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We describe the results of the GALLEX solar neutrino experiment after completion of the project. In particular, we summarize the results for GALLEX IV (12 solar runs) and for our 71As - spiking experiments. The integral GALLEX result for all 65 solar runs (GALLEX I–IV) is (78 ± 8) SNU (1σ). This is only slightly more than half of the expected rate. The significance of this deficit is assured. • directly by the results from our two 5Cr neutrino source experiments (at the 10% - level), and • indirectly by means of experiments in which 71Ge is generated within the target solution from beta-decaying 71As (at the percent level). GALLEX at Gran Sasso is now succeeded by Gallium Neutrino Observatory). The GNO status as of October 1998 is reported.

After 5.5 years of data taking, GALLEX ended its experimental phase. The solar neutrino production rate, 76.4 ± 8 SNU, represents about 55% of the predicted rate. The As tests prove, at the 1% level, the reliability of the technique and the detection of 51Cr neutrino, with the nominal efficiency (93.0±8%), control the response of the detector to neutrinos in the solar energy range.

The magnitude of heavy-ion beam loss at the relativistic heavy ion collider (RHIC) and the large hadron collider (LHC) due to Coulomb induced bound-electron{endash}positron production and to Coulomb dissociation of the nucleus is evaluated. With the nominal design parameters, the associated partial beam lifetime of RHIC (assuming four intersection regions) is calculated as 7.7 h and that of LHC (one intersection region) as 5.3 h. {copyright} {ital 1996 The American Physical Society.}

Since May 1991, the GALLEX experiment — installed in the Gran Sasso Underground Laboratory — is continuously monitoring the solar neutrino signal by measuring the 71 Ge production rate in a target of 30.3 tons of nat Ga. The measured signal 77.1 ± 8.5 (stat) +4.4 – 5.4 SNU (1 σ ) [1] is well below the Standard Solar Model (SSM) prediction: ⋍ 120–130 SNU. To exclude unknown systematic effects as responsible for the observed deficit, an experiment with a (62.5 ± 0.4) PBq 51 Cr neutrino source has been performed 2. , 3. . The ratio R=0.97 ± 0.11 between measured and expected Cr-produced 71 Ge demonstrates that the deficit cannot be ascribed to unknown experimental systematics. Although astrophysical reasons could still remain as a possible explanation of the “solar neutrino puzzle”, we recall that the GALLEX result, when considered together with the results of the other solar neutrino experiments, would allow to strongly constrain the neutrino masses and mixing angles in the framework of the MSW effect.

A derivation of screening effects in a moderately dense equilibrated plasma, based on the methods of finite temperature field theory, demonstrates the limits of validity of the ``weak screening`` form. Because the systematics of the theory make it possible to unambiguously separate off the leading order {ital e}{sup 3}, there can be no effects that cancel screening. The static nature of the equilibrium removes questions connected with use of time-response methods for a steady-state problem. The derived screening potential approaches the Debye-Huckel potential at large separations, but is cut off by quantum effects at short distances; the inherent violations of self-consistency in classical derivations of the Debye-Huckel potential are absent. Applied to the conditions of the Sun`s central region, screening corrections deviate only moderately from the classical, {similar_to}15%. The partial degeneracy of electrons also presents only small effects beyond those accounted for by the appropriate population factors. Given the weak role of screening, the effect of the corrections on solar neutrino fluxes is, therefore, seen to be small.

The cross section for the production of [ital e][sup +]-[ital e][sup [minus]] ([ital K] orbit) pairs by very-high-energy fully stripped heavy ions is calculated for large impact parameters, where perturbation theory is valid. To achieve accuracy a large range of angular momenta and energies is explicitly computed. The remaining high-angular-momentum and high-energy domain are included by means of a modified version of an asymptotic expansion devised by Hall [Phys. Rev. 45, 620 (1934); Rev. Mod. Phys. 8, 358 (1936)]. An approximation to the small-impact-parameter, nonperturbative contribution is taken from previous work to obtain a reliable estimate for the practically important Au[sup 79+] on Au[sup 79+] cross section.

Assuming the approximation of pair independence, the number of pairs produced by a classical, imperturbable electromagnetic source is shown to be described by a Poisson distribution. The perturbational calculation of pairs by colliding heavy-ion beams is treated by straightforward summation of the diagrammatically defined series. The extended calculation, in which all orders of interaction between colliding ions and the electron-positron system are included, is also demonstrated to result in a Poisson-number distribution. Applications to current heavy-ion colliders are made.

