2,014 research outputs found
Recommended from our members
Search for CP violating top quark couplings in pp collisions at âs = 13 TeV
A preprint version of the article is available at arXiv:2205.07434v2 [hep-ex], https://arxiv.org/abs/2205.07434. It has not been certified by peer review.Results are presented from a search for CP violation in top quark pair production, using proton-proton collisions at a center-of-mass energy of 13 TeV. The data used for this analysis consist of final states with two charged leptons collected by the CMS experiment, and correspond to an integrated luminosity of 35.9 fbâ1. The search uses two observables, O1 and O3, which are Lorentz scalars. The observable O1 is constructed from the four-momenta of the charged leptons and the reconstructed top quarks, while O3 consists of the four-momenta of the charged leptons and the b quarks originating from the top quarks. Asymmetries in these observables are sensitive to CP violation, and their measurement is used to determine the chromoelectric dipole moment of the top quark. The results are consistent with the expectation from the standard model. [Figure not available: see fulltext.].SCOAP
Recommended from our members
Measurement of the Higgs boson width and evidence of its off-shell contributions to ZZ production
Since the discovery of the Higgs boson in 2012, detailed studies of its properties have been ongoing. Besides its mass, its widthârelated to its lifetimeâis an important parameter. One way to determine this quantity is to measure 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-section of two Z bosons with data from the CMS experiment at the CERN Large Hadron Collider. We constrain the total rate of the off-shell Higgs boson contribution beyond the Z boson pair production threshold, relative to its standard model expectation, to the interval [0.0061, 2.0] at the 95% confidence level. The scenario with no off-shell contribution is excluded at a p-value of 0.0003 (3.6 standard deviations). We measure the width of the Higgs boson as ÎH=3.2â1.7+2.4MeV, in agreement with the standard model expectation of 4.1 MeV. In addition, we set constraints on anomalous Higgs boson couplings to W and Z boson pairs
Recommended from our members
Evaluation of planar silicon pixel sensors with the RD53A readout chip for the Phase-2 Upgrade of the CMS Inner Tracker
Shared via Kudos: https://www.growkudos.com/publications/10.1088%25252F1748-0221%25252F18%25252F11%25252Fp11015The Large Hadron Collider at CERN will undergo an upgrade in order to increase its luminosity to 7.5 Ă 10^34 cm^-2s^-1. The increased luminosity during this High-Luminosity running phase, starting around 2029, means a higher rate of proton-proton interactions, hence a larger ionizing dose and particle fluence for the detectors. The current tracking system of the CMS experiment will be fully replaced in order to cope with the new operating conditions. Prototype planar pixel sensors for the CMS Inner Tracker with square 50 ÎŒm Ă 50 ÎŒm and rectangular 100 ÎŒm Ă 25 ÎŒm pixels read out by the RD53A chip were characterized in the lab and at the DESY-II testbeam facility in order to identify designs that meet the requirements of CMS during the High-Luminosity running phase. A spatial resolution of approximately 3.4 ÎŒm (2 ÎŒm) is obtained using the modules with 50 ÎŒm Ă 50 ÎŒm (100 ÎŒm Ă 25 ÎŒm) pixels at the optimal angle of incidence before irradiation. After irradiation to a 1 MeV neutron equivalent fluence of Ίeq = 5.3 Ă 10^15 cm^-2, a resolution of 9.4 ÎŒm is achieved at a bias voltage of 800 V using a module with 50 ÎŒm Ă 50 ÎŒm pixel size. All modules retain a hit efficiency in excess of 99% after irradiation to fluences up to 2.1 Ă 10^16 cm^-2. Further studies of the electrical properties of the modules, especially crosstalk, are also presented in this paper.BMWFWandFWF(Austria);FNRSandFWO(Belgium);CERN;MSEandCSF(Croatia);Academy
of Finland, MEC, and HIP (Finland); CEA and CNRS/IN2P3 (France); BMBF, DFG, and HGF
(Germany); GSRT (Greece); NKFIA K124850, and Bolyai Fellowship of the Hungarian Academy of
Sciences (Hungary); DAE and DST (India); INFN (Italy); PAEC (Pakistan); SEIDI, CPAN, PCTI and
FEDER(Spain); Swiss Funding Agencies (Switzerland); MST (Taipei); STFC (United Kingdom);
DOEandNSF(U.S.A.). This project has received funding from the European Unionâs Horizon 2020
research and innovation program under the Marie SkĆodowska-Curie grant agreement No 884104
(PSI-FELLOW-III-3i) and project AIDA-2020, GA no. 654168. Individuals have received support
from HFRI (Greece)
Recommended from our members
Search for nonresonant Higgs boson pair production in the four leptons plus two b jets final state in proton-proton collisions at = 13 TeV
