Experimental constraints on left-right symmetric models from muon decay

The TWIST Collaboration has completed a new measurement of the energy-angle spectrum of positrons from the decay of highly polarized muons. A simultaneous measurement of the muon decay parameters ρ, δ, and P(μ)(π)ξ tests the standard model in a purely leptonic process and provides improved limits for relevant extensions to the standard model. Specifically, for the generalized left-right symmetric model |(g(R)/g(L))ζ|<0.020 and (g(L)/g(R))m(2)>578 GeV/c(2), both 90% C.L.     

Cooperative behavior between oscillatory and excitable units: the peculiar role of positive coupling-frequency correlations

We study the collective dynamics of noise-driven excitable elements, so-called active rotators. Crucially here, the natural frequencies and the individual coupling strengths are drawn from some joint probability distribution. Combining a mean-field treatment with a Gaussian approximation allows us to find examples where the infinite-dimensional system is reduced to a few ordinary differential equations. Our focus lies in the cooperative behavior in a population consisting of two parts, where one is composed of excitable elements, while the other one contains only self-oscillatory units. Surprisingly, excitable behavior in the whole system sets in only if the excitable elements have a smaller coupling strength than the self-oscillating units. In this way positive local correlations between natural frequencies and couplings shape the global behavior of mixed populations of excitable and oscillatory elements.     

First dark matter search results from the PandaX-I experiment

We report on the first dark-matter (DM) search results from PandaX-I, a low threshold dual-phase xenon experiment operating at the China JinPing Underground Laboratory. In the 37-kg liquid xenon target with 17.4 live-days of exposure, no DM particle candidate event was found. This result sets a stringent limit for low-mass DM particles and disfavors the interpretation of previously-reported positive experimental results. The minimum upper limit, 3.7 × 10^?44 cm², for the spin-independent isoscalar DM-particle-nucleon scattering cross section is obtained at a DM-particle mass of 49GeV/c² at 90% confidence level.     

Jet measurements by ALICE at LHC

Jets are collimated sprays of particles originating from fragmentation of high energy partons produced in a hard collision. They are an important diagnostic tool in studies of the Quark Gluon Plasma (QGP). The modification of the jet fragmentation pattern and its structure is a signature for the influence of hot and dense matter on the parton fragmentation process. Jet measurements in proton-proton collisions provide a baseline for similar measurements in heavy-ion collisions, while studies in proton-nucleus system allow to estimate cold nuclear matter effects. Here we present jet studies in different colliding systems (p–p, p–Pb, Pb–Pb) performed by the ALICE collaboration at LHC energies. Results on jet spectra, cross sections, nuclear modification factors, jet structure and other kinematic observables will be presented.     

Study of D_s~±→μ~±V_μ at Belle

We present a preliminary measurement of the B(D_s→μν_μ)with the Belle experiment at the KEKB collider.We select D~s→μV_μdecays with a method that provides a high-purity of the selected sample and an absolute measurement of the branching fraction.The results are based on a data sample of 550 fb~(-1)and are compared to similar measurements by other experiments as well as to the predictions of LQCD.We conclude with short prospects for improvements in the accuracy of the measurement.     

Roper resonance—Its static and dynamic properties from single- and double-pion production

In most investigations the Roper resonance is sensed only very indirectly via complex partial wave analyses. We find indications for its excitation in the pp→npπ⁺ reaction, where some resonance-like structure is observed in the invariant nπ⁺ mass spectrum at with a width of 150 MeV. The values fit very favorably to the most recent phase shift results as well as to the observations at BES. In near-threshold two-pion production pp→ppπ⁰π⁰ the Roper excitation and its subsequent decay into Nππ is the only dominant process. There we find its decay into the Nσ channel as the dominating decay process — in favor of a monopole nature of the Roper excitation.     

Temporally controlled modulation of antihydrogen production and the temperature scaling of antiproton-positron recombination

We demonstrate temporally controlled modulation of cold antihydrogen production by periodic RF heating of a positron plasma during antiproton-positron mixing in a Penning trap. Our observations have established a pulsed source of atomic antimatter, with a rise time of about 1 s, and a pulse length ranging from 3 to 100 s. Time-sensitive antihydrogen detection and positron plasma diagnostics, both capabilities of the ATHENA apparatus, allowed detailed studies of the pulsing behavior, which in turn gave information on the dependence of the antihydrogen production process on the positron temperature T. Our data are consistent with power law scaling T (-1.1+/-0.5) for the production rate in the high temperature regime from approximately 100 meV up to 1.5 eV. This is not in accord with the behavior accepted for conventional three-body recombination.     

Multipion systems in lattice QCD and the three-pion interaction

The ground-state energies of 2, 3, 4, and 5 pi(+)'s in a spatial volume V approximately (2.5 fm)(3) are computed with lattice QCD. By eliminating the leading contribution from three-pi(+) interactions, particular combinations of these n-pi(+) ground-state energies provide precise extractions of the pi(+)pi(+) scattering length in agreement with that obtained from calculations involving only two pi(+)'s. The three-pi(+) interaction can be isolated by forming other combinations of the n-pi(+) ground-state energies. We find a result that is consistent with a repulsive three-pi(+) interaction for m_(pi) less, similar352 MeV.     

New experimental limits on the probabilities of pauli-forbidden transitions in the <Superscript>12</Superscript>C nucleus from data obtained with the borexino detector

The Pauli exclusion principle was tested for nucleons in the ¹²C nucleus by using data from the Borexino detector. The approach used consisted in seeking photons, neutrons, and protons, as well as electrons and positrons, emitted in the Pauli-forbidden transitions of nucleons from the 1P _3/2 shell to the filled 1S _1/2 shell. Owing to a uniquely low background level in the Borexino detector and its large mass, the currently most stringent experimental limits were obtained for the probabilities and relative intensities of Pauli-forbidden transitions for the electromagnetic, strong, and weak channels.     

Solar Modulation of <Superscript>2</Superscript>H/<Superscript>1</Superscript>H and <Superscript>3</Superscript>He/<Superscript>4</Superscript>He according to Data Obtained in the PAMELA Satellite-Borne Experiment between 2006 and 2014

Preliminary results of measurements of the solar modulation of the isotopic hydrogen and helium content in galactic cosmic rays are presented for the first time. These data were obtained between 2006 and 2014 in the PAMELA international orbital experiment via measuring the time of flight of nuclei in the Pamela scintillation telescope and via analyzing, in the multilayered calorimeter of the PAMELA magnetic spectrometer, ionization losses of nuclei whose rigidity was known from trajectory measurements and which traversed the instrument without undergoing nuclear interactions. The results of these measurements are compared with existing experimental and calculated data, which are quite scanty.