-
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
-
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
-
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.
-
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
-
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
-
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
-
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
-
S Horikawa,
I Daito,
A Gorin,
T Hasegawa,
N Horikawa,
T Iwata,
K Kuroda,
I Manuilov,
T Matsuda,
Y Miyachi,
A Riazantsev,
A Sidorov,
N Takabayashi, T Toeda
[show abstract]
[hide abstract]
ABSTRACT: An extensive study was performed on the development of fast and precise scintillating-fibre detectors with position-sensitive photomultipliers (PSPM) for application in high-rate experiments. Several detector prototypes with Kuraray multi-cladding fibres of 0:5 mm diameter and Hamamatsu 16-channel H6568 PSPMs were constructed and tested under different beam conditions at the CERN PS and SPS beam lines. High time resolution of the order of 300 ps (r.m.s.) was obtained with spatial resolution of about 125 mm (r.m.s.) and with detection efficiency in excess of 98%. The detector prototype equipped with a 3-m-long light guide was also tested and showed a time resolution of about 540 ps (r.m.s.). Results of tests using a high-intensity muon beam show excellent stability of the detector performances in time and spatial resolutions as well as in detection efficiency under beam fluxes of up to 1:4 Â 10 8 muons per 2.4-second spill.
Nuclear Instruments and Methods in Physics Research A. 01/2004; 5164060(85).
-
S. Horikawa,
I. Daito,
N. Doshita,
A. Gorin,
T. Hasegawa,
N. Horikawa,
T. Iwata,
K. Kondo,
K. Kuroda,
I. Manuilov,
T. Matsuda,
Y. Miyachi,
A. Riazantsev,
N. Takabayashi, T. Toeda,
S. Torimitsu
[show abstract]
[hide abstract]
ABSTRACT: A fast and precise scintillating fiber (SciFi) tracker, using 0.5-mm-diameter fibers (Kuraray SCSF-78MJ) and position-sensitive photomultiplier tubes (Hamamatsu H6568), has been developed for the COMPASS (NA58) experiment at CERN. Tests of a 16-channel prototype showed an excellent stability in time resolution, in spatial resolution, as well as in detection efficiency under different beam flux of up to 1.4 × 10<sup>8</sup> muons/spill. Four SciFi tracker stations have been constructed and all of them are presently under operation in the experiment with high performances as expected from the prototype.
IEEE Transactions on Nuclear Science 07/2002; · 1.45 Impact Factor
-
S Horikawa,
I. Daito,
N Doshita,
N Horikawa,
T Iwata,
K Kondo,
Y Miyachi,
N Takabayashi, T Toeda,
S. Torimitsu,
A. Gorin,
I. Manuilov,
A. Riazantsev,
T Hasegawa,
T Matsuda,
K. I. Kuroda
[show abstract]
[hide abstract]
ABSTRACT: Fast and precise scintillating fiber tracker (SciFi), using 0.5 mm diameter fibers (Kuraray SCSF-78MJ) and position-sensitive photomultiplier tubes (Hamamatsu H6568), has been developed for COMPASS (NA58) experiment at CERN. Tests of a 16-channel prototype showed an excellent stability in time resolution, in spatial resolution as well as in detection efficiency under different beam flux of up to 1.4×10<sup>8</sup> muons/spill. Four SciFi stations have been constructed and all of them are presently under operation in the experiment with high performances as expected from the prototype.
Nuclear Science Symposium Conference Record, 2001 IEEE; 12/2001
-
[show abstract]
[hide abstract]
ABSTRACT: Fast and precise scintillating fiber detectors using KURARAY fibers and HAMAMATSU multianode H6568 tubes were constructed
for new experiments (DIRAC and COMPASS) at CERN. Tests of the DIRAC detector and COMPASS prototype show high detection efficiency,
good time and space resolution.
Czechoslovak Journal of Physics 01/1999; 49:173-182. · 0.42 Impact Factor
-
S Uozumi,
T Asakawa,
J.P Done,
Y Fujii,
K Furukawa,
K Hara,
T Ishizaki,
S Kaga,
F Kajino,
T Kamon, [......],
R Oishi,
T Ota,
K Sendai,
Y Sugimoto,
T Suzuki,
H Takeda,
T Takeshita,
A Takeuchi, T Toeda,
Y Yamada
[show abstract]
[hide abstract]
ABSTRACT: We have measured performance of a lead/plastic scintillator sampling calorimeter in two separate beam tests at low (1–) and high (10–) energies. The calorimeter is composed of 8-mm-thick lead plates and 2-mm-thick plastic scintillator plates for hardware compensation, where responses to electromagnetic and hadronic showers of the same energy are identical. We find the linearity to be better than 1% in the energy range between 2 and for both pions and electrons. The energy resolutions are obtained to be for pions, where the energy E is given in GeV. The response ratio of electromagnetic showers to hadronic showers is measured to be 1.04±0.01 at low energies, and 0.99±0.01 at high energies.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment.
