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Sara Pucillo

Publications and source records attributed to Sara Pucillo.

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Probing Strange-Quark Hadronization via (Multi-)Strange Hadron Multiplicity Distributions in Small Collision Systems with ALICE

Strangeness enhancement is defined as the increased relative production of strange hadrons in heavy-ion collisions compared to proton--proton (pp) interactions. It was originally proposed as one of the signatures of quark--gluon plasma (QGP) formation. At the LHC, the ALICE experiment observed that strange-hadron-to-pion yield ratios rise with increasing charged-particle multiplicity at midrapidity, independently of collision energy ($\sqrt{s}$) and system size, from pp to p--Pb and up to Pb--Pb collisions. To gain deeper insight into the mechanisms of strangeness production, the ALICE collaboration has measured the probability distribution of producing a given number of strange particles ($K^{0}_{S}$, $\Lambda$, $\Xi$, and $\Omega$) of the same species per event in pp collisions at $\sqrt{s}~=~5.02$ TeV. This measurement extends the study of strangeness production beyond the mean particle yield by employing, for the first time, a technique based on event-by-event particle counting. It provides a new test bench for production mechanisms, probing events with large imbalances between strange and non-strange content. The results are compared with state-of-the-art phenomenological models implemented in commonly used Monte Carlo event generators, offering enhanced sensitivity to the underlying dynamics of strangeness production.

nucl-ex

Recent results on strangeness enhancement in small collision systems with ALICE

Quantum Chromodynamics (QCD) predicts that, at sufficiently high temperature and energy density, nuclear matter undergoes a phase transition from confined hadrons to a deconfined state of quarks and gluons known as the quark-gluon plasma (QGP). One of the historically proposed signatures of QGP formation is strangeness enhancement (SE), characterized by an increased production of strange hadrons in heavy-ion collisions relative to proton--proton (pp) interactions. At the LHC, the ALICE experiment has measured a continuous increase in the strange-to-non-strange hadron yield ratios as a function of midrapidity charged-particle multiplicity, not only in large systems like Pb--Pb but also in small systems such as pp and p--Pb. The origin of SE in small systems is still under debate, motivating further experimental investigations. This article presents recent ALICE analyses that offer complementary insights into the phenomenon. These include (i) multi-differential studies using event-shape observables such as transverse spherocity and the concept of effective energy, and (ii) the first measurement of multiplicity distributions of strange and multi-strange hadrons, P($\textit{n}_{S}$), in pp collisions.

nucl-ex

New insights into strange-quark hadronization measuring multiple (multi-)strange hadron production in small collision systems with ALICE

Among the most important results from the Run-1 and Run-2 of the LHC is the observation of an enhanced production of (multi-)strange to non-strange hadron yields, gradually rising from low-multiplicity to high-multiplicity pp and p--Pb collisions, reaching values close to those measured in peripheral Pb--Pb collisions. The observed behaviour cannot be quantitatively reproduced by any of the available QCD-inspired MC generators. In this contribution an extension of this study is presented: the measurement of the ${\rm K}_{\rm S}^{0}$, $\Lambda$, $\Xi^{-}$ and $\Omega^{-}$ (together with their antiparticles) multiplicity distributions in pp collisions at $\sqrt{s}$ = 5.02 TeV as a function of the charged-particle multiplicity, together with the average probability for the multiplets production, extending the study of strangeness production beyond its average. This novel method, based on counting the number of strange particles event-by-event, represents a new test bench for production mechanisms, probing events with a large imbalance between strange and non-strange content.

hep-ex

Insights on strange quark hadronization in small collision system with ALICE: multiple strange hadrons and $\Sigma^{\pm}$ baryons

Among the most iconic results of Run-1 and Run-2 of the LHC is the observation of enhanced production of (multi-)strange to non-strange particles, gradually rising from low-multiplicity to high-multiplicity pp or p--Pb collisions and reaching values close to those measured in peripheral Pb--Pb collisions. The observed behaviour cannot be quantitatively reproduced by any of the available QCD-inspired MC generators. In this contribution two extensions of this study are presented: the measurement of $\Sigma$ baryons and the first measurement of the full Probability Density Function (PDF) for $K^{0}_{S}$, $\Lambda$, $\Xi^{-}$ and $\Omega^{-}$, therefore extending the study of strangeness production beyond the average of the distribution. This novel method represents a unique opportunity to test the connection between charged and strange particle multiplicity production.

hep-ex