Pentaquark searches at FOCUS

We find no evidence for high-energy photoproduction of pentaquarks at 1540 MeV/$c^2$, 1862 MeV/$c^2$, or 3099 MeV/$c^2$ using decay modes $pK_S^0$, $\Xi^-\pi^-$, and $D^{(*)-}p$, respectively.Comment: Proceedings from talk at 2004 DPF Meeting at University of California, Riversid

Search for resonant production of strongly coupled dark matter in proton-proton collisions at 13 TeV

The first collider search for dark matter arising from a strongly coupled hidden sector is presented and uses a data sample corresponding to 138 fb&minus;1, collected with the CMS detector at the CERN LHC, at s&radic; = 13 TeV. The hidden sector is hypothesized to couple to the standard model (SM) via a heavy leptophobic Z&prime; mediator produced as a resonance in proton-proton collisions. The mediator decay results in two &ldquo;semivisible&rdquo; jets, containing both visible matter and invisible dark matter. The final state therefore includes moderate missing energy aligned with one of the jets, a signature ignored by most dark matter searches. No structure in the dijet transverse mass spectra compatible with the signal is observed. Assuming the Z&prime; boson has a universal coupling of 0.25 to the SM quarks, an inclusive search, relevant to any model that exhibits this kinematic behavior, excludes mediator masses of 1.5&ndash;4.0 TeV at 95% confidence level, depending on the other signal model parameters. To enhance the sensitivity of the search for this particular class of hidden sector models, a boosted decision tree (BDT) is trained using jet substructure variables to distinguish between semivisible jets and SM jets from background processes. When the BDT is employed to identify each jet in the dijet system as semivisible, the mediator mass exclusion increases to 5.1 TeV, for wider ranges of the other signal model parameters. These limits exclude a wide range of strongly coupled hidden sector models for the first time.</p

Study of quark and gluon jet substructure in Z plus jet and dijet events from pp collisions

Measurements of jet substructure describing the composition of quark- and gluon-initiated jets are presented. Proton-proton (pp) collision data at s&radic; = 13 TeV collected with the CMS detector are used, corresponding to an integrated luminosity of 35.9 fb&minus;1. Generalized angularities are measured that characterize the jet substructure and distinguish quark- and gluon-initiated jets. These observables are sensitive to the distributions of transverse momenta and angular distances within a jet. The analysis is performed using a data sample of dijet events enriched in gluon-initiated jets, and, for the first time, a Z+jet event sample enriched in quark-initiated jets. The observables are measured in bins of jet transverse momentum, and as a function of the jet radius parameter. Each measurement is repeated applying a &ldquo;soft drop&rdquo; grooming procedure that removes soft and large angle radiation from the jet. Using these measurements, the ability of various models to describe jet substructure is assessed, showing a clear need for improvements in Monte Carlo generators.</p

Search for long-lived particles produced in association with a Z boson in proton-proton collisions at root s=13 TeV

A search for long-lived particles (LLPs) produced in association with a Z boson is presented. The study is performed using data from proton-proton collisions with a center-of-mass energy of 13 TeV recorded by the CMS experiment during 2016&ndash;2018, corresponding to an integrated luminosity of 117 fb&minus;1. The LLPs are assumed to decay to a pair of standard model quarks that are identified as displaced jets within the CMS tracker system. Triggers and selections based on Z boson decays to electron or muon pairs improve the sensitivity to light LLPs (down to 15 GeV). This search provides sensitivity to beyond the standard model scenarios which predict LLPs produced in association with a Z boson. In particular, the results are interpreted in the context of exotic decays of the Higgs boson to a pair of scalar LLPs (H &rarr; SS). The Higgs boson decay branching fraction is constrained to values less than 6% for proper decay lengths of 10&ndash;100 mm and for LLP masses between 40 and 55 GeV. In the case of low-mass (&asymp; 15 GeV) scalar particles that subsequently decay to a pair of b quarks, the search is sensitive to branching fractions B(H &rarr; SS) &lt; 20% for proper decay lengths of 10&ndash;50 mm. The use of associated production with a Z boson increases the sensitivity to low-mass LLPs of this analysis with respect to gluon fusion searches. In the case of 15 GeV scalar LLPs, the improvement corresponds to a factor of 2 at a proper decay length of 30 mm.</p

Search for new physics in the lepton plus missing transverse momentum final state in proton-proton collisions at root s=13 TeV

A search for physics beyond the standard model (SM) in final states with an electron or muon and missing transverse momentum is presented. The analysis uses data from proton-proton collisions at a centre-of-mass energy of 13 TeV, collected with the CMS detector at the LHC in 2016&ndash;2018 and corresponding to an integrated luminosity of 138 fb&minus;1. No significant deviation from the SM prediction is observed. Model-independent limits are set on the production cross section of W&rsquo; bosons decaying into lepton-plus-neutrino final states. Within the framework of the sequential standard model, with the combined results from the electron and muon decay channels a W&rsquo; boson with mass less than 5.7 TeV is excluded at 95% confidence level. Results on a SM precision test, the determination of the oblique electroweak W parameter, are presented using LHC data for the first time. These results together with those from the direct W&rsquo; resonance search are used to extend existing constraints on composite Higgs scenarios. This is the first experimental exclusion on compositeness parameters using results from LHC data other than Higgs boson measurements. &nbsp;</p

