Transcript neutral current overview

Parity Violation
and determination of sin2W
Shufang Su • U. of Arizona
Hall C 2006 summer workshop
Outline
 Determination of sin2eff
 Neutral current measurements
– parity violating electron scattering (PVES)
ee Moller scattering (SLAC E158, Jlab 12 GeV)
ep elastic scattering (Jlab Qweak)
- Parity violation deep inelastic scattering (DIS-parity)
– atomic parity violation (APV)
– neutrino-nucleus deep inelastic scattering (NuTeV)
probe new physics beyond SM
some QCD issue
 Conclusion
S. Su
2
Low energy precision measurements
 address questions difficult to study at high energy
weak interactions (parity violation)
 high precision low energy experiment available
size of loop effects from new physics: (/)(M/Mnew)2
- muon g-2: M=m , new  2x10-9, exp < 10-9
– -decay, -decay: M=mW , new  10-3, exp  10-3
– parity-violating electron scattering: M=mW , new  10-3,
QWe,p  1-4 sin2W  0.1
 1/QWe,p 10 more sensitive to new physics
 need exp  10-2 “easier” experiment
 probe new physics off the Z-resonance
- sensitive to new physics not mix with Z
S. Su
4
Møller Scattering
e
e
e
e
g
Q-Weak (JLab)
DIS-Parity
e
e
g Z
Z
g
Z
p
n
e
• Purely Leptonic
• Coherent quarks in P
• Results in ~2008
• 2(2C1u+C1d)
Atomic Parity Violation
e
g
Cs133
Z
• Coherent quarks in entire nucleus
• Nuclear structure uncertainties
• -376 C1u – 422 C1d
S. Su
e
• Isoscaler quark scattering
• (2C1u-C1d)+Y(2C2u-C2d)
Neutrino Scattering
n
n

W
+
n
Z
• Quark scattering (from
nucleus)
• Weak charged and neutral
current difference
5
Courtesy of P. Reimer and R. Arnold
Test of sin2W running
Weak mixing angle sinW
g sinW = g’ cosW = e
0.25
QWe
current
0.245
future
SM
0.24
Jlab Moller
Q W (p)
Qweak
SLAC E158
eD-DIS
n-DIS
Q W (e)
A FB
NuTeV
APV
0.235
Cs APV
Z-pole
0.23
DIS-parity
Standard Model Prediction
Erler, Kurylov & Ramsey-Musolf,
Phys. Rev. D 72, 073003 (2005)
0.225
S. Su
0.001
0.01
0.1
1
Q [GeV]
10
100
1000
6
Precision of sin2W determination
Measurement
Δsin2θW/sin2θW
Δsin2θW
Z-pole
0.07%
0.00016
0.5% Qw(Cs)
0.7%
0.0016
NuTeV
0.7%
0.0016
13.1% Qw(e)SLAC
0.5%
0.0013
2.5% Qw(e)Jlab
0.1%
0.00025
4% QW(p)
0.3%
0.00072
0.8% DIS-parity
0.45%
0.0011
S. Su
(on par with Z pole)
Talk by D. Mack
Talk by K. Paschke
7
Sensitivity to new physics scale
Ramsey-Musolf(1999)
: new physics scale
O(1)
courtesy of Carlini
Take  QWp=4%
● probe new physics scale comparable to LHC
● confirmation of LHC discovery (couplings, charges)
S. Su
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NC exp as a indirect probe of new physics
SM is a low energy approximation of a more fundamental theory
 SUSY: minimal Supersymmetric extension of SM (MSSM)
spin differ by ½
each SM particle
superpartner
- with R-parity : loop corrections
- without R-parity: tree-level contribution
 extra Z’
- exists in extension of SM
- constraints from Z-pole observable (mix with Z)
 leptoquark
 extra-dimension …
S. Su
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Misc. model sensitivities (non-SUSY)
Courtesy of D. Mack
Experiment
Colliders
(LEP2, CDF,Hera)
Z’
M(ZΧ) M(ZLR)
(TeV) (TeV)
.67
.80
Leptoquarks
MLQ(up) MLQ(down)
(TeV)
(TeV)
“1.5”
Compositeness (LL)
e-q
e-e
(TeV)
(TeV)
“1.5”
0.5% Qw(Cs)
1.2
1.3
4.0
3.8
28
---
13.1% Qw(e)
.66
.34
---
---
---
2.5% Qw(e)
1.5
.77
---
---
---
29
4% Qw(p)
.95
.45
3.1
4.3
28
----
exists!
13
exists!
under construction
scaled from R-Musolf, PRC 60 (1999), 015501
S. Su
Collider limits from Erler and Langacker, hep-ph/0407097
10
Moller and Qweak
A
V
weak charge
S. Su
QWf = 2gfV = 2 If3 -4Qfs2
11
Moller and Qweak
QWe,p tree
QWe,p loop
q2
ALR
exp precision
 sin2W
QWp (Qweak)
QWe (SLAC)
QWe (Jlab)
1-4s2
0.0721
0.03 GeV2
-0.29 ppm
4%
0.0007
-(1-4s2)
-0.0449
0.026 GeV2
0.008 GeV2
-0.131 ppm -0.04 ppm
13%
2.5%
0.0013
0.00025
 clean environment: Hydrogen target
 theoretically clean: small hadronic uncertainties
 tree level  0.1  sensitive to new physics
S. Su
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MSSM correction to weak charge
Kurylov, Ramsey-Musolf, Su (2003)
QWf =  (2Tf3 - 4Qf  s2) + f
 QWe and QWp
correlated
dominant :  (<0)

