arXiv subjects
Publications and source records attributed to John N. Bahcall.
We show that solar neutrino experiments set an upper limit of 7.8% (7.3% including the recent KamLAND measurements) to the fraction of energy that the Sun produces via the CNO fusion cycle, which is an order of magnitude improvement upon the previous limit. New experiments are required to detect CNO neutrinos corresponding to the 1.5% of the solar luminosity that the standard solar model predicts is generated by the CNO cycle.
This article describes the unconventional and occassionally stormy birth and early history of the HST Snapshot Program.
I summarize in four slides the 40 years of development of the standard solar model that is used to predict solar neutrino fluxes and then describe the current uncertainties in the predictions. I next dispel the misconception that the p-p neutrino flux is determined by the solar luminosity and present a related formula that gives, in terms of the p-p and 7Be neutrino fluxes, the ratio of the rates of the two primary ways of terminating the p-p fusion chain. I will also attempt to explain why it took so long, about three and a half decades, to reach a consensus view that new physics is being learned from solar neutrino experiments. Finally, I close with a personal confession.
We present "Before and After" global oscillation solutions, as well as predicted "Before and After" values and ranges for ten future solar neutrino observables (for BOREXINO, KamLAND, SNO, and a generic p-p neutrino detector). We have performed global analyses using the full SNO day-night energy spectrum and, alternatively, just the SNO CC and NC rates and the day-night asymmetry.The ``Before'' case includes all solar neutrino data (and some theoretical improvements) available prior to April 20, 2002 and the ``After'' case includes, in addition, the new SNO data on the CC, NC, and day-night asymmetry. The LMA solution is the only currently allowed MSW oscillation solution at ~99% CL. The LOW solution is allowed only at more than 2.5 sigma, SMA at 3.7 sigma or 4.7 sigma (depending upon analysis strategy), and pure sterile oscillations at 4.7sigma. Small mixing angles are ``out''(pure sterile is ``way out''); MSW with large mixing angles is definitely ``in''. Vacuum oscillations are allowed at 3 sigma, but not a 2 sigma. Precise maximal mixing is excluded at 3.2 sigma for MSW solutions and at 2.8 sigma for vacuum solutions. Most of the predicted values for future observables for the BOREXINO, KamLAND, and future SNO measurements are changed only by minor amounts by the inclusion of the recent SNO data. In order to test the robustness of the allowed neutrino oscillation regions and the predictions for future observables, we have carried out calculations using a variety of strategies to analyze the SNO and other solar neutrino data.
The 8B solar neutrino flux inferred from a global analysis of solar neutrino experiments is within 11% (1 sigma) of the predicted standard solar model value if only active neutrinos exist, but could be as large as 1.7 times the standard prediction if sterile neutrinos exist. We show that the total 8B neutrino flux (active plus sterile neutrinos) can be determined experimentally to about 10% (1 sigma) by combining charged current measurements made with the KamLAND reactor experiment and with the SNO CC solar neutrino experiment, provided the LMA neutrino oscillation solution is correct and the simulated performance of KamLAND is valid. Including also SNO NC data, the sterile component of the 8B neutrino flux can be measured by this method to an accuracy of about 12% (1 sigma) of the standard solar model flux. Combining Super-Kamiokande and KamLAND measurements and assuming the oscillations occur only among active neutrinos, the 8B neutrino flux can be measured to 6% (1 sigma); the total flux can be measured to an accuracy of about 9%. The total 7Be solar neutrino flux can be determined to an accuracy of about 28% (1 sigma) by combining measurements made with the KamLAND, SNO, and gallium neutrino experiments. One can determine the total 7Be neutrino flux to a one sigma accuracy of about 11% or better by comparing data from the KamLAND experiment and the BOREXINO solar neutrino experiment provided both detectors work as expected. The pp neutrino flux can be determined to about 15% using data from the gallium, KamLAND, BOREXINO, and SNO experiments.
