本文介绍了一种测量包含射流和双射流产生截面的方法。利用紧凑型μ子螺线管（CMS）探测器收集了大型强子对撞机（LHC）质子-质子碰撞的数据，能量为7 TeV，相当于积分亮度的$\sqrt{s}=$。喷流重建与反$k_T$聚类算法与尺寸参数$R=0.7$，扩展到快速度$|y|=2.5$，横向动量$p_{T}=$ 2 TeV，和dijet不变质量$M_{JJ}=$ 5 TeV。测得的截面进行校正的检测器的影响和微扰QCD预测相比，在下一个领先的顺序（NLO），校正非微扰（NP）的因素，使用各种设置的部分子分布函数。本文介绍了由$\sqrt{s}=$ 7 TeV CMS数据确定喷流能量修正的方法。确定了各个组件。还示出了射流能量标度的不确定性因子。
英文摘要：
A measurement of inclusive jet and dijet production cross sections is presented. Data from large hadron collider (LHC) proton-proton collisions at $\sqrt{s}=$ 7 TeV, corresponding to $4.67 fb^{-1}$ of integrated luminosity, have been collected with the compact muon solenoid (CMS) detector. Jets are reconstructed with the anti-$k_T$ clustering algorithm with size parameter $R=0.7$, extending to rapidity $|y|=2.5$, transverse momentum $p_{T}=$ 2 TeV, and dijet invariant mass $M_{JJ}=$ 5 TeV. The measured cross sections are corrected for detector effects and compared to perturbative QCD predictions at next-to-leading order (NLO), corrected for non perturbative (NP) factors, using various sets of parton distribution functions. Determination Of Jet Energy Correction from $\sqrt{s}=$ 7 TeV CMS data is presented. The individual components are determined. The jet energy scale uncertainty factors are also shown.
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.
We use public data from the CMS experiment to study the 2-prong substructure of jets. The CMS Open Data is based on 31.8/pb of 7 TeV proton-proton collisions recorded at the Large Hadron Collider in 2010, yielding a sample of 768,687 events containing a high-quality central jet with transverse momentum larger than 85 GeV. Using CMS's particle flow reconstruction algorithm to obtain jet constituents, we extract the 2-prong substructure of the leading jet using soft drop declustering. We find good agreement between results obtained from the CMS Open Data and those obtained from parton shower gen…
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…
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.
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.
We perform a detailed comparison of next-to-next-to-leading order (NNLO) QCD predictions for the W+jet and Z+jet processes with 7 TeV experimental data from ATLAS and CMS. We observe excellent agreement between theory and data for most studied observables, which span several orders of magnitude in both cross section and energy. For some observables, such as the $H_T$ distribution, the NNLO QCD corrections are essential for resolving existing discrepancies between theory and data.
The underlying event is an important part of high-energy collision events. In the event generators, the underlying event is tuned by fits to collision data. Usually, the underlying event observables are affected by the existence of extra jets and it is difficult to find a part of the phase space which is dominated by the underlying event. In this paper, we suggest to veto the jets in the considered region to disentangle these effects. The idea is verified to work on CMS Open Data. To our knowledge, it is the first time that such ideas are tested on real collision data.
We present measurements of multi-jet event properties, performed using proton-proton collisions data recorded by the CMS experiment. The jet charge and jet mass distributions are considered in addition to a measurement of the azimuthal angular correlations in 2- and 3-jet events. The measurements are compared to predictions including higher orders matched to parton shower and hadronization, together with predictions from semi-analytical calculations beyond next-to-leading logarithmic accuracy.
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
We present angular correlations in multi-jet events at highest center-of-mass energies and compare the measurements to theoretical predictions including higher order parton radiation and coherence effects.
Recent measurements based on jet production in high energy pp collisions at the CERN LHC with the CMS detector are reported. Specifically, the measurement of the inclusive jet production cross section as a function of the anti-$k_t$ distance parameter $R$ divided by the jet cross section at $R = 0.4$, is discussed. The cross section ratio is sensitive to various perturbative and non-perturbative treatments of the jet formation process in quantum chromodynamics (QCD). In the second study, the regimes of validity of the parton shower and matrix element approaches are tested on multijet events in…
The splitting function is a universal property of quantum chromodynamics (QCD) which describes how energy is shared between partons. Despite its ubiquitous appearance in many QCD calculations, the splitting function cannot be measured directly since it always appears multiplied by a collinear singularity factor. Recently, however, a new jet substructure observable was introduced which asymptotes to the splitting function for sufficiently high jet energies. This provides a way to expose the splitting function through jet substructure measurements at the Large Hadron Collider. In this letter, we…
The most recent results on searches in lepton plus jet final states motivated by different models beyond the standard model are presented, using pp collision data collected by the ATLAS and CMS detectors during Run I and Run II at the CERN LHC. Leptoquarks and heavy Majorana neutrinos that arise in the left-right model are looked for in the final states with two leptons and two jets (ll + jj; l = e; mu; tau ). Heavy Majorana neutrinos are further investigated by relying on a composite-fermion scenario, considering two leptons and one large-radius jet (ll + J; l = e, mu), and in the context of …
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.
