New Constraints on the Axion–Photon Coupling Constant for Solar Axions

Resonance excitation of the ⁸³Kr first nuclear level (E = 9.4 keV) by solar axions formed via the Primakoff mechanism is sought. The γ- and X-ray photons and the conversion and Auger electrons arising from the excited-level relaxation are detected with a gas proportional counter of a low-background detector in the underground Baksan Neutrino Observatory. The following experimental constraint is obtained for the product of the axion–photon coupling constant and the axion mass:|g_Aγ × m_A| ≤ 6.3 × 10 ^-17 In the framework of the hadronic-axion model, this corresponds to a new axion-mass constraint of m_A ≤ 12.7 eV at 95% C.L.     

<Emphasis Type="Italic">O</Emphasis>(1) eV sterile neutrino in <Emphasis Type="Italic">f</Emphasis>(<Emphasis Type="Italic">R</Emphasis>) gravity

We refer [1] to the role of an additional O(1) eV sterile neutrino in modified gravity models. We find parameter constraints in particular f(R) gravity model using following up-to-dated cosmological data: measurements of the cosmic microwave background (CMB) anisotropy, the CMB lensing potential, the baryon acoustic oscillations (BAO), the cluster mass function and the Hubble constant. It was obtained for the sterile neutrino mass 0.47 eV < m _ν,sterile < 1 eV (2σ) assuming that the sterile neutrinos are thermalized and the active neutrinos are massless, not significantly larger than in the standard cosmology model within the same data set: 0.45 eV < m _ν,sterile < 0.92 eV (2σ). But, if the mass of sterile neutrino is fixed and equals ≈ 1.5 eV according to various anomalies in neutrino oscillation experiments, f(R) gravity is much more consistent with observation data than the CDM model.     

Search for resonant absorption of solar axions emitted in an <Emphasis Type="Italic">M</Emphasis>1 transition in <Superscript>57</Superscript>Fe nuclei

The resonant absorption of solar axions by ⁵⁷Fe nuclei, which is accompanied by the excitation of the first excited nuclear level: A + ⁵⁷Fe → ⁵⁷Fe* → ⁵⁷Fe + γ(14.4 keV), is sought. To seek 14.4-keV photons, a Si(Li) detector and an enriched ⁵⁷Fe target are used. The detector and target are placed in a low-background setup equipped with passive and active shieldings. As a result, a new upper limit m _A ≤ 360 eV (at 90% C.L.) has been determined for the axion mass.     

Search for resonant absorption of solar axions by atomic nuclei

Search for resonant absorption of solar axions by ⁵⁷Fe and ¹⁶⁹Tm nuclei, leading to the excitation of the first nuclear level: ⁵⁷Fe: A + ⁵⁷Fe → ⁵⁷Fe* → ⁵⁷Fe + γ and A + ¹⁶⁹Tm → ¹⁶⁹Tm* → ¹⁶⁹Tm + γ, has been performed. To this end, the energy spectra of the Si(Li) detector with ⁵⁷Fe and ¹⁶⁹Tm targets have been measured. The detector and targets were located in a low-background setup equipped with passive and active shields. A new upper limit on the axion mass: m _A ≤ 330 eV (90% confidence level) has been established from the spectrum of ⁵⁷Fe (30 days). Measurements with a ¹⁶⁹Tm target during 8 days gave a new upper limit on the product of the axion-photon coupling constant and the axion mass: g _Aγ (GeV^?1) × m _A (eV) ≤ 2.9 × 10^?4 (90% confidence level).     

