60 research outputs found
Towards Jetography
As the LHC prepares to start taking data, this review is intended to provide
a QCD theorist's understanding and views on jet finding at hadron colliders,
including recent developments. My hope is that it will serve both as a primer
for the newcomer to jets and as a quick reference for those with some
experience of the subject. It is devoted to the questions of how one defines
jets, how jets relate to partons, and to the emerging subject of how best to
use jets at the LHC.Comment: 95 pages, 28 figures, an extended version of lectures given at the
CTEQ/MCNET school, Debrecen, Hungary, August 2008; v2 includes additional
discussion in several places, as well as other clarifications and additional
references
Planck 2018 results. XII. Galactic astrophysics using polarized dust emission
We present 353 GHz full-sky maps of the polarization fraction p, angle \u3c8, and dispersion of angles S of Galactic dust thermal emission produced from the 2018 release of Planck data. We confirm that the mean and maximum of p decrease with increasing NH. The uncertainty on the maximum polarization fraction, pmax=22.0% at 80 arcmin resolution, is dominated by the uncertainty on the zero level in total intensity. The observed inverse behaviour between p and S is interpreted with models of the polarized sky that include effects from only the topology of the turbulent Galactic magnetic field. Thus, the statistical properties of p, \u3c8, and S mostly reflect the structure of the magnetic field. Nevertheless, we search for potential signatures of varying grain alignment and dust properties. First, we analyse the product map S
7p, looking for residual trends. While p decreases by a factor of 3--4 between NH=1020 cm 122 and NH=2
71022 cm 122, S
7p decreases by only about 25%, a systematic trend observed in both the diffuse ISM and molecular clouds. Second, we find no systematic trend of S
7p with the dust temperature, even though in the diffuse ISM lines of sight with high p and low S tend to have colder dust. We also compare Planck data with starlight polarization in the visible at high latitudes. The agreement in polarization angles is remarkable. Two polarization emission-to-extinction ratios that characterize dust optical properties depend only weakly on NH and converge towards the values previously determined for translucent lines of sight. We determine an upper limit for the polarization fraction in extinction of 13%, compatible with the pmax observed in emission. These results provide strong constraints for models of Galactic dust in diffuse gas
Planck 2018 results. XII. Galactic astrophysics using polarized dust emission
We present 353 GHz full-sky maps of the polarization fraction , angle , and dispersion of angles of Galactic dust thermal emission produced from the 2018 release of Planck data. We confirm that the mean and maximum of decrease with increasing . The uncertainty on the maximum polarization fraction, % at 80 arcmin resolution, is dominated by the uncertainty on the zero level in total intensity. The observed inverse behaviour between and is interpreted with models of the polarized sky that include effects from only the topology of the turbulent Galactic magnetic field. Thus, the statistical properties of , , and mostly reflect the structure of the magnetic field. Nevertheless, we search for potential signatures of varying grain alignment and dust properties. First, we analyse the product map , looking for residual trends. While decreases by a factor of 3--4 between cm and cm, decreases by only about 25%, a systematic trend observed in both the diffuse ISM and molecular clouds. Second, we find no systematic trend of with the dust temperature, even though in the diffuse ISM lines of sight with high and low tend to have colder dust. We also compare Planck data with starlight polarization in the visible at high latitudes. The agreement in polarization angles is remarkable. Two polarization emission-to-extinction ratios that characterize dust optical properties depend only weakly on and converge towards the values previously determined for translucent lines of sight. We determine an upper limit for the polarization fraction in extinction of 13%, compatible with the observed in emission. These results provide strong constraints for models of Galactic dust in diffuse gas
Mise en forme analytique de courbes et de surfaces fermées
Representation of plane curves or tridimensionnal surfaces by coordinates sets needs a high amount of numerical data. We propose a procedure based upon the least mean square method which minimizes the final number of useful data. We give some elementary examples and we suggest some other applications and ways of method developing.Les représentations de courbes ou de surfaces gauches par ensembles de coordonnées obtenues expérimentalement mobilisent un nombre élevé de données numériques. On propose une procédure basée sur la méthode des moindres carrés et minimisant le nombre final de données utiles. On donne des exemples simples et on suggÚre quelques autres applications possibles ainsi que des voies de développement de la méthode
Mise en forme analytique de courbes et de surfaces fermées
Les représentations de courbes ou de surfaces gauches par ensembles de coordonnées obtenues expérimentalement mobilisent un nombre élevé de données numériques. On propose une procédure basée sur la méthode des moindres carrés et minimisant le nombre final de données utiles. On donne des exemples simples et on suggÚre quelques autres applications possibles ainsi que des voies de développement de la méthode
Synthesis and crystal structure of a new potassium fluorotellurate (IV) : KTe2F9
International audienc
- âŠ