Search for single production of a vector-like T quark decaying to a top quark and a Z boson in the final state with jets and missing transverse momentum at root

A search is presented for single production of a vector-like T quark with charge 2/3 e, in the decay channel featuring a top quark and a Z boson, with the top quark decaying hadronically and the Z boson decaying to neutrinos. The search uses data collected by the CMS experiment in proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 137 fb&minus;1 recorded at the CERN LHC in 2016&ndash;2018. The search is sensitive to a T quark mass between 0.6 and 1.8 TeV with decay widths ranging from negligibly small up to 30% of the T quark mass. Reconstruction strategies for the top quark are based on the degree of Lorentz boosting of its final state. At 95% confidence level, the upper limit on the product of the cross section and branching fraction for a T quark of small decay width varies between 15 and 602 fb, depending on its mass. For a T quark with decay widths between 10 and 30% of its mass, this upper limit ranges between 16 and 836 fb. For most of the studied range, the results provide the best limits to date. This is the first search for single T quark production based on the full Run 2 data set of the LHC. &nbsp;</p

Search for strongly interacting massive particles generating trackless jets in proton-proton collisions at root s=13 TeV

A search for dark matter in the form of strongly interacting massive particles (SIMPs) using the CMS detector at the LHC is presented. The SIMPs would be produced in pairs that manifest themselves as pairs of jets without tracks. The energy fraction of jets carried by charged particles is used as a key discriminator to suppress efficiently the large multijet background, and the remaining background is estimated directly from data. The search is performed using proton&ndash;proton collision data corresponding to an integrated luminosity of 16.1fb&minus;1, collected with the CMS detector in 2016. No significant excess of events is observed above the expected background. For the simplified dark matter model under consideration, SIMPs with masses up to 100GeV are excluded and further sensitivity is explored towards higher masses.</p

Search for supersymmetry in final states with two or three soft leptons and missing transverse momentum in proton-proton collisions at root s=13 TeV

A search for supersymmetry in events with two or three low-momentum leptons and missing transverse momentum is performed. The search uses proton-proton collisions at s&radic; = 13 TeV collected in the three-year period 2016&ndash;2018 by the CMS experiment at the LHC and corresponding to an integrated luminosity of up to 137 fb&minus;1. The data are found to be in agreement with expectations from standard model processes. The results are interpreted in terms of electroweakino and top squark pair production with a small mass difference between the produced supersymmetric particles and the lightest neutralino. For the electroweakino interpretation, two simplified models are used, a wino-bino model and a higgsino model. Exclusion limits at 95% confidence level are set on &chi;&sim;02/&chi;&sim;&plusmn;1 masses up to 275 GeV for a mass difference of 10 GeV in the wino-bino case, and up to 205(150) GeV for a mass difference of 7.5 (3) GeV in the higgsino case. The results for the higgsino are further interpreted using a phenomenological minimal supersymmetric standard model, excluding the higgsino mass parameter &mu; up to 180 GeV with the bino mass parameter M1 at 800 GeV. In the top squark interpretation, exclusion limits are set at top squark masses up to 540 GeV for four-body top squark decays and up to 480 GeV for chargino-mediated decays with a mass difference of 30 GeV.</p

Measurements of the associated production of a W boson and a charm quark in proton-proton collisions at √s=8TeV

Measurements of the associated production of aW boson and a charm (c) quark in proton&ndash;proton collisionsat a centre-of-mass energy of 8 TeV are reported. The anal-ysis uses a data sample corresponding to a total integratedluminosity of 19.7 fb&minus;1 collected by the CMS detector atthe LHC. The W bosons are identified through their leptonicdecays to an electron or a muon, and a neutrino. Charm quarkjets are selected using distinctive signatures of charm hadrondecays. The product of the cross section and branching frac-tion &sigma; (pp &rarr; W + c + X)B(W &rarr; �&nu;), where � = e or &mu;,and the cross section ratio &sigma; (pp &rarr; W+ + &macr;c + X)/&sigma; (pp &rarr;W&minus; + c + X) are measured in a fiducial volume and differ-entially as functions of the pseudorapidity and of the trans-verse momentum of the lepton from the W boson decay. Theresults are compared with theoretical predictions. The impactof these measurements on the determination of the strangequark distribution is assessed.</p

Study of dijet events with large rapidity separation in proton-proton collisions at root s=2.76 TeV

The cross sections for inclusive and Mueller-Navelet dijet production are measured as a function of the rapidity separation between the jets in proton-proton collisions at s&radic; = 2.76 TeV for jets with transverse momentum pT &gt; 35 GeV and rapidity |y| &lt; 4.7. Various dijet production cross section ratios are also measured. A veto on additional jets with pT &gt; 20 GeV is introduced to improve the sensitivity to the effects of the Balitsky-Fadin-Kuraev-Lipatov (BFKL) evolution. The measurement is compared with the predictions of various Monte Carlo models based on leading-order and next-to-leading-order calculations including the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi leading-logarithm (LL) parton shower as well as the LL BFKL resummation.</p