25,459 research outputs found
Femtoscopic results in Au+Au and p+p from PHENIX at RHIC
Ultra-relativistic gold-gold and proton-proton collisions are investigated in
the experiments of the Relativistic Heavy Ion Collider (RHIC). In the last
several years large amount of results were revealed about the matter created in
these collisions. The latest PHENIX results for femtoscopy and correlations are
reviewed in this paper. Bose-Einstein correlations of charged kaons in 200 GeV
Au+Au collisions and of charged pions in 200 GeV p+p collisions are shown. They
are both compatible with previous measurements of charged pions in gold-gold
collisions, with respect to transverse mass or number of participants scaling.Comment: Talk given at the VI Workshop on Particle Correlations and
Femtoscopy, Kiev, September 14-18, 2010. 6 pages, 4 figures. This work was
supported by the OTKA grant NK73143 and M. Csanad's Bolyai scholarshi
Measurement of light mesons at RHIC by the PHENIX experiment
The PHENIX experiment at RHIC has measured a variety of light neutral mesons
(, K, , , , ) via
multi-particle decay channels over a wide range of transverse momentum. A
review of the recent results on the production rates of light mesons in p+p and
their nuclear modification factors in d+Au, Cu+Cu and Au+Au collisions at
different energies is presented.Comment: 5 pages, 4 figures, talk given at Hard Probes 2008 conference in La
Toja, Spain. submitted to EPJ
Non-colliding Brownian Motions and the extended tacnode process
We consider non-colliding Brownian motions with two starting points and two
endpoints. The points are chosen so that the two groups of Brownian motions
just touch each other, a situation that is referred to as a tacnode. The
extended kernel for the determinantal point process at the tacnode point is
computed using new methods and given in a different form from that obtained for
a single time in previous work by Delvaux, Kuijlaars and Zhang. The form of the
extended kernel is also different from that obtained for the extended tacnode
kernel in another model by Adler, Ferrari and van Moerbeke. We also obtain the
correlation kernel for a finite number of non-colliding Brownian motions
starting at two points and ending at arbitrary points.Comment: 38 pages. In the revised version a few arguments have been expanded
and many typos correcte
Nuclear modification at sqrt{s_{NN}}=17.3 GeV, measured at NA49
Transverse momentum spectra up to 4.5 GeV/c were measured around midrapidity
in Pb+Pb reactions at sqrt{s_{NN}}=17.3 GeV, for pi^{+/-}, p, pbar and K^{+/-},
by the NA49 experiment. The nuclear modification factors R_{AA}, R_{AA/pA} and
R_{CP} were extracted and are compared to RHIC results at sqrt{s_{NN}}=200 GeV.
The modification factor R_{AA} shows a rapid increase with transverse momentum
in the covered region. The modification factor R_{CP} shows saturation well
below unity in the pi^{+/-} channel. The extracted R_{CP} values follow the 200
GeV RHIC results closely in the available transverse momentum range for all
particle species. For pi^{+/-} above 2.5 GeV/c transverse momentum, the
measured suppression is smaller than that observed at RHIC. The nuclear
modification factor R_{AA/pA} for pi^{+/-} stays well below unity.Comment: Proceedings of Quark Matter 2008 conferenc
Phonon-modulated magnetic interactions and spin Tomonaga-Luttinger liquid in the p-orbital antiferromagnet CsO2
The magnetic response of antiferromagnetic CsO2, coming from the p-orbital
S=1/2 spins of anionic O2- molecules, is followed by 133Cs nuclear magnetic
resonance across the structural phase transition occuring at Ts1=61 K on
cooling. Above Ts1, where spins form a square magnetic lattice, we observe a
huge, nonmonotonic temperature dependence of the exchange coupling originating
from thermal librations of O2- molecules. Below Ts1, where antiferromagnetic
spin chains are formed as a result of p-orbital ordering, we observe a spin
Tomonaga-Luttinger-liquid behavior of spin dynamics. These two interesting
phenomena, which provide rare simple manifestations of the coupling between
spin, lattice and orbital degrees of freedom, establish CsO2 as a model system
for molecular solids.Comment: 9 pages, 5 figures (with Supplemental Material), to appear in
Physical Review Letter
Brane Effects on Extra Dimensional Scenarios: A Tale of Two Gravitons
We analyze the propagation of a scalar field in multidimensional theories
which include kinetic corrections in the brane, as a prototype for
gravitational interactions in a four dimensional brane located in a (nearly)
