Discovering the composite Higgs through the decay of a heavy fermion

A possible composite nature of the Higgs could be revealed at the early stage of the LHC, by analyzing the channels where the Higgs is produced from the decay of a heavy fermion. The Higgs production from a singly-produced heavy bottom, in particular, proves to be a promising channel. For a value \lambda=3 of the Higgs coupling to a heavy bottom, for example, we find that, considering a 125 GeV Higgs which decays into a pair of b-quarks, a discovery is possible at the 8 TeV LHC with 30 fb^{-1} if the heavy bottom is lighter than roughly 530 GeV (while an observation is possible for heavy bottom masses up to 650 GeV). Such a relatively light heavy bottom is realistic in composite Higgs models of the type considered and, up to now, experimentally allowed. At \sqrt{s}=14 TeV the LHC sensitivity on the channel increases significantly. With \lambda=3 a discovery can occur, with 100 fb^{-1}, for heavy bottom masses up to 1040 GeV. In the case the heavy bottom was as light as 500 GeV, the 14 TeV LHC would be sensitive to the measure of the \lambda\ coupling in basically the full range \lambda>1 predicted by the theory.Comment: 25 pp. v2: Minor changes. v3: Version accepted for publication in JHEP. v4: typos fixe

Single-top t-channel hadroproduction in the four-flavour scheme with POWHEG and aMC@NLO

We present results for the QCD next-to-leading order (NLO) calculation of single-top t-channel production in the 4-flavour scheme, interfaced to Parton Shower (PS) Monte Carlo programs according to the POWHEG and MC@NLO methods. Comparisons between the two methods, as well as with the corresponding process in the 5-flavour scheme are presented. For the first time results for typical kinematic distributions of the spectator-b jet are presented in an NLO+PS approach.Comment: 16+1 pages, 8 figures, matches version accepted for publication in JHE

Testing right-handed currents at the LHC

The CMS Collaboration has published two different searches for new physics that contain possible hints for excesses in $eejj$ and $e\nu jj$ final states. Interpreting those hints as a possible signal of a right-handed gauge boson $W_R$ with mass 2-2.5~TeV may have profound implications for our understanding of the gauge structure of nature and Grand Unification, the scalar sector accessible at the LHC, neutrino physics, and the baryon asymmetry of the Universe. We show that this interpretation is, indeed, consistent with all existing constraints. However, before making premature claims we propose a number of cross-checks at the LHC14 that could confirm or falsify this scenario. Those include searches for a $Z_R$ resonance and the related new scalar sector around 6-7~TeV. Additionally, large effects in top-quark spin-asymmetries in single top production are possible.Comment: Additional references include

Probing the W tb vertex structure in t-channel single-top-quark production and decay in pp collisions at s√=8 TeV with the ATLAS detector

To probe the W tb vertex structure, top-quark and W -boson polarisation observables are measured from t-channel single-top-quark events produced in proton-proton collisions at a centre-of-mass energy of 8 TeV. The dataset corresponds to an integrated luminosity of 20.2 fb−1, recorded with the ATLAS detector at the LHC. Selected events contain one isolated electron or muon, large missing transverse momentum and exactly two jets, with one of them identified as likely to contain a b-hadron. Stringent selection requirements are applied to discriminate t-channel single-top-quark events from background. The polarisation observables are extracted from asymmetries in angular distributions measured with respect to spin quantisation axes appropriately chosen for the top quark and the W boson. The asymmetry measurements are performed at parton level by correcting the observed angular distributions for detector effects and hadronisation after subtracting the background contributions. The measured top-quark and W -boson polarisation values are in agreement with the Standard Model predictions. Limits on the imaginary part of the anomalous coupling gR are also set from model-independent measurements.We acknowledge the support of ANPCyT, Argentina; YerPhI, Armenia; ARC, Australia; BMWFW and FWF, Austria; ANAS, Azerbaijan; SSTC, Belarus; CNPq and FAPESP, Brazil; NSERC, NRC and CFI, Canada; CERN; CONICYT, Chile; CAS, MOST and NSFC, China; COLCIENCIAS, Colombia; MSMT CR, MPO CR and VSC CR, Czech Republic; DNRF and DNSRC, Denmark; IN2P3-CNRS, CEA-DSM/IRFU, France; SRNSF, Georgia; BMBF, HGF, and MPG, Germany; GSRT, Greece; RGC, Hong Kong SAR, China; ISF, I-CORE and Benoziyo Center, Israel; INFN, Italy; MEXT and JSPS, Japan; CNRST, Morocco; NWO, Netherlands; RCN, Norway; MNiSW and NCN, Poland; FCT, Portugal; MNE/IFA, Romania; MES of Russia and NRC KI, Russian Federation; JINR; MESTD, Serbia; MSSR, Slovakia; ARRS and MIZS, Slovenia; DST/NRF, South Africa; MINECO, Spain; SRC and Wallenberg Foundation, Sweden; SERI, SNSF and Cantons of Bern and Geneva, Switzerland; MOST, Taiwan; TAEK, Turkey; STFC, United Kingdom; DOE and NSF, United States of America. In addition, individual groups and members have received support from BCKDF, the Canada Council, CANARIE, CRC, Compute Canada, FQRNT, and the Ontario Innovation Trust, Canada; EPLANET, ERC, ERDF, FP7, Horizon 2020 and Marie Sklodowska-Curie Actions, European Union; Investissements d'Avenir Labex and Idex, ANR, Region Auvergne and Fondation Partager le Savoir, France; DFG and AvH Foundation, Germany; Herakleitos, Thales and Aristeia programmes co-financed by EU-ESF and the Greek NSRF; BSF, GIF and Minerva, Israel; BRF, Norway; CERCA Programme Generalitat de Catalunya, Generalitat Valenciana, Spain; the Royal Society and Leverhulme Trust, United Kingdom.The crucial computing support from all WLCG partners is acknowledged gratefully, in particular from CERN, the ATLAS Tier-1 facilities at TRIUMF (Canada), NDGF (Denmark, Norway, Sweden), CC-IN2P3 (France), KIT/GridKA (Germany), INFN-CNAF (Italy), NL-T1 (Netherlands), PIC (Spain), ASGC (Taiwan), RAL (UK) and BNL (USA), the Tier-2 facilities worldwide and large non-WLCG resource providers. Major contributors of computing resoinfo:eu-repo/semantics/publishedVersio

ν\nu-Two Higgs Doublet Model and its Collider Phenomenology

Smallness of neutrino masses can be explained by introducing a tiny vacuum expectation value of an extra-Higgs doublet which couples to right-handed neutrinos ($N_R$). This situation is naturally realized in $\nu$-Two Higgs Doublet Model ($\nu$THDM), where a TeV-scale seesaw mechanism can work well. We investigate observable phenomenology of $\nu$THDM at LHC and ILC experiments. Charged Higgs boson ($H^\pm$) in $\nu$THDM is almost originated from the extra-Higgs doublet and its coupling strength to neutrinos are not small. Then this model induces rich phenomenology at the LHC, for example, when $m_{H^\pm}^{} < M_N$, observable charged tracks can be induced from long lived charged Higgs. On the other hand, when $m_{H^\pm}^{} > M_N$, right-handed neutrinos can be long-lived, and secondary vertices may be tagged at the LHC. The $\nu$THDM also predicts observable lepton number violating process at the ILC.Comment: 17 pages, 27 eps file