Charles J. Horowitz (Indiana)

M. Ramsey-Musolf (Connecticut)

Willem T. H. van Oers (Manitoba)

Gerald A. Miller (Washington)

Peter Ring (Munich)

Workshop supported by the ECT* with additional funds from Jefferson
Laboratory, Indiana University and Indiana University Cyclotron Facility.

Information on the workshop location is at the ECT*
Web Site

Parity violation provides a uniquely clean probe of complex strong interaction dynamics and allows important tests of the Standard Model. There is a new opportunity to use parity violating elastic electron scattering from a heavy nucleus to accurately and model independently measure the neutron density. This could have many implications for atomic parity experiments, nuclear structure and nuclear astrophysics. New results on proton-proton parity violation are being disseminated. The first week of this workshop will focus on parity violating electron scattering, atomic PNC and the nuclear structure related to neutron densities. The second week will focus on parity violation in nuclei and in nucleon scattering.

**For more information:**

Email: charlie@iucf.indiana.edu
1 (812) 855-2959, or

vanoers@physics.umanitoba.ca

<<<< NEW >>>>>

Summary of First Week

Summary of Second Week

Postscript
files for Some talks

List
of Participants including E-mails

**Schedule (Subject to change):**

First Week, June 5-10, 2000

Second
Week, June 12-16, 2000

**List of Topics:**

- Parity violating electron scattering overview
- Parity violating measurements of neutron densities
- Theoretical considerations for neutron density measurements
- Low energy tests of the standard model, M. Ramsey-Musolf [U. Conn.]
- Atomic parity experiments
- Atomic theory for parity violation
- Anapole moments and PV {\it in} nuclei
- Nuclear structure needs of atomic parity, S. Pollock [Boulder]
- Mean field models of neutron densities--relativistic
- Mean field models of neutron densities--non-relativistic
- Effective field theory for neutron densities
- Neutron densities and r-process nucleosynthesis
- Hadronic probes of neutron densities
- The neutron radius of neutron stars

- Parity Violation in Nuclear Systems
- Meson Exchange Model Parameterizations, Weak Meson-Nucleon Couplings
- Nuclear Structure Calculations and Parity Violation
- Parity Violation in Proton-Proton Scattering from Low to High Energies
- Effective Field Theory Descriptions
- Anapole Moment of the Deuteron
- The TRIUMF Proton-Proton Parity Violation Experiments
- Planned Parity Violation Experiments at COSY
- Epithermal Neutron Parity Violation Experiments
- Parity Violating Spin Rotation in Helium and Hydrogen
- Parity Violating Gamma-Ray Asymmetry in $n-p\rightarrow d-\gamma$
- Helicity Dependence in Photodisintegration of the Deuteron
- The effects of Inelasticity and Two-Pion Exchanges
- Proton-Proton Parity Violation Experiments at the AGS and RHIC
- Parity Violation in the Quark-Gluon Regime
- Weak Hyperon Production ($p-n\rightarrow p-\Lambda$)

Parity violation can be used to probe many aspects of the Standard Model
and nuclear

and nucleon structure. First, parity violation in atoms and electron
scattering

will be discussed and then parity violation with hadronic probes.
These two sections

share many important ideas including the crucial role of nuclear structure
and anapole

moments. Anapole moments involve hadronic weak interactions but
are measured with atomic

or electron probes.

The first section of the workshop will bring together atomic, parity
violating

electron scattering and nuclear structure physicists to exploit a new
possibility

for measuring neutron densities. The common theme is neutron
densities:

how they are calculated, how they are measured using hadronic and weak

probes and how this information can be used for atomic parity

experiments, extrapolation to exotic nuclei in radioactive beams and

astrophysics, etc. The workshop will assess our present knowledge
of

neutron densities and the improvements expected from an accurate

measurement. In addition, related parity violating issues will
be

discussed.

The neutron radius of a heavy nucleus can be measured to 1\% using

parity violating electron scattering (because the $Z^0$ couples primarily

to neutrons). This would be the only accurate and model
independent

measurement of the size of a large hadronic system. Because of
the

neutron skin, the size does not follow from the charge radius.

Such a measurement will have many implications for atomic parity violation

(PV), low energy tests of the standard model, nuclear structure, nuclear

astrophysics and the physics of radioactive beams.

It is important to test the standard model at low energy. There
is an

apparent disagreement between the measurement of parity violation in
atomic

Cs and the standard model. As the precision of the atomic
experiments

improve they will need increasingly accurate nuclear structure information

on neutron densities. The most precise standard model test
may involve the

combination of an atomic measurement and PV electron scattering to

constrain the nuclear structure. Atomic measurements suffer from
atomic

theory uncertainties. This motivates measurements of ratios of
PV in

different isotopes. While minimizing the atomic theory uncertainties,

this requires more information on neutron radii of different isotopes.

