Giacomo Ortona

Higgs pair production provides a unique handle for measuring the strength of the Higgs self interaction and constraining the shape of the Higgs potential. Among the proposed future facilities, a circular 100 TeV proton-proton collider would provide the most precise measurement of this crucial quantity. In this work, we perform a detailed analysis of the most promising decay channels and derive the expected sensitivity of their combination, assuming an integrated luminosity of 30 ab$^{-1}$. Depending on the assumed systematic uncertainties, we observe that the Higgs self-coupling will be measured with a precision in the range 3.4 - 7.8% at 68% confidence level.

The charge asymmetry in the production of top quark and antiquark pairs is measured in proton-proton collisions at a center-of-mass energy of 8 TeV. The data, corresponding to an integrated luminosity of 19.6 inverse femtobarns, were collected by the CMS experiment at the LHC. Events with a single isolated electron or muon, and four or more jets, at least one of which is likely to have originated from hadronization of a bottom quark, are selected. A template technique is used to measure the asymmetry in the distribution of differences in the top quark and antiquark absolute rapidities. The measured asymmetry is A[c,y] = [0.33 +/- 0.26 (stat) +/- 0.33 (syst)]%, which is the most precise result to date. The results are compared to calculations based on the standard model and on several beyond-the-standard-model scenarios.

We present a parton-level study of electro-weak production of vector-boson pairs at the Large Hadron Collider, establishing the sensitivity to a set of dimension-six operators in the Standard Model Effective Field Theory (SMEFT). Different final states are statistically combined, and we discuss how the orthogonality and interdependence of different analyses must be considered to obtain the most stringent constraints. The main novelties of our study are the inclusion of SMEFT effects in non-resonant diagrams and in irreducible QCD backgrounds, and an exhaustive template analysis of optimal observables for each operator and process considered. We also assess for the first time the sensitivity of vector-boson-scattering searches in semileptonic final states.

A measurement of the Higgs boson Yukawa coupling to the top quark is presented using proton-proton collision data at $\sqrt{s} =$ 13 TeV, corresponding to an integrated luminosity of 137 fb$^{-1}$, recorded with the CMS detector. The coupling strength with respect to the standard model value, $Y_\mathrm{t}$, is determined from kinematic distributions in $\mathrm{t\bar{t}}$ final states containing ee, $μμ$, or e$μ$ pairs. Variations of the Yukawa coupling strength lead to modified distributions for $\mathrm{t\bar{t}}$ production. In particular, the distributions of the mass of the $\mathrm{t\bar{t}}$ system and the rapidity difference of the top quark and antiquark are sensitive to the value of $Y_\mathrm{t}$. The measurement yields a best fit value of $Y_\mathrm{t} =$ 1.16 $^{+0.24}_{-0.35}$, bounding $Y_\mathrm{t}$ $\lt$ 1.54 at a 95% confidence level.

Abstract In 1956 Reines & Cowan discovered the neutrino using a liquid scintillator detector. The neutrinos interacted with the scintillator, producing light that propagated across transparent volumes to surrounding photo-sensors. This approach has remained one of the most widespread and successful neutrino detection technologies used since. This article introduces a concept that breaks with the conventional paradigm of transparency by confining and collecting light near its creation point with an opaque scintillator and a dense array of optical fibres. This technique, called LiquidO, can provide high-resolution imaging to enable efficient identification of individual particles event-by-event. A natural affinity for adding dopants at high concentrations is provided by the use of an opaque medium. With these and other capabilities, the potential of our detector concept to unlock opportunities in neutrino physics is presented here, alongside the results of the first experimental validation.

Anisotropic transverse flow patterns that are observed in relativistic heavy ion collisions can be added to the available microscopic Monte Carlo event generators as a final state modification to the azimuthal angles of the particles, which are generated isotropically. The method proposed for this purpose by A. M. Poskanzer and S. A. Voloshin [Phys. Rev. C 58, 1671 (1998)] is valid only for small values of the Fourier coefficients ${v}_{n}$ and therefore it is not suitable for simulations with large values of anisotropy such as the ones predicted for Pb-Pb collisions at the LHC. We present here a possible solution to treat the cases of large anisotropies.

