Search

Low background segmented liquid scintillator detector, doped with an indium as a target for solar neutrino registration, can be used for measuring total solar neutrino spectrum including neutrinos. A detector consisting of small modules filled with liquid scintillator in the volume of 1–2 L is considered. Silicon matrices are used for light collection. The background of indium beta-activity is suppressed by triple coincidences. The detector of such a type can measure Be neutrino flux with high accuracy and independently check the measurement performed by the Borexino Collaboration. [ABSTRACT FROM AUTHOR]

We analyze neutrino fluxes near the surface of a protoneutron star in type II supernova explosions. For magnetorotational explosion mechanism it is shown that effective neutrino collisions in a magnetized nucleon gas caused by the neutral current Gamow–Teller component lead to neutrino acceleration. Such an effect originates from spin-projection asymmetry in phase space volume of outer channel neutrino due to nucleon magnetic moment interaction with magnetic field. Respective increase in a hardness of the energy spectrum is favorable for observations of supernova neutrinos using neutrino telescopes. The possibilities of detecting supernova neutrinos by large-volume Cherenkov observatories—KM3NeT and Baikal-GVD—are discussed. As is demonstrated the upper limits of the distance thresholds for such observations can be increased by a factor of , when employing the -fold coincidence technique in data processing. [ABSTRACT FROM AUTHOR]

The LVD detector, located in the Gran Sasso Laboratory at a depth of 3600 m w.e., is designed for research in the field of neutrino physics, astrophysics, cosmic ray physics and the search for rare processes predicted by theory. The LVD experiment was built in 1991 to detect neutrinos from collapses of stellar nuclei in our galaxy. The background of the detector is atmospheric muons, neutrons generated by muons in the detector material and natural radioactivity underground. The report presents the latest experimental results obtained at LVD: a limit on the frequency of supernova outbreaks, muon variations with a period of 1, 4, 10 years, and also describes the problems of studying the low-energy background underground. [ABSTRACT FROM AUTHOR]

The process of neutrino interaction with and nuclei is studied with allowance for the effect of charge-exchange resonances. The results obtained by calculating the cross section for solar-neutrino capture by the isotopes Mo and Mo, , are presented. Use is made of both experimental data obtained for the strength functions in () and ( He, ) charge-exchange reactions and the strength functions calculated within the theory of finite Fermi systems. The effect of the resonance structure of on the calculated cross sections for solar-neutrino capture is studied, and the contribution of each high-lying resonance to the capture cross section is isolated. The contributions of all components of the solar neutrino spectrum are calculated. The contribution of background solar neutrinos to the double-beta decay of Mo nuclei is estimated. [ABSTRACT FROM AUTHOR]

A modification of the LENS (Low Energy Neutrino Spectroscopy) project for spectroscopy of solar neutrinos with energies above about 715 keV on the basis of new technologies and solutions is examined. The respective detector employs In nuclei as a target for neutrinos. The creation of a detector containing about 200 t of a scintillator loaded with 10 t of indium will make it possible to measure, within five years, the energy spectra of solar neutrinos from Be, neutrinos from the CNO cycle, and neutrinos with small systematic errors. The detector was simulated in the form of a set of cells of a liquid scintillator doped with indium (about 10 in weight). Necessary technical conditions for detector cells are formulated, and the possible counting rate for events induced by internal and external backgrounds and characterized by an energy release of 600 to 1600 keV is estimated. It is shown that such a detector is implementable, in principle. [ABSTRACT FROM AUTHOR]

Neutrino oscillation is an experimentally established phenomenon by which neutrinos undergo flavor transformations periodically as they propagate large enough distances. Oscillation experiments provide information about the mass-squared differences and the leptonic mixing angles, but they are insensitive to the absolute mass scale for the neutrinos. As neutrino oscillations give no information about the absolute value of the neutrino mass squared eigenvalues, hence, there are various possibilities of neutrino hierarchy spectrums consistent with solar and atmospheric neutrino oscillation data. In this paper, we have attempted to present a picture of neutrino mass spectrum in the case of normal, inverted and almost degenerate hierarchy of neutrino masses by taking some specific choice of effective mass of electron neutrino related to 0 decay. We find neutrino mass eigenvalues in different neutrino mass spectrum and also calculate percentage change in mass eigenvalues by taking uncertainties in the best fit neutrino oscillation parameters. The normal and inverted mass ordering of neutrino masses in context of future double–beta–decay experiments is discussed at the end. [ABSTRACT FROM AUTHOR]

