Summary of determinations of αs from hadronic τ -decays (a), from lattice calculations (b), from DIS structure functions (c) and from e + e − annihilation (d). The shaded bands indicate the pre-average values explained in the text, to be included in the determination of the nal world average of αs. In a), full circles are results obtained using CIPT, and open circles using FOPT expansions, see text.  

Summary of determinations of αs from hadronic τ -decays (a), from lattice calculations (b), from DIS structure functions (c) and from e + e − annihilation (d). The shaded bands indicate the pre-average values explained in the text, to be included in the determination of the nal world average of αs. In a), full circles are results obtained using CIPT, and open circles using FOPT expansions, see text.  

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This is a preliminary update of the measurements of αs and the determination of the world average value of αs (M2Z) presented in the 2013/2014 edition of the Review of Particle Properties [1].

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... The results are shown in Fig. 8. The one-loop perturbative expression (32), evaluated at α ¼ 0.3 ≈ α MS ð2 GeVÞ [61,62] and m q ¼ 17 MeV and with μ ¼ 2 GeV, is also plotted. We have used the subtracted bare quark mass rather than the renormalized mass in this calculation, but this makes little difference as varying m q even by a factor 2 has a negligible effect for the range of momenta we are considering here. ...
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Thesis
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... In the GE potential we use the vector coupling constant, which does not contain fitting parameters and takes into account the asymptotic freedom behavior [33], so that the effective coupling of the ground state α V (eff.) = 0.39 is relatively small, while α V = 0.54 is larger for excited states with n r ≥ 2. Details can be found in Ref. [22], where the vector coupling α v (n f = 3) is shown to be defined via the QCD vector constant Λ V (n f = 3) = 0.455 GeV, which corresponds to the QCD constant Λ M S (n f = 3) = 330 MeV from Ref. [34]. ...
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... For the CKM matrix we assume the unit matrix, which for the most relevant element of our computation V tb is consistent with the measured value (1.021 ± 0.032 [102]). Furthermore, we set the initial value for the strong (running) coupling constant to [103] α s µ = m Z = 0.118 , (3.14) ...
Article
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... This asymmetry causes, via multiple collisions, an anisotropic momentum distribution as shown in Figure 1. 6. ...
... This model [44] also factorizes the charmonium production cross section into perturbative and non-perturbative steps, but unlike the CSM, it does not assume that the charm quarks are produced in their final color state. The J/ψ production cross section under this model is given by [45]: This model has been successful in describing many charmonium observables including the J/ψ production cross sections at different LHC energies measured by ALICE as will be discussed in section 2. 6 ...
... As Figure 4.7: Invariant mass distributions of opposite-charge muon pairs from semileptonic decay of bb pairs at s NN = 5.02 TeV using PYTHIA. 6. The different distributions correspond to the applying of different kinematic cuts. ...
Thesis
Ultra relativistic heavy-ion collisions are considered as a unique tool to produce, in the laboratory, thehot and dense strongly-interacting medium, the Quark-Gluon Plasma (QGP). This thesis is dedicated to the studyof two powerful probes, the J/ψ and Z-boson, that can help reaching a better understanding of the properties of theQGP.An important observable to study the QGP formation in heavy-ion collisions is the measurement of the J/ψproduction. The sizes of the different effects that can enhance or suppress this production vary with the collisionenergy. In this thesis, the J/ψ production is measured in Pb-Pb collisions at √sNN = 5.02 TeV using mainly themuon spectrometer of the ALICE detector. The J/ψ nuclear modification factor is presented as a function ofcollision centrality, rapidity and transverse momentum (pT). In addition, results on the J/ψ average pT and squaredaverage pT are also obtained. The comparison between the results and various theoretical calculations suggests thatthe J/ψ production is affected in the medium by an interplay between dissociation and regeneration mechanisms.In heavy-ion collisions, the initial state of the collision can affect the results even in the absence of the QGP.Understanding and quantifying such effects is crucial in order to separate them from the ones caused by thepresence of the QGP. One of these effects is the nuclear modification of the parton distribution functions (PDFs).The measurement of Z-boson production in heavy-ion collisions is a powerful tool to study the nuclearmodification of PDFs since it is not affected by the presence of the strongly-interacting medium. The second partof this thesis is devoted to measure the Z-boson production, for the first time with ALICE, in p-Pb and Pb-Pbcollisions at √sNN = 5.02 TeV. In Pb-Pb collisions where the precision of the measurement is higher, the agreementbetween data and theoretical calculations is better when the latter take into account the nuclear modification of thePDFs.
... For the experimental values M t ≈ 173.34 ± 0.76 GeV [65], M H ≈ 125.09 ± 0.24 GeV[66] and α s (M Z ) = 0.1184 ± 0.0007 [67] we get the couplings in the MS-scheme at the scale of the top mass using two-loop matching relations [15] ...