The GALLEX collaboration aims at the detection of solar neutrinos in a radiochemical experiment employing 30 tons of Gallium in form of concentrated aqueous Gallium-chloride solution. The detector is primarily sensitive to the otherwise inaccessible pp-neutrinos. Details of the experiment have been repeatedly described before [1-7]. Here we report the present status of implementation in the Laboratori Nazionali del Gran Sasso (Italy). So far, 12.2 tons of Gallium are at hand. The present status of development allows to start the first full scale run at the time when 30 tons of Gallium become available. This date is expected to be January, 1990.

We report the GALLEX solar neutrino results for the measuring period GALLEX III, the period from 12 October 1994-4 October 1995. Counting for these runs was completed on 29 March 1996. The GALLEX III result (14 runs) is [53.9 ± 10.6(stat.) ± 3.1 (syst.)] SNU (1σ). This is 15.8 SNU below but statistically compatible with the new combined result for GALLEX (I+II+III) (53 runs), which is [69.7 ± 6.7(stat.) −4.5 +3.9 (syst.)] SNU (1σ) or (69.7 −8.1 +7.8 ) SNU with errors quadratically added. We also give the preliminary result from our second 51 Cr-source experiment: the measured detector response is 83±10% of expectation. The combined result from both GALLEX 51 Cr-source experiments is 92±8% of expectation.

Calculations are presented to show how large a day-night effect would be seen in appropriately modified radiochemical detectors for the [Delta][ital m][sup 2], sin[sup 2]2[theta] regions allowed by the present gallium, [sup 37]Cl, and Kamiokande solar neutrino results.

The radiochemical GALLEX experiment, which has been measuring the solar neutrino flux since May 1991, has performed an investigation with an intense man-made 51 Cr neutrino source (61.9 ± 1.2 PBq). The source, produced via neutron irradiation of ≈ 36 kg of chromium enriched in 50 Cr, primarily emits 746 keV neutrinos. It was placed for a period of 3.5 months in the reentrant tube in the GALLEX tank, to expose the gallium chloride target to a known neutrino flux. This experiment provides the ratio, R , of the production rate of Cr-produced 71 Ge measured in these source exposures to the rate expected from the known source activity: R = 1.04 ± 0.12. This result not only constitutes the first observation of low-energy neutrinos from a terrestrial source, but also (a) provides an overall check of GALLEX, indicating that there are no significant experimental artifacts or unknown errors at the 10% level that are comparable to the 40% deficit in observed solar neutrino signal, and (b) directly demonstrates for the first time, using a man-made neutrino source, the validity of the basic principles of radiochemical methods used to detect rare events (at the level of 10 atoms or less). Because of the close similarity in neutrino energy spectra from 51 Cr and from the solar 7 Be branch, this source experiment also shows that the gallium detector is sensitive to 7 Be neutrinos with full efficiency.

The galliumchloride detector operated by the GALLEX-collaboration in the Gran Sasso Underground Laboratory responds primarily to pp-neutrinos. They are produced in the primary fusion reaction of hydrogen into deuterium and directly coupled to the solar luminosity. Standard Solar Models predict ca. 58% of the total signal expected in GALLEX (123-132 SNU) to be due to pp-neutrinos. The relative pp-neutrino dominance becomes even larger if the deficit of higher energy neutrinos (as observed in the Homestake- and Kamiokande experiments) is considered. During the first data taking period, 15 solar runs had been performed within the exposure period 14.5.1991 - 29.4.1992. The result, 81 {+-} 17 {+-} 9 SNU provided the first experimental evidence for pp-neutrinos from the Sun. At the same time, it confirmed the depression of higher energy neutrino fluxes relative to the model predictions. Here the authors report the results of 15 more solar neutrino runs, covering the period 19.8.92 - 13.10.93. They obtain 78 {+-} 13 {+-} 5 SNU. Evaluated together, the result for all 30 runs is 79 {+-} 10 {+-} 6 SNU. While the SNU rate of GALLEX I is well reproduced the statistical error has been reduced so substantially that a value of signal +2{sigma}more » is required to accommodate not only pp-and pep- but also the {sup 7}Be-neutrino induced {sup 71}Ge-production. Contrary, the fate of {sup 8}B-neutrinos has only little discernible effect on the GALLEX data. In conclusion, with the present errors GALLEX constitutes a 2.5 {sigma} problem for {sup 7}Be neutrinos within the frame of {open_quotes}astrophysical{close_quotes} solutions. Alternatively, the particle physics solution (MSW-effect) can consistently explain all available solar neutrino results, leading to a most probable mass scale with the muon-neutrino at approximately 3 meV (milli-eV). However, since the GALLEX result allows the presence of pp and pep neutrinos at full strength. the latter explanation of the data is not forced.« less

