118862672
Technicolor-assisted leptogenesis with an ultra-heavy Higgs doublet
If fermion condensation is a main source of electroweak symmetry breaking, an ultra-heavy Higgs doublet of mass ~10^8 GeV can yield naturally small Dirac neutrino masses. We show that such a scenario can lead to a new leptogenesis mechanism based on the decays of the ultra-heavy Higgs. Given its very large mass, the requisite Higgs doublet can be considered an elementary particle and would point to a cutoff scale ~10^10 GeV. We outline how our scenario can also naturally lead to composite asymmetric dark matter. Some potential signals of this scenario are discussed.
116539757
Cosmological and Astrophysical Constraints on Tensor Unparticles
We calculate cosmological and astrophysical bounds on the couplings between standard model fields and tensor unparticles. The present day density of tensor unparticles from neutrino-neutrino and photon-photon annihilation is calculated. Also, the supernovae volume energy loss rates from electron-positron and photon-photon annihilation to tensor unparticles are calculated. The constraints from matter density and supernovae volume energy loss rates from photon-photon annihilation are on the same order of magnitude, while the bounds from supernovae volume energy loss rates from electron-positron annihilation are an order of magnitude lower. We find the couplings between standard model fields and tensor unparticles are at least an order of magnitude lower than those used for previous studies of tensor unparticle collider phenomenology.
5632236
Right-Handed Neutrinos as the Origin of the Electroweak Scale
The insular nature of the Standard Model may be explained if the Higgs mass parameter is only sensitive to quantum corrections from physical states. Starting from a scale-free electroweak sector at tree-level, we postulate that quantum effects of heavy right-handed neutrinos induce a mass term for a scalar weak doublet that contains the dark matter particle. In turn, below the scale of heavy neutrinos, the dark matter sector sets the scale of the Higgs potential. We show that this framework can lead to a Higgs mass that respects physical naturalness, while also providing a viable scalar dark matter candidate, realistic light neutrino masses, and the baryon asymmetry of the Universe via leptogenesis. The proposed scenario can remain perturbative and stable up to the Planck scale, thereby accommodating simple extensions to include a high scale (2\times 10^{16} GeV) inflationary sector, implied by recent measurements. In that case, our model typically predicts that the dark matter scalar is close to 1 TeV in mass and could be accessible in near future direct detection experiments.
18105043
Chiral couplings of W ′ and top quark polarization at the LHC
If a TeV-scale charged gauge boson (W') is discovered at the Large Hadron Collider (LHC), it will become imperative to determine its chiral couplings to standard model (SM) fermions in order to learn about the underlying theory containing the W'. We describe the reconstruction of the tb decay mode of the W' at the LHC, and identify various kinematic observables such as the angular distributions of the top quark and the lepton resulting from top decay that can be used to disentangle the chiral couplings of the W' to SM fermions. We demonstrate by presenting analytical expressions, numerical simulations, as well as intuitive illustrations for these observables at the LHC that among the SM fermions, the polarized top quark can most directly probe the chirality of such couplings.
15532687
QCD corrections to scalar diquark production at hadron colliders
We calculate the next-to-leading order QCD corrections to quark-quark annihilation to a scalar resonant state (“diquark”) in a color representation of antitriplet or sextet at the Tevatron and LHC energies. At the LHC, we find the enhancement (K-factor) for the antitriplet diquark is typically about 1.31–1.35, and for the sextet diquark is about 1.22–1.32 for initial-state valence quarks. The full transverse-momentum spectrum for the diquarks is also calculated at the LHC by performing the soft gluon resummation to the leading logarithm and all orders in the strong coupling.
119256327
Exploring resonant di-Higgs boson production in the Higgs singlet model
We study the enhancement of the di-Higgs production cross section resulting from the resonant decay of a heavy Higgs boson at hadron colliders in a model with a Higgs singlet. This enhancement of the double Higgs production rate is crucial in understanding the structure of the scalar potential and we determine the maximum allowed enhancement such that the electroweak minimum is a global minimum. The di-Higgs production enhancement can be as large as a factor of $\ensuremath{\sim}18(13)$ for the mass of the heavy Higgs around 270(420) GeV relative to the Standard Model rate at 14 TeV for parameters corresponding to a global electroweak minimum.
