Electroweak Physics at an Electron-Ion ColliderM.J. Ramsey-MusolfWisconsin-MadisonQuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.
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http://www.physics.wisc.edu/groups/particle-theory/
NPACTheoretical Nuclear, Particle, Astrophysics & Cosmology
ECT* Trento, July 2008
Outline
• Brief Context: Precision and Energy Frontiers
• Neutral Current Processes: PV DIS & PV Moller
• Charged Current Processes: e-+A K ET + j
• Lepton flavor violation: e-+A K - + A
Disclaimer: some ideas worked out in detail; others need more research
Low-Energy: What we have learned
• Weak interactions violate P
• QCD is tiny
• QWP ~ 0.1 QW
n ~ -1
• S-quarks: impt for spin, not for N
• Sin2W runs
• TeV scale technicolor unlikely
• Nuclei have large anapole moments
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What we would like to know
• Does the “new SM” violate CP? Can it explain the abundance of matter?
• Are there new TeV scale interactions? If so, what are their symmetries?
• How does QCD make a proton?
• Are lepton number and charged lepton flavor conserved ?
Precision Probes of New Symmetries
Beyond the SM SM symmetry (broken)
Electroweak symmetry breaking: Higgs ?
New Symmetries
1. Origin of Matter2. Unification & gravity
3. Weak scale stability4. Neutrinos
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e−
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?
LHC: energy frontier
Low-energy: precision frontier
EIC: Post LHC Era
Precision & Energy Frontiers
Radiative corrections
Direct Measurements
Stunning SM Success
J. Ellison, UCI
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GFZ
GFμ
≈ 1+ ΔrZ − Δrμ( )
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t
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t
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b
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• Precision measurements predicted a range for mt
before top quark discovery
• mt >> mb !
• mt is consistent with that range
• It didn’t have to be that way
Probing Fundamental Symmetries beyond the SM:
Use precision low-energy measurements to probe virtual effects of new symmetries & compare with collider results
Precision Frontier:
• Precision ~ Mass scale
• Look for pattern from a variety of measurements
• Identify complementarity with collider searches
• Special role: SM suppressed processes
Nuclei & Charged Leptons
PV Electron ScatteringQuickTime™ and a
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Weak DecaysQuickTime™ and a
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• nuclear decay
• pion decays
• muon decays
• Q-Weak • 12 GeV Moller• PV DIS
Muons
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• g-2
• A->eA
EIC:• More PV• New CC ?• LFV ?
Neutral Current Probes: PV
• Basics of PV electron scattering
• Standard Model: What we know
• New physics ? SUSY as illustration
• Probing QCD
PV Electron Scattering
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e−, p
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γ
Parity-Violating electron scattering
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APV =N↑↑ − N↑↓
N↑↑ + N↑↓
=GFQ2
4 2παQW + F(Q2,θ)[ ]
“Weak Charge” ~ 0.1 in SM
Enhanced transparency to new physics
Small QCD uncertainties (Marciano & Sirlin; Erler & R-M)
QCD effects (s-quarks): measured (MIT-Bates, Mainz, JLab)
Nuclei & Charged Leptons: Theory
PV Electron ScatteringQuickTime™ and a
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• Q-Weak • 12 GeV Moller• PV DIS
Muons
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• g-2
• A->eA
Essential Role for Theory
• Precise SM predictions (QCD)
• Sensitivity to new physics & complementarity w/ LHC
• Substantially reduced QCD uncertainty in sin2W running
• QCD uncertainties in ep box graphs quantified
• Comprehensive analysis of new physics effects
e p e p e p
W
W
Z
Z
Z
γ
Weak DecaysQuickTime™ and a
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• n decay correlations
• nuclear decay
• pion decays
• muon decays
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Effective PV e-q interaction & QW
Low energy effective PV eq interaction
Weak Charge:
Nu C1u + Nd C1d
Proton:
QWP = 2 C1u + C1d = 1-4 sin2W ~ 0.1
Electron:
QWe = C1e = -1+4 sin2W ~ - 0.1
QW and Radiative Corrections
Tree Level
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QWf = gV
f gAe
Radiative Corrections
QWf =ρPV (2I3
f −4QfκPV )+λ fsin2 θW
Flavor-independent
Normalization Scale-dependent effective weak mixing
Flavor-dependent
Constrained by Z-pole precision observables
Large logs in
Sum to all orders with running sin2W & RGE
Weak Charge & Weak Mixing
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sin2 θW =g(μ)Y
2
g(μ)2 + g(μ)Y2
SU(2)LU(1)Y
Weak mixing depends on scale
Weak Mixing in the Standard Model
Scale-dependence of Weak Mixing
SLAC Moller
Parity-violating electron scattering
Z0 pole tension
Z Pole Tension
⇒ mH = 89 +38-28
GeV⇒ S = -0.13 ± 0.10
ALR AFB (Z→ bb)
sin2θw = 0.2310(3)
↓mH = 35 +26
-17 GeVS= -0.11 ± 17
sin2θw = 0.2322(3)
↓mH = 480 +350
-230
GeVS= +0.55 ± 17
Rules out the SM! Rules out SUSY!Favors Technicolor!
