Suyong Choi

Since the discovery of the Higgs boson in 2012, detailed studies of its properties have been ongoing. Besides its mass, its width - related to its lifetime - is an important parameter. One way to determine this quantity is by measuring its off-shell production, where the Higgs boson mass is far away from its nominal value, and relating it to its on-shell production, where the mass is close to the nominal value. Here, we report evidence for such off-shell contributions to the production cross sec

Abstract The performance of muon tracking, identification, triggering, momentum resolution, and momentum scale has been studied with the CMS detector at the LHC using data collected at √( s NN ) = 5.02 TeV in proton-proton (pp) and lead-lead (PbPb) collisions in 2017 and 2018, respectively, and at √( s NN ) = 8.16 TeV in proton-lead (pPb) collisions in 2016. Muon efficiencies, momentum resolutions, and momentum scales are compared by focusing on how the muon reconstruction performance varies fro

A measurement of the production cross section of a Higgs boson with transverse momentum greater than 250 GeV is presented where the Higgs boson decays to a pair of τ leptons. It is based on proton-proton collision data collected by the CMS experiment at the CERN LHC at a center-of-mass energy of 13 TeV. The data sample corresponds to an integrated luminosity of 138 fb − 1 . Because of the large transverse momentum of the Higgs boson the τ leptons from its decays are boosted and produced spatiall

A bstract A search for t -channel exchange of leptoquarks (LQs) is performed in dimuon and dielectron spectra using proton-proton collision data collected at $$\sqrt{s}=13$$ TeV with the CMS detector at the CERN LHC. The data correspond to an integrated luminosity of 138 fb − 1 . Eight scenarios are considered, in which up or down quarks couple to muons or electrons via a scalar or vector LQ exchange, for dilepton invariant masses above 500 GeV. The LQ masses are probed up to 5 TeV, beyond a reg

Data analyses in particle physics rely on an accurate simulation of particle collisions and a detailed simulation of detector effects to extract physics knowledge from the recorded data. Event generators together with a GEANT-based simulation of the detectors are used to produce large samples of simulated events for analysis by the LHC experiments. These simulations come at a high computational cost, where the detector simulation and reconstruction algorithms have the largest CPU demands. This a

A bstract The results of a search for the production of two scalar bosons in final states with two photons and two tau leptons are presented. The search considers both nonresonant production of a Higgs boson pair, HH, and resonant production via a new boson X which decays either to HH or to H and a new scalar Y. The analysis uses up to 138 fb − 1 of proton-proton collision data, recorded between 2016 and 2018 by the CMS experiment at the LHC at a center-of-mass energy of 13 TeV. No evidence for

This Letter reports the first measurement of photonuclear D^{0} meson production in ultraperipheral heavy ion collisions. The study is performed using lead-lead collision data, with an integrated luminosity of 1.34 nb^{-1}, collected by the CMS experiment at a nucleon-nucleon center-of-mass energy of 5.36 TeV. Photonuclear events, where one of the colliding nuclei breaks up and the other remains intact, are selected based on breakup neutron emissions and by requiring no particle activity in a la

A large number of top quarks will be produced at the Large Hadron Collider (LHC) during the Run II period. This will allow us to measure the rare processes from the top sector in great details. We present a study of top-quark pair production in association with a bottom-quark pair (t¯tb¯b) from fast simulations for the Compact Muon Solenoid (CMS) experiment. The differential distributions of t¯tb¯b are compared with the top-quark pair production with two additional jets (t¯tjj) and with the prod

Searches are presented for heavy scalar ($\mathrm{H}$) and pseudoscalar ($\mathrm{A}$) Higgs bosons posited in the two doublet model (2HDM) extensions of the standard model (SM). These searches are based on a data sample of $\mathrm{p}\mathrm{p}$ collisions collected with the CMS experiment at the LHC at a center-of-mass energy of $\sqrt{s} = 8~\mathrm{TeV}$ and corresponding to an integrated luminosity of $19.5~\mathrm{fb}^{-1}$. The decays $\mathrm{H} \rightarrow \mathrm{h} \mathrm{h}$ and $\m

A bstract Precision measurements of Higgs boson differential production cross sections are a key tool to probe the properties of the Higgs boson and test the standard model. New physics can affect both Higgs boson production and decay, leading to deviations from the distributions that are expected in the standard model. In this paper, combined measurements of differential spectra in a fiducial region matching the experimental selections are performed, based on analyses of four Higgs boson decay

A novel machine-learning-based flavor-tagging algorithm combining same-side and opposite-side tagging is used to obtain the equivalent of 27 500 tagged B_{s}^{0}→J/ψϕ(1020) decays from pp collisions at sqrt[s]=13 TeV, collected by the CMS experiment and corresponding to an integrated luminosity of 96.5 fb^{-1}. A time- and flavor-dependent angular analysis of the μ^{+}μ^{-}K^{+}K^{-} final state, consistent with a ϕ(1020)→K^{+}K^{-} decay, is used to measure parameters of the B_{s}^{0}-B[over ¯]

Silicon sensors with 3-D structures are expected to tolerate radiation levels higher than those of sensors based on normal planar technologies. We studied the performance of a single-sided 3-D silicon pixel-type sensor by using 3-D semiconductor simulation tools. We expect the 3-D silicon detector to have good charge collection efficiency and position resolution.

For the Heavy Ion Accelerator Project in South Korea we designed an optimized antimuon beamlineby using a simulation with the G4beamline and the TRANSPORT software packages. Thisresearch suggests that the optimized muon beamline can transport 2.4×108 antimuons per secondto a circle with a radius of 3 cm. In terms of the muon rate, this is competitive with world-leadingmuon beam facilities.

Recent astrophysical observations provided indirect evidences for sub-GeV, light, dark-matter (DM). A new gauge particle in this mass range could exist as an extra $U(1)$ gauge particle, called the dark photon. The dark photon can mix weakly with a ordinary photon and can mediate interactions of DM. If the dark photon is massive enough, it can decay into a pair of standard-model (SM) particles or DM particles. Light dark-matter particles in the MeV to GeV mass range, as well as in other mass ran

A search for Higgs boson pair (HH) production with one Higgs boson decaying to two bottom quarks and the other to two W bosons are presented. The search is done using proton-proton collisions data at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb$^{-1}$ recorded by the CMS detector at the LHC from 2016 to 2018. The final states considered include at least one leptonically decaying W boson. No evidence for the presence of a signal is observed and correspond