Search

The Russian-Italian Large Volume Detector (LVD) is located at the Gran Sasso underground laboratory at a depth of 3300 m w.e. To study the seasonal variations of the penetrating component of cosmic rays, the data on cosmic ray muons detected in 2001–2008 was analyzed, along with those associated with neutrons produced by muons since April 2003. One-year periodic variations of muons and neutrons produced by them were found. The maximum intensity is observed in July, in accord with theoretical concepts.

The history of cosmic ray research at the Lebedev Institute beginning with the first work and continuing up to now is reviewed. The milestones and main avenues of research are outlined. Pioneering studies on the nuclear cascade process in extensive air showers, investigations of the Vavilov–Cherenkov radiation, and some work on the origin of cosmic rays are discussed. Recent data on ultrahigh-energy particle detection at the Pierre Auger Observatory and the High Resolution Fly's Eye (HiRes) experiments are presented.

The problem of the relationship between the numbers of positively and negatively charged particles in the flux of cosmic-ray muons arriving at sea level with energies in excess of 0.1 TeV (up to 100 TeV) is discussed. It is shown that the formation of quark—gluon matter as the result of high-energy nuclear interactions leads to a reduction of the positive excess in cosmic-ray muons at the above energies. At the present time, the quark-gluon state of matter is studied in accelerator experiments at colliding-particle energies of up to √s = 200 GeV per nucleon. Estimates presented in this article for the positive excess of muons having energies of up to 3 or 4 TeV are based on available data from accelerator experiments; at higher muon energies, the respective estimates are based on extrapolating these data.

In this paper we show the capabilities of the Large Volume Detector (INFN Gran Sasso National Laboratory) to identify a neutrino burst associated with a supernova explosion, in the absence of an “external trigger”, e.g., an optical observation. We describe how the detector trigger and event selection have been optimized for this purpose, and we detail the algorithm used for the on-line burst recognition. The on-line sensitivity of the detector is defined and discussed in terms of supernova distance and ν ¯ e intensity at the source.

Potentialities of a multipurpose astrophysical orbital observatory designed on the basis of ionization-neutron calorimetry for direct studies of energy spectra and charge composition of the primary cosmic radiation in a wide energy range up to the “knee” energies (10 15 –10 16 eV) and other astrophysical goals are considered.

Potentialities of a multipurpose astrophysical orbital observatory designed on the basis of ionization-neutron calorimetry for direct studies of high-energy primary cosmic radiation is considered. Scientific goals of the project are discussed, including measurements of energy spectra and PCR charge composition in a wide energy range up to the "knee" energies (1015 – 1016 eV) as well as a number of other astrophysical goals.

A radiochemical 71 Ga- 71 Ge experiment to determine the primary flux of neutrinos from the Sun began measurements of the solar neutrino flux at the Baksan Neutrino Observatory in 1990. The number of 71 Ge atoms extracted from 30 tons of gallium in 1990 and from 57 tons of gallium in 1991 was measured in 12 runs during the period of January 1990 to December 1991. The combined 1990 and 1991 data-sets give a value of 58 + 17/ —24 (stat) ± 14 (syst) SNU. This is to be compared with 132 + 7/ —5 SNU predicted by the Standard Solar Model.

A new phenomenon—giant air showers of energy above 1020 eV,which lie beyond the Greisen-Zatsepin-Kuzmin cutoff—was discovered by various detection methods. The mechanism of particle acceleration to such high energies is still a puzzle. The arrival directions of giant showers do not contradict the hypothesis of their isotropic distribution. There are indications of their correlations with distant objects. It is obvious that only observations at new arrays can clarify the problem. The observed events must be reanalyzed within a more elaborate scheme. Verification of slight deviations from Lorentz invariance is possible.

A new complex installation ATHLET is now being built at Tien Shan near Almaty. Some problems of the planned cosmic ray studies are discussed.

