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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.

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 Pair Production of Second Generation Scalar Leptoquarks

Download or read book Search for Pair Production of Second Generation Scalar Leptoquarks written by and published by . This book was released on 2008 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

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 Second generation Scalar Leptoquarks in P Anti p Collisions at S 1 2

Download or read book Search for Second generation Scalar Leptoquarks in P Anti p Collisions at S 1 2 written by and published by . This book was released on 2005 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: Results on a search for pair production of second generation scalar leptoquark in p{bar p} collisions at √s=1.96 TeV are reported. The data analyzed were collected by the CDF detector during the 2002-2003 Tevatron Run II and correspond to an integrated luminosity of 198 pb−1. Leptoquarks (LQ) are sought through their decay into (charged) leptons and quarks, with final state signatures represented by two muons and jets and one muon, large transverse missing energy and jets. We observe no evidence for LQ production and derive 95% C.L. upper limits on the LQ production cross sections as well as lower limits on their mass as a function of [beta], where [beta] is the branching fraction for LQ → [mu]q.

Book Search for Second generation Scalar Leptoquarks in P Anti p Collisions at S

Download or read book Search for Second generation Scalar Leptoquarks in P Anti p Collisions at S written by and published by . This book was released on 2005 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: Results on a search for pair production of second generation scalar leptoquark in p{bar p} collisions at √s=1.96 TeV are reported. The data analyzed were collected by the CDF detector during the 2002-2003 Tevatron Run II and correspond to an integrated luminosity of 198 pb−1. Leptoquarks (LQ) are sought through their decay into (charged) leptons and quarks, with final state signatures represented by two muons and jets and one muon, large transverse missing energy and jets. We observe no evidence for LQ production and derive 95% C.L. upper limits on the LQ production cross sections as well as lower limits on their mass as a function of?, where? is the branching fraction for LQ →?q.

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 The Search for the Pair Production of Second generation Scalar Leptoquarks and Measurements of the Differential Cross Sections of the W Boson Produced in Association with Jets with the CMS Detector at the LHC

Download or read book The Search for the Pair Production of Second generation Scalar Leptoquarks and Measurements of the Differential Cross Sections of the W Boson Produced in Association with Jets with the CMS Detector at the LHC written by Darin C. Baumgartel and published by . This book was released on 2014 with total page 217 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since the formulation of the Standard Model of particle physics, numerous experiments have sought to observe the signatures of the subatomic particles by examining the outcomes of charged particle collisions. Over time, advances in detector technology and scientific computing have allowed for unprecedented precision measurements of Standard Model phenomena and particle properties. Although the Standard Model has displayed remarkable predictive power, extensions to the Standard Model have been formulated to account for unexplained phenomena, and these extensions often infer the existence of additional subatomic particles. Consequently, experiments at particle colliders often endeavor to search for signatures of physics beyond the Standard Model. These searches and measurements are often complementary pursuits, as searches are often limited by the precision of estimations of the Standard Model backgrounds. At the forefront of present-day collider experiments is the Large Hadron Collider at CERN, which delivers proton-proton collisions with unprecedented energy and luminosity. Collisions are recorded with detectors located at interaction points along the ring of the Large Hadron Collider. The CMS detector is one of two general-purpose detectors at the Large Hadron Collider, and the high-precision detection of particles from collision events in the CMS detector make the CMS detector a powerful tool for both Standard-Model measurements and searches for new physics. The Standard Model is characterized by three generation of quarks and leptons. This correspondence between the generations of quarks and leptons is necessary to allow for the renormalizability of the Standard Model, but it is not an inherent property of the Standard Model. Motivated by this compelling symmetry, many theories and models propose the existence of leptoquark bosons which mediate transitions between quarks and leptons. Experimental constraints indicate that leptoquarks would couple to a single generation, and this thesis describes searches for leptoquarks produced in pairs and decaying to final states containing either two muons and two jets, or one muon, one muon-neutrino, and two jets. Searches are conducted with collision data at center-of-mass energies of both 7 TeV and 8 TeV. No compelling evidence for the existence of leptoquarks is found, and upper limits on the leptoquark mass and cross section are placed at the 95% confidence level. These limits are the most stringent to date, and are several times larger than limits placed previously at hadron collider experiments. While the pair production of massive leptoquark bosons yields final states which have strong kinematic differences from the Standard Model processes, the ability to exploit these differences is limited by the ability to accurately model the backgrounds. The most notable of these backgrounds is the production of a W boson in association with one or more jets. Since the W+jets process has a very large cross section and a final state containing missing energy, its contribution to the total Standard Model background is both nominally large and more difficult to discriminate against than backgrounds with only visible final state objects. Furthermore, estimates of this background are not easily improved by comparisons with data in control regions, and simulations of the background are often limited to leading-order predictions. To improve the understanding and modeling of this background for future endeavors, this thesis also presents measurements of the W+jets process differentially as a function of several variables, including the jet multiplicity, the individual jet transverse momenta and pseudorapidities, the angular separation between the jets and the muon, and the scalar sum of the transverse momenta of all jets. The agreement of these measurements with respect to predictions from event leading-order generators and next-to-leading-order calculations is assessed.

Book Search for First and Second Generation Leptoquarks at

Download or read book Search for First and Second Generation Leptoquarks at written by and published by . This book was released on 1995 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 First Generation Leptoquark Pair Production in the Electron Missing Energy Jets Final State

Download or read book Search for First Generation Leptoquark Pair Production in the Electron Missing Energy Jets Final State written by and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We present a search for the pair production of first generation scalar leptoquarks (LQ) in data corresponding to an integrated luminosity of 5.4 fb-1 collected with the D0 detector at the Fermilab Tevatron Collider in pp collisions at √s = 1.96 TeV. In the channel LQLQ → eq?eq, where q,q 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 leptoquark mass, assuming equal probabilities of leptoquark decays to eq and ?subesubq.