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E S Ageev,
V Yu Alexakhin,
Y. Alexandrov,
G D Alexeev,
A Amoroso,
B Badelek,
F Balestra,
J Ball,
G Baum,
Y Bedfer, [......],
U Wiedner,
M Wiesmann,
R Windmolders,
S Wirth,
W Wilicki,
A M Zanetti,
K Zaremba,
J Zhao,
R Ziegler,
A. Zvyagin
[show abstract]
[hide abstract]
ABSTRACT: We present a precise measurement of the deuteron longitudinal spin asymmetry $A_1^d$ and of the deuteron spin-dependent structure function $g_1^d$ at $Q^2 < $ 1~(GeV/$c$)$^2$ and $4\cdot$10$^{-5} < x < $~2.5$\cdot$10$^{-2}$ based on the data collected by the COMPASS experiment at CERN during the years 2002 and 2003. The statistical precision is tenfold better than that of the previous measurement in this region. The measured $A_1^d$ and $g_1^d$ are found to be consistent with zero in the whole range of $x$.
Physics Letters B 04/2007; 647(5-6):330-340. · 3.95 Impact Factor
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E S Ageev,
V Yu Alexakhin,
Yu A Alexandrov,
G D Alexeev,
A Amoroso,
B Badelek,
F Balestra,
J Ball,
G Baum,
Y Bedfer, [......],
U Wiedner,
M Wiesmann,
R Windmolders,
S Wirth,
W Wislicki,
A M Zanetti,
K Zaremba,
J Zhao,
R Ziegler,
A. Zvyagin
[show abstract]
[hide abstract]
ABSTRACT: We present a determination of the gluon polarization Delta G/G in the nucleon, based on the helicity asymmetry of quasi-real photoproduction events, Q^2<1(GeV/c)^2, with a pair of large transverse-momentum hadrons in the final state. The data were obtained by the COMPASS experiment at CERN using a 160 GeV polarized muon beam scattered on a polarized 6-LiD target. The helicity asymmetry for the selected events is <A_||/D> = 0.002 +- 0.019(stat.) +- 0.003(syst.). From this value, we obtain in a leading-order QCD analysis Delta G/G=0.024 +- 0.089(stat.) +- 0.057(syst.) at x_g = 0.095 and mu^2 =~ 3 (GeV}/c)^2.
Physics Letters B 02/2006; 633(1):25-32. · 3.95 Impact Factor
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E.S. Ageev,
V.Yu. Alexakhin,
Yu. Alexandrov,
G.D. Alexeev,
A. Amoroso,
B. Badelek,
F. Balestra,
J. Ball,
G. Baum,
Y. Bedfer, [......],
U. Wiedner,
M. Wiesmann,
R. Windmolders,
S. Wirth,
W. Wiślicki,
A.M. Zanetti,
K. Zaremba,
J. Zhao,
R. Ziegler,
A. Zvyagin
[show abstract]
[hide abstract]
ABSTRACT: We present a determination of the gluon polarization ΔG/G in the nucleon, based on the helicity asymmetry of quasi-real photoproduction events, Q2<1 2(GeV/c), with a pair of large transverse-momentum hadrons in the final state. The data were obtained by the COMPASS experiment at CERN using a 160 GeV polarized muon beam scattered on a polarized 6LiD target. The helicity asymmetry for the selected events is 〈A∥/D〉=0.002±0.019(stat)±0.003(syst). From this value, we obtain in a leading-order QCD analysis ΔG/G=0.024±0.089(stat)±0.057(syst) at xg=0.095 and μ2≃3 2(GeV/c).
Physics Letters B. 02/2006; 633(1):25-32.
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V Yu Alexakhin,
Yu Alexandrov,
G D Alexeev,
A Amoroso,
B Badełek,
F Balestra,
J Ball,
G Baum,
Y Bedfer,
P Berglund, [......],
E Weise,
M Wiesmann,
R Windmolders,
S Wirth,
W Wiślicki,
A M Zanetti,
K Zaremba,
J Zhao,
R Ziegler,
A Zvyagin
[show abstract]
[hide abstract]
ABSTRACT: First measurements of the Collins and Sivers asymmetries of charged hadrons produced in deep-inelastic scattering of muons on a transversely polarized 6LiD target are presented. The data were taken in 2002 with the COMPASS spectrometer using the muon beam of the CERN SPS at 160 GeV/c. The Collins asymmetry turns out to be compatible with zero, as does the measured Sivers asymmetry within the present statistical errors.
Physical Review Letters 06/2005; 94(20):202002. · 7.37 Impact Factor
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E S Ageev,
V Yu Alexakhin,
Yu A Alexandrov,
G D Alexeev,
A Amoroso,
B Badeek,
F Balestra,
J Ball,
G Baum,
Y Bedfer, [......],
Q. Weitzel,
M Wiesmann,
R Windmolders,
S Wirth,
W Wislicki,
A M Zanetti,
K Zaremba,
J Zhao,
R Ziegler,
A. Zvyagin
[show abstract]
[hide abstract]
ABSTRACT: Narrow Xi-pi+- and Xi-bar+pi+- resonances produced by quasi-real photons have been searched for by the COMPASS experiment at CERN. The study was stimulated by the recent observation of an exotic baryonic state decaying into Xi-pi-, at a mass of 1862 MeV, interpreted as a pentaquark. While the ordinary hyperon states Xi(1530)^0 and Xi-bar(1530)^0 are clearly seen, no exotic baryon is observed in the data taken in 2002 and 2003.
European Physical Journal C 05/2005; 41(4):469-474. · 3.63 Impact Factor
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E S Ageev,
V Yu Alexakhin,
Yu A Alexandrov,
G D Alexeev,
A Amoroso,
B Badeek,
F Balestra,
J Ball,
G Baum,
Y Bedfer, [......],
Q. Weitzel,
M Wiesmann,
R Windmolders,
S Wirth,
W Wislicki,
A M Zanetti,
K Zaremba,
J Zhao,
R Ziegler,
A. Zvyagin
[show abstract]
[hide abstract]
ABSTRACT: We present a new measurement of the longitudinal spin asymmetry A_1^d and the spin-dependent structure function g_1^d of the deuteron in the range 1 GeV^2 < Q^2 < 100 GeV^2 and 0.004< x <0.7. The data were obtained by the COMPASS experiment at CERN using a 160 GeV polarised muon beam and a large polarised 6-LiD target. The results are in agreement with those from previous experiments and improve considerably the statistical accuracy in the region 0.004 < x < 0.03.
Physics Letters B 04/2005; 612(3-4):154-164. · 3.95 Impact Factor
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V Yu Alexakhin,
Yu A Alexandrov,
G D Alexeev,
A Amoroso,
B Badeek,
F Balestra,
J Ball,
G Baum,
Y Bedfer,
P Berglund, [......],
E Weise,
M Wiesmann,
R Windmolders,
S Wirth,
W Wislicki,
A M Zanetti,
K Zaremba,
J Zhao,
R Ziegler,
A. Zvyagin
[show abstract]
[hide abstract]
ABSTRACT: First measurements of the Collins and Sivers asymmetries of charged hadrons produced in deep-inelastic scattering of muons on a transversely polarized 6-LiD target are presented. The data were taken in 2002 with the COMPASS spectrometer using the muon beam of the CERN SPS at 160 GeV/c. The Collins asymmetry turns out to be compatible with zero, as does the measured Sivers asymmetry within the present statistical errors.
Physical Review Letters 02/2005; 94(20). · 7.37 Impact Factor
