Pair Cross Section Research Articles

Measurement of vector boson production cross sections and their ratios using pp collisions at [formula omitted] TeV with the ATLAS detector

Fiducial and total W± and Z boson cross sections, their ratios and the ratio of top-antitop-quark pair and W-boson fiducial cross sections are measured in proton–proton collisions at a centre-of-mass energy of s=13.6TeV, corresponding to an integrated luminosity of 29 fb−1 of data collected in 2022 by the ATLAS experiment at the Large Hadron Collider. The measured fiducial cross-section values for W+→ℓ+ν, W−→ℓ−ν¯, and Z→ℓ+ℓ− (ℓ=e or μ) boson productions are 4250±150pb, 3310±120pb, and 744±20pb, respectively, where the uncertainty is the total uncertainty, including that arising from the luminosity of about 2.2%. The measurements are in agreement with Standard-Model predictions calculated at next-to-next-to-leading-order in αs, next-to-next-to-leading logarithmic accuracy and next-to-leading-order electroweak accuracy.

Charmed meson pair production in high‐energy pp$$ pp $$ collisions within the QCD color dipole approach

AbstractA study of double‐charmed meson production in high‐energy proton–proton collisions at the Large Hadron Collider is presented. Considering the color dipole formalism developed in the transverse momentum representation along with the double parton scattering mechanism, predictions are made for the transverse momentum differential cross section for different pairs of ‐mesons. The theoretical results cover the center‐of‐mass energy and forward rapidities available by the LHCb experiment. The proton–proton results considering different unintegrated gluon distributions are compared to the respective data collected at the LHC.

Recent results of Baryon electromagnetic form factors at BESIII

Baryon Electromagnetic Form Factors are essential for testing ground state models of nucleon internal structures. At the BESIII experiment, a comprehensive study has been conducted on the electromagnetic form factors of various baryons. The electromagnetic form factor ratio of the nucleon (proton and neutron), denoted as |GE/GM|, has been determined with high precision. And the study at BESIII has explored the cross sections of various baryon pairs, including Λ, Λc, Σ, Ξ, Ω and Δ from their respective thresholds. In the study conducted at BESIII, threshold effects have been observed in some baryon pairs, enhancing our understanding of these baryon interactions.

Baryon electromagnetic form factors at BESIII

The electromagnetic form factors (EMFFs) of various baryons have been studied at BESIII. The proton EMFF ratio |GE/GM| is determined precisely. Recent results of neutron EMFFs show great improvement comparing with previous experiments. Cross sections of various baryon pairs (Λ, Σ, Ξ, Λc) are studied from their thresholds and threshold effects are observed.

Double charmed meson in pp and pA collisions production at the LHC within the dipole approach in momentum representation

A study of double charmed meson production in proton–proton and proton–nucleus collisions at the LHC energies is performed. Based on the color dipole formalism developed in the transverse momentum representation and the double parton scattering mechanism, predictions are made for the transverse momentum differential cross section for different pairs of D-mesons. The theoretical results consider the center-of-mass energy and forward rapidities associated to the measurements by the LHCb Collaboration. The results considering different unintegrated gluon distributions are presented and compared to data and predictions for proton–nucleus collisions are provided.

Effective field theories for dark matter pairs in the early universe: cross sections and widths

In order to predict the cosmological abundance of dark matter, an estimation of particle rates in an expanding thermal environment is needed. For thermal dark matter, the non-relativistic regime sets the stage for the freeze-out of the dark matter energy density. We compute transition widths and annihilation, bound-state formation, and dissociation cross sections of dark matter fermion pairs in the unifying framework of non-relativistic effective field theories at finite temperature, with the thermal bath modeling the thermodynamical behaviour of the early universe. We reproduce and extend some known results for the paradigmatic case of a dark fermion species coupled to dark gauge bosons. The effective field theory framework allows to highlight their range of validity and consistency, and to identify some possible improvements.

Drell-Yan transverse momentum dependence over a wide mass range

The measurement of the differential cross section for opposite-charge electron or muon pairs as a function of transverse momentum is presented in this report. The measurement is performed in several invariant mass bins, from 50 GeV to 1 TeV. The results are presented for inclusive production as well as for the production in association with one jet. The results are obtained from proton-proton interactions recorded with the CMS detector at the LHC at a centre-of-mass energy of 13 TeV during 2016. The integrated luminosity of the data is 36.3fb−1. The measurements are compared with several theoretical predictions.