With the goal of identifying signatures that select specific neutrino oscillation parameters, we test the robustness of global oscillation solutions that fit all the available solar and reactor experimental data. We use three global analysis strategies previously applied by different authors and also determine the sensitivity of the oscillation solutions to the critical nuclear fusion cross section, S_{17}(0), for the production of 8B. The favored solutions are LMA, LOW, and VAC in order of g.o.f. The neutral current to charged current ratio for SNO is predicted to be 3.5 +- 0.6 (1 sigma), which is separated from the no-oscillation value of 1.0 by much more than the expected experimental error. The predicted range of the day-night difference in charged current rates is (8.2 +- 5.2)% and is strongly correlated with the day-night effect for neutrino-electron scattering. A measurement by SNO of either a NC to CC ratio > 3.3 or a day-night difference > 10%, would favor a small region of the currently allowed LMA neutrino parameter space. The global oscillation solutions predict a 7Be neutrino-electron scattering rate in BOREXINO and KamLAND in the range 0.66 +- 0.04 of the BP00 standard solar model rate, a prediction which can be used to test both the solar model and the neutrino oscillation theory. Only the LOW solution predicts a large day-night effect(< 42%) in BOREXINO and KamLAND. For the KamLAND reactor experiment, the LMA solution predicts 0.44 of the standard model rate; we evaluate 1 sigma and 3 sigma uncertainties and the first and second moments of the energy spectrum.
We show that the combined data from solar neutrino experiments and from the KamLAND reactor neutrino experiment can establish an upper limit on, or detect, potential CPT violation in the neutrino sector of order 10^{-20} GeV to 10^{-21} GeV.
A specific linear combination of the total solar neutrino fluxes must equal the measured solar photon luminosity if nuclear fusion reactions among light elements are responsible for solar energy generation. This luminosity constraint, previously used in a limited form in testing the no neutrino oscillation hypothesis, is derived in a generality that includes all of the relevant solar neutrino fluxes and which is suitable for analyzing the results of many different solar neutrino experiments. With or without allowing for neutrino oscillations, the generalized luminosity constraint can be used in future analyses of solar neutrino data. Accurate numerical values for the linear coefficients are provided.
For active and sterile neutrinos, we present the globally allowed solutions for two neutrino oscillations. We include the SNO CC measurement and all other relevant solar neutrino and reactor data. Five active neutrino oscillation solutions (LMA, LOW, SMA, VAC, and Just So2) are currently allowed at 3 sigma; three sterile neutrino solutions (Just So2, SMA, and VAC) are allowed at 3 sigma. The goodness of fit is satisfactory for all eight solutions. We also investigate the robustness of the allowed solutions by carrying out global analyses with and without: 1) imposing solar model constraints on the 8B neutrino flux, 2) including the Super-Kamiokande spectral energy distribution and day-night data, 3) including a continuous mixture of active and sterile neutrinos, 4) using an enhanced CC cross section for deuterium (due to radiative corrections), and 5) a optimistic, hypothetical reduction by a factor of three of the error of the SNO CC rate. For every analysis strategy used in this paper, the most favored solutions all involve large mixing angles: LMA, LOW, or VAC. The favored solutions are robust, but the presence at 3 sigma of individual sterile solutions and the active Just So2 solution is sensitive to the analysis assumptions.
I discuss why we need solar neutrino experiments below 1 MeV. I also express my prejudices about the desired number and types of such experiments, emphasizing the importance of p-p solar neutrino experiments
We present a global analysis of all the available solar neutrino data treating consistently the 8B and hep neutrino fluxes as free parameters. The analysis reveals at 99.7% C.L. eight currently-allowed discrete regions in two-neutrino oscillation space, five regions corresponding to active neutrinos and three corresponding to sterile neutrinos. Most of the allowed solutions are robust with respect to changes in the analysis procedure, but the traditional vacuum solution is fragile. The globally-permitted range of the 8B neutrino flux, 0.45 to 1.95 in units of the BP2000 flux, is comparable to the 3 sigma range allowed by the standard solar model. We discuss the implications for SNO of a low mass, Delta m^2 ~ 6 times 10^{-12} eV^2, vacuum oscillation solution, previously found by Raghavan, and by Krastev and Petcov, but absent in recent analyses that included Super-Kamiokande data. For the SNO experiment, we present refined predictions for the charged-current rate and the ratio of the neutral-current rate to charged-current rate. The predicted charged-current rate can be clearly distinguished from the no-oscillation rate only for the LMA solution. The predicted ratio of the neutral-current rate to charged-current rate is distinguishable from the no-oscillation ratio for the LMA, SMA, LOW, and VAC solutions for active neutrinos.
