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" EXPERIMENTAL METHOD" STATISTICAL ERROR ( 5 × 108 Pulses; ~½ of E158 running)
δAD/AD = 0.006
δ sin2θW = 0.0006
" EXPERIMENTAL SYSTEMATIC ERRORS
δAD/AD = 0.006
δ sin2θW = 0.0006 (ASSUMING STANDARD MODEL)
" THEORETICAL SYSTEMATIC ERRORS
δ sin2θW = 0.0004 (ASSUMING STANDARD MODEL)
" TOTAL ERRORδAD/AD = 0.008
δ sin2θW = 0.0009 (ASSUMING STANDARD MODEL)
OUTLINE
" DEEP INELASTIC SCATTERING ( e + d → e + X )
" MEASURE ASYMMETRY: A D =(σR
−σL) / (σ
L+σ
R)
AD ≈ 10−4 Q2 ≈ 0.002
" POLARIZED ( 85%) ELECTRON BEAM (E= 36, 39 GeV)" UNPOLARIZED LD 2 TARGET (1.0 m)
" 2 MAGNETIC SPECTROMETERS" LEAD GLASS DETECTORS
COUNT INDIVIDUAL ELECTRONS INSENSITIVE TO SOFT BACKGROUND
" KINEMATICS
16 < Q2 < 26 GeV2 (AVOID HIGHER TWIST)
0.3 < x < 0.7 9 < E′ < 17 GeV
10 < W2 < 36 GeV2 (DIS)
EXPERIMENTAL METHOD
" HIGH STABILITY FROM E158NEW TOROIDSNEW POSITION MONITORSNEW ACCELERATOR FEEDBACK LOOPS
" HIGH INTENSITY FROM E158 " POLARIMETER FROM SLD
BEAM
MOMENTUM FOCUSING
� ~0.8 msr ACCEPTANCE FOR 9 < P < 16 GeV
" LEAD GLASS ARRAYS FROM E142−E155X20 Vertical x 10 Horizontal BLOCKS: 6 cm squareRESOLUTION: σ/E < 5% IN OUR ENERGY RANGE
COLLIMATORS DETERMINE FIDUCIAL REGION" ELECTRONICS:
250 MHz FLASH ADCs on EACH BLOCK10 BIT RESOLUTIONDEVELOPED FOR KAMLAND by BERKELEY
" COUNTING SINGLE ELECTRONS
" RATE DEPENDENCESPACE AND TIME SEPARATION OF PARTICLESPULSE HEIGHT AND SHAPE FOR OVERLAPSMEASURE RESIDUAL RATE DEPENDENCE
DETECTOR
Momentum Range of electronshitting a given row of PbG blocks.Red curve is minimum P cut for 1 e.Blue curve is minimum P cut for 2 e.
Number of events/spill in eachrow of PbG blocks.
14 electrons/spill : Dashed blue curve 4 pions/spillSolid Red Curve is e and π
" BEAM POLARIZATION
" MEAN Q 2
" ELECTROMAGNETIC RADIATIVE CORRECTION" PILE UP AND DEAD TIME" TARGET PURITY AND DENSITY" PION CONTAMINATION" FALSE ASYMMETRIES" PAIR SYMMETRIC BACKGROUND
EXPERIMENTAL SYSTEMATIC ERRORS
" COMPTON POLARIMETERPHOTON−ELECTRON SCATTERINGRADIATIVE CORRECTIONS <0.1%USED AT SLD WITH 0.5% ACCURACYHIGH POWER LASERDETECT SCATTERED ELECTRONDETECT SCATTERED PHOTON (INDEPENDENT MEASUREMENT)MEASURE CONTINUOUSLYMEASUREMENT TAKES ~5 MINUTES
BEAM POLARIZATION
ESA
POLARIMETER ANALIZING POWER AND RATES DETECTOR EDGES AND BACKGROUND
Signal
Background
" BACKGROUNDS" FROM ELECTRON BEAM
e.g. BREMSSTRAHLUNG FROM GAS IN BEAMLINE� MEASURE WITH LASER OFF
� LASER PULSES AT 17 Hz
ELECTRONIC NOISE: PULSING LASER� MEASURE WITH BEAM OFF
" SLD EXPERIENCE (Mike Woods)
SIMILAR SETUP ⇒ δPe = 0.5%
" NLC NEEDS 0.25% ACCURACYIMPORTANT TO TEST TECHNIQUESESA BEAM NOW SIMILAR TO NLC BEAM
" WE CAN DO δ P = 0.3%
BEAM POLARIZATION
" NEED TO KNOW: δ<Q2>/<Q2> ≤ 0.3%
" Q2 = 4 E E′ SIN2θ /2 (θ =12o ~200 mr)
" MEASURE δ E/E ≤ 0.1%
ZERO CROSSING OF BEAM POLARIZATION