We report the solar neutrino results from the complete set of runs in the exposure period, GALLEX II, from 19 August 1992 - 23 June 1994. Counting for these runs was completed on 10 December 1994. The GALLEX II result (24 runs) is [75.2±9.7 (stat) −4.6+4.1 (syst)] SNU (1 σ). After three years of recording the solar neutrino flux with the GALLEX detector, the combined result from the 39 completed solar runs (GALLEX I+II) is [77.1±8.5 (stat) −5.4+4.4 (syst) SNU (1 σ) or 77.1 −10.1+9.6 SNU with errors combined in quadrature. The combined error (± 13%) has now approached a level where the limits on the derived contribution of 7Be neutrinos to the GALLEX signal confront the predictions of solar models.

Large-basis coupled-channel Dirac-equation calculations of bound-electron\char21{}positron pair production in relativistic heavy-ion collisions are presented. The relative importance of the enhancement of the coupled-channel calculations over corresponding calculations performed in perturbation theory is shown to decrease with increasing basis size, indicating a systematic reduction of this effect of nonperturbative enhancement with improving convergence of the calculations. The total nonperturbative enhancement of the cross section is shown to be about 7 b for ${\mathrm{Pb}}^{82+}$ on ${\mathrm{Pb}}^{82+}$ at the Brookhaven Relativistic Heavy-Ion Collider, only some 6% over perturbation theory.

Calculations are presented to determine what real time day-night effects would be observable at SNO, Super-Kamiokande, or Borexino for the [Delta][ital m][sup 2], sin[sup 2]2[theta] space allowed by the present gallium, [sup 37]Cl, and Kamiokande solar neutrino results. We show that the combination of possible day-night effects and the observation of overall neutrino detection rates in the upcoming experiments might allow discrimination between the allowed regions of mass and mixing parameters. Approximate analytical expressions for the real time MSW effect in the Earth are presented to clarify the nature of electron-neutrino regeneration as a function of path length through the Earth. We point out that even for the allowed small sin[sup 2]2[theta] MSW solution, it might be possible to detect a day-night effect for neutrino trajectories through the core of the Earth.

The first period (GALLEX I) of data taking in the GALLEX solar neutrino experiment has been completed. From 14 May 1991 to 29 April 1992, the experiment observed the solar neutrino flux using neutrino capture by 71 Ga to form 71 Ge. Counting ended on 2 November 1992. The final result from the 15 runs of this periodpis (81±17 [ stat .]±9 [ syst .]) SNU (1 σ ). The first 6 runs of GALLEX II recorded the neutrino signal from 19 August 1992 to 3 February 1993. The preliminary result for this period is (97±23 [ stat .]±7 [ syst .]) SNU (1 σ ). With counting data considered until 29 April 1993, the joint result for all 21 runs is (87±14 [ stat .]±7 [ syst .]) SNU (1 σ ). The present neutrino recording period GALLEX II is continuing with one solar exposure every four weeks.

International audience; We have measured the rate of production of $^{71}$Ge from $^{71}$Ga by solar neutrinos. The target consists of 30.3 t of gallium in the form of 8.13 M aqueous gallium chloride solution (101 t), shielded by $\approx$ 3300 m water equivalent of standard rock in the Gran Sasso Underground Laboratory (Italy). In nearly one year of operation, 14 measurements of the production rate of $^{71}$Ge were carried out to give, after corrections for side reactions and other backgrounds, an average value of 83$\pm$19 (stat.)$\pm$8 (syst.) SNU (l$\sigma$) due to solar neutrinos. This conclusion constitutes the first observation of solar pp neutrinos. Our result is consistent with the presence of the full pp neutrino flux expected according to the "standard solar model" together with a reduced flux of $^8$B+$^7$Be neutrinos as observed in the Homestake and Kamiokande experiments. Astrophysical reasons remain as a possible explanation of the solar neutrino problem. On the other hand, if the result is to be interpreted in terms of the MSW effect, it would fix neutrino masses and mixing angles within a very restricted range.

