Review of top quark mass measurements in CMS

OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information) · 2025 · 8 citations

• Particle physics
• Physics
• Nuclear physics

The top quark mass is one of the most intriguing parameters of the standard model (SM). Its value indicates a Yukawa coupling close to unity, and the resulting strong ties to Higgs physics make the top quark mass a crucial ingredient for understanding essential aspects of the electroweak sector of the SM. This review offers the first comprehensive overview of the top quark mass measurements performed by the CMS Collaboration using the data collected at centre-of-mass energies of 7, 8, and 13 TeV. Moreover, a detailed description of the top quark event reconstruction is provided and dedicated studies of the dominant uncertainties in the modelling of the signal processes are discussed. The interpretation of the experimental results on the top quark mass in terms of the SM Lagrangian parameter is challenging and is a focus of an ongoing discussion in the theory community. The CMS Collaboration has performed two main types of top quark mass measurements, addressing this challenge from different perspectives: highly precise ‘direct’ measurements, based on reconstructed top quark decay products and relying exclusively on Monte-Carlo simulations, as well as ‘indirect’ measurements, where the simulations are employed to determine parton-level cross sections that are compared to fixed-order perturbative calculations. Recent mass extractions using Lorentz-boosted top quarks open a new avenue of measurements based on top quark decay products contained in a single particle jet, with promising prospects for accurate theoretical interpretations.

Model-independent search for pair production of new bosons decaying into muons in proton-proton collisions at $$ \sqrt{s} $$ = 13 TeV

arXiv (Cornell University) · 2024 · 2 citations

• Physics
• Particle physics
• Nuclear physics

A bstract The results of a model-independent search for the pair production of new bosons within a mass range of 0 . 21 &lt; m &lt; 60 GeV, are presented. This study utilizes events with a four-muon final state. We use two data sets, comprising 41 . 5 fb − 1 and 59 . 7 fb − 1 of proton-proton collisions at $$ \sqrt{s} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> </mml:math> = 13 TeV, recorded in 2017 and 2018 by the CMS experiment at the CERN LHC. The study of the 2018 data set includes a search for displaced signatures of a new boson within the proper decay length range of 0 &lt; cτ &lt; 100 mm. Our results are combined with a previous CMS result, based on 35 . 9 fb − 1 of proton-proton collisions at $$ \sqrt{s} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> </mml:math> = 13 TeV collected in 2016. No significant deviation from the expected background is observed. Results are presented in terms of a model-independent upper limit on the product of cross section, branching fraction, and acceptance. The findings are interpreted across various benchmark models, such as an axion-like particle model, a vector portal model, the next-to-minimal supersymmetric standard model, and a dark supersymmetric scenario, including those predicting a non-negligible proper decay length of the new boson. In all considered scenarios, substantial portions of the parameter space are excluded, expanding upon prior results.

Stairway to discovery: A report on the CMS programme of cross section measurements from millibarns to femtobarns

Physics Reports · 2024 · 9 citations

• Physics
• Particle physics
• Nuclear physics

The Large Hadron Collider at CERN, delivering proton-proton collisions at much higher energies and far higher luminosities than previous machines, has enabled a comprehensive programme of measurements of the standard model (SM) processes by the CMS experiment. These unprecedented capabilities facilitate precise measurements of the properties of a wide array of processes, the most fundamental being cross sections. The discovery of the Higgs boson and the measurement of its mass became the keystone of the SM. Knowledge of the mass of the Higgs boson allows precision comparisons of the predictions of the SM with the corresponding measurements. These measurements span the range from one of the most copious SM processes, the total inelastic cross section for proton-proton interactions, to the rarest ones, such as Higgs boson pair production. They cover the production of Higgs bosons, top quarks, single and multibosons, and hadronic jets. Associated parameters, such as coupling constants, are also measured. These cross section measurements can be pictured as a descending stairway, on which the lowest steps represent the rarest processes allowed by the SM, some never seen before.

