Cross sections for charged current ν and\bar v interactions in the energy range 10 to 50 GeV

Charged-current neutrino and antineutrino interaction cross sections have been measured in the energy range 10 to 50 GeV using BEBC filled with a neon-hydrogen mixture. At these energies, σ/E was measured to be (0.73±0.08) 10^?38 cm²/GeV per nucleon for neutrinos and (0.32±0.06) 10^?38 cm²/GeV per nucleon for antineutrinos.     

Neutrino-induced deuteron disintegration in an experiment at the Krasnoyarsk nuclear reactor

The results of studying antineutrino interactions with deuterons (CCD and NCD reactions) and hydrogen (CCP) at the Krasnoyarsk underground reactor with the Deuteron detector are presented. The cross sections for NCD and CCD were measured with a precision of 9%. For CCP, the precision is 3%: σ _expt ^NCD =(3.35±0.31)×10^?44 cm²/fission ²³⁵U, σ _expt ^NCD =(1.08±0.09)×10^?44 cm²/fission ²³⁵U, and σ _expt ^NCD =(6.39±0.19)×10^?43 cm²/fission ²³⁵U. The precision of the experimental results is close to the theoretical one and is in good agreement with other experiments. The limit on the parameters of antineutrino oscillations into the sterile state was obtained: Δm ²≤4.7×10^?2 eV² for sin²(2?)=1.0 (68% C.L.). A comparison of the measured and theoretical cross section gives us the neutron-neutron scattering length of a _nn(S)=?17±6 fm in the approach of zero momentum transfers. The weak neutral current constant is in good agreement with the prediction of the Standard Model: G _A ^NC =G _A ^CC /0.932±0.056.     

Coherent single pion production by antineutrino charged current interactions and test of PCAC

The cross section for coherent production of a single π^? meson in charged current antineutrino interactions on neon nuclei has been measured in BEBC to be (175±25) 10^?40 cm²/neon nucleus, averaged over the energy spectrum of the antineutrino wide band beam at the CERN SPS; this corresponds to (0.9±0.1) % of the total charged current \(\bar v_\mu \) cross section. The distributions of kinematical variables are in agreement with theoretical predictions based on the PCAC hypothesis and the meson dominance model; in particular, theQ ² dependence is well described by a propagator containing a massm=(1.35±0.18) GeV. The absolute value of the cross section is also in agreement with the model. This analysis thus provides a test of the PCAC hypothesis in the antineutrino energy range 5–150 GeV.     

Quantum rotational scattering of H2 and its isotopologues with He

Quantum close-coupling computations of the rotational quenching of H₂ and its isotopologues due to He impact are performed using a highly accurate potential energy surface. State-to-state cross sections are obtained in a wide range of collision energies between 10^?5 cm^?1 and 10⁴ cm^?1, and the theoretical rate coefficients are reported for temperatures ranging from 10^?4 K to 3000 K. Compared with previous studies, the well depth of the potential adopted in this study is larger, leading to stronger resonance effects in the cross sections of He-HD. The accurate potential was employed to investigate the isotope effects of H₂ in detail. The cross-section resonances shift towards lower collision energies and become stronger with increasing reduced mass. The calculated cross sections and rate coefficients of H₂ and its isotopic variants in collisions with He are provided to study the energy transfer in these systems.     

Approximation of the electron excitation cross sections for triplet states excited from the 23 S 1 metastable state in helium

The method of approximated four-parameter representation of the electron-impact cross sections for a helium atom excited from the 2³ S ₁ metastable state into higher triplet states is applied and discussed. The approximation consists in interpolation over the whole set of the cross section values for each helium atomic level measured in our experiments and reported by other researchers. The approximation parameters and the cross sections calculated using these parameters for the maxima of the corresponding excitation functions are presented for 19 triplet levels of the S, P, and D HeI series with n=2–10. The interpolated values are compared to the theoretical cross sections. The serial regularities were investigated for the S, P, and D levels studied and a decrease in the cross sections for excitation from the given metastable state within each series, described by the approximate law Q=Cn ^?5, was revealed. Validity of the similarity relationship and the Bethe approximation for cross sections in the 2³ S?n ³ P series was verified. It is shown that the cross sections for a triplet level excitation from the 2³ S ₁ metastable state exceed the corresponding values for excitation from the ground state of helium by a factor of approximately 10³ for n=2 and 3 and 10 2 for the higher levels. It is concluded that the proposed method of representation of the cross sections for the electron-impact excitation of triplet levels from the metastable state increases accuracy and more importantly, reliability of the final results.     

