1. PHYS 5326 – Lecture #7 Improvements in Sin2qW
Monday, Feb. 10, 2003
Dr. Jae Yu
Improvements in Sin2qW
Interpretation of Sin2qW results
The link to Higgs
No class this Wednesday  Will make up on Fridays.
Monday, Feb. 10, 2003
PHYS 5326, Spring 2003
Jae Yu

2. How is sin2qW measured?
Cross section ratios between NC and CC proportional to sin2qW
Llewellyn Smith Formula:
Monday, Feb. 10, 2003
PHYS 5326, Spring 2003
Jae Yu

3. Experimental Variable
Define an Experimental Length variable
Distinguishes CC from NC experimentally in statistical manner
Compare experimentally measured ratio
to theoretical prediction of Rn
Monday, Feb. 10, 2003
PHYS 5326, Spring 2003
Jae Yu

4. Past Experimental Results
The yellow band represents a correlated uncertainty!!
Monday, Feb. 10, 2003
PHYS 5326, Spring 2003
Jae Yu

5. sin2qW Theoretical Uncertainty
Significant correlated error from CC production of charm quark (mc) modeled by slow rescaling mechanism
Suggestion by Paschos-Wolfenstein by separating n and`n beams:
Reduce charm CC production error by subtracting sea quark contributions
Only valence u, d, and s contributes while sea quark contributions cancel out
Massive quark production through Cabbio suppressed dv quarks only
Monday, Feb. 10, 2003
PHYS 5326, Spring 2003
Jae Yu

6. Improving Experimental Uncertainties
Electron neutrinos, ne, in the beam fakes NC events from CC interactions
If the production cross section is well known, the effect will be smaller but since majority come from neutral K (KL) whose x-sec is known only to 20%, this is a source of large experimental uncertainty
Need to come up with a beamline that separates neutrinos from anti-neutrinos
Monday, Feb. 10, 2003
PHYS 5326, Spring 2003
Jae Yu

7. Event Contamination and Backgrounds
SHORT nm CC’s (20% n, 10% `n)
m exit and rangeout
SHORT ne CC’s (5%)
neNeX
Cosmic Rays (0.9%)
LONG nm NC’s (0.7%)
hadron shower
punch-through effects
Hard m Brem(0.2%)
Deep m events
Monday, Feb. 10, 2003
PHYS 5326, Spring 2003
Jae Yu

8. Other Detector Effects
Sources of experimental uncertainties kept small, through modeling using n and TB data
Effect
Size(dsin2qW)
Tools
Zvert
0.001/inch
m+m- events
Xvert & Yvert
0.001 MC
Counter Noise
TB m’s
Counter Efficiency
0.0002
n events
Counter active area
0.0025/inch
n CC, TB
Hadron shower length
0.0015/cntr
TB p’s and k’s
Energy scale
0.001/1% TB
Muon Energy Deposit
0.004
n CC
Monday, Feb. 10, 2003
PHYS 5326, Spring 2003
Jae Yu

9. Measurements of ne Flux
Use well known processes (Ke3: )
Shower Shape Analysis can provide direct measurement ne events, though less precise
Weighted average used for ne dRnexp~0.0005
ne from very short events (En>180 GeV)
Precise measurement of ne flux in the tail region of flux  ~35% more `ne in `n than predicted
Had to require (Ehad<180 GeV)
due to ADC saturation
Results in sin2qw shifts by
Monday, Feb. 10, 2003
PHYS 5326, Spring 2003
Jae Yu

10. MC to Relate Rnexp to Rn and sin2qW
Parton Distribution Model
Correct for details of PDF model  Used CCFR data for PDF
Model cross over from short nm CC events
Neutrino Fluxes
nm,ne,`nm,`ne in the two running modes
ne CC events always look short
Shower length modeling
Correct for short events that look long
Detector response vs energy, position, and time
Continuous testbeam running minimizes systematics
Monday, Feb. 10, 2003
PHYS 5326, Spring 2003
Jae Yu

11. sin2qW Fit to Rnexp and R`nexp
Thanks to the separate beam  Measure Rn’s separately
Use MC to simultaneously fit and to sin2qW and mc, and sin2qW and r
Rn Sensitive to sin2qW while R`n isn’t, so Rn is used to extract sin2qW and R`n to control systematics
Single parameter fit, using SM values for EW parameters (r0=1)
Two parameter fit for sin2qW and r0 yields
Syst. Error dominated since we cannot take advantage of sea quark cancellation
Monday, Feb. 10, 2003
PHYS 5326, Spring 2003
Jae Yu

12. NuTeV sin2qW Uncertainties
Dominant uncertainty RL
0.08
DMW (GeV/c2)
Total Systematic Uncertainty
Total Physics Model Systmatics
RadiativeCorrection
Non-isoscalar target
Higher Twist
CC Charm production, sea quarks
Total Experimental Systematics
Energy Measurements
Event Length
ne flux
Statistical
d sin2qW
Source of Uncertainty
1-Loop Electroweak Radiative Corrections based on Bardin, Dokuchaeva JINR-E (1986)
Monday, Feb. 10, 2003
PHYS 5326, Spring 2003
Jae Yu

13. NuTeV vs CCFR Uncertainty Comparisons
}Beamline worked!
}Technique worked!
Monday, Feb. 10, 2003
PHYS 5326, Spring 2003
Jae Yu

14. Homework Assignments
Process the transferred TMB data files and convert them into TMBtree for root analysis
You can work together on this one
One person can produce TMBtree for all
Due next Monday, Feb. 17
Produce an electron ET spectrum of the highest ET electrons in your samples
Due next Wednesday, Feb. 19
Monday, Feb. 10, 2003
PHYS 5326, Spring 2003
Jae Yu