Symmetries in Nuclear Physics Krishna Kumar University of Massachusetts Editorial Board: Parity Violation: K.
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Symmetries in Nuclear Physics
Krishna Kumar
University of Massachusetts
Editorial Board: Parity Violation: K. K, D. Mack, M. Ramsey-Musolf, P. Reimer, P. Souder Low Energy QCD: B. Bernstein, A. Gasparian, J. Goity
Jlab 12 GeV PAC Meeting, January 10, 2005
10 January, 2005
Symmetries in Nuclear Physics
Symmetry Tests at 12 GeV
• •
Strong Interaction
– Chiral symmetry breaking – Axial Anomaly – Charge symmetry violation – Spin-Flavor symmetry breaking
Electroweak Interaction
– TeV scale physics 10 January, 2005
Symmetries in Nuclear Physics
Outline
• • •
Primakoff Production of Pseudoscalar Mesons
– 2
decay widths of
and
’
– Transition Form Factors at low Q
2
Parity-Violating M øller Scattering
– Ultimate Precision at Q
2 <
Parity-Violating Deep Inelastic Scattering
– New Physics at 10 TeV in Semileptonic Sector – Charge Symmetry Violation – d/u at High x – Higher Twist Effects 10 January, 2005
Symmetries in Nuclear Physics
Lightest Pseudoscalar Mesons
• • •
Spontaneous breaking of Chiral SU L (3)xSU R (3) Goldstone bosons Chiral anomalies - Mass of - 2
0 decay widths Flavor SU(3) breaking π 0 ,
,
’ mixing Test fundamental QCD symmetries via the
10 January, 2005
Primakoff Effect
Symmetries in Nuclear Physics
Setup with Energy Upgrade
• • •
Larger X-Section Lighter Nuclei: 1 H and 4 He Better background separation
•New high energy photon tagger •Improved PbWO
4 calorimeter
10 January, 2005
Symmetries in Nuclear Physics
From 2
to 3π to Quark Mass Ratio
Leutwyler Q
2
m s
2
m d
2
m m u
2 2 , where ˆ 1 2 (
m u
m d
) 10 January, 2005
Symmetries in Nuclear Physics
Major Physics Impact
•
Determination of quark mass ratio
•
The nature of the
’: Goldstone boson?
•
Interaction Radii of π 0 ,
,
•
Chiral anomaly predictions ’
•
Number of colors N c
•
Tests of QCD models
•
Tests of future lattice calculations
•
Input to light-by-light amplitude for (g-2)
10 January, 2005
Symmetries in Nuclear Physics
PV Asymmetries
10 5
Q
2 to 10 4
(g A e g V T +
Q
2
g V e g A T )
For electrons scattering off nuclei or nucleons:
Z couplings provide access to different linear combination of underlying quark substructure
10 January, 2005
Symmetries in Nuclear Physics
• • •
Parity Violation at Jlab
Electron Beam Quality
– Simple laser transport system; pioneers in PV experiments with
high polarization cathodes (HAPPEX-I)
– CW beam alleviates many higher order effects; especially in
energy fluctuations
– HAPPEX-II preliminary result: A
raw correction ~ 60 ppb
High Luminosity
– High beam current AND high polarization – Dense cryogenic targets with small density fluctuations
Progression of Precision Experiments
– Facilitates steady improvements in technology – Strong collaboration between accelerator and physics divisions
(A PV )
1 part per billion
10 January, 2005
Symmetries in Nuclear Physics
(A PV )/A PV
1%
(it just wont break!)
The Annoying Standard Model
Nuclear Physics Long Range Plan: What is the new standard model?
Low Q 2 offers unique and complementary probes of new physics
•Rare or Forbidden Processes •Symmetry Violations •Electroweak One-Loop Effects
- Double beta decay..
- neutrinos, EDMs..
- Muon g-2, beta decay..
