120964777
New results from the KIMS experiment
The Korea Invisible Mass Search (KIMS) collaboration has performed experiments on dark matter searches and double beta decay searches at the Yangyang underground laboratory. Recent results of KIMS as well as the status of the R&D on various detectors are presented. For the WIMP search KIMS ruled out the recoil of 127I of DAMA signal region unambiguously and set the most stringent limit on spin dependent WIMP interactions in the case of pure proton coupling. New limits on neutrino-less double beta decays of 112Sn, 124Sn, 64Zn is also reported.
122861815
Beam test of the CsI(Tl) calorimeter for the BELLE detector at the KEK-B factory
We studied the performance of a prototype electromagnetic calorimeter for the BELLE detector at the KEK proton synchrotron for an energy range of 0.25-3.5 GeV. The prototype consisted of an array of 6 x 5 CsI(Tl) crystals with 30 cm length (16.2 radiation lengths) and about 6 cm x 6 cm cross section. The scintillation light of each CsI(Tl) crystal was read out by two large-area PIN photodiodes and charge-sensitive preamplifiers attached at the rear face of the crystal. We measured the energy and position resolution for electrons and the e/pi separation for two sets of matrix configurations: one corresponded to the center and the other to the edge of the barrel calorimeter. The overall performance measured by the test proves that the prototype calorimeter is satisfactory for the use in the BELLE detector.
122859309
Electromagnetic calorimeter trigger at Belle
The performance of CsI(Tl) electromagnetic calorimeter trigger system in the Belle experiment is described. Two kinds of trigger schemes have been taken into account, namely a total energy trigger and a cluster counting trigger which are complementary to each other. In addition, the system has provided the online/offline luminosity information using the Bhabha event trigger scheme. An upgrade of the trigger is discussed.
184667614
Current Status of RENO Experiment
119276928
Measurement of central exclusive $\pi^+ \pi^-$ production in $p\bar{p}$ collisions at $\sqrt{s} = 0.9$ and 1.96 TeV at CDF
We measure exclusive π+π- production in proton-antiproton collisions at center-of-mass energies s=0.9 and 1.96 TeV in the Collider Detector at Fermilab. We select events with two oppositely charged particles, assumed to be pions, with pseudorapidity |η|<1.3 and with no other particles detected in |η|<5.9. We require the π+π- system to have rapidity |y|<1.0. The production mechanism of these events is expected to be dominated by double pomeron exchange, which constrains the quantum numbers of the central state. The data are potentially valuable for isoscalar meson spectroscopy and for understanding the pomeron in a region of transition between nonperturbative and perturbative quantum chromodynamics. The data extend up to dipion mass M(π+π-)=5000  MeV/c2 and show resonance structures attributed to f0 and f2(1270) mesons. From the π+π- and K+K- spectra, we place upper limits on exclusive χc0(3415) production.
17082200
N-flation: Multifield inflationary dynamics and perturbations
We carry out numerical investigations of the dynamics and perturbations in the Nflation model of Dimopoulos et al. (2005). This model features large numbers of scalar fields with different masses, which can cooperate to drive inflation according to the assisted inflation mechanism. We extend previous work to include random initial conditions for the scalar fields, and explore the predictions for density perturbations and the tensor-to-scalar ratio. The tensor-to-scalar ratio depends only on the number of e-foldings and is independent of the number of fields, their masses, and their initial conditions. It therefore always has the same value as for a single massive field. By contrast, the scalar spectral index has significant dependence on model parameters. While normally multi-field inflation models make predictions for observable quantities which depend also on the unknown field initial conditions, we find evidence of a ‘thermodynamic’ regime whereby the predicted spectral index becomes independent of initial conditions if there are enough fields. Only in parts of parameter space where the mass spectrum of the fields is extremely densely packed is the model capable of satisfying the tight observational constraints from WMAP3 observations.
59400471
Summary of the 3rd International Workshop on a Far Detector in Korea for the J-PARC Beam
by the J-PARC conventional neutrino beam detected by a new large underground neutrino detector in Korea. In this paper, we highlight some of the most relevant findings of the workshop. The present neutrino physics program in Korea, focused at a reactor neutrino experiment RENO, and the state of the J-PARC neutrino beam, presently under construction at Tokai (Japan) for the T2K experiment, were reviewed at the workshop. Future long baseline neutrino experiments have the task to complete the present knowledge on the mixing parameters, possibly including the CP violating phase ‐. The measurements in RENO and T2K could indicate a non-vanishing µ13 angle, thereby ascertaining the 3◊3 nature of the lepton flavor mixing matrix. They may conclude that the simultaneous determination of the neutrino mass hierarchy and the CP violating phase is possible at a next generation long baseline experiment coupled to a high intensity conventional neutrino beam.
18940226
GALACTIC WARPS IN TRIAXIAL HALOS
We study the behavior of galactic disks in triaxial halos both numerically and analytically to see if warps can be excited and sustained in triaxial potentials. We consider the following two scenarios: (1) galactic disks that are initially tilted relative to the equatorial plane of the halo (for a pedagogical purpose), and (2) tilted infall of dark matter relative to the equatorial plane of the disk and the halo. With numerical simulations of 100,000 disk particles in a fixed halo potential, we find that in triaxial halos, warps can be excited and sustained just as in spherical or axisymmetric halos but they show some oscillatory behavior and even can be transformed to a polar-ring system if the halo has a prolate-like triaxiality. The nonaxisymmetric component of the halo causes the disk to nutate, and the differential nutation between the inner and outer parts of the disk generally makes the magnitude of the warp slightly diminish and fluctuate. We also find that warps are relatively weaker in oblate and oblate-like triaxial halos, and since these halos are the halo configurations of disk galaxies inferred by cosmological simulations, our results are consistent with the fact that most of the observed warps are quite weak. We derive approximate formulae for the torques exerted on the disk by the triaxial halo and the dark matter torus, and with these formulae we successfully describe the behavior of the disks in our simulations. The techniques used in deriving these formulae could be applied for realistic halos with more complex structures.