Cosmic rays: direct measurements

This paper is based on the rapporteur talk given at the 34$^{th}$ International Cosmic Ray Conference (ICRC), on August 6$^{th}$, 2015. The purpose of the talk and paper is to provide a summary of the most recent results from balloon-borne and space-based experiments presented at the conference, and give an overview of the future missions and developments foreseen in this field.Comment: Write-up of the rapporteur talk given at the 34th International Cosmic Ray Conference, 30 July-6 August, 2015, The Hague, The Netherlands. 24 pages , 11 figure

Observation of charm mixing at CDF

We report on the observation of $D^0$--$\bar{D}^0$ oscillations by measuring the time-dependent ratio of yields for the rare decay $D^0 \rightarrow K^+\pi^-$ to the favored decay $D^0 \rightarrow K^-\pi^+$ at the Collider Detector at Fermilab (CDF). Using 9.6 fb$^{-1}$ of integrated luminosity of $\sqrt{s}$ = 1.96 TeV $p$$\bar{p}$ collisions recorded in the full CDF Run II, the signals of $7.6 \times 10^6$ $D^0\rightarrow K^-\pi^+$ and $33 \times 10^3$ $D^0\rightarrow K^+\pi^-$ decays are reconstructed in $D^{*}$-tagged events, with proper decay times between 0.75 and 10 mean $D^0$ lifetimes. We measure the mixing parameters $x'^2 = (0.08 \pm 0.18)\times 10^{-3}$, $y' = (4.3 \pm 4.3) \times 10^{-3}$, and $R_D = (3.51 \pm 0.35) \times 10^{-3}$. Our results are consistent with standard model expectations and similar results from proton-proton collisions and exclude the no-mixing hypothesis with a significance equivalent to 6.1 standard deviations.Comment: 6 pages, 7 figures, 1 table. Contribution to the proceedings for the 14th International Conference on B-Physics at Hadron Machines, April 8-12, 2013, Bologna, Ital

High-energy astroparticle physics with CALET

The CALorimetric Electron Telescope (CALET) will be installed on the Exposure Facility of the Japanese Experiment Module (JEM-EF) on the International Space Station (ISS) in 2014 where it will measure the cosmic-ray fluxes for five years. Its main scientific goals are to search for dark matter, investigate the mechanism of cosmic-ray acceleration and propagation in the Galaxy and discover possible astrophysical sources of high-energy electrons nearby the Earth. The instrument, under construction, consists of two layers of segmented plastic scintillators for the cosmic-ray charge identification (CHD), a 3 X$_0$-thick tungsten-scintillating fiber imaging calorimeter (IMC) and a 27 X$_0$-thick lead-tungstate calorimeter (TASC). The CHD can provide single-element separation in the interval of atomic number Z from 1 to 40, while IMC and TASC can measure the energy of cosmic-ray particles with excellent resolution in the range from few GeV up to several hundreds of TeV. Moreover, IMC and TASC provide the longitudinal and lateral development of the shower, a key issue for good electron/hadron discrimination. In this paper, we will review the status of the mission, the instrument configuration and its expected performance, and the CALET capability to measure the different components of the cosmic radiation.Comment: 4 pages, 3 figures. Contribution to the proceedings for the 23rd European Cosmic Ray Symposium 3-7 July 2012, Moscow, Russi

A Luttinger Liquid Core Inside Helium-4 Filled Nanopores

As helium-4 is cooled below 2.17 K it undergoes a phase transition to a fundamentally new state of matter known as a superfluid which supports flow without viscosity. This type of dissipationless transport can be observed by forcing helium to travel through a narrow constriction that the normal liquid could not penetrate. Recent experiments have highlighted the feasibility of fabricating smooth pores with nanometer radii, that approach the truly one dimensional limit where it is believed that a system of bosons (like helium-4) may have startlingly different behavior than in three dimensions. The one dimensional system is predicted to have a linear hydrodynamic description known as Luttinger liquid theory, where no type of long range order can be sustained. In the limit where the pore radius is small, Luttinger liquid theory would predict that helium inside the channel behaves as a sort of quasi-supersolid with all correlations decaying as power-law functions of distance at zero temperature. We have performed large scale quantum Monte Carlo simulations of helium-4 inside nanopores of varying radii at low temperature with realistic helium-helium and helium-pore interactions. The results indicate that helium inside the nanopore forms concentric cylindrical shells surrounding a core that can be described via Luttinger liquid theory and provides insights into the exciting possibility of the experimental detection of this intriguing low dimensional state of matter.Comment: 26 pages, 10 figure

Particle partition entanglement of one dimensional spinless fermions

We investigate the scaling of the R\'{e}nyi entanglement entropies for a particle bipartition of interacting spinless fermions in one spatial dimension. In the Tomonaga-Luttinger liquid regime, we calculate the second R\'{e}nyi entanglement entropy and show that the leading order finite-size scaling is equal to a universal logarithm of the system size plus a non-universal constant. Higher-order corrections decay as power-laws in the system size with exponents that depend only on the Luttinger parameter. We confirm the universality of our results by investigating the one dimensional $t-V$ model of interacting spinless fermions via exact-diagonalization techniques. The resulting sensitivity of the particle partition entanglement to boundary conditions and statistics supports its utility as a probe of quantum liquids.Comment: 19 pages, 6 figure

Quantum Monte Carlo measurement of the chemical potential of helium-4

A path integral Monte Carlo method based on the worm algorithm has been developed to compute the chemical potential of interacting bosonic quantum fluids. By applying it to finite-sized systems of helium-4 atoms, we have confirmed that the chemical potential scales inversely with the number of particles to lowest order. The introduction of a simple scaling form allows for the extrapolation of the chemical potential to the thermodynamic limit, where we observe excellent agreement with known experimental results for helium-4 at saturated vapor pressure. We speculate on future applications of the proposed technique, including its use in studies of confined quantum fluids.Comment: 7 pages, 4 figure

Backscattering Between Helical Edge States via Dynamic Nuclear Polarization

We show that that the non-equilibrium spin polarization of one dimensional helical edge states at the boundary of a two dimensional topological insulator can dynamically induce a polarization of nuclei via the hyperfine interaction. When combined with a spatially inhomogeneous Rashba coupling, the steady state polarization of the nuclei produces backscattering between the topologically protected edge states leading to a reduction in the conductance which persists to zero temperature. We study these effects in both short and long edges, uncovering deviations from Ohmic transport at finite temperature and a current noise spectrum which may hold the fingerprints for experimental verification of the backscattering mechanism.Comment: 4+ pages, 4 figure

Interacting bosons in one dimension and Luttinger liquid theory

Harmonically trapped ultra-cold atoms and helium-4 in nanopores provide new experimental realizations of bosons in one dimension, motivating the search for a more complete theoretical understanding of their low energy properties. Worm algorithm path integral quantum Monte Carlo results for interacting bosons restricted to the one dimensional continuum are compared to the finite temperature and system size predictions of Luttinger liquid theory. For large system sizes at low temperature, excellent agreement is obtained after including the leading irrelevant interactions in the Hamiltonian which are determined explicitly.Comment: 4 pages, 3 figure