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COMPASS PLANS

COMPASS PLANS. Stephane Platchkov I nstitut de R echerche sur les lois F ondamentales de l’ U nivers CEA/IRFU, Saclay , France (for the COMPASS Collaboration). EIC workshop Stony Brook, June 24- 27, 2014. COMPASS – a fixed target experiment. A very versatile setup

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COMPASS PLANS

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  1. COMPASS PLANS Stephane Platchkov Institut de Recherchesur les loisFondamentales de l’Univers CEA/IRFU, Saclay, France (for the COMPASS Collaboration) EIC workshop Stony Brook, June 24-27, 2014

  2. COMPASS – a fixed target experiment • A very versatile setup • Several beams available: µ+, µ-, h+, h-, e-=> Several physics goals Energy: 100 – 200 GeV Intensity: up to 109/spill Large acceptance, PID detectors Several particles in the final state Large (1.2 m) polarized target 50 m “Minor” changes to the setup – switch between various physics programs EIC 2014

  3. COMPASS – a fixed target experiment • A very versatile setup • Several beams available: µ+, µ-, h+, h-, e- => Several physics goals Measurements with muon beams • Gluon polarization • Spin-flavor decomposition • Transversity • Transv. Mom. Distributions Measurements with hadron beams • Pion polarizability • Light meson spectroscopy • Baryon spectroscopy • Search for hybrids COMPASS - I (2002 – 2011) COMPASS - II (2012, 2015 – 2017/2018) • DVCS and HEMP • Unpolarized SIDIS and TMDs • Drell-Yan studies • Pion and Kaonpolarizabilities EIC 2014

  4. Nucleon structure studies – physics goals from Bacchetta from Bacchetta PDF (x) TMD (x,kT) GPD (x,bT) Drell-Yan EIC 2014

  5. DVCS and HEMP studies EIC 2014

  6. Beams 100 – 200 GeV Beam polarization: ~80% Both m+ and m- beams x domain: ≈ 0.01 – 0.1 Q2 domain: 1 to 10 (GeV/c)2 Luminosity: 1032 cm-2s-1 (with a 2.5 m long LH2 target) DVCScharacteristics in COMPASS + EIC Detect both outgoing photon and recoiling proton EIC 2014

  7. DVCS and BH cross section for µ+ and µ- Cross section for µp -> µpγ : • COMPASS beams: opposite charge/spin • Charge-and-Spin Sum: • Charge-and-Spin Difference • small for COMPASS DVCS BH Access both Re(H) and Im(H) by measuring the Sum and the Difference EIC 2014

  8. DVCS – SUM of m+ and m- cross sections Expected statistics in 2 x 140 days of data taking Goal: transverse size of the nucleon as a function of xB - Nucleon “tomography” - EIC 2014

  9. Beam Charge and Spin Difference Expected statistics in 2 x 140 days of data taking Kroll, Moutarde, Sabatié, EPJC 73(2013)2278 EIC 2014

  10. DVCS – the COMPASS xBregions – SIMULATION 0.005 < xB <0.01 0.01 < xB < 0.03 xB > 0.03 DVCS BH DVCS BH Large relative amplitude variation as a function of x EIC 2014

  11. Test run – 4 days with a 40 cm long H2 target DVCS – the COMPASS xBregions – REAL DATA 2009 data 278 134 54 DVCS BH dominance Interference DVCS dominance Successful feasibility measurement EIC 2014

  12. DVCS run – main new equipment ECAL2 ECAL0 ECAL1 50 m 4.0 m longTime-Of-Flight detector: 24 inner and 24 outer slabs 2x2 m2 electromagnetic calorimeter, ECAL0 2.5 m long LH target EIC 2014

  13. 2012 DVCS setup – 4 weeks data taking ECAL2 Partially ready ECAL0 ECAL1 Full scale recoil proton detector Liquid H2 target EIC 2014

  14. Transverse size of the nucleon Test data taking in 2012 – 4 weeks 2012 data: expected uncertainty Data analysis is underway EIC 2014

  15. Semi-inclusive unpolarized DIS • Features • Pure hydrogen target, 2.4 m long • High-performance particle identification for p+,p-,p0,K+,K-,K0 etc… • Measurements of: • Multiplicities Input to global FF analysis • Strange quark pPDF down to x=0.004 Phys. Rev. D 89 (2014) 097101 1 week of beam will s(x) continue to raise? EIC 2014

  16. Beyond GPD H • Hard Exclusive Meson production • Vector mesons: sensitive to H, E • allows for flavour separation • Present studies at COMPASS : • Transversely polarized target • No recoil proton detection (From transversity data: 2007/2010) • First example: exclusive r production EIC 2014

  17. Exclusive r0 production • Measurement: μ+ p  μ’ + 0+p +- COMPASS: PLB 731 (2014) 19 NPB 865 (2012) 1 First possible indication for a non-vanishing HT Access to different E and H combinations Analysis of wongoing EIC 2014

  18. Distant future (beyond 2018) • DVCS and HEMP on a transversely polarized target • 2 years of data, NH3 target, 160 GeV, global efficiency ~10% Main challenge: development of dedicated superconducting magnet Planned proposal/addendum EIC 2014

