Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 88
Filtrar
Mais filtros

Base de dados
País/Região como assunto
Tipo de documento
Intervalo de ano de publicação
1.
Phys Rev Lett ; 131(5): 051901, 2023 Aug 04.
Artigo em Inglês | MEDLINE | ID: mdl-37595238

RESUMO

The structure of nucleons is multidimensional and depends on the transverse momenta, spatial geometry, and polarization of the constituent partons. Such a structure can be studied using high-energy photons produced in ultraperipheral heavy-ion collisions. The first measurement of the azimuthal angular correlations of exclusively produced events with two jets in photon-lead interactions at large momentum transfer is presented, a process that is considered to be sensitive to the underlying nuclear gluon polarization. This study uses a data sample of ultraperipheral lead-lead collisions at sqrt[s_{NN}]=5.02 TeV, corresponding to an integrated luminosity of 0.38 nb^{-1}, collected with the CMS experiment at the LHC. The measured second harmonic of the correlation between the sum and difference of the two jet transverse momentum vectors is found to be positive, and rising, as the dijet transverse momentum increases. A well-tuned model that has been successful at describing a wide range of proton scattering data from the HERA experiments fails to describe the observed correlations, suggesting the presence of gluon polarization effects.

2.
Phys Rev Lett ; 128(8): 081805, 2022 Feb 25.
Artigo em Inglês | MEDLINE | ID: mdl-35275660

RESUMO

Measurements of the inclusive and differential fiducial cross sections of the Higgs boson are presented, using the τ lepton decay channel. The differential cross sections are measured as functions of the Higgs boson transverse momentum, jet multiplicity, and transverse momentum of the leading jet in the event, if any. The analysis is performed using proton-proton collision data collected with the CMS detector at the LHC at a center-of-mass energy of 13 TeV and corresponding to an integrated luminosity of 138 fb^{-1}. These are the first differential measurements of the Higgs boson cross section in the final state of two τ leptons. In final states with a large jet multiplicity or with a Lorentz-boosted Higgs boson, these measurements constitute a significant improvement over measurements performed in other final states.

3.
Phys Rev Lett ; 128(25): 252301, 2022 Jun 24.
Artigo em Inglês | MEDLINE | ID: mdl-35802434

RESUMO

The B_{c}^{+} meson is observed for the first time in heavy ion collisions. Data from the CMS detector are used to study the production of the B_{c}^{+} meson in lead-lead (Pb-Pb) and proton-proton (pp) collisions at a center-of-mass energy per nucleon pair of sqrt[s_{NN}]=5.02 TeV, via the B_{c}^{+}→(J/ψ→µ^{+}µ^{-})µ^{+}ν_{µ} decay. The B_{c}^{+} nuclear modification factor, derived from the Pb-Pb-to-pp ratio of production cross sections, is measured in two bins of the trimuon transverse momentum and of the Pb-Pb collision centrality. The B_{c}^{+} meson is shown to be less suppressed than quarkonia and most of the open heavy-flavor mesons, suggesting that effects of the hot and dense nuclear matter created in heavy ion collisions contribute to its production. This measurement sets forth a promising new probe of the interplay of suppression and enhancement mechanisms in the production of heavy-flavor mesons in the quark-gluon plasma.

4.
Phys Rev Lett ; 129(3): 032001, 2022 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-35905365

RESUMO

Proton-proton interactions resulting in final states with two photons are studied in a search for the signature of flavor-changing neutral current interactions of top quarks (t) and Higgs bosons (H). The analysis is based on data collected at a center-of-mass energy of 13 TeV with the CMS detector at the LHC, corresponding to an integrated luminosity of 137 fb^{-1}. No significant excess above the background prediction is observed. Upper limits on the branching fractions (B) of the top quark decaying to a Higgs boson and an up (u) or charm (c) quark are derived through a binned fit to the diphoton invariant mass spectrum. The observed (expected) 95% confidence level upper limits are found to be 0.019% (0.031%) for B(t→Hu) and 0.073% (0.051%) for B(t→Hc). These are the strictest upper limits yet determined.

5.
Phys Rev Lett ; 129(2): 021802, 2022 Jul 08.
Artigo em Inglês | MEDLINE | ID: mdl-35867460

RESUMO

A search for resonances decaying into a W boson and a radion, where the radion decays into two W bosons, is presented. The data analyzed correspond to an integrated luminosity of 138 fb^{-1} recorded in proton-proton collisions with the CMS detector at sqrt[s]=13 TeV. One isolated charged lepton is required, together with missing transverse momentum and one or two massive large-radius jets, containing the decay products of either two or one W bosons, respectively. No excess over the background estimation is observed. The results are combined with those from a complementary channel with an all-hadronic final state, described in an accompanying paper. Limits are set on parameters of an extended warped extra-dimensional model. These searches are the first of their kind at the LHC.

