A
bstract
The yields and production rates of the radioisotopes
9
Li and
8
He created by cosmic muon spallation on
12
C, have been measured by the two detectors of the Double Chooz experiment. The ...identical detectors are located at separate sites and depths, which means that they are subject to different muon spectra. The near (far) detector has an overburden of ∼120 m.w.e. (∼300 m.w.e.) corresponding to a mean muon energy of 32.1 ± 2.0 GeV (63.7 ± 5.5 GeV). Comparing the data to a detailed simulation of the
9
Li and
8
He decays, the contribution of the
8
He radioisotope at both detectors is found to be compatible with zero. The observed
9
Li yields in the near and far detectors are 5.51 ± 0.51 and 7.90 ± 0.51, respectively, in units of 10
−8
μ
−1
g
−1
cm
2
. The shallow overburdens of the near and far detectors give a unique insight when combined with measurements by KamLAND and Borexino to give the first multi-experiment, data driven relationship between the
9
Li yield and the mean muon energy according to the power law
Y
=
Y
0
E
μ
/
1
GeV
α
¯
, giving
α
¯
=
0.72
±
0.06
and
Y
0
= (0.43 ± 0.11) × 10
−8
μ
−1
g
−1
cm
2
. This relationship gives future liquid scintillator based experiments the ability to predict their cosmogenic
9
Li background rates.
Superconducting nanowire single photon detectors are capable of single-photon detection across a large spectral range with near unity detection efficiency, picosecond timing jitter, and sub-10 mu m ...position resolution, at rates as high as 10(9) counts/s. In an effort to bring this technology into nuclear physics experiments, we fabricate niobium nitride (NbN) nanowire detectors using ion beam assisted sputtering and test their performance in strong magnetic fields. We demonstrate that these devices are capable of detection of 400 nm wavelength photons with saturated internal quantum efficiency at temperatures of 3 K and in magnetic fields of up to 5 T at high count rates and with nearly zero dark counts.
A new version of the two-fluid model is developed, specially devoted to liquid–vapour two-phase mixtures, but also relevant to liquid-gas and liquid–liquid mixtures. It is well-known that, over a ...large range of volume fractions, liquid–vapour mixtures behave as dispersions of particles in a carrier fluid. But the “particles” belong to one phase at the beginning of the phase change, and to the second phase at the end. Within the present model, the dispersed phase is not prescribed at the outset but is merely the one with the lower volume fraction. To simplify the issue, surface tension and interfacial properties are neglected. However, the differences of pressure, temperature and velocity between the two phases are taken into account. The exchanges of mass, momentum and energy between phases are split into a “mean-field” part corresponding to the average conditions imposed by the whole mixture on the dispersed phase, and a part specifically due to the disturbances created by the particles. Constraints on constitutive relations are obtained from the overall dissipation rate, and result in a closed set of seven equations for seven state variables including one volume fraction. We insist on the general form of the equations but not on the details of the closure relations. The limits of this simple model are clearly stated, and we discuss possible improvements, including a better account of small-scale kinetic phenomena, as well as an eighth equation for the density of interfaces.
Coherent elastic neutrino–nucleus scattering ($\hbox {CE}\nu \hbox {NS}$) offers a unique way to study neutrino properties and to search for new physics beyond the Standard Model. Nuclear reactors ...are promising sources to explore this process at low energies since they deliver large fluxes of anti-neutrinos with typical energies of a few MeV. In this paper, a new-generation experiment to study $\hbox {CE}\nu \hbox {NS}$ is described. The NUCLEUS experiment will use cryogenic detectors which feature an unprecedentedly low-energy threshold and a time response fast enough to be operated under above-ground conditions. Both sensitivity to low-energy nuclear recoils and a high event rate tolerance are stringent requirements to measuring $\hbox {CE}\nu \hbox {NS}$ of reactor anti-neutrinos. A new experimental site, the Very-Near-Site (VNS), at the Chooz nuclear power plant in France is described. The VNS is located between the two 4.25 $\hbox {GW}_{\mathrm {th}}$ reactor cores and matches the requirements of NUCLEUS. First results of on-site measurements of neutron and muon backgrounds, the expected dominant background contributions, are given. In this paper a preliminary experimental set-up with dedicated active and passive background reduction techniques and first background estimations are presented. Furthermore, the feasibility to operate the detectors in coincidence with an active muon veto at shallow overburden is studied. The paper concludes with a sensitivity study pointing out the physics potential of NUCLEUS at the Chooz nuclear power plant.
