744 research outputs found
Characterization and analysis of azimuthally sensitive correlations
A unified framework for describing the azimuthal dependence of two-particle
correlations in heavy-ion collisions is introduced, together with the methods
for measuring the corresponding observables. The generalization to azimuthal
correlations between more than two particles is presented.Comment: 7 pages; talk given at Hot Quarks 2004, Taos (NM), July 18-24,200
H2O and Cl in deep crustal melts: the message of melt inclusions in metamorphic rocks
The use of NanoSIMS on primary melt inclusions in partially melted rocks is a powerful approach to clarify the budget of volatiles at depth during crust formation and its reworking. Anatectic melt inclusions are indeed gateways to quantify H2O, halogens and other species (e.g. CO2, N) partitioned into the deep partial melts generated during metamorphism of the continental crust. Here we present new datasets of NanoSIMS measurements of H2O and Cl in preserved melt inclusions from metamorphic rocks with different protoliths – magmatic or sedimentary – which underwent partial melting at different pressure–temperature–fluid conditions. These new datasets are then compared with similar data on natural anatectic melts available in the literature to date. Our study provides novel, precise constraints for the H2O content in natural melts formed at high pressure, a field previously investigated mostly via experiments. We also show that H2O heterogeneities in partial melts at the microscale are common, regardless of the rock protolith. Correlations between H2O contents and P–T values can be identified merging new and old data on anatectic inclusions via NanoSIMS. Overall, the data acquired so far indicate that silicate melt generation in nature always requires H2O, even for the hottest melts found so far (>1000 ∘C). Moreover, in agreement with previous work, preserved glassy inclusions always appear to be poorer in H2O than crystallized ones, regardless of their chemical system and/or P–T conditions of formation. Finally, this study reports the very first NanoSIMS data on Cl (often in amounts >1000 ppm) acquired in situ on natural anatectic melts, showing how anatectic melt inclusions – additionally to magmatic ones – may become a powerful tool to clarify the role of halogens in many geological processes, not only in crustal evolution but also in ore deposit formation.</p
The carbon budget of crustal reworking during continental collision: Clues from nanorocks and fluid inclusions
The source of volatiles in the continental crust is a long-standing issue. In addition to controlling the amount of melt generated during anatexis, H2O and CO2 budgets of the middle and lower siliciclastic crust are also of great importance for carbonate precipitation, ore concentration, orogenic degassing and carbon storage. Here we focus on two case studies of partially melted metamorphic rocks of crustal affinity– the Ivrea Zone in the Western Alps (0.8 GPa) and the Central Maine Terrane (1.8 GPa), USA. These terrains contain fluid inclusions and carbonbearing nanogranitoids (former melt inclusions) from which the H2O and CO2 content has been estimated via in-situ analyses. Thermodynamic modelling is used to quantify the amount of internally derived, mineral-bound
bulk rock CO2 necessary to reproduce the volatile contents of these melt inclusions. The minimum amount of bulk rock CO2 present at peak metamorphic conditions is estimated at 400 ppm for the Ivrea Zone and 3000 ppm for the Central Maine Terrane. This suggests that the flux of carbon associated with the burial of siliciclastic sediments in the lower crust during the Phanerozoic is 0.2–4.4 Mt. C/yr. These values, as well as the nature of the source of the deep crustal carbon might have changed with time, with periods dominated by internal reworking rather than external inputs. The protracted growth and differentiation of the continental crust through the reworking of supracrustal materials in continental collision settings is a key element of carbon storage processes. The stability of the continental crust through time provides an ultimate, long-lasting reservoir of carbon
Eccentricity fluctuations and elliptic flow at RHIC
Fluctuations in nucleon positions can affect the spatial eccentricity of the
overlap zone in nucleus-nucleus collisions. We show that elliptic flow should
be scaled by different eccentricities depending on which method is used for the
flow analysis. These eccentricities are estimated semi-analytically. When
is analyzed from 4-particle cumulants, or using the event plane from directed
flow in a zero-degree calorimeter, the result is shown to be insensitive to
eccentricity fluctuations.Comment: 5 pages, 3 eps figure
Anisotropic flow from Lee-Yang zeroes: a practical guide
We present a new method to analyze anisotropic flow from the genuine
correlation among a large number of particles, focusing on the practical
implementation of the method.Comment: 4 pages; contribution to Quark Matter 2004, Oakland, January 11-17,
200
Elliptic Flow Analysis at RHIC with the Lee-Yang Zeroes Method in a Relativistic Transport Approach
The Lee-Yang zeroes method is applied to study elliptic flow () in Au+Au
collisions at ~GeV, with the UrQMD model. In this transport
approach, the true event plane is known and both the nonflow effects and
event-by-event fluctuations exist. Although the low resolutions prohibit
the application of the method for most central and peripheral collisions, the
integral and differential elliptic flow from the Lee-Yang zeroes method agrees
with the exact values very well for semi-central collisions.Comment: 4 pages, 4 figure
Jet multiplicities as the QGP thermometer
It is proposed to use the energy behavior of mean multiplicities of jets
propagating in a nuclear medium as the thermometer of this medium during the
collision phases. The qualitative effects are demonstrated in the framework of
the fixed coupling QCD with account of jet quenching.Comment: Modify version of hep-ph/0509344, 3 figure
Elliptic flow and incomplete equilibration at RHIC
We argue that RHIC data, in particular those on the anisotropic flow
coefficients v_2 and v_4, suggest that the matter produced in the early stages
of nucleus-nucleus collisions is incompletely thermalized. We interpret the
parameter (1/S)(dN/dy), where S is the transverse area of the collision zone
and dN/dy the multiplicity density, as an indicator of the number of collisions
per particle at the time when elliptic flow is established, and hence as a
measure of the degree of equilibration. This number serves as a control
parameter which can be varied experimentally by changing the system size, the
centrality of the collision, or the beam energy. We provide predictions for
Cu-Cu collisions at RHIC as well as for Pb-Pb collisions at the LHC.Comment: 5 pages, 2 figures, minor correction
Probe for the strong parity violation effects at RHIC with three particle correlations
In non-central relativistic heavy ion collisions, \P-odd domains, which might
be created in the process of the collision, are predicted to lead to charge
separation along the system orbital momentum \cite{Kharzeev:2004ey}. An
observable, \P-even, but directly sensitive to the charge separation effect,
has been proposed in \cite{Voloshin:2004vk} and is based on 3-particle mixed
harmonics azimuthal correlations. We report the STAR measurements using this
observable for Au+Au and Cu+Cu collisions at =200 and 62 GeV.
The results are reported as function of collision centrality, particle
separation in rapidity, and particle transverse momentum. Effects that are not
related to parity violation but might contribute to the signal are discussed.Comment: 4 pages, Quark Matter 2008 Poster proceeding
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