Transcript neutral current overview

Probing New Physics with
Neutral Current Measurements
Shufang Su • U. of Arizona
Outline
• Precision measurements vs. direct detection
• Neutral current measurements
– parity violating electron scattering
ee Moller scattering (SLAC E158)
ep elastic scattering (Jlab Qweak)
– atomic parity violation (APV)
– neutrino-nucleus deep inelastic scattering (NuTeV)
- proble new physics beyond SM
- some QCD issue
- future experiments
• Conclusion
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Precision measurements vs. direct detection
(indirect)
Direct vs. indirect detection
(direct)
● provide complementary
information
mt=178.0  4.3 GeV
● success of SM
● consistency check of any
new physics scenario
LEP EWWG
LEP EWWG 2004 winter
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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
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Neutral Current: Test of sin2W running
Weak mixing angle sin2W
courtesy of Erler and Carlini
E158 Runs I+II
(Preliminary)
NuTeV
MS
Weak mixing angle sinW
g sinW = g’ cosW = e
● sin2W(0) - sin2W(mZ2) =
+0.007
-2
Cs neutral current
Talk in
session
– QW : agree Q =0
-
– NuTeV:
+3 Q2=20 (GeV)2
●
Norval Fortson:APV
APV(Cs)
● Bob McKeown: ee (E158)
• parity-violating electron
● Shelley Page: ep (Qweak)
scattering (PVES) Q2=0.03 (GeV)2
ee
E158
ep
Qweak
Anticipated final errors
scale Q (GeV)
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● Kevin McFarland: (NuTeV)
- ee Moller scattering (SLAC) QWe
Inelastic
addition
- ep
scattering (J-lab) QWp
● Janet Conrad (Friday):
 sin2W - 0.0007
reactor based -e- scattering
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NC exp as a indirect probe of new physics
SM is a low energy approximation of a more fundamental theory
NC exp:  consistency check of SM
 complementary to direct new physics searches
 distinguish various new physics
● 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 …
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PVES:E158 and Qweak
A
ALR
V
N+-NN++N-
 QWf
geA = Ie3
weak charge QWf = 2gfV = 2 If3 -4Qfs2
ep Qweak exp QWp
ee Moller exp QWe
QWe,p tree
1-4s2
-(1-4s2)
QWe,p loop
0.0721
-0.0449
exp precision 4%
9%
2
 sin
0.0007
0.0010
W
clean environment:
Hydrogen target
SM running
10  clean: small hadronic
8  uncertainties
 theoretically
Cs :
tree
level
2 =
 0.0021
0.1  sensitive
to new
QW
 sin
NuTeV:
sin2physics
W = 0.0016
W
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Sensitivity to new physics scale
Ramsey-Musolf(1999)
: new physics scale
Take  QWp=4%
O(1)
courtesy of Carlini
- Non-perturbative theory g » 2   » 29 TeV
- Extra Z’ (GUT) g » 0.45 mZ’ » 2.1 TeV
● probe new physics scale comparable to LHC
● confirmation of LHC discovery (couplings, charges)
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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%
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R-parity violating (RPV)
• RPV operators contribute to QWe,p at tree level
Kurylov, Ramsey-Musolf, Su (2003)
Exp constraints
Qp
W
•
•
•
•
 decay:RPV
|Vud| = -0.00145 MSSM
 0.0007
CLCs = -0.0040 loop
APV(Cs):95%
 QW
0.0066
Re/ :
 Re/ = -0.0042  0.0033
G :
 G = 0.00025  0.00188
No SUSY dark
matter
G
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I) Obtain 95% CL allowed region
in RPV coefficients
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
 0.0040
• MSSM:
Distinguish
via APV QWCs
• extra Z’:
• RPV SUSY
• leptoquark
SM
SM
Combinations of NC exps could be used to distinguish various new physics
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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 %
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QCD correction to ep scattering
Box diagram contribution to QWP
e
p
e
p
e
Z
W
suppression

p
26%
 QWP
W
kloop
e »n O(mW)
p
Z
Z
e


Z
p
3%
kloop » O(mZ)
|CW|  2using (CKM
unitarity)
OPE (pQCD)
|CZ|  2
-0.08%
 QWP (QCD) -0.7%
e
p
e
non-calculable
Similar to nuclear -decay
ep 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%
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Outlook: PV electron scattering
Kurylov, Ramsey-Musolf, Su (2003)
Erler
MSSM
NuTeV
RPV
sin2W
Linear Collider e-eDIS-Parity,JLab
DIS-Parity, SLAC
APV
SLAC E158
(ee)
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JLab Moller
(ee)
e+e- LEP, SLD
JLab QWeak
(ep)
Q (GeV)
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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)
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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

QWd
<0

 QW(Z,N) / QW(Z,N) < 0.2 % for Cs
 QWp
• exp
 0.0029
 QWe
 QWCs
 0.0040
• MSSM:
small
• extra Z’:
sizable
SM
SM
Erler, Kurylov and Ramsey-Musolf (2003)
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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
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NuTeV experiment
NC
CC
gL,R2=(uL,R)2+(dL,R)2
R=-0.0033
 0.0015
-
R=-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
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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)
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New physics explanation
Difficult !
● Supersymmetry:  R, -  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)
●  mixing with extra heavy neutrino:
constraints from other observables
Babu and Pati (2002), Loinaz et. al. (2003)
reactor based MSSM
-e- scattering  sin2W
RPV
Conrad, Link and Shaevitz (2004)
(Janet Conrad, Friday)
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Conclusion
● NC exp: precision measurements of sin2W at low energy
- PV ee, ep scattering (E158, Qweak)
- APV measurements
- NuTeV
● consistency check of SM
● sensitive to new physics
complementary to direct searches
● combinations of several NC exp
 distinguish various new physics
● uncertainties caused by QCD
- extract from experimental measurements
- SM predictions
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Talks in this workshop
Talk in neutral current session
● Norval Fortson:APV
● Bob McKeown: ee (E158)
● Shelley Page: ep (Qweak)
● Kevin McFarland: (NuTeV)
In addition
● Janet Conrad (Friday):
- - scattering
reactor based -e
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