Neutrino astronomy offers a novel view of the non-thermal Universe and is complementary to other astronomical disciplines. The field has seen rapid progress in recent years, including the first detection of astrophysical neutrinos in the TeV–PeV energy range by IceCube and the first identified extragalactic neutrino source (TXS 0506+056). Further discoveries are aimed for with new cubic-kilometer telescopes in the Northern Hemisphere: Baikal-GVD, in Lake Baikal, and KM3NeT-ARCA, in the Mediterranean sea. The construction of Baikal-GVD proceeds as planned; the detector currently includes over 2000 optical modules arranged on 56 strings, providing an effective volume of 0.35 km . We review the scientific case for Baikal-GVD, the construction plan, and first results from the partially built array. [ABSTRACT FROM AUTHOR]

The resonance structure of the charge-exchange strength function and its effect on the cross sections for solar-neutrino capture by I nuclei are analyzed. Three types of isobaric resonances are studied within the self-consistent theory of finite Fermi systems. These are the giant Gamow–Teller resonance; the analog resonance; and the pygmy resonances, which lie lower. The capture cross section for solar neutrinos incident to I nuclei is calculated with allowance for the resonance structure of the strength function , and the effect of each resonance on the energy dependence is analyzed. It is shown that all high-lying charge-exchange resonances should be taken into account in calculating the cross section . The contributions of neutrinos of different origin to the structure of the cross section are analyzed. In particular, the contribution of energetic neutrinos to the ratio of the Xe and Xe production rates is considered. The Xe Xe isotope ratio is an indicator of hard boron neutrinos in the solar spectrum. [ABSTRACT FROM AUTHOR]

The Gamow–Teller strength functions as well as electron capture and decay rates for Ni in hot stellar environment are calculated within a thermodynamically consistent approach based on the thermal quasiparticle RPA. We present a thorough analysis of the tensor interaction effects on the GT strength functions at zero and finite temperatures. To this aim we use self-consistent calculations with the Skyrme interaction. Several Skyrme interactions are used in order to verify the sensitivity of the obtained results to the Skyrme force parameters. It is pointed out that finite temperature amplifies the effect of tensor correlations on the GT strength functions. Our calculations of electron capture and decay rates demonstrate the importance of the tensor interaction for simulation of supernova weak-interaction processes. [ABSTRACT FROM AUTHOR]

The resonance structure of the charge-exchange strength function S(E) is studied. Three types of isobaric resonances are considered within the self-consistent theory of finite Fermi systems and within its model approximation. These are giant Gamow-Teller, analog, and pygmy resonances (GTR, AR, and PR, respectively). The energies calculated for GTR, AR and three PRs agree well with experimental data. In heavy nuclei, the energy difference ΔEG-A = EGTR — EAR tends to zero, which corresponds to restoration of Wigner's SU(4) symmetry. The average deviation of the calculated values of ΔEG-A from known experimental data for 33 nuclei is 0.30 MeV. The root-mean-square deviations of the calculated energies of pygmy resonances from experimental data are also moderately small, δE < 0.40 MeV. The strength function S(E) is calculated for the isotopes 71Ga, 98Mo, 118Sn, and 127I. The calculated values of the resonance energies and resonance-peak parameters are close to their experimental counterparts. A strong effect of charge-exchange resonances on neutrino-capture cross sections, including those for solar neutrinos, is demonstrated. [ABSTRACT FROM AUTHOR]

The cross section σ(Eν) for solar-neutrino capture by the 76Ge nucleus is calculated. The effect of Gamow-Teller resonances on the rate of neutrino capture in the reaction 76Ge (ν, e−)76 As is studied. It is shown that the contribution of high-lying Gamow-Teller resonances to the charge-exchange strength function increases the rate of solar-neutrino capture by 25% to 50%, depending on the normalization method and on the inclusion of the quenching effect. [ABSTRACT FROM AUTHOR]

