Search for first generation leptoquark pair production in the electron + missing energy + jets final state

We present a search for the pair production of first generation scalar leptoquarks ($LQ$) in data corresponding to an integrated luminosity of $5.4{\mathrm{fb}}^{-1}$ collected with the D0 detector at the Fermilab Tevatron Collider in $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$. In the channel $LQLQ\to eq{\nu }_e{q}^{\prime }$, where $q$, $q^{\prime }$ are $u$ or $d$ quarks, no significant excess of data over background is observed, and we set a 95% C.L. lower limit of 326 GeV on the $LQ$ mass, assuming equal probabilities of $LQ$ decays to $eq$ and ${\nu }_e{q}^{\prime }$.

Figure 1

(a) $M_T^{e\nu }$ distribution after preselection, (b) $\sum _{}^{}{M}_{LQ}$ for $M_T^{e\nu }>110\mathrm{GeV}$, (c) the $S_T$ for $M_T^{e\nu }>110\mathrm{GeV}$ and $\sum _{}^{}{M}_{LQ}>350\mathrm{GeV}$, which is used to set an upper limit on the $LQ$ pair production cross section after the final selection.

Figure 2

Expected and observed upper limits calculated at the 95% C.L. on the $LQ$ cross section as a function of $M_{LQ}$ for a scalar $LQ$ compared with the NLO prediction for $\beta =0.5$. The NLO cross section is shown for different choices of the renormalization and factorization scales, $\mu =M_{LQ}$, $\mu =0.5\times M_{LQ}$, and $\mu =2\times M_{LQ}$.

Figure 3

95% C.L. observed limit for $\mu =M_{LQ}$ on the $LQ$ mass as a function of $\beta$ compared with the previous D0 result [16], and CMS [17, 18] and ATLAS [19] results.