12,592 research outputs found
Beyond the Standard Model with Precision Nucleon Matrix Elements on the Lattice
Precision measurements of nucleons provide constraints on the Standard Model
and can discern the signatures predicted for particles beyond the Standard
Model (BSM). Knowing the Standard Model inputs to nucleon matrix elements will
be necessary to constrain the couplings of dark matter candidates such as the
neutralino, to relate the neutron electric dipole moment to the CP-violating
theta parameter, or to search for new TeV-scale particles though non-
interactions in neutron beta decay. However, these matrix elements derive from
the properties of quantum chromodynamics (QCD) at low energies, where
perturbative treatments fail. Using lattice gauge theory, we can
nonperturbatively calculate the QCD path integral on a supercomputer. In this
proceeding, I will discuss a few representative areas in which lattice QCD
(LQCD) can contribute to the search for BSM physics, emphasizing suppressed
operators in neutron decay, and outline prospects for future development.Comment: 3 pages, 2 figures, talk presented at the 19th Particles and Nuclei
International Conference (PANIC 2011), Massachusetts Institute of Technology,
Cambridge, MA, USA, July 24-29, 201
Charmed spectroscopy from a nonperturbatively determined relativistic heavy quark action in full QCD
We present a preliminary calculation of the charmed meson spectrum using the
2+1 flavor domain wall fermion lattice configurations currently being generated
by the RBC and UKQCD collaborations. The calculation is performed using the
3-parameter, relativistic heavy quark action with nonperturbatively determined
coefficients. We will also demonstrate a step-scaling procedure for determining
these coefficients nonperturbatively using a series of quenched, gauge field
ensembles generated for three different lattice spacings.Comment: Proceeding for 24th International Symposium on Lattice Field Theory
(Lattice 2006), Tucson, Arizona, 23-28 Jul 200
Invasion of a littoral cladoceran Sida crystallina into the pelagic zone of Christine Lake, NH and its potential impact on the phytoplankton community
This study evaluated the phytoplankton community and grazing influences of the zooplankton in oligotrophic Christine Lake, NH, by assessing the body size and clearance rates of the three dominant crustaceans: Sida crystallina (0.08 individuals L-1 ), Daphnia dubia (0.11 individuals L-1 ), and Leptodiaptomus sicilis (2.11 individuals L-1 ). Sida crystallina, typically a littoral cladoceran, was abundant throughout the water column in the open water, and contributed approximately 44% of the grazing in the pelagic zone. Phytoplankton abundance was examined to assess the potential impact S. crystallina might have on the phytoplankton in Christine lake. Aphanocapsa, the dominant phytoplankton in Christine Lake (relative abundance 68.54%), is a picocyanobacterium capable of forming colonies in the presence of planktonic grazers. Its ability to out-compete other phytoplankton due to differential grazing pressure suggests the appearance of the strong grazer S. crystallina may have contributed to the dominance of cyanobacteria in this oligotrophic lake
Physics Results From Alpha Magnetic Spectrometer 1998 Shuttle Flight
The Alpha Magnetic Spectrometer (AMS) is a particle detector designed to
detect antimatter. During the 10-day test flight on the space shuttle in June
1998, AMS detected events. Upon analysis, no antimatter was found and
the antimatter limit was reduced to . The proton spectrum
shows some differences with the cosmic ray flux used in atmospheric neutrino
simulation. A large amount of protons, positrons, and electrons were found
below the geomagnetic rigidity cutoff. The energy of these particles are as
high as several GeV, one order of magnitude higher than any previously measured
energy in radiation belts. These particles also exhibit many interesting
features. This paper reviews the results in the four published papers of the
AMS collaboration and provides explanation for some features of the albedo
particles.Comment: 14 pages, 20 figures, The 7-th Taiwan Astrophysics Worksho
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