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Search Results: 1 - 10 of 401314 matches for " Leitch M "
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RHIC Results on J/Psi
M. J. Leitch
Physics , 2007, DOI: 10.1088/0954-3899/34/8/S34
Abstract: Quarkonia ($J/\psi$, $\psi$', $\Upsilon$) production provides a sensitive probe of gluon distributions and their modification in nuclei; and is a leading probe of the hot-dense (deconfined) matter created in high-energy collisions of heavy ions. We will discuss the current understanding of the production process and of the cold-nuclear-matter effects that modify this production in nuclei in the context of recent p+p and p(d)+A quarkonia measurements. Then we will review the latest results for nucleus-nucleus collisions from RHIC, and together with the baseline results from d+A and p+p collisions, discuss several alternative explanations for the observed suppressions and future prospects for distinguishing these different pictures.
Quarkonia production at RHIC
M. J. Leitch
Physics , 2006, DOI: 10.1088/0954-3899/32/12/S48
Abstract: Quarkonia (J/Psi, Psi', Upsilon) production provides a sensitive probe of gluon distributions and their modification in nuclei; and is a leading probe of the hot-dense (deconfined) matter created in high-energy collisions of heavy ions. I will discuss our current understanding of the modification of gluon distributions in nuclei and other cold-nuclear-matter effects in the context of recent p-p and p(d)-A quarkonia measurements. Then I will review the latest results for nucleus-nucleus collisions from RHIC, and together with the baseline results from d-A and p-p collisions, discuss several alternative explanations for the observed suppressions and future prospects for distinguishing these different pictures.
Overview of Charm Physics at RHIC
M. J. Leitch
Physics , 2006, DOI: 10.1063/1.2714429
Abstract: Heavy-quark production provides a sensitive probe of the gluon structure of nucleons and its modication in nuclei. It is also a key probe of the hot-dense matter created in heavy-ion collisions. We will discuss the physics issues involved, as seen in quarkonia and open heavy-quark production, starting with those observed in proton-proton collisions. Then cold nuclear matter effects on heavy-quark production including shadowing, gluon saturation, energy loss and absorption will be reviewed in the context of recent proton-nucleus and deuteron-nucleus measurements. Next we survey the most recent measurements of open-charm and J/Psi's in heavy-ion collisions at RHIC and their interpretation. We discuss the high-pT suppression and flow of open charm in terms of energy loss and thermalization and, for J/Psi, contrast explanations in terms of screening in a deconfined medium vs. recombination models.
Latest Results on the Hot-Dense Partonic Matter at RHIC
M. J. Leitch
Physics , 2006, DOI: 10.1140/epja/i2006-10240-4
Abstract: At the Relativistic Heavy Ion Collider (RHIC) collisions of heavy ions at nucleon-nucleon energies of 200 GeV appear to have created a new form of matter thought to be a deconfined state of the partons that ordinarily are bound in nucleons.We discuss the evidence that a thermalized partonic medium, usually called a Quark Gluon Plasma (QGP), has been produced. Then we discuss the effect of this high-density medium on the production of jets and their pair correlations. Next we look at direct photons as a clean electro-magnetic probe to constrain the initial hard scatterings. Finally we review the developing picture for the effect of this medium on the production of open heavy quarks and on the screening by the QGP of heavy-quark bound states.
Progress Towards Understanding Quarkonia at PHENIX
M. J. Leitch,for the PHENIX Collaboration
Physics , 2008,
Abstract: Quarkonia (J/psi, psi', chi_C, Upsilon) production provides a sensitive probe of gluon distributions and their modification in nuclei; and is a leading probe of the hot-dense (deconfined) matter created in high-energy collisions of heavy ions. We will discuss the physics of quarkonia production in the context of recent p+p measurements at PHENIX. We next discuss Cold-Nuclear Matter (CNM) effects as seen in our measurements in $d+Au$ collisions - both for intrinsic physics such as gluon saturation and final-state dissociation, and as a baseline for studies in nucleus-nucleus collisions. Then we review the latest nucleus-nucleus results in the light of the expected CNM effects, and discuss two leading scenarios for the observed suppression patterns. Finally we show the latest data from PHENIX, including new d+Au data from the 2007-2008 run; and then look into the future.
Mass Extinctions and The Sun's Encounters with Spiral Arms
Erik M. Leitch,Gautam Vasisht
Physics , 1998, DOI: 10.1016/S1384-1076(97)00044-4
Abstract: The terrestrial fossil record shows that the exponential rise in biodiversity since the Precambrian period has been punctuated by large extinctions, at intervals of 40 to 140 Myr. These mass extinctions represent extremes over a background of smaller events and the natural process of species extinction. We point out that the non-terrestrial phenomena proposed to explain these events, such as boloidal impacts (a candidate for the end-Cretaceous extinction), and nearby supernovae, are collectively far more effective during the solar system's traversal of spiral arms. Using the best available data on the location and kinematics of the Galactic spiral structure (including distance scale and kinematic uncertainties), we present evidence that arm crossings provide a viable explanation for the timing of the large extinctions.