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 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.
LHC $t\bar{t}$ data have the potential to provide constraints on the gluon distribution, especially at high $x$, with both ATLAS and CMS performing differential measurements. Recently, CMS has measured double-differential $t\bar{t}$ distributions at 8 TeV. In this paper we examine the impact of this data set on the gluon distribution. To that end we develop novel, double-differential NNLO predictions for that data. No significant impact is found when the CMS data is added to the CT14HERA2 global PDF fit, due to the larger impact of the inclusive jet data from both the Tevatron and the LHC. If …
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.
We present measurements of the inclusive jet production at centre-of-mass energies of 8 and 13 TeV, and of multijets at 8 TeV. These measurements allow to constrain PDFs and the strong coupling constant. Two measurements of the azimuthal correlations at 8 and 13 TeV are also presented, testing higher order QCD calculations.
Measurements of jet energy scale (JES) and resolution (JER) are presented, based on the legacy reconstruction of 13 TeV proton-proton collision data collected by the CMS experiment during the LHC Run 2 period from 2016-2018. Precision measurement of JES is of the utmost importance for the vast majority of physics measurements and searches at CMS. The high pileup, a harsh radiation environment, and time-dependent variations in detector response and calibration, all make precision JES measurement a challenging task. We present in-situ derivations of JES and JER based on CMS Run 2 data, as well a…
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.
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.
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…
We report on the recent CMS measurements of soft hadron-hadron production, including the measurements of inclusive single- and double-diffractive cross sections, as well as the measurement of pseudorapidity distributions, and of the leading charged particle and leading jet cross sections. We present the cross sections for low-pT forward jets production, and production of dijets with large rapidity separation (central-forward, and forward-backward jets). Studies of double parton scattering using four-jet and W+2-jet events, and the cross sections for Drell-Yan with associated jet production are…
The increase of the centre-of-mass energy of the Large Hadron Collider (LHC) to 13 TeV has opened up a new energy regime. Final states including high-momentum multi-jet signatures often dominate beyond standard model phenomena, in particular decay products of new heavy particles. While the potential di-photon resonance currently receives a lot of attention, multi-jet final states pose strong constraints on what physics model an observation could actually be described with. In this presentation, the latest results of the ATLAS and CMS collaborations in high transverse momentum multi-jet final s…
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…
Results by the CMS Collaboration on forward physics, diffraction, and physics in the small-$x$ limit of quantum chromodynamics (QCD), are presented. In particular, results on azimuthal angle decorrelations between two jets in events where two outermost jets are separated by a large rapidity interval are discussed. In addition, results based on the production of two jets separated by a large rapidity gap (interval void of radiation) are presented. These dijet production processes are expected to be sensitive to Balitsky-Fadin-Kuraev-Lipatov (BFKL) evolution effects. We highlight results on incl…
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…
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…
By applying the Error PDF Updating Method, we analyze the impact of the absolute and normalized single differential cross-sections for top-quark pair production data from the ATLAS and CMS experiments at the Large Hadron Collider, at a centre-of-mass energy of $\sqrt{s}= 8$ TeV, on the CT14HERA2 PDFs. We find that the top quark pair single differential distributions provide minor constraints on the CT14HERA2 gluon PDF when the nominal CT14HERA2 inclusive jet production data are included in the fit. Larger constraints on the gluon distribution are present when the jet data are removed (CT14HERA…
We report on our NLL BFKL studies of Mueller-Navelet jets. We first perform a complete NLL BFKL analysis supplemented by a BLM renormalization scale fixing procedure, which is successfully compared with recent CMS data. Second, we argue for the need of a measurement of an asymmetric jet configuration in order to perform a valuable comparison with fixed order approaches. Third, we predict that the energy-momentum violation is rather tiny in the NLL BFKL approach, for an asymmetric jet configuration. Finally, we argue that the double parton scattering contribution is negligible in the kinematics…
The production of a strongly interacting medium in heavy-ion collisions is identified through suppression of high transverse momentum jets leading to an effect known as jet quenching. Detailed measurements of nuclear modification factors and energy flow of the aforementioned quenched jets are performed with the CMS detector. These new results extend previous measurements to large angles with respect to the quenched jets and increase reach in the transverse momentum range. High statistics pp, pPb and PbPb data taken in 2011-13 are used in the following analysis. A new data-driven method to esti…
