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COMPASS (CERN-NA58) Overview
A. Magnon CEA Saclay-DAPNIA/SPhN COMPASS Collaboration A.Magnon SPIN2006,section 2A, Kyoto October 2, 2006
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SPIN2006,section 2A, Kyoto October 2, 2006
Longitudinally polarized muons GeV/c 2.108 m/ spill (4.8s / 16.8s) PB= -80% Longitudinally or transversely polarized deuteron target : 6LiD PT ~ 50% Luminosity: ~ cm-2s-1 LHC COMPASS at CERN M2 beam line SPS A.Magnon SPIN2006,section 2A, Kyoto October 2, 2006
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SPIN2006,section 2A, Kyoto October 2, 2006
COMPASS Spectrometer Trigger Hodoscopes ECALs & HCALs MWPCs SM2 RICH 50 m SM1 Drift Chambers m Filters/Walls 6LiD target Straws GEMs Si Micromegas 160 GeV m SciFi veto A.Magnon SPIN2006,section 2A, Kyoto October 2, 2006
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SPIN2006,section 2A, Kyoto October 2, 2006
Physics Programmes SPIN2006 Muon beam programme Polarised target (Long. & Transv.) Gluon contribution to nucleon spin Quark polarisation (g1, DS, Dq, flavor separation) Transversity Production of r, F, J/Ψ, L, ... Hadron beam programme Primakoff: p, K polarisabilities Exotics q-states, glue balls Double charmed hadrons Drell-Yann (project) Muon beam, LH2 target, proton recoil detector Generalized Parton Distributions (project ~ 2010) A.Magnon SPIN2006,section 2A, Kyoto October 2, 2006
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SPIN2006,section 2A, Kyoto October 2, 2006
GeV m beam & 6LiD Long/Transv polarisations idem (~ 80/20) idem hadron beam NO SPS beam (Several upgrades) GeV m beam & 6LiD Long/polarisation (plan) A.Magnon SPIN2006,section 2A, Kyoto October 2, 2006
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Physics Results Overview
DG/G from production of high pT hadron pairs & open charm g1D, new COMPASS NLO fit, a0, Ds, DS, DG Transversity: Collins, Sivers asymmetries (L Long. & Transv. Polarisations, r vector meson) Upgrades, prospects A.Magnon SPIN2006,section 2A, Kyoto October 2, 2006
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SPIN2006,section 2A, Kyoto October 2, 2006
DG/G from high pT hadron pairs Photon Gluon Fusion: gg -> qq High pT hadron pair qq -> hh Scale m2 = Q2 or SpT2 Large statistics Physical background 2 cases: Q2 > 1 (GeV/c)2 Q2 < 1 (GeV/c)2 A.Magnon SPIN2006,section 2A, Kyoto October 2, 2006
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SPIN2006,section 2A, Kyoto October 2, 2006
DG/G from high pT hadron pairs + Photon Gluon Fusion Leading Order QCD compton Resolved g Q2 < 1 (GeV/c)2 aLL : calculable partonic asymmetry RPGF : Monte Carlo is required to calculate RPGF A.Magnon SPIN2006,section 2A, Kyoto October 2, 2006
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SPIN2006,section 2A, Kyoto October 2, 2006
DG/G from high pT hadron pairs Two high pT hadrons, pT > 0.7 GeV/c, SpT2 > 2.5 (Gev/c)2 Q2 < 1 (GeV/c)2 analysis - large statistics - perturbative QCD scale from SpT2 - PHYTIA MC used to evaluate RPGF (0.3) & physical Bkg, low pT, resolved g 2002 – data Q2 < 1 (GeV/c)2 DG/G = ± (stat) ± (syst) @ xg ~ 0.085, m2 = 3 (GeV/c)2 A.Magnon SPIN2006,section 2A, Kyoto October 2, 2006
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SPIN2006,section 2A, Kyoto October 2, 2006
