COMPASS (CERN-NA58) Overview

COMPASS (CERN-NA58) Overview
A. Magnon CEA Saclay-DAPNIA/SPhN COMPASS Collaboration A.Magnon SPIN2006,section 2A, Kyoto October 2, 2006

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

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

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

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

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

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

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

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

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

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

DG/G from open charm untagged tagged A.Magnon 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

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

COMPASS g1D ( ) Also: C.Quintans session 2A new: hep-ex/060938, CERN-PH-EP/ A.Magnon 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

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

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

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

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

AColl (deuteron) p,K Also: F. Bradamante session 2B π K A.Magnon 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

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

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

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

RICH-1 upgrade, in 2006 Lens system + MAPMTs + MAD4 + F1 CsI MWPC + APV25S1 + ADC A.Magnon 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

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

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

Additional slides A.Magnon SPIN2006,section 2A, Kyoto October 2, 2006

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

Transverse L polarization L L Also: A. Ferrero session 2A A.Magnon SPIN2006,section 2A, Kyoto October 2, 2006

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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