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PR-09-018: SSA with SBS

PR-09-018: SSA with SBS Measurement of the Semi-Inclusive p and K electro-production in DIS regime from transversely polarized 3 He target with the SBS & BB spectrometers in Hall A G. Cates, E. Cisbani, G.B. Franklin, B. Wojtsekhowski and the SBS Collaboration

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PR-09-018: SSA with SBS

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  1. PR-09-018: SSA with SBS Measurement of the Semi-Inclusive p and K electro-production in DIS regime from transversely polarized 3He target with the SBS & BB spectrometers in Hall A G. Cates, E. Cisbani, G.B. Franklin, B. Wojtsekhowski and the SBS Collaboration http://hallaweb.jlab.org/12GeV/SuperBigBite PR-09-018 (SSA with SBS) / PAC34 / JLab

  2. Propose to measure the SSA of SIDIS processes n(e,e’p)X and n(e,e’K)X • Extract Sivers and Collins (and Pretzelosity) asymmetries on p and K with high statistics • Provide 2D binning (at least) on the relevant variables: x, P and z, for both hadrons • Provide Q2 dependence • Explore for the first time the high x valence region (with overlap to HERMES, COMPASS, JLab6 data) • Understanding of QCD dynamics in the nucleon by the Sivers effect • Improve knowledge of the nucleon structure in terms of parton distribution functions • Shed more light on the origin of the nucleon spin PR-09-018 (SSA with SBS) / PAC34 / JLab

  3. Method: from SIDIS to SSA to DFFF Pretzelosity PR-09-018 (SSA with SBS) / PAC34 / JLab

  4. Collins Moments on proton/deuteron COMPASS/deuteron proton Hepex-0802.2160 From Pappalardo / Transversity 2008 • Proton (left) • K- and p- with opposite sign, strong flavor dependence (but K errors significant)! • K+ and p+ consistent with u dominance • COMPASS compatible with HERMES • Deuteron (up): consistent with 0, expected asymmetry on neutron as large as on proton From Levorato / Transversity 2008 Larger effects at larger x PR-09-018 (SSA with SBS) / PAC34 / JLab

  5. Sivers Moments on proton/deuteron COMPASS/deuteron Hepex-0802.2160 From Pappalardo / Transversity 2008 • Proton (left) • K+ twice p+ conflict with u dominance expectation • K- and p- consistent with 0 • COMPASS smaller than HERMES • Deuteron (up): consistent with 0, expected asymmetry on neutron as large as on proton From Levorato / Transversity 2008 PR-09-018 (SSA with SBS) / PAC34 / JLab

  6. Extraction of DF and FF from a Global Fit Transversity first moment (assume DTsea = 0) HERMES/p + COMPASS/d (Q2~2.5 GeV2) e+e- from BELLE (Q2=110 GeV2) Sivers function Anselmino et al 12/08 Anselmino et al 05/08 Collins Fragmentation Function Collins: Unfav/Fav FF puzzle (not seen in Unpol FF) Sivers: large s-bar sea small PR-09-018 (SSA with SBS) / PAC34 / JLab

  7. Theory Report for PR-09-018 M. Burkardt, H. Kamano “ … A measurement of the Sivers function at JLab would be very interesting for several reasons. Most importantly, the statistics would be much higher… Since there is a strong overlap in the x range with the HERMES data, it would be possible to verify/falsify the “kaon puzzle”… The JLab data would not only extend the Q2 leverage of the HERMES/COMPASS experiments but at the same time provide results for two different value of Q2, and thus can shed some light on the Q2 evolution of the Sivers function… The HERMES and COMPASS results are more consistent with each other in the case of the Collins function. However, also here a very interesting results needs confirmation: it appears that the Collins function for “unfavored” fragmentation is about as large (and of opposite sign) than that of the “favored” fragmentation… A JLab experiment, with significantly higher statistics than the HERMES data, could verify/falsify this result, and also help to study the Q2 evolution of the Collins function…” PR-09-018 (SSA with SBS) / PAC34 / JLab

