Observation of proton-tagged, central (semi)exclusive production of high-mass lepton pairs in pp collisions at 13 TeV with the CMS-TOTEM precision proton spectrometer
The process pp$\to\ell^+\ell^-$p$^{(*)}$, with $\ell^+\ell^-$ a muon or an electron pair produced at midrapidity with mass larger than 110 GeV, has been observed for the first time at the LHC in pp collisions at $\sqrt{s} =$ 13 TeV. One of the two scattered protons is measured in the CMS-TOTEM precision proton spectrometer (CT-PPS), which operated for the first time in 2016. The second proton either remains intact or is excited and then dissociates into a low-mass state p$^{*}$, which is undetected. The measurement is based on an integrated luminosity of 9.4 fb$^{-1}$ collected during standard, high-luminosity LHC operation. A total of 12 $μ^+μ^-$ and 8 e$^+$e$^-$ pairs with $m(\ell^{+}\ell^{-}) >$ 110 GeV, and matching forward proton kinematics, are observed, with expected backgrounds of 1.49 $\pm$ 0.07 (stat) $\pm$ 0.53 (syst) and 2.36 $\pm$ 0.09 (stat) $\pm$ 0.47 (syst), respectively. This corresponds to an excess of more than five standard deviations over the expected background. The present result constitutes the first observation of proton-tagged $γγ$ collisions at the electroweak scale. This measurement also demonstrates that CT-PPS performs according to the design specifications.
Exclusive and diffractive physics measurements are important for the better understanding of the non-perturbative regime of QCD. Two recent results of the CMS experiment is presented in this paper. The total and differential cross sections of central exclusive $π^+π^-$ production are measured at 5.02 and 13 TeV in the $p_{\mathrm{T}}(π) > 0.2~$GeV/$c$ and $|η(π)| < 2.4$ kinematic region. The invariant mass distribution is fitted by the sum of a continuum and four interfering relativistic Breit-Wigner functions. In the second part of the paper the measurement of the single diffractive dijets is…
The CMS+TOTEM Precision Proton Spectrometer operated for the first time in 2016, collecting data during $pp$ collisions at $\sqrt{s} = 13$ TeV at the CERN Large Hadron Collider. Procedures for the detector alignment, optics corrections, and background estimations were developed, and applied to an analysis of the process $pp \rightarrow p μ^{+}μ^{-} p^{(*)}$ with dimuon masses larger than 110 GeV. A total of 12 candidate events are observed, corresponding to an excess of $>4σ$ over the background prediction. This constitutes the first evidence for this process at such masses, and demonstrates t…
A search for central exclusive production of top quark pairs ($\mathrm{t}\bar{\mathrm{t}}$) is presented using collision data collected by CMS and the CMS-TOTEM Precision Proton Spectrometer in 2017. A data-driven method to estimate the background from coincidences of inclusive events and pileup protons is described, as well as the development of a Boosted Decision Tree classifier to separate the exclusive $\mathrm{t}\bar{\mathrm{t}}$ signal from the inclusive $\mathrm{t}\bar{\mathrm{t}}$ background. The first-ever upper limits on the cross section of exclusive $\mathrm{t}\bar{\mathrm{t}}$ are…
A search for new physics in central exclusive production using the missing mass technique with the CMS detector and the CMS-TOTEM precision proton spectrometer
The TOTEM experiment with its detectors in the forward region of CMS and the Roman Pots along the beam line will determine the total pp cross-section via the optical theorem by measuring both the elastic cross-section and the total inelastic rate. TOTEM will have dedicated runs with special high-beta* beam optics and a reduced number of proton bunches resulting in a low effective luminosity between 1.6 x 10^{28} cm^{-2} s^{-1} and 2.4 x 10^{29} cm^{-2} s^{-1}. In these special conditions also an absolute luminosity measurement will be made, allowing the calibration of the CMS luminosity monito…
Pseudorapidity (eta) distributions of charged particles produced in proton-proton collisions at a centre-of-mass energy of 8 TeV are measured in the ranges abs(eta) < 2.2 and 5.3 < abs(eta) < 6.4 covered by the CMS and TOTEM detectors, respectively. The data correspond to an integrated luminosity of 45 inverse microbarns. Measurements are presented for three event categories. The most inclusive category is sensitive to 91-96% of the total inelastic proton-proton cross section. The other two categories are disjoint subsets of the inclusive sample that are either enhanced or depleted in single d…
We describe the most recent results from the Proton Precision Spectrometer from the CMS and TOTEM collaborations, namely the first observation of exclusive di-lepton production at high mass at the LHC, and the prospects concerning the sensitivity to quartic anomalous couplings..
