228 research outputs found
Ekpyrosis and inflationary dynamics in heavy ion collisions: the role of quantum fluctuations
We summarize recent significant progress in the development of a
first-principles formalism to describe the formation and evolution of matter in
very high energy heavy ion collisions. The key role of quantum fluctuations
both before and after a collision is emphasized. Systematic computations are
now feasible to address early time dynamics essential to quantifying properties
of strongly interacting quark-gluon matter.Comment: Talk by R.V. at Quark Matter 2011, Annecy, France, May 23-28, 2011.
LaTex, 4 pages; v2, final version to appear in J. Phys.
Closing the Nuclear Fuel Cycle with a Simplified Minor Actinide Lanthanide Separation Process (ALSEP) and Additive Manufacturing
Expanded low-carbon baseload power production through the use of nuclear fission can be enabled by recycling long-lived actinide isotopes within the nuclear fuel cycle. This approach provides the benefits of (a) more completely utilizing the energy potential of mined uranium, (b) reducing the footprint of nuclear geological repositories, and (c) reducing the time required for the radiotoxicity of the disposed waste to decrease to the level of uranium ore from one hundred thousand years to a few hundred years. A key step in achieving this goal is the separation of long-lived isotopes of americium (Am) and curium (Cm) for recycle into fast reactors. To achieve this goal, a novel process was successfully demonstrated on a laboratory scale using a bank of 1.25-cm centrifugal contactors, fabricated by additive manufacturing, and a simulant containing the major fission product elements. Americium and Cm were separated from the lanthanides with over 99.9% completion. The sum of the impurities of the Am/Cm product stream using the simulated raffinate was found to be 3.2âĂâ10â3âg/L. The process performance was validated using a genuine high burnup used nuclear fuel raffinate in a batch regime. Separation factors of nearly 100 for 154Eu over 241Am were achieved. All these results indicate the process scalability to an engineering scale
The QCD Pomeron in ultraperipheral heavy ion collisions: III. Photonuclear production of heavy quarks
We calculate the photonuclear production of heavy quarks in ultraperipheral
heavy ion collisions. The integrated cross section and the rapidity
distribution are computed employing sound high energy QCD formalisms as the
collinear and semihard approaches as well as the saturation model. In
particular, the color glass condensate (CGC) formalism is also considered using
a simple phenomenological parameterization for the color field correlator in
the medium, which allow us to obtain more reliable estimates for charm and
bottom production at
LHC energies.Comment: 15 pages, 2 figures. Extended version to be published in Eur. Phys.
J.
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Aqueous Complexation of Thorium(IV), Uranium(IV), Neptunium(IV), Plutonium(III/IV), and Cerium(III/IV) with DTPA
Aqueous complexation of Th(IV), U(IV), Np(IV), Pu(III/IV), and Ce(III/IV) with DTPA was studied by potentiometry, absorption spectrophotometry, and cyclic voltammetry at 1 M ionic strength and 25 °C. The stability constants for the 1:1 complex of each trivalent and tetravalent metal were calculated. From the potentiometric data, we report stability constant values for Ce(III)DTPA, Ce(III)HDTPA, and Th(IV)DTPA of log ÎČâââ = 20.01 ± 0.02, log ÎČâââ = 22.0 ± 0.2, and log ÎČâââ = 29.6 ± 1, respectively. From the absorption spectrophotometry data, we report stability constant values for U(IV)DTPA, Np(IV)DTPA, and Pu(IV)DTPA of log ÎČâââ = 31.8 ± 0.1, 32.3 ± 0.1, and 33.67 ± 0.02, respectively. From the cyclic voltammetry data, we report stability constant values for Ce(IV) and Pu(III) of log ÎČâââ = 34.04 ± 0.04 and 20.58 ± 0.04, respectively. The values obtained in this work are compared and discussed with respect to the ionic radius of each cationic metal
The Physics of Ultraperipheral Collisions at the LHC
We discuss the physics of large impact parameter interactions at the LHC:
ultraperipheral collisions (UPCs). The dominant processes in UPCs are
photon-nucleon (nucleus) interactions. The current LHC detector configurations
can explore small hard phenomena with nuclei and nucleons at photon-nucleon
center-of-mass energies above 1 TeV, extending the range of HERA by a
factor of ten. In particular, it will be possible to probe diffractive and
inclusive parton densities in nuclei using several processes. The interaction
of small dipoles with protons and nuclei can be investigated in elastic and
quasi-elastic and production as well as in high
production accompanied by a rapidity gap. Several of these phenomena
provide clean signatures of the onset of the new high gluon density QCD regime.