We report on a search for low-energy neutrino (antineutrino) bursts in correlation with the 8 time coincident events observed by the gravitational waves detectors EXPLORER and NAUTILUS (GWD) during the year 2001. The search, conducted with the LVD detector (INFN Gran Sasso National Laboratory, Italy), has considered several neutrino reactions, corresponding to different neutrino species, and a wide range of time intervals around the (GWD) observed events. No evidence for statistically significant correlated signals in LVD has been found. Assuming two different origins for neutrino emission, the cooling of a neutron star from a core-collapse supernova or from coalescing neutron stars and the accretion of shocked matter, and taking into account neutrino oscillations, we derive limits to the total energy emitted in neutrinos and to the amount of accreting mass, respectively., Comment: Accepted for publication in Astronomy and Astrophysics

Combined analysis of the data of 92 runs of SAGE during the 12-year period January 1990 through December 2001 gives a capture rate of solar neutrinos with energy more than 233 keV of 70.9 −5.2 +5.3 (stat.) −3.2 +3.7 (syst.) SNU. This represents only 55% of the predicted standard solar model rate of ∼130 SNU. The results of individual runs as well as the results of combined analysis of all runs during yearly, monthly, and bimonthly periods are presented. No compelling evidence for temporal variations is observed. By an analysis of the SAGE results combined with those from all other solar neutrino experiments, we make the first estimate of the electron neutrino pp flux that reaches the Earth to be (4.6 ± 1.2) x 10 10 /(cm 2 s). Assuming that neutrinos oscillate to active flavors the pp neutrino flux emitted in the solar fusion reaction is approximately (7.6 ± 2.0) x 10 10 /(cm 2 s), in agreement with the standard solar model calculation of (5.95 ± 0.06) x 10 10 /(cm 2 s).

シャワー拡散層付エマルションチェンバーによるエネルギー決定法について報告する． この方法は，1995年の日ロ共同気球実験(RUNJOB-program, RUssia-Nippon JOint Balloon-program) で観測されたPeV陽子のエネルギー推定方法を基に開発され，1997年のRUNJOB実験より導入した．シャワー拡散層はカロリメーター層の下部に設置され，カロリメーター層で発達した電磁カスケードシャワーはシャワー拡散層で幾何学的に広がり，電子数密度が減少する．普通，電磁カスケードシャワーによるエネルギー決定の場合，シャワー最大発達点を捉えていないとそのエネルギーは信頼できない．しかし，本論文で報告する方法により，シャワー極大を捉えていない場合でもエネルギー決定が可能となった．約４ｃｍの厚さのシャワー拡散層があれば陽子の場合，６c.u.の鉛厚で数１０TeVまで，９c.u.あれば１００TeV近くまでシャワーエネルギーをσ～０．２以内の精度で決定できる．又，鉄核の場合，６c.u.の鉛厚で１００TeVまでのシャワーエネルギーをやはりσ～０．２以内の精度で決定できる．したがって，これまでシャワー極大を捉えていないためデータとして採用できないような高エネルギーシャワーについてもエネルギー決定が行え，特に高エネルギー領域の統計量を増やす事ができる．本論文では，主にシャワー拡散層付エマルションチェンバー内でのカスケードシャワーシミュレーション方法およびエネルギー決定精度について議論する．また実際にRUNJOB実験データに対して適用した例についても報告する．, We report a new energy determination method using the emulsion calorimeter with diffuser module. The idea of diffuser method is based on the energy estimation for a PeV proton observed by the first RUNJOB(RUssia-Nippon JOint Balloon-program) experiment in 1995 and we have used a new type of emulsion chamber with diffuser module since 1997. The diffuser module was set below calorimeter, and the electromagnetic cascade shower develops in the calorimeter, and spreads geometcally in the diffuser. In general, it is very hard to determine the energy unless we detect the shower maximum, but it might be possible to determine the shower energy with help of the diffuser module. We find the energy resolution is better than σ～0.2 for proton with several tens TeV and for iron with 100TeV if the path length of calorimeter and the diffuser are 6c.u. and 4cm respectively. With the thickness of calorimeter of 9c.u. with 4cm diffuser, we can estimate the energy up to nearly 100TeV for proton with the resolution of better than σ～0.2. In this report, we disscus the energy resolution in the present method based on the simulation calculation of cascade shower in the calorimeter with diffuser module. We show several events observed by RUNJOB experiment in 1997 and alloy the present method for the energy determination., 資料番号: SA0200107000

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 −6.2 −3.0 +6.2 +3.5 SNU, where the uncertainties are statistical and systematic, respectively. The experimental procedures and data analysis are presented.

