What can the L3 γγll\gamma\gamma ll events be?

We consider the 4 $\gamma\gamma ll$ ($l=\mu,\ e$) events reported by the L3 collaboration, and go through the logical possibilities which could explain the events. If they are not coincidental bremsstrahlung events, we find that the physics which they could point to is extremely limited. One possibility would be to have a new 60 GeV scalar (or pseudoscalar) particle $X^0$ with an off-diagonal coupling to a $Z$ and $Z'$ which is non-perturbative ($\alpha > 1$), where the $Z'$ couplings to $\nu\bar\nu$ are suppressed. One could also construct a model involving $X^0$, and a second scalar $X'^0$ with a large $X'll$ coupling. We do not promote either of these models, but hope they would prove to be useful guidelines, should the L3 events turn out to be new physics.Comment: 7 pp (3 fig avail. on request), LATEX, TRI-PP-92-12

Proton decay via dimension-six operators in intersecting D6-brane models

We analyze the proton decay via dimension six operators in supersymmetric SU(5)-Grand Unified models based on intersecting D6-brane constructions in Type IIA string theory orientifolds. We include in addition to 10* 10 10* 10 interactions also the operators arising from 5-bar* 5-bar 10* 10 interactions. We provide a detailed construction of vertex operators for any massless string excitation arising for arbitrary intersecting D-brane configurations in Type IIA toroidal orientifolds. In particular, we provide explicit string vertex operators for the 10 and 5-bar chiral superfields and calculate explicitly the string theory correlation functions for above operators. In the analysis we chose the most symmetric configurations in order to maximize proton decay rates for the above dimension six operators and we obtain a small enhancement relative to the field theory result. After relating the string proton decay rate to field theory computations the string contribution to the proton lifetime is tau^{ST}_p =(0.5-2.1) x 10^{36} years, which could be up to a factor of three shorter than that predicted in field theory.Comment: 46 pages, 2 figures references added, minor correction

Technifermion Representations and Precision Electroweak Constraints

We discuss the selection of fermion representations in technicolor models with a view toward minimizing technicolor contributions to the precision electroweak $S$ parameter. We present and analyze models that involve one technifermion SU(2)$_L$ doublet with standard-model singlet technifermion sectors that lead to walking behavior, which further reduces $S$. We also consider models that have technifermions in higher-dimensional representations and study embeddings in extended technicolor theories.Comment: 8 pages, late

\mbox{SU}(3)_L \otimes \mbox{U}(1)_N and \mbox{SU}(4)_L \otimes \mbox{U}(1)_N gauge models with right-handed neutrinos

Pisano and Pleitez have introduced an interesting \mbox{SU}(3)_C \otimes \mbox{SU}(3)_L \otimes \mbox{U}(1)_N gauge model which has the property that gauge anomaly cancellation requires the number of generations to be a multiple of 3. We consider generalizing that model to incorporate right-handed neutrinos. We find that there exists a non-trivial generalization of the Pisano-Pleitez model with right-handed neutrinos which is actually simpler than the original model in that symmetry breaking can be achieved with just three \mbox{SU}(3)_L triplets (rather than 3 \mbox{SU}(3)_L triplets and a sextet). We also consider a gauge model based on \mbox{SU}(3)_C\otimes \mbox{SU}(4)_L \otimes \mbox{U}(1)_N symmetry. Both of these new models also have the feature that the anomalies cancel only when the number of generations is divisible by 3.Comment: 8, McGill/94-1

Primordial nucleosynthesis with a varying fine structure constant: An improved estimate

We compute primordial light-element abundances for cases with fine structure constant alpha different from the present value, including many sources of alpha dependence neglected in previous calculations. Specifically, we consider contributions arising from Coulomb barrier penetration, photon coupling to nuclear currents, and the electromagnetic components of nuclear masses. We find the primordial abundances to depend more weakly on alpha than previously estimated, by up to a factor of 2 in the case of ^7Li. We discuss the constraints on variations in alpha from the individual abundance measurements and the uncertainties affecting these constraints. While the present best measurements of primordial D/H, ^4He/H, and ^7Li/H may be reconciled pairwise by adjusting alpha and the universal baryon density, no value of alpha allows all three to be accommodated simultaneously without consideration of systematic error. The combination of measured abundances with observations of acoustic peaks in the cosmic microwave background favors no change in alpha within the uncertainties.Comment: Phys. Rev. D accepted version; minor changes in response to refere

