Generation Scalar Leptoquarks Research Articles

Search for Second Generation Leptoquark Pairs Decaying toμν+jetsinpp¯Collisions at√s=1.8TeV

We report on a search for second generation leptoquarks (LQ) produced in p (p) over bar collisions at root s = 1.8 TeV using the DO detector at Fermilab. Second generation leptoquarks are assumed to be produced in pairs and to decay to either mu. or nu and either a strange or a charm quark (q). Limits an placed on sigma(p (p) over bar --> LQ --> mu nu + jets) as a function of the mass of the leptoquark. For equal branching ratios to mu q and nu q, second generation scalar leptoquarks with a mass below 160 GeV/c(2), vector leptoquarks with anomalous minimal vector couplings with a mass below 240 GeV/c(2), and vector leptoquarks with Yang-Mills couplings with a mass below 290 GeV/c(2), are excluded at the 95% confidence level.

Search for First Generation Scalar Leptoquark Pairs inpp¯Collisions ats=1.8TeV

We have searched for first generation scalar leptoquark (LQ) pairs in the eν+jets channel using pp¯ collider data (∫Ldt≈115pb−1) collected by the D0 experiment at the Fermilab Tevatron during 1992–1996. The analysis yields no candidate events. We combine the results with those from the ee+jets and νν+jets channels to obtain 95% confidence level (C.L.) upper limits on the LQ pair production cross section as a function of mass and of β, the branching fraction to a charged lepton. Comparing with the next-to-leading order theory, we set 95% C.L. lower limits on the LQ mass of 225, 204, and 79GeV/c2 for β=1, 12, and 0, respectively.Received 30 October 1997DOI:https://doi.org/10.1103/PhysRevLett.80.2051©1998 American Physical Society

Signal and backgrounds for leptoquarks at the CERN LHC

We study the potentiality of the CERN Large Hadron Collider (LHC) to unravel the existence of first generation scalar leptoquarks. Working with the most general $SU(2)_L \otimes U(1)_Y$ invariant leptoquark interactions, we analyze in detail the signals and backgrounds that lead to a final state containing a pair $e^+e^-$ and jets. Our results indicate that a machine like the LHC will be able to discover leptoquarks with masses up to 2--3 TeV depending on their couplings.

Search for Scalar Leptoquark Pairs Decaying to Electrons and Jets inp¯pCollisions

We have searched for the pair production of first generation scalar leptoquarks in the $\mathrm{eejj}$ channel using the full data set $(123{\mathrm{pb}}^{\ensuremath{-}1})$ collected with the D0 detector at the Fermilab Tevatron during 1992--1996. We observe no candidates with an expected background of approximately 0.4 events. Comparing the experimental 95% confidence level upper limit to theoretical calculations of the cross section with the assumption of a 100% branching fraction of $\mathrm{eq}$, we set a lower limit on the mass of a first generation scalar leptoquark of $225\mathrm{GeV}{/c}^{2}$. The results of this analysis rule out the interpretation of the excess of high ${Q}^{2}$ events at DESY HERA as leptoquarks which decay exclusively to $\mathrm{eq}$.

Bounds on second generation scalar leptoquarks from the anomalous magnetic moment of the muon.

We calculate the contribution of second generation scalar leptoquarks to the anomalous magnetic moment of the muon (AMMM). In the near future, E-821 at Brookhaven will reduce the experimental error on this parameter to $\Delta a_\mu^{\rm exp}<4\times 10^{-10}$, an improvement of 20 over its current value. With this new experimental limit we obtain a lower mass limit of $m_{\Phi_L}>186$\ GeV for the second generation scalar leptoquark, when its Yukawa-like coupling $\lambda_{\Phi_L}$\ to quarks and leptons is taken to be of the order of the electroweak coupling $g_2$.

Second generation leptoquark search in pp-bar collisions at sqrt s=1.8 TeV.

We report on a search for second generation scalar leptoquarks with the DO detector at the Fermilab Tevatron pp¯ collider at s=1.8 TeV. This search is based on 12.7 pb−1 of data. Second generation leptoquarks are assumed to be produced in pairs and to decay into a muon and quark with branching ratio β or into a neutrino and quark with branching ratio 1−β. We obtain cross section times branching ratio limits as a function of leptoquark mass and set lower limits on the leptoquark mass at the 95% confidence level.Received 5 July 1995DOI:https://doi.org/10.1103/PhysRevLett.75.3618©1995 American Physical Society