We present measurements of the solar neutrino capture rate on metallic gallium in the Soviet-American gallium experiment (SAGE) over a period of slightly more than half the 22-year solar cycle. A combined analysis of 92 runs over the twelve-year period from January 1990 until December 2001 yields a capture rate of 70.8 −5.2 +5.3 (stat) −3.2 +3.7 (sys) SNU for solar neutrinos with energies above 0.233 MeV. This value is slightly more than half the rate predicted by the standard solar model, 130 SNU. We present the results of new runs since April 1998 and analyze all runs combined by years, months, and bimonthly periods beginning in 1990. A simple analysis of the SAGE results together with the results of other solar neutrino experiments gives an estimate of (4.6±1.2)× 1010 neutrinos cm−2 s−1 for the flux of the electron pp neutrinos that reach the Earth without changing their flavor. The flux of the pp neutrinos produced in thermonuclear reactions in the Sun is estimated to be (7.6 ± 2.0) × 1010 neutrinos cm−2 s−1, in agreement with the value of (5.95±0.06)×1010 neutrinos cm−2 s−1 predicted by the standard solar model.

The main goal of the Large Volume Detector (LVD) is to search for neutrino burst from gravitational stellar collapses in our Galaxy. The apparatus is shown to be able to register stellar collapse even if there is none of the antineutrino emission specific to the standard scenario. The data from more than nine years of detector operation have been processed, and no candidate events for neutrino bursts have been detected. This implies the existence of an experimental limit to the galactic stellar collapse rate in those cases where collapse is not accompanied by electron antineutrino emission: less than one event per 4.1 yr at the 90% confidence level.

The large geometric factor and good spatial resolution of the Large Volume Detector (LVD) ensures statistically significant and highly accurate measurements of muon trajectories and determination of the multiplicity of muon groups. The developed algorithm allows us to reconstruct 2 × 106 muon events (single muons and muon groups). Characteristics of muon groups are obtained and the specific yield of neutrons produced by single muons, muon groups, and showers is determined.

We report experimental results obtained by the emulsion chambers on board of the long duration balloon. We have been carrying out the trans-Siberian-continental balloon flight since 1995, and the results from 1995 to 1996 experiments are presented here. Total exposure of these two years amounts to 231.5 m 2 h at the average altitude of ∼32 km. The energy range covers 10–500 TeV for proton-primary, 3–70 TeV/n for helium-primary, and 1–5 TeV/n for Fe-group ( Z =26–28), though statistics of heavy components is not yet enough. Our preliminary data show that the spectra of the proton and the helium have nearly the same power indices ∼2.80, while those of heavier ones become gradually harder as the mass gets heavier, for instance the index is ∼2.70 for CNO-group and ∼2.55 for Fe-group. It is remarkable that a very high energy proton with multi-PeV is detected in 1995 experiment, and the estimated flux of this event coincides with a simple extrapolation from the energy spectrum with the power index 2.8 observed in the range 10–500 TeV. It indicates that there is no spectral break at around 100 TeV, in contrast to the maximum energy predicted by the current shock-wave acceleration model. This evidence requires some modification on the acceleration and/or propagation mechanism. Also we present all-particle spectrum and the average primary mass in the energy range 20–1000 TeV/particle. Our preliminary data show no drastic change in mass composition over the wide energy range, at least up to 1 PeV/particle, though the statistics is not yet enough to confirm it concretely. The flight performance and the procedure of the analysis, particularly the energy determination methods and the detection efficiency calculation are also given.

A new technique of the Ionization Neutron Calorimeter (INCA) to be installed aboard a satellite or a space station is capable of opening new horizons for cosmic-ray physics. The main goal of the experiment proposed is studying local nearby sources of high-energy cosmic rays by measuring the spectrum and composition of the nuclear component with the energy resolution of better than 30% that is sufficient for solution of these problems in the energy range 0.1–10 PeV, i.e., in the so-called “knee” region, and the spectrum of primary electrons in the energy range 0.1–10 TeV with the proton-background suppression factor up to 107. In addition, this experiment can provide new information on the cosmic-ray gamma-radiation in the energy interval 30 GeV–1 TeV, neutrons and gamma-rays from solar flares, and the existence of very massive exotic charged particles in cosmic radiation. The INCA is a calorimeter combining properties of conventional ionization calorimeters and classical neutron monitors. It can measure both the ionization produced by charged particles and evaporation neutrons arising as a result of excitation of heavy-absorber nuclei by cascade particles. The advantages of the INCA are not only excellent electron–proton separation but a high geometry factor of about 2 m 2 sr / ton owing to the INCA optimized composition and shape, whereas conventional ionization calorimeters are usually limited by geometry factor on the order of 0.1 m 2 sr / ton . To verify the INCA concept, a prototype was constructed and exposed to pion and proton accelerator beams with energies of 4 and 70 GeV, respectively, and to an electron beam with an energy of 200–550 MeV. The experimental data obtained agree well with the results of a Monte Carlo simulation by the SHIELD code.

