Strangeness Production In Pp Collisions Research Articles

Probing the interplay of multiplicity and effective energy on strangeness production in pp collisions with ALICE

The strong interaction between quarks and gluons, the elementary constituents of the hadronic matter, is described by quantum chromodynamics (QCD). Under extreme conditions of high temperature and energy density, the QCD predicts a transition from the hadronic phase to a colour deconfined medium called quark-gluon plasma (QGP). The QGP can be investigated in the laboratory through ultrarelativistic heavy-ion collisions, such as the ones between lead (Pb) ions at the Large Hadron Collider (LHC) at CERN. The enhanced production of strange hadrons in heavy-ion collisions with respect to proton-proton (pp) collisions was historically considered one of the signatures of QGP formation. At the LHC, the ALICE Collaboration observed that the ratio of strange to non-strange hadron yields increases with the charged-particle multiplicity at midrapidity, starting from pp collisions and evolving smoothly across larger interaction systems and energies, ultimately reaching Pb-Pb collisions. The origin of this effect in small collision systems remains an open question. This work exploits a novel approach to study strangeness production in pp collisions, introducing, for the first time, the concept of effective energy in hadronic collisions at the LHC.

A multi-differential investigation of strangeness production in pp collisions with ALICE

In these proceedings, two multi-differential analyses performed in pp collisions collected by the ALICE collaboration during the LHC Run 2 are presented. One investigates the dependence of strange particle production with multiplicity and effective energy, whereas the other clarifies how strangeness enhancement is correlated to the leading jet in the event. The results suggest that strangeness production at the LHC depends strongly on effective energy, and originates dominantly from the transverse region with respect to the leading jet direction.

New indication on scaling properties of strangeness production in pp collisions at RHIC

Experimental data on transverse momentum spectra of strange particles [Formula: see text] produced in [Formula: see text] collisions at [Formula: see text] obtained by the STAR and PHENIX collaborations at RHIC are analyzed in the framework of [Formula: see text]-scaling approach. The concept of the [Formula: see text]-scaling is based on fundamental principles of self-similarity, locality, and fractality of hadron interactions at high energies. General properties of the data [Formula: see text]-presentation are studied. Self-similarity of fractal structure of protons and fragmentation processes with strange particles is discussed. A microscopic scenario of constituent interactions developed within the [Formula: see text]-scaling scheme is used to study the dependence of momentum fractions and recoil mass on the collision energy, transverse momentum and mass of produced inclusive particle, and to estimate the constituent energy loss. We consider that obtained results can be useful in study of strangeness origin, in searching for new physics with strange probes, and can serve for better understanding of fractality of hadron interactions at small scales.

Self-similarity of strangeness production in pp collisions at RHIC

New experimental data on transverse momentum spectra of strange particles (K0S,K–, K*, ϕ, …) produced in pp collisions at √s = 200 GeV obtained by the STAR and PHENIX collaborations at RHIC are analysed in the framework of z-scaling approach. Scaling properties of the data z-presentation are illustrated. Self-similarity of strange particle production is discussed. A microscopic scenario of constituent interactions developed within the z-scaling approach is used to study constituent energy loss, proton momentum fraction and recoil mass in dependence on the transverse momentum, strangeness, and mass of the inclusive particle. The obtained results can be useful for understanding strangeness origin, for searching for new physics with strange probes and can serve as a benchmark for complex analyses of self-similar features of strange production in heavy ion collisions.

Strangeness measurements at LHC with ALICE

A review of the first results obtained on strangeness production in pp collisions at 0.9 and 7 TeV cm. energy with the ALICE detector at LHC will be presented. About 250,000 minimum bias events recorded in 2009 during the very first LHC runs at 0.9 TeV were analyzed. Preliminary results on central rapidity production of mesons containing strange quarks (K±, Ks0, ϕ(1020)) as well as single and double strange baryons are reported. More than 400 million minimum bias events have been collected up to now at 7 TeV by the ALICE experiment. Using only a fraction of the collected events the signals of many strange mesons (Ks0), hyperons and resonances (K*(892)0, ϕ(1020) and Σ(1385)) have been extracted. The ϕ(1020) invariant mass and the raw yield of as a function of transverse momentum will be shown.

First measurements of strangeness production in pp collisions with the ALICE experiment at LHC

The status of strange baryon and anti-baryon analysis in pp collisions at LHC is reported. It is based on ALICE pp data collected at s = 900 GeV and 7 TeV. The performance of K S 0 , Λ ( Λ ¯ ), Ξ ( Ξ ¯ ) and Ω ( Ω ¯ ) reconstruction via their weak decay topology is described. Transverse momentum spectra extracted at central rapidity are presented.

Resonance model study of strangeness production in pp collisions

Results for the energy dependence of the elementary kaon production cross sections in proton-proton collisions are reported. Calculations are performed within an extended version of the resonance model which was used for the previous studies of elementary kaon production in pion-nucleon and pion-Δ collisions. Although the model treatment is within the empirical tree level (observed widths for the resonances are used), it is fully relativistic, and includes all relevant baryon resonances up to 2 GeV. One of the purposes of this study is to provide the results for the simulation codes of subthreshold kaon production in heavy ion collisions. This is the first, consistent study of the elementary kaon production reactions including both πB and BB ( B = N, Δ) collisions on the same footing. Comparisons are made between the calculated results and the existing semi-empirical parametrizations which are widely used for the simulation codes, as well as the experimental data.

High resolution study ofhyperon-nucleon interactions by associated strangeness production in pp collisions

The associated strangeness production in pp collisions was studied at bombarding energies of 2.3 and 2.7 GeV by detecting the outgoing K + particles with a high resolution magnetic spectrometer at forward angles up to 23.5° laboratory angle. The kaons were separated from an immense background of protons and pions by a highly resolving TOF electronics addition to vetoes from Čerenkov detectors utilizing either β differing Čerenkov light cones in lucite or different thresholds for light production in aerogel. The hyperon-nucleon missing mass spectra obtained show strong deviations from pure phase space which is ascribed to final state interactions of the pΛ and the Nσ systems. The structures found are discussed and compared with results from K −d → π −YN experiments, with theoretical calculations in the frame of OBE models, and with the prediction of sharp strange dibaryon resonances from several quark-bag models.