Recent CMS results on diffraction are presented. These include the measurements of the soft diffractive cross sections, of the forward rapidity gap cross section, of the diffractive dijet cross section, the measurement of a large rapidity gap in W and Z boson events and the measurement of the pseudorapidity distribution of charged particles in a single diffractive enhanced sample. This last measurement is the first common result of the CMS and TOTEM collaborations. Some prospects of common CMS-TOTEM data taking are also discussed.
At the LHC, diffractive physics will be explored by the dedicated experiment TOTEM whose Technical Design Report has been approved in Summer 2004. The experimental programme will be carried out partly in TOTEM standalone mode for purely forward phenomena like elastic scattering, and partly in collaboration with CMS for processes requiring a full rapidity coverage. ATLAS and ALICE are interested in diffraction for a later stage. This article presents the TOTEM/CMS running scenario for diffractive physics in the first year of LHC. We discuss which processes are within reach and with which statis…
This note highlights the predictive power of the 3-component Pomeron model designed by the authors ten years ago with a partial account of the multiplicity of Pomerons in QCD. The model is put to the test by comparing its predictions with the recent data from DO and TOTEM Collaborations at 1.96 and 7 TeV, respectively. We also compare model predictions for inelastic cross section to experimental measurement by TOTEM, CMS, ALICE, and ATLAS collaborations. It is shown that the DO data are perfectly predicted by the model. Total, elastic, and inelastic cross section predictions are in agreement w…
We analyze the problem of correlating pp interaction data from the central detectors with a subevent measured in an independent system of leading proton detectors using FP420 as an example. FP420 is an R&D project conducted by a collaboration formed by members of ATLAS and CMS to investigate the possibility of detecting new physics in the central exclusive channel, PP -> P + X + P,where the central system X may be a single particle, for example a Standard Model Higgs boson. With standard LHC optics, the protons emerge from the beam at a distance of 420m from the Interaction Point, for M_X ~ 12…
Measurements are presented of the single-diffractive dijet cross section and the diffractive cross section as a function of the proton fractional momentum loss $ξ$ and the four-momentum transfer squared $t$. Both processes pp$\to$pX and pp$\to$Xp, ie with the proton scattering to either side of the interaction point, are measured, where X includes at least two jets; the results of the two processes are averaged. The analyses are based on data collected simultaneously with the CMS and TOTEM detectors at the LHC in proton-proton collisions at $\sqrt{s}$= 8 TeV during a dedicated run with $β^{\as…
In this note we present a measurement of the VZ (V=W,Z) production cross section in proton-proton collisions at $\sqrt{s}=$8 TeV in the VZ$\rightarrow$V$b\bar{b}$ decay mode with V$=$Z$\rightarrow (ν\barν$,$\ell\ell$), V$=$W$\rightarrow \ellν$, ($\ell=e,μ$). The results are based on data corresponding to an integrated luminosity of 18.9 fb$^{-1}$ collected with the CMS experiment. The process is observed for the first time in this particular final state with a significance exceeding six standard deviations ($σ$). The measured cross sections are consistent with the predictions of NLO calculatio…
The CMS/TOTEM and ATLAS collaborations carry out a program of forward physics with several near-beam detectors extending their coverage to high pseudorapidities. This instrumentation includes calorimeters (CASTOR and ZDC), tracking devices (TOTEM T1 and T2), proton taggers (Roman Pots and FP420), and instrumentation dedicated to luminosity monitoring and normalisation. A rich physics program is accessible, including soft QCD interactions, Diffraction, photon-induced physics and luminosity measurements.
