Search

International audience; The Ultracold Neutron Asymmetry (UCNA) experiment was designed to measure the β-decay asymmetry parameter, A0, for free neutron decay. In the experiment, polarized ultracold neutrons are transported into a decay trap, and their β-decay electrons are detected with ≈4π acceptance into two detector packages which provide position and energy reconstruction. The experiment also has sensitivity to bn, the Fierz interference term in the neutron β-decay rate. In this work, we determine bn from the energy dependence of A0 using the data taken during the UCNA 2011–2013 run. In addition, we present the same type of analysis using the earlier 2010 A dataset. Motivated by improved statistics and comparable systematic errors compared to the 2010 data-taking run, we present a new bn measurement using the weighted average of our asymmetry dataset fits, to obtain bn=0.066±0.041stat±0.024syst which corresponds to a limit of −0.012

EPJ Web of Conferences, 219, ISSN:2100-014X, ISSN:2101-6275, International Workshop on Particle Physics at Neutron Sources (PPNS 2018), Grenoble, France, May 24–26, 2018, ISBN:978-2-7598-9082-8

It has been proposed recently that a previously unobserved neutron decay branch to a dark matter particle (χ) could account for the discrepancy in the neutron lifetime observed in experiments that use two different measurement techniques. One of the possible final states discussed includes a single χ along with an e^+e^− pair. We use data from the UCNA (Ultracold Neutron Asymmetry) experiment to set limits on this decay channel. Coincident electron-like events are detected with ∼4π acceptance using a pair of detectors that observe a volume of stored Ultracold Neutrons (UCNs). The summed kinetic energy (E_(e^+e^−)) from such events is used to set limits, as a function of the χ mass, on the branching fraction for this decay channel. For χ masses consistent with resolving the neutron lifetime discrepancy, we exclude this as the dominant dark matter decay channel at ≫ 5σlevel for 100 keV < E_(e^+e^−) < 644 keV. If the χ + e^+e^− final state is not the only one, we set limits on its branching fraction of 90% confidence level.

Background: The neutron β-decay asymmetry parameter A_0 defines the angular correlation between the spin of the neutron and the momentum of the emitted electron. Values for A_0 permit an extraction of the ratio of the weak axial-vector to vector coupling constants, λ≡gA/gV, which under assumption of the conserved vector current hypothesis (gV=1) determines gA. Precise values for gA are important as a benchmark for lattice QCD calculations and as a test of the standard model. Purpose: The UCNA experiment, carried out at the Ultracold Neutron (UCN) source at the Los Alamos Neutron Science Center, was the first measurement of any neutron β-decay angular correlation performed with UCN. This article reports the most precise result for A_0 obtained to date from the UCNA experiment, as a result of higher statistics and reduced key systematic uncertainties, including from the neutron polarization and the characterization of the electron detector response. Methods: UCN produced via the downscattering of moderated spallation neutrons in a solid deuterium crystal were polarized via transport through a 7 T polarizing magnet and a spin flipper, which permitted selection of either spin state. The UCN were then contained within a 3-m long cylindrical decay volume, situated along the central axis of a superconducting 1 T solenoidal spectrometer. With the neutron spins then oriented parallel or anti-parallel to the solenoidal field, an asymmetry in the numbers of emitted decay electrons detected in two electron detector packages located on both ends of the spectrometer permitted an extraction of A_0. Results: The UCNA experiment reports a new 0.67% precision result for A_0 of A_0=−0.12054(44)_(stat)(68)_(syst), which yields λ=gA/gV=−1.2783(22). Combination with the previous UCNA result and accounting for correlated systematic uncertainties produces A0=−0.12015(34)stat(63)syst and λ=gA/gV=−1.2772(20). Conclusions: This new result for A0 and gA/gV from the UCNA experiment has provided confirmation of the shift in values for gA/gV that has emerged in the published results from more recent experiments, which are in striking disagreement with the results from older experiments. Individual systematic corrections to the asymmetries in older experiments (published prior to 2002) were >10%, whereas those in the more recent ones (published after 2002) have been of the scale of

