HELAS and MadGraph with spin-3/2 particles
Fortran subroutines to calculate helicity amplitudes with massive spin-3/2 particles, such as massive gravitinos, which couple to the standard model and supersymmetric particles via the supercurrent, are added to the HELAS (HELicity Amplitude Subroutines) library. They are coded in such a way that arbitrary amplitudes with external gravitinos can be generated automatically by MadGraph, after slight modifications. All the codes have been tested carefully by making use of the gauge invariance of the helicity amplitudes.

title: Probing top-philic sgluons with LHC Run I data
abstract: Many theories beyond the Standard Model predict the existence of colored scalar states, known as sgluons, lying in the adjoint representation of the QCD gauge group. In scenarios where they are top-philic, sgluons are expected to be copiously pair-produced at the LHC via strong interactions with decays into pairs of top quarks or gluons. Consequently, sgluons can be sought in multijet and multitop events at the LHC. We revisit two LHC Run I analyses in which events featuring either the same-sign dileptonic decay of a four-top-quark system or its single leptonic decay are probed. Adopting a simplified model approach, we show how this reinterpretation allows us to extract simultaneous bounds on the sgluon mass and couplings.

title: Multilepton signals of gauge mediated supersymmetry breaking at the LHC
abstract: We investigate multilepton LHC signals arising from electroweak processes involving sleptons. We consider the framework of general gauge mediated supersymmetry breaking, focusing on models where the low mass region of the superpartner spectrum consists of the three generations of charged sleptons and the nearly massless gravitino. We demonstrate how such models can provide an explanation for the anomalous four lepton events recently observed by the CMS Collaboration, while satisfying other existing experimental constraints. The best fit to the CMS data is obtained for a selectron/smuon mass of around 145 GeV and a stau mass of around 90 GeV. These models also give rise to final states with more than four leptons, offering alternative channels in which they can be probed and we estimate the corresponding production rates at the LHC.

title: Higgs characterisation via vector-boson fusion and associated production: NLO and parton-shower effects
abstract: 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.

title: Decay distribution of tau produced by neutrino-nucleon scattering☆
abstract: We studied the decay distributions of τ leptons produced in neutrino-nucleon scattering via charged current interaction, taking into account the τ polarization, for the long baseline neutrino oscillation experiments which aim to observe ν τ appearance. The information on the τ polarization is essential for measuring ν τ appearance since the decay particle distributions depend crucially on the τ spin. We show that τ produced via neutrino has high degree of polarization, and its spin direction depends non-trivially on the energy and the scattering angle of τ in the laboratory frame. We also show that the subsequent decay distributions are significantly affected by the produced τ polarization.

title: T-odd asymmetries in radiative top-quark decays
abstract: 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.

title: An H-alpha search for over-dense regions at z=2.23
abstract: 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.

title: CHARACTERIZATION OF THE DISTRIBUTION OF THE Lyα EMITTERS IN THE 53W002 FIELD AT z = 2.4*
abstract: We present the results of our wide-field narrowband imaging of the field around the radio galaxy 53W002 at z = 2.390 with Subaru/Suprime-Cam. A custom-made filter, NB413, centered at 4140 A with a width of 83 A is used to observe the 31' × 24' area around the radio galaxy. We detected 204 Lyα emitters (LAEs) at z = 2.4 with a rest-frame equivalent width larger than 25 A to the depth of 26 AB mag (in NB413). The entire LAE population in the 53W002 field has an average number density and distributions of equivalent width and size that are similar to those of other fields at z ~ 2. We identify a significant high-density region (53W002F-HDR) that spreads over ≈5' × 4' near 53W002, where the LAE number density is nearly four times as large as the average of the entire field. Using the probability distribution function of density fluctuation, we evaluate the rareness probability of 53W002F-HDR to be 0.9+2.4 – 0.62%, which corresponds to a moderately rich structure. No notable environmental dependency at the comoving scale of 10 Mpc is found for the distributions of the Lyα equivalent width and luminosity in the field. We also detected four Lyα blobs, one of which is newly discovered. They are all located in the rims of high-density regions. The biased location and unique morphologies in Lyα suggest that galaxy interaction plays a key role in their formation.