We present a study of jet production in association with W and Z bosons in proton-proton collisions at a centre-of-mass energy of 7 TeV using the full 2010 data set collected by CMS corresponding to an integrated luminosity of (35.9 +/- 1.4) inverse picobarn. We report the measurement of ratios s(V + >= n jets)/s(V) and s(V + >= n jets)/s(V + >= (n - 1) jets), where V represents either a W or a Z, s stands for the cross section and n stands for the number of jets.
The results of searches for Supersymmetry in events with two same-sign isolated leptons, hadronic jets, and missing transverse energy in the final state are presented. The searches use pp collisions at 7 TeV collected in 2011 by the CMS experiment.
The most recent results of Standard Model physics using 8 and 13 TeV proton-proton collision data recorded by the CMS detector during the LHC Runs I and II are reviewed. This overview includes studies of several results of vector boson production in association with jets. The outlined results are compared to the corresponding theoretical predictions and no significant deviation is observed.
The capabilities of the ATLAS, CMS and LHCb detectors to reconstruct jets at forward rapidities (|η|> 3) in p-p collisions at the CERN Large Hadron Collider are reviewed. The QCD and Higgs physics motivations for such measurements are summarised. Details are given on studies that provide information on the parton structure and evolution at small values of fractional momenta in the proton.
The study of the associated production of vector bosons and jets constitutes an excellent environment to check numerous QCD predictions. Total and differential cross sections of vector bosons produced in association with jets have been studied in pp collisions using CMS data. Differential distributions as a function of a broad range of kinematical observables are measured and compared with theoretical predictions. In this talk, studies of associated production of vector bosons with inclusive jets and with jets originating from heavy-flavour quarks will be summarized.
We report on the status and history of the CMS commissioning, together with selected results from cosmic-ray muon data. The second part focuses on strategies for optimizing the reconstruction of jets, missing transverse energy and photons for early standard model measurements at ATLAS and CMS with the first collision data from the Large Hadron Collider at CERN.
Measurements of Vector Boson production in association with jets are presented, using p-p collision data at sqrt{s} = 7 TeV. The measurements presented include Z + jets azimuthal correlations, event shapes, vector boson + jets differential cross section measurements, hard double-parton scattering using W + jets events and electroweak Z + forward - backward jet production.
Recent results from CMS are reviewed for searches for supersymmetry in final states with multiple bottom quark jets. Results are based on the full 2012 CMS dataset consisting of 19.5 fb-1 collected at a center-of-mass energy of sqrt(s) = 8 TeV. In particular, searches for final states with multiple b-jets and one or two leptons are presented. These final states are of special interest in the context of the search for third generation squarks in gluino or sbottom cascade decays, as predicted by natural supersymmetry.
The performance of reconstruction and calibration of jets and missing transverse momentum in the CMS Collaboration, together with the latest tools for pileup mitigation, is presented. The results shown are relative to the data collected from 2016 to 2018 (Run 2) in proton-proton collisions at a centre-of-mass energy of 13 TeV. An outlook to the new techniques foreseen for Run 3 is discussed.
This document is dedicated to recent results on the measurements of a vector boson production associated with jets (V+jets) using CMS detector experiment, with a central proton-proton (pp) collision energy of respectively 8 TeV (RunI) and 13 TeV (RunII). The vector boson can be a W boson, Z boson, or photon(γ). The jets are of any flavor, as well as the ones containing heavy flavor quarks, such as bottom(b) quarks. The inclusive cross sections of V+jets processes and differential cross sections as a function of various kinematic observables are presented and compared to several theoretical pre…
Many physics analyses at the LHC are looking into processes where the signal jets are originating from quarks, while jets in the background are more gluon enriched. Based on observables sensitive to fundamental differences in the fragmentation properties of gluons and quarks, a likelihood discriminant is constructed to distinguish between jets originating from quarks and gluons. The performance of the tagger is evaluated using Z+jets and dijet events produced in proton-proton collisions at a centre-of-mass energy of 8 TeV, recorded by the CMS experiment at the LHC.
The cross section for production of Z bosons with two associated b-jets, and Z decaying to leptons, can be measured at the LHC with about 100 pb-1 of data. We use simulated data to study possible strategies for an early measurement of this process with the CMS detector. The rate and kinematic properties of this final state needs to be well understood because it constitutes a large fraction of the total backgrounds to several of the Higgs discovery channels at the LHC.
