Single top production at HERA and THERA

Abstract

We study the single top production mediated by flavor changing neutral current via both of the t − q − γ and t − q − Z vertices (here q represents c and u quarks) in ep collisions at two colliders HERA and THERA. Contribution of the second vertex becomes even more important as the couplings take more improved values provided by the higher luminosities of colliders. In addition to these improvements if the CM energy of the collider is increased, the production will be dominated by the anomalous t − q − Z vertex.

Probe anomalous tqγ couplings through single top photoproduction at the LHC

“…We find that for the typical detector acceptance 0.0015 < ξ 1 < 0.5 and 0.0015 < ξ 3 photoproduction processes pp → pγp → pW(→ ℓν ℓ )b and pp → pγp → pW(→ ℓν ℓ )bj, both channels can be used to test the anomalous tqγ couplings. These parameter limits (bounds) are also comparable with the other phenomenological studies [26,27,28,41,95,96] and much better than the constraints from experiments [78,79,80,83]. Notice that in Fig.9 and Fig.10, we also present the bounds obtained when the luminosity become larger than 200fb −1 , see, up to 1000fb −1 .…”

“…lower bounds for the anomalous tqγ couplings κ both channels can be used to test the anomalous tqγ couplings. These parameter limits (bounds) are also comparable with the other phenomenological studies [26,27,28,41,95,96] and much better than the constraints from experiments [78,79,80,83]. Notice that in Fig.…”

“…In addition to the direct top quark decays, production of top quarks by FCNC interactions can also be used to probe such vertices. Studies have been presented at linear colliders [18,19,20,21,22,23,24], lepton-hadron colliders [25,26,27,28], as well as hadron colliders [24,29,30,31,32,33,34,35,36,37,38,39,40], see also reference there in. In this paper, we study the tqγ anomalous couplings through the leading single top photoproduction and single top jet associated photoproduction via the main reaction pp → pγp → pt → pW(→ ℓν ℓ )b + X and pp → pγp → ptj → pW(→ ℓν ℓ )bj + X assuming a typical LHC multipurpose forward detectors in a model independent effective lagrangian approach.…”

Anomalous production of fourth-family up-quarks at future lepton hadron colliders

“…The kinematics of this process is same as that of the single top quark production via FCNC interactions, which was presented in one of our earlier works [17]. Here, we present the total production cross sections as functions of u 4 mass in Fig.…”

Single top or bottom production associated with a scalar inγpcollision as a probe of topcolor-assisted technicolor

“…The limiting values are x 1,max = 0.83 in order to get rid of the background effects in the Compton backscattering, particularly e + e − pair production in the collision of the laser with the high energy photon in the conversion region, x 1,min = 0, x 2,max = 1, x 2,min = τ 0.83 , s min = (m q + M π ) 2 /s. Then we can write the total cross-section as [18,19] :…”