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-moving protons matches the mass and rapidity of the central, two-photon system. No events are found that satisfy this condition. Interpreting this result in an effective dimension-8 extension of the standard model, the first limits are set on the two anomalous four-photon coupling parameters. If the other parameter is constrained to its standard model value, the limits at 95% CL are $\lvertζ_1\rvert$ $\lt$ 2.9 $\times$ 10$^{-13}$ GeV$^{-4}$ and $\lvertζ_2\rvert$ $\lt$ 6.0 $\times$ 10$^{-13}$ GeV$^{-4}$.

A search is performed for the production of a massive W′ boson decaying to a top and a bottom quark. The data analysed correspond to an integrated luminosity of 19.7 fb−1 collected with the CMS detector at the LHC in proton-proton collisions at $$ \sqrt{s}=8 $$ TeV. The hadronic decay products of the top quark with high Lorentz boost from the W′ boson decay are detected as a single top flavoured jet. The use of jet substructure algorithms allows the top quark jet to be distinguished from standard model QCD background. Limits on the production cross section of a right-handed W′ boson are obtained, together with constraints on the left-handed and right-handed couplings of the W′ boson to quarks. The production of a right-handed W′ boson with a mass below 2.02 TeV decaying to a hadronic final state is excluded at 95% confidence level. This mass limit increases to 2.15 TeV when both hadronic and leptonic decays are considered, and is the most stringent lower mass limit to date in the tb decay mode.

A detailed study of charge collection efficiency has been performed on the Silicon Drift Detectors (SDD) of the ALICE experiment. Three different methods to study the collected charge as a function of the drift time have been implemented. The first approach consists in measuring the charge at different injection distances moving an infrared laser by means of micrometric step motors. The second method is based on the measurement of the charge injected by the laser at fixed drift distance and varying the drift field, thus changing the drift time. In the last method, the measurement of the charge deposited by atmospheric muons is used to study the charge collection efficiency as a function of the drift time. The three methods gave consistent results and indicated that no charge loss during the drift is observed for the sensor types used in 99% of the SDD modules mounted on the ALICE Inner Tracking System. The atmospheric muons have also been used to test the effect of the zero-suppression applied to reduce the data size by erasing the counts in cells not passing the thresholds for noise removal. As expected, the zero suppression introduces a dependence of the reconstructed charge as a function of drift time because it cuts the signal in the tails of the electron clouds enlarged by diffusion effects. These measurements allowed also to validate the correction for this effect extracted from detailed Monte Carlo simulations of the detector response and applied in the offline data reconstruction.

The discovery of the Higgs boson, a fundamental particle of the Standard Model, at the Large Hadron Collider (LHC) in 2012, marked a monumental milestone in the field of particle physics. Since then, extensive research has been conducted to understand the properties and interactions of the Higgs boson, particularly its couplings with other known particles. This article provides a review of the past, present, and future measurements of the Higgs boson couplings, with a focus on the most recent experimental developments. It discusses the experimental techniques and methods used to study the Higgs boson couplings, including the production and decay channels employed in various experiments. The article highlights the important relationships between the Higgs boson and other known particles, including the gauge bosons ( W and Z bosons), quarks, and leptons and the Higgs boson itself, through its self-interaction. After discussing the channels used by ATLAS and CMS collaborations to measure the Higgs boson coupling to the other standard model particles, the article will present an overview of the latest results obtained at the LHC, commenting on how various measurements have evolved over time along with a better comprehension of the detectors and ever more refined analysis techniques. Future collider developments and expectation for the measurement of the Higgs boson couplings and double-Higgs boson production with increased precision and accuracy will be discussed along with the main challenges faced by future experiments.

At LHC extreme values of energy density will be reached even for proton-proton collisions. Such values of energy density may be large enough to generate a collective motion in the products of the collision, therefore generating effects such as elliptic flow. Using ideal 3+1D hydrodynamical simulations, we show that elliptic flow can occur at least for top multiplicities p-p events at LHC and that the intensity of such effect is strongly related to quantum fluctuations in the initial proton energy distribution.

This document summarises the talks and discussions happened during the VBSCan Mid-Term Scientific Meeting workshop. The VBSCan COST action is dedicated to the coordinated study of vector boson scattering (VBS) from the phenomenological and experimental point of view, for the best exploitation of the data that will be delivered by existing and future particle colliders.

