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At least 1,243 records · Page 69

Measurement of the total cross section and $\rho$-parameter from elastic scattering in pp collisions at $\sqrt{s}=13$ TeV with the ATLAS detector

In a special run of the LHC with β* = 2.5 km, proton–proton elastic-scattering events were recorded at $\sqrt{s}=13$ TeV with an integrated luminosity of $340$ μb -1 using the ALFA subdetector of ATLAS in 2016. The elastic cross section was measured differentially in the Mandelstam t variable in the range from - t = 2.5 · 10 -4 GeV 2 to - t = 0.46 GeV 2 using 6.9 million elastic-scattering candidates. This paper presents measurements of the total cross section σ tot , parameters of the nuclear slope, and the p -parameter defined as the ratio of the real part to the imaginary part of the elastic-scattering amplitude in the limit t → 0. These parameters are determined from a fit to the differential elastic cross section using the optical theorem and different parameterizations of the t-dependence. The results for σ tot and p are σ tot (pp → X) = 104.7 ± 1.1 mb, p = 0.098 ± 0.011. The uncertainty in σ tot is dominated by the luminosity measurement, and in p by imperfect knowledge of the detector alignment and by modelling of the nuclear amplitude.

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Measurements of the Higgs boson production cross section and couplings in the W boson pair decay channel in proton-proton collisions at $\sqrt{s}=13\,\text {Te\hspace{-.08em}V} $

Production cross sections of the standard model Higgs boson decaying to a pair of W bosons are measured in proton-proton collisions at a center-of-mass energy of 13$\,\text {Te\hspace{-.08em}V}$. The analysis targets Higgs bosons produced via gluon fusion, vector boson fusion, and in association with a W or Z boson. Candidate events are required to have at least two charged leptons and moderate missing transverse momentum, targeting events with at least one leptonically decaying W boson originating from the Higgs boson. Results are presented in the form of inclusive and differential cross sections in the simplified template cross section framework, as well as couplings of the Higgs boson to vector bosons and fermions. The data set collected by the CMS detector during 2016–2018 is used, corresponding to an integrated luminosity of 138$\,\text {fb}^{-1}$. The signal strength modifier $\mu $, defined as the ratio of the observed production rate in a given decay channel to the standard model expectation, is measured to be $\mu = 0.95^{+0.10}_{-0.09}$. All results are found to be compatible with the standard model within the uncertainties.

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Measurement of the $H \rightarrow \gamma \gamma $ and $H \rightarrow ZZ^* \rightarrow 4 \ell $ cross-sections in $pp$ collisions at $\sqrt{s}=13.6$ TeV with the ATLAS detector

The inclusive Higgs boson production crosssection is measured in the di-photon and the Z Z* → 4$\ell$ decay channels using 31.4 and 29.0 fb –1 of pp collision data respectively, collected with the ATLAS detector at a centreof-mass energy of $\sqrt{s}$ = 13.6 TeV. To reduce the model dependence, the measurement in each channel is restricted to a particle-level phase space that closely matches the channel’s detector-level kinematic selection, and it is corrected for detector effects. These measured fiducial cross-sections are σ fid,γγ = $76^{+14}_{–13}$ fb, and $σ_{\text{fid,4}\ell}$ = 2.80 ± 0.74 fb, in agreement with the corresponding Standard Model predictions of 67.6±3.7 fb and 3.67±0.19 fb. Assuming Standard Model acceptances and branching fractions for the two channels, the fiducial measurements are extrapolated to the full phase space yielding total cross-sections of σ (pp → H) = $67^{+12}_{–11}$ pb and 46±12 pb at 13.6 TeV from the di-photon and Z Z* → 4$\ell$ measurements respectively. The two measurements are combined into a total cross-section measurement of σ (pp → H) = 58.2±8.7 pb, to be compared with the Standard Model prediction of σ (pp → H) SM = 59.9 ± 2.6 pb.

