119212880
Effective field theory for Higgs boson plus jet production
We use an effective field theory (EFT) which includes all possible gluon-Higgs dimension-5 and dimension-7 operators to study Higgs boson plus jet production in next-to-leading order QCD. The EFT sheds light on the effect of a finite top quark mass as well as any Beyond-the-Standard Model (BSM) modifications of Higgs-gluon effective couplings. In the gluon channel, the accuracy of the heavy-top approximation for differential distributions arises from the non-interference between the helicity amplitudes of the G^3 h and G^2 h operators in the m_h < p_T limit at lowest order. One dimension-7 operator involving quark bilinears, however, contributes significantly at high p_T, and potentially offers a channel for seeing BSM effects. One-loop renormalization of these operators is determined, allowing resummation of large logarithms via renormalization group running. NLO numerical results at the LHC are presented, which include O(1/m_t^2) contributions in the SM limit.
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.
18630918
Higgs decays as a window into the dark sector
A light vector boson, Z_d, associated with a "dark sector" U(1)_d gauge group has been introduced to explain certain astrophysical observations as well as low energy laboratory anomalies. In such models, the Higgs boson may decay into X+Z_d, where X=Z, Z_d or \gamma. Here, we provide estimates of those decay rates as functions of the Z_d coupling through either mass-mixing (e.g. via an enlarged Higgs mechanism) or through heavy new fermion loops and examine the implied LHC phenomenology. Our studies focus on the higher m_{Z_d} case, > several GeV, where the rates are potentially measurable at the LHC, for interesting regions of parameter spaces, at a level complementary to low energy experimental searches for the Z_d. We also show how measurement of the Z_d polarization (longitudinal versus transverse) can be used to distinguish the physics underlying these rare decays.
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.
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.
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 .
16819006
The luminosity–metallicity relation in the local Universe from the 2dF Galaxy Redshift Survey
We investigate the Luminosity ‐ Metallicity (L Z) relation in the local universe (0 0.3) galaxies. Oxygen-to-hydrogen (O/H) abundance ratios are estimated using the ”strong-line” method, which relates the strength of following bright emission lines [O II] �3727, [O III] �5007, and H� (parametersR23 andO32)
53618836
Design drivers for a wide-field multi-object spectrograph for the William Herschel Telescope
Wide-field multi-object spectroscopy is a high priority for European astronomy over the next decade. Most 8-10m telescopes have a small field of view, making 4-m class telescopes a particularly attractive option for wide-field instruments. We present a science case and design drivers for a wide-field multi-object spectrograph (MOS) with integral field units for the 4.2-m William Herschel Telescope (WHT) on La Palma. The instrument intends to take advantage of a future prime-focus corrector and atmospheric-dispersion corrector (Agocs et al, this conf.) that will deliver a field of view 2 deg in diameter, with good throughput from 370 to 1,000 nm. The science programs cluster into three groups needing three different resolving powers R: (1) high-precision radial-velocities for Gaia-related Milky Way dynamics, cosmological redshift surveys, and galaxy evolution studies (R = 5,000), (2) galaxy disk velocity dispersions (R = 10,000) and (3) high-precision stellar element abundances for Milky Way archaeology (R = 20,000). The multiplex requirements of the different science cases range from a few hundred to a few thousand, and a range of fibre-positioner technologies are considered. Several options for the spectrograph are discussed, building in part on published design studies for E-ELT spectrographs. Indeed, a WHT MOS will not only efficiently deliver data for exploitation of important imaging surveys planned for the coming decade, but will also serve as a test-bed to optimize the design of MOS instruments for the future E-ELT.
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.