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a large number of `` fundamental '' particles , as well as observable free parameters ( put by hand ) , in standard model ( sm ) indicate that it is not `` the end of story '' .
physics has met similar situation two times in the past : one is the periodic table of the elements which was clarified by rutherford s experiment later , the other is hadron inflation which has resulted in quark model .
this analogy implies the preonic structure of the sm fermions ( see @xcite and references therein ) .
the preonic models predict a zoo of new particles such as excited leptons and quarks , leptoquarks , leptogluons etc .
excited fermions and leptoquarks are widely discussed in literature and their searches are inseparable parts of future collider s physics programs .
unfortunately , leptogluons did not attract necessary attention , while they are predicted in all models with colored preons ( see , for example , @xcite , @xcite , @xcite , @xcite , @xcite , @xcite ) .
lower bound on leptogluon masses , @xmath2 gev , given in pdg @xcite reflects twenty years old tevatron results @xcite . as mentions in @xcite
d0 clearly exclude @xmath3 gev leptogluons and could naively place the constraint @xmath4 gev .
fifteen years old h1 results on color octet electron , @xmath5 , search @xcite has excluded the compositeness scale @xmath6 @xmath7tev for @xmath8 gev and @xmath6@xmath9 gev for @xmath10 gev .
the advantage of lepton - hadron colliders is the resonant production of leptogluons , whereas at hadron and lepton colliders they are produced in pairs .
the sole realistic way to tev scale in lepton - hadron collisions are presented by linac - ring type electron - proton colliders ( see reviews @xcite , @xcite , @xcite and references therein ) .
recently cern , ecfa and nupecc initiated the study on the lhc based ep colliders @xcite .
two options are considered for the large hadron electron collider ( lhec ) : the construction of new e - ring in the lhc tunnel @xcite or the construction of e - linac tangentially to the lhc @xcite , @xcite , @xcite .
it should be noted that energy of electrons in first option is limited by synchrotron radiation , whereas in second option energy of electrons can be increased by lengthening the linac .
tentative parameters for linac - ring options of the lhec are presented in the table 1 .
qcd explorer stage(s ) is mandatory : it will provide necessary information on pdf s for adequate interpretation of future lhc results and it will clarify qcd basics , as well .
the realization of the energy frontier stage(s ) will be determined by the lhc results on beyond the standard model ( bsm ) physics .
.tentative parameters of the lhec linac - ring options .
qcde and ef denotes qcd explorer and energy frontier , respectively . [
cols="^,^,^,^",options="header " , ]
it seems that qcd explorer stage(s ) of the lhec , together with providing necessary information on pdf s and qcd basics , could play essential role on the bsm physics , also .
concerning color octet electrons .
lhec / qcde-1 will cover @xmath11 mass up to o(@xmath12 gev ) , whereas lhec / qcde-2 will enlarge covered mass range up to o(@xmath13 gev ) .
the discovery of @xmath1 at this machine , simultaneously will determine compositeness scale .
for example , if @xmath14 gev lhec / qcde-2 with @xmath15 @xmath16 will be sensitive to @xmath17 up to @xmath18 tev .
authors are grateful to a. celikel and m. kantar for useful discussions .
this work is supported by tubitak in the framework of the bidep post - doctoral program and taek under the grant no cern - a5.h2.p1.01 - 11 .
in composite models with colored preons leptogluons ( @xmath0 ) has a same status with leptoquarks , excited leptons and quarks etc . we analyze resonant production of color octet electron ( @xmath1 ) at qcd explorer stage of the large hadron electron collider ( lhec ) . 
 it is shown that the @xmath1 discovery at the lhec simultaneously will determine the compositeness scale .