Excitation rates of heavy quarks

We obtain the production rates for c, b, and t quarks in deep-inelastic neutrino- (antineutrino-) nucleon interactions, in the standard six-quark model with left-handed couplings. The results are obtained with the most recent mixing parameters and we include a comparison between quark parametrizations. The excitations are calculated separately for each flavor, allowing the understanding of the role of threshold effects when considered through different rescaling variables.Facultad de Ciencias Exacta

The γγ→J/ψJ/ψ\gamma \gamma \to J/\psi J/\psi reaction and the J/ψJ/ψJ/\psi J/\psi pair production in exclusive ultraperipheral ultrarelativistic heavy ion collisions

We calculate the cross section for the $\gamma \gamma \to J/\psi J/\psi$ process. Two mechanisms are considered: box (two-loop) diagrams of the order of $O(\alpha_{em}^2 \alpha_s^2)$ and two-gluon exchange of the order of $O(\alpha_{em}^2 \alpha_s^4)$. The first mechanism is calculated in the heavy-quark non-relativistic approximation while the second case we also include the effects of quantum motion of quarks in the bound state. The box contribution dominates at energies close to the threshold ($W <$ 15 GeV) while the two-gluon mechanism takes over at $W >$ 15 GeV. Including the bound-state wave function effects for the two-gluon exchange mechanism gives a cross section 0.1 - 0.4 pb, substantially smaller than that in the non-relativistic limit (0.4 - 1.6 pb). We also find a strong infrared sensitivity which manifests itself in a rather strong dependence on the mass for the $t$-channel gluons. The elementary cross section is then used in the Equivalent Photon Approximation (EPA) in the impact parameter space to calculate the cross section for $^{208}Pb+^{208}Pb \to ^{208}Pb + J/\psi J/\psi + ^{208}Pb$ reaction. Distributions in rapidity of the $J/\psi J/\psi$ pair and invariant mass of the pair are shown.Comment: 15 pages, 11 figure

Channel-Coupling Effects in High-Energy Hadron Collisions

The Two-Gluon Model of the Pomeron predicts strongly size-dependent high-energy hadron cross sections. Yet experimental cross sections for radially excited mesons appear surprisingly close in value. The strong coupling of these mesons in hadron collisions also predicted by the model permits a qualitative understanding of this puzzling behavior in terms of eigenmode propagation with a common eigen-$\sigma$. A detailed semiempirical coupled-channel model of the Pomeron is constructed to elucidate this and other features of high-energy hadron cross sections.Comment: 13 pages, latex, no figure

Calibration of the photon spectrometer PHOS of the ALICE experiment

The procedure for the energy calibration of the high granularity electromagnetic calorimeter PHOS of the ALICE experiment is presented. The methods used to perform the relative gain calibration, to evaluate the geometrical alignment and the corresponding correction of the absolute energy scale, to obtain the nonlinearity correction coefficients and finally, to calculate the time-dependent calibration corrections, are discussed and illustrated by the PHOS performance in proton-proton (pp) collisions at s=13 TeV. After applying all corrections, the achieved mass resolutions for π0 and η mesons for pT &amp;gt; 1.7 GeV/c are σm π0 = 4.56 ± 0.03 MeV/c2 and σm η = 15.3 ± 1.0 MeV/c2, respectively. © 2019 CERN for the benefit of the Alice collaboration.

Erratum to: Insight into particle production mechanisms via angular correlations of identified particles in pp collisions at s = 7 TeV (The European Physical Journal C, (2017), 77, 8, (569), 10.1140/epjc/s10052-017-5129-6)

We have identified a mistake in how Fig. 1 is referenced in the text of the article Eur. Phys. J. C 77 (2017) no. 8, 569 which affected three paragraphs of the results section. The corrected three paragraphs as well as the unmodified accompanying figure are reproduced in this document with the correct labeling. In addition, an editing issue led to a missing acknowledgements section. The missing section is reproduced at the end of this document in the manner in which it should have appeared in the published article. © 2019, CERN for the benefit of the ALICE collaboration

Measurement of D-0, D+, D+* and D-s(+) production in pp collisions at root s=5.02 TeV with ALICE