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

A measurement of inclusive four-jet production in proton-proton collisions at a center-of-mass energy of 13\TeV is presented. The transverse momenta of jets within $\lvert\eta\rvert \lt$ 4.7 reach down to 35, 30, 25, and 20 GeV for the first-, second-, third-, and fourth-leading jet, respectively. Differential cross sections are measured as functions of the jet transverse momentum, jet pseudorapidity, and several other observables that describe the angular correlations between the jets. The measured distributions show sensitivity to different aspects of the underlying event, parton shower, and matrix element calculations. In particular, the interplay between angular correlations caused by parton shower and double-parton scattering contributions is shown to be important. The double-parton scattering contribution is extracted by means of a template fit to the data, using distributions for single-parton scattering obtained from Monte Carlo event generators and a double-parton scattering distribution constructed from inclusive single-jet events in data. The effective double-parton scattering cross section is calculated and discussed in view of previous measurements and of its dependence on the models used to describe the single-parton scattering background.

Abstract The ALICE experiment is one of the four large experiments at the Large Hadron Collider (LHC), and it is dedicated to the study of ultra-relativistic heavy-ion collisions, with the goal of investigating the properties of the high-density state of QCD matter produced in these collisions. The study of D meson azimuthal anisotropy and the measurement of its elliptic flow ( ν 2 ) can provide insight on the degree of thermalisation of charm quarks in the medium and on the charm hadronization mechanism. We present the measurement of the D + and D 0 meson ν 2 in Pb–Pb collisions at s NN = 2.76 TeV at the LHC with ALICE. We discuss the details of the analysis and we show the results obtained from data samples collected in 2011.

A Large Ion Collider Experiment (ALICE) is one of the four large experiments at the Large Hadron Collider (LHC), and the one dedicated to ultra relativistic heavy ion collisions, aiming at investigating the properties of the high-density state of QCD matter produced in such events. ALICE started to collect data in proton-proton collisions at the LHC at CERN in November 2009 (with a centre of mass energy [Formula: see text]). Since March 2010 data are being recorded at an energy of [Formula: see text] while from November 7 to December 6 LHC provided Pb-Pb collisions at an energy of [Formula: see text] per nucleon-nucleon pair. In Pb-Pb collisions heavy quarks are regarded as sensitive probes of the interaction dynamics between the parton and medium produced in the collisions, and the energies available at LHC will allow to study the production of heavy flavours with high statistics. Proton-proton data will be used to measure the heavy flavours production cross section to compare with perturbative QCD calculations in an unexplored energy domain and they will provide the reference for the study of Pb-Pb collisions. After a description of the ALICE experiment focused on its heavy flavour related performance, the status of the first analysis on charm production, measured by reconstructing the decays of D 0 , D + , D* + , and D s into hadronic and semi-leptonic channels will be presented. An outlook of the same measurements for the upcoming Pb-Pb run will also be discussed.

The production of the pairs of Higgs bosons provides a direct handle on the structure of the Higgs field potential.While the HH production within the SM is very small and essentially out of the experimental reach within the Run I or II, several beyond SM theories foresee an enhancement that can be already probed with the available data.These proceedings detail the searches for double Higgs boson production performed at the Large Hadron Collider with the Compact Muon Solenoid experiment.Both resonant and non-resonant productions are discussed using final states in which one of the two Higgs bosons decays in a pair of b quarks, while the other can decay in pairs of τ, b, W or γ particles.Exclusion upper limits are set on the resonant and non-resonant double Higgs boson production cross-sections and on the presence of anomalous couplings affecting the non-resonant production.

This document reports the first year of activity of the VBSCan COST Action network, as summarised by the talks and discussions happened during the VBSCan Thessaloniki 2018 workshop. The VBSCan COST action is aiming at a consistent and coordinated study of vector-boson scattering from the phenomenological and experimental point of view, for the best exploitation of the data that will be delivered by existing and future particle colliders.

The discovery of the neutrino by Reines & Cowan in 1956 revolutionised our understanding of the universe at its most fundamental level and provided a new probe with which to explore the cosmos. Furthermore, it laid the groundwork for one of the most successful and widely used neutrino detection technologies to date: the liquid scintillator detector. In these detectors, the light produced by particle interactions propagates across transparent scintillator volumes to surrounding photo-sensors. This article introduces a new approach, called LiquidO, that breaks with the conventional paradigm of transparency by confining and collecting light near its creation point with an opaque scintillator and a dense array of fibres. The principles behind LiquidO's detection technique and the results of the first experimental validation are presented. The LiquidO technique provides high-resolution imaging that enables highly efficient identification of individual particles event-by-event. Additionally, the exploitation of an opaque medium gives LiquidO natural affinity for using dopants at unprecedented levels. With these and other capabilities, LiquidO has the potential to unlock new opportunities in neutrino physics, some of which are discussed here.

