Study of central pp and p-Pb collisions using flattenicity with ALICE at the LHC

In this seminar I will introduce a novel event-activity estimator named flattenicity, which has been built to select central pp and p-Pb collisions at the Large Hadron Collider energies. Monte Carlo (MC) simulations incorporating an impact-parameter dependence of multiparton interactions (MPI) show that in central pp collisions the high-pT particle yield exhibits an approximate scaling with the number of binary parton-parton interactions. This behavior is recovered using flattenicity that quantifies the event activity with small biases due to local multiplicity fluctuations. Therefore, a modification factor (Qpp) can be defined in analogy to the nuclear modification factor typically measured in heavy-ion collisions to study parton-energy loss effects. The first ALICE results including pT spectra and Qpp as a function of pT in pp collisions at √s=13 TeV for unidentified charged particles, as well as for charged pions, kaons and (anti)protons will be presented. The measurements were performed from hundreds of MeV up to 20 GeV/c. Within the limited pT reach (10-20 GeV/c), no deviation from the MC baseline is seen. At intermediate pT, the Qpp factor exhibits a structure that is mass dependent. In contrast to analogous studies as a function of multiplicity, a steeper increase of the kaon-to-pion ratio is observed in the new set of measurements. Data will be discussed in the context of QCD-inspired event generators.

References:

The ALICE Collaboration, arXiv:2407.20037

A. Ortiz et al., arXiv:2408.06340

https://cuaieed-unam.zoom.us/j/86190366383?pwd=E9sm6BpDXxE6A7yfQdYH14zdYYUClK.1

Meeting ID: 861 9036 6383
Passcode: 892172