The measurements of the production of prompt D , D + , D 17 + , and Ds+ mesons in proton\u2013proton (pp) collisions at s=5.02TeV with the ALICE detector at the Large Hadron Collider (LHC) are reported. D mesons were reconstructed at mid-rapidity (| y| &lt; 0.5) via their hadronic decay channels D \u2192 K - \u3c0 + , D + \u2192 K - \u3c0 + \u3c0 + , D 17 + \u2192 D \u3c0 + \u2192 K - \u3c0 + \u3c0 + , Ds+\u2192\u3d5\u3c0+\u2192K+K-\u3c0+, and their charge conjugates. The production cross sections were measured in the transverse momentum interval 0&lt;36GeV/c for D , 1&lt;36GeV/c for D + and D 17 + , and in 2&lt;24GeV/c for Ds+ mesons. Thanks to the higher integrated luminosity, an analysis in finer p T bins with respect to the previous measurements at s=7TeV was performed, allowing for a more detailed description of the cross-section p T shape. The measured p T -differential production cross sections are compared to the results at s=7&nbsp;TeV and to four different perturbative QCD calculations. Its rapidity dependence is also tested combining the ALICE and LHCb measurements in pp collisions at s=5.02TeV. This measurement will allow for a more accurate determination of the nuclear modification factor in p\u2013Pb and Pb\u2013Pb collisions performed at the same nucleon\u2013nucleon centre-of-mass energy

Calibration of the photon spectrometer PHOS of the ALICE experiment

The procedure for the energy calibration of the high granularity electromagnetic calorimeter PHOS of the ALICE experiment is presented. The methods used to perform the relative gain calibration, to evaluate the geometrical alignment and the corresponding correction of the absolute energy scale, to obtain the nonlinearity correction coefficients and finally, to calculate the time-dependent calibration corrections, are discussed and illustrated by the PHOS performance in proton-proton (pp) collisions at s=13 TeV. After applying all corrections, the achieved mass resolutions for \u3c00 and \u3b7 mesons for pT &gt; 1.7 GeV/c are \u3c3m\u3c0javax.xml.bind.JAXBElement@533d1c3d = 4.56 \ub1 0.03 MeV/c2 and \u3c3m\u3b7 = 15.3 \ub1 1.0 MeV/c2, respectively

Relative particle yield fluctuations in Pb-Pb collisions at root s(NN)=2.76 TeV

First results on K / \u3c0, p / \u3c0 and K/p fluctuations are obtained with the ALICE detector at the CERN LHC as a function of centrality in Pb--Pb collisions at 1asNN=2.76TeV. The observable \u3bd dyn , which is defined in terms of the moments of particle multiplicity distributions, is used to quantify the magnitude of dynamical fluctuations of relative particle yields and also provides insight into the correlation between particle pairs. This study is based on a novel experimental technique, called the Identity Method, which allows one to measure the moments of multiplicity distributions in case of incomplete particle identification. The results for p / \u3c0 show a change of sign in \u3bd dyn from positive to negative towards more peripheral collisions. For central collisions, the results follow the smooth trend of the data at lower energies and \u3bd dyn exhibits a change in sign for p / \u3c0 and K/p

Publisher Correction: Unveiling the strong interaction among hadrons at the LHC (Nature, (2020), 588, 7837, (232-238), 10.1038/s41586-020-3001-6)

In Fig. 1c of this Article, owing to an error during the production process, the equation incorrectly began ‘C(k*, r*) = …’ instead of ‘C(k*) = …’. In addition, in affiliation 71 ‘Dipartimento di Fisica dell’Università degli studi di Bari Aldo Moro’ has been corrected to read ‘Dipartimento di Fisica dell’Università degli studi di Cagliari’. The original Article has been corrected online. *A list of authors and their affiliations appears online. © 2021, The Author(s), under exclusive licence to Springer Nature Limited

Energy dependence of exclusive J/ photoproduction off protons in ultra-peripheral p-Pb collisions at NN=5.02 TeV

The ALICE Collaboration has measured the energy dependence of exclusive photoproduction of J / \u3c8 vector mesons off proton targets in ultra\u2013peripheral p\u2013Pb collisions at a centre-of-mass energy per nucleon pair sNN=5.02 TeV. The e + e - and \u3bc + \u3bc - decay channels are used to measure the cross section as a function of the rapidity of the J / \u3c8 in the range - 2.5 &lt; y&lt; 2.7 , corresponding to an energy in the \u3b3p centre-of-mass in the interval 40 &lt; W \u3b3p &lt; 550 GeV. The measurements, which are consistent with a power law dependence of the exclusive J / \u3c8 photoproduction cross section, are compared to previous results from HERA and the LHC and to several theoretical models. They are found to be compatible with previous measurements