Previously reported large nonperturbative enhancements of bound-electron--positron pair production in heavy-ion reactions are shown to be extremely gauge dependent due to incompleteness of the basis set. Large-basis calculations for the Pb on Pb system put a probable upper limit of the order of 10 b on the correction to perturbative calculations of the [ital K]-orbit-electron--positron pair production at ultrarelativistic heavy-ion colliders such as RHIC; this is to be added to the perturbative value of about 115 b.

The GALLEX collaboration is performing an experiment for the detection of neutrinos coming principally from the p-p fusion reaction in the Sun, via the reaction ve +71Ga →71Ge + e-. The experiment is running in the Gran Sasso Underground Laboratory of INFN, using as a target 30.3 tons of gallium in the form of 8.13 molar aqueous GaCl3 solution. A report is given of the status of GALLEX after the end of the operations devoted to the removal from the solution of the cosmogenically formed Ge isotopes, completed in the middle of 1991. The experiment is now collecting data on solar neutrinos and the data analysis is in progress. Preliminary results concerning the first year of measurement are presented.

During beam crossing at RHIC, the Lorentz contracted Coulomb interaction between the heavy ions will excite internal modes of the nucleus. The subsequent decay of these modes is predominately via single or multiple nucleon emission. Changing the atomic mass Of the beam ion will eventually cause beam intensity loss at RHIC for the radius of the ion orbit is sensitive to changes of the ratio Z/A. While calculations for this beam loss mechanism have been made, it is now clear that these earlier theoretical studies underestimated the Coulomb dissociation loss rate for they appear to have included only a limited range of internal nuclear excitation energy. In this report we reexamine the question of Coulomb dissociation cross sections at RHIC by including internal excitation energies up to thousands of GeV. In addition, we utilize experimental photonuclear absorption cross sections when evaluating the dissociation cross section. Also, internal excitation of a nucleus in one beam wig result in both energy loss and transverse momentum change of an ion in the colliding beam. These recoil effects will be examined in detail to determine if there is an additional loss rate for ions out of the rf bucket or a non-negligible change inmore » the ion's betatron momentum.« less

The GALLEX result 83 ± 19 (stat.) ± 8 (syst.) SNU is two standard deviations below the predictions of stellar model calculations (124–132 SNU). To fit this result together with those of the chlorine and Kamiokande experiments requires severe stretching of solar models but does not rule out such a procedure, leaving the possibility of massless neutrinos. It clearly implies that the pp neutrinos have been detected. The Mikheyev-Smirnov-Wolfenstein (MSW) mechanism provides a good fit, and the GALLEX result fixes the Δm 2 and sin 2 2 θ parameters in two very confined ranges (around Δm 2 = 6 × 10 −6 eV 2 and sin 2 2 θ = 7 × 10 −3 and around Δm 2 = 8 × 10 −6 eV 2 and sin 2 2 θ = 0.6). Explanations of the solar neutrino problems based on the decay or magnetic interactions of neutrinos are disfavoured.

A radiochemical Gallium-Solar-Neutrino Detector has been set up at the Gran Sasso Underground Laboratory. All major installations are implemented and the target, 53.5 m3 of galliumchloride solution containing 30.3 tons of gallium, has been brought underground after removing cosmogenic Ge-isotopes through nitrogen purge. This final implementation status and the achieved parameters characterizing the experiment are described in this report. Full scale performance tests and optimalization of the operating conditions of the extraction system are presently under way.

A Comment on the Letter by J. N. Bahcall and H. A. Bethe, Phys. Rev. Lett. 65, 2233 (1990).

A nonresonant diffraction-model calculation is found adequate to describe the gross-structure behavior thus far observed in the $^{12}\mathrm{C}$ + $^{12}\mathrm{C}$ and $^{16}\mathrm{O}$ + $^{16}\mathrm{O}$ inelastic scattering excitation functions.

