First direct observation of muon antineutrino disappearance

This Letter reports the first direct observation of muon antineutrino disappearance. The MINOS experiment has taken data with an accelerator beam optimized for ν(μ) production, accumulating an exposure of 1.71 × 102? protons on target. In the Far Detector, 97 charged current ν(μ) events are observed. The no-oscillation hypothesis predicts 156 events and is excluded at 6.3σ. The best fit to oscillation yields |Δm2| = [3.36(-0.40)(+0.46)(stat) ± 0.06(syst)] × 10?3 eV2, sin2(2θ) = 0.86(-0.12)(+0.11)(stat) ± 0.01(syst). The MINOS ν(μ) and ν(μ) measurements are consistent at the 2.0% confidence level, assuming identical underlying oscillation parameters.     

Measurement of neutrino oscillation with KamLAND: evidence of spectral distortion

We present results of a study of neutrino oscillation based on a 766 ton/year exposure of KamLAND to reactor antineutrinos. We observe 258 nu (e) candidate events with energies above 3.4 MeV compared to 365.2+/-23.7 events expected in the absence of neutrino oscillation. Accounting for 17.8+/-7.3 expected background events, the statistical significance for reactor nu (e) disappearance is 99.998%. The observed energy spectrum disagrees with the expected spectral shape in the absence of neutrino oscillation at 99.6% significance and prefers the distortion expected from nu (e) oscillation effects. A two-neutrino oscillation analysis of the KamLAND data gives Deltam(2)=7.9(+0.6)(-0.5)x10(-5) eV(2). A global analysis of data from KamLAND and solar-neutrino experiments yields Deltam(2)=7.9(+0.6)(-0.5)x10(-5) eV(2) and tan((2)theta=0.40(+0.10)(-0.07), the most precise determination to date.     

Inverse beta decay in a nonequilibrium antineutrino flux from a nuclear reactor

The evolution of the reactor-antineutrino spectrum toward equilibrium above the inverse-beta-decay threshold during the reactor operating period and the decay of residual $\bar \nu _e $ radiation after reactor shutdown are considered. It is found that, under certain conditions, these processes can play a significant role in experiments seeking neutrino oscillations.     

New results for the production of Λ and Σhyperons in antineutrino scattering from protons

We obtain total and differential cross-sections for the strangeness changing charged current reactions ˉ + p → Λ + L ⁺ and ˉ + p → Σ⁰ + L ⁺ , where L is a charged lepton, either an electron, muon or tau. We do this by making use of the standard dipole form factors normally used and of the new form factors recently obtained from recoil proton measurements in electron-proton electromagnetic scattering. We also obtain the contributions of the individual form factors to the total and differential cross-sections for both sets of form factors. We find that the differential and total cross-sections for Λ production change only slightly between the two sets of form factors but that the differential and total cross-sections change substantially for Σ⁰ production. We discuss the possibility of distinguishing between the two cases for the experiments planned by the MINERν A Collaboration.     

First results from RHIC-PHENIX

The PHENIX experiment consists of a large detector system located at the newly commissioned relativistic heavy ion collider (RHIC) at the Brookhaven National Laboratory. The primary goal of the PHENIX experiment is to look for signatures of the QCD prediction of a deconfined high-energy-density phase of nuclear matter quark gluon plasma. PHENIX started data taking for Au+Au collisions at √sNN=130 GeV in June 2000. The signals from the beam-beam counter (BBC) and zero degree calorimeter (ZDC) are used to determine the centrality of the collision. A Glauber model reproduces the ZDC spectrum reasonably well to determine the participants in a collision. Charged particle multiplicity distribution from the first PHENIX paper is compared with the other RHIC experiment and the CERN, SPS results. Transverse momentum of photons are measured in the electro-magnetic calorimeter (EMCal) and preliminary results are presented. Particle identification is made by a time of flight (TOF) detector and the results show clear separation of the charged hadrons from each other. For the PHENXI Collaboration The word PHENIX is the abbreviation of Pioneering High Energy Nuclear Interaction Experiment.     

First results from the CRIS experiment

The ability to study rare isotopes with techniques such as mass spectrometry and laser spectroscopy is often prevented by low production rates and large isobaric contamination. This has necessitated the development of novel beam cleaning techniques that can efficiently isolate the isotope of interest. The Collinear Resonance Ionization Spectroscopy (CRIS) experiment at ISOLDE, achieves this by resonantly ionizing a bunched atom beam in a region of ultra high vacuum. This method is motivated by the need to measure the hyperfine structure and isotope shift at the extremes of isospin where typical production rates drop to 1 atom/s. The technique also offers the ability to purify an ion beam and even select long-lived isomeric states (> 1 ms) from the ground state, which can be subsequently studied by decay spectroscopy or mass spectrometry experiments. This paper will report on the successful commissioning of the CRIS beam line and the recent laser spectroscopy results and laser assisted nuclear decay spectroscopy on the neutron deficient francium isotopes.     

