3 research outputs found
Flavor Changing Neutral Currents involving Heavy Quarks with Four Generations
We study various FCNC involving heavy quarks in the Standard Model (SM) with
a sequential fourth generation. After imposing , and constraints, we find can be enhanced by an order of magnitude to ,
while decays can reach , which are orders of magnitude
higher than in SM. However,these rates are still not observable for the near
future.With the era of LHC approaching, we focus on FCNC decays involving
fourth generation and quarks. We calculate the rates for
loop induced FCNC decays , as well as
t^\prime\to tZ,\tH, tg, t\gamma. If is of order , tree level decay would dominate, posing a challenge
since -tagging is less effective. For ,
would tend to dominate, while could also open for heavier
, leading to thepossibility of quadruple- signals via . The FCNC decays could still dominate if
is just above 200 GeV. For the case of , ingeneral would be dominant, hence it behaves like a heavy top. For both and
, except for the intriguing light case, FCNC decays are in the
range, and are quite detectable at the LHC.For a possible
future ILC, we find the associated production of FCNC ,
are below sensitivity, while
and can be better probed.Tevatron Run-II can still probe the
lighter or scenario. LHC would either discover the fourth generation
and measure the FCNC rates, or rule out the fourth generation conclusively.Comment: 31 pages, 15 eps figures, version to appear in JHE