Упругое рассеяние атома рутения на атомах Si и O в диапазоне относительных кинетических энергий 2-200 eV

Interconnector technologies of a new generation involve use of ruthenium. The high cost of experimental study of sputtering and etching of trenches in Ru leads to the need to optimize it by modeling, requiring knowledge of the cross sections of elementary processes of interaction of plasma particles with Ru. In this work, the binary interatomic potentials of Ru-Ru and Ru-Si pairs, tested by molecular dynamics method, and the Ru-O one calculated using the multi reference configurational interaction MRCI/AV5Z were used to calculate the elastic scattering cross sections of the atomic pairs in the energy range typical for plasma etching chambers.

Elastic scattering of ruthenium atoms from Si and O atoms in the range of relative kinetic energies of 2-200 eV

Interconnector technologies of a new generation involve the use of ruthenium. The high cost of experimental study of sputtering and etching of trenches in Ru leads to the need to optimize it by modeling that requires knowledge of the cross sections of elementary processes of interaction of plasma particles with Ru. In this work, the binary interatomic potentials of Ru-Ru and Ru-Si pairs tested by the molecular dynamics method, and the Ru-O one calculated by the method of multi-reference configurational interaction MRCI/AV5Z were used to calculate the elastic scattering cross sections of the atomic pairs in the energy range typical of plasma etching chambers. Keywords: ruthenium, elastic scattering, cross sections, sputtering, binary potential.

Heavy-ion fusion reactions of astrophysical interest

The hindrance in fusion of heavy-ion reactions crops up in the region of extreme sub-barrier energies. This phenomenon can be effectively analyzed using a simple diffused barrier formula derived assuming a Gaussian distribution of fusion barrier heights. Folding the Gaussian barrier distribution with the classical expression for the fusion cross section for a fixed barrier, the fusion cross section is obtained. The energy dependence of the fusion cross section provides good description to the existing data on sub-barrier heavy-ion fusion for lighter systems of astrophysical interest. Using this simple formula, an analysis has been presented from $^{16}$O + $^{18}$O to $^{12}$C + $^{198}$Pt, all of which were measured down to $<$ 10 $\mu$b. The agreement of the present analysis with the measured values is better than those calculated even from the sophisticated coupled channels calculations. The relatively smooth variation of the three parameters of this formula implies that it may be exploited to estimate the excitation function or to extrapolate cross sections for pairs of interacting nuclei which are yet to be measured. Possible extensions of the present methodology and its limitations have also been discussed.

Top quark pair and single top cross sections and ttX (CMS)

Latest results on inclusive and differential top quark pair and single top quark production cross sections are presented using proton-proton collision data collected by the CMS experiment. The differential cross sections are measured as a function of various kinematic observables of the top quarks and the jets and leptons of the event final state. The results are confronted with precise theory calculations and used to constrain Standard Model parameters. Measurements are performed also with high p_TpT top quarks, i.e., in boosted regimes.

Prompt and non-prompt J/ψ production cross sections at midrapidity in proton-proton collisions at sqrt{mathrm{s}} = 5.02 and 13 TeV

The production of J/ψ is measured at midrapidity (|y| < 0.9) in proton-proton collisions at sqrt{s} = 5.02 and 13 TeV, through the dielectron decay channel, using the ALICE detector at the Large Hadron Collider. The data sets used for the analyses correspond to integrated luminosities of mathcal{L} int = 19.4 ± 0.4 nb−1 and mathcal{L} int = 32.2 ± 0.5 nb−1 at sqrt{s} = 5.02 and 13 TeV, respectively. The fraction of non-prompt J/ψ mesons, i.e. those originating from the decay of beauty hadrons, is measured down to a transverse momentum pT = 2 GeV/c (1 GeV/c) at sqrt{s} = 5.02 TeV (13 TeV). The pT and rapidity (y) differential cross sections, as well as the corresponding values integrated over pT and y, are carried out separately for prompt and non-prompt J/ψ mesons. The results are compared with measurements from other experiments and theoretical calculations based on quantum chromodynamics (QCD). The shapes of the pT and y distributions of beauty quarks predicted by state-of-the-art perturbative QCD models are used to extrapolate an estimate of the mathrm{b}overline{mathrm{b}} pair cross section at midrapidity and in the total phase space. The total mathrm{b}overline{mathrm{b}} cross sections are found to be {sigma}_{mathrm{b}overline{mathrm{b}}} = 541 ± 45 (stat.) ± 69 {left(mathrm{syst}.right)}_{-12}^{+10} (extr.) μb and {sigma}_{mathrm{b}overline{mathrm{b}}} = 218±37 (stat.)±31 {left(mathrm{syst}.right)}_{-9.1}^{+8.2} (extr.) μb at sqrt{s} = 13 and 5.02 TeV, respectively. The value obtained from the combination of ALICE and LHCb measurements in pp collisions at sqrt{s} = 13 TeV is also provided.

