A baryon ( , proper decay length ) is produced with laboratory momentum . A silicon…

PHYSICS · Multi-part · Fermi University Physics · Particle Physics & Quantum Fields · Particles, interactions and experiment · Particles, interactions and experiment

Symmetry and Flavour, Ch The collider experiment: from bunch populations to a measured cross section

Problem

A Λb0\Lambda_b^0 baryon (m=5.620 GeVm = 5.620\,\mathrm{GeV}, proper decay length cτ=441 μmc\tau = 441\,\mu\mathrm{m}) is produced with laboratory momentum p=40 GeVp = 40\,\mathrm{GeV}. A silicon vertex detector resolves the impact parameter of a charged track to 1010-20 μm20\,\mu\mathrm{m}. ((a)) Estimate the mean laboratory decay length ⟨ℓ⟩\langle\ell\rangle of this Λb0\Lambda_b^0. ((b)) Explain, in one or two sentences, why the typical impact parameter of a decay daughter is of order cτc\tau rather than of order ⟨ℓ⟩\langle\ell\rangle, and use this to decide whether the stated vertex resolution is adequate to tag this decay.

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