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Measurement of the production cross section for a W boson in association with a charm quark in proton–proton collisions at $\sqrt{s} = 13\,\hbox {TeV}$

The strange quark content of the proton is probed through the measurement of the production cross section for a W boson and a charm (c) quark in proton–proton collisions at a center-of-mass energy of 13$\,\text {Te}\hspace{-.08em}\text {V}$. The analysis uses a data sample corresponding to a total integrated luminosity of 138$\,\text {fb}^{-1}$ collected with the CMS detector at the LHC. The W bosons are identified through their leptonic decays to an electron or a muon, and a neutrino. Charm jets are tagged using the presence of a muon or a secondary vertex inside the jet. The $\hbox {W}+\hbox {c}$ production cross section and the cross section ratio $R_\textrm{c}^{\pm }= \sigma ({\hbox {W}}^{+}+\bar{\text {c}})/\sigma (\hbox {W}^{-}+{\textrm{c}})$ are measured inclusively and differentially as functions of the transverse momentum and the pseudorapidity of the lepton originating from the W boson decay. The precision of the measurements is improved with respect to previous studies, reaching 1% in $R_\textrm{c}^{\pm }= 0.950 \pm 0.005\,\text {(stat)} \pm 0.010 \,\text {(syst)} $. The measurements are compared with theoretical predictions up to next-to-next-to-leading order in perturbative quantum chromodynamics.

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Measurement of multidifferential cross sections for dijet production in proton–proton collisions at $\sqrt{s}$ = 13 TeV

A measurement of the dijet production cross section is reported based on proton–proton collision data collected in 2016 at $\sqrt{s}$ = 13 TeV by the CMS experiment at the CERN LHC, corresponding to an integrated luminosity of up to 36.3 fb –1 . Jets are reconstructed with the anti-$k$ T algorithm for distance parameters of R = 0.4 and 0.8. Cross sections are measured double-differentially (2D) as a function of the largest absolute rapidity |y| max of the two jets with the highest transverse momenta $p$ T and their invariant mass $m$ 1,2 , and triple-differentially (3D) as a function of the rapidity separation $y$*, the total boost $y$ b , and either $m$ 1,2 or the average $p$ T of the two jets. The cross sections are unfolded to correct for detector effects and are compared with fixed-order calculations derived at next-to-next-to-leading order in perturbative quantum chromodynamics. The impact of the measurements on the parton distribution functions and the strong coupling constant at the mass of the Z boson is investigated, yielding a value of $α$ S ($m$ Z ) = 0.1179 ± 0.0019.

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Measurement of W±-boson differential cross-sections in proton–proton collisions with low pile-up data at s=5.02 TeV and 13TeV with the ATLAS detector

High precision single-differential W±$$W^\pm $$-boson production cross-sections as a function of electron or muon transverse momentum pT$$p_\textrm{T}$$ or their pseudorapity η$$\eta $$, as well as double-differential cross-sections as functions of these variables, are measured in proton–proton collisions at centre-of-mass energies s=5.02$$\sqrt{s}=5.02$$ TeV and 13 TeV. The W-boson charge asymmetry as a function of lepton η$$\eta $$ is also measured. The data, collected in dedicated runs at reduced instantaneous luminosity with the ATLAS detector at the Large Hadron Collider, correspond to integrated luminosities of 255 pb-1$$^{-1}$$ at 5.02 TeV and 338 pb-1$$^{-1}$$ at 13 TeV. The measurements are in agreement with Standard-Model predictions calculated at next-to-next-to-leading-order in the strong coupling constant αs$$\alpha _s$$ including transverse-momentum resummation at next-to-next-to-leading logarithmic accuracy using several parton distribution functions. The impact of the measured differential cross-sections as a function of lepton η$$\eta $$ on the determination of these functions is studied using a profiling technique.

Aad, G↗

Metabolomics Collision Cross Section Database and Server

This is a the code and data for a website created to display collision cross section data for metabolites and small molecules. This repository hosts two things. First is the source code (js) for a website created to display collision cross section data for metabolites and other small molecules. The second is the underlying CCS dataset. The growing interest in metabolomic and exposomic studies is also inciting a need for new techniques to analyze these diverse molecules. Mass spectrometry-based studies are often preferred for the confident identification of small molecules. Ion mobility spectrometry (IMS) is capable of separating molecules that have the same m/z but different conformational arrangements, which is very useful in metabolomic and exposomic analyses. As the desire for IMS measurements of metabolites continues to grow, so does the need for high quality collision cross section (CCS) values.