The Nozie res-Pines method for describing neutron scattering on a heated Fermi liquid (liquid 3He) is used to calculate cross sections for inelastic neutrino scattering on the isotope 54Fe, which is an element that plays a key role in the cooling of supernovae. The calculation in question is performed on the basis of the the theory of finite Fermi systems with the aid of the DF3-a Fayans energy density functional. [ABSTRACT FROM AUTHOR]

A technique for the measurement of activities of intense β sources by measuring the continuous gamma-radiation (internal bremsstrahlung) spectra is developed. A method for reconstructing the spectrum recorded by a germanium semiconductor detector is described. A method for the absolute measurement of the internal bremsstrahlung spectrum of Cr is presented. [ABSTRACT FROM AUTHOR]

Academician M.A. Markov in the 1960s first proposed detecting the electron antineutrino in the reaction of inverse beta decay on a proton to study the processes inside the Earth. The radioactive isotopes U, Th, and K present in our planet decay with radiation of neutrinos (antineutrinos). Neutrinos that are produced reach the Earth's surface practically without absorption and carry information about the internal structure of the planet. However, because of the smallness of the antineutrino fluxes and interaction cross sections with matter, antineutrinos of geological origin were first registered in only two experiments (Borexino and Kamland) in recent years. The experimental observation of antineutrinos from the isotope decays in the depths of the Earth is the only way to study the radiation in our planetary interior. [ABSTRACT FROM AUTHOR]

The results of gallium measurements of solar neutrino and measurements with artificial sources of neutrinos are presented. Conclusions are drawn from these results, and the potential of the SAGE experiment for studying transitions of active neutrinos to sterile states for Δ m > 0.5 eV and a sensitivity of a few percent to the disappearance of electron neutrinos is examined. [ABSTRACT FROM AUTHOR]

The effect of flavor day-night asymmetry is considered for solar neutrinos of energy about 1 MeV under the assumption that the electron-density distribution within the Earth is approximately piecewise continuous on the scale of the neutrino-oscillation length. In this approximation, the resulting asymmetry factor for beryllium neutrinos does not depend on the structure of the inner Earth’s layers or on the properties of the detector used. Its numerical estimate is on the order of −4 × 10 −4, which is far beyond the reach of present-day experiments. [ABSTRACT FROM AUTHOR]

Data of the Borexino experiment on the detection of the reaction involving elastic solar-neutrino scattering on an electron are presented. The fraction of electron neutrinos in the fluxes of Be and B neutrinos is in agreement with the LMA MSW oscillation solution. The uniquely low level of the Borexino detector background made it possible to set new limits on the effective magnetic moment of the neutrino, on the possible violation of the Pauli exclusion principle, and on some other rare processes. [ABSTRACT FROM AUTHOR]

The results of a direct measurement of the counting rate for solar neutrinos from the electron-capture process on 7Be, 7Be( e−, ν e)7Li( E ν = 0.862 MeV), with the low-background scintillation detector BOREXINO are presented. This is the first ever real-time observation of a signal from solar neutrinos of energy below 1 MeV. The counting rate for monoenergetic beryllium neutrinos in the BOREXINO detector proved to be 47 ± 7 (stat.) ± 12 (syst.) counts/(day × 100 t), which is in agreement with the predictions of the standard solar model and the hypothesis of neutrino oscillations in matter with parameters in the LMA region. [ABSTRACT FROM AUTHOR]

The current status of neutrino long-baseline accelerator experiments and new results obtained in these experiments are presented. Prospects for near-future program are also discussed. [ABSTRACT FROM AUTHOR]