The LHC is in the kinematic range where nonlinear effects are several times
larger than at HERA. Two-photon processes in UPCs are also studied. In
addition, while UPCs play a role in limiting the maximum beam luminosity, they
can also be used a luminosity monitor by measuring mutual electromagnetic
dissociation of the beam nuclei. We also review similar studies at HERA and
RHIC as well as describe the potential use of the LHC detectors for UPC
measurements.Comment: 229 Pages, 121 figure
Comments on two papers by Kapusta and Wong
We critically examine recently published results on the thermal production of
massive vector bosons in a quark-gluon plasma. We claim the production rate is
a collinear safe observable.Comment: 6 pages LATEX documen
QCD at small x and nucleus-nucleus collisions
At large collision energy sqrt(s) and relatively low momentum transfer Q, one
expects a new regime of Quantum Chromo-Dynamics (QCD) known as "saturation".
This kinematical range is characterized by a very large occupation number for
gluons inside hadrons and nuclei; this is the region where higher twist
contributions are as large as the leading twist contributions incorporated in
collinear factorization. In this talk, I discuss the onset of and dynamics in
the saturation regime, some of its experimental signatures, and its
implications for the early stages of Heavy Ion Collisions.Comment: Plenary talk given at QM2006, Shanghai, November 2006. 8 pages, 8
figure
The Quark-Gluon-Plasma Liquid
The quark-gluon plasma close to the critical temperature is a strongly
interacting system. Using strongly coupled, classical, non-relativistic plasmas
as an analogy, we argue that the quark-gluon plasma is in the liquid phase.
This allows to understand experimental observations in ultrarelativistic
heavy-ion collisions and to interpret lattice QCD results. It also supports the
indications of the presence of a strongly coupled QGP in ultrarelativistic
heavy-ion collisions.Comment: 8 pages, 2 figures, final version, to bepublished in J. Phys.
From Glasma to Quark Gluon Plasma in heavy ion collisions
When two sheets of Color Glass Condensate collide in a high energy heavy ion
collision, they form matter with very high energy densities called the Glasma.
We describe how this matter is formed, its remarkable properties and its
relevance for understanding thermalization of the Quark Gluon Plasma in heavy
ion collisions. Long range rapidity correlations contained in the near side
ridge measured in heavy ion collisions may allow one to directly infer the
properties of the Glasma.Comment: Plenary Topical Overview Talk, Quark Matter 2008; 10 pages 8 figure
Dijet production as a centrality trigger for p-p collisions at CERN LHC
We demonstrate that a trigger on hard dijet production at small rapidities
allows to establish a quantitative distinction between central and peripheral
collisions in pbar-p and p-p collisions at Tevatron and LHC energies. Such a
trigger strongly reduces the effective impact parameters as compared to minimum
bias events. This happens because the transverse spatial distribution of hard
partons (x >~ 10^{-2}) in the proton is considerably narrower than that of soft
partons, whose collisions dominate the total cross section. In the central
collisions selected by the trigger, most of the partons with x >~ 10^{-2}
interact with a gluon field whose strength rapidly increases with energy. At
LHC (and to some extent already at Tevatron) energies the strength of this
interaction approaches the unitarity ('black-body') limit. This leads to
specific modifications of the final state, such as a higher probability of
multijet events at small rapidities, a strong increase of the transverse
momenta and depletion of the longitudinal momenta at large rapidities, and the
appearance of long-range correlations in rapidity between the forward/backward
fragmentation regions. The same pattern is expected for events with production
of new heavy particles (Higgs, SUSY). Studies of these phenomena would be
feasible with the CMS-TOTEM detector setup, and would have considerable impact
on the exploration of the physics of strong gluon fields in QCD, as well as the
search for new particles at LHC.Comment: 17 pages, Revtex 4, 14 EPS figures. Expanded discussion of some
points, added 3 new figures and new references. Included comment on
connection with cosmic ray physics near the GZK cutoff. To appear in Phys Rev
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