112 research outputs found
The phase of the sigma -> pi-pi amplitude in J/Psi -> omega-pi-pi
The phase variation of the sigma -> pi-pi amplitude is accurately determined
as a function of mass from BES II data for J/Psi -> omega-pi-pi. The
determination arises from interference with the strong b1(1235)-pi amplitude.
The observed phase variation agrees within errors with that in pi-pi elastic
scattering.Comment: 10 pages, 4 figures, Euro. Phys. J C (in press
Anisotropic field dependence of the magnetic transition in Cu2Te2O5Br2
We present the results of measurements of the thermal conductivity of
Cu2Te2O5Br2, a compound where tetrahedra of Cu^{2+} ions carrying S=1/2 spins
form chains along the c-axis of the tetragonal crystal structure. The thermal
conductivity kappa was measured along both the c- and the a-direction as a
function of temperature between 3 and 300 K and in external magnetic fields H
up to 69 kOe, oriented both parallel and perpendicular to the c-axis. Distinct
features of kappa(T) were observed in the vicinity of T_N=11.4 K in zero
magnetic field. These features are unaltered in external fields which are
parallel to the c-axis, but are more pronounced when a field is applied
perpendicularly to the c-axis. The transition temperature increases upon
enhancing the external field, but only if the field is oriented along the
a-axis.Comment: 5 pages, 3 figure
Zemach and magnetic radius of the proton from the hyperfine splitting in hydrogen
The current status of the determination of corrections to the hyperfine
splitting of the ground state in hydrogen is considered. Improved calculations
are provided taking into account the most recent value for the proton charge
radius. Comparing experimental data with predictions for the hyperfine
splitting, the Zemach radius of the proton is deduced to be fm.
Employing exponential parametrizations for the electromagnetic form factors we
determine the magnetic radius of the proton to be fm. Both values
are compared with the corresponding ones derived from the data obtained in
electron-proton scattering experiments and the data extracted from a rescaled
difference between the hyperfine splittings in hydrogen and muonium
Additional Suppression from High Density Effects
At high energies the saturation effects associated to the high parton density
should modify the behavior of the observables in proton-nucleus and
nucleus-nucleus scattering. In this paper we investigate the saturation effects
in the nuclear production and estimate the modifications in the energy
dependence of the cross section as well as in the length of the nuclear medium.
In particular, we calculate the ratio of to Drell-Yan cross sections
and show that it is strongly modified if the high density effects are included.
Moreover, our results are compared with the data from the NA50 Collaboration
and predictions for the RHIC and LHC kinematic regions are presented. We
predict an additional suppression associated to the high density
effects.Comment: 13 pages, 5 figures, version to be published in Eur. Phys. J.
Behavior of a Model Dynamical System with Applications to Weak Turbulence
We experimentally explore solutions to a model Hamiltonian dynamical system
derived in Colliander et al., 2012, to study frequency cascades in the cubic
defocusing nonlinear Schr\"odinger equation on the torus. Our results include a
statistical analysis of the evolution of data with localized amplitudes and
random phases, which supports the conjecture that energy cascades are a generic
phenomenon. We also identify stationary solutions, periodic solutions in an
associated problem and find experimental evidence of hyperbolic behavior. Many
of our results rely upon reframing the dynamical system using a hydrodynamic
formulation.Comment: 22 pages, 14 figure
Elliptic flow of charged particles in Pb-Pb collisions at 2.76 TeV
We report the first measurement of charged particle elliptic flow in Pb-Pb
collisions at 2.76 TeV with the ALICE detector at the CERN Large Hadron
Collider. The measurement is performed in the central pseudorapidity region
(||<0.8) and transverse momentum range 0.2< < 5.0 GeV/. The
elliptic flow signal v, measured using the 4-particle correlation method,
averaged over transverse momentum and pseudorapidity is 0.087 0.002
(stat) 0.004 (syst) in the 40-50% centrality class. The differential
elliptic flow v reaches a maximum of 0.2 near = 3
GeV/. Compared to RHIC Au-Au collisions at 200 GeV, the elliptic flow
increases by about 30%. Some hydrodynamic model predictions which include
viscous corrections are in agreement with the observed increase.Comment: 10 pages, 4 captioned figures, published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/389
The ALICE Transition Radiation Detector: Construction, operation, and performance
The Transition Radiation Detector (TRD) was designed and built to enhance the capabilities of the ALICE detector at the Large Hadron Collider (LHC). While aimed at providing electron identification and triggering, the TRD also contributes significantly to the track reconstruction and calibration in the central barrel of ALICE. In this paper the design, construction, operation, and performance of this detector are discussed. A pion rejection factor of up to 410 is achieved at a momentum of 1 GeV/c in p-Pb collisions and the resolution at high transverse momentum improves by about 40% when including the TRD information in track reconstruction. The triggering capability is demonstrated both for jet, light nuclei, and electron selection. (c) 2017 CERN for the benefit of the Authors. Published by Elsevier B.V
Higher harmonic anisotropic flow measurements of charged particles in Pb-Pb collisions at 2.76 TeV
We report on the first measurement of the triangular , quadrangular
, and pentagonal charged particle flow in Pb-Pb collisions at 2.76
TeV measured with the ALICE detector at the CERN Large Hadron Collider. We show
that the triangular flow can be described in terms of the initial spatial
anisotropy and its fluctuations, which provides strong constraints on its
origin. In the most central events, where the elliptic flow and
have similar magnitude, a double peaked structure in the two-particle azimuthal
correlations is observed, which is often interpreted as a Mach cone response to
fast partons. We show that this structure can be naturally explained from the
measured anisotropic flow Fourier coefficients.Comment: 10 pages, 4 figures, published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/387
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