18,243 research outputs found
Jets associated with Z^0 boson production in heavy-ion collisions at the LHC
The heavy ion program at the LHC will present unprecedented opportunities to
probe hot QCD matter, that is, the quark gluon plasma (QGP). Among these
exciting new probes are high energy partons associated with the production of a
Z^0 boson, or Z^0 tagged jets. Once produced, Z^0 bosons are essentially
unaffected by the strongly interacting medium produced in heavy-ion collisions,
and therefore provide a powerful signal of the initial partonic energy and
subsequent medium induced partonic energy loss. When compared with theory,
experimental measurements of Z^0 tagged jets will help quantify the jet
quenching properties of the QGP and discriminate between different partonic
energy loss formalisms. In what follows, I discuss the advantages of tagged
jets over leading particles, and present preliminary results of the production
and suppression of Z^0 tagged jets in relativistic heavy-ion collisions at LHC
energies using the Guylassy-Levai-Vitev (GLV) partonic energy loss formalism.Comment: To appear in the proceedings of the 2010 Winter Workshop on Nuclear
Dynamics, which was held in Ocho Rios, Jamaica, mon
A Toy Model of Flying Snake's Glide
We have developed a toy model of flying snake's glide [J.J. Socha, Nature
vol. 418 (2002) 603.] by modifying a model for a falling paper. We have found
that asymmetric oscillation is a key about why snake can glide. Further
investigation for snake's glide will provide us details about how it can glide
without a wing.Comment: 6 pages, to be submitted to J. Phys. Soc. Jpn. Revised Version
submitted to the abov
Comparison of BES measurements of ion-scale turbulence with direct, gyrokinetic simulations of MAST L-mode plasmas
Observations of ion-scale (k_y*rho_i <= 1) density turbulence of relative
amplitude dn_e/n_e <= 0.2% are available on the Mega Amp Spherical Tokamak
(MAST) using a 2D (8 radial x 4 poloidal channel) imaging Beam Emission
Spectroscopy (BES) diagnostic. Spatial and temporal characteristics of this
turbulence, i.e., amplitudes, correlation times, radial and perpendicular
correlation lengths and apparent phase velocities of the density contours, are
determined by means of correlation analysis. For a low-density, L-mode
discharge with strong equilibrium flow shear exhibiting an internal transport
barrier (ITB) in the ion channel, the observed turbulence characteristics are
compared with synthetic density turbulence data generated from global,
non-linear, gyro-kinetic simulations using the particle-in-cell (PIC) code
NEMORB. This validation exercise highlights the need to include increasingly
sophisticated physics, e.g., kinetic treatment of trapped electrons,
equilibrium flow shear and collisions, to reproduce most of the characteristics
of the observed turbulence. Even so, significant discrepancies remain: an
underprediction by the simulations of the turbulence amplituide and heat flux
at plasma periphery and the finding that the correlation times of the
numerically simulated turbulence are typically two orders of magnitude longer
than those measured in MAST. Comparison of these correlation times with various
linear timescales suggests that, while the measured turbulence is strong and
may be `critically balanced', the simulated turbulence is weak.Comment: 27 pages, 11 figure
V1647 Ori (IRAS 05436-0007) in Outburst: the First Three Months
We report on photometric (BVRIJHK) and low dispersion spectroscopic
observations of V1647 Ori, the star that drives McNeil's Nebula, between 10
February and 7 May 2004. The star is photometrically variable atop a general
decline in brightness of about 0.3-0.4 magnitudes during these 87 days. The
spectra are featureless, aside from H-alpha and the Ca II infrared triplet in
emission, and a Na I D absorption feature. The Ca II triplet line ratios are
typical of young stellar objects. The H-alpha equivalent width may be modulated
on a period of about 60 days. The post-outburst extinction appears to be less
than 7 mag. The data are suggestive of an FU Orionis-like event, but further
monitoring will be needed to definitively characterize the outburst.Comment: Accepted for publication in the Astronomical Journa
Ohm's Law for a Relativistic Pair Plasma
We derive the fully relativistic Ohm's law for an electron-positron plasma.
The absence of non-resistive terms in Ohm's law and the natural substitution of
the 4-velocity for the velocity flux in the relativistic bulk plasma equations
do not require the field gradient length scale to be much larger than the
lepton inertial lengths, or the existence of a frame in which the distribution
functions are isotropic.Comment: 12 pages, plain TeX, Phys. Rev. Lett. 71 3481 (1993
Learning through social spaces: migrant women and lifelong learning in post-colonial London
This article shows how migrant women engage in learning through social spaces. It argues that such spaces are little recognised, and that there are multiple ways in which migrant women construct and negotiate their informal learning through socialising with other women in different informal modes. Additionally, the article shows how learning is shaped by the socio-political, geographical and multicultural context of living in London, outlining ways in which gendered and racialised identities shape, construct and constrain participation in lifelong learning. The article shows that one way in which migrant women resist (post)colonial constructions of difference is by engaging in informal and non-formal lifelong learning, arguing that the benefits are (at least) two-fold. The women develop skills (including language skills) but also use their informal learning to develop what is referred to in this article as 'relational capital'. The article concludes that informal lifelong learning developed through social spaces can enhance a sense of belonging for migrant women
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