727 research outputs found
Longitudinal polarization of and hyperons in deep-inelastic scattering at COMPASS
The production of Lambda and Lambda-bar hyperons by polarized muons of 160
GeV/c on a polarized 6LiD target has been studied using the COMPASS
spectrometer. First preliminary results on the longitudinal polarization of
Lambda and Lambda-bar hyperons produced in the deep-inelastic scattering will
be presented for 2002 data set.Comment: 4 pages, 2 figures, proceeding of SPIN2004, Triest
Methods and complex of programs for radiating particle 3DOF nonlinear dynamics analysis
The Lie-transform perturbation theory for non-autonomous non- Hamiltonian systems and its implementation in a complex of Mathematica programs are described. On the example of LEP 108/90 lattice the radiation effects are shown to play an important effect on particle stability at high energies. (9 refs)
Transversity signals at COMPASS
COMPASS is a fixed target experiment at the CERN SPS, with a rich physics
program focused on nucleon spin structure and on hadron spectroscopy. One of
the main goals of the spin program is the measurement of the transverse spin
distribution function in semi-inclusive DIS off transversely
polarized nucleons. For this purpose approximately 20% of the running time in
the years 2002 to 2004 with the longitudinally polarized muon beam of 160 GeV
and with LiD polarized target was used to collect data with the target
polarized transversely with respect to the beam direction. The 2002 data have
been already analysed and published. We present here the preliminary results
from the full statistics for the Collins and Sivers single hadron asymmetries
and for the transverse spin asymmetry in hadron pair production.Comment: 4 pages, 5 figures, prepared for the QCD06 Conference, 3-7th July
2006, Montpellie
Transverse Spin Structure of the Nucleon from COMPASS
The measurement of transverse spin effects in semi-inclusive deep-inelastic
scattering is an important part of the COMPASS physics program. In the years
2002-2004 data were taken by scattering a 160 GeV muon beam on a transversely
polarized deuteron target. In 2007, additional data were collected on a
transversely polarized proton target. New results for the Collins and Sivers
asymmetries from the analysis of the proton data are presented.Comment: Proceedings of QCD08, Montpellier, July 200
Measurement of the longitudinal spin structure of the proton by COMPASS
The inclusive A_1,p and hadron double-spin asymmetries A_p^pi+, A_p^pi-,
A_p^K+, A_p^K- measured at COMPASS (CERN SPS) in deep-inelastic scattering of a
polarized muon beam off a polarized NH_3 solid target are presented. The
results have been obtained with the full statistics collected in 2007 for the
longitudinal target polarization. Proton asymmetries have been combined with
the published deuteron ones. An evaluation of the non-singlet spin-dependent
structure function g_1^NS(x,Q^2) and its first moment, which confirms the
validity of the Bjorken sum-rule, is presented. A LO evaluation of polarized
quark densities is also presented. The use of the proton data allows to perform
a full flavor separation and to extract individual helicity densities of u, d,
anti-u, anti-d and s quarks. All sea quark densities are found to be compatible
with zero in the full range of the measurements.Comment: 4 pages, 5 figures, presented at the 3rd joint International HADRON
STRUCTURE '09 Conference, Tatranska Strba (Slovak Republic
Transversity Measurements at COMPASS
The measurement of transverse spin effects in semi-inclusive deep-inelastic
scattering is an important part of the COMPASS physics program. From the
analysis of the 2002-2004 data, new results for the transverse target spin
asymmetry of z-ordered identified pion and kaon pairs are presented. In
addition, a first result for the transverse target spin asymmetry of
exclusively produced rho^0 mesons on the deuteron is shown.Comment: Proceedings of Photon07, Paris, 200
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Analytical Study and Tracking Simulations of the Beam-Beam Compensation at Tevatron
Head-on and long-range induced tunespread of about 0.025 in the Tevatron collider at Run II (together with the increased strength of the resonances) can significantly deteriorate the {bar p} lifetime and the collider luminosity. It was proposed to employ the so-called Tevatron Electron Lenses (TEL) to compress the beam-beam footprint and eliminate completely the bunch-to-bunch tunespread (PACMAN effect) for small amplitude particles. The first lens has been recently installed and tested [1]. This report presents results of analytical studies and tracking simulations of the linear beam-beam compensation (elimination of the bunch-to-bunch tune variation). Compression of the beam-beam footprint (nonlinear compensation) is discussed in [2]
Chiral symmetry breaking and the spin content of hadrons
From the parton distributions in the infinite momentum frame one finds that
only about 30% of the nucleon spin is carried by spins of the valence quarks,
which gave rise to the term "spin crisis". Similar results hold for the lowest
mesons, as it follows from the lattice simulations. We define the spin content
of a meson in the rest frame and use a complete and orthogonal
chiral basis and a unitary transformation from the chiral basis to the (2S+1)LJ
basis. Then, given a mixture of different allowed chiral representations in the
meson wave function at a given resolution scale, one can obtain its spin
content at this scale. To obtain the mixture of the chiral representations in
the meson we measure in dynamical lattice simulations a ratio of couplings of
interpolarors with different chiral structure. For the rho meson we obtain
practically the 3S1 state with no trace of the spin crisis. Then a natural
question arises: which definition does reflect the spin content of a hadron?Comment: 7 pp, Presented at Int. School of Nuclear Physics: "From Quarks and
Gluons to Hadrons and Nuclei", Erice-Sicily, 16 - 24 September, 201
Generelized Parton Distributions in light meson production
We analyze light meson electroproduction within the handbag model, where the
amplitude factorizes into Generelized Parton Distributions (GPDs) and a hard
scattering part. The cross sections and spin asymmetries for various vector and
pseudoscalar mesons are analyzed. We discuss what information on hadron
structure can be obtained from GPDs.Comment: Latex, 14 pages, 12 figures, Presented at the 5th joint International
HADRON STRUCTURE '11 Conference, June 27- July 1, 2011, Tatranska Strba
(Slovak Republic
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