HST ultraviolet spectral energy distributions for three ultraluminous infrared galaxies

We present HST Faint Object Camera ultraviolet (230 nm and 140 nm) images of three ultraluminous infrared galaxies (ULIG: L_ir > 10^12 L_sun) selected from the IRAS Revised Bright Galaxy Sample. The purpose is to estimate spectral energy distributions (SEDs) to facilitate the identification of similar objects at high redshift in deep optical, infrared, and submm surveys. All three galaxies (VII Zw031 = IRAS F12112+0305, and IRAS F22491-1808) were well detected at 230 nm. Two of the three were marginally detected at 140 nm. The fluxes, together with ground-based optical and infrared photometry, are used to compute SEDs over a wide wavelength range. The measured SEDs drop from the optical to the ultraviolet, but the magnitude of the drop ranges from a factor of ~3 in IRAS F22491-1808 to a factor of ~100 in VIIZw031. This is most likely due to different internal extinctions. Such an interpretation is also suggested by extrapolating to ultraviolet wavelengths the optical internal extinction measured in VIIZw031. K-corrections are calculated to determine the colors of the sample galaxies as seen at high redshifts. Galaxies like VIIZw031 have very low observed rest-frame UV fluxes which means that such galaxies at high redshift will be extremely red or even missing in optical surveys. On the other hand, galaxies like IRAS F12112+0305 and IRAS F22491-1808, if seen at high redshift, would be sufficiently blue that they would not easily be distinguished from normal field galaxies, and therefore, identified as ULIGs. The implication is then that submillimeter surveys may be the only means of properly identifying the majority of ULIGs at high redshift.Comment: AJ in press, TeX, 23 pages, 7 tab, 17 figs available also (at higher resolution) from http://www.ast.cam.ac.uk~trentham/ufigs.htm

Probing color-singlet exchange in Z+2Z+2-jet events at the LHC

The purely electroweak process $qq\to qqZ$ (via $t$-channel $\gamma/Z$ or $W$ exchange) provides a copious and fairly clean source of color-singlet exchange events in $pp$ collisions at the LHC. A judicious choice of phase-space region allows the suppression of QCD backgrounds to the level of the signal. The color-singlet-exchange signal can be distinguished from QCD backgrounds by the radiation patterns of additional minijets in individual events. A rapidity-gap trigger at the minijet level substantially enhances the signal versus the background. Analogous features of weak boson scattering events make $Z+2$-jet events at the LHC an ideal laboratory for investigation of the soft-jet activity expected in weak-boson scattering events.Comment: 24 pages (with 7 embedded figures), Revtex, uses epsf.sty. Z-compressed postscript version also available at http://phenom.physics.wisc.edu/pub/preprints/1996/madph-96-943.ps.Z or at ftp://phenom.physics.wisc.edu/pub/preprints/1996/madph-96-943.ps.

The Central Temperature of the Sun can be Measured via the 7^7Be Solar Neutrino Line

A precise test of the theory of stellar evolution can be performed by measuring the difference in average energy between the neutrino line produced by ${\rm ^7Be}$ electron capture in the solar interior and the corresponding neutrino line produced in a terrestrial laboratory. The high temperatures in the center of the sun broaden the line asymmetrically, FWHM = 1.6~keV, and cause an average energy shift of 1.3~keV. The width of the $^7$Be neutrino line should be taken into account in calculations of vacuum neutrino oscillations.Comment: RevTeX file, 9 pages. For hardcopy with figure, send to [email protected]. Institute for Advanced Study number AST 93/4

Charged Heavy Lepton Production In Superstring Inspired E6 Models

The possibility of studying superstring inspired \mbox{${\rm E}_6$} phenomenology at high energy hadron colliders is investigated. A very simple low energy rank-5 Supersymmetric (N=1) model is considered, which consists of three scalar-Higgses, $H^0_{i=1,2,3}\,$, two charged-Higgses, $H^\pm\,$, one pseudo-scalar-Higgses, $P^0\,$, and an extra vector boson, the $Z^\prime$. The production of charged heavy leptons pairs, $L^+L^-\,$, by gluon-gluon fusion and Drell-Yan mechanisms is discussed. For gluon-gluon fusion an enhancement in the parton level cross-section is expected due to the heavy (s)fermion loops which couple to the gluons. This mechanism is expected to dominate over Drell-Yan for $L^+L^-$ invariant masses above the $Z^\prime$ mass.Comment: 65 pages, LaTeX file, 26 figures, also available at http://www.physics.carleton.ca/~boyce/papers/prd96.p

Is Large Lepton Mixing Excluded?