A new analysis of the precise experimental astrophysical S factors for the direct-capture reaction 7Be( p, γ)8B [A.J. Junghans et al., Phys. Rev. C 68, 065803 (2003) and L.T. Baby et al., Phys. Rev. C 67, 065805 (2003)] is carried out on the basis of a modified two-body potential approach in which the direct astrophysical S factor, S17( E), is expressed in terms of the asymptotic normalization constants for p + 7Be → 8B and two additional conditions are involved to verify the peripheral character of the reaction under consideration. The Woods-Saxon potential form is used for the bound-( p + 7Be)-state wave function and for p7Be-scattering wave function. New estimates are obtained for the “indirectly measured” values of the asymptotic normalization constants (the nuclear vertex constants) for the p + 7Be → 8B and S17( E) at E ≤ 115 keV, including E = 0. These values of S17( E) and asymptotic normalization constants have been used for obtaining the indirectly measured values of the s-wave average scattering length and the p-wave effective-range parameters for p7Be scattering. [ABSTRACT FROM AUTHOR]

We consider the possibilities of studying a supernova collapse neutrino burst at Baksan Neutrino Observatory (Institute for Nuclear Research, Russian Academy of Sciences) using the proposed 5-kt target-mass liquid scintillation spectrometer. Attention is given to the influence of mixing angle ϑ 13 on the expected rates and spectra of neutrino events. [ABSTRACT FROM AUTHOR]

Experiments sensitive to pp neutrinos from the Sun are very promising for precise measurement of the mixing angle ϑ 12. A νe − scattering experiment (XMASS) and/or a charged-current experiment (indium detector) can measure the flux of electron pp neutrinos. One can find the total flux of pp neutrinos from a luminosity constraint after the contributions of 7Be and CNO neutrinos to the total luminosity of the Sun are measured. A radiochemical experiment utilizing a lithium target has high sensitivity to the CNO neutrinos; thus, it has a good promise for precise measurement of the mixing angle and for a test of the current theory of evolution of the stars. [ABSTRACT FROM AUTHOR]

The XMASS project utilizes ultrapure liquid xenon and aims to detect pp and 7Be solar neutrinos by means of ν e e scattering. It requires low background and a low threshold, which will also enable us to search for dark matter in the Galactic halo. By using a prototype detector, we have confirmed its feasibility to realize low background and low threshold. We have estimated the sensitivity of an 800-kg liquid-xenon detector for a dark matter search experiment based on the experimental results. [ABSTRACT FROM AUTHOR]

The Sun is a plasma diffuser that selectively moves light elements like H and He and the lighter isotopes of each element to its surface. The Sun formed on the collapsed core of a supernova (SN) and is composed mostly of elements made near the SN core (Fe, O, Ni, Si, and S), like the rocky planets and ordinary meteorites. Neutron emission from the central neutron star triggers a series of reactions that generate solar luminosity, solar neutrinos, solar mass fractionation, and an outpouring of hydrogen in the solar wind. Mass fractionation seems to have operated in the parent star and likely occurs in other stars as well. [ABSTRACT FROM AUTHOR]

Measurements are needed of low-energy antineutrinos generated by possible neutron decay at the core of the Sun. The measurement will test the validity of a proposal that solar luminosity, solar neutrinos, and the outpouring of H+ ions from the solar surface are the products of a chain of reactions triggered by neutron emission from the solar core. Inverse β decay of 87-d 35S, induced by capture of low-energy antineutrinos on 35Cl, is a likely candidate for this measurement.© 2004 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

It is shown that a large-volume liquid organic scintillator detector with an energy resolution of 10 keV at 200 keV (1σ) will be sensitive to solar pp neutrinos, if operated at the target radiopurity levels for the Borexino detector or the solar neutrino project of KamLAND.© 2004 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

The solar neutrino capture rate measured by the Russian–American Gallium Experiment on a metallic gallium target SAGE during the time from January 1990 through December 2000 is 77.0[sup +6.2][sub -6.2][sup +3.5][sub -3.0] SNU, where the uncertainties are statistical and systematic, respectively. The experimental procedures and data analysis are presented.© 2002 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

The new project GENIUS will cover a wide range of the parameter space of predictions of supersymmetry for neutralinos as cold dark matter. Further, it has the potential to be a real-time detector for low-energy (pp and [sup 7]Be) solar neutrinos. The GENIUS Test Facility has just been funded and will come into operation by the end of 2001.© 2002 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

