Single top and Higgs associated production as a probe of the $Ht\overline{t}$ coupling sign at the LHC

The LHC sensitivity to an anomalous Higgs coupling to the top quark in the Higgs-top associated production is analyzed. Thanks to the strong destructive interference in the t-channel for standard model couplings, this process can be very sensitive to both the magnitude and the sign of a nonstandard top-Higgs coupling. We analyze cross sections and the main irreducible backgrounds for the H\u2009\u2192\u2009\u3b3\u3b3 decay channel. Sensitivities to an anomalous sign for the top Yukawa coupling are found to be large. In particular, at s 1a=14TeV , assuming a universal rescaling in the Yukawa sector, a parton-level analysis with realistic selection cuts gives a signal-to-background ratio S/B\u2009~\u20095, for 121.5 72Yt/YSMt 720 . A number of events S\u2009 43\u200910 (with corresponding significances\u2009~\u20093 \u3c3) are expected for 60 fb 121, to be compared with the standard-model expectation S\u2009~\u20090.3