The problem of charm generation in the interactions of nucleons with nuclei of air atoms at energies inaccessible at present-day accelerators is discussed. Both experimental data on cosmic-ray muons and the predictions of QCD-based theoretical models are used in analyzing the behavior of the differential cross sections for charmed-particle production at high energies. The calculated fluxes of muons and neutrinos arriving at sea level both along the vertical and along the horizontal direction are presented, together with their approximations for the interval 2×102–1010 GeV.

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 −7.0−3.0 +7.2+3.5 ) 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.

We report experimental results obtained by using a wide-gap type emulsion chamber flown in the first Japanese-Russo joint balloon project, called RUNJOB ( RU ssia- N ippon JO int B alloon-program). Two balloons were launched from Kamchatka in July 1995, and both were recovered successfully near the Volga River. The exposure time was 130 hours for the first flight and 168 hours for the second. The mean ceiling altitude, in both flights, was 32 km corresponding to 10 g/cm 2 . Total area of the emulsion chamber was 0.8 m 2 , and the thickness 0.385 and 2.28 collision m.f.p.'s for vertically incident proton- and iron-primaries, respectively. We detected 381 showers using Fuji-#200-type X-ray film; of these 174 showers were due to atmospheric secondary γ-rays, and the rest 207 came from nuclear components. The energy range covers 20∼200 TeV for proton-primary, 3∼30 TeV/nucleon for helium-primary, and 0.7∼5 TeV/nucleon for iron-primary. We give the energy spectra for various elements (proton, helium, …, iron) as well as the all-particle spectrum and the average mass of the cosmic-ray primaries.

The CERN Neutrino to Gran Sasso (CNGS) project aims to produce a high energy, wide band $\nu_{\mu}$ beam at CERN and send it toward the INFN Gran Sasso National Laboratory (LNGS), 732 km away. Its main goal is the observation of the $\nu_{\tau}$ appearance, through neutrino flavour oscillation. The beam started its operation in August 2006 for about 12 days: a total amount of $7.6~10^{17}$ protons were delivered to the target. The LVD detector, installed in hall A of the LNGS and mainly dedicated to the study of supernova neutrinos, was fully operating during the whole CNGS running time. A total number of 569 events were detected in coincidence with the beam spill time. This is in good agreement with the expected number of events from Montecarlo simulations., Comment: Accepted for publication by the European Physical Journal C ; 7 pages, 11 figures

Possibilities to put upper and lower limits on prompt atmospheric neutrino fluxes up to some hundreds of TeV are discussed. The conclusions are made based on charm production mechanism data being obtained from experiments on accelerators, modem theoretical considerations and on data on cosmic ray muons. Discrepancies which exist among the results set out in different works can be restricted.

The neutrino capture rate measured by the Russian-American Gallium Experiment is well below that predicted by solar models. To check the response of this experiment to low-energy neutrinos, a 517 kCi source of 51Cr was produced by irradiating 512.7 g of 92.4%-enriched 50Cr in a high-flux fast neutron reactor. This source, which mainly emits monoenergetic 747-keV neutrinos, was placed at the center of a 13.1 tonne target of liquid gallium and the cross section for the production of 71Ge by the inverse beta decay reaction was measured to be (5.55 +/- 0.60 (stat.) +/- 0.32 (syst.)) x 10^(-45) cm^2. The ratio of this cross section to the theoretical cross section of Bahcall for this reaction is 0.95 +/- 0.12 (exp.) +/- 0.03 (theor.) and to the cross section of Haxton is 0.87 +/- 0.11 (exp.) +/- 0.09 (theor.). This good agreement between prediction and observation implies that the overall experimental efficiency for the solar neutrino measurements is correctly determined and provides considerable evidence for the reliability of the solar neutrino measurement., 20 pages including figures in two column format

The latest results of studies of the gamma-ray spectra recorded together with charged particles in the Russian-Nippon Joint Balloon (RUNJOB) experiment are presented. A comparison of the experimental spectra with the results of the calculations based on assumptions of different intensities of the gamma-ray spec- tra demonstrates that the previously published intensities of primary cosmic rays measured in the RUNJOB experiments are underestimated.

