Upsilon production at Fermilab Tevatron and LHC energies

Area of Science:

• High Energy Physics
• Quantum Chromodynamics
• Particle Phenomenology

Background:

• Direct Upsilon(nS) hadroproduction is a key process for testing Quantum Chromodynamics (QCD).
• Previous theoretical predictions faced discrepancies with experimental data from the Fermilab Tevatron.
• Understanding Upsilon production mechanisms is crucial for interpreting results at the Large Hadron Collider (LHC).

Purpose of the Study:

• To update theoretical predictions for direct Upsilon(nS) hadroproduction.
• To investigate the impact of next-to-leading order (NLO) corrections on cross-section and polarization.
• To compare updated predictions with experimental data and assess the role of color-singlet and color-octet contributions.

Main Methods:

• Utilized the framework of nonrelativistic Quantum Chromodynamics (NRQCD).
• Calculated NLO corrections in alpha(S) to the color-singlet transition for Upsilon(nS) production.
• Evaluated leading alpha(S)(5) contributions from Upsilon(nS) associated with three light partons.
• Analyzed differential cross-sections and Upsilon polarization.

Main Results:

• NLO corrections significantly increase the differential cross-section at high transverse momentum (pT).
• These corrections substantially influence the polarization of the Upsilon.
• The updated color-singlet cross-section at alpha(S)(5) shows substantial agreement with Fermilab Tevatron data.
• No evidence for the necessity of color-octet contributions was found.
• Predicted longitudinal polarization for Upsilon(nS).

Conclusions:

• The updated theoretical framework, including NLO corrections, successfully describes Upsilon(nS) hadroproduction data.
• Color-singlet contributions are sufficient to explain the observed cross-sections, diminishing the need for color-octet mechanisms.
• The study provides predictions for Upsilon(nS) production at the LHC, aiding future experimental analyses.