11226857
Dynamical electroweak symmetry breaking with top-quark and neutrino condensates.
Recently it has been suggested that electroweak symmetry is broken by a top-quark vacuum condensate. In that model, the prediction for the top-quark mass seems to be in conflict with indirect experimental upper bounds. We propose a new scenario in which electroweak symmetry is broken by a combination of top-quark and third-generation neutrino condensates, involving a right-handed gauge-singlet neutrino. We show that the top-quark mass comes out smaller in this model and can easily lie in the experimentally favored window. The resulting neutrino spectrum is phenomenologically acceptable if we make the natural assumption that the right-handed neutrino has a large Majorana mass.
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.
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.
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.
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.
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.
10342426
Physically meaningful and not so meaningful symmetries in Chern-Simons theory.
We explicitly show that the Landau gauge supersymmetry of Chern-Simons theory does not have any physical significance. In fact, the difference between an effective action that is both Becchi-Rouet-Stora (BRS) invariant and Landau supersymmetric and an effective action that is only BRS invariant is a finite field redefinition. Having established this, we use a BRS-invariant regulator that defines CS theory as the large mass limit of topologically massive Yang-Mills theory to discuss the shift [ital k][r arrow][ital k]+[ital c][sub [ital V]] of the bare Chern-Simons parameter [ital k] in connection with the Landau supersymmetry. Finally, to convince ourselves that the shift above is not an accident of our regularization method, we comment on the fact that all BRS-invariant regulators used as yet yield the same value for the shift.
19437204
Parton distributions for the pion extracted from Drell-Yan and prompt photon experiments.
We determine the parton distributions of the pion from a consistent next-to-leading-order analysis of several high-statistics π ± N experiments including both Drell-Yan and prompt photon production
14833247
Deep inelastic events containing a forward photon as a probe of small x dynamics.
We calculate the rate of producing deep inelastic events containing an energetic isolated forward photon at DESY HERA. We quantify the enhancement arising from the leading log1/{ital x} gluon emissions with a view to using such events to identify the underlying dynamics. {copyright} {ital 1996 The American Physical Society.}
33800044
Finite-size and dynamical effects in pair production by an external field.
We evaluate the rate of pair production in a uniform electric field confined to a bounded region in space. Using the Balian-Bloch expansion of Green's functions we obtain explicit expressions for finite-size corrections to Schwinger's formula. The case of a time-dependent boundary, relevant to describe energy deposition by quark-antiquark pair production in ultrarelativistic collisions, is also investigated. We find that finite-size effects are important in nuclear collisions. They decrease when the strength of the chromoelectric field between the nuclei is large. As a result, the rate of energy deposition increases sharply with the mass number {ital A} of the colliding nuclei.
23673028
New information on parton distributions.
New data on structure functions from deep-inelastic scattering provide new information on parton distributions, particularly in the 0.01[lt][ital x][lt]0.1 interval. This has important implications for predictions for the DESY [ital ep] collider HERA and for present and future high-energy hadron colliders. We present the results of updated fits to all available precision structure function and related data. We focus in particular on two issues: (a) the increase in the sea-quark distribution at small [ital x] implied by new [ital F][sub 2] data from the New Muon Collaboration, and its implications for other processes, and (b) the evidence for SU(2)-symmetry breaking in the light-quark sea. We show that although good fits can be obtained with or without this symmetry breaking, more physically reasonable parton distributions are obtained if we allow [ital [bar d]][gt][ital [bar u]] at small [ital x]. With the inclusion of the latest deep-inelastic data we find [alpha][sub [ital s]]([ital M][sub [ital Z]])=0.111[sub [minus]0.005][sup +0.004]. We also show how [ital W], [ital Z], and Drell-Yan production at [ital [bar p]p] colliders can give information on parton distributions.