In this talk we present a selection of forward physics results recently obtained with the run-1 and run-2 LHC data by the CMS, LHCf and TOTEM experiments. The status of the very forward LHC proton spectrometer, CT-PPS, is discussed: emphasis is given to the physics potential of CT-PPS and to the analyses that are currently ongoing with the data collected in 2016. Very recent forward measurements obtained with the LHCf and the CMS-CASTOR calorimeter are then addressed. In particular, CMS measured the inclusive energy spectrum in the very forward direction for proton-proton collisions at a cente…
Recent results in soft QCD at LHC by the ATLAS, CMS and TOTEM Collaborations are presented. Special focus is reserved to studies in diffractive and forward physics, and to the underlying event, with comparison with previous results and highlighting novel techniques.
We present recent results on Minimum Bias, MPI and DPS, Diffractive and Exclusive studies using data collected during Run 1 of the LHC. The measurements include data collected in pp collisions at $\sqrt s = 7$, and $8$ TeV by the CMS Collaboration. Double parton scattering is investigated in several final states including vector bosons and jets, and the effective cross section results are compared to other experiments and to MPI models tuned to recent underlying event measurements at CMS. Inclusive diffractive cross sections are discussed and compared to models, while searches and measurements…
The first physics results from the TOTEM experiment are here reported, concerning the measurements of the total, differential elastic, elastic and inelastic pp cross-section at the LHC energy of $\sqrt{s}$ = 7 TeV, obtained using the luminosity measurement from CMS. A preliminary measurement of the forward charged particle $η$ distribution is also shown.
The TOTEM experiment at the LHC measures the total proton-proton cross section with the luminosity-independent method and the elastic proton-proton cross-section over a wide |t|-range. It also performs a comprehensive study of diffraction, spanning from cross-section measurements of individual diffractive processes to the analysis of their event topologies. Hard diffraction will be studied in collaboration with CMS taking advantage of the large common rapidity coverage for charged and neutral particle detection and the large variety of trigger possibilities even at large luminosities. TOTEM wi…
The feasibility studies of the measurement of the central exclusive jet production at the LHC using the proton tagging technique are presented. In order to reach the low jet-mass region, single tagged events were considered. The studies were performed at the c.m. energy of 14 TeV and the ATLAS detector, but are also applicable for the CMS-TOTEM experiments. Four data-taking scenarios were considered: AFP and ALFA detectors as forward proton taggers and $β^*$ = 0.55 m and $β^*$ = 90 m optics. After the event selection, the signal-to-background ratio ranges between 5 and $10^4$. Finally, the exp…
We describe recent results from CMS and TOTEM on hard diffraction, diffractive jets and jet gap jet events. We also give the first sensitivities and limits on quartic anomalous couplings and axion-like particles at high mass using the LHC as a $γγ$ collider. The predicted sensitivities with 300 fb$^{-1}$ are better by two or three orders of magnitude compared to the more standard methods at the LHC without measuring intact protons after collision
Photon induced processes can be used as a sensitive probe of new physics searches and can be studied using exclusive processes. These processes lead to unprecedented sensitivities on quartic anomalous couplings between photons and W and Z bosons, and new physics searches. By tagging the leading proton from the hard interaction, the Precision Proton Spectrometer (PPS) provides an increased sensitivity to select exclusive processes. PPS is designed to operate in standard high-luminosity runs at the LHC to perform measurements of e.g. the quartic gauge couplings and search for rare exclusive proc…
We present a result of a search for supersymmetry in final states with missing transverse energy and b-tagged jets. This search is performed with data collected by the CMS experiment at the LHC in pp-collisions at a center-of-mass energy of 7 TeV. Data-driven techniques used to measure the Standard Model background are demonstrated. The result is interpreted in terms of the constrained Minimal Supersymmetric Standard Model and compared to a similar search without any b-tag requirement.