" OPTICS MEASUREMENTS FOR E′ (0.2%) & θ (0.2 mr)
" METHODS FROM PAST EXPERIMENTS
FLOATING WIRE USED IN E140 (We have shorter spectrometer)
CENTRAL ANGLE ±0.05 mr
CENTRAL MOMENTUM δE′/E′ ±0.03%
AGREEMENT WITH ELASTIC PEAK 0.13%
AVERAGE Q 2 OF EVENTS
FIELD MAPS OF MAGNETS AND SURVEY
SPECIAL ACCEPTANCE RUNS
SHORT TARGETS IN VARIOUS POSITIONS
BEAM ENERGY SWEEP (E154)
QUADS ON / OFF
APERATURE DEFINING MASKS (E154)
CROSS SECTION WELL KNOWN FROM PREVIOUS FITS
" OVERALL UNCERTAINTY: δ<Q2>/<Q2> ≤ 0.3%
AVERAGE Q 2 OF EVENTS
" WELL KNOWN TECHNIQUE
Mo and Tsai
Bardin
USED IN ALL ELECTRON SCATTERING EXPERIMENTS
INTERNAL CORRECTIONS
AT THE SCATTERING NUCLEON
EXTERNAL CORRECTIONS
ENERGY LOSS IN TARGET
POLARIZATION LOSS IN TARGET
" OUR KINEMATICS HAVE SMALL CORRECTIONS
EM RADIATIVE CORRECTIONS
" INTERNAL COMPARE Mo −Tsai WITH Bardin
AVERAGE DIFFERENCE δAD/AD = < 0.001
" EXTERNAL:
USE DIFFERENT FITS TO F2(X,Q2) AS INPUT:
GET AVERAGE DIFFERENCE IN ASYMMETRY
RESONANCE MODELS δAD/AD < 0.001
DIS MODELS δAD/AD ~ 0.002
" TOTAL ERROR: δAD/AD < 0.003
EM RC ERROR DETERMINATION
.
THEORETICAL SYSTEMATIC ERRORS
" AD IS EXPERIMENTALLY MEASURED
� FOCUS: EXTRACT sin2θW FROM ADASSUME STANDARD MODEL
sin2θW IS BURIED IN THE C ij
C1U ~ −1/2 +4/3 sin2θW
" ERRORS FROM R’s, Y, ETC.
" R = fi(x)/(Σf) : Fraction of sea or valence quarks
" Rc, Rs SMALL; R V ~ 1.0 at our values of x
Determined from Parton Distribution Functions
CTEQ, MRS Groups Provide Errors (2002)
Over 25 Distributions Considered
Uncertainties from CTEQ Errors, and Most Different Distribution
" δ sin2θW ~ 0.0002
"Ad Depends on Couplings and Quark Distributions
PARTON DISTIBUTIONS
" Higher Order pQCD easy to do." Higher Twist
DECREASES ~ Q−2 Compared to leading twist 2
Q2 =20: δsin2θW < 2×10−5 (Castorina & Mulders)
NACHTMANN MOMENTS OF F 2 : HT < .4% OF LT
(Osipenko et al.)
WE USE CONSERVATIVE δsin2θW ~ 0.0001
LOI at JLAB for Experiment at low Q 2
QCD and HIGHER TWIST
" NO VIOLATION : un = dp ; up = dn; sp = sn ; cp = cn
Assumes that n and p are perfect isospin doublet Broken by E & M Mp ≠ Mn But only by about 0.1%
md/mu ≈1.8 ; md−mu ≈3 MeV : ~ 1% of ΛQCD
So Expect δ(un −dp) ≈ 0" CAN BE CALCULATED
MIT bag modelMeson Cloud Model
AVERAGE OF MODELS: δ sin2θW ≈0.0002 ± 0.0002SAME MODEL FOR NuTeV: 0.0015
CHARGE SYMMETRY VIOLATION IN DEUTERON
"Very Well Determined in Standard Model
" Depends on α, MZ, MW, MH ,Q2, sin2θW
C1U
= ρ′(−1/2 +4/3 κ′sin2θW) + λ1u
ρ′,κ′≈1; λ1u≈0" Overall Correction to Asymmetry < 1%" Weak Dependence on Higgs Mass
"Cut off’s depend on Q2 , not on quark masses" Jens Erler & Michael Ramsey−Musolf in collaboration
" δ sin2θW ≈ 0.0002
ELECTROWEAK RADIATIVE CORRECTIONS
" EMC EFFECT IN DEUTERIUM?σD/ (σp + σn) ~ 0.98 to 1.00 IN OUR X RANGE
IF PARTON DISTRIBUTION SHIFTED TO LOWER X� Rs, Rc, Rv RATIOS UNCHANGED.