6.
Phys Rev Lett ; 129(2): 022001, 2022 Jul 08.
Artigo em Inglês | MEDLINE | ID: mdl-35867464

RESUMO

Multiparticle azimuthal correlations of prompt D^{0} mesons are measured in Pb-Pb collisions at a nucleon-nucleon center-of-mass energy of sqrt[s_{NN}]=5.02 TeV. For the first time, a four-particle cumulant method is used to extract the second Fourier coefficient of the azimuthal distribution (v_{2}) of D^{0} mesons as a function of event centrality and the D^{0} transverse momentum. The ratios of the four-particle v_{2} values to previously measured two-particle cumulant results provide direct experimental access to event-by-event fluctuations of charm quark azimuthal anisotropies. These ratios are also found to be comparable to those of inclusive charged particles in the event. However, hints of deviations are seen in the most central and peripheral collisions. To investigate the origin of flow fluctuations in the charm sector, these measurements are compared to a model implementing fluctuations of charm quark energy loss via collisional or radiative processes in the quark-gluon plasma. These models cannot quantitatively describe the data over the full transverse momentum and centrality ranges, although the calculations with collisional energy loss provide a better description of the data.

7.
Phys Rev Lett ; 126(25): 252003, 2021 Jun 25.
Artigo em Inglês | MEDLINE | ID: mdl-34241504

RESUMO

The Ξ_{b}^{-}π^{+}π^{-} invariant mass spectrum is investigated with an event sample of proton-proton collisions at sqrt[s]=13 TeV, collected by the CMS experiment at the LHC in 2016-2018 and corresponding to an integrated luminosity of 140 fb^{-1}. The ground state Ξ_{b}^{-} is reconstructed via its decays to J/ψΞ^{-} and J/ψΛK^{-}. A narrow resonance, labeled Ξ_{b}(6100)^{-}, is observed at a Ξ_{b}^{-}π^{+}π^{-} invariant mass of 6100.3±0.2(stat)±0.1(syst)±0.6(Ξ_{b}^{-}) MeV, where the last uncertainty reflects the precision of the Ξ_{b}^{-} baryon mass. The upper limit on the Ξ_{b}(6100)^{-} natural width is determined to be 1.9 MeV at 95% confidence level. The low Ξ_{b}(6100)^{-} signal yield observed in data does not allow a measurement of the quantum numbers of the new state. However, following analogies with the established excited Ξ_{c} baryon states, the new Ξ_{b}(6100)^{-} resonance and its decay sequence are consistent with the orbitally excited Ξ_{b}^{-} baryon, with spin and parity quantum numbers J^{P}=3/2^{-}.

8.
Phys Rev Lett ; 126(25): 252002, 2021 Jun 25.
Artigo em Inglês | MEDLINE | ID: mdl-34241533

RESUMO

A fiducial cross section for Wγ production in proton-proton collisions is measured at a center-of-mass energy of 13 TeV in 137 fb^{-1} of data collected using the CMS detector at the LHC. The W→eν and µν decay modes are used in a maximum-likelihood fit to the lepton-photon invariant mass distribution to extract the combined cross section. The measured cross section is compared with theoretical expectations at next-to-leading order in quantum chromodynamics. In addition, 95% confidence level intervals are reported for anomalous triple-gauge couplings within the framework of effective field theory.

9.
Phys Rev Lett ; 127(19): 191801, 2021 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-34797136

RESUMO

The first measurements of diboson production cross sections in proton-proton interactions at a center-of-mass energy of 5.02 TeV are reported. They are based on data collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 302 pb^{-1}. Events with two, three, or four charged light leptons (electrons or muons) in the final state are analyzed. The WW, WZ, and ZZ total cross sections are measured as σ_{WW}=37.0_{-5.2}^{+5.5}(stat)_{-2.6}^{+2.7}(syst) pb, σ_{WZ}=6.4_{-2.1}^{+2.5}(stat)_{-0.3}^{+0.5}(syst) pb, and σ_{ZZ}=5.3_{-2.1}^{+2.5}(stat)_{-0.4}^{+0.5}(syst) pb. All measurements are in good agreement with theoretical calculations at combined next-to-next-to-leading order quantum chromodynamics and next-to-leading order electroweak accuracy.