New Structures in the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>J</mml:mi><mml:mo>/</mml:mo><mml:mi>ψ</mml:mi><mml:mi>J</mml:mi><mml:mo>/</mml:mo><mml:mi>ψ</mml:mi></mml:mrow></mml:math> Mass Spectrum in Proton-Proton Collisions at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msqrt><mml:mrow><mml:mi>s</mml:mi></mml:mrow></mml:msqrt><mml:mo>=</mml:mo><mml:mn>13</mml:mn><mml:mtext> </mml:mtext><mml:mtext> </mml:mtext><mml:mi>TeV</mml:mi></mml:mrow></mml:math>

Physical Review Letters · 2024 · 96 citations

• Physics

A search is reported for near-threshold structures in the J/ψJ/ψ invariant mass spectrum produced in proton-proton collisions at sqrt[s]=13 TeV from data collected by the CMS experiment, corresponding to an integrated luminosity of 135 fb^{-1}. Three structures are found, and a model with quantum interference among these structures provides a good description of the data. A new structure is observed with a local significance above 5 standard deviations at a mass of 6638_{-38}^{+43}(stat)_{-31}^{+16}(syst) MeV. Another structure with even higher significance is found at a mass of 6847_{-28}^{+44}(stat)_{-20}^{+48}(syst) MeV, which is consistent with the X(6900) resonance reported by the LHCb experiment and confirmed by the ATLAS experiment. Evidence for another new structure, with a local significance of 4.7 standard deviations, is found at a mass of 7134_{-25}^{+48}(stat)_{-15}^{+41}(syst) MeV. Results are also reported for a model without interference, which does not fit the data as well and shows mass shifts up to 150 MeV relative to the model with interference.

Search for Long-Lived Heavy Neutral Leptons with Lepton Flavour Conserving or Violating Decays to a Jet and a Charged Lepton

arXiv (Cornell University) · 2023 · 1 citations

• Physics
• Particle physics
• Nuclear physics

A search for long-lived heavy neutral leptons (HNLs) is presented, which considers the hadronic final state and coupling scenarios involving all three lepton generations in the 2-20 GeV HNL mass range for the first time. Events comprising two leptons (electrons or muons) and jets are analyzed in a data sample of proton-proton collisions, recorded with the CMS experiment at the CERN LHC at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb$^{-1}$. A novel jet tagger, based on a deep neural network, has been developed to identify jets from an HNL decay using various features of the jet and its constituent particles. The network output can be used as a powerful discriminating tool to probe a broad range of HNL lifetimes and masses. Contributions from background processes are determined from data. No excess of events in data over the expected background is observed. Upper limits on the HNL production cross section are derived as functions of the HNL mass and the three coupling strengths $V_{\ell\mathrm{N}}$ to each lepton generation $\ell$ and presented as exclusion limits in the coupling-mass plane, as lower limits on the HNL lifetime, and on the HNL mass. In this search, the most stringent limit on the coupling strength is obtained for pure muon coupling scenarios; values of $\lvert V_{\mu\mathrm{N}}\rvert^{2}\gt $ 5 (4)$\times$10$^{-7}$ are excluded for Dirac (Majorana) HNLs with a mass of 10 GeV at a confidence level of 95% that correspond to proper decay lengths of 17 (10) mm.

Measurement of the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"><mml:msubsup><mml:mrow><mml:mtext>B</mml:mtext></mml:mrow><mml:mrow><mml:mtext>s</mml:mtext></mml:mrow><mml:mrow><mml:mn>0</mml:mn></mml:mrow></mml:msubsup><mml:mo stretchy="false">→</mml:mo><mml:msup><mml:mrow><mml:mi mathvariant="normal">μ</mml:mi></mml:mrow><mml:mrow><mml:mo linebreak="badbreak" linebreakstyle="after">+</mml:mo></mml:mrow></mml:msup><mml:msup><mml:mrow><mml:mi mathvariant="normal">μ</mml:mi></mml:mrow><mml:mrow><mml:mo linebreak="badbreak" linebreakstyle="after">−</mml:mo></mml:mrow></mml:msup></mml:math> decay properties and search for the B0 → μ+μ− decay in proton-proton collisions at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.svg"><mml:msqrt><mml:mrow><mml:mi>s</mml:mi></mml:mrow></mml:msqrt><mml:mo linebreak="goodbreak" linebreakstyle="after">=</mml:mo><mml:mn>13</mml:mn><mml:mspace width="0.2em"/><mml:mtext>TeV</mml:mtext></mml:math>

Physics Letters B · 2023 · 75 citations

• Computer Science
• Physics
• Algorithm

Measurements are presented of the Bs0→μ+μ− branching fraction and effective lifetime, as well as results of a search for the B0→μ+μ− decay in proton-proton collisions at s=13TeV at the LHC. The analysis is based on data collected with the CMS detector in 2016–2018 corresponding to an integrated luminosity of 140fb−1. The branching fraction of the Bs0→μ+μ− decay and the effective Bs0 meson lifetime are the most precise single measurements to date. No evidence for the B0→μ+μ− decay has been found. All results are found to be consistent with the standard model predictions and previous measurements.