Proton-proton elastic scattering has been measured by the TOTEM experiment at the CERN Large Hadron Collider at $\sqrt{s} = 7 $ TeV in special runs with the Roman Pot detectors placed as close to the outgoing beam as seven times the transverse beam size. The differential cross-section measurements are reported in the |t|-range of 0.36 to 2.5 GeV^2. Extending the range of data to low t values from 0.02 to 0.33 GeV^2,and utilizing the luminosity measurements of CMS, the total proton-proton cross section at sqrt(s) = 7 TeV is measured to be (98.3 +- 0.2(stat) +- 2.8(syst)) mb.
We plan to add high precision tracking- and timing-detectors at z = +/- 240 m to CMS to study exclusive processes p + p -- p + X + p at high luminosity. This enables the LHC to be used as a tagged photon-photon collider, with X = l+l- and W+W-, and as a "tagged" gluon-gluon collider (with a spectator gluon) for QCD studies with jets. A second stage at z = 240 m would allow observations of exclusive Higgs boson production.
Natural SUSY suggests the existence of light stop quarks, accessible at the LHC, which are the focus of a dedicated CMS search program. I present two inclusive CMS searches that look for TeV scale colored sparticles in final states with jets, b-tagged jets and missing transverse energy performed using up to 19.4fb-1 of 8TeV LHC proton-proton data. No deviation from the Standard Model was observed in these searches, and the implications for this was shown for several simplified model scenarios and phenomenological MSSM.
Identification of jets originating from b quarks (b-tagging) is a key element of many physics analyses at the LHC. Various algorithms for b-tagging have been developed by the CMS experiment to identify b-tagged jets with a typical efficiency between 40% and 70% while keeping the rate of misidentified light quark jets between 0.1% and 10%. An important step, in order to be able to use these tools in physics analysis, is the determination of the efficiency for tagging b-jets. Several methods to measure the efficiencies of the lifetime based b-tagging algorithms are presented. Events that have je…
A search for exclusive two-photon production via photon exchange in proton-proton collisions, pp $\to$ p$γγ$p with intact protons, is presented. The data correspond to an integrated luminosity of 9.4 fb$^{-1}$ collected in 2016 using the CMS and TOTEM detectors at a center-of-mass energy of 13 TeV at the LHC. Events are selected with a diphoton invariant mass above 350 GeV and with both protons intact in the final state, to reduce backgrounds from strong interactions. The events of interest are those where the invariant mass and rapidity calculated from the momentum losses of the forward-movin…
In this report, we describe the most recent results on exclusive diffraction from the ATLAS, CMS, LHCb, TOTEM experiments at the LHC concerning exclusive pions, $J/Ψ$, $Ψ(2S)$, dilepton, diphoton, $WW$ productions and prospects concerning the search for anomalous couplings and axion-like particle production.
