179 research outputs found
Near-threshold production of omega mesons in the pn -> d omega reaction
The first measurement of the p n -> d omega total cross section has been
achieved at mean excess energies of Q = 28 and 57 MeV by using a deuterium
cluster-jet target. The momentum of the fast deuteron was measured in the ANKE
spectrometer at COSY-Juelich and that of the slow "spectator" proton p(sp) from
the p d -> p(sp) d omega reaction in a silicon telescope placed close to the
target. The cross sections lie above those measured for p p -> p p omega but
seem to be below theoretical predictions.Comment: 7 pages, 8 figures; second approach to describe the background has
been added; results changed insignificantly, EPJ in pres
The pion-nucleon scattering lengths from pionic deuterium
We use the framework of effective field theories to discuss the determination
of the S-wave \pi N scattering lengths from the recent high-precision
measurements of pionic deuterium observables. The theoretical analysis proceeds
in several steps. Initially, the precise value of the pion-deuteron scattering
length a_{\pi d} is extracted from the data. Next, a_{\pi d} is related to the
S-wave \pi N scattering lengths a_+ and a_-. We discuss the use of this
information for constraining the values of these scattering lengths in the full
analysis, which also includes the input from the pionic hydrogen energy shift
and width measurements, and throughly investigate the accuracy limits for this
procedure. In this paper, we also give a detailed comparison to other effective
field theory approaches, as well as with the earlier work on the subject,
carried out within the potential model and multiple scattering framework.Comment: The replacement includes an erratum, which is published in Eur. Phys.
J.
Pleiotropic Meta-Analysis of Cognition, Education, and Schizophrenia Differentiates Roles of Early Neurodevelopmental and Adult Synaptic Pathways
Measurement of the LT-asymmetry in \pi^0 electroproduction at the energy of the \Delta (1232) resonance
The reaction p(e,e'p)pi^0 has been studied at Q^2=0.2 (GeV/c)^2 in the region
of W=1232 MeV. From measurements left and right of q, cross section asymmetries
\rho_LT have been obtained in forward kinematics \rho_LT(\theta_\pi^0=20deg) =
(-11.68 +/- 2.36_stat +/- 2.36_sys)$ and backward kinematics
\rho_LT(\theta_\pi^0=160deg) =(12.18 +/- 0.27_stat +/- 0.82_sys). Multipole
ratios \Re(S_1+^* M_1+)/|M_1+|^2 and \Re(S_0+^* M_1+)/|M_1+|^2 were determined
in the framework of the MAID2003 model. The results are in agreement with older
data. The unusally strong negative \Re(S_0+^* M_1+)/|M_1+|^2 required to bring
also the result of Kalleicher et al. in accordance with the rest of the data is
almost excluded.Comment: 7 pages, 7 figures, 4 tables. Changed content. Accepted for
publication in EPJ
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
Electroweak corrections to W\gamma and Z\gamma production at the LHC
We have calculated the electroweak O(\alpha) corrections to the processes p p
-> Z \gamma + X -> \nu_l \bar{\nu}_l \gamma + X, p p -> Z \gamma + X -> l
\bar{l} \gamma + X, and p p -> W \gamma + X -> \nu_l \bar{l} \gamma + X at the
LHC, with l=e,\mu and \nu_l=\nu_e,\nu_\mu,\nu_\tau. The virtual corrections are
evaluated in leading-pole approximation, whereas the real corrections are taken
into account exactly. These corrections are implemented into a Monte Carlo
generator which includes both phase-space slicing and subtraction to deal with
soft and collinear singularities. We present numerical results for total cross
sections as well as for experimentally interesting distributions. Applying
typical LHC cuts, the electroweak corrections are of the order of -5% for the
total cross sections and exceed -20% for observables dominated by high
centre-of-mass energies of the partonic processes.Comment: 39 pages, LaTeX, 7 eps figure
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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