10.
Phys Rev Lett ; 127(26): 261804, 2021 Dec 24.
Artigo em Inglês | MEDLINE | ID: mdl-35029469

RESUMO

A search for long-lived particles (LLPs) produced in decays of standard model (SM) Higgs bosons is presented. The data sample consists of 137 fb^{-1} of proton-proton collisions at sqrt[s]=13 TeV, recorded at the LHC in 2016-2018. A novel technique is employed to reconstruct decays of LLPs in the end cap muon detectors. The search is sensitive to a broad range of LLP decay modes and to masses as low as a few GeV. No excess of events above the SM background is observed. The most stringent limits to date on the branching fraction of the Higgs boson to LLPs subsequently decaying to quarks and τ^{+}τ^{-} are found for proper decay lengths greater than 6, 20, and 40 m, for LLP masses of 7, 15, and 40 GeV, respectively.

11.
Tijdschr Psychiatr ; 61(3): 148-152, 2019.
Artigo em Holandês | MEDLINE | ID: mdl-30896023

RESUMO

BACKGROUND: The (medical) educational literature does not contain an unequivocal answer to the question 'what is a good quality post-graduate education in psychiatry?'.
AIM: To describe the meaning of 'quality' and the role of psychiatrists in training (residents or trainees) in achieving and monitoring high-quality post-graduate psychiatry education in the Netherlands.
METHOD: Critical consideration of the current system of post-graduate education in psychiatry.
RESULTS: A qualitatively good post-graduate training system offers residents an optimal learning climate in which the individual development plan is central and there is opportunity to acquire a good basis for all competency domains. Possibilities for improvement concern the quality of supervisors, flexibility in internships and curricular education, and extra attention for management and policy skills.
CONCLUSION: Suggestions are made for further development of post-graduate psychiatry training in the Netherlands.


Assuntos
Psiquiatria/educação , Currículo , Educação de Pós-Graduação em Medicina , Feminino , Humanos , Internato e Residência , Masculino , Países Baixos
12.
Ann Oncol ; 26(12): 2392-8, 2015 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-26371288

RESUMO

BACKGROUND: In clinical trials, the use of intermediate time-to-event end points (TEEs) is increasingly common, yet their choice and definitions are not standardized. This limits the usefulness for comparing treatment effects between studies. The aim of the DATECAN Kidney project is to clarify and recommend definitions of TEE in renal cell cancer (RCC) through a formal consensus method for end point definitions. MATERIALS AND METHODS: A formal modified Delphi method was used for establishing consensus. From a 2006-2009 literature review, the Steering Committee (SC) selected 9 TEE and 15 events in the nonmetastatic (NM) and metastatic/advanced (MA) RCC disease settings. Events were scored on the range of 1 (totally disagree to include) to 9 (totally agree to include) in the definition of each end point. Rating Committee (RC) experts were contacted for the scoring rounds. From these results, final recommendations were established for selecting pertinent end points and the associated events. RESULTS: Thirty-four experts scored 121 events for 9 end points. Consensus was reached for 31%, 43% and 85% events during the first, second and third rounds, respectively. The expert recommend the use of three and two endpoints in NM and MA setting, respectively. In the NM setting: disease-free survival (contralateral RCC, appearance of metastases, local or regional recurrence, death from RCC or protocol treatment), metastasis-free survival (appearance of metastases, regional recurrence, death from RCC); and local-regional-free survival (local or regional recurrence, death from RCC). In the MA setting: kidney cancer-specific survival (death from RCC or protocol treatment) and progression-free survival (death from RCC, local, regional, or metastatic progression). CONCLUSIONS: The consensus method revealed that intermediate end points have not been well defined, because all of the selected end points had at least one event definition for which no consensus was obtained. These clarified definitions of TEE should become standard practice in all RCC clinical trials, thus facilitating reporting and increasing precision in between trial comparisons.