An intense source of 37Ar was produced by the (n, α) reaction on 40Ca by irradiating calcium oxide in the fast neutron breeder reactor at Zarechny, Russia. The 37Ar was released from the solid target, sealed into a small source, and was used to irradiate 13 tonnes of gallium metal in the Russian-American gallium solar neutrino experiment SAGE. The initial source strength was 409 ± 2 kCi. The measured production rate of 71Ge on gallium metal was 11.0+1.0−0.9 (stat) ± 0.6 (syst.) atoms per day, which is 0.79+0.09−0.10 of the theoretically calculated production rate.

The paper considers the possibility of EAS production by charmed particles and direct muons (muons produced in decays of particles with a very short life-time comparing to that of charmed particles, as, for example, in decays of resonances). At large angles (≳ 70°) charmed particles and direct muons could be completely responsible for EAS measured at the sea level. The estimations are made for the primary nucleon energy 1019 eV and the angles 45–72°.

I. V. AMURINA,1 V. P. ANTONOVA,2 G. M. AUTOVA,3 M. K. BABAEV,4 A. S. BAYGUBEKOV,4 P. F. BEYL’,1 R. U. BEISEMBAEV,1 A. E. BODUNOV-SKVORTSOV,5 A. S. BORISOV,5 K. V. CHERDYNTSEVA,5 A. P. CHUBENKO,5 P. A. CHUBENKO,5 V. G. DENISOVA,5 V. I. DROBZHEV,2 E. N. GUDKOVA,5 A. V. GUREVICH,5 Z. M. GUSEVA,5 E. A. KANEVSKAYA,5 J. KEMPA,6 M. G. KOGAN,5 E. V. KOSTIN,5 O. N. KRYAKUNOVA,2 A. V. KRUGLOV,1 S. V. KRYUKOV,2 M. I. KRYLOWA,1 A. I. KUPCHISHIN,7 A. K. MANAGADZE,8 I. S. MART’YANOV,4 V. M. MAXIMENKO,5 K. M. MUKASHEV,3 R. A. MUKHAMEDSHIN,9 R. A. NAM,1 N. M. NESTEROVA,5 KH. NURITDINOV,10 V. V. OSKOMOV,7 V. P. PAVLYUCHENKO,5 V. V. PISCAL’,1 R. YU. POLYAKOV,1 V. S. PUCHKOV,5 S. E. PYATOVSKY,5 I. V. RAKOBOL’SKAYA,8 T. M. ROGANOVA,8 N. N. ROINISHVILI,11 V. A. RYABOV,5 N. O. SADUEV,7 T. KH. SADYKOV,4 S. B. SHAULOV,5 A. L. SHCHEPETOV,5 S. A. SLAVATINSKY,5 A. V. STEPANOV,1 L. G. SVESHNIKOVA,8 G. T. SHOIYNBAEVA,3 ZH. T. TOLEGEN,7 YU. N. VAVILOV,5 A. V. VARGASOV,5 N. G. VIL’DANOV,1 L. I. VIL’DANOVA,1 V. I. YAKOVLEV,5 T. S. YULDASHBAEV,10 N. N. ZASTROZHNOVA,4 G. T. ZATSEPIN9 and V. V. ZHUKOV1 1Tien Shan Mountain Scientific Station of LPI, Almaty, 480037 Kazakhstan 2Institute of Ionosphere, Ministry of Education and Science, Almaty, 480020 Kazakhstan 3Abai Almaty State University, Almaty, 480100 Kazakhstan 4Physical-Technical Institute of Academy of Sciences of Uzbekistan, Almaty, 700084 Kazakhstan 5P. N. Lebedev Physical Institute, Moscow, 119991 Russia 6Warsaw University of Technology, Warszawska Politechnika, Off-Campus, Plock, 09400 Poland 7Al-Faraby Kazakh National University, Ministry of Education and Science, Almaty, 480012 Kazakhstan 8D. V. Skobeltsyn Institute of Nuclear Physics, Moscow State University, Moscow, 119899 Russia 9Institute for Nuclear Research, Russian Academy of Sciences, Moscow, 117312 Russia 10Physical-Technical Institute of Academy of Sciences of Uzbekistan, Tashkent, 700084 Uzbekistan 11Institute of Physics Academy of Sciences of the Georgian Republic, Tbilisi, 380077 Georgia

