15 research outputs found
Prompt and non-prompt J/ψ production cross sections at midrapidity in proton-proton collisions at s = 5.02 and 13 TeV
No full textThe production of J/ψ is measured at midrapidity (|y| < 0.9) in proton-proton collisions at 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 Lint = 19.4 ± 0.4 nb−1 and Lint = 32.2 ± 0.5 nb−1 at 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 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 bb¯ pair cross section at midrapidity and in the total phase space. The total bb¯ cross sections are found to be σbb¯ = 541 ± 45 (stat.) ± 69 syst.−12+10 (extr.) μb and σbb¯ = 218±37 (stat.)±31 syst.−9.1+8.2 (extr.) μb at s = 13 and 5.02 TeV, respectively. The value obtained from the combination of ALICE and LHCb measurements in pp collisions at s = 13 TeV is also provided
Prompt and non-prompt J/psi production and nuclear modification at mid-rapidity in p-Pb collisions at root s(NN)=5.02 TeV
No full textA measurement of beauty hadron production at mid-rapidity in proton-lead collisions at a nucleon-nucleon centre-of-mass energy root s(NN) = 5.02 TeV is presented. The semi-inclusive decay channel of beauty hadrons into J/psi is considered, where the J/psi mesons are reconstructed in the dielectron decay channel at mid-rapidity down to transverse momenta of 1.3 GeV/c. The bb production cross section at mid-rapidity, d sigma(bb)/dy, and the total cross section extrapolated over full phase space, sigma(bb), are obtained. This measurement is combined with results on inclusive J/psi production to determine the prompt J/psi cross sections. The results in p-Pb collisions are then scaled to expectations from pp collisions at the same centre-of-mass energy to derive the nuclear modification factor R-pPb, and compared to models to study possible nuclear modifications of the production induced by cold nuclear matter effects. RpPb is found to be smaller than unity at low pT for both J/psi coming from beauty hadron decays and prompt J/psi
Study of flavor dependence of the baryon-to-meson ratio in proton-proton collisions at s=13 TeV
No full textThe production cross sections of D0 and Λc+ hadrons originating from beauty-hadron decays (i.e., nonprompt) were measured for the first time at midrapidity (|y|<0.5) by the ALICE Collaboration in proton-proton collisions at a center-of-mass energy s=13 TeV. They are described within uncertainties by perturbative QCD calculations employing the fragmentation fractions of beauty quarks to baryons measured at forward rapidity by the LHCb Collaboration. The bb¯ production cross section per unit of rapidity at midrapidity, estimated from these measurements, is dσbb¯/dy||y|<0.5=83.1±3.5(stat)±5.4(syst)-3.2+12.3(extrap) μb. The baryon-to-meson ratios are computed to investigate the hadronization mechanism of beauty quarks. The nonprompt Λc+/D0 production ratio has a similar trend to the one measured for the promptly produced charmed particles and to the p/π+ and Λ/KS0 ratios, suggesting a similar baryon-formation mechanism among light, strange, charm, and beauty hadrons. The pT -integrated nonprompt Λc+/D0 ratio is found to be significantly higher than the one measured in e+e- collisions
Measurement of beauty-quark production in pp collisions at s = 13 TeV via non-prompt D mesons
No full textThe pT-differential production cross sections of non-prompt D0, D+, and Ds+ mesons originating from beauty-hadron decays are measured in proton–proton collisions at a centre-of-mass energy s = 13 TeV. The measurements are performed at midrapidity, |y| < 0.5, with the data sample collected by ALICE from 2016 to 2018. The results are in agreement with predictions from several perturbative QCD calculations. The fragmentation fraction of beauty quarks to strange mesons divided by the one to non-strange mesons, fs/(fu + fd), is found to be 0.114 ± 0.016 (stat.) ± 0.006 (syst.) ± 0.003 (BR) ± 0.003 (extrap.). This value is compatible with previous measurements at lower centre-of-mass energies and in different collision systems in agreement with the assumption of universality of fragmentation functions. In addition, the dependence of the non-prompt D meson production on the centre-of-mass energy is investigated by comparing the results obtained at s = 5.02 and 13 TeV, showing a hardening of the non-prompt D-meson pT-differential production cross section at higher s. Finally, the bb ̄ production cross section per unit of rapidity at midrapidity is calculated from the non-prompt D0, D+, Ds+, and Λc+ hadron measurements, obtaining dσ/dy=75.2±3.2stat.±5.2syst.−3.2+12.3extrap. μb