A preprint version of the article is available at arXiv:2206.10657v2 [hep-ex], https://arxiv.org/abs/2206.10657 . Comments: Replaced with the published version. Added the journal reference and the DOI. All the figures and tables can be found at this http URL (CMS Public Pages). Report number: CMS-HIG-20-004, CERN-EP-2022-114.The first search for nonresonant production of Higgs boson pairs (HH) with one H decaying into four leptons and the other into a pair of b quarks is presented, using proton-proton collisions recorded at a center-of-mass energy of s = 13 TeV by the CMS experiment. The analyzed data correspond to an integrated luminosity of 138 fbâ1. A 95% confidence level upper limit of 32.4 is set on the signal strength modifier ÎŒ, defined as the ratio of the observed HH production rate in the HHâ ZZâb b ÂŻ â 4 âb b ÂŻ decay channel to the standard model (SM) expectation. Possible modifications of the H trilinear coupling λ HHH with respect to the SM value are investigated. The coupling modifier Îșλ, defined as λ HHH divided by its SM prediction, is constrained to be within the observed (expected) range â8.8 (â9.8) < Îșλ < 13.4 (15.0) at 95% confidence level. [Figure not available: see fulltext.].SCOAP3
Recommended from our members
Search for long-lived particles decaying to a pair of muons in proton-proton collisions at âs = 13 TeV
A preprint version of the article is available at arXiv:2205.08582v2 [hep-ex], https://arxiv.org/abs/2205.08582 . Comments: Replaced with the published version. Added the journal reference and the DOI. All the figures and tables, including additional supplementary figures and tables, can be found at https://cms-results.web.cern.ch/cms-results/public-results/publications/EXO-21-006 (CMS Public Pages).An inclusive search for long-lived exotic particles decaying to a pair of muons is presented. The search uses data collected by the CMS experiment at the CERN LHC in proton-proton collisions at s = 13 TeV in 2016 and 2018 and corresponding to an integrated luminosity of 97.6 fbâ1. The experimental signature is a pair of oppositely charged muons originating from a common secondary vertex spatially separated from the pp interaction point by distances ranging from several hundred ÎŒm to several meters. The results are interpreted in the frameworks of the hidden Abelian Higgs model, in which the Higgs boson decays to a pair of long-lived dark photons ZD, and of a simplified model, in which long-lived particles are produced in decays of an exotic heavy neutral scalar boson. For the hidden Abelian Higgs model with m(ZD) greater than 20 GeV and less than half the mass of the Higgs boson, they provide the best limits to date on the branching fraction of the Higgs boson to dark photons for cÏ(ZD) (varying with m(ZD)) between 0.03 and â0.5 mm, and above â0.5 m. Our results also yield the best constraints on long-lived particles with masses larger than 10 GeV produced in decays of an exotic scalar boson heavier than the Higgs boson and decaying to a pair of muons. [Figure not available: see fulltext.].SCOAP3
Recommended from our members
Search for top squarks in the four-body decay mode with single lepton final states in proton-proton collisions at âs = 13 TeV
A preprint version of the article is available at arXiv:2301.08096v2 [hep-ex], https://arxiv.org/abs/2301.08096 . Comments: Replaced with the published version. Added the journal reference and the DOI. All the figures and tables can be found at https://cms-results.web.cern.ch/cms-results/public-results/publications/SUS-21-003 (CMS Public Pages).A search for the pair production of the lightest supersymmetric partner of the top quark, the top squark (t ~1), is presented. The search targets the four-body decay of the t ~1 , which is preferred when the mass difference between the top squark and the lightest supersymmetric particle is smaller than the mass of the W boson. This decay mode consists of a bottom quark, two other fermions, and the lightest neutralino (Ï~10), which is assumed to be the lightest supersymmetric particle. The data correspond to an integrated luminosity of 138 fbâ1 of proton-proton collisions at a center-of-mass energy of 13 TeV collected by the CMS experiment at the CERN LHC. Events are selected using the presence of a high-momentum jet, an electron or muon with low transverse momentum, and a significant missing transverse momentum. The signal is selected based on a multivariate approach that is optimized for the difference between m(t ~1) and m(Ï~10). The contribution from leading background processes is estimated from data. No significant excess is observed above the expectation from standard model processes. The results of this search exclude top squarks at 95% confidence level for masses up to 480 and 700 GeV for m(t ~1) â m(Ï~10) = 10 and 80 GeV, respectively. [Figure not available: see fulltext.].SCOAP3
Recommended from our members
Luminosity determination using Z boson production at the CMS experiment
Data Availability Statement - This manuscript has no associated data or
the data will not be deposited. [Authorsâ comment: Release and preser
vation of data used by the CMS Collaboration as the basis for publi
cations is guidedbytheCMSpolicyasstatedinhttps://cms-docdb.cern.
