1 / 31

COMPASS II proposal available at : CERN-SPSC-2010-014 preprint

Proposal for GPD studies at COMPASS E. Burtin CEA-Saclay Irfu/SPhN On behalf of the COMPASS Collaboration MENU 2010 – College of William & Mary Williamsburg - June 2 nd , 2010. Proposal submitted to the SPS comittee (May 17,2010) Physics topics :

saskia
Download Presentation

COMPASS II proposal available at : CERN-SPSC-2010-014 preprint

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Proposalfor GPD studiesat COMPASSE. Burtin CEA-Saclay Irfu/SPhNOn behalf of the COMPASS CollaborationMENU 2010 – College of William & MaryWilliamsburg -June 2nd, 2010 • Proposalsubmitted to the SPS comittee (May 17,2010) • Physicstopics: • Hard exclusive photon and meson production • UnpolarizedPDFs and TMD effects in SIDIS • Pion inducedDrell-Yan muon pair production (TMD) • Experimentalstudies of chiral perturbation theory COMPASS II proposalavailableat : CERN-SPSC-2010-014preprint http://cdsweb.cern.ch/record/1265628/files/SPSC-P-340.pdf

  2. CERN.gif Lac Léman Jura mountains COMPASS SPS LHC N 2

  3. What makes Compass unique ? • CERN High energymuonbeam • 100 - 190 GeV • 80% Polarisation • μ+andμ-available • Opposite polarization Luminositylimit Foreseen program : DVCS and meson production off a liquid H2 target (unpolarized) • Will explore the intermediate • xBjregion • Uncoveredregionbetween • ZEUS+H1 and HERMES+Jlab xBj Gluon, sea and valence quarks

  4. μ’ * θ μ p  Comparison of BH and DVCS at 160 GeV DVCS : Bethe-Heitler :   BH dominates BH and DVCS at the samelevelDVCS dominates excellentaccessDVCS amplitude studyofdDVCS/dt referenceyieldthrough the interference

  5. Known expression μ’ * θ μ p φ Azimuthal angular dependence analysis from Belitsky, Kirchner, Müller : polarized beam off unpolarized target dσ(μpμp) = dσBH + dσDVCSunpol + PμdσDVCSpol + eμ aBHRe ADVCS + eμ PμaBHIm ADVCS Pμ eμ eμPμ Twist-2 M11 >> Twist-3 M01 Twist-2 gluon M-11

  6. μ’ * θ μ p φ Angular dependence analysis Case of COMPASS :μ+(P=-0.8) and μ-(P=+0.8) unpolarized H2target DU,CS : dσμ+- dσμ-= 2 PμdσDVCSpol+ eμaBHRe ADVCS => Re(F1H) SU,CS :dσμ++ dσμ-= 2(dσBH+dσDVCSunpol) + 2eμ PμaBHIm ADVCS => dσ/dt => Im (F1H)

  7. FromSU,CS :transverse imaging Using SU,CS : dDVCS / dt ~ exp(-Bt) B ~ ½ <r2> Ansatzatsmall x :B(x) = b0 + 2 α’ ln(x0/x)α’ =0.125 GeV-2 (FFS) 160 GeVmuon beam 2.5m LH2 target 2 years L = 1222 pb-1 εglobal = 10 % ? 1. 0.5 Assuming 3% syst. error on BH subtraction 0.65 0.02 fm H1 PLB659(2008) 2.5 σslope meas. for : α’ > 0.26 (ECAL 1+2 ) α’ > 0.125 (ECAL 0+1+2) COMPASS xB

  8. Exclusive production of rho mesons dVMP / dt ~ exp(-Bt) Exclusive VMP VMP model developed by Sandacz Normalisedaccording Goloskokov and Kroll 160 GeVmuon beam 2.5m LH2 target 2 years L = 1222 pb-1 εglobal = 10 % Sensitive to the nucleon size + the transverse size of the meson Q2=1 GeV2 B ~ 8 GeV-2 Q2=10 GeV2 B ~ 5.5 GeV-2

  9. μ’ * θ μ p φ Angular dependence analysis Case of COMPASS :μ+(P=-0.8) and μ-(P=+0.8) unpolarized H2target DU,CS : dσμ+- dσμ-= 2 PμdσDVCSpol+ eμaBHRe ADVCS => Re(F1H) SU,CS :dσμ++ dσμ-= 2(dσBH+dσDVCSunpol) + 2eμ PμaBHIm ADVCS => dσ/dt => Im (F1H)

  10. μ’ * θ μ p φ DU,CS : Beam Charge & Spin Difference DU,CS : dσμ+- dσμ-= 2 PμdσDVCSpol+ eμaBHRe ADVCS 160 GeVmuon beam 2.5m LH2 target 2 years L = 1222 pb-1 εglobal = 10 % => Re(F1H) Systematicerrors:3% charge-dependenteffectbetween+ and -

  11. DU,CS() over the kinematical domain 160 GeVmuon beam 2.5m LH2 target 2 years L = 1222 pb-1 εglobal = 10 % Syst. : 3% μ+/μ- norm.  (deg) using the VGG model Phys. Rev. D60:094017,1999

  12. Sensitivity of COMPASS: cosϕmodulation BCSA = DU,CS /SU,CS = A0 + ACS,Ucosϕ + A2 cos2ϕ B B B B B B

  13. Continuation of the GPD program :constrain the GPD E with+, - beamand transverselypolarized NH3 (proton) target DT,CS dT(+) -dT(-) Im(F2H– F1E)sin(- S) cos  160 GeV muon beam 1.2 m polarized NH3 target (f=0.26) 2 years - εglobal = 10 %