A global analysis of solar (including the recent SNO result), atmospheric, and reactor neutrino data is presented in terms of three- and four-neutrino oscillations. We first present the allowed regions of solar and atmospheric oscillation parameters assuming three-neutrino families, showing that in this framework it is possible to reconcile the two anomalies and providing an unified fit of all the observables at a time. Then, we consider scenarios where a sterile neutrino is added to the three standard ones and the mass spectra present two separate doublets. We evaluate the allowed active-sterile admixture in both solar and atmospheric oscillations, showing that, although the Super-Kamiokande data disfavor both the pure ν[sub μ]→ν[sub s] atmospheric channel and, in combination with SNO, the pure ν[sub e]→ν[sub s] solar channel, the result from the combined analysis still favors close-to-pure active and sterile oscillations and disfavors oscillations into a near-maximal active-sterile admixture.© 2002 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

Solar neutrinos from the decay of [sup 8]B have been detected at the Sudbury Neutrino Observatory (SNO) via the charged current (CC) reaction on deuterium and by the elastic scattering (ES) of electrons. The CC reaction is sensitive exclusively to ν[sub e], while the ES reaction also has a small sensitivity to ν[sub μ] and ν[sub τ]. The flux of ν[sub e] from [sup 8]B decay measured by the CC reaction rate is φ[sup CC](ν[sub e])=[1.75±0.07 (stat.)[sup +0.12][sub -0.11] (syst.)±0.05 (theor.)]×10[sup 6]cm[sup -2]s[sup -1]. Assuming no flavor transformation, the flux inferred from the ES reaction rate is φ[sup EC](ν[sub x])=[2.39±0.34 (stat.) [sup +0.16][sub -0.14] (syst.)]×10[sup 6]cm[sup -2]s[sup -1]. Comparison of φ[sup CC](ν[sub e] to the Super-Kamiokande collaboration’s precision value of φ[sup EC](ν[sub x] yields a 3.3σ difference, assuming the systematic uncertainties are normally distributed, providing evidence that there is a nonelectron flavor active neutrino component in the solar flux. The total flux of active [sup 8]B neutrinos is thus determined to be (5.44±0.99)×10[sup 6]cm[sup -2]s[sup -1], in close agreement with the predictions of solar models.© 2002 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

The LENS detector is a ν[sub e]- flavor real-time detector for measurement of low-energy solar neutrino flux and spectral shape, specifying the pp and [sup 7]Be neutrinos individually. It will complement future low-energy neutrino experiments (BOREXINO, HELLAZ, GENIUS), all of which are scattering experiments. The main goal of the LENS collaboration is to develop final formulation of Yb- and In-loaded liquid scintillators and to build a prototype of suitable volume to study the backgrounds and detector performance.© 2002 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

Data on a direct determination of systematic uncertainties caused by the background production of germanium isotopes in the radiochemical SAGE experiment measuring the solar-neutrino flux are analyzed. The result obtained for the rate of [sup 68]Ge production is 6.5(1±1.0) times greater than the expected one; the rate of [sup 69]Ge production does not exceed preliminary estimates. The above result for [sup 68]Ge corresponds to the systematic uncertainty that is caused by the interaction of cosmic-ray muons and which is equal to 5.8% (4.5 SNU) at a solar-neutrino-capture rate of 77.0 SNU. An experiment is proposed that would test the effect of cosmic-ray muon influence on the SAGE systematic uncertainty and which would be performed at the location of the underground scintillation telescope facilities of the Baksan Neutrino Observatory (Institute for Nuclear Research, Russian Academy of Sciences).© 2002 MAIK “Nauka / Interperiodica”. [ABSTRACT FROM AUTHOR]

