Parity Violating Electron Scattering in Resonance region (Res-Parity)
Parity-violating NN interaction from different approaches
description
Transcript of Parity-violating NN interaction from different approaches
Parity-violating Parity-violating NNNN interaction interaction from different approachesfrom different approaches
Chang Ho Hyun with
B. Desplanques Universite Joseph Fourier
S. Ando Manchester
C.-P. Liu Wisconsin-Madison
13 November, 2007
Contents
Effective field theory
Covariant formalism
Summary
• Effective field theory (EFT) in nuclear physics : Successful in describing various strong and electromagnetic few body (2N, 3N, …) processes at low energies.
• Advantage of EFT Perturbative expansion scheme : We can (roughly) estimate the amo
unt of terms (diagrams) not considered. Low energy constants (LECs) : Make the prediction model-independe
nt without the knowledge of short range dynamics.
-> A natural extension of EFT to other realm of interaction :
Parity-violating (PV) interaction from order by order expansion of EFT!
Effective Field Theory
• The first derivation PV two-nucleon (2N) potential from EFT :S.-L. Zhu, C.M. Maekawa, B.R. Holstein, M.J. Ramsey-Musolf, U. van Kolck, NPA748, 435 (2005). Leading order (LO ; Q-1) : one-pion-exchange (OPE) Next-to-next-to leading order (NNLO ; Q1) : two-pion-exchange (TPE) + 4N contact term (CT)
• Re-derivation of the PV potential up to NNLO :
CHH, SA and BD, PLB652, 257 (2007),
and
• Application to physical processes :
CHH, SA and BD, PLB652, 257 (2007),
CPL, PRC75, 065501 (2007).
CHH, SA, BD, PLB651, 257 (2007)
• Observable : PV asymmetry (A) in n p -> d
• Last measurement : (1.5 +- 4.8)x10-8 (Cavainag et al. Can. J. Phys. ’88)
• On-going experiment at SNS aims at unambiguous measurement of A at 10-8 order.
• Strong interaction : Av18• Weak interaction : Heavy baryon chiral perturbation theory
LO NNLO
OPE ~ Q-1 TPE ~ Q1 CT ~ Q1
We introduce form factor and cutoff : monopole form factor.
Maximal (MX) subtraction
Minimal (MN) subtraction
Determination of : Usually in terms of
experiment, but no available data yet in PV observables.-> Assume heavy meson limit :
dependent
~-3
A
A = ai 1
ai
I. Strong interaction phenomenology : Av18
II. EM operator : E1 ∝ (Siegert theorem)
III. Weak potential : LO, NNLO
r
Each contribution
Make OPE contribution
independent ->
Net value
A
1. Contribution of LEC with heavy meson limit amounts to about 30% of that of TPE.
2. Maximum scheme dependence amounts to 25%.
3. Renormalization point dependence gives about 15% uncertainty.
Uncertainty due to short and intermediate range behavior of TPE
and CT potentials.
• No unknown parameter (no LEC)
• Well defined at short range (form factor and cutoff not necessary)
• Can give hints to the magnitude of LECs and their contributions to observables
• Can be a guideline to the behavior of TPE potential in the intermediate range
Covariant Formalism
’• BD, PLB41, 461 (1972)• H.J. Pirner and D.O. Riska, PLB44, 151 (1973)• M. Chemtob and BD, NPA78, 139 (1974)
One-pion iteration subtracted
Relevant to np -> d
Relevant to pp scattering
Higher order in 1/M -> Neglect them
Take large nucleon mass (LM) limit from COV
A2 discrepancy can be accounted by missing
contribution in COV calculation.
-> EFT is equivalent to leading 1/ term in COV.
(~1/3)
(~1/4)
Short-intermediate
Long
1. Long range : COV and LM converges.2. Short range• COV : converges to a finite value,• LM : diverges proportional to - with > 2.-> No need for form factor for COV. -> COV result will be free from cutoff uncertainty.
2 ()
Weak pot.
OPE TPE-COV TPE-LM TPE+CT(EFT)
a -0.112 0.004 0.014 0.010~0.019
- OPE dominating
- TPE-COV : ~5% correction
- TPE-LM : ~13% correction (consistent with EFT TPE)
- NNLO (EFT) : correction in the range 9~17%
※ -intermediate state : negligible (N. Kaiser, PRC76, 047001 (2007))
A
Summary
Two-pion-exchange parity-violating potentials from covariant formalism and effective field theory are compared.
Same TPE contribution. aLM2 aEFT
2
Higher-order corrections are contrasting.
aEFTCT 0.1 aEFT
2: Good convergence.
aCOV20.3aLM
2 : Significant higher corrections.
1 can be determined from measurement of A in n p -> d
with uncertainty about 10%.
More experiments are absolutely wanted for better understanding of the PV interaction.