PHYS 5326 – Lecture #5
Monday, Feb. 12, 2007
Dr. Jae Yu
1. ILC News from Beijing
2. Interpretation of sin2qW
3. sin2qW link to Higgs
Monday, Feb. 12, 2007
PHYS 5326, Spring 2007
Jae Yu
1
ILC RDR from Beijing
• Global Design Effort (GDE) headed by Barry Barish
of CalTech completed a Reference Design Report
(RDR)
– Worldwide group working on ILC machine design
– Defines the baseline design of the ILC and provides the
cost estimate for an ILC
• Baseline design parameters
–
–
–
–
CMS Energy: 200 – 500GeV scannable
Total length: 31km
Luminosity: L = 2 1034 cm 2 s 1
Single interaction region two detector in push-pull mode
Monday, Feb. 12, 2007
PHYS 5326, Spring 2007
Jae Yu
2
ILC RDR from Beijing
• Baseline cost estimate
– ILC Value units to provide cost in universally
understandable price
• Lowest reasonable price for required quality
– Shared cost: $4.87B
– Site specific cost: $1.78B
• This is the cost for tunneling, foundation, geological issues, etc
– Labor cost: 13,000 Man-years
– Not included in the cost estimate
•
•
•
•
Engineering design, preparation cost for R&D
Detectors and associated R&D
Contingencies for risks
Escalation (inflation)
Monday, Feb. 12, 2007
PHYS 5326, Spring 2007
Jae Yu
3
ILC RDR from Beijing
• The next steps
– Engineering design report by 2010
• Should include complete design of the machine except for the
site specific portion of it
• Refined cost estimate
– Accept expression of interest (EOI) for hosting the ILC
from countries from now till 2011
– Site selection process begins shortly as EOI’s collected
– Construction of the machine begins 2011 or so
• Detector R&D and selection should complete by
2010 – 2011 time scale
Monday, Feb. 12, 2007
PHYS 5326, Spring 2007
Jae Yu
4
MC to Relate Rnexp to Rn and sin2qW
• Parton Distribution Model
– Correct for details of PDF model  Used CCFR data for PDF
• To minimize systematic effects
– Model cross over from short nm CC events
Monday, Feb. 12, 2007
PHYS 5326, Spring 2007
Jae Yu
5
MC to Relate Rnexp to Rn and sin2qW
• 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. 12, 2007
PHYS 5326, Spring 2007
Jae Yu
6
sin2qW Fit to Rnexp and R`nexp
• Thanks to the separate beam  Measure Rn’s separately
• Use MC to simultaneously fit Rnexp and Rnexp to sin2qW and
mc, and sin2qW and r
n (n )
R
n (n )
σNC
 n (n )
σ CC
n (n )


1
5
σ
 ρ2   sin2θ W  sin4 θ W  1  nCC(n )
2
9
σ CC



 

• Rn Sensitive to sin2qW while R`n isn’t
Rn is used to extract sin2qW and R`n to control systematics
Why???
Monday, Feb. 12, 2007
PHYS 5326, Spring 2007
Jae Yu
7
sin2qW Fit to Rnexp and R`nexp
• Single parameter fit, using SM values for EW parameters
(r0=1)
sin θ W  0.2277  0.0013 (stat)  0.0009 (syst)
2
2
mc  1.32  0.09 (stat)  0.06 (syst)  mc  1.38  0.14 GeV/c as input
•Two parameter fit for sin2qW and r0 yields
sin θ W  0.2265  0.0031
2
ρ0  0.9983  0.040
Monday, Feb. 12, 2007
PHYS 5326, Spring 2007
Jae Yu
Syst. Error dominated
since we cannot take
advantage of sea quark
cancellation
8
NuTeV sin2qW Uncertainties
Dominant
uncertainty
d sin2qW
Source of Uncertainty
Statistical
0.00135
ne flux
0.00039
Event Length
0.00046
Energy Measurements
0.00018
Total Experimental Systematics
0.00063
CC Charm production, sea quarks
0.00047
Higher Twist
0.00014
Non-isoscalar target
0.00005
n /n
0.00022
RadiativeCorrection
0.00011
RL
0.00032
Total Physics Model Systmatics
0.00064
Total Systematic Uncertainty
0.00162
DMW (GeV/c2)
Monday, Feb. 12, 2007
1-Loop Electroweak Radiative
Corrections based on Bardin,
Dokuchaeva JINR-E2-86-2 60 (1986)
shell)
δsin2θ(On
W
0.08
PHYS 5326, Spring 2007
Jae Yu
 M2t   175GeV 2 
 0.00022  

