Active to sterile neutrino mixing limits from neutral-current interactions in MINOS

Results are reported from a search for active to sterile neutrino oscillations in the MINOS long-baseline experiment, based on the observation of neutral-current neutrino interactions, from an exposure to the NuMI neutrino beam of 7.07×10(20) protons on target. A total of 802 neutral-current event candidates is observed in the Far Detector, compared to an expected number of 754 ± 28(stat) ± 37(syst) for oscillations among three active flavors. The fraction f(s) of disappearing ν(μ) that may transition to ν(s) is found to be less than 22% at the 90% C.L.     

Single-pion production in antineutrino-induced neutral-current interactions

Results are presented on antineutrino-induced processes in which a single π⁰or π^? is produced. The raw data come from analysis of film from Gargamelle filled with a propane-freon mixture. Comparison of the neutral-current production rates for π⁰and π^?, after correction for nuclear effects, indicates that pure isoscalar or pure isovector transitions are not favoured. The ratio of the neutral-to-charged-current single-π⁰ production rates is found to be compatible with the static model for Δ³³ resonance production in the framework of the Weinberg-Salam theory, yielding values for sin²θ_W in the range 0.15–0.52.     

Upper limits for charm production in 150 GeV p-Be interactions

A search has been made for the hadronic production of charmed baryons and mesons with a large aperture forward magnetic spectrometer using 150 GeV protons originating from the CERN-SPS. A prompt electron trigger was used as a signature for charm. Upper limits at 90% confidence level have been obtained for the production of $\text{Λ}{}_{\mathrm{<mtext>c</mtext>}}{}^{\mathrm{+}}\text{D}{}^0\text{,}\text{D}{}^0\text{D}{}^{\mathrm{+}}\text{and D}{}^{\mathrm{?}}\text{: σ(Λ}{}_{\mathrm{<mtext>c</mtext>}}\text{) ? 8 μ}\text{b}\text{, σ(}\text{D}{}^0\text{) ? 64 μ}\text{b}\text{, σ(}\text{D}{}^0\text{) < 37 μ}\text{b}\text{, σ(}\text{D}{}^{\mathrm{+}}\text{) ? 51 μ}\text{b and}\text{σ(}\text{D}{}^{\mathrm{?}}\text{) ? 49 μ}\text{b}$ per nucleon, assuming linear A dependence. Systematic errors due to uncertainties in branching ratios and to model dependence of the acceptance calculation are discussed.     

Almost unique determination of neutral-current couplings in neutrino-hadron interactions

Simultaneous analyses of inclusive and semi-inclusive reactionns in neutrino-nucleon collisions and elastic neutrino-proton scattering uniquely determine the neutral-current couplings between neutrinos and hadrons up to a two-fold “vector-axial-vector ambiguity”. One of the preferred solutions coincides with the Salam-Weinberg model within errors while the other solution, also compatible with SU(2) ? U(1) models with the simplest Higgs mechanism, may be helpful in understanding the bismuth puzzle.     

Effect of gluons on neutral-current interactions in deep inelastic neutrino scattering

The contribution of neutral spin-1 gluons to the deep inelastic neutral-current processesv(v)+N→v(v)+ hadrons is worked out in the parton model. Such a contribution violates Bjorken scaling strongly.     

Upper limits on a stochastic background of gravitational waves

The Laser Interferometer Gravitational-Wave Observatory has performed a third science run with much improved sensitivities of all three interferometers. We present an analysis of approximately 200 hours of data acquired during this run, used to search for a stochastic background of gravitational radiation. We place upper bounds on the energy density stored as gravitational radiation for three different spectral power laws. For the flat spectrum, our limit of omega0 < 8.4 x 10(-4) in the 69-156 Hz band is approximately 10(5) times lower than the previous result in this frequency range.     