A variety of models of physics beyond the standard model predict new particles that decay to leptons, jets, or both together. These models include axigluons, colorons, diquarks, excited quarks, heavy long-lived charged particles, leptoquarks, Randall-Sundrum gravitons, string resonances, and new vector bosons (right-handed W and Z'). Using the data collected in 2011 and 2012 at center-of-mass energies of 7 and 8 TeV, the CMS collaboration has performed searches for these new particles in channels with leptons and jets. The results of these searches will be presented. No evidence of new physics…
The observation of the electroweak production of a Z boson with two jets in pp collisions at $\sqrt{s} = 8$ TeV with the CMS experiment at the CERN LHC is presented, based on a data sample with an integrated luminosity of 19.7 fb$^{-1}$. The cross section measurement, combining the muon and electron channels, is in agreement with the theoretical expectations. Radiation patterns of selected Z plus two jets events, and the hadronic activity in the rapidity interval between the jets are also measured. These results are of substantial importance in the more general study of vector boson fusion pro…
Selected results of searches for neutral long-lived particles with displaced and delayed jets, trackless jets and emerging jets, as well as displaced muons, obtained with data recorded at a centre-of-mass energy of 13 TeV by the ATLAS and CMS Collaborations during LHC's Run 2 are presented, as well as challenges and techniques.
We report on cross section measurements for inclusive forward jet production and for the simultaneous production of a forward and a central jet in sqrt{s} = 7 TeV pp-collisions. Data collected in 2010, corresponding to an integrated luminosity of 3.14 pb^{-1}, is used for the measurements. Jets in the transverse momentum range pT = 35 - 140 GeV/c are reconstructed with the anti-kT (R = 0.5) algorithm. The extended coverage of large pseudo-rapidities is provided by the Hadronic Forward calorimeter (3.2 < η< 4.7), while central jets are limited to η< 2.8, covered by the main detector components.…
At the Large Hadron Collider, the identification of jets originating from b quarks is important for searches for new physics and for measurements of standard model processes. A variety of algorithms has been developed by CMS to select b-quark jets based on variables such as the impact parameters of charged-particle tracks, the properties of reconstructed decay vertices, and the presence or absence of a lepton, or combinations thereof. The performance of these algorithms has been measured using data from proton-proton collisions at the LHC and compared with expectations based on simulation. The…
Forward (di)jet measurements are a useful tool to constrain the Parton Distribution Functions (PDFs) at low values of parton momentum fraction x, and to study the possible onset of BFKL or gluon saturation QCD evolutions in the proton. We present studies of jet reconstruction capabilities in the CMS Hadron Forward (HF) calorimeter (3<|eta|<5). The expected sensitivity of the inclusive forward jet p_T spectrum to the proton PDF, as well as the azimuthal decorrelation of Mueller-Navelet jets with a large rapidity separation are presented for p-p collisions at sqrt{s} = 14 TeV.
The top quark mass is measured using $35.9~\mathrm{fb}^{-1}$ of LHC proton-proton collision data collected with the CMS detector at $\sqrt{s}=13~\mathrm{TeV}$ in 2016. The measurement uses the $\mathrm{t}\overline{\mathrm{t}}$ all-jets final state, which comprises a total of six jets. A kinematic fit is performed to reconstruct the decay of the $\mathrm{t}\overline{\mathrm{t}}$ system and suppress QCD multijet background. By means of the ideogram method, the top quark mass is determined, simultaneously constraining an additional jet energy scale factor ($\text{JSF}$). The result of $172.34\pm0…
The performance of jet finding using only charged tracks in CMS has been investigated. Different jet algorithms have been applied to QCD di-jet events, to hadronic tt multi-jet events and on Z+jets events. Results using jets made with tracks only or calorimeter towers are compared for energy response, angular resolution and jet matching to the leading partons. The jet reconstruction performance in the presence of pile-up interactions is presented for the Z+jets sample.
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…
Recent measurements performed by the ATLAS and CMS collaborations on the Run 2 dataset are testing QCD with unprecedented precision. The wealth of data, an ever-improving experimental understanding of jets and photons, and novel measurements of jet substructure enable an improved understanding.
