Applicability of transverse mass scaling in hadronic collisions at energies available at the CERN Large Hadron Collider

Abstract

We present a study on the applicability of transverse mass scaling for identified particle spectra in proton-proton collisions at √ s = 7 TeV based on data taken by the ALICE experiment at the LHC. The measured yields are parametrized and compared to estimates obtained from a generalized transverse mass scaling approach applied to different reference particle spectra. It is found that generalized transverse mass scaling is not able to describe the measured spectra over the full range in transverse momentum. At low p T , deviations of 20% or more are obtained, in particular, if pions are used as reference particles. A better scaling performance is obtained when kaons are used as reference particles. At high p T all tested spectra with the possible exception of the charged kaons exhibit a scaling behavior. Investigating the feed-down contributions from resonance decays to the charged pion yields reveals, that using them as reference a general scaling may not be achievable. Our findings imply that for precision measurements of direct photon and di-electron spectra at low transverse momentum one should measure the relevant hadronic background, instead of relying on m T scaling for its estimate.

Neutral mesons production measured with the ALICE experiment

“…Results show the universal character among collision energies and systems, and agree within uncertainties with the world data [4]. The significant (above 6σ for pp collisions at √ s = 8 TeV) deviation from m T scaling prediction at low-p T is visible in pp collsions as seen also for other mesons at LHC energies [16]. The origin is most likely from additional contributions to light mesons from heavier resonance decays.…”

Production of the ρ(770)0 meson in pp and Pb-Pb collisions at sAcharya1, Acosta2, Adamová3 et al. 2019Phys. Rev. C302210View full textAdd to dashboardCite

“…For pp collisions at √ s = 2.76 TeV, the shape of the ω(782) p T spectrum is approximated using the fit to π spectrum [47] with a m T -scaling correction [59]. The function, which is fit to the transverse-momentum distribution of pions, is transformed into a production spectrum of ω(782) in two steps.…”

Measurement of dielectron production in central Pb-Pb collisions at sNN=2.76TeV

“…This is done by randomly adding hadrons to a pure sample of electrons such that the hadron-to-electron ratio reproduces the same ratio estimated in real data, in each momentum interval, and for each hadron species. The input transverse-momentum distributions of dielectron sources in the MC simulation are corrected, using p T -dependent weights obtained from the measured spectra [47][48][49][50], to have the same relative particle abundances as in data. The invariantmass distribution of correlated electron-hadron and hadronhadron pairs is shown in Fig.…”

“…This injected sample includes π 0 , η, η , ρ 0 , ω, φ, and J/ψ, forced to decay into dielectrons, produced in equal amounts with uniform p T distributions, and an enriched sample of heavy-flavor sources with forced semileptonic decay channel. The input p T distributions of dielectron sources are corrected using p T -dependent weights, which include a correction factor to adjust their relative particle abundances according to measurements [47,48,50]. The p T -differential cross section of neutral pions measured by ALICE [48] is used as a reference to modify the input spectrum of π 0 , while the shapes of p T distributions of all other light-flavor mesons are obtained from m T -scaling of the π 0 spectrum, replacing p T with √ m 2 − m 2 π + (p T /c) 2 .…”