In January, 2018, Fornal and Grinstein proposed that a previously unobserved neutron decay branch to a dark matter particle (χ) could account for the discrepancy in the neutron lifetime observed in two different types of experiments. One of the possible final states discussed includes a single χ along with an e+e− pair. We use data from the UCNA (Ultracold Neutron Asymmetry) experiment to set limits on this decay channel. Coincident electron-like events are detected with ∼ 4π acceptance using a pair of detectors that observe a volume of stored Ultracold Neutrons (UCNs). We use the timing information of coincidence events to select candidate dark sector particle decays by applying a timing calibration and selecting events within a physically-forbidden timing region for conventional n → p + e- + ν̅e decays. The summed kinetic energy (Ee+e−) from such events is reconstructed and used to set limits, as a function of the χ mass, on the branching fraction for this decay channel.

Data from the Sudbury Neutrino Observatory have been used to constrain the lifetime for nucleon decay to ``invisible'' modes, such as n -> 3 nu. The analysis was based on a search for gamma-rays from the de-excitation of the residual nucleus that would result from the disappearance of either a proton or neutron from O16. A limit of tau_inv > 2 x 10^{29} years is obtained at 90% confidence for either neutron or proton decay modes. This is about an order of magnitude more stringent than previous constraints on invisible proton decay modes and 400 times more stringent than similar neutron modes., Update includes missing efficiency factor (limits change by factor of 2) Submitted to Physical Review Letters

We describe a simple drift tube counter that has been used as a cosmic ray veto for the UCNA experiment, a first-ever measurement of the neutron beta-asymmetry using ultra-cold neutrons. These detectors provide an inexpensive alternative to more conventional scintillation detectors for large area cosmic ray anticoincidence detectors.

A radiochemical 71 Ga- 71 Ge experiment to determine the primary flux of neutrinos from the Sun began measurements of the solar neutrino flux at the Baksan Neutrino Observatory in 1990. The number of 71 Ge atoms extracted from 30 tons of gallium in 1990 and from 57 tons of gallium in 1991 was measured in 12 runs during the period of January 1990 to December 1991. The combined 1990 and 1991 data-sets give a value of 58 + 17/ —24 (stat) ± 14 (syst) SNU. This is to be compared with 132 + 7/ —5 SNU predicted by the Standard Solar Model.

The earlier search at HERMES for narrow baryon states excited in quasireal photoproduction, decaying through the channel pK(S)(0) -> p pi(+)pi(-), has been extended with improved decay-particle reconstruction, more advanced particle identification, and increased event samples. The structure observed earlier at an invariant mass of 1528 MeV shifts to 1522 MeV and the statistical significance drops to about 2 sigma for data taken with a deuterium target. The number of events above background is 68(-31)(+98)(stat) +/- 13(sys). No such structure is observed in the hydrogen data set.

Ultra-cold neutrons (UCN), neutrons with energies low enough to be confined by the Fermi potential in material bottles, are playing an increasing role in measurements of fundamental properties of the neutron. The ability to manipulate UCN with material guides and bottles, magnetic fields, and gravity can lead to experiments with lower systematic errors than have been obtained in experiments with cold neutron beams. The UCN densities provided by existing reactor sources limit these experiments. The promise of much higher densities from solid deuterium sources has led to proposed facilities coupled to both reactor and spallation neutron sources. In this Letter we report on the performance of a prototype spallation neutron-driven solid deuterium source. This source produced bottled UCN densities of 145±7 UCN/cm 3 , about three times greater than the largest bottled UCN densities previously reported. These results indicate that a production UCN source with substantially higher densities should be possible.

