(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image) The production cross-section of J/ψ pairs is measured using a data sample of pp collisions collected by the LHCb experiment ...at a centre-of-mass energy of ... TeV, corresponding to an integrated luminosity of 279 ±11 pb−1. The measurement is performed for J/ψ mesons with a transverse momentum of less than 10 GeV/c in the rapidity range 2.0 < y < 4.5. The production cross-section is measured to be 15.2 ± 1.0 ± 0.9 nb. The first uncertainty is statistical, and the second is systematic. The differential cross-sections as functions of several kinematic variables of the J/ψ pair are measured and compared to theoretical predictions. Figure not available: see fulltext.
Search for the charmless decay Adeva, B; Ajaltouni, Z; Amhis, Y ...
The journal of high energy physics,
05/2017, Letnik:
2017, Številka:
5
Journal Article
Recenzirano
Odprti dostop
A search for the charmless Figure not available: see fulltext.
Study of the D^sup 0^p amplitude decays Adeva, B; Ajaltouni, Z; Amhis, Y ...
The journal of high energy physics,
05/2017, Letnik:
2017, Številka:
5
Journal Article
Recenzirano
Odprti dostop
An amplitude analysis of the decay Lambda ^sub b ^ ^sup 0^ right arrowD ^sup 0^ ppi ^sup -^ is performed in the part of the phase space containing resonances in the D ^sup 0^ p channel. The study is ...based on a data sample corresponding to an integrated luminosity of 3.0 fb^sup -1^ of pp collisions recorded by the LHCb experiment. The spectrum of excited Lambda ^sub c ^ ^sup +^ states that decay into D ^sup 0^ p is studied. The masses, widths and quantum numbers of the Lambda^sub c^(2880)^sup +^ and Lambda^sub c^(2940)^sup +^ resonances are measured. The constraints on the spin and parity for the Lambda^sub c^(2940)^sup +^ state are obtained for the first time. A near-threshold enhancement in the D ^sup 0^ p amplitude is investigated and found to be consistent with a new resonance, denoted the Lambda^sub c^(2860)^sup +^, of spin 3/2 and positive parity. Figure not available: see fulltext.
A measurement of mixing and \(C\!P\) violation in neutral charm mesons is performed using data reconstructed in proton-proton collisions collected by the LHCb experiment from 2016 to 2018, ...corresponding to an integrated luminosity of 5.4\(\textrm{fb}^{-1}\). A total of \(30.6\) million \(D^{0}\rightarrow K^{0}_{\mathrm{S}}\pi^{+}\pi^{-}\) decays are analyzed using a method optimized for the measurement of the mass difference between neutral charm-meson eigenstates. Allowing for \(C\!P\) violation in mixing and in the interference between mixing and decay, the mass and decay-width differences are measured to be \(x_{C\!P} = \left3.97\pm0.46\textrm{(stat)}\pm 0.29\textrm{(syst)}\right\times10^{-3}\) and \(y_{C\!P} = \left4.59\pm1.20\textrm{(stat)}\pm0.85\textrm{(syst)}\right\times10^{-3}\), respectively. The \(C\!P\)-violating parameters are measured as \(\Delta x = \left-0.27\pm0.18\textrm{(stat)}\pm0.01\textrm{(syst)}\right\times10^{-3}\) and \(\Delta y = \left0.20\pm0.36\textrm{(stat)}\pm0.13\textrm{(syst)}\right\times10^{-3}\). This is the first observation of a nonzero mass difference in the \(D^0\) meson system, with a significance exceeding seven standard deviations. The data are consistent with \(C\!P\) symmetry, and improve existing constraints on the associated parameters.
A combined amplitude analysis is performed for the decays \(B^0 \rightarrow \overline{D}^0 D^+_s\pi^-\) and \(B^+\rightarrow D^- D^+_s\pi^+\), which are related by isospin symmetry. The analysis is ...based on data collected by the LHCb detector in proton-proton collisions at center-of-mass energies of 7, 8 and 13\(\,\rm{TeV}\). The full data sample corresponds to an integrated luminosity of 9\(\,\rm{fb^{-1}}\). Two new resonant states with masses of \(2.908\pm0.011\pm0.020\,\rm{GeV}\) and widths of \(0.136\pm0.023\pm0.011\,\rm{GeV}\) are observed, which decay to \(D^+_s\pi^+\) and \(D^+_s\pi^-\) respectively. The former state indicates the first observation of a doubly charged open-charm tetraquark state with minimal quark content \(c\bar{s}u\bar{d}\), and the latter state is a neutral tetraquark composed of \(c\bar{s}\bar{u}d\) quarks. Both states are found to have spin-parity \(0^+\), and their resonant parameters are consistent with each other, which suggests that they belong to an isospin triplet.
The Standard Model of particle physics currently provides our best description of fundamental particles and their interactions. The theory predicts that the different charged leptons, the electron, ...muon and tau, have identical electroweak interaction strengths. Previous measurements have shown a wide range of particle decays are consistent with this principle of lepton universality. This article presents evidence for the breaking of lepton universality in beauty-quark decays, with a significance of 3.1 standard deviations, based on proton-proton collision data collected with the LHCb detector at CERN's Large Hadron Collider. The measurements are of processes in which a beauty meson transforms into a strange meson with the emission of either an electron and a positron, or a muon and an antimuon. If confirmed by future measurements, this violation of lepton universality would imply physics beyond the Standard Model, such as a new fundamental interaction between quarks and leptons.
A search is performed for massive long-lived particles (LLP) decaying semileptonically into a muon and two quarks. Two kinds of LLP production processes were considered. In the first, a Higgs-like ...boson with mass from 30 to 200 GeV is produced by gluon fusion and decays into two LLPs. The analysis covers LLP mass values from 10 GeV up to about one half the Higgs-like boson mass. The second LLP production mode is directly from quark interactions, with LLP masses from 10 to 90 GeV. The LLP lifetimes considered range from 5 to 200 ps. This study uses LHCb data collected from proton-proton collisions at sqrt(s)=13 TeV, corresponding to an integrated luminosity of 5.4 1/fb. No evidence of these long-lived states has been observed, and upper limits on the production cross-section times branching ratio have been set for each model considered.
Conventional hadronic matter consists of baryons and mesons made of three quarks and quark-antiquark pairs, respectively. The observation of a new type of hadronic state, a doubly charmed tetraquark ...containing two charm quarks, an anti-\(u\) and an anti-\(d\) quark, is reported using data collected by the LHCb experiment at the Large Hadron Collider. This exotic state with a mass of about 3875 MeV\(/c^2\) manifests itself as a narrow peak in the mass spectrum of \(D^0D^0\pi^+\) mesons just below the \(D^{*+}D^0\) mass threshold. The near threshold mass together with a strikingly narrow width reveals the resonance nature of the state.
The differential cross-section of prompt inclusive production of long-lived charged particles in proton-proton collisions is measured using a data sample recorded by the LHCb experiment at a ...centre-of-mass energy of \({\sqrt{s} = 13\,\mathrm{TeV}}\). The data sample, collected with an unbiased trigger, corresponds to an integrated luminosity of \({5.4\,\mathrm{nb}^{-1}}\). The differential cross-section is measured as a function of transverse momentum and pseudorapidity in the ranges \({p_\mathrm{T} \in 0.08, 10)\,\mathrm{GeV}\,c^{-1}}\) and \({\eta \in 2.0, 4.8)}\) and is determined separately for positively and negatively charged particles. The results are compared with predictions from various hadronic-interaction models.
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