The Discovery of Anomalous Microwave Emission
Erik M. Leitch,A. C. R. Readhead
Advances in Astronomy , 2013, DOI: 10.1155/2013/352407
Abstract:
The Basics of Physician Compensation
Khristinn K. Leitch,Paul M. Walker
University of Toronto Medical Journal , 1999, DOI: 10.5015/utmj.v77i1.1129
Abstract:
Relative efficacy of organic manures in spring barley (Hordeum vulgare L. ) production
Ofosu-Anim J,Leitch M
Australian Journal of Crop Science , 2009,
Abstract: The effect of organic sources of nutrients on the growth of spring barley (Hordeum vulgare L.) was studied in a pot experiment in a heated glasshouse at the University of Wales, Aberyswyth from November 2006 to March 2007. Spring barley seeds were sown in 120 pots containing a mixture of peat and 180g dry weight of poultry manure, cowdung, chicken manure pellet, sheep manure and horse manure. Chicken manure pellet was applied at 3.0 g pot-1 as top dressing. Mineralization pattern of the organic manures was monitored in a parallel experiment with 24 pots containing only the growth media. In this study, organic manures significantly increased plant height and chlorophyll content of leaves over the control plants. The application of inorganic fertilizer increased plant height over chicken manure and compost. In addition chlorophyll content was higher with inorganic fertilizer than cowdung at six weeks after germination. N mineralization significantly varied among organic manure sources with compost having the highest mineralized N and sheep manure the least. Plant tissue analysis revealed significant differences in plant tissue nutrient composition under organic manure treatment. Growing plants in organic manure resulted in 1.2 to1.6-folds, 1.1 to 4-fold and 1.1 to 4.1-fold increases in total N content of plant tissue at four weeks, eight weeks and twelve weeks after germination, respectively. Dry matter production by plants was also significantly increased under organic manure treatments. Organic manure application had the potential of increasing spring barley yield by 1.5 to 4-fold. Cowdung appeared to be the best source of organic manure for spring barley production.
The Discovery of Anomalous Microwave Emission
Erik M. Leitch,A. C. R. Readhead
Advances in Astronomy , 2013, DOI: 10.1155/2013/352407
Abstract: We discuss the first detection of anomalous microwave emission, in the Owens Valley RING5M experiment, and its interpretation in the context of the ground-based cosmic microwave background (CMB) experiments of the early 1990s. The RING5M experiment was one of the first attempts to constrain the anisotropy power on sub-horizon scales, by observing a set of -size fields around the North Celestial Pole (NCP). Fields were selected close to the NCP to allow continuous integration from the Owens Valley site. The experiment detected significant emission at both 14.5?GHz and 30?GHz, consistent with a mixture of CMB and a flat-spectrum foreground component, which we termed anomalous, as it could be explained neither by thermal dust emission, nor by standard models for synchrotron or free-free emission. A significant spatial correlation was found between the extracted foreground component and structure in the IRAS 100?μm maps. While microwave emission from spinning dust may be the most natural explanation for this correlation, spinning dust is unlikely to account for all of the anomalous emission seen in the RING5M data. 1. Introduction From the perspective of the 21st century cosmology, it can be hard to imagine how primitive the state of our knowledge was a short twenty years ago and how rapidly the landscape was changing at the time. Today, ground-based experiments like the South Pole Telescope (SPT) and the Atacama Cosmology Telescope (ACT) have measured the high- power spectrum with enough resolution to detect the first nine Doppler peaks (SPT [1, 2], ACT [3]) and enough sensitivity to detect the background of SZ power from unresolved galaxy clusters [4]. The combination of ground, balloon-borne, and space-based missions have already determined fundamental cosmological parameters to uncertainties of a few percent (c.f. DASI [5], ACBAR [6], Boomerang [7], WMAP [8]), and new data from Planck are poised to refine these further. The E-mode polarization of the CMB, whose detection was unthinkable twenty years ago, is now routinely measured by ground-based experiments (first detected by DASI [9, 10], with progressive improvements in resolution and sensitivity by CBI [11], QUaD [12], BICEPI [13], and QUIET [14]), while ever more sensitive limits on the B-mode power spectrum are beginning to place interesting constraints on the tensor-to-scalar ratio [13] (with the next generation cameras like SPTpol, BICEPII, the Keck Array, PolarBear, and ACTpol already in operation). By contrast, the early 1990s had just witnessed the first ever detection of CMB anisotropy on
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