Two-loop Renormalization Group Equations in the Standard Model

Two-loop renormalization group equations in the standard model are re-calculated. A new coefficient is found in the beta-function of the quartic coupling and a class of gauge invariants are found to be absent in the beta-functions of hadronic Yukawa couplings. The two-loop beta-function of the Higgs mass parameter is presented in complete form.Comment: 4 pages, RevTe

Irregular sloshing cold fronts in the nearby merging groups NGC 7618 and UGC 12491: evidence for Kelvin-Helmholtz instabilities

We present results from two \sim30 ks Chandra observations of the hot atmospheres of the merging galaxy groups centered around NGC 7618 and UGC 12491. Our images show the presence of arc-like sloshing cold fronts wrapped around each group center and \sim100 kpc long spiral tails in both groups. Most interestingly, the cold fronts are highly distorted in both groups, exhibiting 'wings' along the fronts. These features resemble the structures predicted from non-viscous hydrodynamic simulations of gas sloshing, where Kelvin-Helmholtz instabilities (KHIs) distort the cold fronts. This is in contrast to the structure seen in many other sloshing and merger cold fronts, which are smooth and featureless at the current observational resolution. Both magnetic fields and viscosity have been invoked to explain the absence of KHIs in these smooth cold fronts, but the NGC 7618/UGC 12491 pair are two in a growing number of both sloshing and merger cold fronts that appear distorted. Magnetic fields and/or viscosity may be able to suppress the growth of KHIs at the cold fronts in some clusters and groups, but clearly not in all. We propose that the presence or absence of KHI-distortions in cold fronts can be used as a measure of the effective viscosity and/or magnetic field strengths in the ICM.Comment: ApJ, accepted. Uses emulateapj styl

Two-loop Renormalization Group Equations in General Gauge Field Theories

The complete set of two-loop renormalization group equations in general gauge field theories is presented. This includes the \beta functions of parameters with and without a mass dimension

Seed Germination after Mixing with Fertilizers

If a 2-day soaking rain starts during seeding and you have to pull out of the field, what do you do with the mix left in the box? How long can small grain or alfalfa seed be mixed with fertilizer before germination is affected? We used wheat, oat, barley, and alfalfa seed and seven fertilizers in germination tests to find more precise answers than we\u27ve had to this point

Constraints on Mass Spectrum of Fourth Generation Fermions and Higgs Bosons

We reanalyze constraints on the mass spectrum of the chiral fourth generation fermions and the Higgs bosons for the standard model (SM4) and the two Higgs doublet model (THDM). We find that the Higgs mass in the SM4 should be larger than roughly the fourth generation up-type quark mass, while the light CP even Higgs mass in the THDM can be smaller. Various mass spectra of the fourth generation fermions and the Higgs bosons are allowed. The phenomenology of the fourth generation models is still rich.Comment: 15 pages, 16 figures; some points clarified, references added, to appear in Phys.Rev.

Higgs Boson Bounds in Three and Four Generation Scenarios

In light of recent experimental results, we present updated bounds on the lightest Higgs boson mass in the Standard Model (SM) and in the Minimal Supersymmetric extension of the Standard Model (MSSM). The vacuum stability lower bound on the pure SM Higgs boson mass when the SM is taken to be valid up to the Planck scale lies above the MSSM lightest Higgs boson mass upper bound for a large amount of SUSY parameter space. If the lightest Higgs boson is detected with a mass M_{H} < 134 GeV (150 GeV) for a top quark mass M_{top} = 172 GeV (179 GeV), it may indicate the existence of a fourth generation of fermions. The region of inconsistency is removed and the MSSM is salvagable for such values of M_{H} if one postulates the existence of a fourth generation of leptons and quarks with isodoublet degenerate masses M_{L} and M_{Q} such that 60 GeV 170 GeV.Comment: 7 pages, 4 figures. To be published in Physical Review

Spectacular X-ray tails, intracluster star formation and ULXs in A3627

We present the discovery of spectacular double X-ray tails associated with ESO137-001 and a possibly heated X-ray tail associated with ESO137-002, both late-type galaxies in the closest rich cluster Abell 3627. A deep Chandra observation of ESO137-001 allows us for the first time to examine the spatial and spectral properties of such X-ray tails in detail. Besides the known bright tail that extends to ~ 80 kpc from ESO137-001, a fainter and narrower secondary tail with a similar length was surprisingly revealed. There is little temperature variation along both tails. We also identified six X-ray point sources as candidates of intracluster ULXs with L(0.3-10 keV) of up to 2.5x10^40 erg s^-1. Gemini spectra of intracluster HII regions downstream of ESO137-001 are also presented, as well as the velocity map of these HII regions that shows the imprint of ESO137-001's disk rotation. For the first time, we unambiguously know that active star formation can happen in the cold ISM stripped by ICM ram pressure and it may contribute a significant amount of the intracluster light. We also report the discovery of a 40 kpc X-ray tail of another late-type galaxy in A3627, ESO137-002. Its X-ray tail seems hot, ~ 2 keV (compared to ~ 0.8 keV for ESO137-001's tails). We conclude that the high pressure environment around these two galaxies is important for their bright X-ray tails and the intracluster star formation.Comment: ApJ in press, January 2010, v708, only several minor word changes, emulateapj5.sty, 24 pages, 11 color + 5 B/W figures (figure quality degraded) and 4 tables. The abstract has been abbreviated. A high-resolution PDF is available at: http://www.astro.virginia.edu/~ms4ar/eso137_p3.pd

Gaseous drag on a gravitational perturber in Modified Newtonian Dynamics and the structure of the wake

We calculate the structure of a wake generated by, and the dynamical friction force on, a gravitational perturber travelling through a gaseous medium of uniform density and constant background acceleration g_ext, in the context of Modified Newtonian Dynamics (MOND). The wake is described as a linear superposition of two terms. The dominant part displays the same structure as the wake generated in Newtonian gravity scaled up by a factor mu^{-1}(g_ext/a_0), where a_{0} is the constant MOND acceleration and mu the interpolating function. The structure of the second term depends greatly on the angle between g_{ext} and and the velocity of the perturber. We evaluate the dynamical drag force numerically and compare our MOND results with the Newtonian case. We mention the relevance of our calculations to orbit evolution of globular clusters and satellites in a gaseous proto-galaxy. Potential differences in the X-ray emission of gravitational galactic wakes in MOND and in Newtonian gravity with a dark halo are highlighted.Comment: 13 pages, 7 figures, accepted for publication in MNRA

A Method to Measure Positron Beam Polarization Using Optically Polarized Atoms

We outline an experimental technique for measuring the degree of polarization of a positron beam using an optically pumped, spin-polarized Rb target. The technique is based on the production and measurement of the ortho- and para-positronium fractions through positron collisions with the Rb atoms as a function of their polarization. Using realistic estimates for the cross sections and experimental parameters involved, we estimate that a polarization measurement with an uncertainty of 3% of the measured value can be achieved in an hou

Two-loop renormalization of gaugino masses in general supersymmetric gauge models

We calculate the two-loop renormalization group equations for the running gaugino masses in general SUSY gauge models, improving our previous result. We also study its consequence to the unification of the gaugino masses in the SUSY SU(5) model. The two-loop correction to the one-loop relation $m_i(\mu)\propto\alpha_i(\mu)$ is found to be of the order of a few \%.Comment: 8 pages + 1 figure (omitted),KEK-TH-371 / UT-65