Assuntos
Carcinoma de Células Renais/terapia , Determinação de Ponto Final/normas , Fidelidade a Diretrizes/normas , Neoplasias Renais/terapia , Ensaios Clínicos Controlados Aleatórios como Assunto/normas , Carcinoma de Células Renais/mortalidade , Técnica Delphi , Intervalo Livre de Doença , Determinação de Ponto Final/métodos , Humanos , Neoplasias Renais/mortalidade , Recidiva Local de Neoplasia/mortalidade , Recidiva Local de Neoplasia/terapia , Ensaios Clínicos Controlados Aleatórios como Assunto/métodos
13.
Ann Oncol ; 25(2): 429-34, 2014 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-24478320

RESUMO

BACKGROUND: The randomized, double-blind phase III AFFIRM trial demonstrated that enzalutamide, an oral androgen receptor inhibitor, significantly prolonged overall survival (OS) [median 18.4 versus 13.6 months (hazard ratio, HR) 0.63 (95% confidence interval, CI, 0.53-0.75); P<0.001] compared with placebo in patients with metastatic castration-resistant prostate cancer who received prior docetaxel chemotherapy. PATIENTS AND METHODS: A post hoc analysis was carried out to assess the efficacy and safety of enzalutamide on outcomes in younger (<75 years) and elderly (≥75 years) patients in the AFFIRM population. Statistics are presented by age group (<75 years, ≥75 years) for efficacy outcomes of OS, radiographic progression-free survival (rPFS), time to prostate-specific antigen (PSA) progression, PSA response, and safety. RESULTS: OS was significantly improved with enzalutamide over placebo in patients<75 years [median not yet reached versus 13.6 months; HR 0.63 (95% CI 0.52-0.78), P<0.001] and in patients ≥75 years [median 18.2 versus 13.3 months; HR 0.61 (95% CI 0.43-0.86), P=0.004], respectively. rPFS was similarly improved in both the younger [HR 0.45 (95% CI 0.38-0.53), P<0.001] and elderly patient cohorts [HR 0.27 (95% CI 0.20-0.37), P<0.001] relative to placebo, as were time to PSA progression and PSA response. Adverse events (AEs) were similar between the two enzalutamide age groups, with the exception of an increase in patients≥75 years in the rates of all grade peripheral edema (22.1% versus 12.5%), fatigue (39.7% versus 31.6%), and diarrhea (26.6% versus 19.6%). The overall grade≥3 AE rates were low with no major difference in frequency or severity between age groups or treatment arms. Five patients were reported with seizure events; three patients<75 years and two patients ≥75 years. CONCLUSIONS: Enzalutamide significantly improves outcomes in both younger (<75 years) and elderly patients (≥75 years), with comparable safety and tolerability.


Assuntos
Antagonistas de Receptores de Andrógenos/uso terapêutico , Antineoplásicos/uso terapêutico , Neoplasias Ósseas/tratamento farmacológico , Feniltioidantoína/análogos & derivados , Neoplasias de Próstata Resistentes à Castração/tratamento farmacológico , Idoso , Benzamidas , Neoplasias Ósseas/mortalidade , Neoplasias Ósseas/secundário , Intervalo Livre de Doença , Método Duplo-Cego , Humanos , Estimativa de Kaplan-Meier , Masculino , Nitrilas , Feniltioidantoína/uso terapêutico , Modelos de Riscos Proporcionais , Neoplasias de Próstata Resistentes à Castração/mortalidade , Neoplasias de Próstata Resistentes à Castração/patologia , Resultado do Tratamento
14.
Phys Rev Lett ; 112(9): 092002, 2014 Mar 07.
Artigo em Inglês | MEDLINE | ID: mdl-24655247

RESUMO

In the resummation of collinear gluons emitted together with active partons from the hadrons in the Drell-Yan process, effects of color entanglement become important when the transverse directions are taken into account. It is then no longer possible to write the cross section as the convolution of two soft correlators and a hard part. We show that the color entanglement introduces additional color factors that must be taken into account in the extraction of transverse momentum-dependent parton distribution functions from azimuthal asymmetries. Examples where such effects matter are the extractions of the double Sivers and double Boer-Mulders asymmetries. Furthermore, we will argue why this color entanglement is a basic ingredient already in the tree-level description of azimuthal asymmetries.