Direct evidence for neutrino flavor transformation from neutral-current interactions in the Sudbury Neutrino Observatory

Observations of neutral-current nu interactions on deuterium in the Sudbury Neutrino Observatory are reported. Using the neutral current (NC), elastic scattering, and charged current reactions and assuming the standard 8B shape, the nu(e) component of the 8B solar flux is phis(e) = 1.76(+0.05)(-0.05)(stat)(+0.09)(-0.09)(syst) x 10(6) cm(-2) s(-1) for a kinetic energy threshold of 5 MeV. The non-nu(e) component is phi(mu)(tau) = 3.41(+0.45)(-0.45)(stat)(+0.48)(-0.45)(syst) x 10(6) cm(-2) s(-1), 5.3sigma greater than zero, providing strong evidence for solar nu(e) flavor transformation. The total flux measured with the NC reaction is phi(NC) = 5.09(+0.44)(-0.43)(stat)(+0.46)(-0.43)(syst) x 10(6) cm(-2) s(-1), consistent with solar models.     

Long range forces and limits on unparticle interactions

Couplings between standard model particles and unparticles from a nontrivial scale invariant sector can lead to long range forces. If the forces couple to quantities such as baryon or lepton (electron) number, stringent limits result from tests of the gravitational inverse square law. These limits are much stronger than from collider phenomenology and astrophysics.     

Weak neutral-current couplings of muons

Inversion of both the charge and the helicity of muon beams is considered as a possibility to determine the weak neutral-current couplings of muons, in particular the right-handed weak charge I^R₃(μ) and sin²θ without using the parton model.     

Upper limits of auditory rotational motion perception

Three experiments are reported, which investigated the auditory velocity thresholds beyond which listeners are no longer able to perceptually resolve a smooth circular trajectory. These thresholds were measured for band-limited noises, white noise, and harmonic sounds (HS), and in different acoustical environments. Experiments 1 and 2 were conducted in an acoustically dry laboratory. Observed thresholds varied as a function of stimulus type and spectral content. Thresholds for band-limited noises were unaffected by center frequency and equal to that of white noise. For HS, however, thresholds decreased as the fundamental frequency of the stimulus increased. The third experiment was a replication of the second in a reverberant concert hall, which produced qualitatively similar results except that thresholds were significantly higher than in the acoustically dry laboratory.     

Identifying neutrinos and antineutrinos in neutral-current scattering reactions

We study neutrino-induced nucleon knockout from nuclei. Expressions for the induced polarization are derived within the framework of the independent-nucleon model and the nonrelativistic plane-wave approximation. Large dissimilarities in the nucleon polarization asymmetries are observed between neutrino- and antineutrino-induced processes. These asymmetries represent a potential way to distinguish between neutrinos and antineutrinos in neutral-current neutrino scattering on nuclei. We discuss astrophysical applications of these polarization asymmetries. Our findings are illustrated for neutrino scattering on 16O and 208P b.     

Upper limits on parity-violating terms in nuclear electromagnetic operators and nuclear structure effects

Parity-violating (PV) nuclear experiments offer a suitable tool for investigating parity conservation in the electromagnetic interaction of nucleons. It has been estimated that PV electromagnetic vertices induced by weak interactions are very small. Thus, any sizeable PV nucleon electromagnetic couplings indicate the presence of a genuine PV electromagnetic interaction. The upper limit to such a PV electromagnetic interaction can be estimated from the existing experimental value for the circular polarization of γ-rays emitted in the radiative capture of a thermal neutron (n+p → d+γ). This estimate is consistent with the value for the circular γ-polarization measured in deformed nuclei (¹⁸¹Ta, ¹⁷⁷Hf). Useful additional information can be extracted from the measurement of the γ-asymmetry in the n+p → d+γ reaction and from the measurements of circular polarization in the decays of selected spherical nuclei (²⁰³Tl, ¹¹¹In, ⁶³Cu). Extensive theoretical analysis taking into account nuclear structure effects shows that the decay of ⁶³Cu is particularly suitable for this purpose.     

Upper limits on the cosmological gravitational wave background and maser clocks in space

We consider the possibility of detecting gravitational waves through the measurement of a time varying phase shift using a hydrogen maser clock on a satellite. Such measurements enable us to put interesting upper limits on the contribution of the gravitational-wave background to the dimensionless density of the Universe. The requirements on residual accelerations and the sensitivity of an accelerometer on the spacecraft are shown to be realistic and could be achieved using the accelerometer technology developed by ONERA for the ARISTOTELES mission. Such an experiment placing upper limits on the cosmological gravitational wave background could be conducted using the proposed Russian satellite Millimetron.On leave from the Astro Space Center, Lebedev Physical Institute, Moscow, Russia