•
Precise predictions at level of 0.1%
•
Indirect access to TeV scale physics
Low energy experiments are again relevant in the neutral current sector
10 January, 2005
Symmetries in Nuclear Physics
World Electroweak Data
16 precision electroweak measurements:
2 /dof ~ 25.4/15
Probability < 5% Leptonic and hadronic Z couplings seem inconsistent Perhaps the Standard Model is already broken Perhaps there are bigger effects elsewhere
10 January, 2005
Symmetries in Nuclear Physics
Electroweak Physics at Low Q
2 Q 2 << scale of EW symmetry breaking
Logical to push to higher energies, away from the Z resonance LEPII, Tevatron, LHC access scales greater than
L
~ 10 TeV Q 2 <
10 January, 2005
Symmetries in Nuclear Physics
Fixed Target Møller Scattering
Purely leptonic reaction
Q W e
~
1
-
4
sin
2
W
A PV
m e E lab
(1 4 sin 2
W
) 1
E lab
(sin sin 2 2
W
W
) 0.05
(
A PV A PV
)
Figure of Merit rises linearly with E lab SLAC E158 Jlab at 12 GeV
Highest possible E lab with good P 2 I Moderate E lab o in COM (E’=E lab /2) with LARGE P 2 I
Unprecedented opportunity: The best precision at Q 2 <
10 January, 2005
Symmetries in Nuclear Physics
Design for 12 GeV
E’: 3-6 GeV
lab = 0.53
o -0.92
o A PV = 40 ppb
I beam = 100 µA 150 cm LH 2 target 4000 hours Toroidal spectrometer ring focus
(A PV )=0.58 ppb
• • • • •
Beam systematics: steady progress (E158 Run III: 3 ppb) Focus alleviates backgrounds: ep
ep(
), ep
eX(
) Radiation-hard integrating detector Normalization requirements similar to other planned experiments Cryogenics, density fluctuations and electronics will push the state of-the-art
10 January, 2005
Symmetries in Nuclear Physics
New Physics Reach
Jlab Møller
L
ee ~ 25 TeV
New Contact Interactions
LEP200 L ee ~ 15 TeV •
SUSY provides a dark matter candidate if baryon (B) and lepton (L) numbers are conserved
•
However, B and L need not be conserved in SUSY, leading to neutralino decay (RPV) LHC
Complementary; 1-2 TeV reach
Kurylov, Ramsey-Musolf, Su
Q e W and Q p W would have new contributions from RPV
10 January, 2005
Symmetries in Nuclear Physics
Electroweak Physics
Q W e modified
Marciano and Czarnecki
sin 2
W runs with Q 2
•
Semileptonic processes have
•
significant uncertainties E158 established running,
•
probing vector boson loops Jlab measurement would probe scalar loops
(sin 2
W ) ~ 0.0003
10 January, 2005
Symmetries in Nuclear Physics
e -
N
Parity Violating Electron DIS
Z *
*
e -
X
A PV a
(
x
)
G F Q
2 2
C
1
i Q i f i
(
x
)
Q i
2
f i
(
x
)
a
(
x
)
b
(
x
)
f
(
y
)
b
(
x
)
C
2
i Q i Q i
2
f i
(
x
)
f i
(
x
)
C
1
i C
2
i
2
g A e
2
g V e g V i g A i
a
(
x
) 1.15
f i
For an isoscalar target like
a
(
x
) 3 10 (2
C
1
u
C
1
d
) 4 15
2
s
(
x
)
u
(
x
)
d
(
x
)
b
(
x
) 3 10 (2
C
2
u
C
2
d
)
q
(
x
)
q
(
x
)
u
(
x
)
d
(
x
)
+ small corrections
b(x) is a factor of 5 to 10 smaller
Elastic scattering measures C 1i , but C 2i are less well-known
12 GeV: 1% measurements feasible Moderate x, high Q 2 , W 2 TeV scale physics
10 January, 2005
Symmetries in Nuclear Physics
2
H PV DIS at 11 GeV
E’: 6.8 GeV ± 10%
I beam = 90 µA
lab = 12.5
o
60 cm LD 2 target
A PV = 290 ppm
400 hours 1 MHz DIS rate, π/e ~ 1 HMS+SHMS or MAD
x Bj Q 2 W 2 ~ 0.45
~ 3.5 GeV 2 ~ 5.23 GeV 2
(A PV )=1.5 ppm
• •
Systematic limit: Beam polarization Beam systematics easily controlled
• •
moderate running time
•
Best constraint on 2C 2u -C 2d
•
Similar sensitivity to NuTeV Theoretical interpretability issues: Important in themselves!