  8. Experimental Setup and parameters e+3He→e’+p(K)+X BB: e-arm at 30o  = 45 msr GEM Tracker Gas Cherenkov Shower  GMn/PR-09-019 SBS: h-arm at 14o  = 50 msr GEM tracker excellent PID / RICH Hadron CALO Event rate: ~104×HERMES 60 days of production expected stat. accuracy: 1/10 of proton HERMES Beam: 50 A, E=8.8 and 11 GeV (80% long. Pol.) Target: 65% polarized 3He  GEn(2)/PR-09-016  Luminosity: 1.4×1037 cm-2s-1, 0.05 sr PR-09-018 (SSA with SBS) / PAC34 / JLab

  9. What is special in this experiment • High Luminosity: • 105 larger than in HERMES • High target polarization (65%) • Fast target polarization switch (120 seconds) • 4 (8) transverse polarization directions • Use of SBS (and BB): • Large solid angle (50 msr), very good angular and vertex resolutions • Large momentum coverage (2-7 GeV/c) • Excellent hadron PID • Reuse equipment from GEp(5) (approved), GEn(2) and GMn (proposals) PR-09-018 (SSA with SBS) / PAC34 / JLab

  10. Hadron Arm: SBS • Angular Resolution: (p = 4 GeV) sJ_h = 0.09+0.59/p [mrad] (0.3 mrad) sJ_v = 0.14+1.34/p [mrad] (0.4 mrad) • Vertex Resolution: 0.53+4.49/p [mm] (0.2 cm/sinJcentral) • Momentum resolution sp/p = 0.03 p+0.29 % (0.4 %) • CALO Trigger Threshold: 1.5 GeV (online), 2.0 (offline) • Magnet: 48D48 - 46 cm gap • 2 Tm field integral -100 ton • Insert for beam pipe • GEM chambers for tracking with 70 m resolution • HERMES RICH for hadron-ID • Segmented Hadron CALO (15x15 cm2 blocks) PR-09-018 (SSA with SBS) / PAC34 / JLab

  11. Hadron PID: HERMES RICH on SBS 5.5 GeV K+ C4F10 gas REAL DATA from NIMA 479 (2002) 511 14.6 GeV e- 1.5 GeV p- Very stable performance (dn/(naerogel-1)= 1%, 9 years) Stored at UVa under safe/controlled conditions (also additional wall of spare Aerogel) PR-09-018 (SSA with SBS) / PAC34 / JLab

  12. SBS Background on HCALO Background Rate and Trigger Logic BB-Shower (1 GeV): 200 kHz BB-Cherenkov (3-4 pe): 2.5 MHz 40 ns coinc./segmented accidental: 4 kHz DIS-e: 1 kHz SBS-HCalo (1.5 GeV): 3 MHz Online 50 ns coinc. real coinc: 100 Hz acc: 750 Hz 4 ns time gate Total: 12 Hz BB-Offline / Tracking p0 suppression: 1 kHz Vertex Correlation (6s=3 cm): 0.6 Hz Momentum cut > 2GeV Bck = 0.3 Hz Signal =67 Hz PR-09-018 (SSA with SBS) / PAC34 / JLab

  13. ~20% of the HERMES RICH PMT array Challenges in large acceptance/high luminosity • SBS Tracker rate 60 kHz/cm2; 3xGEM support rate >10 MHz/cm2 • Track reconstruction: BB first,SBS from vertex to segmented HCALO hit • RICH PID: high segmentation of photon detector (2000 PMT) is the optimal solution: • Expected 35 extra hits/event from:soft photons → Compton electronsin aerogel (50 ns gate width) 2-5% occupancy PR-09-018 (SSA with SBS) / PAC34 / JLab

