Speaker
Description
We propose a direct measurement of the CKM element Vtd at the LHC. Taking profit of the imbalance between d and d¯ quark content in the proton, we show that a non-zero Vtd induces a charge asymmetry in the tW associated production. The main backgrounds to this process, tt¯ production, and tW associated production mediated by Vtb, give charge symmetric contributions at leading order in QCD. Therefore, using specific kinematic features of the signal, we construct a charge asymmetry in the di-lepton final state which, due also to a reduction of systematic uncertainties in the asymmetry, is potentially sensitive to Vtd suppressed effects. In particular, using signal and background simulations up to detector level, we show that this new observable could improve the current direct upper bound on |Vtd| already with existing LHC data. We also project that |Vtd| values down to ∼10 times the Standard Model prediction could be probed in the high luminosity phase of the LHC.