Rules out Technicolor!Favors SUSY!
(also APV in Cs) (also Moller @ E158)
W. MarcianoThe Average: sin2θw = 0.23122(17)
3σ apart
•Precision sin2W measurements at colliders very challenging•Neutrino scattering cannot compete statistically•No resolution of this issue in next decade
K. Kumar
Weak Mixing in the Standard Model
Scale-dependence of Weak Mixing
JLab Future
SLAC Moller
Parity-violating electron scattering
Z0 pole tension
Effective PV e-q interaction & PVDIS
Low energy effective PV eq interaction
PV DIS eD asymmetry: leading twistWeak Charge:
Nu C1u + Nd C1d
Proton:
QWP = 2 C1u + C1d = 1-4 sin2W ~ 0.1
Electron:
QWe = C1e = -1+4 sin2W ~ - 0.1
C2q and Radiative Corrections
Tree Level
Radiative CorrectionsFlavor-dependent
Flavor-independent
Normalization Scale-dependent effective weak mixing
Constrained by Z-pole precision observables
Like QWp,e ~ 1 - 4 sin2W
New Physics: Comparing PV Observables
QWP = 0.0716 QW
e = 0.0449
Experiment
SUSY Loops
E6 Z/ boson
RPV SUSY
Leptoquarks
SM SM
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±0.0029
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±0.0040
SUSY Radiative Corrections
Propagator
Box
Vertex & External leg
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˜ χ Kurylov, RM, Su
SUSY: R Parity-Violation
μ−
ν e e−
νμ
˜ e Rk
12k 12k
e−
d e−
d
˜ q Lj
1j1
1j1
L=1 L=1
Δ12k =λ12k
2
4 2GF M˜ e Rk
2 Δ1j1/ =
λiji/ 2
4 2GFM˜ q Lj
2
• No SUSY DM: LSP unstable
• Neutrinos are Majorana
PVES & APV Probes of SUSY
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Q
WP
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US
Y /
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P,
SM
RPV: No SUSY DM Majorana ν s
SUSY Loops
QWe, SUSY / QW
e, SM
g-2
12 GeV
6 GeV
E158
Q-Weak (ep)
Moller (ee)
Kurylov, RM, Su
Hyrodgen APV or isotope ratios
Global fit: MW, APV, CKM, l2,…
Deep Inelastic PV: Beyond the Parton Model & SM
e-
N X
e-
Z* γ*
d(x)/u(x): large x Electroweak test: e-q couplings & sin2W
Higher Twist: qq and qqg correlations
Charge sym in pdfs
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up (x) = dn (x)?
d p (x) = un (x)?
PVDIS & QCD
Low energy effective PV eq interaction
PV DIS eD asymmetry: leading twist
Higher Twist (J Lab)
CSV (J Lab, EIC)
d/u (J Lab, EIC) +
PVDIS & CSV
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up (x) = dn (x)?
d p (x) = un (x)?
