1,889 research outputs found
Longitudinal spin transfer of Lambda and anti-Lambda in polarized pp collisions at \sqrt s=200 GeV at STAR
We report our measurement on longitudinal spin transfer, D_LL, from high
energy polarized protons to and hyperons in
proton-proton collisions at with the STAR detector at
RHIC. The current measurements cover , pseudorapidity
and transverse momenta up to using the data taken
in 2005. The longitudinal spin transfer is found to be D_LL= -0.03\pm 0.13
(stat) \pm 0.04(syst)\LambdaD_{LL} = -0.12 \pm
0.08(stat) \pm 0.03(syst)\bar{\Lambda} =
0.5 = 3.7 GeV/c$. The prospects with 2009 data and the future
measurements are also given.Comment: 6 pages, 3 figures, presentation at the SPIN2010 International
Symposium, Juelich (Germany), Sep. 27-Oct. 2, 201
Light delivery and light dosimetry for photodynamic therapy
Abstract
Photodynamic therapy (PDT) has attracted attention because it was considered to be a selective form of cancer treatment causing minimal damage to normal tissues. This is not exactly true, because the ratio between the photosensitizer concentrations in tumour and surrounding normal tissues is not always much more than one. Nevertheless, tumour destruction by PDT with relatively little damage to normal tissue is possible in many cases. This requires sophisticated light delivery and/or light dosimetry techniques. In this respect the limited penetration of light into biological tissues can sometimes be useful. In this paper a qualitative and sometimes quantitative discussion is given of the physical phenomena determining the energy fluence in a biological tissue. Most important is light scattering, the contribution of which depends on the geometrical conditions. Finite beam surface irradiation, irradiation of hollow organs (bladder) and interstitial irradiation are discussed separately. The emphasis is on light âdoseâ and light dose distribution. It is emphasized that PDT dosimetry in general is complicated by photosensitizer distribution (which is usually not known), by photobleaching of the sensitizer, by possible effects of hyperthermia, and by changes in optical properties during and as a result of PDT
In vivo action spectra, absorption and fluorescence excitation spectra of photosensitizers for photodynamic therapy
Global polarization measurement in Au+Au collisions
The system created in non central relativistic nucleus-nucleus collisions
carries large angular orbital momentum. Due to spin-orbital coupling, produced
particles could be globally polarized along the direction of the system angular
momentum. We present results of a measurement of Lambda hyperon global
polarization in Au+Au collisions at the center of mass energies 62 and 200 GeV
with the STAR detector at RHIC. The observed global polarization of Lambda
hyperons in the STAR acceptance is consistent with zero within the precision of
the measurement. The obtained upper limit, |P_Lambda| < 0.01, is significantly
below the theoretical values discussed recently in the literature.Comment: Talk given at SQM 2006, International Conference on Strangeness in
Quark Matter, March 26-31, 2006, Los Angeles CA; 4 pages, 2 figure
Particle dependence of elliptic flow in Au+Au collisions at 200 GeV
The elliptic flow parameter () for and
has been measured at mid-rapidity in Au + Au collisions at
GeV by the STAR collaboration. The values for both
and saturate at moderate , deviating
from the hydrodynamic behavior observed in the lower region. The
saturated values and the scales where the deviation begins are
particle dependent. The particle-type dependence of shows features
expected from the hadronization of a partonic ellipsoid by coalescence of
co-moving quarks. These results will be discussed in relation to the nuclear
modification factor () which has also been measured for and
by the STAR collaboration.Comment: 6 pages, 3 figures, Strange Quark Matter 2003 Conference (SQM 2003):
updated with 2 figures from original talk that did not appear in the journa
Multi-strange baryon production in Au+Au collisions at top RHIC energy as a probe of bulk properties
We report STAR preliminary results on multi-strange baryon production in
Au+Au collisions at sqrt(s_NN)=200 GeV at RHIC. Its implication for the
formation of a new state of matter is discussed. The system size dependence on
the production of strange baryons is investigated to study the onset of strange
