Prospects for γγ→H\gamma \gamma \to H and γγ→W+W−\gamma \gamma \to W^{+}W^{-} measurements at the FCC-ee

We study the possibilities for the measurement of two-photon production of the Higgs boson (in the $b \bar{b}$ decay channel), and of $W^{+}W^{-}$ pairs (decaying into four jets) in $e^{+}e^{-}$ collisions at the the Future Circular Collider (FCC-ee). The processes are simulated with the PYTHIA and MADGRAPH 5 Monte Carlo codes, using the effective photon approximation for the $e^{+}e^{-}$ photon fluxes, at center-of-mass energies $\sqrt{s} =$ 160 GeV and 240 GeV. The analyses include electron-positron tagging, realistic acceptance and reconstruction efficiencies for the final-state jets, and selection criteria to remove the backgrounds. Observation of both channels is achievable with the expected few ab$^{-1}$ integrated luminosities at FCC-ee.Comment: Proceedings of the conference PHOTON 2015: International Conference on the Structure and the Interactions of the Photon including the 21th International Workshop on Photon-Photon Collisions and the International Workshop on High Energy Photon Colliders, held at Budker Institute of Nuclear Physics (BINP), Siberian Branch of Russian Academy of Science, Novosibirsk, Russia, from 15 to 19 June, 201

Sharpening the shape analysis for higher-dimensional operator searches

When the Standard Model is interpreted as the renormalizable sector of a low-energy effective theory, the effects of new physics are encoded into a set of higher dimensional operators. These operators potentially deform the shapes of Standard Model differential distributions of final states observable at colliders. We describe a simple and systematic method to obtain optimal estimations of these deformations when using numerical tools, like Monte Carlo simulations. A crucial aspect of this method is minimization of the estimation uncertainty: we demonstrate how the operator coefficients have to be set in the simulations in order to get optimal results. The uncertainty on the interference term turns out to be the most difficult to control and grows very quickly when the interference is suppressed. We exemplify our method by computing the deformations induced by the ${\cal O}_{3W}$ operator in $W^+W^-$ production at the LHC, and by deriving a bound on ${\cal O}_{3W}$ using $8$ TeV CMS data.Comment: 21 pages, 4 figures. v2: Minor corrections, references added, matches journal versio

Prospects for γγ→\gamma\gamma\to Higgs observation in ultraperipheral ion collisions at the Future Circular Collider

We study the two-photon production of the Higgs boson, $\rm \gamma\gamma\to H$, at the Future Circular Collider (FCC) in ultraperipheral PbPb and pPb collisions at $\sqrt{s_{NN}} = 39$ and 63 TeV. Signal and background events are generated with MADGRAPH 5, including $\gamma$ fluxes from the proton and lead ions in the equivalent photon approximation, yielding $\rm \sigma(\gamma\gamma\to H)$ = 1.75 nb and 1.5 pb in PbPb and pPb collisions respectively. We analyse the H$\,\to b\bar{b}$ decay channel including realistic reconstruction efficiencies for the final-state $b$-jets, showered and hadronized with PYTHIA 8, as well as appropriate selection criteria to reduce the dominant exclusive $\gamma\gamma\to b\bar{b}$ continuum background. Observation of $\rm PbPb\xrightarrow{\gamma\gamma}(Pb)\,H\,(Pb)$ is achievable in the first year with the expected PbPb integrated luminosities.Comment: 5 pages, 4 figures. PHOTON'17, CERN Proceedings, to appear. References adde

Searches for axion-like particles via γγ\gamma \gamma fusion at future e+e−\mathrm{e}^+\mathrm{e}^- colliders

Opportunities for searches for axion-like particles (ALPs) coupling to photons in $\mathrm{e}^+\mathrm{e}^-$ collisions at the Future Circular Collider (FCC-ee) and International Linear Collider (ILC) are investigated. We perform a study of the photon-fusion production of ALPs decaying into two photons, $\mathrm{e}^+\mathrm{e}^- \overset{\gamma \gamma}{\longrightarrow} \mathrm{e}^{+}\;a(\gamma \gamma)\;\mathrm{e}^{-}$, over the light-by-light continuum background, for the planned FCC-ee and ILC center-of-mass energies and integrated luminosities. An analysis of the feasibility measurements is presented using parametrized simulations for two types of detectors. Upper limits at 95% confidence level (CL) on the cross section for ALP production, $\sigma(\gamma \gamma \to a \to \gamma \gamma)$, and on the ALP-photon coupling are obtained over the $m_a \approx 0.1$--1000 GeV ALP mass range, and compared to current and future collider searches. Production cross sections down to $\sigma(\gamma \gamma \to a \to \gamma \gamma) \approx 1$ fb (1 ab) will be probed at $m_a\approx 1$ (300) GeV, corresponding to constraints on the axion-photon coupling as low as $g_\mathrm{a\gamma \gamma} \approx 2\cdot10^{-3}$ TeV$^{-1}$

Measurement of differential cross sections for top quark pair production using the lepton plus jets final state in proton-proton collisions at 13 TeV

National Science Foundation (U.S.

Particle-flow reconstruction and global event description with the CMS detector

The CMS apparatus was identified, a few years before the start of the LHC operation at CERN, to feature properties well suited to particle-flow (PF) reconstruction: a highly-segmented tracker, a fine-grained electromagnetic calorimeter, a hermetic hadron calorimeter, a strong magnetic field, and an excellent muon spectrometer. A fully-fledged PF reconstruction algorithm tuned to the CMS detector was therefore developed and has been consistently used in physics analyses for the first time at a hadron collider. For each collision, the comprehensive list of final-state particles identified and reconstructed by the algorithm provides a global event description that leads to unprecedented CMS performance for jet and hadronic tau decay reconstruction, missing transverse momentum determination, and electron and muon identification. This approach also allows particles from pileup interactions to be identified and enables efficient pileup mitigation methods. The data collected by CMS at a centre-of-mass energy of 8 TeV show excellent agreement with the simulation and confirm the superior PF performance at least up to an average of 20 pileup interactions

Identification of heavy-flavour jets with the CMS detector in pp collisions at 13 TeV

Many measurements and searches for physics beyond the standard model at the LHC rely on the efficient identification of heavy-flavour jets, i.e. jets originating from bottom or charm quarks. In this paper, the discriminating variables and the algorithms used for heavy-flavour jet identification during the first years of operation of the CMS experiment in proton-proton collisions at a centre-of-mass energy of 13 TeV, are presented. Heavy-flavour jet identification algorithms have been improved compared to those used previously at centre-of-mass energies of 7 and 8 TeV. For jets with transverse momenta in the range expected in simulated $\mathrm{t}\overline{\mathrm{t}}$ events, these new developments result in an efficiency of 68% for the correct identification of a b jet for a probability of 1% of misidentifying a light-flavour jet. The improvement in relative efficiency at this misidentification probability is about 15%, compared to previous CMS algorithms. In addition, for the first time algorithms have been developed to identify jets containing two b hadrons in Lorentz-boosted event topologies, as well as to tag c jets. The large data sample recorded in 2016 at a centre-of-mass energy of 13 TeV has also allowed the development of new methods to measure the efficiency and misidentification probability of heavy-flavour jet identification algorithms. The heavy-flavour jet identification efficiency is measured with a precision of a few per cent at moderate jet transverse momenta (between 30 and 300 GeV) and about 5% at the highest jet transverse momenta (between 500 and 1000 GeV)