First results from STAR at RHIC

The Relativistic Heavy Ion Collider (RHIC) along with its complement of four experiments commenced operation for physics in the summer of 2000. Initial results on detector performance, preliminary physics results on hadron production, and the physics anticipated from the STAR experiment will be reported.     

First results from the ALICE experiment

The results from first series of measurements performed by the ALICE experiment at the LHC are presented. These measurements include the charged-particle pseudorapidity densities, multiplicity distributions and transverse momentum spectra obtained by analyzing the data collected in 2009 and 2010 in proton-proton collisions at three different center-of-mass energies of 0.9, 2.36, and 7 TeV. The results are compared to previous proton-antiproton data and to model predictions.     

First evidence for direct CP violation

The double ratio R of the relative decay rates of the short- and long-lived neutral kaons into two charged and two neutral pions was measured to be 0.980±0.004±0.005. The deviation of R from the CP violation in the transition of the CP-odd K₂ into two pions with ϵ′/ϵ=(3.3 ± 1.1)×10⁻³.     

First results from the CERN axion solar telescope

Hypothetical axionlike particles with a two-photon interaction would be produced in the sun by the Primakoff process. In a laboratory magnetic field ("axion helioscope"), they would be transformed into x-rays with energies of a few keV. Using a decommissioned Large Hadron Collider test magnet, the CERN Axion Solar Telescope ran for about 6 months during 2003. The first results from the analysis of these data are presented here. No signal above background was observed, implying an upper limit to the axion-photon coupling g(agamma)<1.16x10(-10) GeV-1 at 95% C.L. for m(a) less, similar 0.02 eV. This limit, assumption-free, is comparable to the limit from stellar energy-loss arguments and considerably more restrictive than any previous experiment over a broad range of axion masses.     

First results from STAR EbyE analysis at RHIC

I review the first STAR event-by-event analysis of <p _p > fluctuations, event multiplicity fluctuations and large-scale two-particle p _t correlations. Significant nonstatistical charge-independent and charge-dependent fluctuations and correlations are observed.     

First evidence for upsilon production by pions

We have measured the production of massive muon pairs in hadronic collisions at the CERN Super Proton Synchrotron (SPS). A clear signal of production of the ? resonance by π⁺ of 200 GeV/c and π^? of 200 and 280 GeV/c on a platinum target is observed.     

High sensitivity search for nu;e's from the sun and other sources at KamLAND

Data corresponding to a KamLAND detector exposure of 0.28 kton yr has been used to search for nu;(e)'s in the energy range 8.3相似文献   

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.     

First dark matter results from the XENON100 experiment

The XENON100 experiment, in operation at the Laboratori Nazionali del Gran Sasso in Italy, is designed to search for dark matter weakly interacting massive particles (WIMPs) scattering off 62 kg of liquid xenon in an ultralow background dual-phase time projection chamber. In this Letter, we present first dark matter results from the analysis of 11.17 live days of nonblind data, acquired in October and November 2009. In the selected fiducial target of 40 kg, and within the predefined signal region, we observe no events and hence exclude spin-independent WIMP-nucleon elastic scattering cross sections above 3.4 × 10??? cm2 for 55 GeV/c2 WIMPs at 90% confidence level. Below 20 GeV/c2, this result constrains the interpretation of the CoGeNT and DAMA signals as being due to spin-independent, elastic, light mass WIMP interactions.     

First evidence for chirality in Tc isotopes: Spectroscopy of 100Tc

Excited states in ¹⁰⁰Tc have been studied using the ⁹⁶Zr( ⁷Li, 3n) reaction at a beam energy of 27 MeV. In the present work, evidence has been found for a second I = 1 band decaying via several stretched dipole transitions to the previously known I = 1 negative-parity band. Comparison of these data with those in neighbouring nuclei and also against recently reported criteria for chiral bands in nuclei, suggests that the two structures can be interpreted as chiral partners. Core quasi-particle coupling model calculations show reasonable agreement with the data and generally support the chiral interpretation of the states.     

First results from the Freiburg electron beam ion trap FreEBIT

Initial tests from the Freiburg electron beam ion trap are reported. Highly charged ions of xenon, barium, tungsten and krypton have been observed with charge states up to 60+ by means of X-ray spectroscopy. The current status, upgrade and future experiments are outlined. This revised version was published online in August 2006 with corrections to the Cover Date.