A portrait of the Higgs boson by the CMS experiment ten years after the discovery

Nature · 2022 · 320 citations

• Physics
• Particle physics
• Nuclear physics

In July 2012, the ATLAS and CMS collaborations at the CERN Large Hadron Collider announced the observation of a Higgs boson at a mass of around 125 gigaelectronvolts. Ten years later, and with the data corresponding to the production of a 30-times larger number of Higgs bosons, we have learnt much more about the properties of the Higgs boson. The CMS experiment has observed the Higgs boson in numerous fermionic and bosonic decay channels, established its spin-parity quantum numbers, determined its mass and measured its production cross-sections in various modes. Here the CMS Collaboration reports the most up-to-date combination of results on the properties of the Higgs boson, including the most stringent limit on the cross-section for the production of a pair of Higgs bosons, on the basis of data from proton-proton collisions at a centre-of-mass energy of 13 teraelectronvolts. Within the uncertainties, all these observations are compatible with the predictions of the standard model of elementary particle physics. Much evidence points to the fact that the standard model is a low-energy approximation of a more comprehensive theory. Several of the standard model issues originate in the sector of Higgs boson physics. An order of magnitude larger number of Higgs bosons, expected to be examined over the next 15 years, will help deepen our understanding of this crucial sector.

Measurement of $$\hbox {t}{\bar{\hbox {t}}}$$ normalised multi-differential cross sections in $${\text {p}}{\text {p}} $$ collisions at $$\sqrt{s}=13\,{\text {TeV}} $$, and simultaneous determination of the strong coupling strength, top quark pole mass, and parton distribution functions