The original \bnum -(or $\bar{\nu}_{\tau}$-) energy spectrum from the gravitational collapse of a star has a larger average energy than the spectrum for \bnue since the opacity of \bnue exeeds that of \bnum (or $\nu_{\tau}$). Flavor neutrino conversion, \bnue $\leftrightarrow$ \bnum, induced by lepton mixing results in partial permutation of the original \bnue and \bnum spectra. An upper bound on the permutation factor, $p \leq 0.35$ (99$\%$ CL) is derived using the data from SN1987A and the different models of the neutrino burst. The relation between the permutation factor and the vacuum mixing angle is established, which leads to the upper bound on this angle. The excluded region, $\sin^2 2\theta > 0.7 - 0.9$, covers the regions of large mixing angle solutions of the solar neutrino problem: ``just-so" and, partly, MSW, as well as part of region of $\nu_{e} - \nu_{\mu}$ oscillation space which could be responsible for the atmospheric muon neutrino deficit. These limits are sensitive to the predicted neutrino spectrum and can be strengthened as supernova models improve.Comment: 20 pages, TeX file. For hardcopy with figures contact [email protected]. Institute for Advanced Study number AST 93/1

Constrained Supersymmetric Flipped SU(5) GUT Phenomenology

We explore the phenomenology of the minimal supersymmetric flipped SU(5) GUT model (CFSU(5)), whose soft supersymmetry-breaking (SSB) mass parameters are constrained to be universal at some input scale, $M_{in}$, above the GUT scale, $M_{GUT}$. We analyze the parameter space of CFSU(5) assuming that the lightest supersymmetric particle (LSP) provides the cosmological cold dark matter, paying careful attention to the matching of parameters at the GUT scale. We first display some specific examples of the evolutions of the SSB parameters that exhibit some generic features. Specifically, we note that the relationship between the masses of the lightest neutralino and the lighter stau is sensitive to $M_{in}$, as is the relationship between the neutralino mass and the masses of the heavier Higgs bosons. For these reasons, prominent features in generic $(m_{1/2}, m_0)$ planes such as coannihilation strips and rapid-annihilation funnels are also sensitive to $M_{in}$, as we illustrate for several cases with tan(beta)=10 and 55. However, these features do not necessarily disappear at large $M_{in}$, unlike the case in the minimal conventional SU(5) GUT. Our results are relatively insensitive to neutrino masses.Comment: 23 pages, 8 figures; (v2) added explanations and corrected typos, version to appear in EPJ

The AdS/QCD Correspondence: Still Undelivered

We consider the particle spectrum and event shapes in large N gauge theories in different regimes of the short-distance 't Hooft coupling, lambda. The mesons in the small lambda limit should have a Regge spectrum in order to agree with perturbation theory, while generically the large lambda theories with gravity duals produce spectra reminiscent of KK modes. We argue that these KK-like states are qualitatively different from QCD modes: they are deeply bound states which are sensitive to short distance interactions rather than the flux tube-like states expected in asymptotically free, confining gauge theories. In addition, we also find that the characteristic event shapes for the large lambda theories with gravity duals are close to spherical, very different from QCD-like (small lambda, small N) and Nambu-Goto-like (small lambda, large N) theories which have jets. This observation is in agreement with the conjecture of Strassler on event shapes in large 't Hooft coupling theories, which was recently proved by Hofman and Maldacena for the conformal case. This conclusion does not change even when considering soft-wall backgrounds in the gravity dual. The picture that emerges is the following: theories with small and large lambda are qualitatively different, while theories with small and large N are qualitatively similar. Thus it seems that it is the relative smallness of the 't Hooft coupling in QCD that prevents a reliable AdS/QCD correspondence from emerging, and that reproducing characteristic QCD-like behavior will require genuine stringy dynamics to be incorporated into any putative dual theory.Comment: 32 pages, 15 figures; references added, minor changes, history clarifie