This document summarises the talks and discussions happened during the VBSCan Mid-Term Scientific Meeting workshop. The VBSCan COST action is dedicated to the coordinated study of vector boson scattering (VBS) from the phenomenological and experimental point of view, for the best exploitation of the data that will be delivered by existing and future particle colliders.

On July 4th, 2012 the ATLAS and CMS collaborations announced the discovery of a new Higgs-like resonance at a mass of about 126 GeV. To determine if the observed resonance is compatible with a SM Higgs boson, the resonance characteristics (mass, couplings, spin) must be measured with high precision. The ZZ channel (H → ZZ* → 4l, l = e,μ) is one of the most promising channels for these measurements. The CMS analysis H → ZZ* → 4l is presented, covering its most important aspects: lepton identification, isolation variables, kinematics, event selection, and background control. The talk presents the most recent CMS results on the search for the standard model Higgs boson in the ZZ channel, using the full dataset recorded at the LHC from pp collisions at centre of mass energies of 7 and 8 TeV. The properties of the new boson, such as the mass and spin, are discussed in detail.

A search for massive resonances decaying to a Z boson and a photon is performed in events with a hadronically decaying Z boson candidate, separately in light-quark and b quark decay modes, identified using jet substructure and advanced b tagging techniques. Results are based on samples of proton-proton collisions collected with the CMS detector at the LHC at center-of-mass energies of 8 and 13 TeV, corresponding to integrated luminosities of 19.7 and 2.7 inverse femtobarns, respectively. The results of the search are combined with those of a similar search in the leptonic decay modes of the Z boson, based on the same data sets. Spin-0 resonances with various widths and with masses in a range between 0.2 and 3.0 TeV are considered. No significant excess is observed either in the individual analyses or the combination. The results are presented in terms of upper limits on the production cross section of such resonances and constitute the most stringent limits to date for a wide range of masses.

The production of the pairs of Higgs bosons provides a direct handle on the structure of the Higgs field potential. While the HH production within the SM is very small and essentially out of the experimental reach within the Run I or II, several beyond SM theories foresee an enhancement that can be already probed with the available data. These proceedings detail the searches for double Higgs boson production performed at the Large Hadron Collider with the Compact Muon Solenoid experiment. Both resonant and non-resonant productions are discussed using final states in which one of the two Higgs bosons decay in a pair of b quarks, while the other can decay in pairs of $\tau$, b, W or $\gamma$ particles. Exclusion upper limits are set on the resonant and non-resonant double Higgs boson production cross-sections and on the presence of anomalous couplings affecting the non-resonant production.

The inelastic hadronic cross section in proton-lead collisions at a centre-of-mass energy per nucleon pair of 5.02 TeV is measured with the CMS detector at the LHC. The data sample, corresponding to an integrated luminosity of 12.6 +/- 0.4 inverse nanobarns, has been collected with an unbiased trigger for inclusive particle production. The cross section is obtained from the measured number of proton-lead collisions with hadronic activity produced in the pseudorapidity ranges 3<abs(eta)<5 and/or -5<abs(eta)<-3, corrected for photon-induced contributions, experimental acceptance, and other instrumental effects. The inelastic cross section is measured to be sigma[inel,pPb]=2061 +/- 3 (stat) +/- 34 (syst) +/- 72 (lum) mb. Various Monte Carlo generators, commonly used in heavy ion and cosmic ray physics, are found to reproduce the data within uncertainties. The value of sigma[inel,pPb] is compatible with that expected from the proton-proton cross section at 5.02 TeV scaled up within a simple Glauber approach to account for multiple scatterings in the lead nucleus, indicating that further net nuclear corrections are small.