The present understanding of neutron densities in medium and heavy nuclei

is based on both non-relativistic and relativistic mean field models.

Recent advances in effective field theories may allow the construction

of these mean field models in a more systematic fashion. This
could

allow one to determine the present uncertainty in neutron densities
and

which parts of the effective interaction, such as the surface symmetry

energy, will be constrained by a neutron measurement. This constraint

could be important in the extrapolation to exotic neutron rich nuclei
for

astrophysics or radioactive beams.

Some goals of this first section include: the introduction of atomic
and

electron scattering PV issues to nuclear structure physicists and vice
versa,

to assess interest in and potential impact of a PV neutron density
measurement,

to help optimize possible experiments including the choice of target

(208Pb, 138Ba,...) and to improve the knowledge of neutron densities.

The next section will focus on hadronic probes of parity violation.

There are to date, several recently disseminated experimental

results. First, the TRIUMF proton-proton parity violation experiment
has

obtained a result for the longitudinal analyzing power A_z at
an energy

(221.3~MeV) where only the weak rho-nucleon coupling constant plays
a role. The

measured value for A_z places an important constraint on the weak rho-nucleon

coupling constant. Together with the low energy results from the Paul
Scherrer

Institute and the University of Bonn, constraints can now be imposed
on both

the weak rho-nucleon and omega-nucleon coupling constants. Secondly,
the

measurements of the anapole moments have led to deductions of the weak

pion-nucleon coupling constant. However, there appears to be an inconsistency

between the anapole moments for 133Cs and 205Tl. But even more

importantly the value of the weak pion-nucleon coupling constant deduced
from

the anapole moment of 133Cs does not agree with the weak pion-nucleon

coupling constant deduced from the value of the circular polarization
of

1.081~MeV gamma-rays of the decay of the well-known parity mixed doublet
in

18F, for which the nuclear structure is relatively well known. One
notes

that there are several experiments, which have measured the circular

polarization of the 1.081~MeV gamma-rays, giving results in mutual
agreement.

An interesting way to reconcile the different experimental results
is to

postulate that the weak meson-nucleon coupling constants depend on
the nuclear

medium. Thirdly, there now exists a large body of parity violating
longitudinal

analyzing power data obtained in scattering of epithermal neutrons
from a large

range of nuclei throughout the periodic table. Very large parity violating

effects have been observed; but extraction of the weak meson-nucleon
coupling

constants appears a daunting task. And fourthly, there is the old,
but still

unexplained, experiment performed at the ZGS of Argonne National Laboratory,

measuring the longitudinal analyzing power in scattering protons from
a water

target, which has given a result more than ten times larger than what
is

expected from simple scaling arguments.

Several new parity violation experiments are currently in preparation:
a

measurement of the parity violating longitudinal analyzing power A_z
in

proton-proton scattering at 450~MeV at TRIUMF and at a few GeV at COSY
(in a

novel cooled stored beam environment); a measurement of the parity
violating

asymmetry in the capture of longitudinally polarized epithermal neutrons
by

hydrogen at LANSCE; a measurement of the parity violating spin rotation
of cold

neutrons passing through hydrogen (and also helium) at ILL and NIST.

The second part of the Workshop is to bring perspective to this

subfield of fundamental symmetries.

The general purpose of such studies is in using the weak interaction
to learn

about more difficult aspects of the strong interaction including the
derivation

of the meson-nucleon coupling constants, the nucleon-nucleon potential,
and the

precise treatment of the many-body problem. Some specific questions
to be

addressed are:

- can a unique set of the six (or seven) weak meson-nucleon coupling constants be deduced from a combination of the presently existing nuclear parity violation data and nucleon-nucleon parity violating scattering asymmetries
- do the weak meson-nucleon coupling constants exhibit a nuclear medium dependence
- what are the effects of inelasticity in the deduction of the weak meson-nucleon coupling constants from proton-proton longitudinal analyzing power data
- which are the crucial experiments which must be performed to further advance the field;
- have theoretical frameworks been developed to the point that improved calculations of the weak meson-nucleon coupling constants can be made;
- what is the range of validity of the meson-exchange model parameterization in terms of the weak meson-nucleon coupling constants;
- how to proceed from the meson-exchange model parameterization to a more fundamental description in terms of quarks and gluons;
- which are the real possibilities to perform a tens of GeV proton-proton parity violation experiment;
- is there an optimum energy for such an experiment and which is the facility where the experiment can be performed?