The performance of radiation detectors fabricated from semi-insulating (SI) GaAs is highly sensitive to EL2+-concentration in the material. Near-infrared optical absorption measurements are commonly used to determine the EL2-concentration and to roughly estimate the EL2+-concentration under the assumption that the optical absorption is mainly determined by the photoionization and the photoneutralization of EL20 and EL2+, respectively. However, the presence of different native defects can contribute to optical absorption and reduce the precision of determination of EL2-concentration. In this work, we evaluate the contributions into optical absorption from EL2 and other deep center namely EL3 defect (0.55 eV) using near-infrared optical absorption and photoconductivity (PC) measurements in the photon energy interval 0.5–1.4 eV for SI GaAs crystals grown by the liquid encapsulated Czochralski method from melts with As content changing from 50% to about 46%. The photoelectrical spectra were measured on p–i–n structure detectors with heavily doped p+ and n+ layers grown by Liquid Phase Epitaxy and on Schottky diodes. The short circuit photocurrent spectra were registered for all detectors in the energy interval 0.65–1.4 eV. Unexpectedly, the current sensitivities in the regions of the extrinsic and intrinsic absorption were comparable. A comparative study of optical absorption, PC and short circuit photocurrent spectra resulted in determination of EL2+-concentration. It was concluded that contribution of additional deep centers, particularly the ionized EL3+ defect could be comparable to the EL2-contribution. The EL3 centers were attributed to oxygen-related defects based on published results and on some indirect evidence in our experimental data.

Dramatic progress has been made in the last several years in our understanding of the properties of neutrinos with evidence for neutrino flavor transformation coming from measurements of atmospheric neutrinos by SuperKamiokande, of solar neutrinos by the Sudbury Neutrino Observatory (SNO), and of reactor neutrinos by KamLAND. These results are a step in the ongoing program of science that is carried out in underground laboratories. The potential for additional significant discoveries with new capabilities in underground laboratories exists and should be exploited. Discoveries are likely to be made not only in nuclear and particle physics, but also in astrophysics, geophysics, and geobiology. A concerted effort is now underway in the United States to create a National Underground Science and Engineering Laboratory (NUSEL) that would provide the facilities and infrastructure necessary to capitalize on the opportunities presented by underground science.

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).

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.

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.

The beam-helicity asymmetry in associated electroproduction of real photons, ep -> aEuro parts per thousand e gamma pi N , in the Delta(1232)-resonance region is measured using the longitudinally polarized Hera positron beam and an unpolarized hydrogen target. Azimuthal Fourier amplitudes of this asymmetry are extracted separately for two channels, ep -> aEuro parts per thousand e gamma pi(0) p and ep -> aEuro parts per thousand e gamma pi(+) n, from a data set collected with a recoil detector. All asymmetry amplitudes are found to be consistent with zero.

Single-spin asymmetries were investigated in inclusive electroproduction of charged pions and kaons from transversely polarized protons at the HERMES experiment. The asymmetries were studied as a function of the azimuthal angle $\psi$ about the beam direction between the target-spin direction and the hadron production plane, the transverse hadron momentum relative to the direction of the incident beam, and the Feynman variable $x_F$. The $\sin(\psi)$ amplitudes are positive for positive pions and kaons, slightly negative for negative pions and consistent with zero for negative kaons, with particular transverse-momentum but weak $x_F$ dependences. Especially large asymmetries are observed for two small subsamples of events, where also the scattered electron was recorded by the spectrometer., Comment: 10 pages, 5 figures

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 (

The solar-neutrino-capture rate measured by the Russian-American Gallium Experiment on metallic gallium during the period from January 1990 to December 1997 is (67.2 −7.0−3.0 +7.2+3.5 ) SNU, where the uncertainties are statistical and systematic, respectively. This result represents a 7σ depression in the neutrino flux in relation to the predicted standard-solar-model rates. The experimental procedures used and data analysis are presented.

The standard electro-weak model predicts negligible violation of time-reversal invariance in light quark processes. We report on an experimental test of time-reversal invariance in the beta decay of polarized neutrons as a search for physics beyond the standard model. The emiT collaboration has measured the time-reversal-violating triple-correlation in neutron beta decay between the neutron spin, electron momentum, and neutrino momentum often referred to as the D coe$cient. The "rst run of the experiment produced 14 million events which are currently being analyzed. However, a second run with improved detectors should provide greater statistical precision and reduced systematic uncertainties. ( 2000 Elsevier Science B.V. All rights reserved.

The results of experiments and calculations for a solid-deuterium UCN source are presented. It was experimentally shown that the UCN yield is increased by a factor 3 at the solidification of liquid deuterium and a factor 10 at a temperature 10 K, with respect to the liquid phase. The gain factor for UCN yield with respect to hydrogen gas or deuterium gas at room temperature is equal to 1230.