15.
Ann Oncol ; 24(9): 2396-402, 2013 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-23803225

RESUMO

BACKGROUND: Avastin and Roferon in Renal Cell Carcinoma (AVOREN) demonstrated efficacy for bevacizumab plus interferon-α2a (IFN; 9 MIU tiw) in first-line metastatic renal cell carcinoma (mRCC). We evaluated bevacizumab with low-dose IFN in mRCC to determine whether clinical benefit could be maintained with reduced toxicity. METHODS: BEVLiN was an open-label, single-arm, multinational, phase II trial. Nephrectomized patients with treatment-naive, clear cell mRCC and favourable/intermediate Memorial Sloan-Kettering Cancer Center scores received bevacizumab (10 mg/kg every 2 weeks) and IFN (3 MIU thrice weekly) until disease progression. Descriptive comparisons with AVOREN patients having favourable/intermediate MSKCC scores treated with bevacizumab plus IFN (9 MIU) were made. Primary end points were grade ≥3 IFN-associated adverse events (AEs) and progression-free survival (PFS). All grade ≥3 AEs and bevacizumab/IFN-related grade 1-2 AEs occurring from first administration until 28 days after last treatment were reported. RESULTS: A total of 146 patients were treated; the median follow-up was 29.4 months. Any-grade and grade ≥3 IFN-associated AEs occurred in 53.4% and 10.3% of patients, respectively. The median PFS and overall survival were 15.3 [95% confidence interval (CI): 11.7-18.0] and 30.7 months (95% CI: 25.7-not reached), respectively. The ORR was 28.8%. CONCLUSIONS: Compared with a historical control AVOREN subgroup, low-dose IFN with bevacizumab resulted in a reduction in incidence rates of IFN-related AEs, without compromising efficacy [NCT00796757].


Assuntos
Inibidores da Angiogênese/uso terapêutico , Anticorpos Monoclonais Humanizados/administração & dosagem , Anticorpos Monoclonais Humanizados/uso terapêutico , Carcinoma de Células Renais/tratamento farmacológico , Interferon-alfa/administração & dosagem , Interferon-alfa/uso terapêutico , Neoplasias Renais/tratamento farmacológico , Adulto , Inibidores da Angiogênese/efeitos adversos , Protocolos de Quimioterapia Combinada Antineoplásica/efeitos adversos , Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Bevacizumab , Carcinoma de Células Renais/mortalidade , Intervalo Livre de Doença , Feminino , Humanos , Imunoterapia , Interferon alfa-2 , Neoplasias Renais/mortalidade , Masculino , Pessoa de Meia-Idade , Neovascularização Patológica/tratamento farmacológico , Proteínas Recombinantes/administração & dosagem , Proteínas Recombinantes/uso terapêutico , Resultado do Tratamento , Fator A de Crescimento do Endotélio Vascular/antagonistas & inibidores , Adulto Jovem
16.
J Psychiatr Res ; 161: 218-227, 2023 05.
Artigo em Inglês | MEDLINE | ID: mdl-36940627

RESUMO

BACKGROUND: Heterogeneity and comorbidity in psychiatric disorders are common, however, little is known about the impact on well-being and the role of functional limitations. We aimed to identify transdiagnostic psychiatric symptom profiles and to study their association with well-being and the mediating role of functional limitations in a naturalistic psychiatric patient group. METHODS: We used four disorder-specific questionnaires to assess symptom severity within a sample of 448 psychiatric patients with stress-related and/or neurodevelopmental disorders and 101 healthy controls. Using both exploratory and confirmatory factor analyses we identified transdiagnostic symptom profiles, which we entered into a linear regression analysis to assess their association with well-being and the mediating role of functional limitations in this association. RESULTS: We identified eight transdiagnostic symptom profiles, covering mood, self-image, anxiety, agitation, empathy, non-social interest, hyperactivity and cognitive focus. Mood and self-image showed the strongest association with well-being in both patients and controls, while self-image also showed the highest transdiagnostic value. Functional limitations were significantly associated with well-being and fully mediated the relationship between cognitive focus and well-being. LIMITATIONS: The participant sample consisted of a naturalistic group of out-patients. While this strengthens the ecological validity and transdiagnostic perspective of this study, the patients with a single neurodevelopmental disorder were underrepresented. CONCLUSION: Transdiagnostic symptom profiles are valuable in understanding what reduces well-being in psychiatric populations, thereby opening new avenues for functionally meaningful interventions.


Assuntos
Transtornos de Ansiedade , Ansiedade , Humanos , Transtornos de Ansiedade/epidemiologia , Comorbidade , Afeto
17.
Eur Phys J C Part Fields ; 83(7): 628, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37471210

RESUMO

The double differential cross sections of the Drell-Yan lepton pair (ℓ+ℓ-, dielectron or dimuon) production are measured as functions of the invariant mass mℓℓ, transverse momentum pT(ℓℓ), and φη∗. The φη∗ observable, derived from angular measurements of the leptons and highly correlated with pT(ℓℓ), is used to probe the low-pT(ℓℓ) region in a complementary way. Dilepton masses up to 1TeV are investigated. Additionally, a measurement is performed requiring at least one jet in the final state. To benefit from partial cancellation of the systematic uncertainty, the ratios of the differential cross sections for various mℓℓ ranges to those in the Z mass peak interval are presented. The collected data correspond to an integrated luminosity of 36.3fb-1 of proton-proton collisions recorded with the CMS detector at the LHC at a centre-of-mass energy of 13TeV. Measurements are compared with predictions based on perturbative quantum chromodynamics, including soft-gluon resummation.