Payne, Sam↗

Damage Pseudo Cross Section Generator

This software is a python script for generating group damage pseudo-cross-sections for specific elements, and tabulating them in forms useful to python or to office-open workbooks (xlsx). The damage pseudo-cross-section is needed for calculating how much neutron radiation damage a structural material receives in a reactor measured in displacements per atom (DPA). The process of generating these pseudo-cross-sections is laborious as it requires running the nuclear data processing code, NJOY, for hundreds of isotopes, and then post-processing the data. This also allows many opportunities for human error to be involved. This script eliminates these problems by fully automating the process.

Gale, MicahD.↗

Measurement of the production cross section of an isolated photon associated with jets in proton-proton collisions at s = 7 TeV with the ATLAS detector

CERN-LHC. A measurement of the cross section for the production of an isolated photon in association with jets in proton-proton collisions at a center-of-mass energy sqrt(s) = 7 TeV is presented. Photons are reconstructed in the pseudorapidity range |eta(gamma)| < 1.37 and with a transverse energy E_T(gamma) > 25 GeV. Jets are reconstructed in the rapidity range |y(jet)| < 4.4 and with a transverse momentum p_T(jet) > 20 GeV. The differential cross section dsigma/dE_T(gamma) is measured, as a function of the photon transverse energy, for three different rapidity ranges of the leading-p_T jet: |y(jet)| < 1.2, 1.2 <= |y(jet)| < 2.8 and 2.8 <= |y(jet)| < 4.4. For each rapidity configuration the same-sign (eta(gamma)y(jet) >= 0) and opposite-sign (eta(gamma)y(jet) < 0) cases are studied separately. The results are based on an integrated luminosity of 37 pb-1, collected with the ATLAS detector at the LHC. Next-to-leading order perturbative QCD calculations are found to be in fair agreement with the data, except for E_T(gamma) <~ 45 GeV, where the theoretical predictions overestimate the measured cross sections.

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Measurement of dijet cross sections in p p collisions at 7 TeV centre-of-mass energy using the ATLAS detector

CERN-LHC. Double-differential dijet cross sections measured in pp collisions at the LHC with a 7 TeV centre-of-mass energy are presented as functions of dijet mass and rapidity separation of the two highest-pT jets. These measurements are obtained using data corresponding to an integrated luminosity of 4.5 fb^-1, recorded by the ATLAS detector in 2011. The data are corrected for detector effects so that cross sections are presented at the particle level. Cross sections are measured up to 5 TeV dijet mass using jets reconstructed with the anti-kt algorithm for values of the jet radius parameter of 0.4 and 0.6.

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Measurements of the W production cross sections in association with jets with the ATLAS detector

This paper presents cross sections for the production of a W boson in association with jets, measured in proton--proton collisions at sqrt(s)=7 TeV with the ATLAS experiment at the Large Hadron Collider. With an integrated luminosity of 4.6 fb^{-1}, this data set allows for an exploration of a large kinematic range, including jet production up to a transverse momentum of 1 TeV and multiplicities up to seven associated jets. The production cross sections for W bosons are measured in both the electron and muon decay channels. Differential cross sections for many observables are also presented including measurements of the jet observables such as the rapidities and the transverse momenta as well as measurements of event observables such as the scalar sums of the transverse momenta of the jets. The measurements are compared to numerous QCD predictions including next-to-leading-order perturbative calculations, resummation calculations and Monte Carlo generators

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Measurement of the inclusive isolated prompt photons cross section in pp collisions at s = 7 TeV with the ATLAS detector using 4.6 fb &#x2212; 1

CERN-LHC. A measurement of the cross section for the production of isolated prompt photons in pp collisions at a center-of-mass energy sqrt(s) = 7 TeV is presented. The results are based on an integrated luminosity of 4.6 fb-1 collected with the ATLAS detector at the LHC. The cross section is measured as a function of photon pseudorapidity and transverse energy in the kinematic range between 100 GeV and 1000 GeV and in the regions of pseudorapidity less than 1.37 and between 1.52 and 2.37. The results are compared to leading-order parton-shower Monte Carlo models and next-to-leading-order perturbative QCD calculations. Next-to-leading-order perturbative QCD calculations agree well with the measured cross sections as a function of transverse energy and pseudorapidity

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Measurement of the production cross section of jets in association with a Z boson in pp collisions at s = 7 TeV with the ATLAS detector

CERN-LHC. Measurements of cross sections for the production of jets in association with a Z0 boson in proton-proton collisions at a centre of mass energy of 7 TeV. The 2011 data sample used has an integrated luminosity of 4.6 fb^{-1}. Inclusive cross sections for Z0 decaying into either electron or muon pairs with jets of transverse momentum above 30 GeV and |rapidity| less than 4.4 are presented along with a detailed breakdown of the systematic errors in the measurements. Data are given here for the individual electron and muon channels as well as for the combined data as shown in the paper. The combined cross section has been extrapolated to the common phase space |eta|<2.5 and pT>20 GeV, similar to the 2010 analysis.