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation Giacomo Ortona, ALICE Collaboration; D meson analysis in Pb-Pb collisions at SNN = 2.76 TeV at the LHC with ALICE. AIP Conf. Proc. 14 March 2012; 1422 (1): 127–134. https://doi.org/10.1063/1.3692207 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAIP Publishing PortfolioAIP Conference Proceedings Search Advanced Search |Citation Search

A Large Ion Collider Experiment (ALICE) is one of the four large experiments at the Large Hadron Collider (LHC), and it is dedicated to the study of ultra-relativistic heavy-ion collisions, with the goal of investigating the properties of the high-density state of QCD matter produced in these collisions. The study of D meson production azimuthal anisotropy and the measurement of their elliptic flow (v2) can provide insight on the degree of thermalisation of charm quarks in the medium and on the charm hadronization mechanism. We present the measurement of the D+ and D0 meson v2 in Pb-Pb collisions at sqrt(sNN)=2.76 TeV at the LHC with ALICE. We discuss the details of the analysis and we show the results obtained from data samples collected in 2011.

The extremely high energies that will be reached with the Large Hadron Collider (LHC) at CERN will allow studying the production of open charm with high statistics in both proton-proton and Pb-Pb collisions. The study of open charm (D) mesons in Pb-Pb collisions will be a powerful tool to investigate the production of heavy flavours and their interaction with the medium produced in such collisions (QGP). Heavy flavour yields will provide also a normalization for quarkonia production. We will present a general overview of the ALICE collaboration heavy flavour program, then we will focus on the analysis and reconstruction strategies developed for the study of the charmed (D) mesons by the ALICE collaboration for proton-proton collisions, with special emphasis on the charged D mesons. Finally, some expected results obtained with MonteCarlo production will be shown.

Charge-dependent anisotropy Fourier coefficients ($v_n$) of particle azimuthal distributions are measured in pPb and PbPb collisions at $ \sqrt{\smash[b]{s_{_{\mathrm{NN}}}}} = $ 5.02 TeV with the CMS detector at the LHC. The normalized difference in the second-order anisotropy coefficients ($v_2$) between positively and negatively charged particles is found to depend linearly on the observed event charge asymmetry with comparable slopes for both pPb and PbPb collisions over a wide range of charged particle multiplicity. In PbPb, the third-order anisotropy coefficient, $v_3$, shows a similar linear dependence with the same slope as seen for $v_2$. The observed similarities between the $v_2$ slopes for pPb and PbPb, as well as the similar slopes for $v_2$ and $v_3$ in PbPb, are compatible with expectations based on local charge conservation in the decay of clusters or resonances, and constitute a challenge to the hypothesis that the observed charge asymmetry dependence of $v_2$ in heavy ion collisions arises from a chiral magnetic wave.

A measurement of the ttbar production cross section at sqrt(s)=13 TeV is presented using proton-proton collisions, corresponding to an integrated luminosity of 2.3 inverse femtobarns, collected with the CMS detector at the LHC. Final states with one isolated charged lepton (electron or muon) and at least one jet are selected and categorized according to the accompanying jet multiplicity. From a likelihood fit to the invariant mass distribution of the isolated lepton and a jet identified as coming from the hadronization of a bottom quark, the cross section is measured to be sigma(ttbar)= 835 +/- 3 (stat) +/- 23 (syst) +/- 23 (lum) pb, in agreement with the standard model prediction. Using the expected dependence of the cross section on the pole mass of the top quark (m[t]), the value of m[t] is found to be 172.7+2.4-2.7 GeV.

The extremely high energies that will be reached at the Large Hadron Collider (LHC) at CERN will allow studying the production of heavy flavours (beauty and charm) with high statistics in both proton-proton and Pb-Pb collisions.The study of open charm (D) and beauty (B) mesons in Pb-Pb collisions will be a powerful tool to investigate the production of heavy flavours and their interaction with the medium produced in such collisions (QGP).Heavy flavour yields will provide also a normalization for quarkonia production.We will present a general overview of the ALICE collaboration heavy flavour program, then we will focus on the analysis and reconstruction strategies developed for the study of the charmed (D) mesons by the ALICE collaboration for proton-proton collisions, with special emphasis on the charged D mesons.Finally, some expected results obtained with MonteCarlo production will be shown.