quark equilibration in the medium. The nuclear modification factor of Lambda,
Xi and Omega is also presented. Its suppression at p_T>3 GeV/c supports the
formation of a dense interacting medium at RHIC. The spectra of multi-strange
baryons reveal that within a hydro-inspired model, they may decouple prior than
lighter particles and that their flow may be mostly developed at a partonic
level. This idea is emphasized by the measurement of the v_2 of Xi+AntiXi and
Omega+AntiOmega whose behaviour is close to the Lambda+AntiLambda baryon
elliptic flow in the intermediate p_T region where a constituent quark scaling
of v_2 is observed.Comment: 8 pages, 8 figures, Strange Quark Matter 2004 conference proceeding
Systematics of mid-rapidity K-/pi ratio in heavy-ion collisions
It is observed that K-/pi in A+A and possibly p+p and pbar+p collisions
follows an interesting systematic in omega, the pion transverse energy per unit
of rapidity and transverse overlap area. The systematics show a linear increase
of K-/pi with omega in the AGS and SPS energy regime and a saturation at RHIC
energy. The systematics indicate that omega might be the relevant variable
underlying K-/pi. At high energy, the omega variable is related to the gluon
saturation scale in high density QCD, and perhaps to the initial energy density
in the Bjorken picture.Comment: 4 pages, 3 figures. SQM-2001 proceeding
Space-time analysis of reaction at RHIC
Space-time information about the Au-Au collisions produced at RHIC are key
tools to understand the evolution of the system and especially assess the
presence of collective behaviors. Using a parameterization of the system's
final state relying on collective expansion, we show that pion source radii can
be tied together with transverse mass spectra and elliptic flow within the same
framework. The consistency between these different measures provide a solid
ground to understand the characteristics of collective flow and especially the
possible peculiar behavior of particles such as Xi, Omega or phi. The validity
of the short time scales that are extracted from fits to the pion source size
is also addressed. The wealth of new data that will soon be available from
Au-Au collisions at sqrt{s_{NN}} = 200 GeV, will provide a stringet test of the
space-time analysis framework developped in these proceedings.Comment: Invited talk given at the SQM2003 conference (March 2003), to be
published in Journal of Physics G. 10 pages, 3 figure
Reconstructed Jets at RHIC
To precisely measure jets over a large background such as pile up in high
luminosity p+p collisions at LHC, a new generation of jet reconstruction
algorithms is developed. These algorithms are also applicable to reconstruct
jets in the heavy ion environment where large event multiplicities are
produced. Energy loss in the medium created in heavy ion collisions are already
observed indirectly via inclusive hadron distributions and di-hadron
correlations. Jets can be used to study this energy loss in detail with reduced
biases. We review the latest results on jet-medium interactions as seen in A+A
collisions at RHIC, focusing on the recent progress on jet reconstruction in
heavy ion collisions.Comment: Proceedings for the 26th Winter Workshop on Nuclear Dynamic
Research Project as Boundary Object: negotiating the conceptual design of a tool for International Development
This paper reflects on the relationship between who one designs for and what one designs in the unstructured space of designing for political change; in particular, for supporting âInternational Developmentâ with ICT. We look at an interdisciplinary research project with goals and funding, but no clearly defined beneficiary group at start, and how amorphousness contributed to impact. The reported project researched a bridging tool to connect producers with consumers across global contexts and show players in the
supply chain and their circumstances. We explore how both the nature of the research and the toolâs function became contested as work progressed. To tell this tale, we invoke
the idea of boundary objects and the value of tacking back and forth between elastic meanings of the projectâs artefacts and processes. We examine the projectâs role in India, Chile and other arenas to draw out ways that it functioned as a catalyst and how absence of committed design choices acted as an unexpected strength in reaching its goals
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