-
E.S. Ageev,
V.Yu. Alexakhin,
Yu. Alexandrov,
G.D. Alexeev,
M. Alexeev,
A. Amoroso,
B. Badełek,
F. Balestra,
J. Ball,
J. Barth, [......],
E. Weise,
Q. Weitzel,
R. Windmolders,
W. Wiślicki,
A.M. Zanetti,
K. Zaremba,
M. Zavertyaev,
J. Zhao,
R. Ziegler,
A. Zvyagin
[show abstract]
[hide abstract]
ABSTRACT: New high precision measurements of the Collins and Sivers asymmetries of charged hadrons produced in deep-inelastic scattering of muons on a transversely polarised 6LiD target are presented. The data were taken in 2003 and 2004 with the COMPASS spectrometer using the muon beam of the CERN SPS at 160 GeV/c. Both the Collins and Sivers asymmetries turn out to be compatible with zero, within the present statistical errors, which are more than a factor of 2 smaller than those of the published COMPASS results from the 2002 data. The final results from the 2002, 2003 and 2004 runs are compared with naive expectations and with existing model calculations.
Nuclear Physics B.
-
S. Horikawa, T. Toeda,
I. Daito,
N. Doushita,
T. Hasegawa,
N. Horikawa,
T. Iwata,
Y. Kibe,
T. Matsuda,
Y. Miyachi,
K. Noboriguchi,
N. Takabayashi,
T. Tohyama,
A. Wakai
[show abstract]
[hide abstract]
ABSTRACT: The performance of scintillating fiber detectors with 2 m long light guides was investigated for COMPASS experiment, using a 450 MeV/c electron beam.Prototypes consisting of 0.5 mm diameter fibers (Kuraray SCSF-38 single-cladding) with the position-sensitive photomultipliers H6568 (Hamamatsu) were constructed for the test. The time resolution of σ∼430 ps was obtained with about 10 photoelectrons for the prototype of 10-layers structure.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment.
-
P. Abbon,
E Albrecht,
V Yu Alexakhin,
Yu Alexandrov,
G D Alexeev,
M G Alekseev,
A Amoroso,
H. Angerer,
V A Anosov,
B Badelek, [......],
W Wislicki,
H Wollny,
A M Zanetti,
K Zaremba,
M. Zavertyaev,
J Zhao,
R Ziegler,
M Ziembicki,
Y L Zlobin,
A. Zvyagin
[show abstract]
[hide abstract]
ABSTRACT: The COMPASS experiment makes use of the CERN SPS high-intensitymuon and hadron beams for the investigation of the nucleon spin structure and the spectroscopy of hadrons. One or more outgoing particles are detected in coincidence with the incoming muon or hadron. A large polarized target inside a superconducting solenoid is used for the measurements with the muon beam. Outgoing particles are detected by a two-stage, large angle and large momentum range spectrometer. The setup is built using several types of tracking detectors, according to the expected incident rate, required space resolution and the solid angle to be covered. Particle identification is achieved using a RICH counter and both hadron and electromagnetic calorimeters. The setup has been successfully operated from 2002 onwards using a muon beam. Data with a hadron beam were also collected in 2004. This article describes the main features and performances of the spectrometer in 2004; a short summary of the 2006 upgrade is also given.
-
E S Ageev,
V Yu Alexakhin,
Yu A Alexandrov,
G D Alexeev,
M. Alexeev,
A Amoroso,
B Badelek,
F Balestra,
J Ball,
J Barth, [......],
E Weise,
Q. Weitzel,
R Windmolders,
W Wislicki,
A M Zanetti,
K Zaremba,
M V Zavertyaev,
J Zhao,
R Ziegler,
A. Zvyagin
[show abstract]
[hide abstract]
ABSTRACT: New high precision measurements of the Collins and Sivers asymmetries of charged hadrons produced in deep-inelastic scattering of muons on a transversely polarised 6LiD target are presented. The data were taken in 2003 and 2004 with the COMPASS spectrometer using the muon beam of the CERN SPS at 160 GeV/c. Both the Collins and Sivers asymmetries turn out to be compatible with zero, within the present statistical errors, which are more than a factor of 2 smaller than those of the published COMPASS results from the 2002 data. The final results from the 2002, 2003 and 2004 runs are compared with naive expectations and with existing model calculations
-
T. Suzuki,
Y. Fujii,
K. Hara,
T. Ishizaki,
F. Kajino,
N. Kanaya,
J. Kanzaki,
K. Kawagoe,
S. Kim,
T. Matsui, [......],
T. Ota,
K. Sendai,
Y. Sugimoto,
H. Takayama,
H. Takeda,
T. Takeshita,
S. Tanaka,
A. Tanaka, T. Toeda,
Y. Yamada
[show abstract]
[hide abstract]
ABSTRACT: The energy resolution and the e/π ratio of a lead/plastic-scintillator sampling calorimeter were measured for various volume ratios of the lead thickness to the scintillator thickness. For this purpose, a hanging-file-type calorimeter module was constructed in which the thicknesses of the lead absorber and the plastic-scintillator plates were able to be altered very flexibly. The thicknesses of the lead and the scintillator plates can be changed by a 2 mm step form 4 to 16 mm and from 2 to 6 mm, respectively. We measured energy resolution for electrons and pions with the calorimeter module as a function of the thickness of a lead plate in the energy range 1–4 GeV. The best energy resolution for pions was obtained to be 33.6%/ with the configuration where the thicknesses of the lead and the scintillator plates were 4 and 2 mm, respectively. The e/π ratio was measured in the energy range 1–4 GeV. The compensation was found to be achieved for the lead thickness of 9.1±0.3 mm in the case of 2 mm-thick scintillator.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment.
