Search for Pair Production of First and Second Generation Leptoquarks in Proton-proton Collisions at $\sqrt{s}
Search for Pair Production of First and Second Generation Leptoquarks in Proton-proton Collisions at $\sqrt{s}

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Published: 2015

Total Pages: 48

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Our search for pair production of first and second generation leptoquarks is performed in final states containing either two charged leptons and two jets, or one charged lepton, one neutrino and two jets, using proton-proton collision data at √s = 8 TeV. The data, corresponding to an integrated luminosity of 19.7 fb-1, were recorded with the CMS detector at the LHC. First-generation scalar leptoquarks with masses less than 1010 (850) GeV are excluded for [beta] = 1.0 (0.5), where b is the branching fraction of a leptoquark decaying to a charged lepton and a quark. Similarly, secondgeneration scalar leptoquarks with masses less than 1080 (760) GeV are excluded for [beta] = 1.0 (0.5). Furthermore, mass limits are also set for vector leptoquark production scenarios with anomalous vector couplings, and for R-parity violating supersymmetric scenarios of top squark pair production resulting in similar final-state signatures. These are the most stringent limits placed on the masses of leptoquarks and RPV top squarks to date.

Search for Pair Production of Second Generation Scalar Leptoquarks in Ppbar Collisions at the Tevatron
Search for Pair Production of Second Generation Scalar Leptoquarks in Ppbar Collisions at the Tevatron

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Published: 2008

Total Pages: 126

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As predicted by numerous extensions of the Standard Model, leptoquarks (LQ) are hypothetical bosons allowing lepton-quark transitions. Under the assumption that they couple only to quarks and leptons of the same generation, three generations of leptoquarks can be distinguished. The search for the pair production of second generation scalar leptoquarks has been carried out in p{bar p} collisions at √s = 1.96TeV, using an integrated luminosity of 1 fb−1 collected by the D0 experiment at the Tevatron collider between August 2002 and February 2006. Topologies arising from the LQ{ovr LQ} → [mu]q[nu]q and LQ{ovr LQ} → [mu]q[mu]q decay modes have been investigated. In order to maximize the available statistics, a method for the combination of various prescaled triggers with an inclusive OR has been developed. Since no excess of data over the Standard Model prediction has been observed, upper limits on the leptoquark pair production cross section have been derived at 95% confidence level as function of the leptoquark mass and the branching fraction [beta] = Br(LQ → [mu]q), and are interpreted as lower limits on the leptoquark mass as function of [beta]. For [beta] = 1, [beta] = 1/2 and [beta] = 0.1, the combination of the two channels excludes scalar second generation leptoquarks with masses up to 309GeV, 262GeV, and 174GeV, respectively. The lower bounds on the scalar second generation leptoquark mass obtained for [beta] ≥ 0.1 are the best exclusion limits to date.

Search for Pair Production of Second Generation Scalar Leptoquarks in P Anti-p Collisions at S**1/2
Search for Pair Production of Second Generation Scalar Leptoquarks in P Anti-p Collisions at S**1/2

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Published: 2006

Total Pages: 8

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The authors report on a search for the pair production of second generation scalar leptoquarks (LQ2) in p{bar p} collisions at the center-of-mass energy √s = 1.96 TeV, using data corresponding to an integrated luminosity of 294 ± 19 pb−1 recorded with the D0 detector. No evidence for a leptoquark signal in the LQ2 {ovr LQ}2 → [mu]q[mu]q channel has been observed, and upper bounds on the product of cross section times branching fraction were set. This yields lower mass limits of m{sub LQ2} > 247 GeV for [beta] = [Beta](LQ{sub 2} → [mu]q) = 1 and m{sub LQ{sub 2}} > 182 GeV for [beta] = 1/2. Combining these limits with previous D0 results, the lower limits on the mass of a second generation scalar leptoquark are m{sub LQ{sub 2}} > 251 GeV and m{sub LQ{sub 2}} > 204 GeV for [beta] = 1 and [beta] = 1/2, respectively.

Search for Pair Production of Second Generation Scalar Leptoquarks
Search for Pair Production of Second Generation Scalar Leptoquarks

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Published: 2008

Total Pages: 11

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We report on a search for the pair production of second generation scalar leptoquarks (LQ) in p{bar p} collisions at the center of mass energy √s = 1.96TeV using a data set corresponding to an integrated luminosity of 1.0 fb−1 collected with the D0 experiment at the Fermilab Tevatron Collider. Topologies arising from the LQ{ovr LQ} → [mu]q[nu]q and LQ{ovr LQ} → [mu]q[mu]q decay modes are investigated. No excess of data over the standard model prediction is observed and upper limits on the leptoquark pair production cross section are derived at the 95% C.L. as a function of the leptoquark mass and the branching fraction [beta] for the decay LQ → [mu]q. These are interpreted as lower limits on the leptoquark mass as a function of [beta]. For [beta] = 1 (0.5), scalar second generation leptoquarks with masses up to 316GeV (270GeV) are excluded.

Search for First Generation Scalar Leptoquarks in the Evjj Channel in Pp Collisions at Sqrt(s)
Search for First Generation Scalar Leptoquarks in the Evjj Channel in Pp Collisions at Sqrt(s)

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Published: 2011

Total Pages: 29

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A search for pair-production of first generation scalar leptoquarks is performed in the final state containing an electron, a neutrino, and at least two jets using proton-proton collision data at sqrt(s)=7 TeV. The data were collected by the CMS detector at the LHC, corresponding to an integrated luminosity of 36 inverse picobarns. The number of observed events is in good agreement with the predictions for standard model processes. Prior CMS results in the dielectron channel are combined with this electron+neutrino search. A 95% confidence level combined lower limit is set on the mass of a first generation scalar leptoquark at 340 GeV for beta=0.5, where beta is the branching fraction of the leptoquark to an electron and a quark. These results represent the most stringent direct limits to date for values of beta greater than 0.05.