Long-range Angular Correlations On The Near And Away Side In P-pb Collisions At √snn=5.02 Tev

7191/Mar294

Multiplicity dependence of inclusive J/psi production at midrapidity in pp collisions at root s=13 TeV

Measurements of the inclusive J/psi yield as a function of charged-particle pseudorapidity density dN(ch)/d eta in pp collisions at root s = 13 TeV with ALICE at the LHC are reported. The J/psi meson yield is measured at midrapidity (vertical bar y vertical bar <0.9) in the dielectron channel, for events selected based on the charged-particle multiplicity at midrapidity (vertical bar eta vertical bar <1) and at forward rapidity (-3.7 <eta <-1.7 and 2.8 <eta <5.1); both observables are normalized to their corresponding averages in minimum bias events. The increase of the normalized J/psi yield with normalized dN(ch)/d eta is significantly stronger than linear and dependent on the transverse momentum. The data are compared to theoretical predictions, which describe the observed trends well, albeit not always quantitatively. (C) 2020 European Organization for Nuclear Research. Published by Elsevier B.V.Peer reviewe

First measurement of Ωc0 production in pp collisions at s=13 TeV

The inclusive production of the charm–strange baryon 0 c is measured for the first time via its hadronic √ decay into −π+ at midrapidity (|y| &lt;0.5) in proton–proton (pp) collisions at the centre-of-mass energy s =13 TeV with the ALICE detector at the LHC. The transverse momentum (pT) differential cross section multiplied by the branching ratio is presented in the interval 2 &lt; pT &lt; 12 GeV/c. The pT dependence of the 0 c-baryon production relative to the prompt D0-meson and to the prompt 0 c-baryon production is compared to various models that take different hadronisation mechanisms into consideration. In the measured pT interval, the ratio of the pT-integrated cross sections of 0 c and prompt + c baryons multiplied by the −π+ branching ratio is found to be larger by a factor of about 20 with a significance of about 4σ when compared to e+e− collisions

Elliptic flow of charged particles at midrapidity relative to the spectator plane in Pb–Pb and Xe–Xe collisions

Measurements of the elliptic flow coefficient relative to the collision plane defined by the spectator neutrons v2{ SP} in collisions of Pb ions at center-of-mass energy per nucleon–nucleon pair √ 2.76 TeV and Xe ions at √ sNN = sNN =5.44 TeV are reported. The results are presented for charged particles produced at midrapidity as a function of centrality and transverse momentum for the 5–70% and 0.2–6 GeV/c ranges, respectively. The ratio between v2{ SP} and the elliptic flow coefficient relative to the participant plane v2{4}, estimated using four-particle correlations, deviates by up to 20% from unity depending on centrality. This observation differs strongly from the magnitude of the corresponding eccentricity ratios predicted by the TRENTo and the elliptic power models of initial state fluctuations that are tuned to describe the participant plane anisotropies. The differences can be interpreted as a decorrelation of the neutron spectator plane and the reaction plane because of fragmentation of the remnants from the colliding nuclei, which points to an incompleteness of current models describing the initial state fluctuations. A significant transverse momentum dependence of the ratio v2{ SP}/v2{4} is observed in all but the most central collisions, which may help to understand whether momentum anisotropies at low and intermediate transverse momentum have a common origin in initial state f luctuations. The ratios of v2{ SP} and v2{4} to the corresponding initial state eccentricities for Xe–Xe and Pb–Pb collisions at similar initial entropy density show a difference of (7.0 ±0.9)%with an additional variation of +1.8% when including RHIC data in the TRENTo parameter extraction. These observations provide new experimental constraints for viscous effects in the hydrodynamic modeling of the expanding quark–gluon plasma produced in heavy-ion collisions at the LHC

Creating a diophantine description of a r.e. set and on the complexity of such a description

A very old class of problems in mathematics is the solving of Diophantine equations. Essentially a Diophantine equation is a polynomial equation that should be solved in the natural numbers. While solutions to specific Diophantine equations have of course been found, a general method to solve any given Diophantine equation has not. In 1900 Hilbert considered this a suficiently important problem to include the finding of such a method in his famous list of at that time unsolved mathematical problems. In 1970 Matijasevic [6] showed that such a method does not exist. I will give a proof of the non-existence of such an algorithm that resembles proofs that were developed later. The main idea used in section 3 strongly resembles the method used in 1975 by Matijasevic and Robinson [8], although many details are handled in a different way here. Section 4 uses some of the same methods as presented in 1984 by Jones and Matijasevic [5], but they are applied to a different formalization here. After giving the proof I will briefly discuss some complexity measures that could have applications when considering the solvability of diophantine equations in a fixed number of unknowns.

Solving the undecidability of the continuum hypothesis: a short summary of the results since 1963

In 1891 Georg Cantor proved that there exist multiple size of infinity. In particular, the size of the natural numbers, @0, is not the same as that of the reals. This of course begs the question: is there a set larger than the natural numbers, but smaller than the reals? The Continuum Hypothesis (CH) is the statement that there is no such set. Since the reals can be seen as the powerset of the natural numbers, CH can be written as ’2@0 = @1’. Cantor tried to prove CH, but he failed (obviously, as would later be shown). CH then made it on the list of Hilbert’s 23 problems (problem 1). A first step to a solution for CH came in 1940, by Kurt G¨odel, who proved that CH is consistent with the axioms of Zermelo-Fraenkel set theory and the axiom of choice (ZFC) [4]. At that point however, it was already clear that the best solution was probably ¬CH. In 1947 G¨odel published an article where he concluded that ¬CH is probably consistent with ZFC too, and an important task in set theory would be to find an extra axiom that would decide the problem in favor of ¬CH [5]. The first part of G¨odels prediction came true in 1963 when Paul Cohen proved the consistency of ¬CH with ZFC [2]. The second part of G¨odels prediction is being worked on. I’ll discuss part of Cohen’s method to prove the consistency of ¬CH with ZFC, and some of the results in finding a new axiom that would solve the continuum hypothesis. This article is based mostly on the Bourbaki Lecture ’Progr`es r´ecents sur l’hypoth`ese du continu [d’apres Woodin]’ by Patrick Dehornoy in 2003 [3], in which results by Hugh Woodin on solving the continuum hypothesis are discussed.

π0 and η meson production in proton-proton collisions at √s = 8 TeV

An invariant differential cross section measurement of inclusive π0 and η meson production at mid-rapidity in pp collisions at √s = 8 TeV was carried out by the ALICE experiment at the LHC. The spectra of π0 and η mesons were measured in transverse momentum ranges of 0.33.5 GeV/c. However, a deviation from this empirical scaling rule is observed for transverse momenta below pT<3.5 GeV/c in the η/ π0 ratio with a significance of 6.2 σ

D-Meson Azimuthal Anisotropy in Midcentral Pb-Pb Collisions at √sNN = 5.02 TeV

The azimuthal anisotropy coefficient v2 of prompt D0, D+, D∗+, and Ds+ mesons was measured in midcentral (30%-50% centrality class) Pb-Pb collisions at a center-of-mass energy per nucleon pair √sNN=5.02 TeV, with the ALICE detector at the LHC. The D mesons were reconstructed via their hadronic decays at midrapidity, |y|<0.8, in the transverse momentum interval 1<pT<24 GeV/c. The measured D-meson v2 has similar values as that of charged pions. The Ds+ v2, measured for the first time, is found to be compatible with that of nonstrange D mesons. The measurements are compared with theoretical calculations of charm-quark transport in a hydrodynamically expanding medium and have the potential to constrain medium parameters