The importance of an adequate CNGS beam monitor at the Gran Sasso Laboratory has been stressed in many papers. Since the number of internal $\nu_\mu$ CC and NC interactions in the various detectors will not allow to collect statistics rapidly, one should also be able to detect the $\nu_\mu$ CC interactions in the upstream rock. In this study we have investigated the performances of the LVD detector as a monitor for the CNGS neutrino beam. Thanks to its wide area ($13 \times 11 m^2$ orthogonal to the beam direction) LVD can detect about 120 muons per day originated by $\nu_\mu$ CC interactions in the rock. The LVD total mass is $\sim2 kt$. This allows to get 30 more CNGS events per day as internal $(NC + CC)$ $\nu_\mu$ interactions, for a total of $\sim 150$ events per day. A 3% statistical error can be reached in 7 days. Taking into account the time characteristics of the CNGS beam, the cosmic muon background can be reduced to a negligible level, of the order of 1.5 events per day., Comment: 15 pages, 11 figures, submitted to Nucl. Instr. Meth. Phys. Res. A

A method to detect 8B solar neutrinos is proposed using the charge current reaction νe19F with a hexafluorobenzene scintillation detector. The main advantage of the detector is the possibility of identifying neutrino events by a delayed coincidence with the β+ decay of 19Ne ( T 1 2 = 17 s ). Because of this the detector is potentially sensitive to neutrinos with an energy as low as 5 MeV. An additional advantage of the detector is the ability to select unambiguously the electron neutrino component of the burst from a stellar gravitational collapse.

The production of nuclear-active and electromagnetic particles, as well as long-lived isotopes in nuclear and electromagnetic showers generated by cosmic-ray muons at different depths underground is discussed. Characteristics of the secondary components and their dependence on the depth and the muon energy, obtained in experiments and calculations, are presented.

Since neutrinos and gamma-rays productions are often associated in many astrophysical processes, the detection of neutrinos in correlation with γ-ray bursts (GRBs) could be a very important step towards the discovery of the sources of these events. A search for low-energy neutrinos of all flavours in correlation with ≈ 200 γ-ray bursts detected by BATSE aboard the Compton Observatory has been performed by the LSD (Liquid-Scintillator Detector) neutrino telescope. This kind of telescope, differently from the water Cerenkov detectors, is also sensitive to νμ, τ and\(\bar \nu _{\mu , \tau } \) fluxes, through the charged-and neutral-current interactions of neutrinos with carbon nuclei. No νe, μ, τ or\(\bar \nu _{e,\mu ,\tau } \) candidate has been detected by LSD during the time interval in which BATSE detected 90% of the photon flux for any of the GRBs analysed. The corresponding upper limits to the neutrino fluxes, summed over 197 GRBs, are:\(F(\bar \nu _e ) \leqslant 1.5 \cdot 10^{11} cm^{ - 2} \), 9≤Eν≤50 MeV,\(F(\bar \nu _e ) \leqslant 2.5 \cdot 10^{10} cm^{ - 2} \), 20≤Eν≤50 MeV,F(νe)≤5.1·1011 cm−2, 25≤Eν ≤50 MeV,F(νμ, τ)≤7.5·1012 cm−2, 20≤Eν≤100 MeV,\(F(\bar \nu _{\mu , \tau } ) \leqslant 7.9 \cdot 10^{12} cm^{ - 2} \), 20≤Eν≤100 MeV.

The Russian-American Gallium Solar Neutrino Experiment (SAGE) is described. Beginning in September 1992, SAGE II data were taken with 55 tons of Ga and with significantly reduced backgrounds. The solar neutrino flux measured by 31 extractions through October 1993 is presented. The result of 69 {+-} 10 +5/{minus}7 SNU is to be compared with a Standard Solar Model prediction of 132 SNU.

