Search for Compositeness, Leptoquarks and Large Extra Dimensions in e-q and e+q Contact Interactions at HERA

Reference Juergen Scheins, talk presented at DIS 2000; C Niebuhr, talk presented at ICHEP 2000, April 2000
Document Conference paper
Figures  (1a)  (1b)  (2)  (3a)  (3b)  (4a)  (4b)  (5a)  (5b)  (6)  (chi2)  (qrad)
Contact Uli Martyn
Abstract Deep-inelastic $e^\pm p$ scattering at high momentum transfer $Q^2$ is used to search for $eq$ contact interactions associated to scales not directly accessible at HERA. The cross section measurements $ m d \sigma / m d Q^2$, corresponding to luminosities of $15.2~\pb^{-1}$ of $e^-p$ data and $81.5~\pb^{-1}$ of $e^+p$ data, are well described by the Standard Model and are analysed to set constraints on new phenomena. For conventional contact interactions lower bounds can be set on $eq$ compositeness scales $\Lambda^\pm$ at $1.6 - 9.2~\TeV$ and on leptoquarks with a ratio mass over coupling $M/\lambda$ of $0.3 - 1.7~\TeV$. A search for low scale gravitational effects through the exchange of Kaluza-Klein excitations of gravitons in models with large extra dimensions results in lower limits on the effective Planck scale $M_S$ of $0.63~\TeV$ and $0.93~\TeV$ for positive and negative coupling, respectively.
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