Calculations are presented for the reaction /sup 71/Ga(p,n) /sup 71/Ge at E/sub p/ = 35 MeV. Differential cross sections to the ground state and the 0.175- and 0.500-MeV states are estimated and compared with experimental results. It is shown that the 0/sup 0/ (p,n) cross section at E/sub p/ = 35 MeV is not directly proportional to the Gamow-Teller strength and thus the experimental results cannot be used to estimate the absorption of solar neutrinos.

It has been suggested that variations in the solar neutrino rate measured by the 37 Cl experiment that appear to be anti-correlated with the solar cycle phenomena could be explained in terms of an MSW mechanism by solar matter displacement. These matter displacements might be brought about by magnetic fields in the sun's convection zone. However, such inside displacements result in solar surface displacements. The observed limits of solar radius variations constrain the inside changes. Using these constraints together with calculations based on the MSW mechanism, we show that the corresponding neutrino rate variations are very much too small to explain any experimental observations.

A solar-neutrino experiment that uses /sup 7/1Ga as a detector can distinguish between broad classes of explanations for the discrepancy between prediction and observation in the /sup 3/7Cl experiment. A radiochemical experiment with the required amount of /sup 7/1Ga is feasible.

Calculations of neutrino regeneration phenomena in the Earth as well as transformation in the Sun are presented with relevant predictions for several existing and planned neutrino detection experiments. The validity of computational approximations in the solar case is appropriately investigated. Sensitivity of the calculated results to the solar model is noted. Transformation and regeneration phenomena are calculated to result from transmission through the Earth of neutrinos with E(MeV)/..delta..m/sup 2/(eV/sup 2/) in the vicinity of 10/sup 6/ to 10/sup 7/. As a result, large time-of-night and seasonal variations are predicted for various solar-neutrino experiments in this parameter range. Analogous effects are predicted for terrestrial cosmic-ray and accelerator experiments.

The isoscalar pairing-force Hamiltonian is studied first in the BCS-like approximation, including neutron-neutron, proton-proton, and neutron-proton interactions. Constraining $〈\stackrel{^}{N}〉$ and $〈{\stackrel{^}{T}}^{2}〉$, we find a class of BCS-like wave functions which give the same minimum energy; they differ in the expectation value of ${\stackrel{^}{T}}_{z}$, $\ensuremath{-}Tl~〈{\stackrel{^}{T}}_{z}〉l~T$. For the limit $〈{\stackrel{^}{T}}_{z}〉=T$, the minimum occurs at zero neutron-proton interaction. The residual interactions, those neglected by the BCS approximation, are treated by the quasiboson approximation. The spurious effects of number and isospin dispersion are identified. A procedure for explicitly displaying the number and isospin dependence of the energy is given, together with one for obtaining excited states with all possible isospins. Finally, as an example, the degenerate case is worked out, and agreement with the exact solution, including ground-state neutron-proton correlations, to the order considered, is demonstrated.

It is shown that the interference particle parameter, b/sub nu / (ML,EL'), appearing in the directional correlation of internal-conversion electrons, has the opposite sign from that given in the literature. It is also shown that in the high-energy limit, the directional-correlation pattern for conversion electrons is identical with that of the corresponding gamma rays. (auth)

Low-energy electric-monopole or $E0$ transitions ($\ensuremath{\Delta}\mathrm{I}=0$, no) proceed solely by internal conversion, with zero units of angular momentum transferred to the ejected electron. Single gamma-ray emission of this multipole order is strictly forbidden. Electricmonopole pair production is possible for transition energies greater than $2m{c}^{2}$.It is pointed out that (1) the electric-monopole mode of de-excitation is available between any two equal-parity states of the same spin, zero or otherwise, (2) in such cases, $E0$ internal conversion may compete favorably with the paralleling magneticdipole and electric-quadrupole transitions in heavy nuclei, and (3) monopole matrix elements may be particularly useful in the study of nuclear structure.The relative and absolute conversion properties of electricmonopole transitions have been calculated relativistically, including the effects of the finite nuclear size and bound-state atomic screening. These results have been used to analyze the available experimental data on the 2+\ensuremath{\rightarrow}2+ transitions in ${\mathrm{Hg}}^{198}$, ${\mathrm{Pt}}^{196}$, and ${\mathrm{Pt}}^{192}$, and to determine upper limits for the monopole matrix elements. These upper limits appear appreciably smaller than the values for the matrix elements of well-known monopole transitions of the 0+\ensuremath{\rightarrow}0+ type.The possible significance of these results is considered with reference to current nuclear models.

