17463150
T-odd asymmetries in radiative top-quark decays
We study the angular distribution of the charged lepton in the top-quark decay into a bottom quark and a W boson which subsequently decays into lνl, when a hard gluon is radiated off. The absorptive part of the t → bWg decay amplitudes, which gives rise to T-odd asymmetries in the distribution, is calculated at the one-loop level in perturbative QCD. The asymmetries at a few percent level are predicted, which may be observable at future colliders.
14210683
The decay of tau leptons produced in neutrino–nucleon scatterings
Abstract Energy and angular distributions of the τ decay products in the CERN-to-Gran Sasso ν τ appearance experiments are studied for the decay modes τ → π ν and τ → l ν ¯ ν ( l = e or μ ). We find that the decay particle distributions in the laboratory frame are significantly affected by the τ polarization. Rather strong azimuthal asymmetry of π − and l − about the τ momentum axis is predicted, which may have observable consequences even at small statistics experiments.
17215723
Higgs characterisation via vector-boson fusion and associated production: NLO and parton-shower effects
Vector-boson fusion and associated production at the LHC can provide key information on the strength and structure of the Higgs couplings to the Standard Model particles. Using an effective field theory approach, we study the effects of next-to-leading order (NLO) QCD corrections matched to a parton shower on selected observables for various spin-0 hypotheses. We find that inclusion of NLO corrections is needed to reduce the theoretical uncertainties on the total rates as well as to reliably predict the shapes of the distributions. Our results are obtained in a fully automatic way via FeynRules and MadGraph5_aMC@NLO.
18756329
Higgs characterisation at NLO in QCD: CP properties of the top-quark Yukawa interaction
At the LHC the CP properties of the top-quark Yukawa interaction can be probed through Higgs production in gluon fusion or in association with top quarks. We consider the possibility for both CP-even and CP-odd couplings to the top quark to be present, and study CP-sensitive observables at next-to-leading order (NLO) in QCD, including parton-shower effects. We show that the inclusion of NLO corrections sizeably reduces the theoretical uncertainties, and confirm that di-jet correlations in $$H+2$$H+2 jet production through gluon fusion and correlations of the top-quark decay products in $$t\bar{t}H$$tt¯H production can provide sensitive probes of the CP nature of the Higgs interactions.
119237448
Monophoton signals in light gravitino production at $$e^+ e^-$$e+e- colliders
We revisit the monophoton plus missing energy signature at $$e^+e^-$$e+e- colliders in supersymmetric (SUSY) models where the gravitino is very light. There are two possible processes which provide the signal: gravitino pair production and associated gravitino production with a neutralino, leading the monophoton final state via an additional photon radiation and via the neutralino decay, respectively. By using the superspace formalism, we construct a model that allows us to study the parameter space for the both processes. We show that the signal cross section and the photon spectra provide information on the masses of the SUSY particles as well as the SUSY breaking scale.
60626146
ILC Reference Design Report: ILC Global Design Effort and World Wide Study
117769943
An H-alpha search for over-dense regions at z=2.23
We present the results of a narrow-band (H2S1, 2.121/0.021um) imaging search with WFCAM/UKIRT for H-alpha emitters around several potential signposts of rare (10^-7-10^-8 Mpc^-3) over-dense regions at z=2.23: an over-density of QSOs (2QZ cluster), a powerful, high-redshift radio galaxy (HzRG), and a concentration of submillimetre galaxies (SMGs) and optically faint radio galaxies (OFRGs). In total, we detect 137 narrow-band emitter candidates down to emission-line fluxes of 0.5-1 x 10^-16 erg s^-1 cm^-2, across a total area of 0.56 sq. degrees (2.1 x 10^5 comoving Mpc at z=2.23) in these fields. The BzK colours of the emitters suggest that at least 80% of our sample are likely to be H-alpha emitters (HAEs) at z=2.23. This is one of the largest HAE samples known at z>2. We find modest (~3-sigma) local over-densities of emitters associated with all the three targets. In the 2QZ cluster field, the emitters show a striking filamentary structure connecting four of the z=2.23 QSOs extending over 30Mpc (comoving). In the HzRG and SMG/OFRG fields, the structures appear to be smaller and seen only in the vicinities of the targets. The K-band magnitudes and the H-alpha equivalent widths of the emitters are weakly correlated with the over-density of the emitters: emitters in over-dense region are more evolved systems compared to those in under-dense regions at z=2.23. We find several examples of extended HAEs in our target fields, including a striking example with a spatial extent of 7.5 arcsec (60 kpc at z=2.23) in the 2QZ field, suggesting that these are relatively common in high-density regions. We conclude that narrow-band H-alpha surveys are efficient routes to map over-dense regions at high-z and thus to understand the relation between the growth of galaxies and their surrounding large-scale structures.