117 research outputs found
Galaxy Clustering Around Nearby Luminous Quasars
We examine the clustering of galaxies around a sample of 20 luminous low
redshift (z<0.30) quasars observed with the Wide Field Camera-2 on the Hubble
Space Telescope. The HST resolution makes possible galaxy identification
brighter than V=23.5 and as close as 2'' to the quasar. We find a significant
enhancement of galaxies within a projected separation of < 100 kpc/h of the
quasars. If we model the qso/galaxy correlation function as a power law with a
slope given by the galaxy/galaxy correlation function, we find that the ratio
of the qso/galaxy to galaxy/galaxy correlation functions is . The
galaxy counts within r<15 kpc/h of the quasars are too high for the density
profile to have an appreciable core radius ( > 100 kpc). Our results reinforce
the idea that low redshift quasars are located preferentially in groups of
10-20 galaxies rather than in rich clusters. We see no significant difference
in the clustering amplitudes derived from radio-loud and radio-quiet
subsamples.Comment: 16 pages, 3 figures (included), 2 tables, Apj in pres
How many sigmas is the solar neutrino effect?
The minimal standard electroweak model can be tested by allowing all the
solar neutrino fluxes, with undistorted energy spectra, to be free parameters
in fitting the measured solar neutrino event rates, subject only to the
condition that the total observed luminosity of the sun is produced by nuclear
fusion. The rates of the five experiments prior to SNO (chlorine, Kamiokande,
SAGE, GALLEX, Super-Kamiokande) cannot be fit by an arbitrary choice of
undistorted neutrino fluxes at the level of 2.5 sigma (formally 99% C.L.).
Considering just SNO and Super-Kamiokande, the discrepancy is at the 3.3 sigma
level(10^{-3} C.L.). If all six experiments are fit simultaneously, the formal
discrepancy increases to 4 sigma (7*10^{-5} C.L.). If the relative scaling in
temperature of the nuclear reactions that produce 7Be and 8B neutrinos is taken
into account, the formal discrepancy is at the 7.4 sigma level.Comment: 1 figure; related information at http://www.sns.ias.edu/~jn
The luminosity constraint on solar neutrino fluxes
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.Comment: related material at http://www.sns.ias.edu/~jn
The Central Temperature of the Sun can be Measured via the Be Solar Neutrino Line
A precise test of the theory of stellar evolution can be performed by
measuring the difference in average energy between the neutrino line produced
by electron capture in the solar interior and the corresponding
neutrino line produced in a terrestrial laboratory. The high temperatures in
the center of the sun broaden the line asymmetrically, FWHM = 1.6~keV, and
cause an average energy shift of 1.3~keV. The width of the Be neutrino line
should be taken into account in calculations of vacuum neutrino oscillations.Comment: RevTeX file, 9 pages. For hardcopy with figure, send to
[email protected]. Institute for Advanced Study number AST 93/4
Tests of electron flavor conservation with the Sudbury Neutrino Observatory
We analyze tests of electron flavor conservation that can be performed at the
Sudbury Neutrino Observatory (SNO). These tests, which utilize B solar
neutrinos interacting with deuterium, measure: 1) the shape of the recoil
electron spectrum in charged-current (CC) interactions (the CC spectrum shape);
and 2) the ratio of the number of charged current to neutral current (NC)
events (the CC/NC ratio). We determine standard model predictions for the CC
spectral shape and for the CC/NC ratio, together with realistic estimates of
their errors and the correlations between errors. We consider systematic
uncertainties in the standard neutrino spectrum and in the charged-current and
neutral current cross-sections, the SNO energy resolution and absolute energy
scale, and the SNO detection efficiencies. Assuming that either matter-enhanced
or vacuum neutrino oscillations solve the solar neutrino problems, we calculate
the confidence levels with which electron flavor non-conservation can be
detected using either the CC spectrum shape or the CC/NC ratio, or both. If the
SNO detector works as expected, the neutrino oscillation solutions that
best-fit the results of the four operating solar neutrino experiments can be
distinguished unambiguously from the standard predictions of electron flavor
conservation.Comment: 31 pages (RevTeX) + 10 figures (postscript). Requires epsfig.sty.