In this paper, selected CMS measurements sensitive to low-x QCD are presented: inclusive cross-sections for forward-central jets production at \sqrt{s}=7 TeV, inclusive cross-sections for forward jets production at 7 TeV and 8 TeV, inclusive to exclusive dijets production cross-sections ratios and correlations of Mueller-Navelet dijets at 7 TeV. Results for data are compared to predictions of theoretical models.
The latest CMS jet measurements in p-p collisions at sqrt(s) = 7 TeV, sensitive to small-x QCD physics, are discussed. These include inclusive forward jet and simultaneous forward-central jet production, as well as production ratios and azimuthal angle decorrelations of jets widely separated in rapidity.
We report on the current simulation studies regarding the reconstruction of Jets and Missing Transverse Energy (MET) with the CMS detector at the CERN proton-proton LHC accelerator. The performance of various jet algorithms is compared, when using calorimeter energy deposits as inputs to the algorithm. The plan for obtaining jet energy corrections is outlined and data-driven correction methods are described. Finally, the performance of MET reconstruction is summarized.
The CMS experiment makes use of a large variety of algorithms to identify the origin of particle jets measured in the detector. Through the study of jet substructure properties, jets originating from quarks, gluons, W/Z/Higgs bosons, top quarks and pileup interactions are identified and categorized. We present new techniques based on machine learning approaches developed for the analysis of the data collected during the LHC Run 2 that significantly surpass the performances of classical taggers.
Jet studies provide an experimental method to explore the features of energy loss in the strongly interacting quark-gluon plasma. Recent jet results from 2.76 TeV PbPb and pp collisions measured with the CMS detector are presented. Jets in the most head-on (central) PbPb collisions are quenched in comparison to pp, and the jets fragment in different ways in the two systems. Measurements from pPb collisions at 5.02 TeV show that the jet and charged particle suppression seen in central PbPb measurements are not due to initial state nuclear effects.
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…
An overview of the searches for heavy resonances that decay to leptons or quarks is presented. The results are based on the data collected by the ATLAS and CMS experiments in proton-proton collisions at $\sqrt{s} = 13~\textrm{TeV}$, and include for the first time the entire LHC Run 2 data set.
The reconstruction and identification of physics objects in the CMS detector, in the context of the charged Higgs boson search analysis, are presented. The reconstruction algorithms and their performance in 7 TeV and 8 TeV LHC data are discussed. The identification of tau hadronic decays, the reconstruction of hadronic jets and missing transverse energy and the identification of b jets are described in detail.
We report on potential for measurement of W and Z boson production, as well as the production in association with jets. Of particular interest are jet multiplicity and $P_{\rm T}$ distributions. The 10 to $100 {\rm pb}^{-1}$ datasets expected in the startup year of operation of LHC are likely to already provide information beyond the reach of the Tevatron collider both in jet multiplicity and $P_{\rm T}$ range. We are especially interested in understanding the ratios of W+jets to Z+jets distributions by comparing them to next-to-leading order Monte Carlo generators, as these processes present …
A neural network technique is used to discriminate between quark and gluon jets produced in the qg->q+photon and q q->g+photon processes at the LHC. Considering the network as a trigger and using the PYTHIA event generator and the full event fast simulation package for the CMS detector CMSJET we obtain signal-to-background ratios.
A search for direct top squark pair production is presented. The search is based on proton-proton collision data at a center-of-mass energy of 13 TeV recorded by the CMS experiment at the LHC during 2016, 2017, and 2018, corresponding to an integrated luminosity of 137 fb$^{-1}$. The search is carried out using events with a single isolated electron or muon, multiple jets, and large transverse momentum imbalance. The observed data are consistent with the expectations from standard model processes. Exclusions are set in the context of simplified top squark pair production models. Depending on t…
We present recent measurements of multijet correlations using forward and low-$p_{\mathrm{T}}$ jets performed by the CMS collaboration at the LHC collider. In pp collisions at $\sqrt{s} = 7$ TeV, azimuthal correlations in dijets separated in rapidity by up to 9.4 units were measured. The results are compared to BFKL- and DGLAP-based Monte Carlo generator and analytic predictions. In pp collisions at $\sqrt{s} = 8$ TeV, cross sections for jets with $p_{\mathrm{T}}$ > 21 GeV and |y| < 4.7, and for track-jets with $p_{\mathrm{T}}$ > 1 GeV (minijets) are presented. The minijet results are sensitiv…
The CMS experiment at the Large Hadron Collider collected in the first months of operation a luminosity of about 300/nb. The first results in the context of the B physics obtained with these data are presented. The di-muon resonances from J/psi and Y decays are presented and their total and differential cross-sections measured. The inclusive B production have also being investigated and two independent measurements are reported. Muons in jets are used as a way to identify events with B content, the kinematic properties (ptRel) of the muons are used to separate the B production from other proce…
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.