  19. Overview of past/planned GPD experiments EIC 2014

  20. Drell-Yan studies EIC 2014

  21. . COMPASS setup advantages Beam energy: 100 – 200 GeV Hadron (pion) beam Transversely polarized NH3 target Large muon angular acceptance With a negative pion beam: u/u annihilation COMPASS acceptance (MC simulation) Dominated by valence quarks (x ≥ 0.1) Polarized Drell-Yan measurements Drell and Yan, PRL 25 (1970), 316, 902. COMPASS is an ideal place for DY studies EIC 2014

  22. DY (polarized) cross section expansion Tung-Mow Yan (SLAC, 1998): “The process (1970) has been so well understood that it has become a powerful tool for precision measurements and new physics” • Full formalism for two spin ½ hadrons • COMPASS: access 4 TMDs: • Boer-Mulders, Sivers, Pretzelosity, Transversity • Access 4 TMDs – asymmetry modulations: Arnold, Metz and Schlegel, Phys. Rev. D79 (2009) 034005. Boer-Mulders Sivers Pretzelosity Transversity Worm-Gear All four TMDs are also measured in SIDIS EIC 2014

  23. TMDs in Drell-Yan and SIDIS • SIDIS vs TMD • SIDIS: TMD and FF • Drell-Yan: two TMDs • Factorization • TMDs (unlike PDFs) can be process dependent (“non-universality”) • Opposite sign in SIDIS and DY processes: Collins, Soper, Sterman, Adv. Ser. High En Phys. 5, 1988. Crucial test of the QCD factorization approach EIC 2014

  24. Sivers asymmetry (SIDIS) • Compass data on a proton target • pions • kaons COMPASS data: PLB 692 (2010) 240 PLB 717 (2012) 383 + preliminary Hermes data: PRL 103 (2009) 152002 EIC 2014

  25. Drell-Yan acceptances (COMPASS vs E615) 0.04 E615 (1989) 0.4 COMPASS (2014) An order of magnitude improvement EIC 2014

  26. SIDIS vs Drell-Yan (x - Q2) regions Kinematical overlap between SIDIS and Drell-Yan EIC 2014

  27. COMPASS Drell-Yan setup • Upgrade of the spectrometer • Beam telescope (Sci-Fi) • Thick hadron absorber/beam dump • Vertex detector • Polarized target moved 2.2 m upstream EIC 2014

  28. COMPASS Drell-Yan setup • Small cross sections – high intensity h beam (~109/spill of 10 sec) • Possible use of thin nuclear targets (inside the absorber) pion beam 190 GeV • Nominal COMPASS setup (minor modifications) • Dimuon trigger system Polarized Target • Hadron absorber: Tungsten, Alumina and Stainless steel EIC 2014

  29. Drell-Yan – test data taking • Test setup (3 days in 2009) • 190 GeV negative pion beam, I ≤ 1.5x107/s (instead of 108/s) • “poor-man” hadron absorber ( concrete and steel) • two polyethylene target cells • preliminaryDY trigger • Results • Count rate confirmed • Mass resolution as expected • Good vertex resolution • Low background at high masses EIC 2014

  30. Expected statistical accuracy • Assumptions: • Ibeam = 108p/s, L = 2.3x1033, P=90%, f = 0.22, t = 140 days, • spill length = 10 s, every 34 s • ~ 2000 DY events/day in the mass region 4 < Mµµ < 9 GeV/c2 • J/Ψ cross section: about 50 times larger Boer-Mulders Sivers Pretzelosity Transversity EIC 2014

  31. Polarized Drell-Yan – expected results Sivers Boer-Mulders 140 days of data 6.108pions/spill 2 x 55 cm NH3 target 4 < Mmm< 9 GeV Pretzelosity Transversity EIC 2014

  32. DY on nuclear targets flavour-dependent EMC effect Further Drell-Yan studies Dutta et al., PRC83:042201,2011 First glimpse from the 2015 data EIC 2014

  33. Drell-Yan: further possibilities • Medium term • DY on nuclear targets • Flavour dependent EMC, Violation of the Lam-Tung relation • Polarized deuteron ( 6LiD) target • Flavour separated TMDs • Long term • RF separated K- and p beams • Recall: at 190 GeV: p-/K-/p = 96.5%/2.5%/1% • Aim at 1 to 2 orders of magnitude improvement for K- and p EIC 2014

  34. COMPASS OUTLOOK • 2014 • Preparation for DY run • Refurbished PT magnet, PT installation, hadron absorber • 2 months of data taking (October-December) • 2015 • Drell - Yan data taking (1 “year” ≈ 140 days) • End 2015, beg. 2016 • Removal of PT, Installation of LH target, CAMERA, ECAL0 • 2016/2017 • DVCS data taking (2 “years” ≈ 2x140 days) • 2018 and beyond Long Shutdown 2 • Extensions of DY and DVCS programs (definition underway) EIC 2014

  35. The End EIC 2014

  36. Exclusive r0production • Measurement: μ + p  μ’ + 0+p +- 5 single-spin (UT) asymmetries 3 double-spin (LT) asymmetries Curves: Goloskokov and Kroll, EPJ C74(2014)2725 Data: Compass, PLB, 731(2014)19. EIC 2014

  37. Boer-Mulders asymmetry (SIDIS) • Compass data on deuteron (6LiD) • Significantly different from zero • Larger for negative hadrons • Dependence on all three variables: x, z, pT COMPASS preprint, hep-ex:1401.6284 also HERMES: PRD 87 (2013)012010. EIC 2014

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