Majorana neutrinos, <Emphasis Type="Italic">CP</Emphasis> violation,neutrinoless double beta and tritium beta decays

If the present or upcoming searches for neutrinoless double beta ((ββ)_0ν) decay give a positive result, the Majorana nature of massive neutrinos will be established. From the determination of the value of the (ββ)_0ν-decay effective Majorana mass parameter (|〈m〉|), it would be possible to obtain information on the type of neutrino mass spectrum. Assuming 3-ν mixing and massive Majorana neutrinos, we discuss the information that a measurement of, or an upper bound on, |〈m〉| can provide on the value of the lightest neutrino mass m₁. With additional data on the neutrino masses obtained in ³H β-decay experiments, it might be possible to establish whether the CP symmetry is violated in the lepton sector. This would require very high precision measurements. If CP invariance holds, the allowed patterns of the relative CP parities of the massive Majorana neutrinos would be determined.     

Single-spin asymmetry of in clusive γ produ ction in $$p_ \uparrow p$$ intera ctions at 200 GeV/ c

From the data of Fermilab polarization experiment E704, the analyzing power A _N ^γ of inclusively produced photons was extracted. It is small, of the order of 2–4%. The analyzing power of “leading” photons (the fastest in π⁰ → γγ decay) is a factor of 2 higher than A _N ^γ assuming a definite model for x_F dependence of A _N ^γ . A Monte Carlo simulation is performed in order to see effects at higher statistics than in the E704 experiment. This simulation showed that the process of inclusive photons may be used as a basis for future polarimetry at polarized colliders. The example of one local photon polarimeter at RHIC is discussed.     

Rare kaon decay $$K^ + \to \pi ^ + \nu \bar \nu $$ in S U(3)C ⊗ S U(3)L ⊗ U(1)N models

The rare kaon decay \(K^ + \to \pi ^ + \nu \bar \nu \) is considered in the framework of models based on the SU(3) _C ? SU(3) _L ? U(1) _N (3-3-1) gauge group. In the 3-3-1 model with right-handed neutrinos, the lower bound of the Z’ mass is derived at 3 TeV, and that in the minimal version, at 1.7 TeV.     

Formation of primary particles in stopped pion absorption reactions

The results from analyzing the yields of protons (p), deuterons (d), and tritons (t) formed in the absorption of stopped π^– mesons by intranuclear clusters are presented. The contributions from cluster absorption to the production of hydrogen isotopes in stopped pion absorption reactions are determined. Phenomenological formulas are proposed for describing the mass number (A) dependences of the yields of the primary protons with ～15% precision in the mass number range of 6 < A < 209 (and of the primary deuterons and tritons in the mass number range of 59 < A < 209). Evidence is observed of the constancy of the ratio between the elemental absorption widths for the absorption of pions by pp and pn pairs over the investigated range of mass numbers.     

Cluster decay of <Superscript>112−122</Superscript>Ba isotopes from ground state and as an excited compound system

The decay properties of various even–even isotopes of barium in the range 112 ≤A ≤ 122 is studied by modifying the Coulomb and proximity potential model for both the ground and excited state decays, using recent mass tables. Most of the values predicted for ground state decays are within the experimental limit for measurements (T_1/2 < 10³⁰ s). The minimum T_1/2 value refers to doubly magic or nearly doubly magic Sn (Z= 50) as the daughter nuclei. A comparison of log ₁₀(T_1/2) value reveals that the exotic cluster decay process slows down due to the presence of excess neutrons in the parent nuclei. The half-lives are also computed using the Universal formula for cluster decay (UNIV) of Poenaru et al and the Universal decay law (UDL) of Qi et al, and are compared with CPPM values and found to be in good agreement. A comparison of half-life for ground and excited systems reveals that probability of decay increases with a rise in temperature or otherwise, inclusion of excitation energy decreases the T_1/2 values.     