Gzipped figures also available at ftp://ftp.sns.ias.edu/pub/lisi/snopaper .
To appear in Phys. Rev.
Standard Neutrino Spectrum from B-8 Decay
We present a systematic evaluation of the shape of the neutrino energy
spectrum produced by beta-decay of B. We place special emphasis on
determining the range of uncertainties permitted by existing laboratory data
and theoretical ingredients (such as forbidden and radiative corrections). We
review and compare the available experimental data on the
BBe decay chain. We analyze the theoretical and
experimental uncertainties quantitatively. We give a numerical representation
of the best-fit (standard-model) neutrino spectrum, as well as two extreme
deviations from the standard spectrum that represent the total (experimental
and theoretical) effective deviations. Solar neutrino experiments
that are currently being developed will be able to measure the shape of the
B neutrino spectrum above about 5 MeV. An observed distortion of the B
solar neutrino spectrum outside the range given in the present work could be
considered as evidence, at an effective significance level greater than three
standard deviations, for physics beyond the standard electroweak model. We use
the most recent available experimental data on the Gamow--Teller strengths in
the system to calculate the B neutrino absorption cross section on
chlorine: ~cm (
errors). The chlorine cross section is also given as a function of the neutrino
energy. The B neutrino absorption cross section in gallium is cm ( errors).Comment: Revised version, to appear in Phys. Rev.
Neutrino afterglow from Gamma-Ray Bursts: ~10^{18} eV
We show that a significant fraction of the energy of a gamma-ray burst(GRB)
is probably converted to a burst of 10^{17}-10^{19} eV neutrinos and multiple
GeV gammas that follow the GRB by > 10 s . If, as previously suggested, GRB's
accelerate protons to ~10^{20} eV, then both the neutrinos and the gammas may
be detectable.Comment: Accepted ApJ; added sentence re: sterile neutrinos; related material
at http://www.sns.ias.edu/~jn
Correlations of Solar Neutrino Observables for SNO
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.Comment: Accepted Phys Rev D. Included new figure. Related material
http://www.sns.ias.edu/~jn
Gallium Solar Neutrino Experiments: Absorption Cross sections, Neutrino spectra, and Predicted Event Rates
Neutrino absorption cross sections for 71Ga are calculated for all solar
neutrino sources with standard energy spectra, and for laboratory sources of
51Cr and 37Ar; the calculations include, where appropriate, the thermal energy
of fusing solar ions and use improved nuclear and atomic data. The ratio, R, of
measured (in GALLEX and SAGE) to calculated 51Cr capture rate is R = 0.95 +/-
0.07 (exp)} + ^{+0.04}_{-0.03} (theory). Cross sections are also calculated for
specific neutrino energies chosen so that a spline fit determines accurately
the event rates in a gallium detector even if new physics changes the energy
spectrum of solar neutrinos. Theoretical uncertainties are estimated for cross
sections at specific energies and for standard neutrino energy spectra.
Standard energy spectra are presented for pp and CNO neutrino sources in the
appendices. Neutrino fluxes predicted by standard solar models, corrected for
diffusion, have been in the range 120 SNU to 141 SNU since 1968.Comment: 57 pages, ReVTeX file. Accepted for publication in Phys. Rev. C.
Viewgraphs and numerical tables of neutrino spectra and cross sections at
http://www.sns.ias.edu/~jn
Solar models and solar neutrino oscillations
We provide a summary of the current knowledge, theoretical and experimental,
of solar neutrino fluxes and of the masses and mixing angles that characterize
solar neutrino oscillations. We also summarize the principal reasons for doing
new solar neutrino experiments and what we think may be learned from the future
measurements.Comment: Submitted to the Neutrino Focus Issue of New Journal of Physics at
http://www.njp.or
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