We report on measurements of the neutron spin asymmetries A{sub 1,2}{sup n} and polarized structure functions g{sub 1,2}{sup n} at three kinematics in the deep inelastic region, with x=0.33, 0.47, ...and 0.60 and Q{sup 2}=2.7, 3.5, and 4.8 (GeV/c){sup 2}, respectively. These measurements were performed using a 5.7 GeV longitudinally polarized electron beam and a polarized {sup 3}He target. The results for A{sub 1}{sup n} and g{sub 1}{sup n} at x=0.33 are consistent with previous world data and, at the two higher-x points, have improved the precision of the world data by about an order of magnitude. The new A{sub 1}{sup n} data show a zero crossing around x=0.47 and the value at x=0.60 is significantly positive. These results agree with a next-to-leading-order QCD analysis of previous world data. The trend of data at high x agrees with constituent quark model predictions but disagrees with that from leading-order perturbative QCD (PQCD) assuming hadron helicity conservation. Results for A{sub 2}{sup n} and g{sub 2}{sup n} have a precision comparable to the best world data in this kinematic region. Combined with previous world data, the moment d{sub 2}{sup n} was evaluated and the new result has improved the precision of this quantity by about a factor of 2. When combined with the world proton data, polarized quark distribution functions were extracted from the new g{sub 1}{sup n}/F{sub 1}{sup n} values based on the quark-parton model. While results for {delta}u/u agree well with predictions from various models, results for {delta}d/d disagree with the leading-order PQCD prediction when hadron helicity conservation is imposed.
Classical thermodynamics of irreversible processes is a valuable tool for the study of suspensions, provided due care is devoted to the selection of internal variables. As a first example, the ...flow-induced anisotropic microstructure appearing in many a suspension is usually depicted by a vector, the orientation and length of which are submitted to a statistical distribution. We show how irreversible thermodynamics imposes restrictions on the time evolution of that structural internal variable (and consequently on the time evolution of its statistical distribution), and how this evolution is related to the elastic stress of the suspension. As a second example, we consider the possibility of a mean relative motion between the particles and the suspending fluid. Upgrading that relative velocity to the status of an internal variable, we analyse the consequences concerning the transport of mass, momentum and energy, providing a link with the two-fluid model of suspensions, as well as with the well-known description of molecular mixtures.
A steady weak evaporation from or condensation onto a spherical condensed phase in its vapor gas is investigated, mainly numerically, on the basis of the Boltzmann equation for hard-sphere molecules. ...The numerical method is the combination of the hybrid-difference-scheme method, which can describe the discontinuity of the velocity distribution function in the gas, and the numerical kernel method 1. The velocity distribution function, macroscopic variables (pressure, temperature, flow velocity, heat flow), as well as mass and heat fluxes from the sphere into the gas, are obtained for the whole range of the Knudsen number. In addition, the solution of the heat transfer problem of a nonvolatile sphere in a rarefied gas is obtained as a special case of the present problem. The problem is also discussed from the standpoint of nonequilibrium thermodynamics.
We have measured the neutron spin asymmetry A{sub 1}{sup n} with high precision at three kinematics in the deep inelastic region at x = 0.33, 0.47 and 0.60, and Q{sup 2} = 2.7, 3.5 and 4.8 ...(GeV/c){sup 2}, respectively. Our results unambiguously show, for the first time, that A{sub 1}{sup n} crosses zero around x = 0.47 and becomes significantly positive at x = 0.60. Combined with the world proton data, polarized quark distributions were extracted. Our results, in general, agree with relativistic constituent quark models and with perturbative quantum chromodynamics (pQCD) analyses based on the earlier data. However they deviate from pQCD predictions based on hadron helicity conservation.
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