Solar Neutrino Capture Rate Research Articles

Estimated solar-neutrino capture rates of 131Xe: implications for multi-tonne Xe-based experiments

Various large-scale experiments for double beta decay or dark matter are based on xenon. Current experiments are on the tonne scale, but future ideas also aim for even larger sizes. Here we study the potential of the isotope 131Xe to allow real-time capture measurements of solar pp-chain neutrinos, besides classical neutrino-electron scattering. Here we use improved nuclear-structure calculations to determine the cross sections of solar neutrinos on 131Xe. Our updated capture-rate estimate is (80 ± 22) SNU, with neutrino survival probabilities taken into account. According to our calculations, the 8B neutrinos are the dominant contribution to the total capture rate. Due to our more accurate treatment of the phase-space factor the computed capture rate, (60 ± 19) SNU, is significantly larger than what was expected based on previous calculations. This improves considerably the prospects of real-time monitoring of pp-chain neutrinos for long periods of time.

Calculated solar-neutrino capture rate for a radiochemical Tl205 -based solar-neutrino detector

Radiochemical experiments for low-energy solar-neutrino detection have been making headlines by exploiting the isotopes \iso{Cl}{37} and \iso{Ga}{71}. Such a very low-threshold measurement of this type can also be performed using \iso{Tl}{205}, which has been considered for decades for this purpose. A unique feature of this detector nucleus is the integration is the solar-neutrino flux over millions of years owing to its long-living daughter \iso{Pb}{205}. In this study we have calculated for the first time the cross section for the charged-current solar-neutrino scattering off \iso{Tl}{205}. Taking into account the solar-model-predicted neutrino fluxes and the electron-neutrino survival probabilities, a solar-neutrino capture rate of 62.2 $\pm 8.6$ SNU is determined, a value significantly smaller than in previous estimates.

Erratum: Precision evaluation of the Ga71(νe,e−) solar neutrino capture rate from the ( He3,t ) charge-exchange reaction [Phys. Rev. C 91 , 034608 (2015)

Erratum: Precision evaluation of the Ga71(νe,e−) solar neutrino capture rate from the ( He3,t ) charge-exchange reaction [Phys. Rev. C 91 , 034608 (2015)

High energy-resolution measurement of theSe82(He3,t)Br82reaction for double-βdecay and for solar neutrinos

A high-resolution ($^{3}\mathrm{He},t$) charge-exchange experiment at an incident energy of 420 MeV has been performed on the double beta ($\ensuremath{\beta}\ensuremath{\beta}$) decay nucleus $^{82}\mathrm{Se}$. A detailed Gamow-Teller (${\mathrm{GT}}^{\ensuremath{-}}$) strength distribution in $^{82}\mathrm{Br}$ has been extracted, which provides information to the $\ensuremath{\beta}\ensuremath{\beta}$-decay nuclear matrix elements. Three strong and isolated transitions, which are to the 75, 1484 and the 2087 keV states in $^{82}\mathrm{Br}$, are found to dominate the low-excitation region below $\ensuremath{\approx}2.1$ MeV. Above 2.1 MeV a sudden onset of a strong GT fragmentation is observed. The degree of fragmentation resembles a situation found in the neighboring $A=76$ system $^{76}\mathrm{Ge}$, whereas the observed concentration of strength in the three low-lying states is reminiscent of the heavier neighbors $^{96}\mathrm{Zr}$ and $^{100}\mathrm{Mo}$. The strong GT transition to the 75 keV $({1}^{+})$ state makes $^{82}\mathrm{Se}$ interesting for solar neutrino detection. The $^{82}\mathrm{Se}({\ensuremath{\nu}}_{e},{e}^{\ensuremath{-}})^{82}\mathrm{Br}$ solar neutrino capture rate in a nonoscillation scenario is therefore evaluated to $668\ifmmode\pm\else\textpm\fi{}12\text{(stat)}\ifmmode\pm\else\textpm\fi{}60\text{(sys)}$ SNU, and some of the advantages of using selenium for solar neutrino studies are discussed.

Precision [formula omitted]–[formula omitted] mass-difference measurement

The Ga71(νe,e−)Ge71 reaction Q value has been measured with the JYFLTRAP mass spectrometer at the IGISOL facility of the University of Jyväskylä to Q=232.443(93)keV. This value agrees with previous measurements, though it features a much higher accuracy. The Q value is being discussed in the context of the solar neutrino capture rate in Ga71.

Precision evaluation of theGa71(νe,e−)solar neutrino capture rate from the(He3,t)charge-exchange reaction

A high-resolution measurement of the ${}^{71}$Ga(${}^{3}$He,$t$)${}^{71}$Ge charge-exchange reaction extracts the Gamow-Teller strength distribution in ${}^{71}$Ge and allows a precision evaluation of the expected solar-neutrino capture rate, assuming a non-oscillation scenario. The new measurements can be used as a benchmark for comparing to neutrino capture rates in the presence of oscillations. With the new results, the dominant statistical uncertainty of the ${}^{71}$Ga capture rate lies now in the solar fluxes from the CNO cycle.