  14. Experimentalrealisation 2008 DVCS beam test Compass hadron set-up Talks of F. Haas, S. Neubert μ’ γ proton • New « superRPD » and H2target • Hermeticcalorimetry : Move ECALsupstream and/or complete ECAL2 • New ECAL0 upstream of SM1

  15. Recoil Proton Detector • 4 m long scintillatorslabs • ~ 300ps timing resolution • Full scale prototype • testedsuccessfully Gandalf Project: 1 GHz digitalisation of the PMT signal to cope for high rate

  16. ECAL 0 • Requirements • - Photon energy range 0.2- 30 GeV • - Size: 320cm x 320cm ; • - Granularity 4x4 – 6x6 cm2 • - Energy resolution < 10.0%/√E (GeV) • - Thickness < 50 cm, • - Insensitive to the magnetic field. • Prototype under studies • Shaschlyk module with AMPD readout • Tested DVCS+BH ECAL1&2

  17. Ring B Ring A 2008-2009 DVCS tests Compass hadron run Target region Selection of events : - one vertex with μ and μ’ - no other charged tracks - only 1 high energy photon (Δt<5ns) - 1 proton in RPD with p < 1. GeV/c DVCS Bethe-Heitler

  18. 2008 beam test : exclusivity cuts μ’+γ Δp =|Pμ’+γ|-|PRPD| Δpperp < 0.2 GeV γ μ’ miss Δϕ proton Transverse plane Δϕ=ϕmiss- ϕRPD Δϕ < 36 deg

  19. 2008 beam test : Bethe-Heitler signal Monte-Carlo simulation of BH (dominant) and DVCS Deep VCS Bethe-Heitler => Bethe-Heitlerobserved Detection efficiency : εμ+p->μ+p+γ = 0.32 +/- 0.13 After all cuts, Q2>1GeV2 • Global efficiency : • - μ+p->μ+p+γ efficiency • SPS & COMPASS availability • Dead time • trigger efficiency • εglobal = 0.13 +/- 0.05 Projections of errors are realistic ~ 10 times more data taken in 2009

  20. 2009 beam test : DVCS signal ~ 10 times more data takenthan in 2008 • Excess of events for xbj>0.03 • is a sign for DVCS

  21. Conclusions & perspectives • the COMPASS-II proposal has been submitted • Wide physics case proposed : • GPDs, TMDs, Chiral perturbation theory, unpolarizedPDFs • SPS Committee meets at the end June • COMPASS has a great potential in GPDs physics • Study of the GPD H with a LH2 target: 2013- • measurement ott-slopes – transverse partonic structure of the nucleon • measurement of Beam Charge and Spin differences & asymmetries • Equipments needed : • 4m long RPD, 2.5m LH2 target, Extended & improved calorimetry • at a later stage : • study of the GPD E with a transversely polarized target

  22. μ’ * θ μ p φ DU,CS : Beam Charge & Spin Difference DU,CS : dσμ+- dσμ-= 2 PμdσDVCSpol+ eμaBHRe ADVCS 160 GeVmuon beam 2.5m LH2 target 2 years L = 1222 pb-1 εglobal = 10 % => Re(F1H) Systematicerrors:3% charge-dependenteffectbetween+ and -

  23. ECAL0 and ECAL1 2008 DVCS beam test Horizontal proton γ μ’ “superRPD” SM1 Vertical ECAL0 ECAL1 ECAL2

  24. Meson production : filter of GPDs • Cross section measurement : • Vectormeson : ρ,ω,…H & E • Pseudo-scalar : π,η… H & E ~ ~ Wouldallow for flavorseparation : Hρ0= 1/2 (2/3 Hu + 1/3 Hd + 3/8 Hg) Hω= 1/2 (2/3 Hu – 1/3 Hd + 1/8 Hg) H = -1/3 Hs - 1/8 Hg  ρ: ω :   9 : 1 : 2 at large Q2 Transverselypolarizedtargetasymmetry on vectormeson :  E/H ( studiedat COMPASS without RPD )

  25. GPD program : new equipments DVCSμp μ’p’ μ’ ECal1 + ECal2 10° • 2.5 m liquid H2target μ Hermeticcalorimetry new ECAL0 p’ 4m long Recoil Proton Detector Later stage… Transverselypolarizedtarget Associated RPD

  26. Hadron program RPD Proton identification in RPD Elasticscattering (hadron beam)

  27. Kinematical consistency : ϑγ*γ μ’ With μ, μ’ and γ : μ γ* With μ, μ’ and proton : γ proton μ+p->μ’+γ+p Events rejected

  28. Measurements and Estimations for resolution tmin=-0.06 GeV2 Good resolution in t Importance for the the transverse imaging

  29. g* g,p,r hard x+ x- soft GPDs P P’ t for quarks : 4 functions H,E,H,E(x,,t) ~~ Generalized Parton Distributions Factorisation: Q2 large, -t<1 GeV2 contains pdf H(x,0,0) = q(x) measured in DIS Generalized Parton Distributions contains form factors measured in elastic scattering contains information on the nucleon spin : Ji’s sum rule :

  30. *  Q² x+ x- p GPDs t 3-Dpartonic structure of the nucleon (Pz,ry,z) Hard Exclusive Scattering Deeply Virtual Compton Scattering ep ep p z x P r y x boost GPDs : H( x,,t ) Fourier (=0) access to correlations : ( Px, ry,z) Burkardt,Belitsky,Müller,Ralston,Pire

More Related