SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 E-158 : A precise measurement of at low Antonin VACHERET CEA SACLAY PAVI 2004, June 10 The 2 miles long LINAC at SLAC

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 Physics Motivation Apparatus Control of systematics Analysis Run I+II preliminary results Conclusion

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 Extracting the weak charge at low M ø ller scattering : - Sensitive to: e, Q w Parity violation asymmetry : Tree level Moller asymmetry : QwQw

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 Radiative corrections 1 loop corrections change the relation between A ee and : 3% corrections to

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 Sensitivity Electron compositness  ~ 10 TeV Z’ (GUT) boson M Z’ ~ 0.8 TeV Projection Aim to measure to level 6.5  significance level to radiative corrections effect. 1. Precise measurement away from Z pole complementary to e-e+ colliders 2. Sensitive to new physics scenarii :

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 SLAC E158 ESA A-line UC Berkeley Caltech Jefferson Lab Princeton Saclay SLAC Smith College Syracuse UMass Virginia Sep 97: EPAC approval : Design and Beam Tests 2000: Funding and construction 2001: Engineering run 2002: Physics Runs I, II 2003: Physics Run III SLAC

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 Experiment principle LH2 4-7 mrad N+,N- E e = 45 GeV Fast polarization reversal 120 Hz High Polarization Pe=85% A ee =P e A exp High intensity 5x10 11 e - /pulse BEAM TARGET DETECTOR 2,7 GHz scattered M ø ller High density target,  ee =12  b L ~ cm -2 s -1 Raw Asymmetry =1.3x10 -7 (130 ppb)  (Apv) = (10 ppb) Need electrons Flux integration 4 Months to achieve 10% statistical precision

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 Polarized beam Optical pumping : Helicity sequence : Quadruplet RLLR,LLRR,… Wavelength (nm) Polarization (%) QE (%) Very high-charge polarized electron beams are possible (Pe~85%)  Beam helicity is chosen pseudo-randomly at 120 Hz Data analyzed as “pulse-pairs”

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 Liquid Hydrogen target Length 1.54 m Refrigeration capacity 1 kW Beam heat deposit 800W Operating temperature 20K Flow rate 5 m/s

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 Spectrometer Dipole Magnetic chicane cut particles < 10 GeV Quadrupoles focus Møller electrons Synchrotron light blocked with Collimators. 60 m e-e

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 Electron Detector Full Azimuthal acceptance Radiation hard Fast pure Cerenkov signal Insensitive to low energy backgrounds Basic Idea: : quartz : copper light guide PMT shielding air

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 Statistics and systematics Integrating counting rate : 1. Additional random fluctuations : affect statistical precison 2. Constant shift : false asymmetry Origin : beam parameters variations (E,X,Y,  x,  y) Physics backgrounds Electronic crosstalk Pulse pair width ~ 200 ppm Raw asymmetry ~ 150 ppb

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 Energy dithering region Precise beam diagnostics High resolution BPM cavity monitors (energy position, angle) Toroids (beam current)  BPM ~2 microns  energy ~1 MeV Agreement (MeV) BPM24 X (MeV) BPM12 X (MeV)  toroid ~30 ppm

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 Luminosity Monitor Parallel plates more than 10 8 scattered electrons per spill at  lab ~ 1 mrad Null asymmetry test Enhanced sensitivity to beam fluctuations Density fluctuations monitor

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 Minimizing beam asymmetries A I ~0.5% A E ~0.1% Feedback loop (Cumulative) : A I < 200 ppb +/- 5 ppb A E < 20 ppb +/- 3 ppb Cumulative asymmetries with feedback on : Natural pulse to pulse jitter : (run I data)

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 Backgrounds controls Flux integration includes various residual backgrounds : eP ring Dilution effect False asymmetry Flux Radial and azimuthal scans Pion flux and asymmetry eP asymmetry

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 Scattered flux profile Very good agreement between Flux scans and MC (run I) Q 2 determination : = GeV-2 Radial and azimuth agreementFlux vs radial distance agreement e-e e-p

