PHYS08200604017 Manimala Mitra - Homi Bhabha National Institute

• The other dominant decay channel for Σ ± decay is Σ ± → νH ± . The neutrino will
give missing energy while H ± will decay into H ± → W ± h 0 . The W ± could decay
hadronically giving 2 jets or leptonically giving either a τ-jet + missing energy
or e/µ lepton + missing energy. Since the lepton released in the Σ ± → l ± h 0 is
important both for understanding the flavor structure of the mixing matrix as well
as for tagging the channel in order to reduce the background, we consider first the
case where one of heavy charged fermion decays into a hard charged lepton and h 0
and the other into a neutrino and H ± . The most interesting channels in this case
turn out to be:
Σ + Σ − → l + h 0 H − ν → l + h 0 h 0 W − ν → 4b+l+2j+ ̸ p T ,
Σ + Σ − → l + h 0 H − ν → l + h 0 h 0 W − ν → 4b+l+τ+ ̸ p T ,
where for the former, the two h 0 (one from the Σ + decay and another from H −
decay) produce 4 b-jets, and the W − decays produce two hadronic jets. In the
latter channel, the W − decays into τν τ , producing a τ-jet. The effective crosssection
for the former channel is 26.88 fb, while that for the latter is 4.48 fb. The
effective cross-sections for the other channels with l + h 0 h 0 W − ν in the intermediate
states are given in Table 3.8. However, their cross-sections are smaller.
• Finally, both the charged heavy fermions could decay through the H ± ν mode. In
this case we have the following leading order possibilities:
Σ + Σ − → H + νH − ν → h 0 h 0 W + W − νν → 4b+4j+ ̸ p T ,
Σ + Σ − → H + νH − ν → h 0 h 0 W + W − νν → 4b+2j +l ′ + ̸ p T ,
Σ + Σ − → H + νH − ν → h 0 h 0 W + W − νν → 4b+2j +τ+ ̸ p T .
The mode Σ + Σ − → 4b+OSD ′ + ̸ p T , appearing at serial number 16 in Table 3.8
could have been easy to tag as it contains 4b-jets and pair of opposite sign dileptons
coming from W ± decay, and missing energy. However, the effective cross-section
for this channel is relatively low. Note that none of the channels with H + νH − ν in
their intermediate state have l in their final state. For these channels therefore, it
is impossible to say anything about the flavor structure of the model.
3.8.2 Σ ± Σ 0 decay
We give in Tables 3.9 and 3.10, the possible decay channels, final state configurations of
particles, and their corresponding effective cross-sections for the Σ ± Σ 0 production and
decays. For the leptons we follow the same convention for our notation as done for the
previous section.
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