Effective-Field-Theory Approach to Top-Quark Production and Decay

We discuss new physics in top-quark interactions, using an effective field theory approach. We consider top-quark decay, single top production, and top-quark pair production. We identify 15 dimension-six operators that contribute to these processes, and we compute the deviation from the Standard Model induced by these operators. The results provide a systematic way of searching for (or obtaining bounds on) physics beyond the Standard Model.Comment: 24 pages, 12 figures; references added, typos correcte

Constraints on Non-standard Top Quark Couplings

We study non-standard top quark couplings in the effective field theory approach. All nine dimension-six operators that generate anomalous couplings between the electroweak gauge bosons and the third-generation quarks are included. We calculate their contributions at tree level and one loop to all major precision electroweak observables. The calculations are compared with data to obtain constraints on eight of these operators.Comment: 26 pages, 2 figure

Pengaruh Media Periklanan terhadap Pengambilan Keputusan Siswa Smu untuk Mendaftar di Universitas Kristen Maranatha: Sikap Konsumen sebagai Variabel Moderasi (Studi Kasus Siswa Smu di Bandung)

Advertising is one of the indicators to build a brand image in consumers' minds. Advertisingcan evolve through feedback or consumer attitudes toward advertising displayed and the brandimage the company itself. Consumer's acceptance or rejection of advertising will be veryinfluential on the goods or services offered. Advertising is used as a stimulus to bring the responsefrom consumers. Response referred in this research is the consumer attitude. In this case can beseen that the advertising is basically intended to build an customer's attitude (affective andcognitive). Purpose of this research is to view the relationship between the effectiveness ofpromotions that have been conducted Maranatha Christian University with purchasing decisionsof high school students in Bandung, which is moderated by consumer attitudes. The resultsobtained show that high school students' attitudes toward advertising and Maranatha ChristianUniversity itself have a good results as well as feelings of respondents toward advertising showsthat advertising is able to remind, made an impression and encouraging respondents to continuetheir education at Maranatha Christian University

Cosmic Mach Number as a Function of Overdensity and Galaxy Age

We carry out an extensive study of the cosmic Mach number (\mach) on scales of R=5, 10 and 20h^-1Mpc using an LCDM hydrodynamical simulation. We particularly put emphasis on the environmental dependence of \mach on overdensity, galaxy mass, and galaxy age. We start by discussing the difference in the resulting \mach according to different definitions of \mach and different methods of calculation. The simulated Mach numbers are slightly lower than the linear theory predictions even when a non-linear power spectrum was used in the calculation, reflecting the non-linear evolution in the simulation. We find that the observed \mach is higher than the simulated mean by more than 2-standard deviations, which suggests either that the Local Group is in a relatively low-density region or that the true value of \Omega_m is ~ 0.2, significantly lower than the simulated value of 0.37. We show from our simulation that the Mach number is a weakly decreasing function of overdensity. We also investigate the correlations between galaxy age, overdensity and \mach for two different samples of galaxies --- DWARFs and GIANTs. Older systems cluster in higher density regions with lower \mach, while younger ones tend to reside in lower density regions with larger \mach, as expected from the hierarchical structure formation scenario. However, for DWARFs, the correlation is weakened by the fact that some of the oldest DWARFs are left over in low-density regions during the structure formation history. For giant systems, one expects blue-selected samples to have higher \mach than red-selected ones. We briefly comment on the effect of the warm dark matter on the expected Mach number.Comment: 43 pages, including 15 figures. Accepted version in ApJ. Included correlation function of different samples of galaxies, and the cumulative number fraction distribution as a fcn. of overdensity. Reorganized figures and added some reference

Cosmic Microwave Background constraints of decaying dark matter particle properties

If a component of cosmological dark matter is made up of massive particles - such as sterile neutrinos - that decay with cosmological lifetime to emit photons, the reionization history of the universe would be affected, and cosmic microwave background anisotropies can be used to constrain such a decaying particle model of dark matter. The optical depth depends rather sensitively on the decaying dark matter particle mass m_{dm}, lifetime tau_{dm}, and the mass fraction of cold dark matter f that they account for in this model. Assuming that there are no other sources of reionization and using the WMAP 7-year data, we find that 250 eV < m_{dm} < 1 MeV, whereas 2.23*10^3 yr < tau_{dm} < 1.23*10^18 yr. The best fit values for m_{dm} and tau_{dm}/f are 17.3 keV and 2.03*10^16 yr respectively.Comment: 17 pages, 3 figure