DG/G from high pT hadron pairs Two high pT hadrons, pT > 0.7 GeV/c, SpT2 > 2.5 (Gev/c)2 Q2 > 1 (GeV/c)2 analysis - lower statistics - perturbative QCD scale from Q2, - LEPTO MC used to evaluate RPGF (0.33) & physical Bkg 2002 – 2003 data Q2 > 1 (GeV/c)2 DG/G = 0.06 ± 0.31 (stat) ± 0.06 (syst) @ xg = 0.13 ± 0.08, m2 ~ 3 (GeV/c)2 A.Magnon SPIN2006,section 2A, Kyoto October 2, 2006
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SPIN2006,section 2A, Kyoto October 2, 2006
DG/G from open charm Photon Gluon Fusion: gg -> cc CHARM: c -> D0 -> Kp Scale m2 = 4mc2 Theory understood s ~ 100 nb, BR = 4% Combinatorial background Limited statistics Challenging experiment. c c A.Magnon SPIN2006,section 2A, Kyoto October 2, 2006
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SPIN2006,section 2A, Kyoto October 2, 2006
DG/G from open charm untagged tagged A.Magnon SPIN2006,section 2A, Kyoto October 2, 2006
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SPIN2006,section 2A, Kyoto October 2, 2006
DG/G from open charm aLL calculated with help of Monte Carlo and parametrized by measured quantities, (Neural Network used.) 2002 – data D0 + D* DG/G = ± 0.41 (stat) ± (syst ≤ stat) @ xg ~ 0.15, m2 ~ 13 (GeV/c)2 A.Magnon SPIN2006,section 2A, Kyoto October 2, 2006
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SPIN2006,section 2A, Kyoto October 2, 2006
Direct measurements of DG/G ∫G(x) = 2. 5 GRSV2000 NLO fits to g1 m2 = 3 Gev2 ∫G(x) = 0.6 (GRSV stdr) ∫G(x) = 0.2 ΔG/G is small (xg ≈ 0.1) ∫DG>1 disfavoured LO high-pT ΔG/G results shown with GRSV NLO fits to g1 Consistent also with RHIC ALL (p0 channel) measurements A.Magnon SPIN2006,section 2A, Kyoto October 2, 2006
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SPIN2006,section 2A, Kyoto October 2, 2006
COMPASS g1D ( ) Also: C.Quintans session 2A new: hep-ex/060938, CERN-PH-EP/ A.Magnon SPIN2006,section 2A, Kyoto October 2, 2006
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SPIN2006,section 2A, Kyoto October 2, 2006
COMPASS g1D ( ) Also: I.Savin session 2A NLO fits to g1N world data (2006) & COMPASS A.Magnon SPIN2006,section 2A, Kyoto October 2, 2006
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SPIN2006,section 2A, Kyoto October 2, 2006
COMPASS g1D ( ), NLO fit NLO fit to world data (2006) & COMPASS, two equally probable solutions : DG > DG < 0 ηG (Q2=3(GeV/c)2) = , ,-0.14 ηS (Q2=3(GeV/c)2) = ± ± 0.01 COMPASS data alone : a0 (Q2=3(GeV/c)2) = ± (stat) ± 0.05 (syst) D s+D s (Q2=3(GeV/c)2) = ± (stat) ± 0.02 (syst) A.Magnon SPIN2006,section 2A, Kyoto October 2, 2006
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SPIN2006,section 2A, Kyoto October 2, 2006
Measurements of DG/G ∫G(x) = 0.3 NLO fit to g1 m2 = 3 Gev2 ∫G(x) = -0.3 LO high-pT ΔG/G results shown with new NLO fits to g1 A.Magnon SPIN2006,section 2A, Kyoto October 2, 2006
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SPIN2006,section 2A, Kyoto October 2, 2006
Prospects DS ~ 0.2 (before) ~ 0.3 (now) Large DG less and less a likely candidate Choose between two scenarios ? DS DG Lq Lg ½ = 1/2 × ½ = 1/2 × COMPASS/RHIC JLab/HERMES/COMPASS A.Magnon SPIN2006,section 2A, Kyoto October 2, 2006
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Transverse spin: Collins & Sivers asymmetries
spin dependent fragmention of transversely polarized quarks into hadrons Intrinsic kT dependence of the quark distribution A.Magnon SPIN2006,section 2A, Kyoto October 2, 2006
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SPIN2006,section 2A, Kyoto October 2, 2006
AColl (deuteron) p,K Also: F. Bradamante session 2B π K A.Magnon SPIN2006,section 2A, Kyoto October 2, 2006
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SPIN2006,section 2A, Kyoto October 2, 2006