negative shift in sin2W
MSSM
 (QWp)SUSY / (QWp)SM < 4%,  (QWe)SUSY / (QWe)SM < 8%
S. Su
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R-parity violating (RPV)
• RPV operators contribute to QWe,p at tree level
Kurylov, Ramsey-Musolf, Su (2003)
Exp constraints
QpW




MSSM
RPV 95% CL
 decay:
|Vud| = -0.00145loop
 0.0007
No SUSYCsDM
APV(Cs):
 QW = -0.0040  0.0066
Re/ :
 Re/ = -0.0042  0.0033
G :
 G = 0.00025  0.00188
4% Qweak
G
S. Su
I) Obtain 95% CL allowed region
in RPV coefficients Future 2.5%
Moller
II) Evaluate  QWe and  QWp
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Correlation between QWp , QWe
 Distinguish new physics
 exp
Erler, Kurylov and Ramsey-Musolf (2003)
 QWp
 0.0029
 QWe
 0.0052
 MSSM:
Distinguish
via APV QWCs
 extra Z’:
 RPV SUSY
 leptoquark
SM
SM
Combinations of NC exps could be used to distinguish various new physics
S. Su
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Extract QWp
use kinematics to simplify: at forward angle 
Musolf et. al., (1994)
?
 measure F(,q2) over finite range in q2, extrapolate F
to small q2
existing PVES: SAMPLE, HAPPEX, G0, A4
 minimize effect of F by making q2 small
 q2  0.03 GeV2, still enough statistics
  QpW / QpW | hadronic effects  2 %
S. Su
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QCD correction to ep scattering
Box diagram contribution to QWP
e
p
e
p
suppression
g
p
26%
 QWP
W
kloop
ne »n O(mW)
p
Z
Z
e
g
g
Z
p
3%
kloop » O(mZ)
|CgW|  2using (CKM
unitarity)
OPE (pQCD)
|CgZ|  2
0.08%
 QWP (QCD) 0.7%
e
p
e
non-calculable
Similar to nuclear -decay
ep W
S. Su
e
Z
W
e
Erler, Kurylov and Ramsey-Musolf (2003)
p
e
p
6%
QCD  kloop  O(mZ)
non-perturbative
0.65%
Total theoretical uncertainty » 0.8%
17
DIS-parity: eD scattering
Longitudinally polarized electrons
on unpolarized deuterium target
— Cahn and Gilman, PRD 17 1313 (1978).
S. Su
e
e
18
Sensitivity to sin2W
Large asymmetry
Q2 = 3.7 GeV2, Ad = 0.0003
“Easy experiment”
 Ad/Ad = 0.8%   sin2 W/sin2W = 0.45%
S. Su
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Ranges of C1u, C1d, C2u, C2d
Courtesy of P. Reimer
S. Su
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SUSY contributions
DIS-parity
S. Su
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Atomic parity violation
Two approaches
● rotation of polarization plane of linearly polarized light
● apply external E field  parity forbidden atomic transition
Boulder group: cesium APV 0.35% exp uncertainty
atomic
structure
+ 2.5
 deviation
1%
wood et. Al. (1997)
(2002)
Blundell
et. al.
(1990, 1992)  Derevianko (2000), Dzuba et. al. (2001)
– Breit
interaction
finite nuclear size
Dzuba et. Al. (1989)
nucleon
substructure
– Uehling
Johnson et. al. (2001),
Milstein
et. al. (2002)
 reduced
error potential
0.6% (exp 
+ theory)
– QED dipole
self-energy
vertex  nuclear spin-dependent term
via transit
amplitudeand
measurement
 »  0.15%
u
d
Dzuba
et.
Al. (2002),
Kuchiev
and Flambaum
(2002), Milstein et. al. (2002)
QW
(Z,N)=(2Z+N)Q
Bennett
and
Wieman
(1999)
W +(Z+2N)QW
QWCs (exp)
S. Su
Pollock and Wieman (2001)
(1994)
Cs(SM)=-73.16
¼
sin2W)-N
¼ -N Q Musolf
= Z(1-4
-72.69
0.48
agree
W
Erler, Kurylov and Ramsey-Musolf (2003)
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Sensitivity to new physics
 Distinguish new physics
•  QW (Z,N)=(2Z+N)  QWu +(2N+Z)  QWd
u
MSSM  QW >0
 QW <0
d