Coupled-channel meson-meson scattering in the diabatic framework

We apply the diabatic framework, a QCD-based formalism for the unified study of quarkoniumlike systems in terms of heavy quark-antiquark and open-flavor meson-meson components, to the description of coupled-channel meson-meson scattering. For this purpose, we first introduce a numerical scheme to find the solutions of the diabatic Schr\"odinger equation for energies in the continuum, then we derive a general formula for calculating the meson-meson scattering amplitudes from these solutions. We thus obtain a completely nonperturbative procedure for the calculation of open-flavor meson-meson scattering cross sections from the diabatic potential, which is directly connected to lattice QCD calculations. A comprehensive analysis of various elastic cross sections for open-charm and open-bottom meson-meson pairs is performed in a wide range of the center-of-mass energies. The relevant structures are identified, showing a spectrum of quasiconventional and unconventional quarkoniumlike states. In addition to the customary Breit-Wigner peaks, we obtain nontrivial structures such as threshold cusps and minimums. Finally, our results are compared with existing data and with results from our previous bound-state--based analysis, finding full compatibility with both.

Probing the muon g−2 anomaly with the Higgs boson at a muon collider

We point out that heavy new physics contributions in leptonic dipole moments and high-energy cross sections of lepton pairs into Higgs bosons and photons are connected model-independently. In particular, we demonstrate that a muon collider, running at center-of-mass energies of several TeV, can provide a unique test of new physics in the muon $g\ensuremath{-}2$ through the study of high-energy processes such as ${\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}\ensuremath{\rightarrow}h\ensuremath{\gamma}$. This high-energy test would be of the utmost importance to shed light on the longstanding muon $g\ensuremath{-}2$ anomaly as it is not affected by the hadronic and experimental uncertainties entering the current low-energy determination of the muon $g\ensuremath{-}2$. Furthermore, we show that the current bound on the muon electric dipole moment can be improved by three orders of magnitude, down to $\mathrm{few}\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}22}\text{ }\text{ }e\text{ }\mathrm{cm}$.

First measurement of the cross section for top quark pair production with additional charm jets using dileptonic final states in pp collisions at [formula omitted

The first measurement of the inclusive cross section for top quark pairs (tt‾) produced in association with two additional charm jets is presented. The analysis uses the dileptonic final states of tt‾ events produced in proton-proton collisions at a centre-of-mass energy of 13 TeV. The data correspond to an integrated luminosity of 41.5fb−1, recorded by the CMS experiment at the LHC. A new charm jet identification algorithm provides input to a neural network that is trained to distinguish among tt‾ events with two additional charm (tt‾cc‾), bottom (tt‾bb‾), and light-flavour or gluon (tt‾LL) jets. By means of a template fitting procedure, the inclusive tt‾cc‾, tt‾bb‾, and tt‾LL cross sections are simultaneously measured, together with their ratios to the inclusive tt‾ + two jets cross section. This provides measurements of the tt‾cc‾ and tt‾bb‾ cross sections of 10.1±1.2(stat)±1.4(syst)pb and 4.54±0.35(stat)±0.56(syst)pb, respectively, in the full phase space. The results are compared and found to be consistent with predictions from two different matrix element generators with next-to-leading order accuracy in quantum chromodynamics, interfaced with a parton shower simulation.

Observation of Enhanced Double Parton Scattering in Proton-Lead Collisions at sqrt[s_{NN}]=8.16 TeV.

A study of prompt charm-hadron pair production in proton-lead collisions at sqrt[s_{NN}]=8.16 TeV is performed using data corresponding to an integrated luminosity of about 30 nb^{-1}, collected with the LHCb experiment. Production cross sections for different pairs of charm hadrons are measured and kinematic correlations between the two charm hadrons are investigated. This is the first measurement of associated production of two charm hadrons in proton-lead collisions. The results confirm the predicted enhancement of double parton scattering production in proton-lead collisions compared to the single parton scattering production.

