Prospects of measuring the CKM matrix element |Vts| at the LHC

2010/05/31 by Ahmed Ali, F. Barreiro, Fernando Barreiro +2
Physics and Astronomy · #Cabibbo–Kobayashi–Maskawa matrix #High-Energy Particle Collisions Research #Large Hadron Collider #Lepton #Nuclear physics #Particle Detector Development and Performance #Particle physics #Particle physics theoretical and experimental studies #Physics #Physics beyond the Standard Model #Quark #Tevatron #Top quark #hep-ex #hep-ph

paper · pdf · doi:10.1016/j.physletb.2010.08.014

published as Phys.Lett.B693:44-51,2010 · 17 pages, 6 figures, 2 tables, improved the text and the quality of figures; added two references; version to appear in Physics Letters B

arxiv created 2010/08/10 · openalex publication_date 2010/08/13 · arxiv updated 2014/11/21 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05

Abstract

We study the prospects of measuring the CKM matrix element \vert V_ts\vert at the LHC with the top quarks produced in the processes p p → ttX and p p → t/t X, and the subsequent decays t → W⁺s and t → W^- s. We insist on tagging the W^± leptonically, W^± → ℓ^± ν_ℓ (ℓ =e, μ, τ), and analyse the anticipated jet profiles in the signal process t → W s and the dominant background from the decay t → W b. To that end, we analyse the V0 (K⁰ and Λ) distributions in the s- and b-quark jets concentrating on the energy and transverse momentum distributions of these particles. The V0s emanating from the t → W b branch have displaced decay vertexes from the interaction point due to the weak decays b → c → s and the b-quark jets are rich in charged leptons. Hence, the absence of secondary vertexes and of the energetic charged leptons in the jet provide additional (b-jet vs. s-jet) discrimination in top quark decays. These distributions are used to train a boosted decision tree (BDT). Using the BDT classifier, and a variant of it called BDTD, which makes use of decorrelated variables, we calculate the BDT(D)-response functions corresponding to the signal (t → W s) and background (t → W b). Detailed simulations undertaken by us with the Monte Carlo generator PYTHIA are used to estimate the background rejection versus signal efficiency for three representative LHC energies √(s)=7 TeV, 10 TeV and 14 TeV. We argue that a benchmark with 10% signal (t → W s ) efficiency and a background (t → W b) rejection by a factor 10³ (required due to the anticipated value of the ratio \vert V_ts\vert²/\vert V_tb \vert² ≃ 1.6 × 10^-3) can be achieved at the LHC@14 TeV with an integrated luminosity of 10 fb^-1.

Citations

• Review of Particle Physics
• Observation of the Top Quark
• Theoretical top quark cross section at the Fermilab Tevatron and the CERN LHC
• Observation of Top Quark Production inp¯pCollisions with the Collider Detector at Fermilab
• Heavy-Flavor Production at Accelerators
• Updated predictions for the total production cross sections of top and of heavier quark pairs at the Tevatron and at the LHC
• First Observation of Elec-troweak Single Top Quark Production
• CP-Violation in the Renormalizable Theory of Weak Interaction
• Big Bang Nucleosynthesis (in "The Review of Particle Properties" 2004)
• Next-to-leading order corrections to single top quark production and decay at the Fermilab Tevatron:s-channel process

Cited by

• Using single top rapidity to measureVtd,Vts,Vtbat hadron colliders