Measurement of subjet multiplicities in neutral current deep inelastic scattering at HERA and determination of α s

AbstractThe subjet multiplicity has been measured in neutral current e + p interactions at Q 2 > 125 GeV 2 with the ZEUS detectorat HERA using an integrated luminosity of 38 . 6pb −1 . Jets were identified in the laboratory frame using the longitudinallyinvariant k T cluster algorithm. The number of jet-like substructures within jets, known as the subjet multiplicity, is definedas the number of clusters resolved in a jet by reapplying the jet algorithm at a smaller resolution scale y cut . Measurementsof the mean subjet multiplicity, n sbj , for jets with transverse energies E T , jet > 15 GeV are presented. Next-to-leading-orderperturbative QCD calculations describe the measurements well. The value of α s (M Z ) , determined from n sbj at y cut =10 −2 for jets with 25

Keywords:

• Neutral current
• Deep inelastic scattering
• HERA
• Particle physics
• Quantum chromodynamics
• Physics
• Nuclear physics
• Multiplicity (mathematics)
• Luminosity

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