A prototype of a solid deuterium (SD 2 ) source of Ultra-Cold Neutrons (UCN) is currently being tested at LANSCE. The source is contained within an assembly consisting of a 4 K polyethylene moderator surrounded by a 77 K beryllium flux trap in which is embedded a spallation target. Time-of-flight measurements have been made of the cold neutron spectrum emerging directly from the flux trap assembly. A comparison is presented of these measurements with results of Monte Carlo (LAHET/MCNP) calculations of the cold neutron fluxes produced in the prototype assembly by a beam of 800 MeV protons incident on the tungsten target. A UCN detector was coupled to the assembly through a guide system with a critical velocity of 8 m/s ( 58 Ni). The rates and time-of-flight data from this detector are compared with calculated values. Measurements of UCN production as a function of SD 2 volume (thickness) are compared with predicted values. The dependence of UCN production on SD 2 temperature and proton beam intensity are also presented.

Depolarization of ultra-cold neutrons (UCN) stored in material traps was "rst observed. The probability of UCN spin #ip per re#ection depends on the trap material and varies from 7]10~6 (beryllium) to 10~4 (glass). ( 2000 Elsevier Science B.V. All rights reserved.

The results on electrical characteristics and charge collection efficiency in the detectors from bulk SI GaAs developed as a material for solar neutrino spectroscopy are presented. SI GaAs crystals were grown by the Czochralski method. The changes in the stoichiometric components are permanently controlled. It is shown that the performance of GaAs p+–i–n+ structures provided the range of operational reverse voltage up to 1 kV. Measurement of deep level spectra and their analysis reveal the dominant deep levels – hole traps E v +0.51 and +0.075 eV in GaAs grown from stoichiometric and nonstoichiometric melts, respectively. Investigation of carrier transport properties and bulk homogeneity evinced in charge collection efficiency has shown advantageous results for SI GaAs grown from stoichiometric melt. The reduction of carrier transport parameters and charge collection efficiency in GaAs grown from nonstoichiometric melt is analyzed taking into consideration formation of the hole trap E v +0.075 eV, presumably assigned to Ga antisite and its influence on the concentration of the ionized deep donor level EL2+.

Semi-insulating GaAs crystals grown by liquid encapsulated Czochralski technique from Ga-rich melts were evaluated as a possible material for radiation detectors with a high active layer thickness. The density of deep traps, particularly the midgap EL2 donors pinning the Fermi level, was measured by various techniques in conducting and semi-insulating samples. For EL2 traps, a direct evidence of their partial neutralization in the space charge region of reverse biased Schottky diodes due to nonequilibrium capture of electrons is presented for the first time. It is shown that the density of EL2 centers decreases with decreased As composition of the melt very gradually, especially for post-growth annealed samples. Subsequently, if one aims to decrease the EL2 density to such an extent that it would make a serious impact on the depletion layer width in GaAs-based detectors one has to grow semi-insulating GaAs crystals from melts with As composition below about 43% which poses a problem for the preservation of high resistivity of the material due to the relatively high concentration of compensating acceptors.

In this paper we describe the principles that have guided our design and the experience we have gained building multi-wire proportional chambers detectors for the ultra-cold neutron (UCN) source at the Los Alamos Neutron Science Center (LANSCE). Simple robust detectors with 50 cm2 of active area have been designed. These have been used both in ion chamber and proportional mode for the detection of UCN.

Current solar neutrino detectors measure a considerably lower flux of electron-flavor neutrinos than predicted by solar models. This could be an indication of neutrino oscillations, which would provide direct evidence that neutrinos have mass. The Sudbury Neutrino Observatory (SNO) was designed to detect all flavors of neutrinos, and will provide a rigorous test of this theory. The SNO detector's heavy water target gives it the unique ability to detect all non-sterile neutrino flavors via the neutral-current (NC) break-up of the deuteron. This NC interaction liberates a neutron which may be detected with an array of discrete /sup 3/He proportional counters. The strict radioactivity requirements imposed by the need for low backgrounds dictate the use of ultra-pure materials and processes in building these counters. Additionally, they must survive in the heavy water environment for several years. The design, construction, and testing of these unique counters are described.