Charged current neutrino cross section for solar neutrinos, and background toββ(0ν) experiments

Solar neutrinos can interact with the source isotope in neutrinoless double-$\ensuremath{\beta}$-decay experiments through charged-current and neutral-current interactions. The charged-current product nucleus will then $\ensuremath{\beta}$ decay with a $Q$ value larger than the double-$\ensuremath{\beta}$-decay $Q$ value. As a result, this process can populate the region of interest and be a background to the double-$\ensuremath{\beta}$-decay signal. We estimate the solar neutrino capture rates on three commonly used double-$\ensuremath{\beta}$-decay isotopes, ${}^{76}$Ge, ${}^{130}$Te, and ${}^{136}$Xe. We then use the decay scheme of each product nucleus to estimate the possible background rates in those materials. As half-life sensitivities in future experiments approach $1\ifmmode\times\else\texttimes\fi{}{10}^{28}$ yr, this background will have to be considered although its rate will depend on detector design in addition to nuclear structure.

Measurement of the solar neutrino capture rate with gallium metal. III. Results for the 2002–2007 data-taking period

The Russian-American experiment SAGE began to measure the solar neutrino capture rate with a target of gallium metal in December 1989. Measurements have continued with only a few brief interruptions since that time. In this article we present the experimental improvements in SAGE since its last published data summary in December 2001. Assuming the solar neutrino production rate was constant during the period of data collection, combined analysis of 168 extractions through December 2007 gives a capture rate of solar neutrinos with energy more than 233 keV of $65.{4}_{\ensuremath{-}3.0}^{+3.1}$ (stat) ${}_{\ensuremath{-}2.8}^{+2.6}$ (syst) SNU. The weighted average of the results of all three Ga solar neutrino experiments, SAGE, Gallex, and GNO, is now $66.1\ifmmode\pm\else\textpm\fi{}3.1$ SNU, where statistical and systematic uncertainties have been combined in quadrature. During the recent period of data collection a new test of SAGE was made with a reactor-produced $^{37}\mathrm{Ar}$ neutrino source. The ratio of observed to calculated rates in this experiment, combined with the measured rates in the three prior $^{51}\mathrm{Cr}$ neutrino-source experiments with Ga, is $0.87\ifmmode\pm\else\textpm\fi{}0.05$. A probable explanation for this low result is that the cross section for neutrino capture by the two lowest-lying excited states in $^{71}\mathrm{Ge}$ has been overestimated. If we assume these cross sections are zero, then the standard solar model including neutrino oscillations predicts a total capture rate in Ga in the range of 63 SNU to 66 SNU with an uncertainty of about 4%, in good agreement with experiment. We derive the current value of the neutrino flux produced in the Sun by the proton-proton fusion reaction to be ${\ensuremath{\phi}}_{\mathit{pp}}^{\ensuremath{\bigodot}}=(6.0\ifmmode\pm\else\textpm\fi{}0.8)\ifmmode\times\else\texttimes\fi{}{10}^{10}/({\mathrm{cm}}^{2} \mathrm{s})$, which agrees well with the $\mathit{pp}$ flux predicted by the standard solar model. Finally, we make several tests and show that the data are consistent with the assumption that the solar neutrino production rate is constant in time.

The BNO–LNGS joint measurement of the solar neutrino capture rate in 71Ga

We describe a cooperative measurement of the capture rate of solar neutrinos by the reaction 71Ga( ν e, e −) 71Ge. Extractions were made from a portion of the gallium target in the Russian–American Gallium Experiment SAGE and the extraction samples were transported to the Gran Sasso laboratory for synthesis and counting at the Gallium Neutrino Observatory (GNO). Six extractions of this type were made and the resultant solar neutrino capture rate was 64 - 22 + 24 SNU, which agrees well with the overall result of the gallium experiments. The major purpose of this experiment was to make it possible for SAGE to continue their regular schedule of monthly solar neutrino extractions without interruption while a separate experiment was underway to measure the response of 71Ga to neutrinos from an 37Ar source. As side benefits, this experiment proved the feasibility of long-distance sample transport in ultralow background radiochemical experiments and familiarized each group with the methods and techniques of the other.

Measurement of the solar neutrino capture rate in SAGE and the value of the pp–neutrino flux at the earth

Measurement of the solar neutrino capture rate in SAGE and the value of the pp–neutrino flux at the earth

Search for time modulations in the Gallex/GNO solar neutrino data

The final data of the Gallex and GNO radiochemical experiments have been searched for possible time modulations of the solar neutrino capture rate using the Lomb–Scargle periodogram and the maximum likelihood methods. Both analyses, performed using the raw data, do not support the presence of a time variability with characteristic periods resembling those of rotation of the solar magnetic fields, as previously suggested in the literature by some authors. In this context, the potential sensitivity of the Lomb–Scargle method to radiochemical 71Ga data has also been explored with simulated data. This allowed to set an exclusion plot in the frequency/amplitude plane from the Gallex–GNO dataset.

