Measurement of b hadron lifetimes in pp collisions at

Area of Science:

• High-energy particle physics
• Hadron spectroscopy
• Quantum chromodynamics

Background:

• Understanding the properties of heavy quarks and their bound states (hadrons) is crucial for testing the Standard Model of particle physics.
• Precise measurements of hadron lifetimes provide sensitive probes of fundamental interactions and potential deviations from theoretical predictions.

Purpose of the Study:

• To present precise measurements of the lifetimes of various B hadrons (B+, B0, Bs0, and Lambda_b0).
• To utilize a large dataset collected by the CMS detector at the LHC for enhanced precision.
• To compare experimental results with theoretical expectations and existing world-average values.

Main Methods:

• Analysis of a data sample corresponding to an integrated luminosity of 19.7 fb^-1 from proton-proton collisions at sqrt(s) = 13 TeV.
• Utilizing specific decay channels for each hadron type to reconstruct their decays.
• Employing sophisticated data analysis techniques within the CMS detector framework to determine decay times and lifetimes.

Main Results:

• The B+ lifetime was measured as 1.638 ± 0.004 ps and 1.641 ± 0.007 ps, yielding a combined value of 1.639 ± 0.003 ps.
• The effective lifetime of the Bs0 meson was measured in two decay modes as 1.507 ± 0.014 ps and 1.450 ± 0.030 ps.
• The B0 lifetime was determined to be 1.521 ± 0.005 ps.
• The Lambda_b0 lifetime was measured to be 1.472 ± 0.009 ps, with a measurement relative to the B0 to reduce systematic uncertainty.

Conclusions:

• All measured hadron lifetimes are in excellent agreement with current world-average values.
• The precision achieved in these measurements is competitive with or surpasses previous experimental results.
• These precise measurements contribute to a robust understanding of heavy quark hadron properties and provide stringent tests of theoretical models.