We discuss a search for natural Supersymmetry in events with at least one bottom-quark jet using razor variables in proton-proton collisions at 8 TeV with the CMS detector. The event distribution in the plane defined by the razor variables $R^2$ and $M_R$ is studied, searching for a peaking signal on top of a smoothly falling standard model background. The data are consistent with the expected background, modeled by a template function. The 95% C.L. exclusion limit on the masses of the gluino and lightest supersymmetric particle in a benchmark simplified model is presented. For a lightest supe…
A search for new physics is performed using isolated same-sign dileptons with at least two b-quark jets in the final state. Results are based on a 4.98 inverse femtobarn sample of proton-proton collisions at a centre-of-mass energy of 7 TeV collected by the CMS detector. No excess above the standard model background is observed. Upper limits at 95% confidence level are set on the number of events from non-standard-model sources. These limits are used to set constraints on a number of new physics models. Information on acceptance and efficiencies are also provided so that the results can be use…
Measurements are reported of the WZ and ZZ production cross sections in proton-proton collisions at sqrt(s) = 8 TeV in final states where one Z boson decays to b-tagged jets. The other gauge boson, either W or Z, is detected through its leptonic decay (either W to e nu, mu nu or Z to e+ e-, mu+ mu-, or nu anti-nu). The results are based on data corresponding to an integrated luminosity of 18.9 inverse femtobarns collected with the CMS detector at the Large Hadron Collider. The measured cross sections, sigma(pp to WZ) = 30.7 +/- 9.3 (stat.) +/- 7.1 (syst.) +/- 4.1 (th.) +/- 1.0 (lum.) pb and si…
A search is presented for an excess of events with large missing transverse momentum in association with at least one highly energetic jet, in a data sample of proton-proton collisions at a centre-of-mass energy of 8 TeV. The data correspond to an integrated luminosity of 19.7 inverse femtobarns collected by the CMS experiment at the LHC. The results are interpreted using a set of simplified models for the production of dark matter via a scalar, pseudoscalar, vector, or axial vector mediator. Additional sensitivity is achieved by tagging events consistent with the jets originating from a hadro…
A search for anomalous production of events with three or more isolated leptons and bottom-quark jets produced in pp collisions at sqrt(s) = 8 TeV is presented. The analysis is based on a data sample corresponding to an integrated luminosity of 19.5 inverse femtobarns collected by the CMS experiment at the LHC in 2012. No excess above the standard model expectations is observed. The results are interpreted in the context of supersymmetric models with signatures that have low missing transverse energy arising from light top-squark pair production with R-parity-violating decays of the lightest s…
We describe the most recent results at the Large Hadron Collider from the ALICE, ATLAS, CMS, LHCb and TOTEM experiments concerning the elastic, inelastic and total cross section measurements as well as particle production in soft and hard processes.
Inclusive and normalised differential cross sections measurements are presented for the production of single top quarks in association with a W boson, in proton-proton collisions at a centre-of-mass energy of 13 TeV. Events containing one muon and one electron in the final state are analysed. For the inclusive measurement, a multivariate discriminant, exploiting the kinematic properties of the events, is used to separate the signal from the dominant t$\bar{\mathrm{t}}$ background. For the differential measurements, a fiducial region is defined according to the detector acceptance, and the requ…
A search has been made for massive resonances decaying into a quark and a vector boson, qW or qZ, or a pair of vector bosons, WW, WZ, or ZZ, where each vector boson decays to hadronic final states. This search is based on a data sample corresponding to an integrated luminosity of 5.0 inverse femtobarns of proton-proton collisions collected in the CMS experiment at the LHC in 2011 at a center-of-mass energy of 7 TeV. For sufficiently heavy resonances the decay products of each vector boson are merged into a single jet, and the event effectively has a dijet topology. The background from QCD dije…
An inclusive search for supersymmetry in events with at least one b-tagged jet is performed using proton-proton collision data collected by the CMS experiment in 2012 at a center-of-mass energy of 8 TeV. The data set size corresponds to an integrated luminosity of 19.3 inverse femtobarns. The two-dimensional distribution of the razor variables R^2 and M[R] is studied in events with and without leptons. The data are found to be consistent with the expected background, which is modeled with an empirical function. Exclusion limits on supersymmetric particle masses at a 95% confidence level are de…
This paper describes the design and the performance of the timing detector developed by the TOTEM Collaboration for the Roman Pots (RPs) to measure the Time-Of-Flight (TOF) of the protons produced in central diffractive interactions at the LHC. The measurement of the TOF of the protons allows the determination of the longitudinal position of the proton interaction vertex and its association with one of the vertices reconstructed by the CMS detectors. The TOF detector is based on single crystal Chemical Vapor Deposition (scCVD) diamond plates and is designed to measure the protons TOF with abou…
A search for narrow resonances and quantum black holes is performed in inclusive and b-tagged dijet mass spectra measured with the CMS detector at the LHC. The data set corresponds to 5 inverse femtobarns of integrated luminosity collected in pp collisions at sqrt(s) = 7 TeV. No narrow resonances or quantum black holes are observed. Model-independent upper limits at the 95% confidence level are obtained on the product of the cross section, branching fraction into dijets, and acceptance for three scenarios: decay into quark-quark, quark-gluon, and gluon-gluon pairs. Specific lower limits are se…
The feasibility studies of the central exclusive jet production at the LHC using the proton tagging technique are presented. Three classes of data taking scenarios are considered: double tag at high pile-up, single tag at low pile-up and double tag at low pile-up. Analyses were performed at the c.m. energy of 14 TeV for the ATLAS experiment, but are also valid for the CMS/TOTEM detectors.