Measurement of the solar neutrino capture rate in Sage

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).

Solar neutrino results and present status

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.

Solar neutrino flux measurements by the Soviet-American gallium experiment (SAGE) for half the 22-year solar cycle

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.

Bulk GaAs as a solar neutrino detector

A GaAs detector may offer the unique possibility to independently study neutrino properties and solar physics. The ability to measure the flux of p–p, 7Be and pep solar neutrinos would allow one to approach a solution of the “solar neutrino problem”, i.e. the explanation of the significant deficit in observed capture rate of solar neutrinos. A large GaAs solar neutrino detector would allow to measure parameters for possible Mikheyev–Smirnov–Wolfenstein neutrino oscillations with unprecedented precision. A model-independent test for sterile neutrinos is also possible. A direct measurement of the temperature profile of the Sun center appears feasible. A GaAs detector would also provide the ability to observe neutral current interactions in addition to addressing a wide range of other interesting physics. In order to measure the p–p, pep and 7Be neutrinos a detector is required with low threshold (< 350 keV), good energy resolution (< 2 keV) and low background. A GaAs solid-state detector could meet the listed requirements. A large GaAs detector would be composed of approximately 40,000 intrinsic GaAs crystals, each weighting 3.2 kg. Such a detector would have a mass of 125 ton and would contain 60 ton of Ga occupying a volume of roughly 3 m on one side. Previous efforts by many groups have resulted in producing very small detectors with reasonably good resolution. However, it has thus far proved impossible to make large detectors with good resolution. Thus, a solar neutrino detector such as the one described above is obviously very ambitious, but the scientific motivation is sufficiently high that we have begun a research and development program with the goal of determining the technical feasibility of constructing large GaAs crystals with the requisite electronic properties to serve as particle detectors.

Measurement of the Solar Neutrino Capture Rate by SAGE and Implications for Neutrino Oscillations in Vacuum

The Russian-American solar neutrino experiment has measured the capture rate of neutrinos on metallic gallium in a radiochemical experiment at the Baksan Neutrino Observatory. Eight years of measurement give the result 67.2 (+7.2,-7.0) (+3.5,-3.0) solar neutrino units, where the uncertainties are statistical and systematic, respectively. The restrictions these results impose on vacuum neutrino oscillation parameters are given.

Measurement of the solar neutrino capture rate with gallium metal

The solar neutrino capture rate measured by the Russian-American Gallium Experiment (SAGE) on metallic gallium during the period January 1990 through December 1997 is 67.2 (+7.2-7.0) (+3.5-3.0) SNU, where the uncertainties are statistical and systematic, respectively. This represents only about half of the predicted Standard Solar Model rate of 129 SNU. All the experimental procedures, including extraction of germanium from gallium, counting of 71Ge, and data analysis are discussed in detail.

On the Solar‐Cycle Modulation of the Homestake Solar Neutrino Capture Rate and the Shuffle Test

There exists no significant correlation between the Homestake neutrino data up to run 133 and the monthly sunspot number, according to a test that is based on certain optimality properties for this type of problem. It is argued that priorly reported highly significant results for segments of the data are due to a statistical fallacy: the usual methods for evaluating the significance of common tests for correlation are not applicable in the sunspot-neutrino context. Moreover, an appropriate evaluation of these tests gives results that are compatible with the hypothesis of no correlation. Some new methods are introduced for assessing the significance of common measures of correlation in a time series setting, with a special emphasis on the Spearman rank correlation coefficient.

Flicker-Noise in Processes of Solar Activity

The time series describing the solar activity variations in the diverse solar layers are analyzed in terms of the developed method of the flicker-noise diagnostic which allows one to extract the dynamic characteristics of the process under study. The revealed results allow us to conclude that in all studied solar processes short term variations of the observational variables (with typical time less than ~3 years) reflect the behavior of some global dynamics. The dynamic characteristics turned out to be similar for the processes which are observed at the level of the solar photosphere and gradually changes in the solar atmosphere. That is why all Sun layers can be considered as a single dynamic system. We find that the short term variations of the solar neutrino capture rate are not random but are caused by some dynamic process. The analysis of solar total irradiance time series in terms of the applied method allows us to suggest that the mentioned dynamic processes exists in the solar core.

Effect of nuclear deformations on Solar neutrino capture rates

Modification of the nuclear matrix elements for transitions between the ground state of a nucleus and accessible excited states of the nucleus formed by neutrino capture on the original nucleus are calculated on the basis of a deformed shell model where the initial and/or final nuclei involved may be deformed. It is shown that as long as there are different deformations in the initial and final nuclear states, the beta transition rates may be reduced by factors of two to three from the values they would have if there were no deformations. These considerations are applied to calculate neutrino capture rates in and in .