nuSTORM: Neutrinos from Stored Muons

nuSTORM (Neutrinos from STORed Muons) is a proposed storage ring facility to deliver beams of muon antineutrinos and electron neutrinos from positive muon decays (muon neutrinos and electron antineutrinos from negative muon decays), with a central muon momentum of 3.8 GeV/c and a momentum acceptance of 10%. The facility will allow searches for eV-scale sterile neutrinos at better than 10 sigma sensitivity, it will be able to provide measurements of neutrino and antineutrino-nucleus scattering cross sections with percent-level precision and will serve as a first step towards developing muon accelerators for particle physics. We report on the physics capabilities of the nuSTORM facility and we specify the main features of its design, which does not require any new technology. The flux of the neutrino beam can be determined with percent-level accuracy to perform cross-section measurements for future neutrino oscillation experiments and to resolve the hints for eV-scale sterile neutrinos. nuSTORM may be considered as a first step towards a Neutrino Factory and a Muon Collider.Comment: 10 pages, 5 figures, Prospects in Neutrino Physics Conference (NuPhys). eConf (CNUM: C14-12-15

Heavy-to-light scalar form factors from Muskhelishvili-Omn\`es dispersion relations

By solving the Muskhelishvili-Omn\`es integral equations, the scalar form factors of the semileptonic heavy meson decays $D\to\pi \bar \ell \nu_\ell$, $D\to \bar{K} \bar \ell \nu_\ell$, $\bar{B}\to \pi \ell \bar\nu_\ell$ and $\bar{B}_s\to K \ell \bar\nu_\ell$ are simultaneously studied. As input, we employ unitarized heavy meson-Goldstone boson chiral coupled-channel amplitudes for the energy regions not far from thresholds, while, at high energies, adequate asymptotic conditions are imposed. The scalar form factors are expressed in terms of Omn\`es matrices multiplied by vector polynomials, which contain some undetermined dispersive subtraction constants. We make use of heavy quark and chiral symmetries to constrain these constants, which are fitted to lattice QCD results both in the charm and the bottom sectors, and in this latter sector to the light-cone sum rule predictions close to $q^2=0$ as well. We find a good simultaneous description of the scalar form factors for the four semileptonic decay reactions. From this combined fit, and taking advantage that scalar and vector form factors are equal at $q^2=0$, we obtain $|V_{cd}|=0.244\pm 0.022$, $|V_{cs}|=0.945\pm 0.041$ and $|V_{ub}|=(4.3\pm 0.7)\times10^{-3}$ for the involved Cabibbo-Kobayashi-Maskawa (CKM) matrix elements. In addition, we predict the following vector form factors at $q^2=0$: $|f_+^{D\to\eta}(0)|=0.01\pm 0.05$, $|f_+^{D_s\to K}(0)|=0.50 \pm 0.08$, $|f_+^{D_s\to\eta}(0)|=0.73\pm 0.03$ and $|f_+^{\bar{B}\to\eta}(0)|=0.82 \pm 0.08$, which might serve as alternatives to determine the CKM elements when experimental measurements of the corresponding differential decay rates become available. Finally, we predict the different form factors above the $q^2-$regions accessible in the semileptonic decays, up to moderate energies amenable to be described using the unitarized coupled-channel chiral approach.Comment: includes further discussions and references; matches the accepted versio

Fast computation of the Kohn-Sham susceptibility of large systems

For hybrid systems, such as molecules grafted onto solid surfaces, the calculation of linear response in time dependent density functional theory is slowed down by the need to calculate, in N^4 operations, the susceptibility of N non interacting Kohn-Sham reference electrons. We show how this susceptibility can be calculated N times faster within finite precision. By itself or in combination with previous methods, this should facilitate the calculation of TDDFT response and optical spectra of hybrid systems.Comment: submitted 25/1/200

Magnetic field morphology in nearby molecular clouds as revealed by starlight and submillimetre polarization

Within four nearby (d < 160 pc) molecular clouds, we statistically evaluate the structure of the interstellar magnetic field, projected on the plane of the sky and integrated along the line of sight, as inferred from the polarized thermal emission of Galactic dust observed by Planck at 353 GHz and from the optical and NIR polarization of background starlight. We compare the dispersion of the field orientation directly in vicinities with an area equivalent to that subtended by the Planck effective beam at 353 GHz (10') and using the second-order structure functions of the field orientation angles. We find that the average dispersion of the starlight-inferred field orientations within 10'-diameter vicinities is less than 20 deg, and that at these scales the mean field orientation is on average within 5 deg of that inferred from the submillimetre polarization observations in the considered regions. We also find that the dispersion of starlight polarization orientations and the polarization fractions within these vicinities are well reproduced by a Gaussian model of the turbulent structure of the magnetic field, in agreement with the findings reported by the Planck collaboration at scales greater than 10' and for comparable column densities. At scales greater than 10', we find differences of up to 14.7 deg between the second-order structure functions obtained from starlight and submillimetre polarization observations in the same positions in the plane of the sky, but comparison with a Gaussian model of the turbulent structure of the magnetic field indicates that these differences are small and are consistent with the difference in angular resolution between both techniques.Comment: 15 pages, 10 figures, submitted to A&

