QCD Instantons could be due to transitions from one
QCD vaccum to another ("tunnel" effect).
At HERA, this could lead to
events with high charged multiplicity, all flavors being
allowed in final state (u,d,c,s).
An MC Event Generator exists (QCDINS).
First studies have been carried out (results presented
e.g. at DIS97 conference).
This topic has not yet been adressed in WG80.
But seems interesting to be continued !
These could appear in Left-Right Supersymmetric
Models (see Mohapatra, Senjanovic). An interesting
characteristics of H-- is that tey can couple
to a pair of like-sign leptons
(e-e-, mu-mu-, e-mu-)
At HERA, charged Higgs could be produced via :
/e+ => beam pipe
/
------------------
e- | e- \
| \ H--
|
| gamma
|
P |
------------------
------------------
followed e.g. by decay H-- -> e- e-
This would lead to signatures with 2 electrons and no
hadronic activity.
Cross-section does not seem to be too low...
No official H1/ZEUS publication on this topic.
MC Event Generator written some time ago by ZEUS people (?)
An Event generator (MAJOR) exists for HERA (written by Rathmans et al.) The cross-sections are higher with e- in initial state than with e+. Results presented by ZEUS (e.g. "Future Physics at HERA" workshop)