The production of neutrinos with energies higher than 0.1 GeV in the solar atmosphere during solar flares is discussed. Neutrinos and muons are generated in decays of π+- mesons produced in nuclear interactions of accelerated solar flare protons with matter of the Sun. Muons themselves decay yielding neutrinos. These neutrinos could come to the Earth and be detected with neutrino telescopes. Estimations of fluxes of such neutrinos are given.

A radiochemical {sup 71}Ga-{sup 71}Ge experiment to determine the primary flux of neutrinos from the Sun began measurements of the solar neutrino flux at the Baksan Neutrino Observatory in 1990. The number of {sup 71}Ge atoms extracted from initially 30 and later 57 tons of metallic gallium was measured in fifteen runs during the period of January 1990 to May 1992. The observed capture rate is 70{plus_minus}19 (stat){plus_minus}10 (syst) SNU. This is to be compared with 132 SNU predicted by the Standard Solar Model.

Fifteen measurements of the solar neutrino flux have been made in a radiochemical 71Ga-71Ge experiment employing initially 30 t and later 57 t of liquid metallic gallium at the Baksan Neutrino Observatory between January 1990 and May 1992. This provides an integral measurement of the flux of solar neutrinos and in particular is sensitive to the dominant, low-energy p-p solar neutrinos. SAGE observed the capture rate to be 73−16+18 (stat.)−7+5 (syst.) SNU. This represents only 56%−60% of the capture rate predicted by different Standard Solar Models.

Medium energy neutrinos from decays of pions and kaons produced in interactions of protons, accelerated in solar flares, can come to the Earth and be detected with neutrino telescopes. Estimations of fluxes of these neutrinos are made in the work. Solar flare neutrinos as a possible source for experiments on searching for neutrino oscillations is discussed.

A radiochemical {sup 71}Ga-{sup 71}Ge experiment to determine the primary flux of neutrinos from the Sun has begun operation at the Baksan Neutrino Observatory. The number of {sup 71}Ge atoms extracted from thirty tons of gallium was measured in five runs during the period of January to July 1990. Assuming that the extraction efficiency for {sup 71}Ge atoms produced by solar neutrinos is the same as from natural Ge carrier, we observed the capture rate to be 20 + 15/{minus}20 (stat) {plus minus} 32 (syst) SNU, resulting in a limit of less than 79 SNU (90% CL). This is to be compared with 132 SNU predicted by the Standard Solar Model.

The Large Volume Detector (LVD) in the Gran Sasso underground Laboratory is a multipurpose detector consisting of a large volume of liquid scintillator interleaved with limited streamer tubes. In this paper we discuss its power to study low-energy cosmic neutrinos. The results show that the first LVD tower (368 tons of liquid scintillator) is well suited to detect neutrinos from gravitational stellar collapses within all of our Galaxy over a wide range of burst duration (up to a few hundred seconds). No burst candidates have been observed in the first two months of data taking.

The LSD liquid scintillation detector has been operating since 1985 as an underground neutrino observatory in the Mont Blanc Laboratory with the main objective of detecting antineutrino bursts from collapsing stars. In August 1988 the construction of an additional lead and borex paraffin shield considerably reduced the radioactive background and increased the sensitivity of the apparatus. In this way the search for steady fluxes of low-energy neutrinos of different flavours through their interactions with free protons and carbon nuclei of the scintillator was made possible. No evidence for a galactic collapse was observed during the whole period of measurement. The corresponding 90% c.l. upper limit on the galactic collapses rate is 0.45 y −1 for a burst duration of ΔT ⩽ 10 s. After analysing the last 3 years data, the following 90% c.l. upper limits on the steady neutrino and antineutrino fluxes were obtained: Φ( \ gn e ) 4 \ gn e s −1 cm −2 9 ⩽ E ν ⩽ 50MeV Φ( \ gn e ) 3 \ gn e s −1 cm −2 20 ⩽ E ν ⩽ 50MeV Φ(ν e ) 3 ν e s −1 cm −2 25 ⩽ E ν ⩽ 50 MeV Φ(ν μ + τ ) 7 ν μ + τ s −1 cm −2 20 ⩽ E ν ⩽ 100 MeV Φ( \ gn μ + τ ) 7 \ gn μ + τ s −1 cm −2 20 ⩽ E ν ⩽ 100 MeV In particular comparing the obtained upper limit on the \ gn e flux for 9 ⩽ E ν ⩽ 20 MeV to the solar ν e flux predicted by the standard solar model in the same range of energy, we can exclude the possibility that more than 6.3% of the solar ν e 's flux can change to \ gn e . Finally the first limits on the flux of relic supernova neutrinos of all flavours as a function of the neutrino sea temperature are presented.