Neutrino oscillations in matter and in a magnetic field are investigated within models involving an extended Higgs sector. The left-right model containing a bidoublet and two triplets of Higgs fields (LRM) and the general two-Higgs-doublet model (GTHDM) are chosen by way of example. It is shown that the interaction of leptons with physical Higgs bosons can substantially change the pattern of oscillations in these models in relation to the predictions of the Standard Model (SM). Upper limits on the Yukawa coupling constants and on the Higgs boson masses are found in order to obtain maximum corrections to the SM solar-matter potential V[sup SM]. By using constraints on these parameters from the literature and those that are obtained here, it is possible to estimate corrections to V[sup SM] that come exclusively from charged Higgs bosons. The maximum value of these corrections is 40% of V[sup SM] within the LRM and 10% of V[sup SM] within the GTHDM. The entire body of information about the contributions of physical Higgs bosons to the solar-matter potential can be obtained by studying the Lorentz structure of the amplitudes for the reactions e[sup -]ν[sub l] → e[sup -]ν[sub l], at low energies. [ABSTRACT FROM AUTHOR]

The possibility of calibrating the solar-neutrino detectors GNO, BOREXINO, and LENS with the same artificial neutrino source is discussed. For this purpose, the Russian heavy-water reactor L-2 can be used to produce a 10 MCi neutrino source based on the [sup 51]Cr isotope. For the first time, the possibility of producing and using a neutrino source based on the [sup 75]Se isotope is demonstrated. [ABSTRACT FROM AUTHOR]

The data collected in the SuperKamiokande detector as of June 1999 are presented. This review covers the complete spectrum of neutrino interactions from solar neutrinos, through the entire spectrum of atmospheric neutrinos, and ending with the neutrino beam produced at KEK for a long-baseline experiment. Different interpretations of these data as demonstrations of neutrino oscillations are discussed. The results of a search for nucleon decay are also summarized. [ABSTRACT FROM AUTHOR]

The solar-neutrino-capture rate measured by the Russian-American Gallium Experiment on metallic gallium during the period from January 1990 to December 1997 is (67.2[sup +7.2 +3.5, sub -7.0 - 3.0]) SNU, where the uncertainties are statistical and systematic, respectively. This result represents a 7σ depression in the neutrino flux in relation to the predicted standard-solar-model rates. The experimental procedures used and data analysis are presented. [ABSTRACT FROM AUTHOR]

Time variations of solar neutrino flux are investigated on the basis of available Homestake experimental data for more than two solar cycles (1970-1994). At first, we determine (with the weight-time function by taking into account [sup 37]Ar decay), for each solar neutrino run n, the effective Earth's heliolatitude L[sub eff](n), the effective Zurich sunspots number Z[sub eff](n), the effective latitude of sunspots distribution Λ[sub eff](n), and the effective surfaces of sunspots in different heliolatitude belts. Then, we consider the correlation of solar-electron-neutrino fluxes with these parameters for different periods of solar activity. It is found that correlation coefficients change sign in different periods of solar activity, so that for total period 1970-1994 the correlation coefficient is very small. The obtained information indicates that a neutrino should have nonzero mass and nonzero magnetic moment. [ABSTRACT FROM AUTHOR]

With effective heliolatitude L[sub eff](n) for each solar-neutrino run n we separate all available Homestake experimental data for more than two solar cycles (1970-1994) on three zones SOUTH, EQUATORIAL, and NORTH in dependence on the heliolatitude (where detected neutrinos cross the Sun's surface). For each latitudinal zone, we determine the average solar electron neutrino flux and correlations with effective solar-activity parameters for asymmetrical latitudinal belts. The obtained results indicate that neutrino should have nonzero mass and nonzero magnetic moment. [ABSTRACT FROM AUTHOR]

Although less than 1% of solar energy is generated in the CNO cycle, it plays a critical role in astrophysics, since this cycle is the primary source of energy in certain more massive stars and at later stages of evolution of solar-type stars. Electron neutrinos are produced in the CNO cycle reactions. These neutrinos may be detected by terrestrial neutrino detectors. Various solar models with different abundances of elements heavier than helium predict different CNO neutrino fluxes. A direct measurement of the CNO neutrino flux could help distinguish between these models and solve several other astrophysical problems. No CNO neutrinos have been detected directly thus far, and the best upper limit on their flux was set in the Borexino experiment. The work on reducing the background in the region of energies of CNO neutrinos (up to 1.74 MeV) and developing novel data analysis methods is presently under way. These efforts may help detect the CNO neutrino flux in the Borexino experiment at the level predicted by solar models. [ABSTRACT FROM AUTHOR]