87,525 research outputs found
Comment on "multiconfiguration Dirac-Fock energy levels and radiative rates for Br-like tungsten" by S. Aggarwal, A.K.S. Jha, and M. Mohan [Can. J. Phys. 91, 394 (2013)]
No full textWe report calculations of energy levels and oscillator strengths for transitions in W XL, undertaken with the general-purpose relativistic atomic structure package (GRASP) and flexible atomic code (FAC). Comparisons are made with existing results and the accuracy of the data is assessed. Discrepancies with the most recent results of S. Aggarwal et al. (Can. J. Phys. 91, 394 (2013)) are up to 0.4 Ryd and up to two orders of magnitude for energy levels and oscillator strengths, respectively. Discrepancies for lifetimes are even larger, up to four orders of magnitude for some levels. Our energy levels are estimated to be accurate to better than 0.5% (i.e., 0.2 Ryd), whereas results for oscillator strengths and lifetimes should be accurate to better than 20%.</p
Multiplicity dependence of π , K, and p production in pp collisions at √s=13 TeV
No full textThis paper presents the measurements of π±, K ±, p and p ̄ transverse momentum (pT) spectra as a function of charged-particle multiplicity density in proton–proton (pp) collisions at s=13TeV with the ALICE detector at the LHC. Such study allows us to isolate the center-of-mass energy dependence of light-flavour particle production. The measurements reported here cover a pT range from 0.1 to 20 GeV / c and are done in the rapidity interval | y| < 0.5. The pT-differential particle ratios exhibit an evolution with multiplicity, similar to that observed in pp collisions at s=7TeV, which is qualitatively described by some of the hydrodynamical and pQCD-inspired models discussed in this paper. Furthermore, the pT-integrated hadron-to-pion yield ratios measured in pp collisions at two different center-of-mass energies are consistent when compared at similar multiplicities. This also extends to strange and multi-strange hadrons, suggesting that, at LHC energies, particle hadrochemistry scales with particle multiplicity the same way under different collision energies and colliding systems
One-dimensional charged kaon femtoscopy in p-Pb collisions at s NN = 5.02 TeV
No full textThe correlations of identical charged kaons were measured in p-Pb collisions at sNN=5.02 TeV by the ALICE experiment at the LHC. The femtoscopic invariant radii and correlation strengths were extracted from one-dimensional kaon correlation functions and were compared with those obtained in pp and Pb-Pb collisions at s=7 TeV and sNN=2.76 TeV, respectively. The presented results also complement the identical-pion femtoscopic data published by the ALICE collaboration. The extracted radii increase with increasing charged-particle multiplicity and decrease with increasing pair transverse momentum. At comparable multiplicities, the radii measured in p-Pb collisions are found to be close to those observed in pp collisions. The obtained femtoscopic parameters are reproduced by the EPOS 3 hadronic interaction model and disfavor models with large initial size or strong collective expansion at low multiplicities
Production of (anti-)He-3 and (anti-)H-3 in p-Pb collisions at root s(NN)=5.02 TeV
No full textThe transverse momentum (p(T)) differential yields of (anti-)He-3 and (anti-)H-3 measured in p-Pb collisions at root s(NN) = 5.02 TeV with ALICE at the Large Hadron Collider (LHC) are presented. The ratios of the p(T)-integrated yields of (anti-)He-3 and (anti-)H-3 to the proton yields are reported, as well as the pT dependence of the coalescence parameters B-3 for (anti-)He-3 and (anti-)H-3. For (anti-)He-3, the results obtained in four classes of the mean charged-particle multiplicity density are also discussed. These results are compared to predictions from a canonical statistical hadronization model and coalescence approaches. An upper limit on the total yield of (4)(He) over bar is determined
Measurement of Λ (1520) production in pp collisions at √s=7TeV and p–Pb collisions at √sNN=5.02TeV
No full textThe production of the Λ (1520) baryonic resonance has been measured at midrapidity in inelastic pp collisions at s=7TeV and in p–Pb collisions at sNN=5.02TeV for non-single diffractive events and in multiplicity classes. The resonance is reconstructed through its hadronic decay channel Λ (1520) → pK - and the charge conjugate with the ALICE detector. The integrated yields and mean transverse momenta are calculated from the measured transverse momentum distributions in pp and p–Pb collisions. The mean transverse momenta follow mass ordering as previously observed for other hyperons in the same collision systems. A Blast-Wave function constrained by other light hadrons (π, K, KS0, p, Λ) describes the shape of the Λ (1520) transverse momentum distribution up to 3.5GeV/c in p–Pb collisions. In the framework of this model, this observation suggests that the Λ (1520) resonance participates in the same collective radial flow as other light hadrons. The ratio of the yield of Λ (1520) to the yield of the ground state particle Λ remains constant as a function of charged-particle multiplicity, suggesting that there is no net effect of the hadronic phase in p–Pb collisions on the Λ (1520) yield
Production of light-flavor hadrons in pp collisions at √s=7and√s=13TeV
No full textThe production of π±, K ±, KS0, K ∗(892) , p , φ(1020) , Λ , Ξ -, Ω -, and their antiparticles was measured in inelastic proton–proton (pp) collisions at a center-of-mass energy of s = 13 TeV at midrapidity (| y| < 0.5) as a function of transverse momentum (pT) using the ALICE detector at the CERN LHC. Furthermore, the single-particle pT distributions of KS0, Λ , and Λ ̄ in inelastic pp collisions at s=7 TeV are reported here for the first time. The pT distributions are studied at midrapidity within the transverse momentum range 0 ≤ pT≤ 20 GeV/c, depending on the particle species. The pT spectra, integrated yields, and particle yield ratios are discussed as a function of collision energy and compared with measurements at lower s and with results from various general-purpose QCD-inspired Monte Carlo models. A hardening of the spectra at high pT with increasing collision energy is observed, which is similar for all particle species under study. The transverse mass and xT≡2pT/s scaling properties of hadron production are also studied. As the collision energy increases from s = 7–13 TeV, the yields of non- and single-strange hadrons normalized to the pion yields remain approximately constant as a function of s, while ratios for multi-strange hadrons indicate enhancements. The pT-differential cross sections of π±, K ± and p (p ̄) are compared with next-to-leading order perturbative QCD calculations, which are found to overestimate the cross sections for π± and p (p ̄) at high pT
Measurement of D-0, D+, D+* and D-s(+) production in pp collisions at root s=5.02 TeV with ALICE
No full textThe measurements of the production of prompt D0, D+, D+, and Ds+ mesons in proton-proton (pp) collisions at TeV with the ALICE detector at the Large Hadron Collider (LHC) are reported. D mesons were reconstructed at mid-rapidity (|y|<0.5) via their hadronic decay channels D0K-+, D+K-++, D+D0+K-++, Ds+phi+K+K-+, and their charge conjugates. The production cross sections were measured in the transverse momentum interval 0<36 for D0, 1<36 for D+ and D+, and in 2<24 for Ds+ mesons. Thanks to the higher integrated luminosity, an analysis in finer pT bins with respect to the previous measurements at sTeV was performed, allowing for a more detailed description of the cross-section pT shape. The measured pT-differential production cross sections are compared to the results at s=7TeV and to four different perturbative QCD calculations. Its rapidity dependence is also tested combining the ALICE and LHCb measurements in pp collisions at s=5.02 TeV. This measurement will allow for a more accurate determination of the nuclear modification factor in p-Pb and Pb-Pb collisions performed at the same nucleon-nucleon centre-of-mass energy
p-p, p-Lambda, and Lambda-Lambda correlations studied via femtoscopy in pp reactions at root s=7 TeV
No full textWe report on the first femtoscopic measurement of baryon pairs, such as p-p, p-Lambda, and Lambda-Lambda, measured by ALICE at the Large Hadron Collider (LHC) in proton-proton collisions at root s = 7 TeV. This study demonstrates the feasibility of such measurements in pp collisions at ultrarelativistic energies. The femtoscopy method is employed to constrain the hyperon-nucleon and hyperon-hyperon interactions, which are still rather poorly understood. A new method to evaluate the influence of residual correlations induced by the decays of resonances and experimental impurities is hereby presented. The p-p, p-Lambda, and Lambda-Lambda correlation functions were fitted simultaneously with the help of a new tool developed specifically for the femtoscopy analysis in small colliding systems: Correlation Analysis Tool using the Schrodinger equation (CATS). Within the assumption that in pp collisions the three particle pairs originate from a common source, its radius is found to be equal to r(0) = 1.125 +/- 0.018 (stat)(-0.035)(+0.058) (syst) fm. The sensitivity of the measured p-Lambda correlation is tested against different scattering parameters, which are defined by the interaction among the two particles, but the statistics is not sufficient yet to discriminate among different models. The measurement of the Lambda-Lambda correlation function constrains the phase space spanned by the effective range and scattering length of the strong interaction. Discrepancies between the measured scattering parameters and the resulting correlation functions at LHC and RHIC energies are discussed in the context of various models
K*(892)(0) and phi(1020) production at midrapidity in pp collisions at root s=8 TeV
No full textThe production of K* (892)(0) and phi(1020) in pp collisions at root s = 8 TeV was measured by using Run 1 data collected by the ALICE collaboration at the CERN Large Hadron Collider (LHC). The P-T-differential yields d(2)N/dydp(T), in the range 0 < p(T) < 20 GeV/c for K*(0) and 0.4 < p(T) < 16 GeV/c for phi have been measured at midrapidity, vertical bar y vertical bar < 0.5. Moreover, improved measurements of the K*(0)(892) and phi (1020) at root s = 7 TeV are presented. The collision energy dependence of p(T) distributions, p(T)-integrated yields, and particle ratios in inelastic pp collisions are examined. The results are also compared with different collision systems. The values of the particle ratios are found to be similar to those measured at other LHC energies. In pp collisions a hardening of the particle spectra is observed with increasing energy, but at the same time it is also observed that the relative particle abundances are independent of the collision energy. The P-T-differential yields of K*(0) and phi in pp collisions at root s = 8 TeV are compared with the expectations of different Monte Carlo event generators
Production of light (anti)nuclei in pp collisions at √s = 5.02 TeV
No full textThe study of the production of nuclei and antinuclei in pp collisions has proven to be a powerful tool to investigate the formation mechanism of loosely bound states in high-energy hadronic collisions. In this paper, the production of protons, deuterons and He-3 and their charge conjugates at midrapidity is studied as a function of the charged-particle multiplicity in inelastic pp collisions at root s = 5.02 TeV using the ALICE detector. Within the uncertainties, the yields of nuclei in pp collisions at root s = 5.02 TeV are compatible with those in pp collisions at different energies and to those in p-Pb collisions when compared at similar multiplicities. The measurements are compared with the expectations of coalescence and Statistical Hadronisation Models. The results suggest a common formation mechanism behind the production of light nuclei in hadronic interactions and confirm that they do not depend on the collision energy but on the number of produced particles
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