Ein experimenteller Beitrag zu der durch langsame Primärelektronen ausgelösten Sekundärelektronenemission

The energy distribution of secondary electrons emitted from a highly degassed polycristalline Pt surface was investigated as a function of low energy (V _p ) primary electrons 5<V _p <150eV. The measurements were carried out in an UHV of better than 10^?10 mm Hg. The dependence of the numberN _S ^(Ev) of secondary electrons of a fixed energyE _v (3<E _v <12eV) on the energyV _p of the primaries (=isochromates) is studied. A lot of observations can be detected:

1. I.
   The exit depth of true secondary electrons is strongly dependent of their energy.     
   
   

Resonant mechanism of axion photoproduction in a magnetized electron gas

It was shown that the contribution of diagrams with electron-positron vacuum excitation in a strong magnetic field B ? B ₀ = m ²/e = 4.41 × 10¹³ G in the Compton mechanism of axion production γe → ae at temperatures on the order of the axion mass exceeds the contribution of the “simple” Compton diagram and the contribution of the neutrino production γe → (ν\(\bar \nu \))e to the radiation power by many orders of magnitude. The conclusion is made on the probable axionic nature of the cold hidden mass of the Universe.     

Yukawa radiative corrections to the triple self-couplings of neutral <Emphasis Type="Italic">CP</Emphasis>-even Higgs bosons and to the <Emphasis Type="Italic">H → hh</Emphasis> decay rate within the minimal supersymmetric standard model

Within the minimal supersymmetric standard model, four self-couplings, λ _hhh , λ _hhH , λ _hHH , and λ _HHH , and the decay rate Γ(H → hh) are calculated with allowance for one-loop corrections induced by the contribution of the t, b, and c quarks, the τ lepton, and the corresponding superpartners and with the aid of the on-shell renormalization scheme. An analysis of the dependences of these features on tanβ and the mass of the A Higgs boson, M _A, shows that, in a specific region of the model-parameter space, the calculated corrections can make a significant contribution to the couplings and decay rate in the one-loop approximation. The inclusion of the radiative corrections in question is mandatory in reconstructing the Higgs potential.     

CAMEO project and discovery potential of the future 2<Emphasis Type="Italic">β</Emphasis>-decay experiments

The demands on the future supersensitivity 2β-decay experiments (aiming to observe neutrinoless 2β decay or to advance restrictions on the neutrino mass to m_ν≤0.01 eV) are considered and requirements for their discovery potential are formulated. The most realistic 2β projects are reviewed and the conclusion is obtained that only several of them with high energy resolution would completely satisfy these severe demands and requirements. At the same time, most of the recent projects (CAMEO, CUORE, DCBA, EXO, etc.) could certainly advance the limit on the neutrino mass up to m_ν≤0.05 eV.     

Dielectric Spectroscopy of Strongly Correlated Electronic States of Vanadium Dioxide

The thermal evolution of the conductivity of a VO₂ film and database-obtained band gap E_g of film nanocrystallites is traced in the temperature range of –196°C < T < 100°C (77 K < T < 273 K); the level position of donor impurity centers is determined to be E_d = 0.04 eV. It is shown that energy E_g decreases from 0.8 to ～0 eV with an increase in temperature in the range of 273 K < T < 300 K, which is caused by the narrowing of the energy gap due to correlation effects and considered as the temperature-extended Mott “insulator–metal” electron phase transition with the monoclinic lattice symmetry retained. The subsequent jump in the symmetry from monoclinic to tetragonal with a further increase in temperature is considered as the Peierls structural phase transition, the temperature of which is in the vicinity of 340 K and determined by the size effects, nonstoichiometry of VO₂ film nanocrystallites, and degree of their adhesion to the substrate.     

Resonance detection of dark matter axions using a DC SQUID

A method for detecting dark matter axions in which a dc SQUID serves as a detector is proposed. The SQUID is shown to be able to detect the magnetic field perturbations induced by its interaction with axions. The resonance signal appears as a current step in the SQUID current–voltage characteristic. The voltage of the step corresponds to the axion mass, while its height depends on the axion energy density in near-Earth space. The proposed method is aimed at detecting axions with masses m_a ? 10^–4 eV, which are of interest for both cosmology and particle physics.     