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 Correcting beam fluctuations Beam jitter enlarge distribution of asymmetry pairs. Two complementary method to correct for the beam noise : –DITHERING –REGRESSION Two main steps : 1.determine the dependance a of the detector integrated flux to beam parameters variations 2.Correct the detector asymmetry : Klystron EX dXYdY An Ax  Areg

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 Corrections method Run I:  A PV (regression-dithering) = ( 3.1 ± 11.8 ) ppb Run II:  A PV (regression-dithering) = ( 4.8 ± 4.2 ) ppb Very good agreement !

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 Analysis Blinded asymmetry Raw asymmetry distribution by pairs Gaussian over 5 orders of magnitude Raw asymmetry distribution by runs

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 Slow reversal 1. Insertable Half Wave Plate 2. Energy change 45 -> 48 GeV g-2 precession in A-Line Split data in four exclusive states :

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 Systematics summary Source Run I + II DA (ppb)Dilution Beam 1 st order 0 +/- 2- Beam 2 nd order 0 +/- 9- Transverse polarization -12 +/- 2- eP Background -30 +/ / High energy  3 +/ / Synchrotron  0 +/ / Neutrons / / Pions 0.5 +/ / Normalization factors Polarimetry / Geometry /

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 Run I+II Preliminary A PV = -161  21 (stat)  17 (syst) ppb Run I + II (preliminary) Run I A PV = -175  30 (stat)  20 (syst) ppb Run II A PV = -144  28 (stat)  23 (syst) ppb Official Run I result : PRL : hep/ex: First observation of parity violation in Møller scattering ~ 5  Q 2 = GeV2):

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 E158 projected The Weak Mixing Angle sin 2  eff (Q 2 =0.026 GeV 2 ) = ± ± (Run I + II, preliminary) Agreement with theory at the level of uncertainty prediction: ± (stat)(syst) sin 2  (M Z 2 )

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 Physics implication Parity is violated in Møller scattering Limit on  LL :  + LL >= 7,4 TeV  - LL >= 6,4 TeV Limits on extra Zs at the level of 700 GeV

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 Toward the final result Run III data analysis is being finalized Preliminary result on full data set very soon Systematics will improve Significant complementary constraint on new physics

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 Conclusion –Preliminary result on APV: -161 ± 21 ± 17 ppb –sin 2  W eff = ± ± (preliminary) –Inelastic e-p asymmetry at low Q 2 consistent with quark picture –First measurement of e-e transverse asymmetry –Preliminary result for all three runs soon ! - 10 ppb statistical error - Systematic error will be less than statistical error

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 Run 1: Spring 2002 Run 2: Fall 2002 Run 3: Summer 2003 Physics Runs Electrons on Target Run 1: Apr 23 12:00 – May 28 00:00, 2002 Run 2: Oct 10 08:00 – Nov 13 16:00, 2002 Run 3: July 10 08:00 - Sep 10 08:00, 2003 One g-2 flip in each run /2 flip roughly once in two days Run I data divided into 24 “slugs”

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 Higher orders Beam spotsize : higher moment in residual polarisation effect at the photocathode. Beam sub pulse fluctuations - Evidences in Run II analysis - monitored during Run III in order to estimate the systematics. - affect the OUT only

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 Wavelength (nm) Polarization (%) QE (%) Laser Power (µJ) Electrons per pulse New cathode Old cathode Very high-charge polarized electron beams are possible. No sign of charge limit! Small anisotropy in strain results in ~3% analyzing power for residual linear polarization. Source Photocathode New photocathode from NLC R&D effort. (T. Maruyama et al., Nucl.Instrum.Meth.A492: ,2002 ) Gradient-doped cathode structure. Low doping for most of active layer yields high polarization. High doping for 10-nm GaAs surface overcomes charge limit.

