This paper presents a search for the pair production of top squarks in events with a single isolated electron or muon, jets, large missing transverse momentum, and large transverse mass. The data sample corresponds to an integrated luminosity of 19.5 fb −1 of pp collisions collected in 2012 by the CMS experiment at the LHC at a center-of-mass energy of √ s = 8 TeV. No significant excess in data is observed above the expectation from standard model processes. The results are interpreted in the context of supersymmetric models with pair production of top squarks that decay either to a top quark and a neutralino or to a bottom quark and a chargino. For small mass values of the lightest supersymmetric particle, top-squark mass values up to around 650 GeV are excluded.Published in the European Physical Journal C as doi:10.1140/epjc/s10052-013-2677-2. IntroductionThe standard model (SM) has been extremely successful at describing particle physics phenomena. However, it suffers from such shortcomings as the hierarchy problem, where fine-tuned cancellations of large quantum corrections are required in order for the Higgs boson to have a mass at the electroweak symmetry breaking scale of order 100 GeV [1][2][3][4][5][6]. Supersymmetry (SUSY) is a popular extension of the SM that postulates the existence of a superpartner for every SM particle, with the same quantum numbers but differing by one half-unit of spin. SUSY potentially provides a "natural", i.e., not fine-tuned, solution to the hierarchy problem through the cancellations of the quadratic divergences of the top-quark and top-squark loops. In addition, it provides a connection to cosmology, with the lightest supersymmetric particle (LSP), if neutral and stable, serving as a dark matter candidate in R-parity conserving SUSY models. This paper describes a search for the pair production of top squarks using the full dataset collected at √ s = 8 TeV by the Compact Muon Solenoid (CMS) experiment [7] at the Large Hadron Collider (LHC) during 2012, corresponding to an integrated luminosity of 19.5 fb −1 . This search is motivated by the consideration that relatively light top squarks, with masses below around 1 TeV, are necessary if SUSY is to be the natural solution to the hierarchy problem [8][9][10][11][12]. These constraints are especially relevant given the recent discovery of a particle that closely resembles a Higgs boson, with a mass of ∼125 GeV [13][14][15]. Searches for top-squark pair production have also been performed by the ATLAS Collaboration at the LHC in several final states [16][17][18][19][20], and by the CDF [21] and D0 [22] Collaborations at the Tevatron.The search presented here focuses on two decay modes of the top squark ( t): t → t χ 0 1 and t → b χ + . These modes are expected to have large branching fractions if kinematically allowed. Here t and b are the top and bottom quarks, and the neutralinos ( χ 0 ) and charginos ( χ ± ) are the mass eigenstates formed by the linear combination of the gauginos and higgsinos, which are the fermi...

To clarify the outstanding problem in charmonium production that existing theories cannot explain the observed cross sections of cJ ðJ ¼ 0; 1; 2Þ and ratio R c ¼ c2 = c1 % 0:75 (in contrast to the spin counting value 5=3) at the Tevatron, we study the complete next-to-leading order radiative corrections in nonrelativistic QCD, and find next-to-leading order contributions of 3 P ½1 J are more important than leading order at high p T , and 3 P ½1 1 decreases slower than 3 P ½1 2 , implying a natural explanation for the R c puzzle. By fitting R c , the predicted cross sections of cJ are found to agree with data. The result indicates coloroctet contribution is crucially needed, thus providing a unique test for heavy quarkonium production mechanisms. Feed-down contributions of cJ to prompt J=c production are estimated to be substantial, about 30%-40% at p T ¼ 20 GeV. Production of cJ ðJ ¼ 0; 1; 2Þ at the LHC is also predicted.

A search for new resonances decaying into a pair of jets is reported using the dataset of proton-proton collisions recorded at √ s = 13 TeV with the ATLAS detector at the Large Hadron Collider between 2015 and 2018, corresponding to an integrated luminosity of 139 fb −1. The distribution of the invariant mass of the two leading jets is examined for local excesses above a data-derived estimate of the Standard Model background. In addition to an inclusive dijet search, events with jets identified as containing b-hadrons are examined specifically. No significant excess of events above the smoothly falling background spectra is observed. The results are used to set cross-section upper limits at 95% confidence level on a range of new physics scenarios. Model-independent limits on Gaussian-shaped signals are also reported. The analysis looking at jets containing b-hadrons benefits from improvements in the jet flavour identification at high transverse momentum, which increases its sensitivity relative to the previous analysis beyond that expected from the higher integrated luminosity.

A measurement is presented of the relative prompt production rate of χc2 and χc1 with 4.6 fb−1 of data collected by the CMS experiment at the LHC in pp collisions at . The two states are measured via their radiative decays χc→J/ψ+γ, with the photon converting into an e+e− pair for J/ψ rapidity |y(J/ψ)|<1.0 and photon transverse momentum pT(γ)>0.5 GeV/c. The measurement is given for six intervals of pT(J/ψ) between 7 and 25 GeV/c. The results are compared to theoretical predictions.

Search for a light charged Higgs boson in top quark decays in pp collisions at √ s = 7 TeVThe CMS collaborationAbstract: Results are presented on a search for a light charged Higgs boson that can be produced in the decay of the top quark t → H + b and which, in turn, decays into τ + ν τ . The analysed data correspond to an integrated luminosity of about 2 fb −1 recorded in protonproton collisions at √ s = 7 TeV by the CMS experiment at the LHC. The search is sensitive to the decays of the top quark pairs tt → H ± W ∓ bb and tt → H ± H ∓ bb. Various final states have been studied separately, all requiring presence of a τ lepton from H + decays, missing transverse energy, and multiple jets. Upper limits on the branching fraction B(t → H + b) in the range of 2-4% are established for charged Higgs boson masses between 80 and 160 GeV, under the assumption that B(H + → τ + ν τ ) = 1.