Kinetics of pulsed cathodoluminescence

The kinetics of pulsed cathodoluminescence, which appears upon irradiation of condensed media with high-power electron beams of nanosecond duration, is analyzed. Four types of emission are considered: recombination emission, exciton emission, intracenter emission, and emission of electron and hole centers. It is found that the maximum difference in the kinetics of the intensities of emission of these types occurs in the time interval t≤t ₁≈A ^?1, and, in the far afterglow, an exponential decay occurs with the characteristic time (2A)^?1 for the first and second types of luminescence and A ^?1 for the fourth type. For the intracenter luminescence, the decay time is equal to (2A)^?1 and A _i ^?1 for short-lived and long-lived radiative levels, respectively (A and A _i are the probabilities of linear recombination of electron-hole pairs and decay of a radiative level, respectively). In the case of long-lived radiative levels, a strong peak is observed in the spectrum of intracenter luminescence in the far afterglow.     

Neutrino mass bounds from neutrinoless double beta-decays and cosmological probes

We investigate the way the total mass sum of neutrinos can be constrained from the neutrinoless double beta-decay and cosmological probes with cosmic microwave background (CMBR), large-scale structures including 2dFGRS and SDSS datasets. First we discuss, in brief, the current status of neutrino mass bounds from neutrino beta decays and cosmic constraint within the flat ΛCMD model. In addition, we explore the interacting neutrino dark-energy model, where the evolution of neutrino masses is determined by quintessence scalar field, which is responsible for cosmic acceleration. Assuming the flatness of the Universe, the constraint we can derive from the current observation is \(\sum m_{\nu } < 0.87\) eV at 95% confidence level, which is consistent with \(\sum m_{\nu } < 0.68\) eV in the flat ΛCDM model without Lyman alpha forest data. In the presence of Lyman- α forest data, interacting dark-energy models prefer a weaker bound \(\sum m_{\nu } < 0.43\) eV to \(\sum m_{\nu } < 0.17\) eV (Seljark et al). Finally, we discuss the future prospect of the neutrino mass bound with weak-lensing effects.     

Measurement of polarization angular coefficients in <Emphasis Type="Italic">Z</Emphasis> boson leptonic decays with ATLAS at the LHC

This paper presents the complete set of polarization angular coefficients A _0?7 describing lepton angular distributions in Z boson decay, which were measured at the ATLAS experiment in proton–proton collisions with the energy √s = 8 TeV. Theoretical values for the difference A ₀ ? A ₂ calculated in the fixed-order QCD perturbation theory O(α _s ² ), demonstrate significant deviation from the measured data, which indicates the necessity of taking into account higher order corrections. The evidence of nonzero coefficients A _5,6,7 was obtained for the first time, in accordance with theoretical calculations in O(α _s ² ) approximation. Measurement of the polarization angular coefficients A _i is important for subsequent precision measurement of parameters of the electroweak model at the LHC, such as the sine of Weinberg electroweak mixing angle sin² θ _W and the W boson mass.     

Influence of the Axial-Vector Coupling Constant and the Energy Distribution Function on <Emphasis Type="Italic">β</Emphasis>-Decay Rates Within the Gross Theory of Beta Decay

We evaluate the β-decay rates within the gross theory of beta decay (GTBD) and compare the results for different values of the axial-vector coupling constant, g_A =?0.76, g_A =?0.88, g_A =?1, g_A =?1.13, and g_A =?1.26, and also different energy distribution functions like Gaussian, exponential, Lorentzian, and modified Lorentzian ones. We use new sets of parameters as well as updated experimental mass defects and also an improved approximation for the Fermi function. We compare our calculated results for a set of 94 nuclei of interest in pre-supernova phase, with experimental data in terrestrial conditions and also with other theoretical models like the QRPA, the shell model (SM), and different versions of the GTBD. We show that best results are obtained with g_A =?1 using Gaussian and Lorentzian distributions, being the rates for the 74 and 80% of our sample, respectively, of the same order of magnitude that of experimental data. Finally, we show that the present results within the GTBD are better than those within the QRPA model and also older versions of the GTBD for the isotopes of cobalt and iron families, and comparable with SM for some elements.