The effect of residual interactions on the Coulomb energy separation between analogue states is examined in the same spirit and accuracy with which residual interactions are handled in nuclear physics. A closed-form expression allows for simple calculational procedures. The dependence on the form of the residual interaction can then be easily explored. A specific calculation is made for the Ca isotopes; the effect of configuration mixing is studied.

It is shown that the finite nuclear size introduces additional nuclear matrix elements into the expression for the rate of internal-conversion-electron ejection which are distinctly different from that for gamma-ray emission of the same multipole order. To illustrate the effect of these new matrix elements, the correction to the $K$-conversion coefficient of magnetic-dipole transitions is calculated. It is shown that in cases where the gamma-ray matrix element is attenuated (e.g., $l$-forbidden $M1$ transitions and the $M1$ components in odd-$A$ rotational transitions), the new nuclear matrix elements may lead to appreciable deviations between the experimentally measured $K$-shell conversion coefficient and the theoretical calculations of Sliv. The conversion coefficients of other electric and magnetic transitions are also affected by the introduction of the new matrix elements, as well as angular-correlation measurements involving the conversion electrons.

A group of highly forbidden electric-dipole transitions in the heavy-element region are known to exhibit anomalous internal conversion. These transitions are close to or below the threshold for K conversion. Their L and M subshell conversions show anomalies which exhibit a definite pattern: LI and LII subshell conversion is enhanced relative to the corresponding “book” values, while LIII is approximately normal. This paper attempts to explain this pattern in terms of “penetration” nuclear matrix elements for internal conversion, which arise because of the penetration of the converting atomic electron within the nucleus. It is found that for E1 transitions there are two types of penetration matrix elements. One of these, ∝ j n · r v 2 Y 1 ∗ , gives an important contribution only to s 1 2 ↔ p 1 2 electron transitions. Such electron transitions are present in LI and LII conversion, but are absent in LIII conversion. Since calculations based on approximate nuclear models indicate that this matrix element is much larger than other penetration matrix elements, a ready qualitative explanation of the experimental results for the three L subshells is available. Similar results are expected for the M subshells, etc. Quantitative interpretation of the observed conversion anomalies evaluates the nuclear penetration matrix elements. These matrix elements contain information in addition to that contained in the gamma-ray matrix element.

A straightforward, purely single-particle analysis of the Coulomb energy shift in ${\mathrm{Sc}}^{41}$, ${\mathrm{Ca}}^{41}$ leads to an abnormally small radius for the ${f}_{\frac{7}{2}}$ valence neutron. Presented in this note is a correlational correction that may help to increase this radius. The calculation of this correction is stated in as general a fashion as is possible, and an estimate is made which leans heavily on a parametrization of the proton and neutron densities.

The conditions the experimentally observed spectral shape imposes on the degree of polarization of the beta particles from RaE (Bi/sup 210/) were investigated. The simplest formulation of the problem consistent with present experimental facts was assumed. (W.D.M.)

In the interaction regions of a relativistic heavy-ion collider, bare, highly charged nuclei pass at great velocities, oppositely moving similar nuclei. Each nucleus, then, sees strong, time varying electromagnetic fields, and it is not surprising that there is a large probability for electron-positron pair creation (a process evaluated many years ago). There is also a smaller probability that the electron of the pair is created, not in a continuum state, but in one of the bound orbits, the K or L or higher orbits, of the Coulomb field of the previously bare nuclei. This dressing is most unfortunate for a collider device, since the charge change leaves the nucleus in an orbit that is no longer appropriate for continuing circulation. This note evaluates the probability for such dressing, and also examines whether a subsequent sweep-off process can undo the first step with any sizeable likelihood. 3 references.

Large transformation and regeneration phenomena are calculated to result from transmission through the Earth of neutrinos whose E(MeV)/\ensuremath{\Delta}${m}^{2}$(${\mathrm{eV}}^{2}$) lie in the vicinity of ${10}^{6}$--${10}^{7}$. As a result large time-of-night and seasonal variations are predicted for solar neutrinos in this parameter range.