119116895
Black Hole Mass and Eddington Ratio Distribution Functions of X-Ray-selected Broad-line AGNs at z ~ 1.4 in the Subaru XMM-Newton Deep Field
In order to investigate the growth of supermassive black holes (SMBHs), we construct the black hole mass function (BHMF) and Eddington ratio distribution function (ERDF) of X-ray-selected broad-line active galactic nuclei (AGNs) at z {approx} 1.4 in the Subaru XMM-Newton Deep Survey (SXDS) field. A significant part of the accretion growth of SMBHs is thought to take place in this redshift range. Black hole masses of X-ray-selected broad-line AGNs are estimated using the width of the broad Mg II line and 3000 A monochromatic luminosity. We supplement the Mg II FWHM values with the H{alpha} FWHM obtained from our NIR spectroscopic survey. Using the black hole masses of broad-line AGNs at redshifts between 1.18 and 1.68, the binned broad-line AGN BHMFs and ERDFs are calculated using the V{sub max} method. To properly account for selection effects that impact the binned estimates, we derive the corrected broad-line AGN BHMFs and ERDFs by applying the maximum likelihood method, assuming that the ERDF is constant regardless of the black hole mass. We do not correct for the non-negligible uncertainties in virial BH mass estimates. If we compare the corrected broad-line AGN BHMF with that in the local universe, then the corrected BHMF atmore » z = 1.4 has a higher number density above 10{sup 8} M{sub Sun} but a lower number density below that mass range. The evolution may be indicative of a downsizing trend of accretion activity among the SMBH population. The evolution of broad-line AGN ERDFs from z = 1.4 to 0 indicates that the fraction of broad-line AGNs with accretion rates close to the Eddington limit is higher at higher redshifts.« less
119346714
Star Formation at Redshift One: Preliminary results from an H-alpha Survey
We present the first successful demonstration of multi-object near-infrared spectroscopy on high redshift galaxies. Our objective is to address the true star formation history of the universe at z~1, a crucial epoch which some have suggested is the peak of star formation activity. By using H-alpha -the same robust star formation indicator used at low-z - redshifted into the J- and H-bands, we can trace star formation without the systematic uncertainties of different calibrators, or the extreme dust extinction in the rest-UV, which have plagued previous efforts. We are using the instrument CIRPASS (the Cambridge Infra-Red PAnoramic Survey Spectrograph), in multi-object mode, which has been successfully demonstrated on the Anglo-Australian Telescope (AAT) and the William Herschel Telescope (WHT). CIRPASS has 150 fibres deployable over \~40arcmin on the AAT and ~15arcmin on the WHT. Here we present preliminary results from one of our fields observed with the WHT: H-alpha detections of z~1 galaxies in the Hubble Deep Field North.
34755903
The star formation rate at redshift one: Hα spectroscopy with CIRPASS
We have conducted an Ha survey of 38 0.77 ≤ z ≤ 1 galaxies over ∼100 arcmin 2 of the Hubble Deep Field-North and Flanking Fields, to determine star formation rates (SFRs), with the near-IR multi-object spectrograph Cambridge Infrared Panoramic Survey Spectrograph (CIRPASS) on the William Herschel Telescope (WHT). This represents the first successful application of this technique to observing high-redshift galaxies. Stacking the spectra in the rest frame to infer a total SFR for the field, we find a lower limit (uncorrected for dust reddening) on the SFR density at redshift z = 1 of 0.04 M ⊙ yr -1 Mpc -3 . This implies rapid evolution in the SFR density from z = 0 to 1 which is proportional to (1 + z) 3.1 .
118340513
The [OII]/Halpha ratio of emission line galaxies in the 2dF redshift survey
We investigate the systematic variation of the [OII]3727/Halpha flux line ratio as a function of various galaxy properties, i.e., luminosity, metallicity, reddening, and excitation state, for a sample of 1124 emission-line galaxies, with a mean redshift z ~ 0.06, drawn from the Two Degree Field Galaxy Redshift Survey. The mean observed and extinction-corrected emission-line flux ratios agree well with the values derived from the $B$-band selected Nearby Field Galaxy Survey galaxy sample, but are significantly different from the values obtained from the Halpha-selected Universidad Complutense de Madrid Survey galaxy sample. This is because the different selection criteria applied in these surveys lead to a significant difference in the mean extinction and metallicity of different samples. We use the R_{23} parameter to estimate the gas-phase oxygen abundance and find that the extinction-corrected [OII]3727/Halpha ratio depends on the oxygen abundance. For 12+log(O/H)>8.4, we confirm that the emission-line ratio decreases with increasing metallicity. We have extended the relationship further to the metal-poor regime, 12+log(O/H)< 8.4, and find that the correlation between the extinction-corrected [OII]3727/Halpha ratio and the metallicity reverses in comparison to the relationship for metal-rich galaxies. For metal-poor galaxies, in contrast with metal-rich ones, the variation of extinction-corrected [OII]3727/Halpha ratio is correlated with the ionization states of the interstellar gas.