I. Krätschmer
A5083183920- Particle physics theoretical and experimental studies
- High-Energy Particle Collisions Research
- Quantum Chromodynamics and Particle Interactions
- Particle Detector Development and Performance
- Dark Matter and Cosmic Phenomena
- Cosmology and Gravitation Theories
- Computational Physics and Python Applications
- Neutrino Physics Research
- Astrophysics and Cosmic Phenomena
- Black Holes and Theoretical Physics
- Medical Imaging Techniques and Applications
- Distributed and Parallel Computing Systems
- Gamma-ray bursts and supernovae
- Genetic Associations and Epidemiology
- Particle Accelerators and Free-Electron Lasers
- Nuclear reactor physics and engineering
- Radiation Detection and Scintillator Technologies
- Birth, Development, and Health
- Radiation Therapy and Dosimetry
- Statistical Methods and Bayesian Inference
- Epigenetics and DNA Methylation
- Cold Atom Physics and Bose-Einstein Condensates
- Nuclear physics research studies
- International Science and Diplomacy
- Gas Dynamics and Kinetic Theory
Institute of Science and Technology Austria
2023-2024
Institute of High Energy Physics
2014-2023
Austrian Academy of Sciences
2012-2017
National and Kapodistrian University of Athens
2016
European Organization for Nuclear Research
2012-2014
Results are presented from searches for the standard model Higgs boson in proton-proton collisions at sqrt(s) = 7 and 8 TeV Compact Muon Solenoid experiment LHC, using data samples corresponding to integrated luminosities of up 5.1 inverse femtobarns 5.3 TeV. The search is performed five decay modes: gamma gamma, ZZ, WW, tau tau, b b-bar. An excess events observed above expected background, with a local significance 5.0 deviations, mass near 125 GeV, signalling production new particle. that...
The CMS apparatus was identified, a few years before the start of LHC operation at CERN, to feature properties well suited particle-flow (PF) reconstruction: highly-segmented tracker, fine-grained electromagnetic calorimeter, hermetic hadron strong magnetic field, and an excellent muon spectrometer. A fully-fledged PF reconstruction algorithm tuned detector therefore developed has been consistently used in physics analyses for first time collider. For each collision, comprehensive list...
This paper describes the CMS trigger system and its performance during Run 1 of LHC. The consists two levels designed to select events potential physics interest from a GHz (MHz) interaction rate proton-proton (heavy ion) collisions. first level is implemented in hardware, selects containing detector signals consistent with an electron, photon, muon, τ lepton, jet, or missing transverse energy. A programmable menu up 128 object-based algorithms used for subsequent processing. thresholds are...
Properties of the Higgs boson with mass near 125 $$\,\text {GeV}$$ are measured in proton-proton collisions CMS experiment at LHC. Comprehensive sets production and decay measurements combined. The channels include $$\gamma \gamma $$ , $$\mathrm{Z}\mathrm{Z}$$ $$\mathrm{W}\mathrm{W}$$ $$\tau \tau $$\mathrm{b} \mathrm{b} $$\mu \mu pairs. data samples were collected 2011 2012 correspond to integrated luminosities up 5.1 {fb}^\text {-1}$$ 7 {TeV}$$ 19.7 8 . From high-resolution channels, is...
Results on two-particle angular correlations for charged particles emitted in pPb collisions at a nucleon–nucleon center-of-mass energy of 5.02 TeV are presented. The analysis uses two million collected with the CMS detector LHC. studied over broad range pseudorapidity, η, and full azimuth, ϕ, as function particle multiplicity transverse momentum, pT. In high-multiplicity events, long-range (2<|Δη|<4), near-side (Δϕ≈0) structure emerges Δη–Δϕ correlation functions. This is first observation...
A detailed description is reported of the analysis used by CMS Collaboration in search for standard model Higgs boson pp collisions at LHC, which led to observation a new boson. The data sample corresponds integrated luminosities up 5.1 inverse femtobarns sqrt(s) = 7 TeV, and 5.3 8 TeV. results five decay modes gamma gamma, ZZ, WW, tau tau, bb, show combined local significance 5 deviations near 125 GeV, are reviewed. fit invariant mass two high resolution channels, ZZ 4 ell, gives estimate...