Measurement of beauty and charm production in pp collisions at √s = 5.02 TeV via non-prompt and prompt D mesons
No full textThe pT-differential production cross sections of prompt and non-prompt (produced in beauty-hadron decays) D mesons were measured by the ALICE experiment at midrapidity (|y| < 0.5) in proton-proton collisions at √s = 5.02 TeV. The data sample used in the analysis corresponds to an integrated luminosity of (19.3 ± 0.4) nb⁻¹. D mesons were reconstructed from their decays D⁰ → K‾ π⁺, D⁺ → K‾π⁺π⁺, and D⁺ₛ → ϕπ⁺ → K‾K⁺π⁺ and their charge conjugates. Compared to previous measurements in the same rapidity region, the cross sections of prompt D⁺ and D⁺ₛ mesons have an extended p T coverage and total uncertainties reduced by a factor ranging from 1.05 to 1.6, depending on pT, allowing for a more precise determination of their pT-integrated cross sections. The results are well described by perturbative QCD calculations. The fragmentation fraction of heavy quarks to strange mesons divided by the one to non-strange mesons, fₛ/ (fᵤ + fd), is compatible for charm and beauty quarks and with previous measurements at different centre-of-mass energies and collision systems. The bb‾ production cross section per rapidity unit at midrapidity, estimated from non-prompt D-meson measurements, is dσ bb¯ / dy| |y| < 0.5 = 34.5 ± 2.4(stat)⁺⁴.⁷₋₂.₉ (tot. syst) μb. It is compatible with previous measurements at the same centre-of-mass energy and with the cross section pre- dicted by perturbative QCD calculations
Dielectron production in proton-proton collisions at root s=7 TeV
No full textCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFINEP - FINANCIADORA DE ESTUDOS E PROJETOSFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOThe first measurement of e(+)e(-) pair production at mid-rapidity (vertical bar eta vertical bar(e) < 0.8) in pp collisions at root s = 7TeV with ALICE at the LHC is presented. The dielectron production is studied as a function of the invariant mass (m(ee )< 3.3 GeV/c(2)), the pair transverse momentum (p(T,ee) < 8 GeV/c), and the pair transverse impact parameter (DCA(ee)), i.e., the average distance of closest approach of the reconstructed electron and positron tracks to the collision vertex, normalised to its resolution. The results are compared with the expectations from a cocktail of known hadronic sources and are well described when PYTHIA is used to generate the heavy-flavour contributions. In the low-mass region (0.14 < m(ee) < 1.1 GeV/c(2)), prompt and non-prompt e(+)e(-) sources can be separated via the DCA(ee). In the intermediate-mass region (1.1 < m(ee) < 2.7 GeV/c(2)), a double-differential fit to the data in m(ee) and p(T,ee) and a fit of the DCA(ee) distribution allow the total cc and bb cross sections to be extracted. Two different event generators, PYTHIA and POWHEG, can reproduce the shape of the two-dimensional m(ee) and p(T,ee) spectra, as well as the shape , of the DCA(ee) distribution, reasonably well. However, differences in the c (c) over bar and b (b) over bar cross sections are observed when using the generators to extrapolate to full phase space. Finally, the ratio of inclusive to decay photons is studied via the measurement of virtual direct photons in the transverse-momentum range 1 < p(T) < 8 GeV/c. This is found to be unity within the statistical and systematic uncertainties and consistent with expectations from next-to-leading order perturbative quantum chromodynamic calculations.9147CNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFINEP - FINANCIADORA DE ESTUDOS E PROJETOSFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFINEP - FINANCIADORA DE ESTUDOS E PROJETOSFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOSem informaçãoSem informaçãoSem informaçãoAgências de fomento estrangeiras apoiaram essa pesquisa, mais informações acesse artig
Measurement of beauty and charm production in pp collisions at <mml:msqrt>s</mml:msqrt>=5.02 TeV via non-prompt and prompt D mesons