  14. Prop. Exp. Ebeam = 11.0 GeV Prop. Exp. Ebeam = 8.8 GeV Current Transversity Exp. E06-010 Q2 coverage We will investigate the Q2 dependence of the Sivers and Collins functions, with overlap in the region of HERMES; reveal higher twist effects. Analysis of the Q2 effect will use also the results of presently running 6 GeV E06-010 Transversity experiment PR-09-018 (SSA with SBS) / PAC34 / JLab

  15. Azimuthal Coverage fh Partial coverage of fh but in sin/cos sensible regions 0.15 < x <0.65 Jh_cent. = 14° Ebeam = 11 GeV 4 target spin directions Complete coverage of the Collins, Sivers and “Pretzelosity” azimuthal angles with 4 target spin directions (with 8 target spin directions even better uniformity) PR-09-018 (SSA with SBS) / PAC34 / JLab

  16. Figure of Merit Two beam energy runs for Q2 dependence studies: PR-09-018 (SSA with SBS) / PAC34 / JLab

  17. Expected Statistical Accuracy on p Contalbrigo/SPIN08 5×5 bins (0.15<x<0.65, 0.2<z<0.7) (only one shown) High x region, with partial overlap with HERMES 2D binning in (x,z), (x,P) and (z,P) for p and K and Q2 dependence DF from CTEQ5M FF from DSS PR-09-018 (SSA with SBS) / PAC34 / JLab

  18. Expected Statistical Accuracy on K • Superior quality of Kaon data • Extend at higher x with partial overlap with existing data on proton, deuteron and expected results of HallA Transversity 6 GeV DF from CTEQ5M FF from DSS Rate normalized to HERMES/p+d K production PR-09-018 (SSA with SBS) / PAC34 / JLab

  19. Systematics • Physics Effects: • FSI on nuclei • 3He: Pp~2%, |Yd|2~10%, Presc~10-20% • D: Pp~85%, |Yd|2~6%, Presc~5-10% • Higher Twist Terms of SIDIS asymmetries • Experimental/Analysis: • Random background • Vector Meson • Particle ID • Acceptance Effects • Radiative Corrections PR-09-018 (SSA with SBS) / PAC34 / JLab

  20. Summary • We propose to measure the SSA in the transversely polarized SIDIS processes: n(e,e’p)X andn(e,e’K)X at two Q2 • Experiment will re-use part of GEp(5) equipment and the HERMES RICH • Will be ready to take data in 2014, with no significant extra costs respect to SBS apparatus for GEp(5) PR-09-018 (SSA with SBS) / PAC34 / JLab

  21. Backup Slides PR-09-018 (SSA with SBS) / PAC34 / JLab

  22. Collaboration Responsibilities All spokespersons are active members of GEp(5) experiment PR-09-018 (SSA with SBS) / PAC34 / JLab

  23. SciFi/NSERC Experimental Setup with SciFi A small part of the SBS-SciFi tracker can be used in front of the HCALO to constraint the track reconstruction PR-09-018 (SSA with SBS) / PAC34 / JLab

  24. Polarized SI-DIS process PR-09-018 (SSA with SBS) / PAC34 / JLab

  25. GEn(2)  High Lumi Target • 60% transverse polarization • Support 60 uA beam current • Extended target cell (60 cm) • Use proved alkali-hybrid mixture technique for polarization transfer • Improved diagnostics for optimal tuning of the potassium-rubidium ratio • Use line-narrowed high-power diode-laser arrays • Use convection for gas mixing between target and pumping chambers • Better description of the target behavior by the identification of the relaxation rate (X-term) • Use of metal target cell PR-09-018 (SSA with SBS) / PAC34 / JLab

  26. Electron Arm: GEn(2), GMn  BigBite • Use the current BB setup: • Gas Cherenkov • Two-Layer Electromagnetic Calo, • Scintillator Hodoscope • GEM based Tracker Replace MWDC tracker by: • GEM based tracker, from components of the GEp(5) front tracker PR-09-018 (SSA with SBS) / PAC34 / JLab