The European Physical Journal C · 2020 · 92 citations

• Physics
• Particle physics
• Nuclear physics

Abstract Normalised multi-differential cross sections for top quark pair ( $$\hbox {t}{\bar{\hbox {t}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mtext>t</mml:mtext><mml:mover><mml:mrow><mml:mtext>t</mml:mtext></mml:mrow><mml:mrow><mml:mo>¯</mml:mo></mml:mrow></mml:mover></mml:mrow></mml:math> ) production are measured in proton-proton collisions at a centre-of-mass energy of 13 $$\,{\text {TeV}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mspace/><mml:mtext>TeV</mml:mtext></mml:mrow></mml:math> using events containing two oppositely charged leptons. The analysed data were recorded with the CMS detector in 2016 and correspond to an integrated luminosity of $$35.9{\,{\text {fb}}^{-1}} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mn>35.9</mml:mn><mml:mrow><mml:mspace/><mml:msup><mml:mrow><mml:mtext>fb</mml:mtext></mml:mrow><mml:mrow><mml:mo>-</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:mrow></mml:math> . The double-differential $$\hbox {t}{\bar{\hbox {t}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mtext>t</mml:mtext><mml:mover><mml:mrow><mml:mtext>t</mml:mtext></mml:mrow><mml:mrow><mml:mo>¯</mml:mo></mml:mrow></mml:mover></mml:mrow></mml:math> cross section is measured as a function of the kinematic properties of the top quark and of the $$\hbox {t}{\bar{\hbox {t}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mtext>t</mml:mtext><mml:mover><mml:mrow><mml:mtext>t</mml:mtext></mml:mrow><mml:mrow><mml:mo>¯</mml:mo></mml:mrow></mml:mover></mml:mrow></mml:math> system at parton level in the full phase space. A triple-differential measurement is performed as a function of the invariant mass and rapidity of the $$\hbox {t}{\bar{\hbox {t}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mtext>t</mml:mtext><mml:mover><mml:mrow><mml:mtext>t</mml:mtext></mml:mrow><mml:mrow><mml:mo>¯</mml:mo></mml:mrow></mml:mover></mml:mrow></mml:math> system and the multiplicity of additional jets at particle level. The data are compared to predictions of Monte Carlo event generators that complement next-to-leading-order (NLO) quantum chromodynamics (QCD) calculations with parton showers. Together with a fixed-order NLO QCD calculation, the triple-differential measurement is used to extract values of the strong coupling strength $$\alpha _{S}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>α</mml:mi><mml:mi>S</mml:mi></mml:msub></mml:math> and the top quark pole mass ( $$m_{{\text {t}}}^{{\text {pole}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mi>m</mml:mi><mml:mrow><mml:mtext>t</mml:mtext></mml:mrow><mml:mtext>pole</mml:mtext></mml:msubsup></mml:math> ) using several sets of parton distribution functions (PDFs). The measurement of $$m_{{\text {t}}}^{{\text {pole}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mi>m</mml:mi><mml:mrow><mml:mtext>t</mml:mtext></mml:mrow><mml:mtext>pole</mml:mtext></mml:msubsup></mml:math> exploits the sensitivity of the $$\hbox {t}{\bar{\hbox {t}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mtext>t</mml:mtext><mml:mover><mml:mrow><mml:mtext>t</mml:mtext></mml:mrow><mml:mrow><mml:mo>¯</mml:mo></mml:mrow></mml:mover></mml:mrow></mml:math> invariant mass distribution to $$m_{{\text {t}}}^{{\text {pole}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mi>m</mml:mi><mml:mrow><mml:mtext>t</mml:mtext></mml:mrow><mml:mtext>pole</mml:mtext></mml:msubsup></mml:math> near the production threshold. Furthermore, a simultaneous fit of the PDFs, $$\alpha _{S}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>α</mml:mi><mml:mi>S</mml:mi></mml:msub></mml:math> , and $$m_{{\text {t}}}^{{\text {pole}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mi>m</mml:mi><mml:mrow><mml:mtext>t</mml:mtext></mml:mrow><mml:mtext>pole</mml:mtext></mml:msubsup></mml:math> is performed at NLO, demonstrating that the new data have significant impact on the gluon PDF, and at the same time allow an accurate determination of $$\alpha _{S}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>α</mml:mi><mml:mi>S</mml:mi></mml:msub></mml:math> and $$m_{{\text {t}}}^{{\text {pole}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mi>m</mml:mi><mml:mrow><mml:mtext>t</mml:mtext></mml:mrow><mml:mtext>pole</mml:mtext></mml:msubsup></mml:math> . The values $$\alpha _{S}(m_{{\text {Z}}}) = 0.1135{}^{+0.0021}_{-0.0017}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>α</mml:mi><mml:mi>S</mml:mi></mml:msub><mml:mrow><mml:mo>(</mml:mo><mml:msub><mml:mi>m</mml:mi><mml:mtext>Z</mml:mtext></mml:msub><mml:mo>)</mml:mo></mml:mrow><mml:mo>=</mml:mo><mml:mn>0.1135</mml:mn><mml:msubsup><mml:mrow/><mml:mrow><mml:mo>-</mml:mo><mml:mn>0.0017</mml:mn></mml:mrow><mml:mrow><mml:mo>+</mml:mo><mml:mn>0.0021</mml:mn></mml:mrow></mml:msubsup></mml:mrow></mml:math> and $$m_{{\text {t}}}^{{\text {pole}}} = 170.5 \pm 0.8 \,{\text {GeV}} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msubsup><mml:mi>m</mml:mi><mml:mrow><mml:mtext>t</mml:mtext></mml:mrow><mml:mtext>pole</mml:mtext></mml:msubsup><mml:mo>=</mml:mo><mml:mn>170.5</mml:mn><mml:mo>±</mml:mo><mml:mn>0.8</mml:mn><mml:mspace/><mml:mtext>GeV</mml:mtext></mml:mrow></mml:math> are extracted, which account for experimental and theoretical uncertainties, the latter being estimated from NLO scale variations. Possible effects from Coulomb and soft-gluon resummation near the $$\hbox {t}{\bar{\hbox {t}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mtext>t</mml:mtext><mml:mover><mml:mrow><mml:mtext>t</mml:mtext></mml:mrow><mml:mrow><mml:mo>¯</mml:mo></mml:mrow></mml:mover></mml:mrow></mml:math> production threshold are neglected in these parameter extractions. A rough estimate of these effects indicates an expected correction of $$m_{{\text {t}}}^{{\text {pole}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mi>m</mml:mi><mml:mrow><mml:mtext>t</mml:mtext></mml:mrow><mml:mtext>pole</mml:mtext></mml:msubsup></mml:math> of the order of $$+1 \,{\text {GeV}} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mo>+</mml:mo><mml:mn>1</mml:mn><mml:mspace/><mml:mtext>GeV</mml:mtext></mml:mrow></mml:math> , which can be regarded as additional theoretical uncertainty in the current $$m_{{\text {t}}}^{{\text {pole}}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msubsup><mml:mi>m</mml:mi><mml:mrow><mml:mtext>t</mml:mtext></mml:mrow><mml:mtext>pole</mml:mtext></mml:msubsup></mml:math> extraction.