A common prejudice is that neutrinos produced by the decays of real or virtual Z0-bosons do not oscillate. We will show that this is incorrect even in case of the universality of interactions and of the absence of sterile neutrinos. In Z0-decay the coherent state of neutrino pairs is produced. The oscillation picture can be observed in principle by measuring the flavors of both neutrinos from the same Z0-decay.

A number of new huge neutrino telescopes have been built, are being built, and are planned to be built all over the world. With these setups, cosmic neutrinos of high energies can be studied experimentally. Atmospheric neutrinos represent the main backgrounds to such experiments—namely, the atmospheric neutrinos determine how large a setup should be to measure diffuse cosmic neutrino fluxes or what angular resolution of a setup should be in order that searches for pointlike neutrino sources in the sky be successful. The atmospheric-neutrino fluxes are calculated in the present study. At high energies, the atmospheric-neutrino fluxes consist mostly of neutrinos produced in the atmosphere through charmed-particle decays. Three sources of information about charm production are used: (1) data obtained in accelerator experiments, (2) data on cosmicray muons, and (3) predictions of the NLO and QGSM QCD models for the charm-production at energies not available at modern accelerators. The uncertainties in the calculated fluxes of atmospheric neutrinos from charmed-particle decays are estimated to be at a level of 3–5 orders of magnitude.

A radiochemical {sup 71}Ga-{sup 71}Ge experiment using 30 tons of gallium to determine the primary flux of neutrinos from the Sun has begun operation at the Baksan Neutrino Observatory in the U.S.S.R. Assuming that the extraction efficiency for {sup 71}Ge atoms produced by solar neutrinos is the same as from natural Ge carrier, we observed the capture rate to be 20{sub {minus}20}{sup +15}(stat){plus minus}32(syst) solar neutrino units (SNU), resulting in a limit of less than 79 SNU (90% C.L.). This is to be compared with 132 SNU predicted by the standard solar model.

The Soviet-American Gallium Experiment is the first experiment able to measure the dominant flux of low energy p-p solar neutrinos. Four extractions made during January to May 1990 from 30 tons of gallium have been counted and indicate that the flux is consistent with 0 SNU and is less than 72 SNU (68% CL) and less than 138 SNU (95% CL). This is to be compared with the flux of 132 SNU predicted by the Standard Solar Model.

The data recorded with the neutrino detectors at Mont Blanc, Kamioka, Baksan and with the gravitational-wave detectors in Maryland and Rome have been analysed searching for correlations associated with SN 1987 A, without presuming or excluding hypotheses for correlations due to neutrinos and gravitational waves. The statistical analysis has been based on a previous analysis that showed a correlation among Maryland, Rome and Mont Blanc with a probability to be accidental less than 10−5. Independent correlations are found during a period of one or two hours, around the Mont Blanc 5ν burst (2h 52 min 36 s UT), among the various sets of data: Mont Blanc-Baksan with a probability to be accidental of the order ofp∼4·10−3, Mont Blanc-Kamioka withp∼4·10−3, Maryland-Rome-Kamioka withp∼5·10−4, Maryland-Rome-Baksan withp∼5·10−2. It is remarkable that the events from all the neutrino detectors follow the signals from the g.w. detectors by a time of the order of 1/2 or 1 s. At present we will not give a physical interpretation of the observed correlations which have strong statistical significance.

We present evidence for a dependence of the average deep underground muon energies on shower size in the coincident EAS-TOP and LVD data at the Gran Sasso laboratories. The measured relation agrees with a mixed chemical composition of the cosmic ray primary spectrum at energies around 10(15) eV. (C) 1998 Elsevier Science B.V.

The possibility of detecting neutrinos from the Sun and supernovae with detectors based on the nuclei 7Li, 19F, 127I, and 23Na is discussed.