PV DIS can address these issues
Symmetries in Nuclear Physics
10 January, 2005
Charge Symmetry Violation (CSV)
Charge symmetry: assume
u
(
x
)
u p
(
x
)
d n
(
x
)
d
(
x
)
d p
(
x
)
u n
(
x
)
are negligible
Small effects are possible from:
•u-d mass difference •electromagnetic effects
Search for unambiguous signal of CSV at the partonic level
For PV DIS off 2 H:
A PV A PV
0.28
u u
d d
No theoretical issues at high Q 2 , W 2 10% effect possible if u+d falls off more rapidly than
u-
d at x ~ 0.7
From pdf fits: 1/3 of NuTeV discrepancy from CSV
Londergan & Thomas
Strategy for PV DIS:
•
measure or constrain higher twist effects at x ~ 0.5-0.6
•
precision measurement of A PV at x ~ 0.7 to search for CSV
10 January, 2005
Symmetries in Nuclear Physics
Higher Twist Effects
Brodsky
• • • •
A PV sensitive to diquarks: ratio of weak to electromagnetic charge depends on amount of coherence If Spin 0 diquarks dominate, likely only 1/Q 4 effects.
Novel interference terms might contribute Other higher twist effects may cancel, so A PV dependence on Q 2 . may have little
10 January, 2005
Symmetries in Nuclear Physics
• • • •
d/u at High x
SU(6) breaking (scalar diquark dominance), expect d/u ~ 0 Perturbative QCD prediction for x ~ 1: d/u ~ 0.2
No consensus on existing deuteron structure function data Proposed methods have nuclear corrections
a
(
x
)
A PV
A
PV
in DIS on
G F Q
2 2
a
(
x
)
f
1 H
(
y
)
b
(
x
)
u
(
x
)
u
(
x
) 0.91
d
(
x
) 0.25
d
(
x
)
+ small corrections
d/u measurement on a single proton!
No nuclear corrections!
•
Must control higher twist effects
•
Verify Standard Model at low x
•
Must obtain ~ 1% stat. errors at x ~ 0.7
10 January, 2005
Symmetries in Nuclear Physics
• • • • • •
PV DIS Program
Hydrogen and Deuterium targets 1 to 2% errors
– It is unlikely that any effects are larger
than 10%
x-range 0.3-0.7
W 2 well over 4 GeV 2 Q 2 range a factor of 2 for each x point
– (Except x~0.7)
Moderate running times TeV physics, higher twist probe, CSV probe, precision d/u…
• •
The Standard Model test can be done with proposed Hall upgrade equipment A dedicated spectrometer/detector package is needed for rest of program
10 January, 2005
Symmetries in Nuclear Physics
A Concept for PV DIS Studies
•
CW 100 µA at 11 GeV
•
Magnetic spectrometer would be too expensive
•
20 to 40 cm LH 2 and LD 2
•
Luminosity > 10 38 /cm 2 /s targets
•
Calorimeter to identify electron clusters and reject
•
hadrons a la A4 at Mainz Toroidal sweeping field to reduce neutrals, low energy
•
Mollers and pions Cherenkov detectors for pion rejection might be needed
• •
solid angle > 200 msr
•
Count at 100 kHz pion rejection of 10 2 to 10 3
10 January, 2005
Symmetries in Nuclear Physics
• • • • • •
High x Physics Outlook
Parity-Violating DIS can probe exciting new physics at high x One can start now (at 6 GeV)
– Do 2 low Q
2 points (P-05-007, X. Zheng contact)
•
Q 2 ~ 1.1 and 1.9 GeV 2
• •
Either bound or set the scale of higher twist effects
– Take data for W<2 (P-05-005, P. Bosted contact)
Duality
•
Could help extend range at 11 GeV to higher x A short run to probe TeV physics in PV DIS off 2 H: Hall A or C The bulk of the program requires a dedicated spectrometer/detector CSV can also be probed via electroproduction of pions
– 6 GeV beam can probe x ~ 0.45 (P-05-006, K. Hafidi contact) – Should be able to go to higher x with 12 GeV beam
Other physics topics could be addressed:
– Transverse (beam-normal) asymmetries in DIS – Polarized targets: g
2 and g 3 structure functions
– Higher twist studies of A
1 p and A 1 n
10 January, 2005
Symmetries in Nuclear Physics
Summary
• • • • •
New window to symmetry tests opened by 12 GeV upgrade Precision measurements of pseudoscalar meson properties: tests of low energy QCD and extraction of fundamental parameters A PV in Møller scattering has unique sensitivity to leptonic contact interactions to 25 TeV A PV in DIS off 2 H at x ~ 0.45 would probe for TeV physics in axial-vector quark couplings An exciting array of important topics in high x physics can be addressed by a new, dedicated spectrometer/detector concept
10 January, 2005
Symmetries in Nuclear Physics