Chemi-ionization and spin exchange upon collisions of metastable helium atoms with potassium atoms in the ground state

The spin exchange and chemi-ionization cross sections have been calculated for the metastable helium atom-potassium atom system in the ground state. The data on the spin exchange cross section in the system He(2³ S ₁)-K(4² S _1/2) have been obtained for the first time. The cross sections were calculated for the collision energies ranging from 2 × 10^?4 to 60 × 10^?4 au The chemi-ionization cross sections obtained have been compared with the data in the literature.     

Coherent production ofρ − mesons in charged current antineutrino-neon interactions in BEBC

Coherent production ofρ ^? mesons in charged current antineutrino interactions on neon nuclei is studied in the BEBC bubble chamber exposed to the CERN SPS wide band beam. The cross section is measured to be (95±25)·10^?40 cm² per neon nucleus, averaged over the beam energy spectrum. The distributions of kinematical variables and the absolute value of the cross section are in agreement with theoretical predictions based on the CVC hypothesis and the vector meson dominance model.     

Isotope effects in electron impact desorption of CO and O2 adsorbed on the (110) plane of tungsten

Results on the isotope effect for total and ionic desorption cross sections in the electron impact desorption of various binding states of CO on the (110) plane of tungsten, and of oxygen on this plane are presented and discussed. It is shown that the observations allow a dissection of cross sections into excitation cross sections and escape probabilities, and that the latter can be used to estimate lifetimes of excited or ionic states. It is found that excitation cross sections for total desorption are of the order of 10^?16–10^?17 cm², but seem to be significantly smaller in some cases for excitation to ionic states, suggesting that different excitations are involved. In all cases examined here the isotope effect for total desorption is much smaller than for ion production. This can be explained by the fact that ion lifetimes are somewhat shorter than those of excited neutrals. Lifetimes are estimated, in the cases examined, to be of the order of 10^?14s.     

L α emission from Ar++H2 collisions in the threshold energy region

In the energy range 2.4 to 33.3 eV_CM, relative cross sections have been measured forL _α emission from impact of Ar⁺ ions in a beam on a H₂ gas target. Absolute cross sections, obtained by normalization to literature data, are 1–10×10^?16cm² for metastable Ar⁺ and 1–20×10^?18cm² for ground state Ar⁺. In the former case, the dominant mechanism is probably dissociative electronic energy transfer, while in the latter case dissociative charge transfer is the most likely process. In addition, at the lowest energiesL _α resulting from a chemiluminescent rearrangement Ar⁺+H₂→ArH⁺+H(2p) has been observed.     

Total cross sections and nucleon structure functions in the gargamelle SPS neutrino/antineutrino experiment

Total neutrino and antineutrino cross sections in the energy range 15 to 150 GeV, and the nucleon structure functions, F₂(x, Q²) and xF₃(x, Q²) in the Q² range 0.5 to 50 (GeV/c)² have been measured using a data sample of 3000 neutrino and 3800 antineutrino events. The structure functions show a weak Q² dependence at different x values.     

Dynamical treatment of binding,polarization and recoil in asymmetric ion-atom collisions

The cross sections for quenching the lowestn ² P states of the alkali atoms Li, Na, K., and Rb by the inert gases He, Ne, Ar, Kr, and Xe are presented for 5 eV≦E _c.m.≦ 100 eV. These cross sections are derived from the corresponding cross sections for collisional excitation by applying the principle of microreversibility. Upper estimates for the quenching cross sections at thermal energies are given; in all studied cases the quenching cross sections are <8·10^?3Ų. These new upper limits are in most cases much lower than those obtained from other methods previously.     