The neutrino capture rate measured by the Russian-American Gallium Experiment is well below that predicted by solar models. To check the response of this experiment to low-energy neutrinos, a 517 kCi source of 51Cr was produced by irradiating 512.7 g of 92.4%-enriched 50Cr in a high-flux fast neutron reactor. This source, which mainly emits monoenergetic 747-keV neutrinos, was placed at the center of a 13.1 tonne target of liquid gallium and the cross section for the production of 71Ge by the inverse beta decay reaction was measured to be (5.55 +/- 0.60 (stat.) +/- 0.32 (syst.)) x 10^(-45) cm^2. The ratio of this cross section to the theoretical cross section of Bahcall for this reaction is 0.95 +/- 0.12 (exp.) +/- 0.03 (theor.) and to the cross section of Haxton is 0.87 +/- 0.11 (exp.) +/- 0.09 (theor.). This good agreement between prediction and observation implies that the overall experimental efficiency for the solar neutrino measurements is correctly determined and provides considerable evidence for the reliability of the solar neutrino measurement., 20 pages including figures in two column format

An intense source of 37Ar was produced by the (n, α) reaction on 40Ca by irradiating calcium oxide in the fast neutron breeder reactor at Zarechny, Russia. The 37Ar was released from the solid target, sealed into a small source, and was used to irradiate 13 tonnes of gallium metal in the Russian-American gallium solar neutrino experiment SAGE. The initial source strength was 409 ± 2 kCi. The measured production rate of 71Ge on gallium metal was 11.0+1.0−0.9 (stat) ± 0.6 (syst.) atoms per day, which is 0.79+0.09−0.10 of the theoretically calculated production rate.

The azimuthal cos{\phi} and cos2{\phi} modulations of the distribution of hadrons produced in unpolarized semi-inclusive deep-inelastic scattering of electrons and positrons off hydrogen and deuterium targets have been measured in the HERMES experiment. For the first time these modulations were determined in a four-dimensional kinematic space for positively and negatively charged pions and kaons separately, as well as for unidentified hadrons. These azimuthal dependences are sensitive to the transverse motion and polarization of the quarks within the nucleon via, e.g., the Cahn, Boer-Mulders and Collins effects.

This paper details the solar neutrino analysis of the 385.17-day phase-III data set acquired by the Sudbury Neutrino Observatory (SNO). An array of He-3 proportional counters was installed in the heavy-water target to measure precisely the rate of neutrino-deuteron neutral-current interactions. This technique to determine the total active B-8 solar neutrino flux was largely independent of the methods employed in previous phases. The total flux of active neutrinos was measured to be 5.54(-0.31)(+0.33)(stat.)(-0.34)(+0.36)(syst.) x 10(6) cm(-2) s(-1), consistent with previous measurements and standard solar models. A global analysis of solar and reactor neutrino mixing parameters yielded the best-fit values of Delta m(2) = 7.59(-0.21)(+0.19) x 10(-5) eV(2) and theta = 34.4(-1.2)(+1.3) degrees. DOI: 10.1103/PhysRevC.87.015502

For the final running period of HERA, a recoil detector was installed at the HERMES experiment to improve measurements of hard exclusive processes in charged-lepton nucleon scattering. Here, deeply virtual Compton scattering is of particular interest as this process provides constraints on generalised parton distributions that give access to the total angular momenta of quarks within the nucleon. The HERMES recoil detector was designed to improve the selection of exclusive events by a direct measurement of the four-momentum of the recoiling particle. It consisted of three components: two layers of double-sided silicon strip sensors inside the HERA beam vacuum, a two-barrel scintillating fibre tracker, and a photon detector. All sub-detectors were located inside a solenoidal magnetic field with an integrated field strength of 1 T. The recoil detector was installed in late 2005. After the commissioning of all components was finished in September 2006, it operated stably until the end of data taking at HERA end of June 2007. The present paper gives a brief overview of the physics processes of interest and the general detector design. The recoil detector components, their calibration, the momentum reconstruction of charged particles, and the event selection are described in detail. The paper closes with a summary of the performance of the detection system., Comment: 50 pages, 72 figures

The Russian-American Gallium Solar Neutrino Experiment (SAGE) is described. Beginning in September 1992, SAGE II data were taken with 55 tons of Ga and with significantly reduced backgrounds. The solar neutrino flux measured by 31 extractions through October 1993 is presented. The result of 69 {+-} 10 +5/{minus}7 SNU is to be compared with a Standard Solar Model prediction of 132 SNU.

