Parity Violation In Few-nucleon Systems Research Articles

The theory of hadronic parity violation

Parity-violating interactions between nucleons are the manifestation of an interplay of strong and weak interactions between quarks in the nucleons. Compared to the dominant parity-conserving part, the parity-violating component of the nuclear force is typically suppressed by approximately 6 to 7 orders of magnitude or more. Due to the short range of the weak interactions, however, it provides a unique probe of the strong dynamics that confine quarks into nucleons. An ongoing experimental program is mapping out this weak component of the nuclear force in few-nucleon systems. I will discuss recent theoretical progress based on effective field theory methods to analyze and interpret hadronic parity violation in few-nucleon systems, with a particular focus on two- and three-nucleon systems.

Status of Theory and Experiment in Hadronic Parity Violation

Hadronic parity violation uses quark-quark weak interactions to probe nonperturbative strong interaction dynamics through two nonperturbative QCD scales: [Formula: see text] and the fine-tuned MeV scales of NN bound states in low energy nuclear physics. The current and projected availability of high-intensity neutron and photon sources coupled with ongoing experiments and continuing developments in theoretical methods provide the opportunity to greatly expand our understanding of hadronic parity violation in few-nucleon systems. The current status of these efforts and future plans are discussed.

Hadronic parity violation in few-body systems

Efforts to describe hadronic parity violation in few-nucleon systems using effective field theories are described. Particular emphasis is given to observables in two- and three-nucleon systems and their relation to ongoing experimental efforts. The role of parityviolating three-nucleon interactions is also discussed.

Hadronic parity violation in few-nucleon systems

The interactions between nucleons contain a parity-violating component, which originates in the weak interaction between quarks and which is suppressed by a factor of approximately 10−7 compared to the dominant parity-conserving component. A theoretical framework based on effective field theory methods to analyze and interpret parity-violating interactions between nucleons is described and a number of applications are discussed.

Chiral effective field theory analysis of hadronic parity violation in few-nucleon systems

We reconsider the derivation of the nucleon-nucleon parity-violating (PV) potential within a chiral effective field theory framework. We construct the potential up to next-to-next-to-leading order by including one-pion-exchange, two-pion-exchange, contact, and 1/M (M being the nucleon mass) terms, and use dimensional regularization to renormalize the pion-loop corrections. A detailed analysis of the number of independent low-energy constants (LEC's) entering the potential is carried out. We find that it depends on six LEC's: the pion-nucleon PV coupling constant $h^1_\pi$ and five parameters multiplying contact interactions. We investigate PV effects induced by this potential on several few-nucleon observables, including the $\vec{p}$-$p$ longitudinal asymmetry, the neutron spin rotation in $\vec{n}$-$p$ and $\vec{n}$-$d$ scattering, and the longitudinal asymmetry in the $^3$He$(\vec{n},p)^3$H charge-exchange reaction. An estimate for the range of values of the various LEC's is provided by using available experimental data.

Hadronic parity violation in few-nucleon systems

The weak interaction between quarks induces a parity-violating component in the interactions between nucleons, which is typically suppressed by a factor of \({\approx 10^{-7}}\) compared to the dominant parity-conserving part. Because of the short range of the weak interactions, it provides a unique probe of the strong dynamics that confine quarks into nucleons. An experimental program to map out this weak component of the nuclear force is underway at a number of facilities, including the Spallation Neutron Source at Oak Ridge National Laboratory. The corresponding observables are related to few-nucleon processes at very low energies, at which pionless effective field theory provides a reliable and model-independent theoretical approach to hadronic parity violation. Results in two- and three-nucleon systems, the role of parity-violating three-nucleon forces, and possible extensions to other few-nucleon systems are discussed.

Hadronic Parity Violation in Few-Nucleon Systems

The weak interaction between quarks induces a parity-violating component in the interactions between nucleons, which is typically suppressed by a factor of $${\approx 10^{-7}}$$ compared to the dominant parity-conserving part. Because of the short range of the weak interactions, it provides a unique probe of the strong dynamics that confine quarks into nucleons. An experimental program to map out this weak component of the nuclear force is underway at a number of facilities, including the Spallation Neutron Source at Oak Ridge National Laboratory. The corresponding observables are related to few-nucleon processes at very low energies, at which pionless effective field theory provides a reliable and model-independent theoretical approach to hadronic parity violation. Results in two- and three-nucleon systems, the role of parity-violating three-nucleon forces, and possible extensions to other few-nucleon systems are discussed.

Study of parity violating observables in few-nucleon systems

Parity violation in few-nucleon systems is studied using a nucleon-nucleon parity-violating (PV) potential derived within an effective field theory framework at next-to-next-to-leading order. The potential includes one- and two-pion exchanges, contact interactions and relativistic corrections and depends on six low-energy constants: the pion-nucleon coupling constant h1π and five parameters multiplying the independent contact interaction terms (with one four-gradient). This potential is used to study the p⃗-p longitudinal asymmetry, the neutron spin rotation in n⃗-d scattering, and the longitudinal asymmetry in the 3He(n⃗,p)3H reaction.

Strangeness-conserving hadronic parity violation at low energies

The parity-violating nucleaon interacton is the key to understanding the strangeness-conserving hadronic weak interaction at low energies. In this brief talk, I review the past accomplishement in and current status of this subject, and outline a new joint effort between experiment and theory that that tries to address the potential problems in the past by focusing on parity violation in few-nucleon systems and using the language of effective field theory.

Parity violation in few-nucleon systems

We summarize recent results on parity-violation in few-nucleon systems, including pp elastic scattering and np radiative capture. These results are relevant to recent or present experimental measurements at TRIUMF and LANSCE, respectively. We also present results for other potential or planned experiments, summarizing the contributions they will make to understanding the weak parity-violating NN interaction. Dependencies upon the NN strong interaction are also addressed. PACS: 21.30.+v Few-body systems – 24.80.+y Nuclear tests of fundamental interactions and symmetries

PARITY VIOLATION IN FEW-NUCLEON SYSTEMS: WHERE DO WE STAND?

We review the present status of our understanding of parity violation in few-nucleon systems. At low energies, nuclear parity-violating forces can be parametrized in the framework of meson-exchange potentials. The pertinent weak meson-nucleon couplings can be calculated by invoking either the quark or the soliton model of the low-lying baryons. We compare the resulting couplings and discuss the advantages and limitations of both approaches. Then, we turn to the experimental study of nuclear parity violation in few-nucleon systems. First, we review various calculations of the longitudinal asymmetry in proton-proton scattering with an eye on the upcoming high-precision experiment at TRIUMF. We stress the importance of a consistent calculation of the weak and strong nucleon-nucleon potential. A toy calculation is presented for the photo-disintegration of the dueteron, which appears to be an excellent candidate to pin down the parity-violating pion-nucleon coupling constant. We encourage further theoretical as well as experimental studies.