Measurements are presented of the cross section for the production of at least four jets, of which at least two originate from b quarks, in proton-proton collisions. Data collected with the CMS detector at the LHC at a center-of-mass energy of 7 TeV are used, corresponding to an integrated luminosity of 3 inverse picobarns. The cross section is measured as a function of the jet transverse momentum for pt > 20 GeV, and of the jet pseudorapidity for abs(eta) < 2.4 (b jets), 4.7 (untagged jets). The correlations in azimuthal angle and pt between the jets are also studied. The inclusive cross sect…
The CP-violating weak phase $ϕ_\mathrm{s}$ and the decay width difference $ΔΓ_{\mathrm{s}}$ of $\mathrm{B}^{0}_{\mathrm{s}}$ mesons are measured by the CMS experiment at the LHC using a data sample of $\mathrm{B}^{0}_{\mathrm{s}} \! \to \mathrm{J} / ψ\,ϕ$ decays. The analysed dataset corresponds to an integrated luminosity of about $20~\mathrm{fb}^{-1}$ collected in $pp$ collisions at a centre-of-mass energy $\sqrt{s} = 8~\mathrm{TeV}$. A total of $49\,000$ reconstructed $\mathrm{B}^{0}_{\mathrm{s}}$ decays are used to extract the values $ϕ_\mathrm{s}$ and $ΔΓ_\mathrm{s}$ by performing a time-…
Search for nonresonant new physics signals in high-mass dilepton events produced in association with b-tagged jets in proton-proton collisions at $\sqrt{s}$ = 13 TeV
We present a measurement of the WZ and ZZ production cross sections in proton-proton collisions at 8 TeV in final states where one Z boson decays to b-tagged jets, while the other gauge boson, either W or Z, is detected through its leptonic decay. The results are based on data corresponding to an integrated luminosity of 18.9 /fb collected with the CMS detector at the Large Hadron Collider.
