573 research outputs found
Probing medium-induced jet splitting and energy loss in heavy-ion collisions
The nuclear modification of jet splitting in relativistic heavy-ion
collisions at RHIC and the LHC energies is studied based on the higher twist
formalism. Assuming coherent energy loss for the two splitted subjets, a
non-monotonic jet energy dependence is found for the nuclear modification of
jet splitting function: strongest modification at intermediate jet energies
whereas weaker modification for larger or smaller jet energies. Combined with
the smaller size and lower density of the QGP medium at RHIC than at the LHC,
this explains the CMS-STAR groomed jet puzzle -- strong nuclear modification of
the momentum sharing distribution at the LHC whereas no obvious
modification of the distribution at RHIC. In contrast, the observed
nuclear modification pattern of the groomed jet distribution cannot be
explained solely by independent energy loss of the two subjets. Our result may
be tested in future measurements of groomed jets with lower jet energies at the
LHC and larger jet energies at RHIC, for different angular separations between
the two subjets.Comment: 10 pages, 12 figure
Optimization of Treatment Geometry to Reduce Normal Brain Dose in Radiosurgery of Multiple Brain Metastases with Single-Isocenter Volumetric Modulated Arc Therapy
Treatment of patients with multiple brain metastases using a single-isocenter volumetric modulated arc therapy (VMAT) has been shown to decrease treatment time with the tradeoff of larger low dose to the normal brain tissue. We have developed an efficient Projection Summing Optimization Algorithm to optimize the treatment geometry in order to reduce dose to normal brain tissue for radiosurgery of multiple metastases with single-isocenter VMAT. The algorithm: (a) measures coordinates of outer boundary points of each lesion to be treated using the Eclipse Scripting Application Programming Interface, (b) determines the rotations of couch, collimator, and gantry using three matrices about the cardinal axes, (c) projects the outer boundary points of the lesion on to Beam Eye View projection plane, (d) optimizes couch and collimator angles by selecting the least total unblocked area for each specific treatment arc, and (e) generates a treatment plan with the optimized angles. The results showed significant reduction in the mean dose and low dose volume to normal brain, while maintaining the similar treatment plan qualities on the thirteen patients treated previously. The algorithm has the flexibility with regard to the beam arrangements and can be integrated in the treatment planning system for clinical application directly
Single Cell Optical Imaging and Spectroscopy
In his 1665 treatise, Micrographia, Robert Hooke described the many observations he had made using a microscope, including compartment-like structures in cork samples that he termed “cells
Physics perspectives of heavy-ion collisions at very high energy
Heavy-ion collisions at very high colliding energies are expected to produce
a quark-gluon plasma (QGP) at the highest temperature obtainable in a
laboratory setting. Experimental studies of these reactions can provide an
unprecedented range of information on properties of the QGP at high
temperatures. We report theoretical investigations of the physics perspectives
of heavy-ion collisions at a future high-energy collider. These include initial
parton production, collective expansion of the dense medium, jet quenching,
heavy-quark transport, dissociation and regeneration of quarkonia, photon and
dilepton production. We illustrate the potential of future experimental studies
of the initial particle production and formation of QGP at the highest
temperature to provide constraints on properties of strongly interaction
matter.Comment: 35 pages in Latex, 29 figure
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