flat extra dimensional bulk. We regularize the theory by introducing an
infrared cutoff given by the size of the extra dimensions and a physical
ultraviolet cutoff of the order of the fundamental Planck scale in the higher
dimensional theory. We show that, contrary to recent suggestions, the radius of
the extra dimensions cannot be arbitrarily large. Moreover, for finite radii,
the gravitational effects localized on the brane can substantially alter the
phenomenology of collider and/or table-top gravitational experiments. This
phenomenology is dictated by the presence of a massless graviton, with standard
couplings to the matter fields, and a massive graviton which couples to matter
in a much stronger way. While graviton KK modes lighter than the massive
graviton couple to matter in a standard way, the couplings to matter of the
heavier KK modes are strongly suppressed.Comment: 21 pages, latex2e, axodraw.sty, 2 figure
Billiard algebra, integrable line congruences, and double reflection nets
The billiard systems within quadrics, playing the role of discrete analogues
of geodesics on ellipsoids, are incorporated into the theory of integrable
quad-graphs. An initial observation is that the Six-pointed star theorem, as
the operational consistency for the billiard algebra, is equivalent to an
integrabilty condition of a line congruence. A new notion of the
double-reflection nets as a subclass of dual Darboux nets associated with
pencils of quadrics is introduced, basic properies and several examples are
presented. Corresponding Yang-Baxter maps, associated with pencils of quadrics
are defined and discussed.Comment: 18 pages, 8 figure
Comment about pion electro-production and the axial form factors
The claim by Haberzettl (Phys.Rev.Lett.85 (2000) 3576) that the axial form
factor of the nucleon cannot be accessed through threshold pion
electroproduction is unfounded
Formal Design of Asynchronous Fault Detection and Identification Components using Temporal Epistemic Logic
Autonomous critical systems, such as satellites and space rovers, must be
able to detect the occurrence of faults in order to ensure correct operation.
This task is carried out by Fault Detection and Identification (FDI)
components, that are embedded in those systems and are in charge of detecting
faults in an automated and timely manner by reading data from sensors and
triggering predefined alarms. The design of effective FDI components is an
extremely hard problem, also due to the lack of a complete theoretical
foundation, and of precise specification and validation techniques. In this
paper, we present the first formal approach to the design of FDI components for
discrete event systems, both in a synchronous and asynchronous setting. We
propose a logical language for the specification of FDI requirements that
accounts for a wide class of practical cases, and includes novel aspects such
as maximality and trace-diagnosability. The language is equipped with a clear
semantics based on temporal epistemic logic, and is proved to enjoy suitable
properties. We discuss how to validate the requirements and how to verify that
a given FDI component satisfies them. We propose an algorithm for the synthesis
of correct-by-construction FDI components, and report on the applicability of
the design approach on an industrial case-study coming from aerospace.Comment: 33 pages, 20 figure
One-dimensional quantum antiferromagnetism in the orbital CsO compound revealed by electron paramagnetic resonance
Recently it was proposed that the orbital ordering of molecular
orbitals in the superoxide CsO compound leads to the formation of spin-1/2
chains below the structural phase transition occuring at ~K on
cooling. Here we report a detailed X-band electron paramagnetic resonance (EPR)
study of this phase in CsO powder. The EPR signal appears as a broad line
below , which is replaced by the antiferromagnetic resonance below
the N\'{e}el temperature ~K. The temperature dependence of the
EPR linewidth between and agrees with the
predictions for the one-dimensional Heisenberg antiferromagnetic chain of
spins in the presence of symmetric anisotropic exchange interaction.
Complementary analysis of the EPR lineshape, linewidth and the signal intensity
within the Tomonaga-Luttinger liquid (TLL) framework allows for a determination
of the TLL exponent . Present EPR data thus fully comply with the
quantum antiferromagnetic state of spin-1/2 chains in the orbitally ordered
phase of CsO, which is, therefore, a unique orbital system where such a
state could be studied.Comment: 6 pages, 3 figure
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