Longitudinal polarization of Λ\Lambda and Λˉ\bar \Lambda 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)

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

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 $\Delta_T q(x)$ 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 $^6$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

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

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 $\bar q q$ 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

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

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

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]

Determination of gluon polarization from deep inelastic scattering and collider data

We investigate impact of $\pi^0$-production data at Relativistic Heavy Ion Collider (RHIC) and future E07-011 experiment for the structure function $g_1$ of the deuteron at the Thomas Jefferson National Accelerator Facility (JLab) on studies of nucleonic spin structure, especially on the polarized gluon distribution function. By global analyses of polarized lepton-nucleon scattering and the $\pi^0$-production data, polarized parton distribution functions are determined and their uncertainties are estimated by the Hessian method. Two types of the gluon distribution function are investigated. One is a positive distribution and the other is a node-type distribution which changes sign at $x \sim 0.1$. Although the RHIC $\pi^0$ data seem to favor the node type for $\Delta g(x)$, it is difficult to determine a precise functional form from the current data. However, it is interesting to find that the gluon distribution $\Delta g(x)$ is positive at large $x$ ($>0.2$) due to constraints from the scaling violation in $g_1$ and RHIC $\pi^0$ data. The JLab-E07-011 measurements for $g_1^d$ should be also able to reduce the gluon uncertainty, and the reduction is comparable to the one by RUN-5 $\pi^0$-production data at RHIC. The reduction is caused by the error correlation between polarized antiquark and gluon distributions and by a next-to-leading-order (NLO) gluonic effect in the structure function $g_1^d$. We find that the JLab-E07-011 data are accurate enough to probe the NLO gluonic term in $g_1$. Both RHIC and JLab data contribute to better determination of the polarized gluon distribution in addition to improvement on polarized quark and antiquark distributions.Comment: 11 pages, 9 eps figures, To be published in Nuclear Physics B. AAC08 FORTRAN package is available at the web site http://spin.riken.bnl.gov/aac