Proposal of a laser radiochemical Ga detector of solar neutrinos

The technique of laser discrimination of ⁷¹Ge β-decay events in a radiochemical detector of low energy solar neutrinos is proposed and considered. This technique is based on laser selective photoionization of single Ga atom. Preliminary experiments are presented.     

Method for recording of solar neutrinos with a lithium detector

A method for solar neutrino recording on a laboratory bench with a lithium detector is developed. The efficiency of extraction of beryllium from lithium as high as 96.4% is achieved, and it is shown that lithium extraction losses are less than 1%. The results of a full-scale experiment with a 10-t lithium detector consisting of 20 500-kg modules are presented. Technical solutions based on the experimental results open the way to designing a pilot facility intended for 500 kg of lithium.     

Feasibility and physics potential of detecting ~8B solar neutrinos at JUNO

The Jiangmen Underground Neutrino Observatory(JUNO) features a 20 kt multi-purpose underground liquid scintillator sphere as its main detector. Some of JUNO's features make it an excellent location for ~8B solar neutrino measurements, such as its low-energy threshold, high energy resolution compared with water Cherenkov detectors, and much larger target mass compared with previous liquid scintillator detectors. In this paper, we present a comprehensive assessment of JUNO's potential for detecting ~8B solar neutrinos via the neutrino-electron elastic scattering process. A reduced 2 MeV threshold for the recoil electron energy is found to be achievable, assuming that the intrinsic radioactive background 238 U and 232 Th in the liquid scintillator can be controlled to 10~(-17) g/g. With ten years of data acquisition, approximately 60,000 signal and 30,000 background events are expected. This large sample will enable an examination of the distortion of the recoil electron spectrum that is dominated by the neutrino flavor transformation in the dense solar matter, which will shed new light on the inconsistency between the measured electron spectra and the predictions of the standard three-flavor neutrino oscillation framework. If ?m_(21)~2= 4.8 × 10~(-5)(7.5 × 10~(-5)) eV~2, JUNO can provide evidence of neutrino oscillation in the Earth at approximately the 3σ(2 σ) level by measuring the non-zero signal rate variation with respect to the solar zenith angle.Moreover, JUNO can simultaneously measure ?m_(21)~2 using ~8B solar neutrinos to a precision of 20% or better, depending on the central value, and to sub-percent precision using reactor antineutrinos. A comparison of these two measurements from the same detector will help understand the current mild inconsistency between the value of ?m_(21)~2 reported by solar neutrino experiments and the KamLAND experiment.     

Coulomb breakup of 8B and the flux of 8B neutrinos from the Sun

A kinematically complete measurement was made of the Coulomb dissociation of ⁸B nuclei on a Pb target at 83 MeV/nucleon. The cross-section was measured at low relative energies in order to infer the astrophysical S-factor for the ⁷Be(p,γ)⁸B reaction. A first-order perturbation theory analysis of the reaction dynamics including E1, E2, and M1 transitions was employed to extract the E1 strength relevant to neutrino-producing reactions in the solar interior. By fitting the measured cross-section from E _rel = 130 keV to 400 keV, we find S ₁₇(0) = 17.8^+1.4 _-1.2 eV b. Semiclassical 1st-order perturbation theory and fully quantum-mechanical continuum-discretized coupled-channels analyses yield nearly identical results for the E1 strength relevant to solar-neutrino flux calculations, suggesting that theoretical reaction mechanism uncertainties need not limit the precision of Coulomb-breakup determinations of the ⁷Be(p,γ)⁸B S-factor. A recommended value of S ₁₇(0) based on a weighted average of this and other measurements is presented. This recommendation implies a revised value for the theoretical flux of ⁸B solar neutrinos, which is also given.-1 Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002 RID="a" ID="a"Present address: Kernfysisch Versneller Instituut, Zernikelaan 25, 9747 AA Groningen, The Netherlands; e-mail: davids@kvi.nl     

Interactions of the solar neutrinos with the deuterons

The beta decay of ³¹Cl has been studied with a silicon detector array and a HPGe detector at the IGISOL facility. Previously controversial proton peaks have been confirmed to belong to ³¹Cl and a new proton group with an energy of 762(14) keV has been found. Proton captures to this state at 6921(15) keV in ³¹S can have an effect on the reaction rate of ³⁰P(p,γ) in ONe novae. Gamma rays of 1249.1(14) keV and 2234.5(8) keV corresponding to the de-excitations of the first two excited states in ³¹S have been measured. No beta-delayed protons from the IAS have been observed.     