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Measurement of the b-hadron production cross section using decays to D &#x2217; &#x3BC; &#x2212; X final states in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector

CERN-LHC. The b-hadron production cross section is measured with the ATLAS detector in pp collisions at sqrt(s) = 7 TeV, using 3.3 pb^-1 of integrated luminosity, collected during the 2010 LHC run. The b-hadrons are selected by partially reconstructing D*muX final states. Differential cross sections are measured as functions of the transverse momentum and pseudorapidity. The measured production cross section for a b-hadron with pT>9 GeV and |eta|<2.5 is 32.7 pm 0.8 (stat) ^{+4.5}_{-6.8} (syst) ub, higher than the next-to-leading-order QCD predictions but consistent within the experimental and theoretical uncertainties. Data taken from the RIVET analysis code.

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Measurement of the inclusive jet cross-section in proton-proton collisions at s = 7 TeV using 4.5 fb &#x2212; 1 of data with the ATLAS detector

CERN-LHC. Double-differential inclusive jet cross-sections measured in pp collisions at the LHC with a 7 TeV centre-of-mass energy are presented as functions of jet transverse momentum and absolute value of rapidity. These measurements are obtained using data corresponding to an integrated luminosity of 4.5 fb^-1, recorded by the ATLAS detector in 2011. The data are corrected for detector effects so that cross-sections are presented at the particle level. Cross-sections are measured up to jet transverse momentum of 2 TeV using jets reconstructed with the anti-kt algorithm with the jet radius parameter R = 0.4 and 0.6.

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Measurement of the b b &#x2015; dijet cross section in p p collisions at s = 7 TeV with the ATLAS detector

CERN-LHC. Measurement of the dijet production cross section for jets containing a b-hadron (b-jets) in proton proton collisions at a centre-of-mass energy of 7 TeV, with 4.2 fb^-1 of data collected by the ATLAS detector in 2011. The cross section is measured for events with two identified b-jets with a transverse momentum pT > 20 GeV and a minimum separation in the eta-phi plane of Delta R = 0.4. At least one of the jets in the event is required to have pT > 270 GeV. The cross section is measured differentially as a function of the dijet invariant mass, dijet transverse momentum, boost of the dijet system, and of the rapidity difference, azimuthal angle and angular distance between the b-jets.

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Measurement of fiducial and differential W + W &#x2212; production cross-sections at s = 13 TeV with the ATLAS detector

A measurement of fiducial and differential cross-sections for W+W- production in proton-proton collisions at sqrt(s)=13 TeV with the ATLAS experiment at the Large Hadron Collider using an integrated luminosity of 36.1fb-1 is presented. Events with one electron and one muon are selected, corresponding to the decay of the diboson system as WW->e nu mu nu. To suppress top-quark background, events containing jets with a transverse momentum exceeding 35 GeV are not included in the measurement phase space. The fiducial cross-section, six differential distributions and the cross-section as a function of the jet-veto transverse momentum threshold are measured and compared with several theoretical predictions. Constraints on anomalous weak boson self-interactions are also presented in the framework of a dimension-six effective field theory.

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Measurement of the inclusive cross-section for the production of jets in association with a Z boson in proton-proton collisions at 8 TeV using the ATLAS detector

The inclusive cross-section for jet production in association with a Z boson decaying into an electron-positron pair is measured as a function of the transverse momentum and the absolute rapidity of jets using 19.9 fb^-1 of sqrt(s) = 8 TeV proton-proton collision data collected with the ATLAS detector at the Large Hadron Collider. The measured Z + jets cross-section is unfolded to the particle level.The cross-section is compared with state-of-the-art Standard Model calculations, including the next-to-leading-order and next-to-next-to-leading-order perturbative QCD calculations, corrected for non-perturbative and QED radiation effects.The results of the measurements cover final-state jets with transverse momenta up to 1 TeV, and show good agreement with fixed-order calculations.

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