Measurements of production cross sections of WZ and same-sign WW boson pairs in association with two jets in proton-proton collisions at [formula omitted

Measurements of production cross sections of WZ and same-sign WW boson pairs in association with two jets in proton-proton collisions at s=13TeV at the LHC are reported. The data sample corresponds to an integrated luminosity of 137fb−1, collected with the CMS detector during 2016–2018. The measurements are performed in the leptonic decay modes ▪ and ▪, where ℓ,ℓ′=e, ▪. Differential fiducial cross sections as functions of the invariant masses of the jet and charged lepton pairs, as well as of the leading-lepton transverse momentum, are measured for W±W± production and are consistent with the standard model predictions. The dependence of differential cross sections on the invariant mass of the jet pair is also measured for WZ production. An observation of electroweak production of WZ boson pairs is reported with an observed (expected) significance of 6.8 (5.3) standard deviations. Constraints are obtained on the structure of quartic vector boson interactions in the framework of effective field theory.

Analysis of the dynamics of Li7 -induced fusion with natZr up to 44 MeV

An experimental study on the fusion dynamics of the $^{7}\mathrm{Li}+^{\text{nat}}\mathrm{Zr}$ reaction has been carried out within the 4.0 to 6.3 MeV/nucleon energy range by measuring cross sections of the populated residues with the help of $\ensuremath{\gamma}$-ray spectrometry. The equilibrium and pre-equilibrium reaction models have been used in the framework of empire3.2.2 to analyze the measured residual cross sections to shed light on the reaction mechanism involved in it. It indicates that the complete and incomplete fusion of $^{7}\mathrm{Li}$ contribute to the residual cross sections. Thus, the strength of incomplete fusion has been derived and is compared with other $^{7}\mathrm{Li}$-induced reactions in the similar mass range. Further, coupled channel (CC) calculations have been carried out to understand the effect of couplings in the fusion process. It has been observed that the fusion cross section is suppressed in $^{7}\mathrm{Li}+^{\text{nat}}\mathrm{Zr}$ reaction as compared to CC calculations far above the Coulomb barrier. The isomeric cross-section ratio has also been obtained from the measured cross sections of the isomeric pairs of $^{93,95}\mathrm{Tc}$ that describes the role of angular momentum and relative spins of the ground and isomeric states with the variation of bombarding energy.

Update of inclusive cross sections of single and pairs of identified light charged hadrons

We report new measurements of the production cross sections of pairs of charged pions and kaons as a function of their fractional energies using various fractional-energy definitions. Two different fractional-energy definitions were used and compared to the conventional fractional-energy definition reported previously. The new variables aim at either identifying dihadron cross sections in terms of single-hadron fragmentation functions, or to provide a means of characterizing the transverse momentum created in the fragmentation process. The results were obtained applying the updated initial-state radiation correction used in other recent Belle publications on light-hadron production cross sections. In addition, production cross sections of single charged pions, kaons, and protons were also updated using this initial-state radiation correction. The cross sections are obtained from a $558\,{\rm fb}^{-1}$ data sample collected at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider.

Estimates of the X(3872) cross section at a hadron collider

The claim that the $X(3872)$ meson cannot be a charm-meson molecule because its prompt production cross section at hadron colliders is too large is based on an upper bound in terms of a cross section for producing charm-meson pairs. Assuming $X$ is sufficiently weakly bound, we derive an equality between the $X$ cross section and a charm-meson pair cross section that takes into account the threshold enhancement from the $X$ resonance. The cross section for producing $X$ is equal to that for producing $D^{*0} \bar{D}^0$ integrated up to a relative momentum $k_\mathrm{max} = 7.7\,\gamma_X$, where $\gamma_X$ is the binding momentum of $X$. We also derive an order-of-magnitude estimate of the $X$ cross section in terms of a naive charm-meson pair cross section that does not take into account the threshold enhancement, such as that produced by a Monte Carlo event generator. The cross section for producing $X$ can be approximated by the naive cross section for producing $D^{*0} \bar{D}^0$ integrated up to a relative momentum $k_\mathrm{max}$ of order $(m_\pi^2 \gamma_X)^{1/3}$. The estimates of the prompt $X$ cross section at hadron colliders are consistent with the cross sections observed at the Tevatron and the LHC.