This paper presents a search for the t-channel exchange of an R-parity violating scalar top quark ((t) over tilde) in the e(+/-)mu(-/+) continuum using 2.1 fb(-1) of data collected by the ATLAS ...detector in root s = 7 TeV pp collisions at the Large Hadron Collider. Data are found to be consistent with the expectation from the Standard Model backgrounds. Limits on R-parity-violating couplings at 95 % C.L. are calculated as a function of the scalar top mass (m((t) over tilde)). The upper limits on the production cross section for pp -> e mu X, through the t-channel exchange of a scalar top quark, ranges from 170 fb for m((t) over tilde) = 95 GeV to 30 fb for m((t) over tilde) = 1000 GeV.
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 s=7 ...TeV. The data were collected by the CMS detector at the LHC, corresponding to an integrated luminosity of 36 pb−1. 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 339 GeV for β=0.5, where β 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 β greater than 0.05.
The Large Hadron Collider (LHC) is at the frontier of collider physics today, probing new physics at unprecedented energy scales. Many theories of physics beyond the Standard Model seek to elucidate ...the underlying mechanism of electroweak symmetry breaking. Given their large Yukawa couplings to the Higgs boson, third generations quarks of the Standard Model, and especially the top quark, play a key role in such theories. Therefore, new particles predicted by these theories often couple preferentially to top and bottom quarks. The favoured coupling to third generation can also be used to explain recently observed flavour physics anomalies in the LHCb, Babar or Belle experiments. This article will review recent searches for new physics performed by the ATLAS and CMS experiments at the LHC, in final states containing top and bottom quarks. In particular, searches for vector-like quarks, leptoquarks, and heavy scalar and gauge bosons will be discussed.
Exotic Physics Signatures at CMS Kaur, Amandeep
Moscow University physics bulletin,
04/2022, Volume:
77, Issue:
2
Journal Article
Peer reviewed
Open access
The highlights of the latest results for the search for exotic physics signatures at the compact muon solenoid (CMS) experiment are presented. These include signatures for heavy mass resonances, ...long-lived particles and leptoquarks predicted by theories beyond the Standard Model (BSM).
The recent result from the E821 experiment at BNL on the anomalous magnetic moment of the muon shows a distinct discrepancy with the Standard Model predictions. We calculate the additional correction ...that the anomalous magnetic moment receives in a model with scalar leptoquarks. We find that such models can account for the deviation from the SM value even for small leptoquark couplings.
We report the results of a search for pair production of scalar bottom quarks ((b) over bar (1)) and scalar third-generation leptoquarks (LQ(3)) in 5.2 fb(-1) of p (p) over bar collisions at the D0 ...experiment of the Fermilab Tevatron Collider. Scalar bottom quarks are assumed to decay to a neutralino ((chi) over bar (1)(0)) and a b quark, and we set 95% C.L. lower limits on their production in the (m((b) over bar1), m((chi) over bar 10)) mass plane such as m((b) over bar1) > 247 GeV for m(<(chi)over) (bar>10) = 0 and m((chi) over bar 10) > 110 GeV for 160 m(<(b) over bar1) < 200 GeV. The leptoquarks are assumed to decay to a tau neutrino and a b quark, and we set a 95% C.L. lower limit of 247 GeV on the mass of a charge-1/3 third-generation scalar leptoquark.
A search for second and third generation scalar and vector leptoquarks produced in ep collisions via the lepton flavour violating processes ep→μX and ep→τX is performed by the H1 experiment at HERA. ...The full data sample taken at a centre-of-mass energy s=319 GeV is used for the analysis, corresponding to an integrated luminosity of 245 pb−1 of e+p and 166 pb−1 of e−p collision data. No evidence for the production of such leptoquarks is observed in the H1 data. Leptoquarks produced in e±p collisions with a coupling strength of λ=0.3 and decaying with the same coupling strength to a muon–quark pair or a tau–quark pair are excluded at 95% confidence level up to leptoquark masses of 712 GeV and 479 GeV, respectively.
The cross section of single vector leptoquark production in direct lepton-gluon interaction is calculated. In a model independent analysis an effective Lagrangian describing the most general C and P ...conserving coupling of the leptoquarks to gluons is considered. An analytical expression is derived for the cross section in the case of anomalous vector leptoquark couplings to the gluon field. The cross sections of inclusive production of (et)-, ( mu t)- and (tt)-type vector leptoquarks in ep and pp collisions due to direct lepton-gluon interaction are evaluated. Dependences of the cross sections on the anomalous couplings are investigated. The obtained results can be useful for studies at ep colliders and the LHC.
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