We present a detailed report of a measurement of the neutron β-asymmetry parameter A_0, the parity-violating angular correlation between the neutron spin and the decay electron momentum, performed with polarized ultracold neutrons (UCN). UCN were extracted from a pulsed spallation solid deuterium source and polarized via transport through a 7-T magnetic field. The polarized UCN were then transported through an adiabatic-fast-passage spin-flipper field region, prior to storage in a cylindrical decay volume situated within a 1-T 2×2π solenoidal spectrometer. The asymmetry was extracted from measurements of the decay electrons in multiwire proportional chamber and plastic scintillator detector packages located on both ends of the spectrometer. From an analysis of data acquired during runs in 2008 and 2009, we report A_0=−0.11966±0.00089_(−0.00140)^(+0.00123), from which we extract a value for the ratio of the weak axial-vector and vector coupling constants of the nucleon, λ=g_A/g_V=−1.27590±0.00239_(−0.00377)^(+0.00331). Complete details of the analysis are presented.

Multiplicities in semi-inclusive deep-inelastic scattering are presented for each charge state of ${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$ and ${\mathrm{K}}^{\ifmmode\pm\else\textpm\fi{}}$ mesons. The data were collected by the HERMES experiment at the HERA storage ring using 27.6 GeV electron and positron beams incident on a hydrogen or deuterium gas target. The results are presented as a function of the kinematic quantities ${x}_{\mathrm{B}}$, ${Q}^{2}$, $z$, and ${P}_{h\ensuremath{\perp}}$. They represent a unique data set for identified hadrons that will significantly enhance our understanding of the fragmentation of quarks into final-state hadrons in deep-inelastic scattering.

A radiochemical {sup 71}Ga-{sup 71}Ge experiment to determine the primary flux of neutrinos from the Sun began measurements of the solar neutrino flux at the Baksan Neutrino Observatory in 1990. The number of {sup 71}Ge atoms extracted from initially 30 and later 57 tons of metallic gallium was measured in fifteen runs during the period of January 1990 to May 1992. The observed capture rate is 70{plus_minus}19 (stat){plus_minus}10 (syst) SNU. This is to be compared with 132 SNU predicted by the Standard Solar Model.

Fifteen measurements of the solar neutrino flux have been made in a radiochemical 71Ga-71Ge experiment employing initially 30 t and later 57 t of liquid metallic gallium at the Baksan Neutrino Observatory between January 1990 and May 1992. This provides an integral measurement of the flux of solar neutrinos and in particular is sensitive to the dominant, low-energy p-p solar neutrinos. SAGE observed the capture rate to be 73−16+18 (stat.)−7+5 (syst.) SNU. This represents only 56%−60% of the capture rate predicted by different Standard Solar Models.

Double-spin asymmetries in exclusive electroproduction of real photons from a transversely polarized hydrogen target are measured with respect to the product of target polarization with beam helicity and beam charge, and with respect to the product of target polarization with beam helicity alone. The asymmetries arise from the deeply virtual Compton scattering process and its interference with the Bethe--Heitler process. They are related to the real part of the same combination of Compton form factors as that determining the previously published transverse target single-spin asymmetries through the imaginary part. The results for the double-spin asymmetries are found to be compatible with zero within the uncertainties of the measurement, and are not incompatible with the predictions of the only available GPD-based calculation., Comment: 9 pages, 4 figures, and 3 tables

Perhaps the most outstanding discrepancy between prediction and measurements in current particle physics comes from the solar neutrino problem, in which a large deficit of high-energy solar neutrinos is observed. Many Nonstandard Solar Models have been invoked to try to reduce the predicted flux, but all have run into problems in trying to reproduce other measured parameters (e.g., the luminosity) of the Sun. Other explanations involving new physics such as neutrino decay and neutrino oscillations, etc. have also been proffered. Again, most of these explanations have been ruled out by either laboratory or astrophysical measurements. It appears that perhaps the most likely particle physics solution is that of matter enhanced neutrino oscillation, the Mikheyev-Smirnov-Wolfenstein (MSW) oscillations. Two new radiochemical gallium experiments, which have a low enough threshold to be sensitive to the dominant flux of low-energy p-p neutrinos, now also report a deficit and also favor a particle physics solution. The next generation of solar experiments promise to finally resolve the source of the ``solar neutrino problem`` by the end of this decade.