We present results from a generic search for strongly produced supersymmetric particles in pp collisions in the multijet + missing transverse momentum final state. The data sample corresponds to 2.3 fb$^{-1}$ recorded by the CMS experiment at $\sqrt{s}=13$ TeV. This search is motivated by supersymmetry (SUSY) models that avoid fine-tuning of the higgs mass. In such models, certain strongly produced SUSY particles, including the gluino and top squark, are predicted to have masses on the order of a TeV. These particles also have some of the highest production cross sections in SUSY and give rise…
A search is reported for massive resonances decaying into a quark and a vector boson (W or Z), or two vector bosons (WW, WZ, or ZZ). The analysis is performed on an inclusive sample of multijet events corresponding to an integrated luminosity of 19.7 inverse femtobarns, collected in proton-proton collisions at a centre-of-mass energy of 8 TeV with the CMS detector at the LHC. The search uses novel jet-substructure identification techniques that provide sensitivity to the presence of highly boosted vector bosons decaying into a pair of quarks. Exclusion limits are set at a confidence level of 9…
A search for neutral Higgs bosons produced in association with b-quark(s) and decaying into a pair of b-quarks is performed with the CMS detector at LHC. The Higgs boson signal is expected to emerge as an excess in the mass spectrum of two b-tagged jets. Dedicated triggers with on-line b-tagging in fully hadronic events were developed specifically for this kind of analysis. Limits on the cross section times branching fractions are derived model independently. The result was interpreted in the Minimal Supersymmetric Model (MSSM). Upper limits at $tanβ$ are derived as a function of MA, the mass …
A Monte Carlo generator has been constructed to simulate the reaction e^+e^- \to γ+ 4 π, where the photon is assumed to be observed in the detector. Only initial state radiation is considered. Additional collinear photon radiation has been incorporated with the technique of structure functions. Predictions are presented for cms energies of 1GeV, 3GeV and 10GeV, corresponding to the energies of DAPHNE, BEBC and of B-meson factories. The event rates are sufficiently high to allow for a precise measurement of R(Q^2) in the region of Q between approximately 1GeV and 2.5GeV. For the construction of…
The CMS Collaboration intends to pursue the study of central exclusive production (CEP) events, pp $\to$ pXp, at the High-Luminosity LHC (HL-LHC) by means of a new near-beam proton spectrometer. In CEP events, the state X is produced at central rapidities, and the scattered protons do not leave the beam pipe. The kinematics of X can be fully reconstructed from that of the protons, which gives access to final states otherwise not visible. CEP allows unique sensitivity to physics beyond the standard model, e.g. in the search for anomalous quartic gauge couplings, axion-like particles, and in gen…
The ATLAS and CMS experiments at the LHC conduct an extensive program to study production of events with a W or Z boson and particle jets. Dedicated studies focus on final states with the jets containing decays of heavy-flavor hadrons (b-tagged jets). The results are obtained using data from proton-proton collisions at sqrt{s}=7 TeV from the LHC at CERN. The set of measurements constitute a stringent test of the perturbative QCD calculations.
Evidence for the production of top quarks in heavy ion collisions is reported in a data sample of lead-lead collisions recorded in 2018 by the CMS experiment at a nucleon-nucleon center-of-mass energy of $\sqrt{s_{_{\mathrm{NN}}}} =$ 5.02 TeV, corresponding to an integrated luminosity of $1.7\pm0.1\,\mathrm{nb}^{-1}$. Top quark pair ($\mathrm{t\bar{t}}$) production is measured in events with two opposite-sign high-$p_\mathrm{T}$ isolated leptons ($\ell^\pm\ell^\mp =\,\mathrm{e}^{+} \mathrm{e}^{-},\,μ^{+} μ^{-},\,\mathrm{and}\,\mathrm{e}^{\pm} μ^{\mp}$). We test the sensitivity to the $\mathrm{…
The PhaseII Upgrades of CMS are being planned for the High Luminosity LHC (HL-LHC) era when the mean number of interactions per beam crossing ("in-time pileup") is expected to reach ~140-200. The potential backgrounds arising from mis-associated jets and photon showers, for example, during event reconstruction could be reduced if physics objects are tagged with an "event time". This tag is fully complementary to the "event vertex" which is already commonly used to reduce mis-reconstruction. Since the tracking vertex resolution is typically ~10^{-3} (50 micron/4.8cm) of the rms vertex distribut…
The modification of jet shapes in PbPb collisions, relative to those in pp collisions, is studied for jets associated with an isolated photon. The data were collected with the CMS detector at the LHC at a nucleon-nucleon center-of-mass energy of 5.02 TeV. Jet shapes are constructed from charged particles with track transverse momenta ($p_\mathrm{T}$) above 1 GeV/c in annuli around the axes of jets with $p^\mathrm{jet}_\mathrm{T}$ $>$ 30 GeV/c associated with an isolated photon with $p^γ_\mathrm{T}$ $>$ 60 GeV/c. The jet shape distributions are consistent between peripheral PbPb and pp collisio…