No full textThe p(T)-differential production cross sections of prompt and non-prompt (produced in beauty-hadron decays) D mesons were measured by the ALICE experiment at midrapidity (|y|< 0.5) in proton-proton collisions at <mml:msqrt>s</mml:msqrt> = 5.02 TeV. The data sample used in the analysis corresponds to an integrated luminosity of (19.3 0.4) nb(-1). D mesons were reconstructed from their decays D-0 -> K-pi (+), D+-> K-pi (+)pi (+), and Ds+</mml:msubsup>-> phi pi+-> K-K+pi+ and their charge conjugates. Compared to previous measurements in the same rapidity region, the cross sections of prompt D+ and Ds+</mml:msubsup> mesons have an extended p(T) coverage and total uncertainties reduced by a factor ranging from 1.05 to 1.6, depending on p(T), allowing for a more precise determination of their p(T)-integrated cross sections. The results are well described by perturbative QCD calculations. The fragmentation fraction of heavy quarks to strange mesons divided by the one to non-strange mesons, f(s)/(f(u) + f(d)), is compatible for charm and beauty quarks and with previous measurements at different centre-of-mass energies and collision systems. The bb<overbar></mml:mover> production cross section per rapidity unit at midrapidity, estimated from non-prompt D-meson measurements, is d<mml:msub>sigma bb<overbar></mml:mover>/dy<mml:mfenced open=”|”><mml:msub><mml:mfenced close=”|” open=”|”>y</mml:mfenced><0.5=34.5<plus/minus>2.4<mml:mfenced close=”)” open=”(”>stat</mml:mfenced>-2.9<mml:mo>+4.7<mml:mfenced close=”)” open=”(”>tot<mml:mo>.syst</mml:mfenced></mml:mfenced> mu b. It is compatible with previous measurements at the same centre-of-mass energy and with the cross section pre- dicted by perturbative QCD calculations.<fig id=”Figa” position=”anchor”><graphic position=”anchor” specific-use=”HTML” mime-subtype=”JPEG” xmlns:xlink=”http://www.w3.org/1999/xlink” xlink:href=”MediaObjects/13130_2021_15783_Figa_HTML.jpg” id=”MO1”></graphi
Beauty production in pp collisions at √s=2.76 TeV measured via semi-electronic decays
No full textThe ALICE collaboration at the LHC reports measurement of the inclusive production cross section of electrons from semi-leptonic decays of beauty hadrons with rapidity |y|&lt;0.8 and transverse momentum 1&lt;pT&lt;10 GeV/c, in pp collisions at s=2.76 TeV. Electrons not originating from semi-electronic decay of beauty hadrons are suppressed using the impact parameter of the corresponding tracks. The production cross section of beauty decay electrons is compared to the result obtained with an alternative method which uses the distribution of the azimuthal angle between heavy-flavour decay electrons and charged hadrons. Perturbative QCD predictions agree with the measured cross section within the experimental and theoretical uncertainties. The integrated visible cross section, σb→e=3.47±0.40(stat)−1.33 +1.12(sys)±0.07(norm) μb, was extrapolated to full phase space using Fixed Order plus Next-to-Leading Log (FONLL) calculations to obtain the total bb¯ production cross section, σbb¯=130±15.1(stat)−49.8 +42.1(sys)−3.1 +3.4(extr)±2.5(norm)±4.4(BR) μb. © 201
Production of charged pions, kaons and protons at large transverse momenta in pp and Pb–Pb collisions at TeV
No full textTransverse momentum spectra of pi(+/-), K-+/- and p((p) over bar) up to p(T) = 20 GeV/c at mid-rapidity in pp, peripheral (60-80%) and central (0-5%) Pb-Pb collisions at v root s(NN) = 2.76 TeV have been measured using the ALICE detector at the Large Hadron Collider. The proton-to-pion and the kaon-to-pionratios both show a distinct peak at p(T) approximate to 3 GeV/c in central Pb-Pb collisions. Below the peak, p(T) 10 GeV/c particle ratios in pp and Pb-Pb collisions are in agreement and the nuclear modification factors for pi(+/-), K-+/- and p((p) over bar) indicate that, within the systematic and statistical uncertainties, the suppression is the same. This suggests that the chemical composition of leading particles from jets in the medium is similar to that of vacuum jets
Study of flavor dependence of the baryon-to-meson ratio in proton–proton collisions at √s= 13 TeV
No full textThe production cross sections of D0 and Λ+c hadrons originating from beauty-hadron decays (i.e. non-prompt) were measured for the first time at midrapidity (|y|<0.5) by the ALICE Collaboration in proton-proton collisions at a center-of-mass energy s√=13 TeV. They are described within uncertainties by perturbative QCD calculations employing the fragmentation fractions of beauty quarks to baryons measured at forward rapidity by the LHCb Collaboration. The bb¯¯¯ production cross section per unit of rapidity at midrapidity, estimated from these measurements, is dσbb¯¯¯/dy||y|<0.5=83.1±3.5(stat.)±5.4(syst.)+12.3−3.2(extrap.)μb. The baryon-to-meson ratios are computed to investigate the hadronization mechanism of beauty quarks. The non-prompt Λ+c/D0 production ratio has a similar trend to the one measured for the promptly produced charmed particles and to the p/π+ and Λ/K0S ratios, suggesting a similar baryon-formation mechanism among light, strange, charm, and beauty hadrons. The pT-integrated non-prompt Λc/D0 ratio is found to be significantly higher than the one measured in e+e− collisions