A radiochemical {sup 71}Ga-{sup 71}Ge experiment to determine the primary flux of neutrinos from the Sun has begun operation at the Baksan Neutrino Observatory. The number of {sup 71}Ge atoms extracted from thirty tons of gallium was measured in five runs during the period of January to July 1990. Assuming that the extraction efficiency for {sup 71}Ge atoms produced by solar neutrinos is the same as from natural Ge carrier, we observed the capture rate to be 20 + 15/{minus}20 (stat) {plus minus} 32 (syst) SNU, resulting in a limit of less than 79 SNU (90% CL). This is to be compared with 132 SNU predicted by the Standard Solar Model.

Neutrino-electron elastic scattering was observed with a 15-ton fine-grained tracking calorimeter exposed to electron neutrinos from muon decay at rest. The measured ${\ensuremath{\nu}}_{e}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\nu}}_{e}{e}^{\ensuremath{-}}$ elastic scattering rate of 236\ifmmode\pm\else\textpm\fi{}35 events yields the total elastic scattering cross section $10.0\ifmmode\pm\else\textpm\fi{}1.5(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.9(\mathrm{syst})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}45} \mathrm{c}{\mathrm{m}}^{2}\ifmmode\times\else\texttimes\fi{}[{E}_{\ensuremath{\nu}} (\mathrm{MeV})]$, and a model-independent measurement of the strength of the destructive interference between the charged and neutral currents, $I=\ensuremath{-}1.07\ifmmode\pm\else\textpm\fi{}0.21$, that agrees well with the standard model (SM) prediction $I=\ensuremath{-}1.08$. The agreement between the measured electroweak parameters and SM expectations is used to place limits on neutrino properties, such as neutrino flavor-changing neutral currents and neutrino electromagnetic moments. Limits are placed on the masses of new bosons that interact with leptons: for a neutral tensor boson, ${M}_{T}g105$ GeV; for a neutral (pseudo)scalar boson, ${M}_{P,S}g47$ GeV; for a charged Higgs boson, ${M}_{{\ensuremath{\chi}}^{+}}g87$ GeV; and for a purely left-handed charged (neutral) vector boson, ${M}_{x}g239 (119)$ GeV.

A precise measurement of the neutron decay $\beta$-asymmetry $A_0$ has been carried out using polarized ultracold neutrons (UCN) from the pulsed spallation UCN source at the Los Alamos Neutron Science Center (LANSCE). Combining data obtained in 2008 and 2009, we report $A_0 = -0.11966 \pm 0.00089_{-0.00140}^{+0.00123}$, from which we determine the ratio of the axial-vector to vector weak coupling of the nucleon $g_A/g_V = -1.27590_{-0.00445}^{+0.00409}$., Comment: 5 pages, 2 figures

Single-spin asymmetries for pions and charged kaons are measured in semi-inclusive deep-inelastic scattering of positrons and electrons off a transversely nuclear-polarized hydrogen target. The dependence of the cross section on the azimuthal angles of the target polarization (phi_S)and the produced hadron (phi) is found to have a substantial sin(phi+phi_S) modulation for the production of pi+, pi- and K+. This Fourier component can be interpreted in terms of non-zero transversity distribution functions and non-zero favored and disfavored Collins fragmentation functions with opposite sign. For pi0 and K- production the amplitude of this Fourier component is consistent with zero., Comment: 7 pages, 3 figures

