What Does the CMS Measurement of W-polarization Tell Us about the Underlying Theory of the Coupling of W-Bosons to Matter?

We discuss results of the CMS collaboration on the sensitivity of the LHC to $W$ boson polarisation in the process $pp\to W^\pm + jet \to e^\pm jet+\not\!\!P_T$ using the $L_P$ variable directly connected to $\theta^*$ angle of the outgoing lepton in the rest frame of the decaying $W$. We have shown that for a given $L_P$, interference between different polarizations of the $W$-boson is not negligible, and needs to be taken into account when considering the differential cross-section with respect to $L_P$. The $L_P$ variable suggested by CMS collaboration is highly suitable variable to study LHC sensitivity to $g_V,g_A$ couplings of $W$-boson to fermions. We note that the experimental sensitivity to W-boson polarization which is much higher than that to ($g_V,g_A$) parameter space can be turned around and used to identify deviations from the Standard Model as a signal for new physics at the LHC.Comment: 11 pages, 8 figures. Updated to match the final version published in JHEP with updated figures and polished tex

Relic density of neutralinos in minimal supergravity

We evaluate the relic density of neutralinos in the minimal supergravity (mSUGRA) model. All 2->2 neutralino annihilation diagrams, as well as all initial states involving sleptons, charginos, neutralinos and third generation squarks are included. Relativistic thermal averaging of the velocity times cross sections is performed. We find that co-annihilation effects are only important on the edges of the model parameter space, where some amount of fine-tuning is necessary to obtain a reasonable relic density. Alternatively, at high tan(beta), annihilation through the broad Higgs resonances gives rise to an acceptable neutralino relic density over broad regions of parameter space where little or no fine-tuning is needed.Comment: LaTeX, 10 pages. Talk given by Alexander Belyaev at SUSY'02, "The 10th International Conference on Supersymmetry and Unification of Fundamental Interactions", DESY, Hamburg, Germany, 17-23 June 200

Light sfermion interplay in the 125 GeV MSSM Higgs production and decay at the LHC

We 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 ($\mu_{ggF}$) with respect to the Vector Boson Fusion ($\mu_{VBF}$) event rates and, in particular, can predict $\frac{\mu_{VBF}}{\mu_{ggF}}>1$ for all Higgs boson decay channels in 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, $\Gamma_{\rm tot}$, is reduced due to a suppressed Yukawa coupling $Y_b$. 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 $H\to b\bar{b}$ partial decay width, the largest component of $\Gamma_{\rm tot}$. Furthermore, we highlight the fact that, in the light stop/sbottom scenario, event rates with the Higgs boson decaying to a $b\bar{b}$ final state are predicted to be essentially below unity. Therefore, during the future LHC runs, the measurement of $h\to b\bar{b}$ final states is a matter of special importance. 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, emphasising the fact that in most cases these are better than for the SM.Comment: 25 page