18.
Brain Stimul ; 15(5): 1065-1072, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35944604

RESUMO

BACKGROUND: Electroconvulsive therapy (ECT) is an effective treatment for severe depression and induces gray matter (GM) increases in the brain. Small-scale studies suggest that ECT also leads to changes in brain functioning, but findings are inconsistent. In this study, we investigated the influence of ECT on changes in both brain structure and function and their relation to clinical improvement using multicenter neuroimaging data from the Global ECT-MRI Research Collaboration (GEMRIC). METHODS: We analyzed T1-weighted structural magnetic resonance imaging (MRI) and functional resting-state MRI data of 88 individuals (49 male) with depressive episodes before and within one week after ECT. We performed voxel-based morphometry on the structural data and calculated fractional amplitudes of low-frequency fluctuations, regional homogeneity, degree centrality, functional connectomics, and hippocampus connectivity for the functional data in both unimodal and multimodal analyses. Longitudinal effects in the ECT group were compared to repeated measures of healthy controls (n = 27). RESULTS: Wide-spread increases in GM volume were found in patients following ECT. In contrast, no changes in any of the functional measures were observed, and there were no significant differences in structural or functional changes between ECT responders and non-responders. Multimodal analysis revealed that volume increases in the striatum, supplementary motor area and fusiform gyrus were associated with local changes in brain function. CONCLUSION: These results confirm wide-spread increases in GM volume, but suggest that this is not accompanied by functional changes or associated with clinical response. Instead, focal changes in brain function appear related to individual differences in brain volume increases.


Assuntos
Eletroconvulsoterapia , Encéfalo , Depressão/diagnóstico por imagem , Depressão/terapia , Eletroconvulsoterapia/métodos , Substância Cinzenta , Humanos , Imageamento por Ressonância Magnética/métodos , Masculino
19.
Eur Phys J C Part Fields ; 81(9): 800, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34781320

RESUMO

The measurement of the luminosity recorded by the CMS detector installed at LHC interaction point 5, using proton-proton collisions at s = 13 TeV in 2015 and 2016, is reported. The absolute luminosity scale is measured for individual bunch crossings using beam-separation scans (the van der Meer method), with a relative precision of 1.3 and 1.0% in 2015 and 2016, respectively. The dominant sources of uncertainty are related to residual differences between the measured beam positions and the ones provided by the operational settings of the LHC magnets, the factorizability of the proton bunch spatial density functions in the coordinates transverse to the beam direction, and the modeling of the effect of electromagnetic interactions among protons in the colliding bunches. When applying the van der Meer calibration to the entire run periods, the integrated luminosities when CMS was fully operational are 2.27 and 36.3 fb - 1 in 2015 and 2016, with a relative precision of 1.6 and 1.2%, respectively. These are among the most precise luminosity measurements at bunched-beam hadron colliders.

20.
Eur Phys J C Part Fields ; 81(6): 488, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34727143

RESUMO

Production cross sections of the Higgs boson are measured in the H → Z Z → 4 ℓ ( ℓ = e , µ ) decay channel. A data sample of proton-proton collisions at a center-of-mass energy of 13 TeV , collected by the CMS detector at the LHC and corresponding to an integrated luminosity of 137 fb - 1 is used. The signal strength modifier µ , defined as the ratio of the Higgs boson production rate in the 4 ℓ channel to the standard model (SM) expectation, is measured to be µ = 0.94 ± 0.07 (stat) - 0.08 + 0.09 (syst) at a fixed value of m H = 125.38 GeV . The signal strength modifiers for the individual Higgs boson production modes are also reported. The inclusive fiducial cross section for the H → 4 ℓ process is measured to be 2 . 84 - 0.22 + 0.23 (stat) - 0.21 + 0.26 (syst) fb , which is compatible with the SM prediction of 2.84 ± 0.15 fb for the same fiducial region. Differential cross sections as a function of the transverse momentum and rapidity of the Higgs boson, the number of associated jets, and the transverse momentum of the leading associated jet are measured. A new set of cross section measurements in mutually exclusive categories targeted to identify production mechanisms and kinematical features of the events is presented. The results are in agreement with the SM predictions.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA