of the magnetooptical effects of heavily doped materials at the plasma edge yields the concentration dependence of the effective cyclotron mass. Therefore these experiments support the general diskussion about the nonparabolicity of a band, the position of the Fermi level at high degenerated semiconductors and the determination of the dispersion function. Experimental results of the magnetooptical determinedm _c ^* (N) function are compared with coresponding band structure calculations. A matrix calculation model, which describes the symmetrical magnetooptical transmission effects as well as the asymmetrical magnetooptical reflection effects of arbitrary successions of coherent films and incoherent substrates consitently, is used to determine free carrier density profilesN (z) of inhomogeneously doped semiconductors non-destructively. This application of the matrix formalism requires the knowledge of them ^* (N)-function. The influence of the effective cyclotron mass on thedifferential magnetooptical interference structures caused by buried density profiles is discussed.     

Determination of the Avogadro constant – A contribution to the new definition of the mass unit kilogram

An improved attempt of several national metrology institutes to replace the present definition of the kilogram with the mass of a certain number of ¹²C atoms is described. This requires the determination of the Avogadro constant, N _A, via the silicon route with a relative uncertainty better than 2 ⋅ 10^-8. Previously, the limiting factor is the measurement of the average molar mass. Consequently, a world-wide collaboration has been set up, to produce, approximately, 5 kg of ²⁸Si single-crystal with an enrichment factor greater than 99.985% to be used for an improved determination of N _A. The first successful tests of all technological steps (enrichment of SiF₄, purification and synthesis of silane, deposition of polycrystalline ²⁸Si, single crystal growth) for the production of high-purity ²⁸Si are described.     

The Lemaître model and the generalisation of the cosmic mass

We consider the spherically symmetric metric with a comoving perfect fluid and non-zero pressure—the Lemaître metric—and present it in the form of a calculational algorithm. We use it to review the definition of mass, and to look at the apparent horizon relations on the observer’s past null cone. We show that the introduction of pressure makes it difficult to separate the mass from other physical parameters in an invariant way. Under the usual mass definition, the apparent horizon relation, that relates the diameter distance to the cosmic mass, remains the same as in the Lemaître–Tolman case.     

The conservation of energy–momentum and the mass for the graviton

In this work we give special attention to the bimetric theory of gravitation with massive gravitons proposed by Visser in 1998. In his theory, a prior background metric is necessary to take in account the massive term. Although in the great part of the astrophysical studies the Minkowski metric is the best choice to the background metric, it is not possible to consider this metric in cosmology. In order to keep the Minkowski metric as background in this case, we suggest an interpretation of the energy–momentum conservation in Visser’s theory, which is in accordance with the equivalence principle and recovers naturally the special relativity in the absence of gravitational sources. Although we do not present a general proof of our hypothesis we show its validity in the simple case of a plane and dust-dominated universe, in which the “massive term” appears like an extra contribution for the energy density.     

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.     

The mass of the isodoublet of the 2^1S0 meson nonet revisited

In the qq quark model, the states π（1300）, η（1295） and η（1475） are assigned as the 2^1S0 meson nonet. The mass of the isodoublet remains interesting and needs further confirmation in experiments. This paper employs the phenomenological trajectory on the （N, M^2）-plot and meson meson mixing methods to calculate the mass of this state, the calculated results are 1341 MeV and 1311.58 ± 59 MeV respectively. These predictions can be compared with experiments in the future.[第一段]     

On the measurement of ¹⁵N-{¹H} nuclear Overhauser effects. 2. Effects of the saturation scheme and water signal suppression

Measurement of steady-state (15)N-{(1)H} nuclear Overhauser effects forms a cornerstone of most methods to determine protein backbone dynamics from spin-relaxation data, since it is the most reliable probe of very fast motions on the ps-ns timescale. We have, in two previous publications (J. Magn. Reson. 192 (2008) 302-313; J. Am. Chem. Soc. 131 (2009) 6048-6049) reevaluated spin-dynamics during steady-state (or "saturated") and reference experiments, both of which are required to determine the NOE ratio. Here we assess the performance of several windowed and windowless sequences to achieve effective saturation of protons in steady-state experiments. We also evaluate the influence of the residual water signal due to radiation damping on the NOE ratio. We suggest a recipe that allows one to determine steady-state (15)N-{(1)H} NOE's without artifacts and with the highest possible accuracy.     

The anomalous shift of the weak boson mass and the quintessence electroweak axion

One of the simplest ways to account for the observed W-boson mass shift is to introduce the SU(2)_L triplet Higgs boson with zero hypercharge, whose vacuum expectation value is about 3 Ge V. If the triplet is heavy enough at O(1) Te V, it essentially contributes only to T parameter without any conflict with the observation. The presence of a complex triplet Higgs boson raises the SU(2)_L gauge coupling constant to α₂(MPL) ■ 1/44 at the Planck scale. Thanks to this ...     

Spin-averaged mass formulas and the mass spectrum of low lying Δ-resonances in harmonic-oscillator-like quark models

By spin-averaging the masses of one species of particle over a sufficient number of multiplets we argue that the resulting spin-averaged mass is insensitive to mass operators which are not spin-scalar. This approach may be applied to averaging over quantum numbers other than spin. We discuss the assumptions necessary to restricting the average to only relatively few multiplets and show how mass formulas between averaged masses may be constructed. This approach reduces the number of parameters and predicts patterns of splittings which should be common to many analyses. We apply our results to the low lying Δ-resonances in harmonic-oscillator-like models and examine the comparison of theory with experiment for four different assumptions about which states should be included in particular averages. Using data from experiment we find that the prediction for the spin-averaged mass of the Δ-resonances from (56,1 ₃ ^? ) is, on average, 150 MeV higher than the spin-averaged mass of the experimental Δ states plausibly assigned to the (56,1 ₃ ^? ). This result is insensitive to which of the assumptions is made. Some suggestions are made about rectifying this discrepancy.