We calculate accurate solar models and report the detailed time dependences of important solar quantities. We use helioseismology to constrain the luminosity evolution of the sun and report the discovery of semi-convection in evolved solar models that include diffusion. In addition, we compare the computed sound speeds with the results of p-mode observations by BiSON, GOLF, GONG, LOWL, and MDI instruments. We contrast the neutrino predictions from a set of eight standard-like solar models and four deviant (or deficient) solar models with the results of solar neutrino experiments. For solar neutrino and for helioseismological applications, we present present-epoch numerical tabulations of characteristics of the standard solar model as a function of solar radius, including the principal physical and composition variables, sound speeds, neutrino fluxes, and functions needed for calculating solar neutrino oscillations.
We study a sample of about 1400 disk M dwarfs that are found in 148 fields observed with the Wide Field Camera 2 (WFC2) on the Hubble Space Telescope and 162 fields observed with pre-repair Planetary Camera 1 (PC1), of which 95 of the WFC2 fields are newly analyzed. The method of maximum likelihood is applied to derive the luminosity function and the Galactic disk parameters. At first, we use a local color-magnitude relation and a locally determined mass-luminosity relation in our analysis. The results are consistent with those of previous work but with considerably reduced statistical errors. These small statistical errors motivate us to investigate the systematic uncertainties. Considering the metallicity gradient above the Galactic plane, we introduce a modified color-magnitude relation that is a function of Galactic height. The resultant M dwarf luminosity function has a shape similar to that derived using the local color-magnitude relation but with a higher peak value. The peak occurs at $M_V \sim 12$ and the luminosity function drops sharply toward $M_V \sim 14$. We then apply a height-dependent mass-luminosity function interpolated from theoretical models with different metallicities to calculate the mass function. Unlike the mass function obtained using local relations, which has a power-law index $α= 0.47$, the one derived from the height-dependent relations tends to be flat ($α= -0.10$). The resultant local surface density of disk M dwarfs (12.2 +/- 1.6 M_sun pc^{-2}) is somewhat smaller than the one obtained using local relations (14.3 +/- 1.3 M_sun pc^{-2}). Our measurement favors a short disk scale length, H = 2.75 +/- 0.16 (statistical) +/- 0.25 (systematic) kpc.
This historical essay describes the struggle to understand how the sun shines. The story begins with the disagreement between Kelvin and Darwin over the age of the sun in the middle of the 19th century and continues through the revelations of solar neutrino experiments at the conclusion of the 20th century.
Neutrino oscillation scenarios predict correlations, and zones of avoidance, among measurable quantities such as spectral energy distortions, total fluxes, time dependences, and flavor content. The comparison of observed and predicted correlations will enhance the diagnostic power of solar neutrino experiments. A general test of all presently-allowed (two neutrino) oscillation solutions is that future measurements must yield values outside the predicted zones of avoidance. To illustrate the discriminatory power of the simultaneous analysis of multiple observables, we map currently allowed regions of neutrino masses and mixing angles onto planes of quantities measurable with the Sudbury Neutrino Observatory (SNO). We calculate the correlations that are predicted by vacuum and MSW (active and sterile) neutrino oscillation solutions that are globally consistent with all available neutrino data. We derive approximate analytic expressions for the dependence of individual observables and specific correlations upon neutrino oscillations parameters. We also discuss the prospects for identifying the correct oscillation solution using multiple SNO observables.
We review five different derivations that demonstrate that the Salpeter formula for the plasma corrections to fusion rates is valid at the center of the sun with insignificant errors (~ percent). We point out errors in several recent papers that have obtained a variety of answers, some even with the wrong sign or the wrong functional dependence.
I summarize the first four decades of solar neutrino research and suggest what may be possible to learn with extragalactic neutrinos and with solar neutrinos in the next decade.
A gamma-ray burst fireball is likely to contain an admixture of neutrons, in addition to protons, in essentially all progenitor scenarios. Inelastic collisions between differentially streaming protons and neutrons in the fireball produce muon neutrinos (antineutrinos) of ~ 10 GeV as well as electron neutrinos (antineutrinos) of ~ 5 GeV, which could produce ~ 7 events/year in kilometer cube detectors, if the neutron abundance is comparable to that of protons. Photons of ~ 10 GeV from pi-zero decay and ~ 100 MeV electron antineutrinos from neutron decay are also produced, but will be difficult to detect. Photons with energies < 1 MeV from shocks following neutron decay produce a characteristic signal which may be distinguishable from the proton-related MeV photons.