Investigation of the mechanism of the reaction 10B(d, pγ)11B at E d = 15.3 MeV by the method of angular pγ correlations

The results are presented that were obtained by measuring the differential cross sections for the reaction ¹⁰B(d, p)¹¹B occurring at E _d = 15.3 MeV and leading to the production of a ¹¹B nucleus in the ground state (3/2^?) and in the lowest two excited states (the 1/2^? state at 2.125 MeV and the 5/2^? state at 4.445 MeV). The energy dependence of the differential cross section for this reaction was measured for several proton emission angles in the energy range E _d = 12–15.3 MeV. The double-differential cross sections for the reaction ¹⁰B(d, pγ)¹¹B were measured for the 5/2^? state of the ¹¹B nucleus at 4.445 MeV, and the angular dependences of the even spin-tensor components of the density matrix were reconstructed on the basis of these data. The angular dependences of the populations of magnetic sublevels are also given. The experimental results in question are compared with their theoretical counterparts obtained under the assumption of various reaction mechanisms (neutron stripping, heavy-particle stripping, and a two-step mechanism that takes into account the delay of interaction). On the basis of this comparison, the deformation parameters of the boron nuclei were found to be β ₂(¹⁰B) = ?0.55 and β ₂(¹¹B) = 0.4.     

Measurement of the hyperfine interaction of free75As ions In H2, He,Ne, Kr and Xe buffer environments and estimate of clolision cross sections in the eV and meV energy region

With the time-integral perturbed angular correlation (TIPAC) method the pressure dependence of the perturbation of the 121.1–279.5 keV γ-γ cascade in⁷⁵As has been investigated using gaseous H₂ ⁷⁵Se sources in different buffer environments. The obtained attenuation coefficients G₂₂ (∞) in the range of 0.55 to 1.0 were fitted with a theoretical stochastic model. In the region of low density, where the correlation time τ_C is large compared to the lifetime τ of the intermediate level of the nucleus, charge transfer collision cross sections have been evaluated between 8.1·10^?16 cm² for He, 1.3·10^?14 cm² for Xe and 1.8·10^?14 cm² for the molecular H₂ buffer gas. For increasing densities of the buffer gases the correlation time τ_C became small compared to the intermediate lifetime τ. The main effect in this region is the depolarization, and we found cross sections between 5.2·10^?15 cm² for He, 8.7·10^?14 cm² for Xe and 1.2·10^?13 cm² for the H₂ buffer gas.     

Trilepton production by neutrinos and antineutrinos

We calculate the electromagnetic and hadronic contributions to neutrino production of μ^?e⁺e^? events and antineutrino production of μ⁺e⁺e^? events. Due to an increase in cross section and acceptance, these rates are much larger in bubble-chamber experiments than the corresponding rates for trimuon events in counter experiments. Verification of these rates would confirm our understanding of the physics behind trilepton events. We stress the importance of measuring also a rate for μ^?e^? events to determine the cross section for the associated production of charmed particles.     

Electron impact ionization cross sections of beryllium and beryllium hydrides

We report calculated electron impact ionization cross sections (EICSs) for beryllium (Be) and some of its hydrides from the ionization threshold to 1 keV using the Deutsch-Märk (DM) and the Binary-Encounter-Bethe (BEB) formalisms. The positions of the maxima of the DM and BEB cross sections are very close in each case while the DM cross section values at the maxima are consistently higher. Our calculations for Be are in qualitative agreement with results from earlier calculations (convergent close-coupling, R matrix, distorted-wave and plane-wave Born approximation) in the low energy region. For the various beryllium hydrides, we know of no other available data. The maximum cross section values for the various compounds range from 4.0 × 10^?16 to 9.4 × 10^?16 cm² at energies of 44 to 56 eV for the DM cross sections and 3.0 × 10^?16 to 5.4 × 10^?16 cm² at energies of 40.5 to 60 eV for the BEB cross sections.     