ASiv (deuteron) Anselmino et. al hep-ph/ Efremov, Goeke, Scheitzer, hep-ph/060354 (fit to BELLE & HERMES data) A.Magnon SPIN2006,section 2A, Kyoto October 2, 2006
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SPIN2006,section 2A, Kyoto October 2, 2006
More polarimeters, prospects More polarimeters for transvsersity: Two-hadrons T spin asymmetries (R. Joosten 2B) L & L T polarisations (A. Ferrero 2A) Prospects: Precise transversity deuteron COMPASS data: hint for p & n cancellation for deuteron ? Strong case for transversity proton data with COMPASS in 2007. A.Magnon SPIN2006,section 2A, Kyoto October 2, 2006
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SPIN2006,section 2A, Kyoto October 2, 2006
Polarized target upgrade, in 2006 Also: F.Gautheron session 9A + - New 3-cell system & microwave cavity matched for larger acceptance, reduces false asymmetries New COMPASS target magnet -> 180 mrad A.Magnon SPIN2006,section 2A, Kyoto October 2, 2006
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SPIN2006,section 2A, Kyoto October 2, 2006
Polarized target performances Polarization of 6LiD in 2006 +53.5% % % Higher & faster than in 2004 days A.Magnon SPIN2006,section 2A, Kyoto October 2, 2006
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SPIN2006,section 2A, Kyoto October 2, 2006
RICH-1 upgrade, in 2006 Lens system + MAPMTs + MAD4 + F1 CsI MWPC + APV25S1 + ADC A.Magnon SPIN2006,section 2A, Kyoto October 2, 2006
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SPIN2006,section 2A, Kyoto October 2, 2006
RICH-1 upgrade, MAPMTs “on-line” Very promising results ! - Precise timing High photon statistics A.Magnon SPIN2006,section 2A, Kyoto October 2, 2006
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SPIN2006,section 2A, Kyoto October 2, 2006
FoM for DG/G from open charm 1/s(DG/G)1/2 = FoM Upgrades Beam delivered in 2006 will be ~ 0.5 of our expectation In 2006, apparatus will have reached optimum performances allowing us to make the most productive use of SPS beam A.Magnon SPIN2006,section 2A, Kyoto October 2, 2006
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SPIN2006,section 2A, Kyoto October 2, 2006
Prospects Proton target with Transverse polarisation (planned in 2007) with Longitudinal polarisation (beyond 2007) SIDIS Particle ID Revisiting Bjorken SR ? Flavor separation A.Magnon SPIN2006,section 2A, Kyoto October 2, 2006
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SPIN2006,section 2A, Kyoto October 2, 2006
Additional slides A.Magnon SPIN2006,section 2A, Kyoto October 2, 2006
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Longitudinal L & L polarisations
Statistics of ~ Λ and ~ Λ from 2003 data 2004 data will at least double statistics Access to s and s quarks, also Ds ? Need dedicated studies with Monte Carlo Also: M. Sapozhnikov session 2A A.Magnon SPIN2006,section 2A, Kyoto October 2, 2006
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SPIN2006,section 2A, Kyoto October 2, 2006
Transverse L polarization L L Also: A. Ferrero session 2A A.Magnon SPIN2006,section 2A, Kyoto October 2, 2006
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Hard exclusive r0 meson production
Large statistics on diffractive production of r, f, J/Ψ Large x, Q2 range Measure spin density matrix elements and L-double spin asymmetries A1 for r0 compatible with zero, more data needed A.Magnon SPIN2006,section 2A, Kyoto October 2, 2006
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