The process of electron emission from {similar to}30 MeV neutrino absorption on carbon, {sup 12}C({nu}{sub {ital e}},{ital e}{sup {minus}}){sup 12}N, has been observed. The flux-weighted total cross section for the exclusive neutrino-induced nuclear transition {sup 12}C({nu}{sub {ital e}},{ital e}{sup {minus}}){sup 12}N(g.s.) is (1.05{plus minus}0.10(stat){plus minus}0.10(syst)){times}10{sup {minus}41} cm{sup 2}. The measured cross section and angular distribution {ital d}{sigma}/{ital d}{Omega} are in agreement with theoretical estimates. The inclusive {nu}{sub {ital e}} {sup 12}C reaction rate, which accounted for the majority of all neutrino interactions observed in this experiment, was determined from a detailed fit of energy and angular distributions for the observed electrons. The inclusive {sup 12}C({nu}{sub {ital e}},{ital e}{sup {minus}}){ital X} cross section is measured to be (1.41{plus minus}0.23(tot)){times}10{sup {minus}41} cm{sup 2}. An upper limit for the sum of the {sup 13}C({nu}{sub {ital e}},{ital e}{sup {minus}}){ital X}+{sup 27}Al({nu}{sub {ital e}},{ital e}{sup {minus}}){ital X} inclusive absorption cross sections is presented.

The transverse-target single-spin asymmetry for inclusive deep-inelastic scattering with effectively unpolarized electron and positron beams off a transversely polarized hydrogen target was measured, with the goal of searching for a two-photon exchange signal in the kinematic range 0.007 < x_B < 0.9 and 0.25 GeV**2 < Q**2 < 20 GeV**2. In two separate regions Q**2 > 1 GeV**2 and Q**2 < 1 GeV**2, and for both electron and positron beams, the asymmetries are found to be consistent with zero within statistical and systematic uncertainties, which are of order 10**(-3) for the asymmetries integrated over x_B., 5 pages, 1 figure, revised text

The nuclear-mass dependence of azimuthal cross section asymmetries with respect to charge and longitudinal polarization of the lepton beam is studiedfor hard exclusive electroproduction of real photons. The observed beam-charge and beam-helicity asymmetries are attributed to the interference between the Bethe-Heitler and deeply virtual Compton scattering processes. For various nuclei, the asymmetries are extracted for both coherent and incoherent-enriched regions, which involve different (combinations of) generalized parton distributions. For both regions, the asymmetries are compared to those for a free proton, and no nuclear-mass dependence is found., Comment: 11 pages, 9 figures, 4 tables, minor revisions of text

A radiochemical {sup 71}Ga-{sup 71}Ge experiment using 30 tons of gallium to determine the primary flux of neutrinos from the Sun has begun operation at the Baksan Neutrino Observatory in the U.S.S.R. Assuming that the extraction efficiency for {sup 71}Ge atoms produced by solar neutrinos is the same as from natural Ge carrier, we observed the capture rate to be 20{sub {minus}20}{sup +15}(stat){plus minus}32(syst) solar neutrino units (SNU), resulting in a limit of less than 79 SNU (90% C.L.). This is to be compared with 132 SNU predicted by the standard solar model.

We report the most sensitive direct upper limit set on the mass {ital m}{sub {nu}} of the electron antineutrino. Our measurements of the shape of the {beta} decay spectrum of free molecular tritium yield, under the assumption of no new physics other than that of mass, a central value for {ital m}{sub {nu}}{sup 2} of {minus}147{plus minus}68{plus minus}41 eV{sup 2}, which corresponds to an upper limit of 9.3 eV (95% confidence level) on {ital m}{sub {nu}}. The result is in clear disagreement with a reported value of 26(5) eV.

A sensitive search for ${\ensuremath{\nu}}_{\ensuremath{\mu}}$ and ${\overline{\ensuremath{\nu}}}_{\ensuremath{\mu}}$ decay into photons was performed in a high-intensity beam of neutrinos from ${\ensuremath{\pi}}^{+}$ and ${\ensuremath{\mu}}^{+}$ decay at rest. An upper limit of 68 possible $\ensuremath{\gamma}$-ray events was established, leading to a lower bound on the radiative lifetime of the muon (anti)neutrino of $\frac{\ensuremath{\tau}}{{m}_{{\ensuremath{\nu}}_{\ensuremath{\mu}}}}\ensuremath{\ge}15.4$ sec/eV (90% C.L.). This result represents more than a factor of 100 improvement over previous direct laboratory searches.