  50GeV 2 


 MH 
0.00032  ln 

 150GeV 
Mhiggs
Term
Mt
Term
9
NuTeV vs CCFR Uncertainty Comparisons
}Beamline worked!
}Technique worked!
Monday, Feb. 12, 2007
PHYS 5326, Spring 2007
Jae Yu
10
Comparison of New sin2qW
Shell
sin2θOn
 0.2277  0.0013 (stat)  0.0009 (syst)
W
M2W
sin θ
 1 2
MZ
 M W OnShell  80.14  0.08 GeV/c 2
2
Onshell
W
Comparable precision but value smaller than other measurements
2.5 
deviation!
Monday, Feb. 12, 2007
PHYS 5326, Spring 2007
Jae Yu
11
SM Global Fits with New Results
Without NuTeV
c2/dof=20.5/14: P=11.4%
With NuTeV
c2/dof=29.7/15: P=1.3%
Confidence level in upper
Mhiggs limit weakens slightly.
LEP EWWG: http://www.cern.ch/LEPEWWG
Monday, Feb. 12, 2007
PHYS 5326, Spring 2007
Jae Yu
12
Tree-level Parameters: r0 and sin2qW(on-shell)
sin2θ W  0.2265  0.0031
ρ0  0.9983  0.040
2 (Onshell)
W
δsin θ
 M2t   175GeV 2 
 0.00022  

  50GeV 2 


 MH 
0.00032  ln 

 150GeV 
• Either sin2qW(on-shell) or r0 could agree with SM but both agreeing
simultaneously is unlikely
Monday, Feb. 12, 2007
PHYS 5326, Spring 2007
Jae Yu
13
Model Independent Analysis
• Rn`n can be expressed in terms of quark couplings:
- 
 -
 n N  n X 
n n 
  g2  r  1g2
R   - 
L
R


  n N     X 


σ νN   X
1
r

Where
  
2
σ νN 
X




Paschos-Wolfenstein formula can be expressed as
σ
R 
σ

ν
NC
ν
CC
σ
σ
Monday, Feb. 12, 2007
ν
NC
ν
CC
ν
ν
R

rR

2 1
2
 gL2  gR2
 ρ   sin θ W  
1 r
2

PHYS 5326, Spring 2007
Jae Yu
14
Model Independent Analysis
• Performed a fit to quark couplings (and gL and gR)
– For isoscalar target, the nN couplings are
5 4 
1
2
g  u  d  ρ   sin θ W  sin θ W 
9
2