  27. SBS Solid Angle Solid angle of SBS as a function of central angle (and distance from target) SBS can go very forward, at reduced solid angle. Moving from 14 to 10 degree, the solid angle goes from 50 to ~40 msr PR-09-018 (SSA with SBS) / PAC34 / JLab

  28. ALICE/STAR RICH Reconstruction Expected ~12% occupancy with 3sp/K separation Performance proved by MC and STAR (3--5% occupancy) real data. D. Di Bari, RICH07/Trieste PR-09-018 (SSA with SBS) / PAC34 / JLab

  29. Phase Space PR-09-018 (SSA with SBS) / PAC34 / JLab

  30. Phase Spase of the Relevant Variables Ebeam = 11 GeV PR-09-018 (SSA with SBS) / PAC34 / JLab

  31. Azimuthal Angles Distributions The coverage of f can be extended moving forward SBS to Jcentral~ 10 degree (with a decrease of SBS acceptance) and/or changing (not dramatically) the BB settings PR-09-018 (SSA with SBS) / PAC34 / JLab

  32. Azimuthal angles coverage vs x Azimuthal angles coverage does not very significantly depend on x,Q2 Number of target spin directions can be increased to have a better uniformity; 8 would be optimal in this respect. PR-09-018 (SSA with SBS) / PAC34 / JLab

  33. fh coverage vs x Partial coverage of one (or both) azimuthal variables. When sinf or cosf (or fS) are close to 0 (red band) the AUT equation degenerates into the sum or difference of AC and AS. The variation of fS is helpless. In all other case, even with partial coverage of f and fS the extraction of the two modulated terms is possible. Error on the extraction roughly goes like (coverage_fraction)-½ fh sin/cos functions PR-09-018 (SSA with SBS) / PAC34 / JLab

  34. Background Rate and Trigger Logic BigBite Background on Shower SBS Background on HCALO BB-Shower (1 GeV): 200 kHz BB-Cherenkov (3-4 pe): 2.5 MHz SBB-HCalo (1.5 GeV): 3 MHz SBB-RICH: 5% occupancy Online 50 ns coinc. real coinc: 100 Hz acc: 750 Hz 40 ns coinc./segmented accidental: 4 kHz DIS-e: 1 kHz Signal =67 Hz 4 ns time gate Total: 12 Hz Vertex Correlation (6s=3 cm): 0.6 Hz Momentum cut > 2GeV: Bck = 0.3 Hz BB-Offline / Tracking p0 suppression: 1 kHz PR-09-018 (SSA with SBS) / PAC34 / JLab

  35. Terms entering the measured asymmetry PR-09-018 (SSA with SBS) / PAC34 / JLab

  36. Systematics/Physics • Target FSI relative error: expected <7% following the analysis of Scopetta/Transversity/2008 • Higher Twists: • we will study the Q2 dependence with high statistics; • terms will be included into the fit whose stability benefits again of the high statistics • Unpolarized analysis will also be carried on PR-09-018 (SSA with SBS) / PAC34 / JLab

  37. Systematics/Exp. Apparatus • Random • dilution factor expected to be small < 1% (S/N = 67/0.3) • Relative error well below 10% • Vector Meson: • from PHYTIA prediction tuned on HERMES data below 2.5%; lower at higher x • can be studied at higher z • Acceptances: • azimuthal angles are well covered even with partial fh coverage • X,z,P,Q2 effects suppressed by 2D (at least) binning • Radiative QED Effects: • Influence x,Q2 and azimuthal angles; PHYTIA can be used to estimate the correction factor (and systematic error) • According to HERMES we expect a systematic error <5% • PID: • RICH detector with up to 5% occupancy expect to provide 4s separation at least PR-09-018 (SSA with SBS) / PAC34 / JLab

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