•Direct observation of parton-level CSV would be very exciting!•Important implications for high energy collider pdfs•Could explain significant portion of the NuTeV anomaly
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u(x) = up (x) − dn (x)
δd(x) = d p (x) − un (x)
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RCSV =δAPV (x)
APV (x)= 0.28
δu(x) −δd(x)
u(x) + d(x)
Londergan & Murdock
Few percent A/A
Adapted from K. Kumar
PVDIS & d(x)/u(x): xK1
Adapted from K. Kumar
SU(6): d/u~1/2Valence Quark: d/u~0
Perturbative QCD: d/u~1/5
PV-DIS off the proton(hydrogen target)
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APV =GFQ2
2παa(x) + f (y)b(x)[ ]
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a(x) =u(x) + 0.91d(x)
u(x) + 0.25d(x)
Very sensitive to d(x)/u(x)
A/A ~ 0.01
PVES at an EIC
Scale-dependence of Weak Mixing
JLab Future
SLAC Moller
Parity-violating electron scattering
EIC PVDIS ?
Z0 pole tension
EIC Moller ?
Charged Current Processes
• The NuTeV Puzzle
• HERA Studies
• W Production at an EIC ? CC/NC ratios ?
Weak Mixing in the Standard Model
Scale-dependence of Weak Mixing
JLab Future
SLAC Moller
νnucleus deep inelasticscattering
Z0 pole tension
The NuTeV Puzzle
Rν =σνNNC σνN
CC =gL2 +rgR
2
Rν =σν NNC σ ν N
CC =gL2 +r−1gR
2
gL,R2 =
ρνNNC
ρνNCC
⎛
⎝ ⎜ ⎞
⎠ ⎟
2
(εL ,Rq
q∑ )2
r =σνNCC σν N
CC
Rνexp−Rν
SM =−0.0033±0.0007
Rν exp−Rν
SM =−0.0019±0.0016
R− =
Rν −rRν
1−r=(1−2sin2θW) /2+L
Paschos-Wolfenstein
SUSY Loops
RPV SUSY
Wrong sign
Other New CC Physics?
Low-Energy Probes
Nuclear & neutron decay
Pion leptonic decay
Polarized -decay
O / OSM ~ 10-3
O / OSM ~ 10-4
O / OSM ~ 10-2
HERA W production
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O / OSM ~ 10-1
A. Schoning (H1, Zeus)
Lepton Number & Flavor Violation
• LNV & Neutrino Mass
• ν Mechanism Problem
• LFV as a Probe
• K e Conversion at EIC ?
ν-Decay: LNV? Mass Term?
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νM
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A Z,N( )
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Effective
( )Mass meV
12 3 4 5 6 7
12 3 4 5 6 7
12 3 4 5 6 7
1 ( )Minimum Neutrino Mass meV
U1e = .866 m2
sol = 7 meV
2
U2e = .5 m2
atm = 2 meV
2
U 3e =
Inverted
Normal
Degenerate
Dirac Majorana
-decayLong baseline
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?
Theory Challenge: matrix elements+ mechanism
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mνEFF & neutrino spectrum
Normal Inverted
ν-Decay: LNV? Mass Term?
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A Z,N( )
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12 3 4 5 6 7
12 3 4 5 6 7
12 3 4 5 6 7
1 ( )Minimum Neutrino Mass meV
U1e = .866 m2
sol = 7 meV
2
U2e = .5 m2
atm = 2 meV
2
U 3e =
Inverted
Normal
Degenerate
Dirac Majorana
-decayLong baseline
?
?
Theory Challenge: matrix elements+ mechanism
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2mk e2iδ
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νM
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d
mνEFF & neutrino spectrum
Normal Inverted
See-saw mechanism
Leptogenesis
νL νLνR
H H
Lepton Asym ! Baryon Asym
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GERDA CUORE
EXO Majorana
ν-Decay: Mechanism
Dirac Majorana
Theory Challenge: matrix elements+ mechanism
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Mechanism: does light νM exchange dominate ?