New sets of parameters (“tunes”) for the underlying-event (UE) modelling pythia8, pythia6 and herwig++ Monte Carlo event generators are constructed using different parton distribution functions. Combined fits to CMS UE proton–proton ( $$\mathrm {p}\mathrm {p}$$ ) data at $$\sqrt{s} = 7\,\text {TeV} $$ proton–antiproton {p}\overline{\mathrm{p}} from CDF experiment lower $$\sqrt{s}$$ , used study models constrain their parameters, providing thereby improved predictions collisions 13 $$\,\text...
Many measurements and searches for physics beyond the standard model at LHC rely on efficient identification of heavy-flavour jets, i.e. jets originating from bottom or charm quarks. In this paper, discriminating variables algorithms used jet during first years operation CMS experiment in proton-proton collisions a centre-of-mass energy 13 TeV, are presented. Heavy-flavour have been improved compared to those previously energies 7 8 TeV. For with transverse momenta range expected simulated...
Improved jet energy scale corrections, based on a data sample corresponding to an integrated luminosity of 19.7 inverse-femtobarns collected by the CMS experiment in proton-proton collisions at center-of-mass 8 TeV, are presented. The corrections as function pseudorapidity eta and transverse momentum pT extracted from simulated events combining several channels methods. They account successively for effects pileup, uniformity detector response, residual data-simulation differences. Further...
The properties of a Higgs boson candidate are measured in the $H\ensuremath{\rightarrow}ZZ\ensuremath{\rightarrow}4\ensuremath{\ell}$ decay channel, with $\ensuremath{\ell}=e$, $\ensuremath{\mu}$, using data from $pp$ collisions corresponding to an integrated luminosity $5.1\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ at center-of-mass energy $\sqrt{s}=7\text{ }\mathrm{TeV}$ and $19.7\text{ }{\mathrm{fb}}^{\ensuremath{-}\text{1}}$ $\sqrt{s}=8\text{ }\mathrm{TeV}$, recorded CMS detector...
A joint measurement is presented of the branching fractions $B^0_s\to\mu^+\mu^-$ and $B^0\to\mu^+\mu^-$ in proton-proton collisions at LHC by CMS LHCb experiments. The data samples were collected 2011 a centre-of-mass energy 7 TeV, 2012 8 TeV. combined analysis produces first observation decay, with statistical significance exceeding six standard deviations, best its fraction so far. Furthermore, evidence for decay obtained three deviations. measurements are statistically compatible SM...
Measurements of two- and four-particle angular correlations for charged particles emitted in pPb collisions are presented over a wide range pseudorapidity full azimuth. The data, corresponding to an integrated luminosity approximately 31 inverse nanobarns, were collected during the 2013 LHC run at nucleon-nucleon center-of-mass energy 5.02 TeV by CMS experiment. results compared 2.76 semi-peripheral PbPb collision 2011 run, covering similar particle multiplicities. observed characterized...
Combined measurements of the production and decay rates Higgs boson, as well its couplings to vector bosons fermions, are presented. The analysis uses LHC proton-proton collision data set recorded with CMS detector in 2016 at $\sqrt{s} =$ 13 TeV, corresponding an integrated luminosity 35.9 fb$^{-1}$. combination is based on analyses targeting five main boson mechanisms (gluon fusion, associated a W or Z top quark-antiquark pair) following modes: H $\to$ $\gamma\gamma$, ZZ, WW, $\tau\tau$,...
Observation of the diphoton decay mode recently discovered Higgs boson and measurement some its properties are reported. The analysis uses entire dataset collected by CMS experiment in proton-proton collisions during 2011 2012 LHC running periods. data samples correspond to integrated luminosities 5.1[Formula: see text]at [Formula: text] 19.7[Formula: 8[Formula: . A clear signal is observed channel at a mass close 125[Formula: with local significance text], where expected for standard model...
The CMS muon detector system, reconstruction software, and high-level trigger underwent significant changes in 2013-2014 preparation for running at higher LHC collision energy instantaneous luminosity. performance of the modified system is studied using proton-proton data center-of-mass $\sqrt{s}=$ 13 TeV, collected 2015 2016. measured parameters, including spatial resolution, efficiency, timing, are found to meet all design specifications well reproduced by simulation. Despite more...
