18 research outputs found
Use of a Multi-sensor Technique to Monitor the Mould Oscillation in a Continuous Billet Caster
- Publication venue
- 'Iron and Steel Institute of Japan'
- Publication date
- 01/01/2006
- Field of study
Effect of C and Mn Variations Upon the Solidification Mode and Surface Cracking Susceptibility of Peritectic Steels
- Author
- Publication venue
- 'Iron and Steel Institute of Japan'
- Publication date
- 01/01/2009
- Field of study
Performance of the CMS Level-1 trigger in proton-proton collisions at root s=13 TeV
- Publication venue
- Publication date
- 01/01/2020
- Field of study
At the start of Run 2 in 2015, the LHC delivered proton-proton
collisions at a center-ofmass energy of 13 TeV. During Run 2 (years
2015-2018) the LHC eventually reached a luminosity of 2.1 x 10(34)
cm(-2) s(-1), almost three times that reached during Run 1 (2009-2013)
and a factor of two larger than the LHC design value, leading to events
with up to a mean of about 50 simultaneous inelastic proton-proton
collisions per bunch crossing (pileup). The CMS Level-1 trigger was
upgraded prior to 2016 to improve the selection of physics events in the
challenging conditions posed by the second run of the LHC. This paper
describes the performance of the CMS Level-1 trigger upgrade during the
data taking period of 2016-2018. The upgraded trigger implements pattern
recognition and boosted decision tree regression techniques for muon
reconstruction, includes pileup subtraction for jets and energy sums,
and incorporates pileup-dependent isolation requirements for electrons
and tau leptons. In addition, the new trigger calculates high-level
quantities such as the invariant mass of pairs of reconstructed
particles. The upgrade reduces the trigger rate from background
processes and improves the trigger efficiency for a wide variety of
physics signals
Running of the top quark mass from proton-proton collisions at root s=13 TeV
- Publication venue
- Publication date
- 01/01/2020
- Field of study
The running of the top quark mass is experimentally investigated for the
first time. The mass of the top quark in the modified minimal
subtraction ((MS) over bar) renormalization scheme is extracted from a
comparison of the differential top quark-antiquark (t (t) over bar)
cross section as a function of the invariant mass of the t (t) over bar
system to next-to-leading-order theoretical predictions. The
differential cross section is determined at the parton level by means of
a maximum-likelihood fit to distributions of final-state observables.
The analysis is performed using t (t) over bar candidate events in the
e(+/-)mu(-/+) channel in proton-proton collision data at a
centre-of-mass energy of 13 TeV recorded by the CMS detector at the CERN
LHC in 2016, corresponding to an integrated luminosity of 35.9 fb(-1).
The extracted running is found to be compatible with the scale
dependence predicted by the corresponding renormalization group
equation. In this analysis, the running is probed up to a scale of the
order of 1 TeV. (C) 2020 The Author(s). Published by Elsevier B.V
Measurement of b jet shapes in proton-proton collisions at root s=5.02 TeV
- Publication venue
- Publication date
- 01/01/2021
- Field of study
We present the first study of charged-hadron production associated with
jets originating from b quarks in proton-proton collisions at a
center-of-mass energy of 5.02 TeV. The data sample used in this study
was collected with the CMS detector at the CERN LHC and corresponds to
an integrated luminosity of 27.4 pb(-1). To characterize the jet
substructure, the differential jet shapes, defined as the normalized
transverse momentum distribution of charged hadrons as a function of
angular distance from the jet axis, are measured for b jets. In addition
to the jet shapes, the per-jet yields of charged particles associated
with b jets are also quantified, again as a function of the angular
distance with respect to the jet axis. Extracted jet shape and particle
yield distributions for b jets are compared with results for inclusive
jets, as well as with the predictions from the pythia and herwig++ event
generators
Search for direct top squark pair production in events with one lepton, jets, and missing transverse momentum at 13 TeV with the CMS experiment
- Publication venue
- Publication date
- 01/01/2020
- Field of study
A search for direct top squark pair production is presented. The search
is based on proton-proton collision data at a center-of-mass energy of
13 TeV recorded by the CMS experiment at the LHC during 2016, 2017, and
2018, corresponding to an integrated luminosity of 137 fb(-1). The
search is carried out using events with a single isolated electron or
muon, multiple jets, and large transverse momentum imbalance. The
observed data are consistent with the expectations from standard model
processes. Exclusions are set in the context of simplified top squark
pair production models. Depending on the model, exclusion limits at 95%
confidence level for top squark masses up to 1.2 TeV are set for a
massless lightest supersymmetric particle, assumed to be the neutralino.
