1 / 17

HAPPEX-II Status Report

HAPPEX-II Status Report. Robert J. Feuerbach Jefferson Lab Constructed from contributions from the HAPPEX Collaboration. Hall A Collaboration Meeting December 5, 2005. Strange-form factors. At Q 2 =0.11 GeV 2 , A PV can access Hydrogen: (G s E + 0.08G s M ) Helium: G s E.

holly-pope
Download Presentation

HAPPEX-II Status Report

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. HAPPEX-II Status Report Robert J. Feuerbach Jefferson Lab Constructed from contributions from the HAPPEX Collaboration Hall A Collaboration Meeting December 5, 2005

  2. Strange-form factors At Q2=0.11 GeV2, APV can access Hydrogen: (GsE + 0.08GsM ) Helium: GsE

  3. How is the PV Asymmetry Measured? 1 ppm: 5% measurement —> 4x1014counts Beam Helicity - 30 Hz PV asymmetry between window pair is measured. 34M (He) and 24M (H) good pairs collected.

  4. Beam Asymmetries Araw = Adet - AQ + E+ ixi • natural beam jitter (regression) • beam modulation (dithering) Slopes from

  5. Hall A Polarimeters Cherenkov cones Compton Moller PMT Target Spectrometer: QQDQ

  6. The Goal The goal was to improve on the error bars of last year by a factor of ~3. 2004: Helium APV: s ~ 0.84 ppm (11.2%) Hydrogen APV: s ~ 0.24 ppm (17%) • This required • higher luminosity • similar to the previous year’s tight control over systematics uncertainties.

  7. Some Improvements for this year • Sweeper Magnet • IbHe: 28uA to 36uA • IbH : 35uA to 58uA • S0 trigger • Beam quality • In development: • Integrating Compton • Cavity monitors

  8. Run Summary Helium Eb=2.75 GeV Scheduled: 48 days July 9 – Aug 7 Aug 7 – Aug 31 July 28 – Sept 1 Sept 9 – Sept 27 Actual: 55 days • Late start due to • installation • sweeper/septum and spectrometer commissioning • beamline commissioning ~18 day “parasitic” extension (to Hall C) was very important Scheduled: 39 days Hydrogen Eb=3.18 GeV Oct 15 – Nov 23 Actual: 36 days Oct 16 – Nov 21 Last day for PREx tests

  9. Auxiliary Studies • Al (target wall) Backgrounds: ~1.8% (He), ~0.7% (H) • Inelastics (quasi-elastic) • Rescattering probability with dipole scan • He: Prelim estimate: <2% He QE, ~1.8% Al, <0.6% rescatter • H: Prelim estimate: ~0.7% Al, <0.2% rescatter • Q2 measurement (scans, Counting DAQ, optics, angle) • Polarimetry: Compton and Moller in good agreement

  10. Optics with Sweeper Sweeper induces ~simple shifts of phi and Z. Angle found with nuclear-recoil method.

  11. Polarimetry Results Helium • Discrepancy of ~0.6% in the transfer function (LvsR) compared to last year and last absolute measurement in 2001. • Will be opening up the Compton to re-measure the transfer function to understand the effect.

  12. New “Challenges” • Electronics pickup between an (unconnected) helicity module and magnet controls • 100nm beam-position difference • Transverse asymmetry • ~3% vertical polarization, He AT ~ 13 ppm -> suggests 0.8 ppm difference • AL– AR is large (0.9 ppm), with correct sign! • Compton power dropped 1200W ->300W • cleaning optics brought it to 500W • excellent beam quality resulted in ~20 S/B

  13. Physics Asymmetry Helium 2004: APV: s ~ 0.21 ppm (3.5%) APV: s ~ 0.84 ppm (11.2%) GEs: s ~ 0.014 GEs: s ~ 0.042 Hydrogen 2004: APV: s ~ 0.24 ppm (17%) APV: s ~ 0.12 ppm (8%) GEs+0.080GMs:s ~ 0.025 GEs+0.084GMs: s ~ 0.012 NOTE: Statistical error only! Systematic error will likely increase Helium error bar by ~40%, and Hydrogen by about 25%

  14. Online Raw Asymmetry (blinded) Helium Hydrogen

  15. Dc2 = 1 95% c.l. Impact of the Measurement He: nucl-ex/0506010 (reviewed and recommended for PRL) H: nucl-ex/0506011 (under revision for submission to PL)

  16. Future • Analysis is beginning (continuing). • Knowledge transfer to next generation of students • Next collaboration meeting in late February 2006. • P-REX and HAPPEX-3 will benefit greatly from high current/high beam polarization now available: • 100uA @ 80% vs. 35uA @ 71% • Manpower needed for the Compton upgrade. • data in ~2008, graduate 2009?

More Related