Results are presented from a search for particle dark matter (DM), extra dimensions, and unparticles using events containing jet an imbalance in transverse momentum. The data were collected by the CMS detector proton-proton collisions at LHC correspond to integrated luminosity of 19.7 inverse femtobarns centre-of-mass energy 8 TeV. number observed is found be consistent with standard model prediction. Limits placed on DM-nucleon scattering cross section as function DM mass spin-dependent...
Measurements of two- and multi-particle angular correlations in pp collisions at sqrt(s) = 5, 7, 13 TeV are presented as a function charged-particle multiplicity. The data, corresponding to integrated luminosities 1.0 inverse picobarn (5 TeV), 6.2 picobarns (7 0.7 (13 were collected using the CMS detector LHC. second-order (v[2]) third-order (v[3]) azimuthal anisotropy harmonics unidentified charged particles, well v[2] K0 short Lambda/anti-Lambda extracted from long-range two-particle...
A study is presented of the mass and spin-parity new boson recently observed at LHC a near 125 GeV. An integrated luminosity 17.3 fb(-1), collected by CMS experiment in proton-proton collisions center-of-mass energies 7 8 TeV, used. The measured ZZ channel, where both Z bosons decay to e or μ pairs, 126.2 ± 0.6(stat) 0.2(syst) angular distributions lepton pairs this channel are sensitive boson. Under assumption spin 0, present data consistent with pure scalar hypothesis, while disfavoring...
New sets of CMS underlying-event parameters ("tunes") are presented for the PYTHIA8 event generator. These tunes use NNPDF3.1 parton distribution functions (PDFs) at leading (LO), next-to-leading (NLO), or next-to-next-to-leading (NNLO) orders in perturbative quantum chromodynamics, and strong coupling evolution LO NLO. Measurements charged-particle multiplicity transverse momentum densities various hadron collision energies fit simultaneously to determine tunes. Comparisons predictions new...
The study of the spin-parity and tensor structure interactions recently discovered Higgs boson is performed using H to ZZ, Z gamma*, gamma* 4 l, WW l nu nu, gamma decay modes. full dataset recorded by CMS experiment during LHC Run 1 used, corresponding an integrated luminosity up 5.1 inverse femtobarns at a center-of-mass energy 7 TeV 19.7 8 TeV. A wide range spin-two models excluded 99% confidence level or higher, 99.87% for minimal gravity-like couplings, regardless whether assumptions are...
Results are presented from a search for the rare decays ${B}_{s}^{0}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ and ${B}^{0}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ in $pp$ collisions at $\sqrt{s}=7$ 8 TeV, with data samples corresponding to integrated luminosities of 5 $20\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$, respectively, collected by CMS experiment LHC. An unbinned maximum-likelihood fit dimuon...
The observation of the standard model (SM) Higgs boson decay to a pair bottom quarks is presented. main contribution this result from processes in which bosons are produced association with W or Z (VH), and searched for final states including 0, 1, 2 charged leptons two identified quark jets. results measurement these data sample recorded by CMS experiment 2017, comprising 41.3 fb$^{-1}$ proton-proton collisions at $\sqrt{s} =$ 13 TeV, described. When combined previous VH measurements using...
A bstract search for the standard model Higgs boson decaying to a W-boson pair at LHC is reported. The event sample corresponds an integrated luminosity of 4.9 fb −1 and 19.4 collected with CMS detector in pp collisions $ \sqrt{s} = 7 8 TeV, respectively. candidates are selected events two or three charged leptons. An excess above background observed, consistent expectation from mass around 125 GeV. probability observe equal larger than one seen, under background-only hypothesis,...
A search for new physics is performed in multijet events with large missing transverse momentum produced proton-proton collisions at sqrt(s) = 8 TeV using a data sample corresponding to an integrated luminosity of 19.5 inverse femtobarns collected the CMS detector LHC. The divided into three jet multiplicity categories (3-5, 6-7, and or more jets), studied further bins two variables: scalar sum momenta momentum. observed numbers various are consistent backgrounds expected from standard model...
A search for invisible decays of a Higgs boson is performed using proton-proton collision data collected with the CMS detector at LHC in 2016 center-of-mass energy , corresponding to an integrated luminosity 35.9. The targets production via vector fusion. are found be agreement background contributions from standard model processes. An observed (expected) upper limit 0.33 (0.25), 95% confidence level, placed on branching fraction decay particles, assuming rates and mass 125.09 GeV. Results...