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... Furthermore, there are other precise determinations with lower central values and in disagreement with the world average from event-shapes64656667 and DIS [68]. A review on recent α s determinations can be found in Refs.697071 . Therefore , in analogy with Ref. [6], we perform our analyses for several values of α s (m Z ) between 0.113 and 0.119, and provide the central values and perturbative errors as (approximate) linear functions of α s (m Z ). ...
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We present new determinations of the \( \overline{\mathrm{MS}} \) charm quark mass using relativistic QCD sum rules at \( \mathcal{O}\left({\alpha}_s^3\right) \) from the moments of the vector and the pseudoscalar current correlators. We use available experimental measurements from e +e − collisions and lattice simulation results, respectively. Our analysis of the theoretical uncertainties is based on different implementations of the perturbative series and on independent variations of the renormalization scales for the mass and the strong coupling. Taking into account the resulting set of series to estimate perturbative uncertainties is crucial, since some ways to treat the perturbative expansion can exhibit extraordinarily small scale dependence when the two scales are set equal. As an additional refinement, we address the issue that double scale variation could overestimate the perturbative uncertainties. We supplement the analysis with a test that quantifies the convergence rate of each perturbative series by a single number. We find that this convergence test allows to determine an overall and average convergence rate that is characteristic for the series expansions of each moment, and to discard those series for which the convergence rate is significantly worse. We obtain \( \overline{m_c}\left(\overline{m_c}\right)=1.288\pm 0.020 \) GeV from the vector correlator. The method is also applied to the extraction of the \( \overline{\mathrm{MS}} \) bottom quark mass from the vector correlator. We compute the experimental moments including a modeling uncertainty associated to the continuum region where no data is available. We obtain \( \overline{m_b}\left(\overline{m_b}\right)=4.176\pm 0.023 \) GeV.
... Whether this fact is due to missing higher-order contributions in our calculations or to other effects is not yet clear at this point. Apart from the kurtosis, the QCD coupling value extracted from all the other moments has values around α s (m 2 Z ) = 0.118, in striking agreement with the current world-average obtained by other methods [57, 58]. ) at NLO (MS scheme, n f = 5 quark flavours) obtained from the fits of the √ s-dependence of the moments of the charged hadron distribution of jets in e + e − collisions obtained from their NMLLA+NLO * evolution. The last column provides the weighted-average of the individual measurements with its total propagated uncertainty. ...
... ) uncertainties have been enlarged by a common factor such that their final weighted average has a χ 2 /ndf close to unity. Such a " χ 2 averaging " method [58] ) = 0.1195 ± 0.0022 which is in excellent agreement with the current world-average of the strong coupling at the Z mass [57, 58]. Our extraction of the QCD strong coupling has an uncertainty (±2%) that is commensurate with that from other e + e − observables such as jet-shapes (±1%) and 3-jets rates (±2%) [57, 58]. ...
... Such a " χ 2 averaging " method [58] ) = 0.1195 ± 0.0022 which is in excellent agreement with the current world-average of the strong coupling at the Z mass [57, 58]. Our extraction of the QCD strong coupling has an uncertainty (±2%) that is commensurate with that from other e + e − observables such as jet-shapes (±1%) and 3-jets rates (±2%) [57, 58]. In a forthcoming work, we will extend the extraction of the strong coupling via the NMLLA+NLO * evolution of the moments of the hadron distribution in jet world-data measured not only in e + e − but also including deep-inelastic e ± p collisions [59]. ...
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The moments of the single inclusive momentum distribution of hadrons in QCD jets, are studied in the next-to-modified-leading-log approximation (NMLLA) including next-to-leading-order (NLO) corrections to the αs strong coupling. The evolution equations are solved using a distorted Gaussian parametrisation, which successfully reproduces the spectrum of charged hadrons of jets measured in e + e − collisions. The energy dependencies of the maximum peak, multiplicity, width, kurtosis and skewness of the jet hadron distribution are computed analytically. Comparisons of all the existing jet data measured in e + e − collisions in the range \( \sqrt{\mathrm{s}}\approx 2-200 \) GeV to the NMLLA + NLO* predictions allow one to extract a value of the QCD parameter ΛQCD , and associated two-loop coupling constant at the Z resonance α s(m Z 2 ) = 0.1195 ± 0.0022, in excellent numerical agreement with the current world average obtained using other methods.
... The recent measurements of m h by the ATLAS [12] and CMS [14] According to ref. [29, 30], the world average of α s (M 2 Z ) from the fit to various data, excluding the EW precision measurements, is given by α s (M 2 Z ) = 0.1184 ± 0.0006. For the hadronic contribution to the running of the electromagnetic coupling, we adopt the recent evaluation ∆α ...
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We perform the fit of electroweak precision observables within the Standard Model with a 126 GeV Higgs boson, compare the results with the theoretical predictions and discuss the impact of recent experimental and theoretical improvements. We introduce New Physics contributions in a model-independent way and fit for the S, T and U parameters, for the $\epsilon_{1,2,3,b}$ ones, for modified $Zb\bar{b}$ couplings and for a modified Higgs coupling to vector bosons. We point out that composite Higgs models are very strongly constrained. Finally, we compute the bounds on dimension-six operators relevant for the electroweak fit.