Search results for "LHC"
showing 10 items of 342 documents
Evidence for the production of three massive vector bosons with the ATLAS detector
2019
A search for the production of three massive vector bosons in proton–proton collisions is performed using data at TeV recorded with the ATLAS detector at the Large Hadron Collider in the years 2015–2017, corresponding to an integrated luminosity of 79.8 fb−1. Events with two same-sign leptons ℓ (electrons or muons) and at least two reconstructed jets are selected to search for . Events with three leptons without any same-flavour opposite-sign lepton pairs are used to search for , while events with three leptons and at least one same-flavour opposite-sign lepton pair and one or more reconstructed jets are used to search for . Finally, events with four leptons are analysed to search for and .…
Study of J/ψ Production in Jets
2017
The production of $J/\psi$ mesons in jets is studied in the forward region of proton-proton collisions using data collected with the LHCb detector at a center-of-mass energy of 13 TeV. The fraction of the jet transverse momentum carried by the $J/\psi$ meson, $z \equiv p_{\rm T}(J/\psi)/p_{\rm T}({\rm jet})$, is measured using jets with $p_{\rm T}({\rm jet}) > 20$ GeV in the pseudorapidity range $2.5 < \eta({\rm jet}) < 4.0$. The observed $z$ distribution for $J/\psi$ mesons produced in $b$-hadron decays is consistent with expectations. However, the results for prompt $J/\psi$ production do not agree with predictions based on fixed-order non-relativistic QCD. This is the first measurement o…
Measurement of the W boson mass
1996
The W boson mass is measured using proton-proton collision data at root s = 13 TeV corresponding to an integrated luminosity of 1.7fb(-1) recorded during 2016 by the LHCb experiment. With a simultaneous fit of the muon q/p(T) distribution of a sample of W ->mu y decays and the phi* distribution of a sample of Z -> mu mu decays the W boson mass is determined to be
Constraints on off-shell Higgs boson production and the Higgs boson total width in ZZ → 4ℓ and ZZ → 2ℓ2ν final states with the ATLAS detector
2018
A measurement of off-shell Higgs boson production in the and decay channels, where ℓ stands for either an electron or a muon, is performed using data from proton–proton collisions at a centre-of-mass energy of TeV. The data were collected by the ATLAS experiment in 2015 and 2016 at the Large Hadron Collider, and they correspond to an integrated luminosity of . An observed (expected) upper limit on the off-shell Higgs signal strength, defined as the event yield normalised to the Standard Model prediction, of 3.8 (3.4) is obtained at 95% confidence level (CL). Assuming the ratio of the Higgs boson couplings to the Standard Model predictions is independent of the momentum transfer of the Higgs…
"Table 3" of "Search for Higgs boson decays into a $Z$ boson and a light hadronically decaying resonance using 13 TeV $pp$ collision data from the AT…
2020
Expected and observed 95% CL upper limits on $\sigma(pp\to H)B(H\to Za)/$pb. These results are quoted for $B(a\to gg)=100\%$ and $B(a\to s\bar{s})=100\%$ for each signal sample. The smaller (larger) quoted ranges around the expected limits represent $\pm 1\sigma$ ($\pm 2\sigma$) fluctuations.
"Table 4" of "Search for Higgs boson decays into a $Z$ boson and a light hadronically decaying resonance using 13 TeV $pp$ collision data from the AT…
2020
Expected and observed 95% CL upper limits on $\sigma(pp\to H)B(H\to Z(\eta_c~\text{or}~J/\psi))/$pb. The smaller (larger) quoted ranges around the expected limits represent $\pm 1\sigma$ ($\pm 2\sigma$) fluctuations.
Observation of $Z$ production in proton-lead collisions at LHCb
2014
The first observation of $Z$ boson production in proton-lead collisions at a centre-of-mass energy per proton-nucleon pair of $\sqrt{s_{NN}}=5~\text{TeV}$ is presented. The data sample corresponds to an integrated luminosity of $1.6~\text{nb}^{-1}$ collected with the LHCb detector. The $Z$ candidates are reconstructed from pairs of oppositely charged muons with pseudorapidities between 2.0 and 4.5 and transverse momenta above $20~\text{GeV}/c$. The invariant dimuon mass is restricted to the range $60-120~\text{GeV}/c^2$. The $Z$ production cross-section is measured to be \begin{eqnarray*} ��_{Z\to��^+��^-}(\text{fwd})&=&13.5^{+5.4}_{-4.0}\text{(stat.)}\pm1.2\text{(syst.)}~\text{nb} …
Search for the neutral Higgs bosons of the Minimal Supersymmetric Standard Model in $pp$ collisions at $\sqrt{s}=7$ TeV with the ATLAS detector
2013
A search for neutral Higgs bosons of the Minimal Supersymmetric Standard Model (MSSM) is reported. The analysis is based on a sample of proton-proton collisions at a centre-of-mass energy of 7 TeV recorded with the ATLAS detector at the Large Hadron Collider. The data were recorded in 2011 and correspond to an integrated luminosity of 4.7 fb[superscript −1] to 4.8 fb[superscript −1]. Higgs boson decays into oppositely-charged muon or τ lepton pairs are considered for final states requiring either the presence or absence of b-jets. No statistically significant excess over the expected background is observed and exclusion limits at the 95% confidence level are derived. The exclusion limits ar…
Measurement of Higgs boson properties in the diphoton decay channel and a search for di-Higgs production in the gamma gamma b anti-b final state with…
2018
La búsqueda del bosón de Higgs fue la pieza central de los programas de física para los experimentos en el Gran Colisionador de Hadrones durante el Run 1 de la toma de datos. El descubrimiento de esta partícula, anunciado el 4 de julio de 2012 por las colaboraciones de ATLAS y CMS, representó un hito a la hora de comprender el mecanismo de ruptura de simetría electrodébil, por el cual las partículas fundamentales adquieren masa. Ahora es esencial que el bosón de Higgs sea ampliamente estudiado. Las mediciones precisas de sus propiedades confirmarán su naturaleza y cualquier desviación de la predicción del Modelo Estándar representará un signo claro de nueva física. Esta tesis presenta dos a…
Precise Phenomenology in the LHC era
2021
Desde la detección del bosón de Higgs en 2012, la comunidad experimental ha centrado sus esfuerzos en la medida de precisión del Modelo Estándar (SM, por sus siglas en inglés). Para satisfacer las demandas de la precisión experimental al LHC en el futuro cercano, cálculos a segundo orden en teoría de perturbaciones son necesarios. El LHC es un colisionador hadrónico, lo que significa que una alta multiplicidad en el estado final es de esperarse debido a la radiación QCD. Para comparar nuestras predicciones teóricas con el experimento, esta radiación QCD debe ser modelada y calculada, lo que se hace utilizando cascádas partónicas mediante generadores de evento de Monte Carlo (MC). Los MCs, n…