SN 1987 A: Correlations between the Maryland and Rome gravitational wave detector data and the Mont Blanc and Kamiokande neutrino detector data

Summary The author reports on the analysis of the data obtained with the detectors given in the title in the period 12h of February 22, 1987 to 6h of February 23, 1987, that includes the time of the ν observation with the Mont Blanc detector during SN 1987a. A very significant correlation has been observed among the data of the above detectors in a period of one or two hours which includes the time of the Mont Blanc 5ν observation. The correlation between the g.w. data and the Kamiokande data is found if a time of 7.8s is added to the Kamioka recorded time; this is very close to the time difference, 6.2s, between the IMB and Kamioka large ν bursts observed at ≈7h 35 min. To speed up publication, the proofs were not sent to the authors and were supervised by the Scientific Committee.     

pep neutrino detection by a lithium detector as a direct way to seek oscillations of solar neutrinos

The high sensitivity of a lithium detector to pep and ⁷Be neutrinos renders a radiochemical lithium detector a powerful tool for seeking solar-neutrino oscillations. The first phase of the lithium experiment with an apparatus involving 10 t of metallic lithium will allow collecting data within 1 yr of measurements to provide very definite information about a MSW SMA solution. The second phase with ten modules 10 t each will measure the semiannual variations of the signal, whereby the contributions of pep and ⁷Be lines will be weighted, which will give “smoking-gun” evidence for the “just-so” solution for large mixing angles and Δm ² about 10^?10–10^?9 eV². If both regions are not confirmed, the results of the lithium detector can be interpreted in favor of the MSW LMA solution.     

Solar neutrinos, the presolar abundance of helium and the solar metallicity

Summary The observational estimates of the presolar abundance of helium (Y _s) are reviewed and a lower value ofY _s ({-0.19 by mass fraction) is suggested to solve the solar-neutrino problem. With this reduced value ofY _s it is argued from the point of view of maintaining the luminosity of the Sun at its observed level that the metallicity requirement isZ _s{-0.013. Previous workers, while considering lowerY _s in the range of 0.15÷0.20, have assumedZ _s in the range of either 0.018÷0.020 or 0.001÷0.004. We suggest that forY _s=0.15÷0.20, one should rather considerZ _s=0.01÷0.02 in order to obtain a global solution that explains the observed modes of solar oscillation as well as the observed neutrino flux. This solution is quite interesting as we find that the real uncertainties in the determination of the solar metallicity arising from the diversity in existing models of the solar atmosphere suggestZ _s{-{0.018±0.005.

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Riassunto Si esaminano le stime di osservazione dell'abbondanza presolare di elio (Y _s) e si sugge risce un valore diY _s inferiore ({-0.19 in posizione di massa) per risolvere il problema dei neutrini solari. Con questo valore ridotto diY _s si deduce dal punto di vista di mantenere la luminosità del Sole al livello osservato che il requisito di metallicità èZ _s=0.013. Alcuni ricercatori in precedenza, considerando unY _s inferiore, nell'intervallo 0.15÷0.20, hanno ipotizzato cheZ _s si trovi nell'intervallo 0.018÷0.020 o 0.001÷0.004. Si suggerisce che perY _s=0.15÷0.20, si dovrebbe piuttosto considerareZ _s=0.01÷0.02 per ottenere una soluzione globale che spieghi i modi osservati di oscillazione solare cosí come il flusso di neutrini osservato. Questa soluzione è piuttosto interessante poiché si trova che le incertezze reali nella determinazione della metallicità solare che derivano dalla diversità in modelli esistenti dell'atmosfera solare suggeriscono cheZ _s{-0.018±0.005.

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Резюме Предлагается обзор оценок распространенности гелия на солнце (Y _s). Предполагается, что низшая величинаY _s ({-0.19 массовой доли) решает проблему солнечных нейтрино. Эта величинаY _s приводит к требованию металлических свойствZ _s{-0.013. В предыдущих работах, где рассматривалась меньшая величинаY _s в области 0.15÷0.020, предполагалось, чтоZ _s находится либо в области 0.018÷0.020, либо в области 0.001÷0.004. Мы предполагаем, что дляY _s=0.15÷0.20 следует принятьZ _s в областиZ _s=0.01÷0.02, чтобы получить глобальное решение, которое объясняет наблюдаемые моды солнечных осцилляций и наблюдаемый поток нейтрино. Это решение представляет интерес, т.к. мы получаем, что реальные неопределенности при определении металлических свойств солннца, обусловленные разбросом существующих модей солнечной атмосферы, предлагают, чтоZ _s{-0.18±0.005.

     

Precise measurement of the W-boson mass with the CDF II detector

We have measured the W-boson mass M(W) using data corresponding to 2.2 fb(-1) of integrated luminosity collected in pp collisions at sqrt[s] = 1.96 TeV with the CDF II detector at the Fermilab Tevatron collider. Samples consisting of 470,126 W → eν candidates and 624,708 W → μν candidates yield the measurement M(W) = 80,387 ± 12(stat.) ± 15(syst.) = 80,387 ± 19 MeV/c2. This is the most precise measurement of the W-boson mass to date and significantly exceeds the precision of all previous measurements combined.     

Higgs charged bosons and the problem of solar neutrinos

For a model with the SU(2)L×SU(2)_R×U(1)_{B−L} gauge group, the passage of neutrino flux through a substance is studied. It is shown that Higgs charged physical bosons can considerably change the potential of neutrino interaction with the solar substance. An analytical expression for the survival probability of left-handed electron neutrinos is derived in the two-flavor approximation. Yanka Kupala Grodno State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 32–37, January, 2000.     

First results of the observation of <Superscript>7</Superscript>Be solar neutrinos with the BOREXINO detector

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.     

The status of the study of solar CNO neutrinos in the Borexino experiment

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.