International Scoping Study (ISS) for a future neutrino factory and Super-Beam facility. Detectors and flux instrumentation for future neutrino facilities

This report summarises the conclusions from the detector group of the International Scoping Study of a future Neutrino Factory and Super-Beam neutrino facility. The baseline detector options for each possible neutrino beam are defined as follows: 1. A very massive (Megaton) water Cherenkov detector is the baseline option for a sub-GeV Beta Beam and Super Beam facility. 2. There are a number of possibilities for either a Beta Beam or Super Beam (SB) medium energy facility between 1-5 GeV. These include a totally active scintillating detector (TASD), a liquid argon TPC or a water Cherenkov detector. 3. A 100 kton magnetized iron neutrino detector (MIND) is the baseline to detect the wrong sign muon final states (golden channel) at a high energy (20-50 GeV) neutrino factory from muon decay. A 10 kton hybrid neutrino magnetic emulsion cloud chamber detector for wrong sign tau detection (silver channel) is a possible complement to MIND, if one needs to resolve degeneracies that appear in the delta-theta(13) parameter space

Toroidal magnetized iron neutrino detector for a neutrino factory

A neutrino factory has unparalleled physics reach for the discovery and measurement of CP violation in the neutrino sector. A far detector for a neutrino factory must have good charge identification with excellent background rejection and a large mass. An elegant solution is to construct a magnetized iron neutrino detector (MIND) along the lines of MINOS, where iron plates provide a toroidal magnetic field and scintillator planes provide 3D space points. In this paper, the current status of a simulation of a toroidal MIND for a neutrino factory is discussed in light of the recent measurements of large θ13. The response and performance using the 10 GeV neutrino factory configuration are presented. It is shown that this setup has equivalent δCP reach to a MIND with a dipole field and is sensitive to the discovery of CP violation over 85% of the values of δCP

The Golden Channel at a Neutrino Factory revisited: improved sensitivities from a Magnetised Iron Neutrino Detector

This paper describes the performance and sensitivity to neutrino mixing parameters of a Magnetised Iron Neutrino Detector (MIND) at a Neutrino Factory with a neutrino beam created from the decay of 10 GeV muons. Specifically, it is concerned with the ability of such a detector to detect muons of the opposite sign to those stored (wrong-sign muons) while suppressing contamination of the signal from the interactions of other neutrino species in the beam. A new more realistic simulation and analysis, which improves the efficiency of this detector at low energies, has been developed using the GENIE neutrino event generator and the GEANT4 simulation toolkit. Low energy neutrino events down to 1 GeV were selected, while reducing backgrounds to the $10^{-4}$ level. Signal efficiency plateaus of ~60% for $\nu_\mu$ and ~70% for $\bar{\nu}_\mu$ events were achieved starting at ~5 GeV. Contamination from the $\nu_\mu\rightarrow \nu_\tau$ oscillation channel was studied for the first time and was found to be at the level between 1% and 4%. Full response matrices are supplied for all the signal and background channels from 1 GeV to 10 GeV. The sensitivity of an experiment involving a MIND detector of 100 ktonnes at 2000 km from the Neutrino Factory is calculated for the case of $\sin^2 2\theta_{13}\sim 10^{-1}$. For this value of $\theta_{13}$, the accuracy in the measurement of the CP violating phase is estimated to be $\Delta \delta_{CP}\sim 3^\circ - 5^\circ$, depending on the value of $\delta_{CP}$, the CP coverage at $5\sigma$ is 85% and the mass hierarchy would be determined with better than $5\sigma$ level for all values of $\delta_{CP}$

Fast diffusion of a Lennard-Jones cluster on a crystalline surface

We present a Molecular Dynamics study of large Lennard-Jones clusters evolving on a crystalline surface. The static and the dynamic properties of the cluster are described. We find that large clusters can diffuse rapidly, as experimentally observed. The role of the mismatch between the lattice parameters of the cluster and the substrate is emphasized to explain the diffusion of the cluster. This diffusion can be described as a Brownian motion induced by the vibrationnal coupling to the substrate, a mechanism that has not been previously considered for cluster diffusion.Comment: latex, 5 pages with figure