Daniel T. Larson

Electroproduction of single pions at low E and a measurement of the pion form factor up to Q = 10 G~V~

We report measurements of the electroproduction of single charged pions from hydrogen and deuterium targets for values of epsilon in the range 0.35 < epsilon < 0.45. Data were taken with a hydrogen target at the (W,Q/sup 2/) points (2.15 GeV, 1.2 GeV/sup 2/), (2.65, 2.0), (2.65, 3.4), (2.65, 6.0), and (2.65, 10.0). Data were taken with a deuterium target at the (W, Q/sup 2/) points (2.15, 1.2) and (2.65, 2.0). The transverse cross section obtained by using these data in conjunction with earlier data at high epsilon to separate the longitudinal and transverse components is used in conjunction with the new data and the t-channel Born term to determine the pion form factor and to re-evaluate previously reported measurements. In the range 0.15 GeV/sup 2/ < Q/sup 2/ < 10.0 GeV/sup 2/ the pion form factor can be described by the simple pole form (1 + Q/sup 2//(0.462 +- 0.024))/sup -/1.

Atmospheric neutrinos can make beauty strange

The large observed mixing angle in atmospheric neutrinos, coupled with Grand Unification, motivates the search for a large mixing between right-handed strange and bottom squarks. Such mixing does not appear in the standard CKM phenomenology, but may induce significant b {yields} s transitions through gluino diagrams. Working in the mass eigenbasis, we show quantitatively that an order one effect on CP violation in B{sub d}{sup 0} {yields} {pi}K{sub S} is possible due to a large mixing between right-handed b and s squarks, while still satisfying constraints from b {yields} s {gamma}. We also include the effect of right- and left-handed bottom squark mixing proportional to m{sub b}{mu} tan{beta}. For small {mu}tan{beta} there may also be a large effect in B{sub s} mixing correlated with a large effect in B{sub d}{sup 0} {yields} {phi}K{sub S}, typically yielding an unambiguous signal of new physics at Tevatron Run II.

Probing the Planck Scale with Proton Decay

We advocate the idea that proton decay may probe physics at the Planck scale instead of the GUT scale. This is possible because supersymmetric theories have dimension-5 operators that can induce proton decay at dangerous rates, even with R-parity conservation. These operators are expected to be suppressed by the same physics that explains the fermion masses and mixings. We present a thorough analysis of nucleon partial lifetimes in models with a string-inspired anomalous U(1)_X family symmetry which is responsible for the fermionic mass spectrum as well as forbidding R-parity violating interactions. Protons and neutrons can decay via R-parity conserving non-renormalizable superpotential terms that are suppressed by the Planck scale and powers of the Cabibbo angle. Many of the models naturally lead to nucleon decay near present limits without any reference to grand unification.

Electroproduction of single pions at low epsilon and a measurement of the pion form factor up to Q/sup 2/ = 10 GeV/sup 2/

We report measurements of the electroproduction of single charged pions from hydrogen and deuterium targets for values of epsilon in the range 0.35 < epsilon < 0.45. Data were taken with a hydrogen target at the (W,Q/sup 2/) points (2.15 GeV, 1.2 GeV/sup 2/), (2.65, 2.0), (2.65, 3.4), (2.65, 6.0), and (2.65, 10.0). Data were taken with a deuterium target at the (W, Q/sup 2/) points (2.15, 1.2) and (2.65, 2.0). The transverse cross section obtained by using these data in conjunction with earlier data at high epsilon to separate the longitudinal and transverse components is used in conjunction with the new data and the t-channel Born term to determine the pion form factor and to re-evaluate previously reported measurements. In the range 0.15 GeV/sup 2/ < Q/sup 2/ < 10.0 GeV/sup 2/ the pion form factor can be described by the simple pole form (1 + Q/sup 2//(0.462 +- 0.024))/sup -/1.