2
2
2
2 5
gR  uR  dR  ρ0 sin4θ W
9
exp
exp
R
– From two parameter fit to Rn and n
2
L
2
L
2
L
2
0
gL2  0.3005  0.0014 (SM: 0.3042 -2.6 deviation)
gR2  0.0310  0.0011 (SM: 0.0301  Agreement)
Monday, Feb. 12, 2007
PHYS 5326, Spring 2007
Jae Yu
15
Model Independent Analysis
Difficult to explain the
disagreement with SM by:
Parton Distribution Function or
LO vs NLO or Electroweak
Radiative Correction: large
MHiggs
Monday, Feb. 12, 2007
PHYS 5326, Spring 2007
Jae Yu
16
What is the discrepancy due to (Old Physics)?
• R- technique is sensitive to q vs`q differences
and NLO effect
– Difference in valence quark and anti-quark
momentum fraction
• Isospin symmetry assumption might not be
entirely correct
– Expect violation about 1%
→NuTeV reduces this effect by using the ratio of n and `n
cross sections
→Reducing dependence by a factor of 3
Monday, Feb. 12, 2007
PHYS 5326, Spring 2007
Jae Yu
17
What is the discrepancy due to (Old Physics)?
• s vs`s quark asymmetry
– s and `s needs to be the same but the momentum
could differ
• A value of Ds=xs -x`s ~+0.002 could shift sin2qW by 0.0026, explaining ½ the discrepancy (S. Davison, et. al.,
hep-ph/0112302)
• NuTeV di-m measurement shows that Ds~-0.0027+/-0.0013
Use opposite sign di-m events
to measure s and `s.
Monday, Feb. 12, 2007
PHYS 5326, Spring 2007
Jae Yu
18
What is the discrepancy due to (Old Physics)?
• NLO and PDF effects
– PDF, mc, Higher Twist effect, etc, are small changes
• Heavy vs light target PDF effect (Kovalenko et al., hepph/0207158)
– Using PDF from light target on Iron target could make up the
difference  NuTeV result uses PDF extracted from CCFR
(the same target)
Monday, Feb. 12, 2007
PHYS 5326, Spring 2007
Jae Yu
19
nens Oscillations with Large Mn
• LSND result implicate a large Dm2 (~10 — 100eV2)
solution for ne oscillation MiniBooNe at FNAL is
running to put the nail on the coffin
• How would this affect NuTeV sin2qW?
1 R  rR
sin θ W  
2
1 r
ν
2
ν
and
Rn 
NnShort  NnMC
e
NnLong

MC
MC
P
N

N
P

N
If nens with n e n s then n e n e n e n e n e 1-Pn e n s

Thus, MC will subtract more than it is in nature, causing
measured Rn to be smaller and thereby increasing sin2qW
Monday, Feb. 12, 2007
PHYS 5326, Spring 2007
Jae Yu
20
New Physics: Interactions from Extra U(1) – Z’
• Extra U(1) gauge group giving
rise to interactions mediated
by heavy Z’ boson (MZ’>>MZ)
• While couplings in these
groups are arbitrary, E(6)
gauge groups can provide
mechanism for extra U(1)
interaction via heavy Z’.
• Can give rise to gR but not gL
which is strongly constrained
by precision Z measurement
Monday, Feb. 12, 2007
PHYS 5326, Spring 2007
Jae Yu
21
What other explanations (New Physics)?
• Heavy non-SM vector boson
exchange: Z’, LQ, etc
– Suppressed Znn (invisible)
coupling
– LL coupling enhanced than LR
needed for NuTeV
Both precision data
are lower than SM
Monday, Feb. 12, 2007
PHYS 5326, Spring 2007
Jae Yu
22
What other explanations (New Physics)?
• Propagator and coupling corrections
– Small compared to the effect
• MSSM : Loop corrections wrong sign and small for
the effect
• Many other attempts in progress but so far nothing seems
to explain the NuTeV results
– Lepto-quarks
– Contact interactions with LL coupling (NuTeV wants mZ’~1.2TeV, CDF/DØ:
mZ’>700GeV)
– Almost sequential Z’ with opposite coupling to n
Langacker et al, Rev. Mod. Phys. 64 87; Cho et al., Nucl. Phys. B531, 65; Zppenfeld
and Cheung, hep-ph/9810277; Davidson et al., hep-ph/0112302
Monday, Feb. 12, 2007
PHYS 5326, Spring 2007
Jae Yu
23
Linking sin2qW with Higgs through Mtop vs MW
One-loop
correction to
sin2qW
shell)
δsin2θ(On
W
Monday, Feb. 12, 2007
 M2t   175GeV 2 
 MH 
 0.00022  

0.00032

ln



  50GeV 2 
150GeV




PHYS 5326, Spring 2007
Jae Yu
24
Homework Assignments
• Draw a few additional Feynman diagrams for
higher order GSW corrections to n-N scattering
at the same order as those on pg 4 of the
previous lecture
– Due: One week from today, Mon., Feb. 19
Monday, Feb. 12, 2007
PHYS 5326, Spring 2007
Jae Yu
25