We present predictions for the inclusive production of charm jets in proton-proton collisions at 2.76 and 5.02 TeV. The charm-quark is considered massless. In this scheme we find that the ratio of the next-to-leading order to the leading order cross section (K factor) is almost equal to one depending essentially on the choice of the renormalization and factorization scale. Adding non-pertubative corrections obtained from Pythia Monte Carlo calculations lead to reasonable agreement with experimental c-jet cross sections obtained by the CMS collaboration.
Recent measurements dedicated to improving the understanding of modelling top quark pair (${\text{t}\overline{\text{t}}}$) production at the LHC are summarised. These measurements, performed with proton-proton collision data collected by the CMS detector at $\sqrt{s}=$ 13 TeV, probe the underlying event in ${\text{t}\overline{\text{t}}}$ events, and use the abundance of jets in ${\text{t}\overline{\text{t}}}$ events to study the substructure of jets. A new set of tunes for PYTHIA 8, and their performance with ${\text{t}\overline{\text{t}}}$ data, are also discussed.
Many physics signals presently studied at the high energy collision experiments lead to final states with jets originating from heavy flavor quarks. This report reviews the algorithms for heavy flavor jets identification developed by the ATLAS and CMS Collaborations in view of the Run2 data taking period at the Large Hadron Collider. The improvements of the algorithms used in 2015 and 2016 data analyses with respect to previous data taking periods are discussed, as well as the ongoing developments in view of the next years of data taking. The measurements of the performance of the algorithms o…
Recent CMS data significantly extend the direct search exclusion for supersymmetry. We examine the impact of such data on global fits of the constrained minimal supersymmetric standard model (CMSSM) to indirect and cosmological data. By simulating supersymmetric signal events at the LHC, we construct a likelihood map for the recent CMS data, validating it against the exclusion region calculated by the experiment itself. A previous CMSSM global fit is then re-weighted by our likelihood map. The CMS results nibble away at the high fit probability density region, transforming probability distribu…
We explore the metric space of jets using public collider data from the CMS experiment. Starting from 2.3/fb of 7 TeV proton-proton collisions collected at the Large Hadron Collider in 2011, we isolate a sample of 1,690,984 central jets with transverse momentum above 375 GeV. To validate the performance of the CMS detector in reconstructing the energy flow of jets, we compare the CMS Open Data to corresponding simulated data samples for a variety of jet kinematic and substructure observables. Even without detector unfolding, we find very good agreement for track-based observables after using c…
Measurements of heavy flavor production in pp collisions at sqrt(s) = 7.0 TeV recorded at the CMS experiment are presented. Double differential cross sections with respect to transverse momentum and rapidity are shown for J/Psi and Upsilon(1S), Upsilon(2S), and Upsilon(3S). The inclusive open beauty rate is measured with two different techniques, including a study of the angular correlations between b jets in events with two identified b jets. Lastly, the B+, B0, and B0s production rates are measured from the reconstruction of exclusive final states.
This document gives an overview over the recent results on helicity measurement of W boson originated from top pair events. The results are obtained using data collected by the CMS detector at a center-of-mass energy of 8 TeV. The helicity measurements are confronted with the most precise theoretical predictions of the standard model.
The identification of jets originating from b quarks is crucial both for the searches for new physics and for the measurement of standard model processes. The Compact Muon Solenoid (CMS) collaboration at the Large Hadron Collider (LHC) has developed a variety of algorithms to select b-quark jets based on variables such as the impact parameter of charged particle tracks, properties of reconstructed secondary vertices from heavy hadron decays, and the presence or absence of a lepton in the jet, or combinations thereof. Performance measurements of these b-jet identification algorithms are present…
This article presents a review of recent results on direct top quark mass measurements performed by the ATLAS and CMS collaborations on $pp$ collisions collected during Run 2 of the LHC at $\sqrt{s}=$13 TeV.