Optical pumping of ions in buffer gases

Transient signals measured with a pulsed rf-optical pumping method are used to determine longitudinal relaxation rates for Sr⁺ ions (even isotopes) in noble gas buffers. Depolarization cross sections of the electronic spin in the Sr⁺5² S _1/2 ground state for binary collisions with rare gas atoms are deduced. The results for σ(Sr⁺5² S _1/2) in Ų are (at temperatures between 374 and 449 °K): 2·10^?5(He),4·10^?5(Ne), 5.7·10^?3(Ar), 1.8·10^?2(Kr), and 4.0·10^?2(Xe). These cross sections for the Sr⁺ ion are about two to three orders of magnitude larger than the corresponding ones for the isoelectronic neutral Rb atom. The large increase of the Sr⁺ relaxation rates is explained with the relaxation mechanism of spin-orbit coupling, taking into account two “indirect” effects of the ionic charge: the increase in the gas kinetic cross sections and the more intimate collisions of the Sr⁺ ion with the noble gas atoms. The depolarization is shown to be predominantly due to short-range interactions. A contribution to the relaxation of the Sr⁺ ion from Sr⁺-noble gas molecule formation, induced by three-body or resonant two-body collisions, could not be established for applied pressuresp between 1.5 and 15 Torr of Ar, Kr, and Xe.     

Messung der Wirkungsquerschnitte für die Linienverbreiterung von Hochfrequenzübergängen im 63 P 2-Zustand des Quecksilbers durch Stöße mit Edelgasatomen

The linewidth of high frequency transitions between Zeeman-levels of the metastable 6³ P ₂-state of mercury is measured as function of the pressure of various noble gases. The measurements are made for all noble gases in the pressure range from 10^?3 to about 2 · 10^?2 Torr. The cross sections for linebroadening due to atomic collisions are derived from the pressure dependence of the linewidth. These cross sections σ were found to be (71 ± 10) · 10^?16 cm² for He, (82 ± 10) · 10^?16 cm² for Ne, (153± 12) × 10^?16 cm² for Ar, (204±28) · 10¹⁶ cm² for Kr and (291 ± 41) · 10^?16 cm² for Xe.     

Gemma experiment: The results of neutrino magnetic moment search

The result of the neutrino magnetic moment (NMM) measurement at the Kalinin Nuclear Power Plant (KNPP) with GEMMA spectrometer is presented. The antineutrino-electron scattering is investigated. A high-purity germanium (HPGe) detector with a mass of 1.5 kg placed at a distance of 13.9 m from the 3 GW_th reactor core is exposed to the antineutrino flux of 2.7 × 10¹³ cm^?2s^?1. The recoil electron spectra taken in 18134 and 4487 h for the reactor ON and OFF periods are compared. The upper limit for the NMM μ_ν < 2.9 × 10^?11 μ_B at 90% C.L. is derived from the data processing.     

Measurement of the inclusive charged-current cross section for neutrino and antineutrino scattering on isoscalar nucleons

This paper reports on measurements of the total cross section for the inclusive reaction v_μ+N , as a function of incident energy. Neutrinos and antineutrinos with energy in the range 30–300 GeV were produced in the 1982 Fermilab narrow-band neutrino beamline. A total of 35 000 neutrino and 7000 antineutrino interactions were recorded in the CCFR detector located in LabE. The incident neutrino flux was determined by methods similar to those used in previous experiments. The rate of increase with energy of the total cross section (σ/E _v) in the range 30 to 75 GeV was determined to be 0.659±0.005(stat)±0.039(syst)×10^?38 cm²/GeV and 0.307±0.008(stat)±0.020(syst)×10^?38 cm²/GeV for incident neutrinos and antineutrinos, respectively. The 5.9% systematic errors are due primarily to uncertainties in the flux intensity measurement. The energy dependence of the cross section in the regionE _ν=100–300 GeV was found to be linear, as determined by relative normalization techniques. A weighted average of our previous and present measurement for the total ν-N cross section yields: $$\begin{gathered} \sigma (vN) = 0.666 \pm 0.020(statistical \hfill \\ + systematic)E_v 10^{ - 38} cm^2 ; \hfill \\ \sigma (\bar vN) = 0.324 \pm 0.014(statistical \hfill \\ + systematic)E_v 10^{ - 38} cm^2 ; \hfill \\ \end{gathered} $$ .