2020/05/31 by Bhubanjyoti Bhattacharya, Alakabha Datta, Saeed Kamali +1 · 2 citations
Physics and Astronomy · #Angular displacement #Angular momentum #Angular resolution (graph drawing) #Distribution (mathematics) #Kinematics #Measure (data warehouse) #Neutrino Physics Research #Particle physics theoretical and experimental studies #Quantum Chromodynamics and Particle Interactions #hep-ex #hep-ph
paper · pdf · doi:10.1007/jhep07(2020)194
published as J. High Energ. Phys. 07 (2020) 194 · 28 pages, 2 figures, 7 tables, presentation format for angular distribution revised, typos corrected, references added, to appear in JHEP
openalex created_date 2020/05/13 · openalex publication_date 2020/07/01 · arxiv created 2020/07/06 · arxiv updated 2020/07/29 · openalex updated_date 2026/08/05
A bstract At present, the measurements of RD(∗ ) <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>R</mml:mi> <mml:msup> <mml:mi>D</mml:mi> <mml:mfenced> <mml:mo>∗</mml:mo> </mml:mfenced> </mml:msup> </mml:msub> </mml:math> and R J/ψ hint at new physics (NP) in b→ cτ-v <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>b</mml:mi> <mml:mo>→</mml:mo> <mml:mi>c</mml:mi> <mml:msup> <mml:mi>τ</mml:mi> <mml:mo>−</mml:mo> </mml:msup> <mml:mover> <mml:mi>v</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> </mml:math> decays. The angular distribution of B→ D∗(→ Dπ )τ-vτ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mover> <mml:mi>B</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> <mml:mo>→</mml:mo> <mml:msup> <mml:mi>D</mml:mi> <mml:mo>∗</mml:mo> </mml:msup> <mml:mfenced> <mml:mrow> <mml:mo>→</mml:mo> <mml:mi>Dπ</mml:mi> </mml:mrow> </mml:mfenced> <mml:msup> <mml:mi>τ</mml:mi> <mml:mo>−</mml:mo> </mml:msup> <mml:msub> <mml:mover> <mml:mi>v</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> <mml:mi>τ</mml:mi> </mml:msub> </mml:math> would be useful for getting information about the NP, but it cannot be measured. The reason is that the three-momentum \overrightarrowpτ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mover> <mml:mi>p</mml:mi> <mml:mo>→</mml:mo> </mml:mover> <mml:mi>τ</mml:mi> </mml:msub> </mml:math> cannot be determined precisely since the decay products of the τ − include an undetected ν τ . In this paper, we construct a measurable angular distribution by considering the additional decay τ − → π − ν τ . The full process is B→ D∗(→ Dπ′)τ-(→ π-vτ)vτ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mover> <mml:mi>B</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> <mml:mo>→</mml:mo> <mml:msup> <mml:mi>D</mml:mi> <mml:mo>∗</mml:mo> </mml:msup> <mml:mfenced> <mml:mrow> <mml:mo>→</mml:mo> <mml:mi>D</mml:mi> <mml:msup> <mml:mi>π</mml:mi> <mml:mo>′</mml:mo> </mml:msup> </mml:mrow> </mml:mfenced> <mml:msup> <mml:mi>τ</mml:mi> <mml:mo>−</mml:mo> </mml:msup> <mml:mfenced> <mml:mrow> <mml:mo>→</mml:mo> <mml:msup> <mml:mi>π</mml:mi> <mml:mo>−</mml:mo> </mml:msup> <mml:msub> <mml:mi>v</mml:mi> <mml:mi>τ</mml:mi> </mml:msub> </mml:mrow> </mml:mfenced> <mml:msub> <mml:mover> <mml:mi>v</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> <mml:mi>τ</mml:mi> </mml:msub> </mml:math> , which includes three final-state particles whose three-momenta can be measured: D , π ′ , π − . The magnitudes and relative phases of all the NP parameters can be extracted from a fit to this angular distribution. One can measure CP-violating angular asymmetries. If one integrates over some of the five kinematic parameters parametrizing the angular distribution, one obtains (i) familiar observables such as the q 2 distribution and the D ∗ polarization, and (ii) new observables associated with the π − emitted in the τ decay: the forward-backward asymmetry of the π − and the CP-violating triple-product asymmetry.