A brief review of the discovery potential of the ATLAS and CMS experiments to search for signals from extra dimensions in different luminosity scenarios is given.
New physics beyond the Standard Model could well preferentially show up at the LHC in final states with taus. The development of efficient and accurate reconstruction and identification of taus is therefore an important item in the CMS physics programme. The potentially superior performance of a particle-flow approach can help to achieve this goal with the CMS detector. Preliminary strategies are presented in this summary for the hadronic decays of the taus.
The CMS Detector consists of a large volume silicon tracker immersed in a high four Tesla magnetic field, together with a high resolution/granularity electromagnetic calorimeter and a nearly full solid angle coverage hadronic calorimeter. Particle flow reconstruction provides a global pp-collision event description by exploiting the combined information across all CMS sub-detectors, optimizing the reconstruction and the identification of each particle (photons, electrons, muons, unstable neutral hadrons, charged hadrons and neutral hadrons) in an event. This summary introduces the CMS particle…
The normalised differential top quark-antiquark production cross section is measured as a function of the jet multiplicity. Using a procedure to associate jets to decay products of the top quarks, the differential cross section of the ttbar production is determined as a function of the additional jet multiplicity. The fraction of events with no additional jets is measured as a function of the threshold required for the transverse momentum of the additional jet. The measurements are compared with predictions from perturbative quantum chromodynamics and no significant deviations are observed.
The Standard Model violates parity, but only by mechanisms which are invisible to Large Hadron Collider (LHC) experiments (on account of the lack of initial state polarisation or spin-sensitivity in the detectors). Nonetheless, new physical processes could potentially violate parity in ways which are detectable by those same experiments. If those sources of new physics occur only at LHC energies, they are untested by direct searches. We probe the feasibility of such measurements using approximately 0.2 inverse femtobarns of data which was recorded in 2012 by the CMS collaboration and made publ…
An overview of recent measurements of differential top quark pair production cross sections performed by the CMS experiment at the LHC is presented. Measurements at different proton-proton center-of-mass energies are available using the dilepton, lepton+jets, and all-jets decay channels of the top quark. In addition to the measurements of parton-level top quarks, many measurements at particle level in an experimental accessible phase space are now available. For these results the dependence on theoretical extrapolations is reduced. A common observation of all measurements is a softer transvers…
First searches for new physics phenomena using the LHC 7 TeV proton-proton collision data collected by the CMS detector in 2010 are reviewed. Results are presented of searches for new physics in events with hadronic jet pairs, and for heavy stable charged particles, including a dedicated search for long-lived particles that stop in the detector and decay in periods between beam crossings.
We present an overview of measurements of electroweak vector boson pair production and anomalous Triple Gauge Couplings (aTGC), with semileptonic and fully leptonic final states. The data analyzed were taken at center of mass energy of 7 & 8 TeV by the CMS detector at the Large Hadron Collider. The cross-section measurements are important because they are test of the Standard Model predictions, while these processes serve as background for Higgs searches and various other processes.
I give an overview of recent results on top quark properties and interactions, obtained using data collected with the CMS experiment during the years 2010--2011 at sqrt(s)= 7 TeV. Measurements are presented for the inclusive top pair production cross section, using the dilepton, lepton plus jets, and hadronic channels. The mass of the top quark is measured using the dilepton and lepton plus jets samples. CMS also measures the cross section for electroweak production of single top quarks and constrains the CKM matrix element V_tb. Top quark results are compared with Standard Model predictions a…
New heavy resonances are predicted by many extensions of the standard model of particle physics. Recent results for high mass resonance searches with the Compact Muon Solenoid detector, in the diphoton, dilepton, dijet and ttbar channels, are discussed. Limits for numerous benchmark models are presented.
We present a search for supersymmetry (SUSY) in the fully hadronic final state with the CMS detector at the LHC. This final state contains at least two jets and a significant transverse energy imbalance due to neutralinos escaping detection. The background to all-hadronic signature arise from QCD multijet production, ttbar and electroweak boson+jet production. These background can be estimated by utilizing a data-driven approach using events thus enabling a possible discovery of SUSY in the early physics data. In addition to the generic search, we also present an analysis which utilizes a new …