How to calc effects reliably ? How to disentangle H & L ?
O(1) for ~ TeV Does operator power counting suffice?
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Prezeau, R-M, Vogel: EFT
ν-Decay: Interpretation
0.1
1
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Effective
( )Mass meV
12 3 4 5 6 7
12 3 4 5 6 7
12 3 4 5 6 7
1 ( )Minimum Neutrino Mass meV
U1e = .866 m2
sol = 7 meV
2
U2e = .5 m2
atm = 2 meV
2
U 3e =
Inverted
Normal
Degenerateν signal equivalent to degenerate hierarchy
Loop contribution to mν of inverted hierarchy scale
Lepton Flavor & Number Violation
Present universe Early universe
Weak scale Planck scale
log10(μ / μ0)
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αY−1
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A Z,N( )
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MEG: γ ~ 5 x 10-14
2e: B ->e ~ 5 x 10-17
??
R = B->e
B->eγ
Also PRIME
Lepton Flavor & Number Violation
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MEG: B->eγ ~ 5 x 10-14
2e: B->e ~ 5 x 10-17
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Logarithmic enhancements of R
Low scale LFV: R ~ O(1) GUT scale LFV: R ~ Oα
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νM
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0ν decay
Light νM exchange ?
Heavy particle exchange ?
Raidal, Santamaria; Cirigliano, Kurylov, R-M, Vogel
k11/ ~ 0.09 for mSUSY ~ 1 TeV
->eγ LFV Probes of RPV:
k11/ ~ 0.008 for mSUSY ~ 1 TeV
->e LFV Probes of RPV:
mν “naturalness”:
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Lepton Flavor & Number Violation
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Exp: B->eγ ~ 1.1 x 10-7
EIC: ~ 103 | A1e|2 fb
Raidal, Santamaria; Cirigliano, Kurylov, R-M, Vogel
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Logarithmic enhancements of R
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|A2e|2 < 10-8
EIC: ~ 10-5 fb
If |A1e|2 ~ |A2
e|2
Log enhancement:
|A1e|2 / |A2
e|2 ~ | ln me / 1 TeV |2 ~ 100
BKeγ 48 3 α |A2e|2
Need ~ 1000 fb
LFV with leptons: HERA
Veelken (H1, Zeus) (2007)
Leptoquark Exchange
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qq eff op
lq|2 < 10-4 (MLQ / 100 GeV)2
Induce Keγ at one loop?
LFV with leptons: recent theory
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Kanemura et al (2005)
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qq eff opSUSY Higgs Exchange
lq|2 < 2 x 10-2 (MLQ / 100 GeV)2
lq|2 < 10-4 (MLQ / 100 GeV)2 HERA
Summary
• Precision studies and symmetry tests are poised to discovery key ingredients of the new Standard Model during the next decade
• There may be a role for an EIC in the post-LHC era
• Promising: PV Moller & PV DIS for neutral currents
• Homework: Charged Current probes -- can they complement LHC & low-energy studies?
• Intriguing: LFV with eK conversion:
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L dt ~ 103 fb∫
Thank you !
• Precision studies and symmetry tests with neutrons are poised to discovery key ingredients of the new Standard Model during the next decade
• Physics “reach” complements and can even exceed that of colliders: dn~10-28 e-cm ; O/OSM ~ 10-4
• Substantial experimental and theoretical progress has set the foundation for this era of discovery
• The precision frontier is richly interdisciplinary: nuclear, particle, hadronic, atomic, cosmology
To the organizers, ECT* staff, and participants for a lively and stimulating workshop
Back Matter
• Precision studies and symmetry tests with neutrons are poised to discovery key ingredients of the new Standard Model during the next decade
• Physics “reach” complements and can even exceed that of colliders: dn~10-28 e-cm ; O/OSM ~ 10-4
• Substantial experimental and theoretical progress has set the foundation for this era of discovery
• The precision frontier is richly interdisciplinary: nuclear, particle, hadronic, atomic, cosmology