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Book Search for Pair Production of First and Second Generation Leptoquarks in Proton proton Collisions at sqrt s

Download or read book Search for Pair Production of First and Second Generation Leptoquarks in Proton proton Collisions at sqrt s written by and published by . This book was released on 2015 with total page 48 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Book Search for Single Production of Scalar Leptoquarks in Proton proton Collisions at S

Download or read book Search for Single Production of Scalar Leptoquarks in Proton proton Collisions at S written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this paper, a search is presented for the production of both first- and second-generation scalar leptoquarks with a final state of either two electrons and one jet or two muons and one jet. The search is based on a data sample of proton-proton collisions at center-of-mass energy √s =8 TeV recorded with the CMS detector and corresponding to an integrated luminosity of 19.6 fb-1. Upper limits are set on both the first- and second-generation leptoquark production cross sections as functions of the leptoquark mass and the leptoquark couplings to a lepton and a quark. Results are compared with theoretical predictions to obtain lower limits on the leptoquark mass. At 95% confidence level, single production of first-generation leptoquarks with a coupling and branching fraction of 1.0 is excluded for masses below 1730 GeV, and second-generation leptoquarks with a coupling and branching fraction of 1.0 is excluded for masses below 530 GeV. Finally, these are the best overall limits on the production of first-generation leptoquarks to date.

Book Search for Pair Production of Third generation Scalar Leptoquarks and Top Squarks in Proton proton Collisions at arrow

Download or read book Search for Pair Production of Third generation Scalar Leptoquarks and Top Squarks in Proton proton Collisions at arrow written by and published by . This book was released on 2014 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for pair production of third-generation scalar leptoquarks and supersymmetric top quark partners, top squarks, in final states involving tau leptons and bottom quarks is presented. The search uses events from a data sample of proton-proton collisions corresponding to an integrated luminosity of 19.7 fb-1, collected with the CMS detector at the LHC with [arrow]" = 8 TeV. The number of observed events is found to be in agreement with the expected standard model background. Third-generation scalar leptoquarks with masses below 740 GeV are excluded at 95% confidence level, assuming a 100% branching fraction for the leptoquark decay to a tau lepton and a bottom quark. In addition, this mass limit applies directly to top squarks decaying via an R-parity violating coupling [lambda]'333. The search also considers a similar signature from top squarks undergoing a chargino-mediated decay involving the R-parity violating coupling [lambda]'3jk. Each top squark decays to a tau lepton, a bottom quark, and two light quarks. Top squarks in this model with masses below 580 GeV are excluded at 95% confidence level. The constraint on the leptoquark mass is the most stringent to date, and this is the first search for top squarks decaying via [lambda]'3jk.

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

Download or read book Search for First Generation Scalar Leptoquarks in the Evjj Channel in Pp Collisions at Sqrt s written by and published by . This book was released on 2011 with total page 29 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Book Search for Third Generation Scalar Leptoquarks in the T tau Channel in Proton Proton Collisions at sqrt s

Download or read book Search for Third Generation Scalar Leptoquarks in the T tau Channel in Proton Proton Collisions at sqrt s written by and published by . This book was released on 2015 with total page 41 pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for pair production of third-generation scalar leptoquarks decaying to top quark and $\tau$ lepton pairs is presented using proton-proton collision data at a center-of-mass energy of $\sqrt{s}$ = 8 TeV collected with the CMS detector at the LHC and corresponding to an integrated luminosity of 19.7 fb-1. The search is performed using events that contain an electron or a muon, a hadronically decaying $\tau$ lepton, and two or more jets. The observations are found to be consistent with the standard model predictions. Assuming that all leptoquarks decay to a top quark and a $\tau$ lepton, the existence of pair produced, charge -1/3, third-generation leptoquarks up to a mass of 685 GeV is excluded at 95% confidence level. This result constitutes the first direct limit for leptoquarks decaying into a top quark and a $\tau$ lepton, and may also be applied directly to the pair production of bottom squarks decaying predominantly via the R-parity violating coupling [lambda]' 333.

Book Search for Scalar Leptoquarks in Pp Collisions at sqrt s

Download or read book Search for Scalar Leptoquarks in Pp Collisions at sqrt s written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: An inclusive search for a new-physics signature of lepton-jet resonances has been performed by the ATLAS experiment. Scalar leptoquarks, pair-produced in pp collisions at $\sqrt{s}$ = 13 TeV at the large hadron collider, have been considered. An integrated luminosity of 3.2 fb-1, corresponding to the full 2015 dataset was used. First (second) generation leptoquarks were sought in events with two electrons (muons) and two or more jets. The observed event yield in each channel is consistent with Standard Model background expectations. The observed (expected) lower limits on the leptoquark mass at 95% confidence level are 1100 and 1050 GeV (1160 and 1040 GeV) for first and second generation leptoquarks, respectively, assuming a branching ratio into a charged lepton and a quark of 100%. Upper limits on the aforementioned branching ratio are also given as a function of leptoquark mass. In conclusion, compared with the results of earlier ATLAS searches, the sensitivity is increased for leptoquark masses above 860 GeV, and the observed exclusion limits confirm and extend the published results.

