Associated production of the Higgs boson and a single top quark in the littlest Higgs model at Large Hadron Collier

Shuo Yang

Promblems in SM• No fundamental scalars observed in nature

• No explanation of dynamics responsible for EWSB

• Hierarachy Problem

• Trivality Problem

• Neutrino mass

• Dark matter

................................

Possible Solutions

• SUSY• Technicolor: TC2 ,top seesaw• Extra Dimensions: flat, wraped • Higgsless Model• Little Higgs

……

LHC May Tell Us what is the nature !

Little higgs modelsMotivation: hierarchy problemBasic Idea: higgs is a goldstone bosonMechanism: collective symmetry breaking

Littlest Higgs Model SU(5) SO(5) [ SU(2)X U(1) ] SU(2)X U(1)2

Collective symmetry breaking

If there is only g2. the original SU(5) is explicitly broken to SU(3)×SU(2)×U(1), where the SU(3) acts on the first three indices. In this limit, The Higgs doublet h shifts under part of the SU(3), and so it is forbidden from picking up a potential.The same symmetry argument applies when only g1

is turned on.

The fact tells us that even when all couplings are turned on, the Higgs does not receive quadratically divergent contributions to its mass-squared at one loop

The cancellation can also be understood in terms of the Lagrangian in gauge boson mass eignstates.

We find that in a large part of the parameter space the cross section of th production in s-channel and t-channel production can deviate largely from the SM prediction.

th production signal and background

Our signal is

Backgrounds

• We find that in a large part of the parameter space the cross section of th production in s-channel and t-channel production can deviate largely from the SM prediction.

• Different from the case in SM, in LH model both the cross sections in s-channel and t-channel are larger than that in W-associated process in a large part of the parameter space.

• We also consider the signal 4b + l + pt +1jet and backgrounds for the th production. It is found that with 75fb inverse of integrated luminosity, in the parameter space of C=0.8 and f<1.62, S/sqrt{B}>5 can be achieved