The strong Coulomb field created in ultrarelativistic heavy ion collisions is expected to produce a rapidity-dependent difference ($\Delta v_2$) in the second Fourier coefficient of the azimuthal distribution (elliptic flow, $v_2$) between $\mathrm{D}^0$ ($\mathrm{\bar{u}c}$) and $\overline{\mathrm{D}}^0$ ($\mathrm{u\bar{c}}$) mesons. Motivated by the search for evidence of this field, the CMS detector at the LHC is used to perform the first measurement of $\Delta v_2$. The rapidity-averaged value is found to be $\langle\Delta v_2 \rangle =$ 0.001 $\pm$ 0.001 (stat) $\pm$ 0.003 (syst) in PbPb collisions at $\sqrt{s_\mathrm{NN}} =$ 5.02 TeV. In addition, the influence of the collision geometry is explored by measuring the $\mathrm{D}^0$ and $\overline{\mathrm{D}}^0$ mesons $v_2$ and triangular flow coefficient ($v_3$) as functions of rapidity, transverse momentum ($p_\mathrm{T}$), and event centrality (a measure of the overlap of the two Pb nuclei). A clear centrality dependence of prompt $\mathrm{D}^0$ meson $v_2$ values is observed, while the $v_3$ is largely independent of centrality. These trends are consistent with expectations of flow driven by the initial-state geometry.

This document reports the first year of activity of the VBSCan COST Action network, as summarised by the talks and discussions happened during the VBSCan Thessaloniki 2018 workshop. The VBSCan COST action is aiming at a consistent and coordinated study of vector-boson scattering from the phenomenological and experimental point of view, for the best exploitation of the data that will be delivered by existing and future particle colliders.

This document reports the first year of activity of the VBSCan COST Action network, as summarised by the talks and discussions happened during the VBSCan Thessaloniki 2018 workshop. The VBSCan COST action is aiming at a consistent and coordinated study of vector-boson scattering from the phenomenological and experimental point of view, for the best exploitation of the data that will be delivered by existing and future particle colliders.

This document reports the first year of activity of the VBSCan COST Action network, as summarised by the talks and discussions happened during the VBSCan Thessaloniki 2018 workshop. The VBSCan COST action is aiming at a consistent and coordinated study of vector-boson scattering from the phenomenological and experimental point of view, for the best exploitation of the data that will be delivered by existing and future particle colliders.

CERN-ACC-2018-004517 March 2019Higgs and Electro-weak symmetry breaking at the FCC-hhL. Borgonovi∗, S. Braibant∗, B. Di Micco†, E. Fontanesi∗, P. Harris‡, C. Helsens§, D. Jamin§,M.L. Mangano§, G. Ortona¶, M. Selvaggi1)§, A. Sznajder‖, M. Testa¶, M. Verducci¶On behalf of the FCC-hh Collaboration∗Universita di Bologna, Italy,†Universita degli Studi Roma Tre, Italy,‡Massachusetts Institute of Technology (MIT), Cambridge, USA,§European Organization for Nuclear Research (CERN), Geneva, Switzerland,¶Laboratoire Leprince-Ringuet, Ecole Polytechnique (LLR), Palaiseau, France,‖Universidade do Estado do Rio de Janeiro (UERJ), Rio de Janeiro, BrazilAbstractThe future circular hadron-hadron collider FCC-hh is expected to produce collisions at thecenter of mass energy of√s=100 TeV and to deliver an integrated luminosity of 30 ab−1.The Higgs-self coupling will be measured with a 5% precision via double Higgs production.Tens of billions of Higgs bosons will be produced at the FCC-hh. Such large statisticswill allow for a wide range of possibilities in the realm of precision Higgs measurements.Several Higgs couplings will be measured to a percent level precision, including the secondgeneration muon yukawa coupling. The Higgs to invisible branching fraction will be probedto a level of few 10−4and the rate of longitudinally polarized vector bosons produced invector boson scattering will be measured with 2% precision.

A measurement of the top quark mass is performed using a data sample enriched with single top quark events produced in the $t$ channel. The study is based on proton-proton collision data, corresponding to an integrated luminosity of 35.9 fb$^{-1}$, recorded at $\sqrt{s}$ = 13 TeV by the CMS experiment at the LHC in 2016.Candidate events are selected by requiring an isolated high-momentum lepton (muon or electron) and exactly two jets, of which one is identified as originating from a bottom quark. Multivariate discriminants are designed to separate the signal from the background. Optimized thresholds are placed on the discriminant outputs to obtain an event sample with high signal purity. The top quark mass is found to be 172.13$^{+0.76}_{-0.77}$ GeV, where the uncertainty includes both the statistical and systematic components, reaching sub-GeV precision for the first time in this event topology. The masses of the top quark and antiquark are also determined separately using the lepton charge in the final state, from which the mass ratio and difference are determined to be 0.9952$^{+0.0079}_{-0.0104}$ and 0.83$^{+1.79}_{-1.35}$ GeV, respectively. The results are consistent with $CPT$ invariance.

