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PVDIS at JLab 6 GeV

PVDIS at JLab 6 GeV. Robert Michaels Jefferson Lab On Behalf of the HAPPEX Collaboration Acknowledgement: Talk prepared by Kai Pan (MIT graduate student) Parity Mini-Symposium, APS Meeting Apr 30 – May 3 , 2011. Motivation #1.

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PVDIS at JLab 6 GeV

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  1. PVDIS at JLab 6 GeV Robert Michaels Jefferson Lab On Behalf of the HAPPEX Collaboration Acknowledgement: Talk prepared by Kai Pan (MIT graduate student) Parity Mini-Symposium, APS Meeting Apr 30 – May 3, 2011

  2. Motivation #1 Testing Electroweak Standard Model • Standard Model is a successful theory. Data confirms the electroweak sector of the SM at a few 0.1%. • Deficiencies of the Standard Model: mass origin, neutrino oscillation, matter antimatter asymmetry, hierarchy problem. • People believe SM is only a piece of some larger framework, and try to find new physics beyond Standard Model. • Direct Search: LHC, Tevatron, etc… (Higgs mechanism) • Indirect Search: SLAC E158 (Moller), Atomic-PV, Sample, NuTeV, Qweak, PVDIS (Electroweak couplings or weak mixing angle)

  3. Testing Electroweak Standard Model Running of sin2θw PVDIS However, PVDIS 6GeV is NOT to measure θw, but the electroweak coupling constant combination.

  4. Motivation #2 • Constrain the poorly known coupling constant combination (2C2u-C2d) Isosinglet target e (↑L) e (↓R) σ ↑ - σ ↓ spin D2 VS D2 A = σ ↑ + σ ↓ (polarized beam, unpolarized target) DIS is a unique probe accessing C2q Measurement so far not as precise as C1q PDF

  5. Constrain the poorly known coupling constant combination (2C2u-C2d) 2C2u-C2d = -0.08 (+-) 0.24 Δ(2C2u-C2d) = 0.06

  6. Motivation #3 • Constrain the hadronic effect • Non-perturbativeQCD (higher-twist) effect • Charge Symmetry violation (equivalence of u,d quark distribution in proton and neutron) • Provide important guide on the future PVDIS 12 GeVupgrade, for which the ultimate goal is to extract electroweak coupling constant as well as sin2( θw) from the asymmetry free from hadronic effects.

  7. Section II: JlabHall A and PVDIS Experiment Setup • JLab: Linear accelerator provides continuous polarized electron beam • Ebeam = 6 GeV • Pbeam = 90% • 3 experimental halls (Hall A) • Spokespersons: • XiaochaoZheng (UVa) • Bob Michaels (JLab) • Paul Reimer (Argonne) • Thesis students: • Diancheng Wang (UVa) • Xiaoyan Deng (UVa) • Kai Pan (MIT) • Postdocs: • Zhiwen Zhao (UVa) • RameshSubedi (UVa, George Washington University) C A B

  8. Jlab Hall A Top View Magnet Q, D • High Resolution Spectrometer (HRS) • Beam Energy 6.067 GeV • 20 cm long liquid deuterium (LD2) target • 100 uA polarized beam with 90% beam polarization • Two kinematics • Q2=1.1(GeV)2 ; 12.90 ; P0 = 3.66 GeV • Q2=1.9(GeV)2 ; 20.00 ; P0 = 2.63 GeV • X = 0.25 ~ 0.3 Detector Package Detector Hut Magnet Side View Q1 Q2 D1 Q3 Run time: Oct – Dec 2009

  9. PVDIS Experiment Setup • Two DAQ Systems were used: • regular High Resolution Spectrometer (HRS) DAQ • Limitation: Max event taking rate is only 2KHz for each arm, which is far below the raterequirement in PVDIS. • Parity fast counting DAQ • Scalerbased (fast counting with very low deadtime) • Measured scaler counting rate is up to 500KHz for each arm • Hardware-basedParticle Identification (PID) • Scalers integrated over helicity periods, like an integration experiment. Useful for simultaneous recording of kinematics, efficiencies and Particle Identification (PID) analysis NEW