General Aspects of Tree Level Gauge Mediation

Tree level gauge mediation (TGM) may be considered as the simplest way to communicate supersymmetry breaking: through the tree level renormalizable exchange of heavy gauge messengers. We study its general structure, in particular the general form of tree level sfermion masses and of one loop, but enhanced, gaugino masses. This allows us to set up general guidelines for model building and to identify the hypotheses underlying the phenomenological predictions. In the context of models based on the "minimal" gauge group SO(10), we show that only two "pure" embeddings of the MSSM fields are possible using $d< 120$ representations, each of them leading to specific predictions for the ratios of family universal sfermion masses at the GUT scale, $m^2_{\bar{5}} = 2 m^2_{10}$ or $m^2_{\bar{5}} = (3/4) m^2_{10}$ (in SU(5) notation). These ratios are determined by group factors and are peculiar enough to make this scheme testable at the LHC. We also discuss three possible approaches to the $\mu$-problem, one of them distinctive of TGM.Comment: 37 pages, 2 figure

Quantifier scope in sentence prosody? : A view from production

Logical scope interpretation and sentence prosody exhibit intricate, yet scarcely studied interrelations across a variety of languages and constructions. Despite these observable interrelations, it is not clear whether quantifier scope by itself is able to directly affect prosodic form. Information structure is a key potential confounding factor, as it appears to richly interact both with scope interpretation and with prosodic form. To address this complication, the current study investigates, based on data from Hungarian, whether quantifier scope is expressed prosodically if information structure is kept in check. A production experiment is presented that investigates grammatically scope ambiguous doubly quantified sentences with varied focus structures, while lacking a syntactically marked topic or focus. In contrast to the information structural manipulation, which is manifest in the analysis of the acoustic data, the results reveal no prosodic effect of quantifier scope, nor the interaction of scope with information structure. This finding casts doubt on the notion that logical scope can receive direct prosodic expression, and it indirectly corroborates the restrictive view instead that scope interpretation is encoded in prosody only in cases in which it is a free rider on information structure

The SUSY-QCD beta function to three loops

A number of DR-bar renormalization constants in softly broken SUSY-QCD are evaluated to three-loop level: the wave function renormalization constants for quarks, squarks, gluons, gluinos, ghosts, and epsilon-scalars, and the renormalization constants for the quark and gluino mass as well as for all cubic vertices. The latter allow us to derive the corresponding beta functions through three loops, all of which we find to be identical to the expression for the gauge beta function obtained by Jack, Jones, and North [Jack:1996vg] (see also Ref. [Pickering:2001aq]). This explicitely demonstrates the consistency of DRED with SUSY and gauge invariance, an important pre-requisite for precision calculations in supersymmetric theories.Comment: Latex, 16 pages, reference added; v2: matches published version in Eur.Phys.J.

HE-LHC: The High-Energy Large Hadron Collider: Future Circular Collider Conceptual Design Report Volume 4

In response to the 2013 Update of the European Strategy for Particle Physics (EPPSU), the Future Circular Collider (FCC) study was launched as a world-wide international collaboration hosted by CERN. The FCC study covered an energy-frontier hadron collider (FCC-hh), a highest-luminosity high-energy lepton collider (FCC-ee), the corresponding 100 km tunnel infrastructure, as well as the physics opportunities of these two colliders, and a high-energy LHC, based on FCC-hh technology. This document constitutes the third volume of the FCC Conceptual Design Report, devoted to the hadron collider FCC-hh. It summarizes the FCC-hh physics discovery opportunities, presents the FCC-hh accelerator design, performance reach, and staged operation plan, discusses the underlying technologies, the civil engineering and technical infrastructure, and also sketches a possible implementation. Combining ingredients from the Large Hadron Collider (LHC), the high-luminosity LHC upgrade and adding novel technologies and approaches, the FCC-hh design aims at significantly extending the energy frontier to 100 TeV. Its unprecedented centre-of-mass collision energy will make the FCC-hh a unique instrument to explore physics beyond the Standard Model, offering great direct sensitivity to new physics and discoveries