Measurements of the inclusive and differential fiducial cross sections of the Higgs boson are presented, using the $\tau$ lepton decay channel. The differential cross sections are measured as functions of the Higgs boson transverse momentum, jet multiplicity, and transverse momentum of the leading jet in the event if any. The analysis is performed using proton-proton data collected with the CMS detector at the LHC at a center-of-mass energy of 13 TeV and corresponding to an integrated luminosity of 138 fb$^{-1}$. These are the first differential measurements of the Higgs boson cross section in the final state of two $\tau$ leptons, and they constitute a significant improvement over measurements in other final states in events with a large jet multiplicity or with a Lorentz-boosted Higgs boson.

The associated production of a W and a Z boson is studied in final states with multiple leptons produced in proton-proton (pp) collisions at a centre-of-mass energy of 13 TeV using 137 fb$^{-1}$ of data collected with the CMS detector at the LHC. A measurement of the total inclusive production cross section yields $\sigma_{\text{tot}}$(pp $\to$ WZ) = 50.6 $\pm$ 0.8 (stat) $\pm$ 1.5 (syst) $\pm$ 1.1 (lum) $\pm$ 0.5 (thy) pb. Measurements of the fiducial and differential cross sections for several key observables are also performed in all the final-state lepton flavour and charge compositions with a total of three charged leptons, which can be electrons or muons. All results are compared with theoretical predictions computed up to next-to-next-to-leading order in quantum chromodynamics plus next-to-leading order in electroweak theory and for various sets of parton distribution functions. The results include direct measurements of the charge asymmetry and the W and Z vector boson polarization. The first observation of longitudinally polarized W bosons in WZ production is reported. Anomalous gauge couplings are searched for, leading to new constraints on beyond-the-standard-model contributions to the WZ triple gauge coupling.

A search for new long-lived particles decaying to leptons using proton-proton collision data produced by the CERN LHC at $\sqrt{s}$ = 13 TeV is presented. Events are selected with two leptons (an electron and a muon, two electrons, or two muons) that both have transverse impact parameter values between 0.01 and 10 cm and are not required to form a common vertex. Data used for the analysis were collected with the CMS detector in 2016, 2017, and 2018, and correspond to an integrated luminosity of 118 (113) fb$^{-1}$ in the ee channel (e$\mu$ and $\mu\mu$ channels). The search is designed to be sensitive to a wide range of models with displaced e$\mu$, ee, and $\mu\mu$ final states. The results constrain several well-motivated models involving new long-lived particles that decay to displaced leptons. For some areas of the available phase space, these are the most stringent constraints to date.

The CMS experiment at the LHC has measured the differential cross sections of Z bosons decaying to pairs of leptons, as functions of transverse momentum and rapidity, in lead-lead collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV. The measured Z boson elliptic azimuthal anisotropy coefficient is compatible with zero, showing that Z bosons do not experience significant final-state interactions in the medium produced in the collision. Yields of Z bosons are compared to Glauber model predictions and are found to deviate from these expectations in peripheral collisions, indicating the presence of initial collision geometry and centrality selection effects. The precision of the measurement allows, for the first time, for a data-driven determination of the nucleon-nucleon integrated luminosity as a function of lead-lead centrality, thereby eliminating the need for its estimation based on a Glauber model.

Measurements of differential and double-differential cross sections of top quark pair ($\text{t}\overline{\text{t}}$) production are presented in the lepton+jets channels with a single electron or muon and jets in the final state. The analysis combines for the first time signatures of top quarks with low transverse momentum $p_\text{T}$, where the top quark decay products can be identified as separated jets and isolated leptons, and with high $p_\text{T}$, where the decay products are collimated and overlap. The measurements are based on proton-proton collision data at $\sqrt{s} = $ 13 TeV collected by the CMS experiment at the LHC, corresponding to an integrated luminosity of 137 fb$^{-1}$. The cross sections are presented at the parton and particle levels, where the latter minimizes extrapolations based on theoretical assumptions. Most of the measured differential cross sections are well described by standard model predictions with the exception of some double-differential distributions. The inclusive $\text{t}\overline{\text{t}}$ production cross section is measured to be $\sigma_{\text{t}\overline{\text{t}}} = $ 791 $\pm$ 25 pb, which constitutes the most precise measurement in the lepton+jets channel to date.