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 Acceptance segmentation Dividing the acceptance : 1. Monitoring the counting statistics versus  and  2. Checking systematics : building monopoles,dipoles amplify false asymmetries. X DIPOLE Y DIPOLE

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 End Station A setup Target chamber Dipoles Detector Cart Drift pipe Quadrupoles Concrete Shielding 60 m

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 Results of corrections Regression Dithering cxccxc pxcpxc pxppxp cxpcxp Run I:  A PV (regression-dithering) = (3.1 ± 11.8) ppb Run II:  A PV (regression-dithering) = (4.8 ± 4.2) ppb Asym width goes form ~500 ppm to 200 ppm

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 from A PV to sin 2  W eff where: is an analyzing power factor; depends on kinematics and experimental geometry. Uncertainty is 1.7%. (y = Q 2 /s) F brem = (0.90 ± 0.01) is a correction for ISR and FSR; (but thick target ISR and FSR effects are included in the analyzing power calculation from a detailed MonteCarlo study)  W eff is derived from an effective coupling constant, g ee eff, for the Zee coupling, with loop and vertex electroweak corrections absorbed into g ee eff

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 “ep” Detector Data Radiative tail of elastic ep scattering is dominant background 8% under Moller peak Additional 1% from inelastic e-p scattering Coupling is large: similar to 3 incoherent quarks Reduced in Run II with additional collimation

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 Backgrounds

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 CID Gun Vault IA Feedback Loop IA cell applies a helicity-correlated phase shift to the beam. The cleanup polarizer transforms this into intensity asymmetry. POS Feedback Loop Piezomirror can deflect laser beam on a pulse-to-pulse basis. Can induce helicity-correlated position differences. Polarized Source Laser System

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 “ANALYSIS OF AN ASYMMETRIC RESONANT CAVITY AS A BEAM MONITOR” (David H. Whittum (SLAC), Yury Kolomensky (Caltech). SLAC-PUB-7846; published in Rev.Sci.Instrum.70: ,1999.) RF Cavity BPM rf Cavity BPMs for E MHz Mixer Rf cavities resonate at 2856 MHz X cavity is TM 210 Y cavity is TM 120 Q cavity is TM 010

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 Beam Performance Electrons / pulse 6 x GeV, 3.5 x GeV Rep. rate120 Hz Intensity jitter0.5% Position jitter50 µm Spot size jitter5% of spot size Energy jitter0.03% rms Energy spread0.1% rms Polarization(85 ± 5)% Efficiency~(65-70)% Quantity Delivered (May 2002) All proposal goals achieved or exceededQuantity Run 1 Achieved AQAQ Alcove: 219 ± 319 ppb (AQ)(AQ) -8.4 ± 7.8 ppb * AEAE -0.1 ± 1.4 keV -1.2 ± 14.8 ppb (AE)(AE) ± 0.24 keV 0.05 ± 2.6 ppb (  x,  y) target (-16.6 ± 5.6 nm, -3.1 ± 4.0 nm)  (  x,  y) target (1.0 ± 0.6 nm, ± 0.9 nm) (  x,  y) angle (15.9 ± 9.4 nm, 4.8 ± 2.7 nm)  (  x,  y) angle (-2.7 ± 2.0 nm, 0.9 ± 1.0 nm) (  x,  y) spotsize (0.7 ± 1.9 nm, -1.7 ± 1.9 nm)

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 Luminosity Monitor Data Null test at level of 20 ppb Target density fluctuations small Limits on second order effects

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 Collimators

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 Pion Detector ~ 0.5 % pion flux ~ 1 ppm asymmetry < 5 ppb correction

SLAC E-158Antonin VACHERET, CEA-Saclay Dapnia/SPhNPAVI 2004 Qweak ~4 years Future Possibilities Part per billion measurements are now feasible: future measurements could improve sensitivity Challenging experiments Interest will depend on discoveries (or lack thereof) over the next few years, including LHC E158 (projected) DIS Jlab 12 GeV Møller Jlab 12 GeV