  10. Parity fast-counting scalerDAQ (Hardware-based PID) Shower a2 Preshower a1 Data Discriminator a3 Ps > a1 Ps + Sh> a2 Scaler ANDing GC > a3

  11. Section III: Data Analysis Status Data Analysis Flow Chart HRS Track reconstruction Beam polarization Deadtime correction Pion contaminaiton Electron detection efficiency Other correction Input Hall A Monte Carlo (HAMC) Hall A Trigger Simulation (HATS) Asim ? Parity Parity Data: Pedestal subtraction Beam linearity calibration Selection of clean cut Charge asymmetry analysis Regression and dithering Aexp

  12. 1. Tracking reconstruction • DIS asymmetry is sensitive to Q^2, thus tracking reconstruction • After calibration, asymmetry uncertainty due to Q^2 reconstruction is <1%

  13. 2. Beam Polarization • A’ = Ameasure / Polarization • Use Compton Polarimeterto measure the beam polarization up to 2% accuracy • MollerPolarimeteras a cross check (consistent) • P ~ 90% (+ -) 2%

  14. 3. Particle Identification Performance Electron detection efficiency Pion Rejection Factor ~97% Lead Glass Lead Glass Horizontal Acceptance [m] Horizontal Acceptance [m] Lead glass Gas Cherenkov Overall Electron efficiency 97% 96% 95% Pion Rejection Factor52 200 10e4 Asymmetry correction due to electron efficiency <0.5% pioncontamination <0.1%

  15. 4. Simulation Target Hall A Monte Carlo (HAMC) • Simulating experiment starting from initial beam to detector package (not included) • Incoming and scattered electron energy loss (ionization and bremsstrahlung) • DIS cross section and asymmetries are calculated by using world data fit (PDF) • Standard Quadrupole and Dipole magnet transportation functions

  16. 4. Simulation Target Consistent Hall A Monte Carlo (HAMC) Black: data Red: simulation • Simulating experiment starting from initial beam to detector package (not included) • Incoming and scattered electron energy loss (ionization and bremsstrahlung) • DIS cross section and asymmetries are calculated by using world data fit (PDF) • Standard Quadrupole and Dipole magnet transportation functions

  17. 4. Simulation

  18. 4. Simulation HallATriggerSimulation(HATS) Credit: DianchengWang (Univ. Virginia graduate student) • Simulating detector and DAQ response to the incoming physics events generated by HAMC • Deadtime Simulation • A’ = Ameasure (1-Deadtime) • Deadtimedata is well understood. (consistent with the simulation) • 1% (+ -)0.2% correction on Asymmetry Target

  19. 5. Parity DAQ data analysis (Blinded raw asymmetry) • Arbitrary shift (blinding factor) on measured asymmetry to avoid analysis bias • To do list before unblinding: Pedestal subtraction, BCM calibration, charge asymmetry analysis, selection of clean cut, regression and dithering correction, etc Online Asymmetries, Q2=1.1 (GeV/C)2 Q2=1.9 (GeV/C)2 B L I N D E D! B L I N D E D! will provide a ~3% relative uncertainty compared to the simulation 90 ppm will provide a ~4% relative uncertainty compared to the simulation 161 ppm

  20. Section IV: Summary and Outlook Physics Goal • Experiment will provide world highest-accuracy measurement on • (2C2u-C2d), improving the uncertainty by a factor of four • Constrain the hadronic effect, providing guidance for PVDIS 12 GeV upgrade • Regular HRS DAQ data analysis is close to being finalized • Parity DAQ data analysis is ongoing • Expected to release preliminary (unblined) asymmetry by the end of this summer (in time for PAVI-11 conference). Data Analysis Progress Special thanks to : Kai Pan, Diancheng Wang, Xiaoyan Deng (grad students) XiaochaoZheng& Paul Reimer (co-spokespersons)

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