Massive galaxies in cosmological simulations: UV-selected sample at redshift z=2

We study the properties of galaxies at z=2 in a Lambda CDM universe, using two different types of hydrodynamic simulation methods (Eulerian TVD and SPH) and a spectrophotometric analysis in the Un, G, R filter set. The simulated galaxies at z=2 satisfy the color-selection criteria proposed by Adelberger et al. (2004) when we assume Calzetti extinction with E(B-V)=0.15. We find that the number density of simulated galaxies brighter than R<25.5 at z=2 is about 2e-2 h^3/Mpc^3, roughly one order of magnitude larger than that of Lyman break galaxies at z=3. The most massive galaxies at z=2 have stellar masses >~1e11 Msun, and their observed-frame G-R colors lie in the range 0.0<G-R<1.0. They typically have been continuously forming stars with a rate exceeding 30 Msun/yr over a few Gyrs from z=10 to z=2, although the TVD simulation indicates a more sporadic star formation history than the SPH simulations. Of order half of their stellar mass was already assembled by z~4. The reddest massive galaxies at z=2 with G-R >= 1.0 and Mstar>1e10 Msun/h finished the build-up of their stellar mass by z~3. Interestingly, our study suggests that the majority of the most massive galaxies at z=2 should be detectable at rest-frame UV wavelengths, contrary to some recent claims made on the basis of near-IR studies of galaxies at the same epoch, provided the median extinction is less than E(B-V)<0.3. However, our results also suggest that the fraction of stellar mass contained in galaxies that pass the color-selection criteria could be as low as 50% of the total stellar mass in the Universe at z=2. Our simulations suggest that the missing stellar mass is contained in fainter (R>25.5) and intrinsically redder galaxies. Our results do not suggest that hierarchical galaxy formation fails to account for the massive galaxies at z>=1. (abridged)Comment: 35 pages, 11 figures. Submitted to ApJ. Error in AB magnitude calculation corrected. Higher resolution version available at http://cfa-www.harvard.edu/~knagamine/redgal.ps.g

Comparisons of Cosmological MHD Galaxy Cluster Simulations to Radio Observations

Radio observations of galaxy clusters show that there are $\mu$G magnetic fields permeating the intra-cluster medium (ICM), but it is hard to accurately constrain the strength and structure of the magnetic fields without the help of advanced computer simulations. We present qualitative comparisons of synthetic VLA observations of simulated galaxy clusters to radio observations of Faraday Rotation Measure (RM) and radio halos. The cluster formation is modeled using adaptive mesh refinement (AMR) magneto-hydrodynamic (MHD) simulations with the assumption that the initial magnetic fields are injected into the ICM by active galactic nuclei (AGNs) at high redshift. In addition to simulated clusters in Xu et al. (2010, 2011), we present a new simulation with magnetic field injections from multiple AGNs. We find that the cluster with multiple injection sources is magnetized to a similar level as in previous simulations with a single AGN. The RM profiles from simulated clusters, both $|RM|$ and the dispersion of RM ($\sigma_{RM}$), are consistent at a first-order with the radial distribution from observations. The correlations between the $\sigma_{RM}$ and X-ray surface brightness from simulations are in a broad agreement with the observations, although there is an indication that the simulated clusters could be slightly over-dense and less magnetized with respect to those in the observed sample. In addition, the simulated radio halos agree with the observed correlations between the radio power versus the cluster X-ray luminosity and between the radio power versus the radio halo size. These studies show that the cluster wide magnetic fields that originate from AGNs and are then amplified by the ICM turbulence (Xu et al. 2010) match observations of magnetic fields in galaxy clusters.Comment: Accepted for publication in Ap

Building galaxies by accretion and in-situ star formation

We examine galaxy formation in a cosmological AMR simulation, which includes two high resolution boxes, one centered on a 3 \times 10^14 M\odot cluster, and one centered on a void. We examine the evolution of 611 massive (M\ast > 10^10M\odot) galaxies. We find that the fraction of the final stellar mass which is accreted from other galaxies is between 15 and 40% and increases with stellar mass. The accreted fraction does not depend strongly on environment at a given stellar mass, but the galaxies in groups and cluster environments are older and underwent mergers earlier than galaxies in lower density environments. On average, the accreted stars are ~2.5 Gyrs older, and ~0.15 dex more metal poor than the stars formed in-situ. Accreted stellar material typically lies on the outskirts of galaxies; the average half-light radius of the accreted stars is 2.6 times larger than that of the in-situ stars. This leads to radial gradients in age and metallicity for massive galaxies, in qualitative agreement with observations. Massive galaxies grow by mergers at a rate of approximately 2.6% per Gyr. These mergers have a median (mass-weighted) mass ratio less than 0.26 \pm 0.21, with an absolute lower limit of 0.20, for galaxies with M\ast ~ 10^12 M\odot. This suggests that major mergers do not dominate in the accretion history of massive galaxies. All of these results agree qualitatively with results from SPH simulations by Oser et al. (2010, 2012).Comment: 18 pages, 12 figures, submitted to MNRA