For models with top squark masses of 1 TeV, neutralino masses up to 600
GeV are excluded
Correlations of azimuthal anisotropy Fourier harmonics with subevent cumulants in pPb collisions at root s(NN)=8.16 TeV
- Publication venue
- Publication date
- 01/01/2021
- Field of study
Event-by-event long-range correlations of azimuthal anisotropy Fourier
coefficients (v(n)) in 8.16 TeV pPb data, collected by the CMS
experiment at the CERN Large Hadron Collider, are extracted using a
subevent four-particle cumulant technique applied to very low
multiplicity events. Each combination of four charged particles is
selected from either two, three, or four distinct subevent regions of a
pseudorapidity range from -2.4 to 2.4 of the CMS tracker, and with
transverse momentum between 0.3 and 3.0 GeV. Using the subevent cumulant
technique, correlations between v(n) of different orders are measured as
functions of particle multiplicity and compared to the standard cumulant
method without subevents over a wide event multiplicity range. At high
multiplicities, the v(2) and v(3) coefficients exhibit an
anticorrelation; this behavior is observed consistently using various
methods. The v(2) and v(4) correlation strength is found to depend on
the number of subevents used in the calculation. As the event
multiplicity decreases, the results from different subevent methods
diverge because of different contributions of noncollective or
few-particle correlations. Correlations extracted with the four-subevent
method exhibit a tendency to diminish monotonically toward the lowest
multiplicity region (about 20 charged tracks) investigated. These
findings extend previous studies to a significantly lower event
multiplicity range and establish the evidence for the onset of
long-range collective multiparticle correlations in small system
collisions
Mixed higher-order anisotropic flow and nonlinear response coefficients of charged particles in PbPb collisions at root s(NN)=2.76 and 5.02 TeV
- Publication venue
- Publication date
- 01/01/2020
- Field of study
Anisotropies in the initial energy density distribution of the
quark-gluon plasma created in high energy heavy ion collisions lead to
anisotropies in the azimuthal distributions of the final-state particles
known as collective anisotropic flow. Fourier harmonic decomposition is
used to quantify these anisotropies. The higher-order harmonics can be
induced by the same order anisotropies (linear response) or by the
combined influence of several lower order anisotropies (nonlinear
response) in the initial state. The mixed highe-rorder anisotropic flow
and nonlinear response coefficients of charged particles are measured as
functions of transverse momentum and centrality in PbPb collisions at
nucleon-nucleon center-of-mass energies root s(NN) = 2.76 and 5.02 TeV
with the CMS detector. The results are compared with viscous
hydrodynamic calculations using several different initial conditions,
aswell asmicroscopic transport model calculations. None of the models
provides a simultaneous description of the mixed higher-order flow
harmonics and nonlinear response coefficients
Measurement of the azimuthal anisotropy of Y(1S) and Y(2S) mesons in PbPb collisions at root s(NN)=5.02 TeV
- Publication venue
- Publication date
- 01/01/2021
- Field of study
The second-order Fourier coefficients (v(2)) characterizing the
azimuthal distributions of Y(1S) and Y(2S) mesons produced in PbPb
collisions at root s(NN) = 5.02 TeV are studied. The Y mesons are
reconstructed in their dimuon decay channel, as measured by the CMS
detector. The collected data set corresponds to an integrated luminosity
of 1.7 nb(-1). The scalar product method is used to extract the v2
coefficients of the azimuthal distributions. Results are reported for
the rapidity range vertical bar y vertical bar < 2.4, in the transverse
momentum interval 0 < pT < 50 GeV/c, and in three centrality ranges of
10-30%, 30-50% and 50-90%. In contrast to the J/psi mesons, the
measured v(2) values for the Y mesons are found to be consistent with
zero. (C) 2021 The Author(s). Published by Elsevier B.V
Search for a heavy pseudoscalar boson decaying to a Z and a Higgs boson at root s=13TeV
- Publication venue
- Publication date
- 01/01/2019
- Field of study
A search is presented for a heavy pseudoscalar boson A decaying to a Z
boson and a Higgs boson with mass of 125 GeV. In the final state
considered, the Higgs boson decays to a bottom quark and antiquark, and
the Z boson decays either into a pair of electrons, muons, or neutrinos.
The analysis is performed using a data sample corresponding to an
integrated luminosity of 35.9 fb-1 collected in 2016 by the CMS
experiment at the LHC from proton-proton collisions at a center-of-mass
energy of 13 Te. The data are found to be consistent with the background
expectations. Exclusion limits are set in the context of
two-Higgs-doublet models in the A boson mass range between 225 and 1000