Book Search for Pair Production of First generation Leptoquarks in P Pbar Collisions at Sqrt s

Download or read book Search for Pair Production of First generation Leptoquarks in P Pbar Collisions at Sqrt s written by and published by . This book was released on 2009 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for pair production of first-generation leptoquarks (LQ) is performed with data collected by the D0 experiment in p{bar p} collisions at √s = 1.96 TeV at the Fermilab Tevatron Collider. In a sample of data corresponding to ≈ 1 fb−1 the search has been performed on the final states with two electrons and two jets or one electron, two jets and missing transverse energy. We find our data consistent with standard model expectations. The results are combined with those found in a previous analysis of events with two jets and missing transverse energy to obtain scalar LQ mass limits. We set 95% C.L. lower limits on a scalar LQ mass of 299 GeV, 284 GeV and 216 GeV for [beta] = 1, [beta] = 0.5 and [beta] = 0.02 respectively, where [beta] is the LQ branching ratio in the eq channel. This improves the results obtained with a lower luminosity sample from Run II of the Tevatron. Lower limits on vector LQ masses with different couplings from 357 GeV to 464 GeV for [beta] = 0.5 are also set using this analysis.

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

Download or read book Search for Pair Production of Second Generation Scalar Leptoquarks in Ppbar Collisions at the Tevatron written by and published by . This book was released on 2008 with total page 126 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Book Search for the Third generation Scalar Leptoquarks and Heavy Right handed Neutrinos in Final States with Two Tau Leptons and Two Jets in Proton proton Collisions at sqrt s

Download or read book Search for the Third generation Scalar Leptoquarks and Heavy Right handed Neutrinos in Final States with Two Tau Leptons and Two Jets in Proton proton Collisions at sqrt s written by and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A search is performed for third-generation scalar leptoquarks and heavy right-handed neutrinos in events containing one electron or muon, one hadronically decaying tau lepton, and at least two jets, using a $\sqrt{s}$=13 TeV pp collision data sample corresponding to an integrated luminosity of 12.9 inverse femtobarns collected with the CMS detector at the LHC in 2016. The number of observed events is found to be in agreement with the standard model prediction. A limit is set at 95% confidence level on the product of the leptoquark pair production cross section and beta squared where beta is the branching fraction of leptoquark decay to a tau lepton and a bottom quark. Assuming beta=1, third-generation leptoquarks with masses below 850 GeV are excluded at 95 % confidence level. An additional search based on the same event topology involves heavy right-handed neutrinos, N[R], and right-handed W bosons, W[R], arising in a left-right symmetric extension of the standard model. In this search, W[R] bosons are assumed to decay to a tau lepton and N[R] followed by the decay of the N[R] to a tau lepton and an off-shell W[R] boson. Assuming the mass of the right-handed neutrino to be half of the mass of the right-handed W boson, W[R] boson masses below 2.9 TeV are excluded at 95 % confidence level. These results improve on the limits from previous searches for third-generation leptoquarks and heavy right-handed neutrinos with tau leptons in the final state.

Book Search for Heavy Neutrinos Or Third generation Leptoquarks in Final States with Two Hadronically Decaying Tau Leptons and Two Jets in Proton proton Collisions at Sqrt s

Download or read book Search for Heavy Neutrinos Or Third generation Leptoquarks in Final States with Two Hadronically Decaying Tau Leptons and Two Jets in Proton proton Collisions at Sqrt s written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A search for new particles has been conducted using events with two high transverse momentum (pt) tau leptons that decay hadronically, at least two high-pt jets, and missing transverse energy from the tau lepton decays. The analysis is performed using data from proton-proton collisions, collected by the CMS experiment in 2015 at sqrt(s) = 13 TeV, corresponding to an integrated luminosity of 2.1 inverse femtobarns. The results are interpreted in two physics models. The first model involves heavy right-handed neutrinos, N[l] (l = e, mu, tau), and right-handed charged bosons, W[R], arising in a left-right symmetric extension of the standard model. Masses of the W[R] boson below 2.35 (1.63) TeV are excluded at 95% confidence level, assuming the N[tau] mass is 0.8 (0.2) times the mass of the W[R] boson and that only the N[tau] flavor contributes to the W[R] decay width. In the second model, pair production of third-generation scalar leptoquarks that decay into tau tau bb is considered. Third-generation scalar leptoquarks with masses below 740 GeV are excluded, assuming a 100% branching fraction for the leptoquark decay to a tau lepton and a bottom quark. This is the first search at hadron colliders for the third-generation Majorana neutrino, as well as the first search for third-generation leptoquarks in the final state with a pair of hadronically decaying tau leptons and jets.

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

Download or read book Search for Pair Production of Second Generation Scalar Leptoquarks in P Anti p Collisions at S 1 2 written by and published by . This book was released on 2006 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.