� NO EFFECT ON ASYMMETRYVALENCE & SEA SHIFTED DIFFERENTLY (Frankfurt & Strikman)
� δ sin2θW ≈ 0.00002" NUCLEAR EFFECTS SHOULD BE SAME FOR γ & Z EXCHANGE
NO CHANGE IN ASYMMETRYONLY NEUTRAL CURRENTS
" CALCULATION BEING DONE BY Alekhin, Kulagin and Liuti
NULEAR EFFECTS
.
" MEASURES UNIQUE INDEPENDENT PARAMETERS Cij" SPECIFIC SENSITIVITY TO NEW PHYSICS" FACTOR OF 20 DECREASE IN ERRORS
" δ sin 2θW = 0.0009 (ΑSSUMING STANDARD MODEL)
NuTeV ~ 0.0016 (εL , εR)
E158 ~ 0.001 ( lepton couplings)"THEORETICAL CORRECTIONS SMALL"THEORETICAL SYSTEMATIC ERRORS SMALL ( 0.0004) "IN A LONG TRADITION OF HIGH ACCURACY
MEASUREMENTS IN ESA"EXPERIENCED COLLABORATION READY TO START "LOW COST: < 0.001 NLC"WANT RESULTS BEFORE LHC ( BUT DIFFERENT THAN LHC)
SUMMARY
OPTICS
Errors on Asymmetry from Uncertainty in Parton Distributions
UNCERTAINTY ON R = σL/σT
� R ~ 0.03± 0.025 (E140)
� AVERAGE: δ sin2θW ≈0.0001
ElectroWeak Corrections
� Running of αs due to γ−Z Mixing
� Axial−vector renormalization: small
� Anapole moment: negligible
� Charge−radii: 0.1% on Ad.
� WW and ZZ box diagrams: < 0.1% on Ad.
� γ−Z box diagram: < 0.1% uncertainty on Ad
� OVERALL UNCERTAINTY:
δ sin2θW ≈ 0.0002
INTERNALDIFFERENT CODESAvg < 0.001
EXTERNAL DIFFERENT MODELSAvg = 0.002
RADIATIVE CORRECTIONS
RATE DEPENDENCE
� SPACE AND TIME SEPARATION OF SHOWERS
OVERLAP of 2 electrons : 4% of electrons merge
� ENERGY SEPARATION
2 Electrons of E > Emin
Additional separation of factor of 15� Energy Straggling� Gaps between blocks
Leaves 0.3% confusion between 1 electron and 2 electrons
� MEASURE RATE DEPENDENCE OF CONFUSION
Another factor of 10
δ ΑD/AD ~ 0.03%
REQUEST FOR BEAM
ENERGY PULSES 35.6 2 × 108
38. 8 2 × 108
35.6 4 × 107 Checkout
35.6 3 × 107 backgrounds
12 to 38 3 × 107 energy scan
TOTAL 5 × 108 2.3 Mo @120 Hz, 70% eff
SPECTROMETERS� 2 IDENTICAL SPECTROMETERS AT ± 120
� QUAD−DIPOLE−QUAD
� FOCUS MOMENTUM
� MAXIMIZE ACCEPTANCE USING EXISING MAGNETS
� ~0.8 msr ACCEPTANCE FOR 9 < P < 16 GeV
� 18 PARTICLES/SPILL/SPECTROMETER
� 14 e− SPREAD UNIFORMLY OVER DETECTOR
� 4 π /spill CONCENTRATED AT BOTTOM
" USE OLDBEAM FROM E158 (VERY STABLE )TARGET FROM E158SPECTROMETER DESIGN FROM E155XMAGNETS FROM E1DETECTOR FROM E142 −E155XCALIBRATION METHOD FROM E140XCOMPTON POLARIMETER FROM SLDPEOPLE FROM ALL THE ABOVE + MANY MORE
" USE NEWFLASH ADC FROM BERKELEY /KAMALAND
EXPERIMENTAL METHOD
" π /e < 1 IN ALL ROWS (AVERAGE: 0.25) ⇒
LEAD GLASS SUFFICIENT FOR REJECTION
PULSE HEIGHT AND SHAPE
REJECT 95% OF π 1% UNDER ELECTRON PEAK
� FIT FOR REMAINDER
" 2nd LAYER OF LEAD GLASS
e SHOWER STOPPED EARLY
EXTRA REJECTION
MEASURE π ΑSYMMETRY
" MEASURE π /e TO BETTER THAN 10%
" DONE IN MANY PREVIOUS EXPERIMENTS
π CONTAMINATION
pi/e=3E154