514 research outputs found
Correlations in the Parton Recombination Model
We describe how parton recombination can address the recent measurement of
dynamical jet-like two particle correlations. In addition we discuss the
possible effect realistic light-cone wave-functions including higher
Fock-states may have on the well-known elliptic flow valence-quark number
scaling law.Comment: 4 pages, two figures, proceedings of the 18th International
Conference on Ultrarelativistic Nucleus-Nucleus Collisions: Quark Matter 2005
(QM 2005), Budapest, Hungary, 4-9 Aug 200
Thermal Recombination: Beyond the Valence Quark Approximation
Quark counting rules derived from recombination models agree well with data
on hadron production at intermediate transverse momenta in relativistic
heavy-ion collisions. They convey a simple picture of hadrons consisting only
of valence quarks. We discuss the inclusion of higher Fock states that add sea
quarks and gluons to the hadron structure. We show that, when recombination
occurs from a thermal medium, hadron spectra remain unaffected by the inclusion
of higher Fock states. However, the quark number scaling for elliptic flow is
somewhat affected. We discuss the implications for our understanding of data
from the Relativistic Heavy Ion Collider.Comment: 5 pages, 5 figure
On the 3-particle scattering continuum in quasi one dimensional integer spin Heisenberg magnets
We analyse the three-particle scattering continuum in quasi one dimensional
integer spin Heisenberg antiferromagnets within a low-energy effective field
theory framework. We exactly determine the zero temperature dynamical structure
factor in the O(3) nonlinear sigma model and in Tsvelik's Majorana fermion
theory. We study the effects of interchain coupling in a Random Phase
Approximation. We discuss the application of our results to recent
neutron-scattering experiments on the Haldane-gap material .Comment: 8 pages of revtex, 5 figures, small changes, to appear in PR
The scintillation and ionization yield of liquid xenon for nuclear recoils
XENON10 is an experiment designed to directly detect particle dark matter. It
is a dual phase (liquid/gas) xenon time-projection chamber with 3D position
imaging. Particle interactions generate a primary scintillation signal (S1) and
ionization signal (S2), which are both functions of the deposited recoil energy
and the incident particle type. We present a new precision measurement of the
relative scintillation yield \leff and the absolute ionization yield Q_y, for
nuclear recoils in xenon. A dark matter particle is expected to deposit energy
by scattering from a xenon nucleus. Knowledge of \leff is therefore crucial for
establishing the energy threshold of the experiment; this in turn determines
the sensitivity to particle dark matter. Our \leff measurement is in agreement
with recent theoretical predictions above 15 keV nuclear recoil energy, and the
energy threshold of the measurement is 4 keV. A knowledge of the ionization
yield \Qy is necessary to establish the trigger threshold of the experiment.
The ionization yield \Qy is measured in two ways, both in agreement with
previous measurements and with a factor of 10 lower energy threshold.Comment: 8 pages, 9 figures. To be published in Nucl. Instrum. Methods
A New Phase of Matter: Quark-Gluon Plasma Beyond the Hagedorn Critical Temperature
I retrace the developments from Hagedorn's concept of a limiting temperature
for hadronic matter to the discovery and characterization of the quark-gluon
plasma as a new state of matter. My recollections begin with the transformation
more than 30 years ago of Hagedorn's original concept into its modern
interpretation as the "critical" temperature separating the hadron gas and
quark-gluon plasma phases of strongly interacting matter. This was followed by
the realization that the QCD phase transformation could be studied
experimentally in high-energy nuclear collisions. I describe here my personal
effort to help develop the strangeness experimental signatures of quark and
gluon deconfinement and recall how the experimental program proceeded soon to
investigate this idea, at first at the SPS, then at RHIC, and finally at LHC.
As it is often the case, the experiment finds more than theory predicts, and I
highlight the discovery of the "perfectly" liquid quark-gluon plasma at RHIC. I
conclude with an outline of future opportunities, especially the search for a
critical point in the QCD phase diagram.Comment: To appear in {\em Melting Hadrons, Boiling Quarks} by Rolf Hagedorn
and Johan Rafelski (editor), Springer Publishers, 2015 (open access
Design and Performance of the XENON10 Dark Matter Experiment
XENON10 is the first two-phase xenon time projection chamber (TPC) developed
within the XENON dark matter search program. The TPC, with an active liquid
xenon (LXe) mass of about 14 kg, was installed at the Gran Sasso underground
laboratory (LNGS) in Italy, and operated for more than one year, with excellent
stability and performance. Results from a dark matter search with XENON10 have
been published elsewhere. In this paper, we summarize the design and
performance of the detector and its subsystems, based on calibration data using
sources of gamma-rays and neutrons as well as background and Monte Carlo
simulations data. The results on the detector's energy threshold, energy and
position resolution, and overall efficiency show a performance that exceeds
design specifications, in view of the very low energy threshold achieved (<10
keVr) and the excellent energy resolution achieved by combining the ionization
and scintillation signals, detected simultaneously
Dimerization and Incommensurate Spiral Spin Correlations in the Zigzag Spin Chain: Analogies to the Kondo Lattice
Using the density matrix renormalization group and a bosonization approach,
we study a spin-1/2 antiferromagnetic Heisenberg chain with near-neighbor
coupling and frustrating second-neighbor coupling , particularly in
the limit . This system exhibits both dimerization and
incommensurate spiral spin correlations. We argue that this system is closely
related to a doped, spin-gapped phase of the one-dimensional Kondo lattice.Comment: 18 pages, with 13 embedded encapsulated Postscript figures, uses
epsf.sty. Corrects a misstatement about the pitch angle, and contains
additional reference
Decoherence in trapped ions due to polarization of the residual background gas
We investigate the mechanism of damping and heating of trapped ions
associated with the polarization of the residual background gas induced by the
oscillating ions themselves. Reasoning by analogy with the physics of surface
electrons in liquid helium, we demonstrate that the decay of Rabi oscillations
observed in experiments on 9Be+ can be attributed to the polarization phenomena
investigated here. The measured sensitivity of the damping of Rabi oscillations
with respect to the vibrational quantum number of a trapped ion is also
predicted in our polarization model.Comment: 26 pdf pages with 5 figures, http://www.df.ufscar.br/~quantum
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