119125083
Light sfermion interplay in the 125 GeV MSSM Higgs production and decay at the LHC
A bstractWe study the effects from light sfermions on the lightest Higgs boson production and decay at the Large Hadron Collider (LHC) within the Minimal Supersymmetric Standard Model (MSSM). We find that the scenario with light coloured sfermions — stops or sbottoms — has the potential to explain a non-universal alteration, as hinted by LHC data, of the gluon-gluon Fusion (μggF) with respect to the Vector Boson Fusion (μVBF) event rates and, in particular, can predict $ \frac{{{\mu_{\mathrm{VBF}}}}}{{{\mu_{ggF }}}} $ > 1 for all Higgs boson decay channels in ggF large areas of the parameter space.We also find that the scenario with a light stop/sbottom can be complemented by the scenario in which the total Higgs width, Γtot, is reduced due to a suppressed Yukawa coupling Yb. In this case, the reduction of the Higgs production rates in the ggF process which occurs in the maximal mixing scenario is compensated by the reduction of the H → $ b\overline{b} $ partial decay width, the largest component of Γtot.Furthermore, we highlight the fact that, in the light stop/sbottom scenario, event rates with the Higgs boson decaying to a $ b\overline{b} $ final state are predicted to be essentially below unity, especially in case of ggF, which is doubly suppressed, at production, due to the negative interference from stop/sbottom loops, as well at decay level, due to the Yb suppression. Therefore, during the future LHC runs, the measurement of h → $ b\overline{b} $ final states is a matter of special importance, which will offer additional handles to pin down the possible MSSM structure of the Higgs sector.Amongst all viable MSSM configurations that we study (including revisiting a light stau solution), we emphasise most the scenario with a light stop, as the latter is also motivated by Dark Matter and Electro-Weak baryogenesis. We also perform fits of the MSSM against the LHC data for all scenarios which we introduce, emphasising the fact that in most cases these are better than for the SM.
4979096
Multiple Higgs and vector boson production beyond the Standard Model
A bstractIf the electroweak symmetry breaking is originated from a strongly coupled sector, as for instance in composite Higgs models, the Higgs boson couplings can deviate from their Standard Model values. In such cases, at sufficiently high energies there could occur an onset of multiple Higgs boson and longitudinally polarised electroweak gauge boson (VL) production. We study the sensitivity to anomalous Higgs couplings in inelastic processes with 3 and 4 particles (either Higgs bosons or VL’s) in the final state. We show that, due to the more severe cancellations in the corresponding amplitudes as compared to the usual 2 → 2 processes, large enhancements with respect to the Standard Model can arise even for small modifications of the Higgs couplings. In particular, we find that triple Higgs production provides the best multiparticle channel to look for these deviations. We briefly explore the consequences of multiparticle production at the LHC.
119851484
Energy loss of high energy quarks and gluons in the quark-gluon plasma
Abstract A complete leading order expression for the collisional energy loss of a heavy quark in a quark-gluon plasma at high temperatures is presented. Including screening effects by using an effective perturbation theory proposed by Braaten and Pisarski, a gauge independent and infrared finite result is obtained. Estimates for the collisional and radiative energy loss of light quarks and gluons are given. Implications for jet quenching as a signal for a quark-gluon plasma formation in ultrarelativistic heavy ion collisions at RHIC and LHC are discussed.