We present a new measurement of the spin-dependent structure function
g
1
d
of the deuteron in deep inelastic scattering of 190 GeV polarised muons on polarised deuterons, in the kinematic range ...0.003 <
x < 0.7 and 1 GeV
2 <
Q
2 < 60 GeV
2. This structure function is found to be negative at small
x. The first moment
Γ
1
d=∫
0
1
g
1
dd
x evaluated at
Q
0
2 = 10 GeV
2 is 0.034 ± 0.009 (stat.) ± 0.006 (syst.). This value is below the Ellis-Jaffe sum rule prediction by three standard deviations. Using our earlier determination of
Γ
1
p
, we obtain
Γ
1
p
−
Γ
1
n
= 0.199 ± 0.038 which agrees with the Bjorken sum rule.
Evidence for a narrow baryon state is found in quasi-real photoproduction on a deuterium target through the decay channel pK0S→pπ+π−. A peak is observed in the pK0S invariant mass spectrum at ...1528±2.6(stat)±2.1(syst) MeV. Depending on the background model, the naive statistical significance of the peak is 4–6 standard deviations and its width may be somewhat larger than the experimental resolution of σ=4.3–6.2 MeV. This state may be interpreted as the predicted S=+1 exotic Θ+(uudds̄) pentaquark baryon. No signal for an hypothetical Θ++ baryon was observed in the pK+ invariant mass distribution. The absence of such a signal indicates that an isotensor Θ is excluded and an isovector Θ is unlikely.
A measurement of the beam-spin asymmetry in the azimuthal distribution of pions produced in semi-inclusive deep-inelastic scattering off protons is presented. The measurement was performed using the ...HERMES spectrometer with a hydrogen gas target and the longitudinally polarized 27.6 GeV positron beam of HERA. The sinusoidal amplitude of the dependence of the asymmetry on the angle ϕ of the hadron production plane around the virtual photon direction relative to the lepton scattering plane was measured for π+, π− and π0 mesons. The dependence of this amplitude on the Bjorken scaling variable and on the pion fractional energy and transverse momentum is presented. The results are compared to theoretical model calculations.
A new method to extract asymmetries and spin-dependent structure functions is proposed. The method is based on the exact formulae for differences of cross-sections of deep inelastic scattering of ...polarised leptons on polarised nucleons with different orientations of spins. A procedure taking into account dynamical variations of beam and target polarisations as well as peculiarities of data taking and processing, has been developed.
Polarization effects in Drell-Yan processes Sissakian, A. N.; Shevchenko, O. Yu; Nagaitsev, A. P. ...
Physics of particles and nuclei,
01/2010, Letnik:
41, Številka:
1
Journal Article
Recenzirano
Effects of polarization of hadrons and constituent quarks in Drell-Yan processes are considered; they are one of the most efficient tools for investigation of the quark structure of hadrons. Special ...attention is paid to such important parton distribution functions as the transversity and
T
-odd Sivers and Boer—Mulders functions whose study is necessary for understanding the effects connected with the nonzero transverse component of the quark momentum. An original method for direct extraction of transversity and Boer—Mulders function in the proton from the data on Drell—Yan processes, in which a maximum of one hadron in the initial state is transversely polarized, is presented. This method possesses a number of important advantages. The method is applied both to Drell—Yan processes with a valence antiquark (antiproton-proton and pion-proton collisions) and with a sea antiquark (proton-proton, proton-deuteron, and deuteron-deuteron collisions). Theoretical estimates of asymmetries and cross sections for setups at RHIC (BNL, US), NICA (JINR, Russia), COMPASS (CERN, Switzerland), PAX (GSI, Germany), and J-PARC (Japan) are presented for evaluation of the measurability of transversity and T-odd distributions. These theoretical estimates are accompanied by calculations of statistical uncertainties for measured asymmetries using the new Monte Carlo generator of Drell—Yan events. The duality of Drell—Yan processes and those of production of
J
/Φ resonance is studied, and it may allow one to considerably reduce statistical uncertainties of parton distributions. Kinematical conditions, for which this duality can be observed, are evaluated.
Study results of neutral lipids of superficial hydro-lipid film (SHLF) in healthy newborns ( n = 46), in the children with severe allergic history ( n = 29), in newborns with toxic erythema ( n = 34) ...and nappies dermatitis ( n = 29) are presented in the article. The study is performed using thin-layer chromatography. Marked changes in lipid structure of dermal SHLF in all children in comparison with controls are revealed which needs further observation and correction.
PDF
