[Paper Review] Hadron-hadron interactions measured by ALICE at the LHC

L. Fabbietti, V. M. Sarti+1 more|arXiv (Cornell University)|Dec 18, 2020

High-Energy Particle Collisions Research4 references5 citations

TL;DR

This paper reviews ALICE's novel method using momentum-space correlations in pp and p-Pb collisions to probe the strong interaction between hadrons, including unstable ones like hyperons and kaons. The approach enables precise measurement of hadron-hadron interactions previously difficult to access, opening a new pathway to study residual strong forces across all hadron pairs.

ABSTRACT

The strong interaction among hadrons has been measured in the past by scattering experiments. But while this technique was extremely successful in providing information about the nucleon-nucleon and pion-nucleon interactions, when unstable hadrons are considered the experiments become more challenging. In the last few years the analysis of correlations in the momentum space for pairs of stable and unstable hadrons measured in pp and p-Pb collisions by ALICE at the LHC provided a new method to investigate the strong interaction among hadrons. In this article we provide a review of the numerous results recently achieved for hyperon-nucleon, hyperon-hyperon and kaon-nucleon pairs showing that the new method opens the possibility of measuring the residual strong interaction of any hadron pair.

Motivation & Objective

• To investigate the strong interaction between hadrons, particularly unstable resonances like hyperons and kaons, which are difficult to study with traditional scattering methods.
• To overcome experimental challenges in measuring interactions involving short-lived hadrons by leveraging high-precision correlation measurements in high-energy collisions.
• To demonstrate that momentum-space correlations in pp and p-Pb collisions provide a viable and powerful alternative to conventional scattering experiments for probing hadron-hadron interactions.
• To extend the reach of strong interaction studies to include all hadron pairs, including those involving exotic or resonant states.

Proposed method

• Utilizes two-particle momentum-space correlations measured in pp and p-Pb collisions at the LHC using the ALICE detector.
• Applies the HBT (Hanbury Brown and Twiss) interferometry technique to extract information about the spatial and temporal characteristics of the particle emission source.
• Analyzes correlations between pairs of stable and unstable hadrons (e.g., hyperon-nucleon, hyperon-hyperon, kaon-nucleon) to infer the strength and nature of their residual strong interactions.
• Extracts scattering parameters such as the scattering length and effective range from the correlation functions, using theoretical models to interpret the data.
• Combines data from multiple collision systems and center-of-mass energies to enhance statistical precision and extract universal features of hadron interactions.
• Validates the method by comparing results with known interactions (e.g., nucleon-nucleon) and extending it to previously inaccessible systems.

Experimental results

Research questions

• RQ1 Can momentum-space correlations in high-energy hadronic collisions be used to extract the strong interaction parameters between hadrons, including unstable resonances?
• RQ2 How do the measured correlation functions for hyperon-nucleon and hyperon-hyperon pairs compare with theoretical predictions for their strong interactions?
• RQ3 To what extent can this method be generalized to study the strong interaction between any pair of hadrons, regardless of stability?
• RQ4 What are the scattering lengths and effective ranges for kaon-nucleon and hyperon-hyperon systems as inferred from correlation data?
• RQ5 How does the method's precision and sensitivity compare to traditional scattering experiments for unstable hadron systems?

Key findings

• The correlation method successfully measures the strong interaction between hyperon-nucleon pairs, providing new constraints on their scattering parameters.
• Evidence for significant hyperon-hyperon interactions is observed, indicating non-trivial strong-force effects in these systems.
• Scattering lengths for kaon-nucleon interactions are extracted with high precision, consistent with expectations from chiral perturbation theory.
• The method demonstrates sensitivity to short-lived resonances, enabling the study of strong interactions involving unstable hadrons previously inaccessible to conventional techniques.
• The technique is validated by reproducing known nucleon-nucleon scattering parameters from correlation data, confirming its reliability.
• The approach opens a new, scalable pathway for measuring strong interactions across the entire hadron spectrum, including exotic and resonant states.