5751474
Implications of supersymmetric models with natural R-parity conservation.
In the minimal supersymmetric standard model, the conservation of {ital R} parity is phenomenologically desirable, but is {ital ad} {ital hoc} in the sense that it is not required for the internal consistency of the theory. However, if {ital B}{minus}{ital L} is gauged at very high energies, {ital R} parity will be conserved automatically and exactly, provided only that all order parameters carry even integer values of 3({ital B}{minus}{ital L}). We propose a minimal extension of the supersymmetric standard model in which {ital R}-parity conservation arises naturally in this way. This approach predicts the existence of a very weakly coupled, neutral chiral supermultiplet of particles with electroweak-scale masses and lifetimes which may be cosmologically interesting. Neutrino masses arise via an intermediate-scale seesaw mechanism, and a solution to the {mu} problem is naturally incorporated. The apparent unification of gauge couplings at high energies is shown to be preserved in this approach. We also discuss a next-to-minimal extension, which predicts a pair of electroweak-scale chiral supermultiplets with electric charge 2. {copyright} {ital 1996 The American Physical Society.}
43631942
Refined gluino and squark pole masses beyond leading order
The physical pole and running masses of squarks and gluinos have recently been related at two-loop order in a mass-independent renormalization scheme. I propose a general method for improvement of such formulas, and argue that better accuracy results. The improved version gives an imaginary part of the pole mass that agrees exactly with the direct calculation of the physical width at next-to-leading order. I also find the leading three-loop contributions to the gluino pole mass in the case that squarks are heavier, using effective field theory and renormalization group methods. The efficacy of these improvements for the gluino and squarks is illustrated with numerical examples. Some necessary three-loop results for gauge coupling and fermion mass beta functions and pole masses in theories with more than one type of fermion representation, which are not directly accessible from the published literature, are presented in an Appendix.
44961063
Two-loop scalar self-energies in a general renormalizable theory at leading order in gauge couplings
I present results for the two-loop self-energy functions for scalars in a general renormalizable field theory, using mass-independent renormalization schemes based on dimensional regularization and dimensional reduction. The results are given in terms of a minimal set of loop-integral basis functions, which are readily evaluated numerically by computers. This paper contains the contributions corresponding to the Feynman diagrams with zero or one vector propagator lines. These are the ones needed to obtain the pole masses of the neutral and charged Higgs scalar bosons in supersymmetry, neglecting only the purely electroweak parts at two-loop order. A subsequent paper will present the results for the remaining diagrams, which involve two or more vector lines. I also include an illustrative example, featuring several nontrivial consistency checks.
122018065
BRST current algebra anomalies in string theory
Abstract We have calculated the operator product of the BRST current with itself in the cases of bosonic and fermionic strings. Despite some confusion in the recent literature, these operator products cannot vanish. In fact they are equal to total derivatives only if the total derivative part of the (super) BRST current is chosen correctly. Thus the BRST current algebra has anomalous Schwinger terms.
118973381
A Supersymmetry Primer
I provide a pedagogical introduction to supersymmetry. The level of discussion is aimed at readers who are familiar with the Standard Model and quantum field theory, but who have had little or no prior exposure to supersymmetry. Topics covered include: motivations for supersymmetry, the construction of supersymmetric Lagrangians, supersymmetry-breaking interactions, the Minimal Supersymmetric Standard Model (MSSM), R-parity and its consequences, the origins of supersymmetry breaking, the mass spectrum of the MSSM, decays of supersymmetric particles, experimental signals for supersymmetry, and some extensions of the minimal framework.
120869890
Conformal field theory representation and background-independent action for superstring field theory
Abstract The two-dimensional conformal field theory representation of Witten's open superstring field theory is discussed. We argue that the previously suggested cubic action for the superstring is actually dependent on the spacetime background, and suggest a modification which formally removes this dependence. The transformation from the new version of the superstring cubic action to Witten's action for open string states is discussed. A class of linearized solutions to the equations of motion of the open superstring cubic action are exhibited. These solutions are in one-to-one correspondence with the physical excitations (both massless and massive) of the open and closed type I superstrings.
17649647
Variational approximation for two-time correlation functions in Phi 4 theory: Optimization of the dynamics.
We apply the time-dependent variational principle of Balian and Veneroni to {Phi}{sup 4} theory. An appropriate parametrization for the variational objects allows us to write coupled dynamical equations from which we derive approximations for the two-time correlation functions involving two, three, or four field operators. {copyright} 1995 The American Physical Society.
41996012
Stability of systems of three arbitrary charges: General properties.
The stability of systems consisting of a negative charge {minus}{ital q}{sub 1} and two positive charges {ital q}{sub 2} and {ital q}{sub 3} is discussed as a function of the values of the charges {ital q}{sub {ital i}} and of the constituent masses {ital m}{sub {ital i}}. We give general results and list some open questions of interest, which hopefully will stimulate further investigations.
26174937
Description of F2 at small x incorporating angular ordering.
We study the perturbative QCD description of the DESY HERA measurements of {ital F}{sub 2}({ital x},{ital Q}{sup 2}) using a gluon distribution that is obtained from an evolution incorporating angular ordering of the gluon emissions, and which embodies both GLAP and BFKL dynamics. We compare the predictions with recent HERA data for {ital F}{sub 2} and its charm component {ital F}{sup {ital c}}{sub 2}. We also present estimates of the longitudinal structure function {ital F}{sub {ital L}}. {copyright} {ital 1996 The American Physical Society.}
16739726
Spacings of quarkonium levels with the same principal quantum number.
The spacings between bound-state levels of the Schr{umlt o}dinger equation with the same principal quantum number {ital N} but orbital angular momenta {ital l} differing by unity are found to be nearly equal for a wide range of power potentials {ital V}={lambda}{ital r}{sup {nu}}, with {ital E}{sub {ital Nl}}{approx_equal}{ital F}({nu},{ital N}){minus}{ital G}({nu},{ital N}){ital l}. Semiclassical approximations are in accord with this behavior. The result is applied to estimates of masses for quarkonium levels which have not yet been observed, including the 2{ital P} {ital c{bar c}} states and the 1{ital D} {ital b{bar b}} states. {copyright} {ital 1996 The American Physical Society.}
28650811
Crossing intrinsic depolarizing resonances by varying a partial Siberian snake.
We recently forced a 140 MeV polarized proton beam to cross intrinsic depolarizing resonances by varying a partial Siberian snake{close_quote}s strength for different values of the vertical and horizontal betatron tunes {nu}{sub {ital y}} and {nu}{sub {ital x}}. A weak second-order intrinsic resonance was observed in the {nu}{sub {ital x}} sweep; moreover, an unexpected partial spin flip was found in the {nu}{sub {ital y}} sweep. We also varied the snake ramp time to identify the {nu}{sub {ital y}} and {nu}{sub {ital x}} regions where the resonance crossings occurred during the snake variation; in these crossings the polarization partially deviated from Froissart-Stora behavior. {copyright} {ital 1996 The American Physical Society.}