 QW(Z,N) / QW(Z,N) < 0.2 % for Cs
 QWp
• exp
 0.0029
 QWe
 QWCs
 0.0052
• MSSM:
small
• extra Z’:
sizable
SM
SM
Erler, Kurylov and Ramsey-Musolf (2003)
S. Su
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Outlook -- APV
● Paris group: more precise Cs APV
● Seattle group: Ba+ APV 6S1/2  5D3/2
● Berkeley group: isotope Yb APV
eliminate large atomic structure theory uncertainties
Ramsey-Musolf(1999)
0.2% uncertainties
comparable to QWp in sensitivity to new physics
S. Su
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NuTeV experiment
NC
CC
gL,R2=(uL,R)2+(dL,R)2
Rn=-0.0033
 0.0015
-
Rn=-0.0019
 0.0026
• exp fit: (gLeff)2=0.30050.0014, (gReff)2=0.03100.0011
• SM EW fit: (gLeff)2=0.3042, (gReff)2=0.0301
S. Su
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NuTeV anomaly
• exp fit (=1): sin2Won-shell = 0.2277  0.0016
• SM fit to Z-pole: sin2Won-shell = 0.2227  0.00037 (3  away)
To explain NuTeV anomaly
• nuclear shadowing
Miller and Thomas (2002), Zeller et. Al. (2002), Kovalenkov, schmidt and Yang (2002)
• asymmetry in strange sea distribution
Davidson, Forte, Gambino, Rius and Strumia (2002), Goncharov et. al. (2001)
• isospin symmetry breaking
Bodek et. al. (1999), Zeller et. Al. (2002)
• QCD corrections
…
Dobrescu and Ellis (2003), Kretzer et. al. (2003), Davidson et. al. (2002)
S. Su
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New physics explanation
Difficult !
● Supersymmetry:  Rn, -n  0
Kurylov, Ramsey-Musolf, Su (2003), Davidson, Forte, Gambino, Rius and Strumia (2002)
● Extra Z’ : family non-universal, finetuning
Langacker and Plumacher (2000)
● Leptoquark: tune mass splitting
Davidson, Forte, Gambino, Rius and Strumia (2002)
● n mixing with extra heavy neutrino:
constraints from other observables
Babu and Pati (2002), Loinaz et. al. (2003)
MSSM
S. Su
RPV
27
Conclusion
● precision measurements of sin2W at low energy
- PV ee, ep scattering (E158, Jlab Moller, Qweak)
- eD DIS-parity
- APV measurements
- NuTeV
● consistency check of SM
● sensitive to new physics
complementary to direct searches
● combinations of several exp
 distinguish various new physics
● uncertainties caused by QCD
- extract from experimental measurements
- SM predictions
S. Su
28
Talks in this workshop
Talk in parity violation
● K. Paschke: DIS-parity
● D. Mack: Moller Parity
S. Su
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