ch/cgibin/PublicDocDB/RetrieveFile?docid=6032&filename=CMSD
ataPolicyV1.2.pdf&version=2. CMS data preservation,re-use and open
access policy.]The measurement of ZÂ boson production is presented as a method to determine the integrated luminosity of CMS data sets. The analysis uses protonâproton collision data, recorded by the CMS experiment at the CERN LHC in 2017 at a center-of-mass energy of 13 TeV . Events with ZÂ bosons decaying into a pair of muons are selected. The total number of ZÂ bosons produced in a fiducial volume is determined, together with the identification efficiencies and correlations from the same data set, in small intervals of 20 pb-1 of integrated luminosity, thus facilitating the efficiency and rate measurement as a function of time and instantaneous luminosity. Using the ratio of the efficiency-corrected numbers of ZÂ bosons, the precisely measured integrated luminosity of one data set is used to determine the luminosity of another. For the first time, a full quantitative uncertainty analysis of the use of Z bosons for the integrated luminosity measurement is performed. The uncertainty in the extrapolation between two data sets, recorded in 2017 at low and high instantaneous luminosity, is less than 0.5%. We show that the ZÂ boson rate measurement constitutes a precise method, complementary to traditional methods, with the potential to improve the measurement of the integrated luminosity.SCOAP
Recommended from our members
Search for new Higgs bosons via same-sign top quark pair production in association with a jet in proton-proton collisions at s = 13 TeV
A search is presented for new Higgs bosons in proton-proton (pp) collision events in which a same-sign top quark pair is produced in association with a jet, via the ppâtH/Aâttc⟠and ppâtH/Aâttu⟠processes. Here, H and A represent the extra scalar and pseudoscalar boson, respectively, of the second Higgs doublet in the generalized two-Higgs-doublet model (g2HDM). The search is based on pp collision data collected at a center-of-mass energy of 13 TeV with the CMS detector at the LHC, corresponding to an integrated luminosity of 138 fbâ1. Final states with a same-sign lepton pair in association with jets and missing transverse momentum are considered. New Higgs bosons in the 200â1000 GeV mass range and new Yukawa couplings between 0.1 and 1.0 are targeted in the search, for scenarios in which either H or A appear alone, or in which they coexist and interfere. No significant excess above the standard model prediction is observed. Exclusion limits are derived in the context of the g2HDM
Recommended from our members
Search for ZZ and ZH production in the bbÌ bbÌ final state using proton-proton collisions at âs = 13TeV
A preprint version of the article is available at arXiv - https://arxiv.org/abs/2403.20241A search for ZZ and ZH production in the bbÌ
bbÌ
final state is presented, where H is the standard model (SM) Higgs boson. The search uses an event sample of proton-proton collisions corresponding to an integrated luminosity of 133fbâ1 collected at a center-of-mass energy of 13TeV with the CMS detector at the CERN LHC. The analysis introduces several novel techniques for deriving and validating a multi-dimensional background model based on control samples in data. A multiclass multivariate classifier customized for the bbÌ
bbÌ
final state is developed to derive the background model and extract the signal. The data are found to be consistent, within uncertainties, with the SM predictions. The observed (expected) upper limits at 95% confidence level are found to be 3.8 (3.8) and 5.0 (2.9) times the SM prediction for the ZZ and ZH production cross sections, respectively.SCOAP
- âŠ