$B \to \rho \ell \bar{\nu}$ resonance form factors from $B \to \pi \pi \ell \bar{\nu}$ in lattice QCD

Leskovec, Luka (author), Meinel, Stefan (author), Petschlies, Marcus (author), Negele, John W. (author), Paul, Srijit (author), Pochinsky, Andrew (author)

The decay $B \to \rho \ell \bar{\nu}$ is an attractive process for determining the magnitude of the smallest Cabibbo-Kobayashi-Maskawa matrix element, $|V_{ub}|$, and can provide new insights into the origin of the longstanding exclusive-inclusive discrepancy in determinations of this standard-model parameter. This requires a nonperturbative QCD calculation of the $B \to \rho$ form factors $V$, $A_0$, $A_1$, and $A_{12}$. The unstable nature of the $\rho$ resonance has prevented precise lattice QCD calculations of these form factors to date. Here, we present the first lattice QCD calculation of the $B \to \rho$ form factors in which the $\rho$ is treated properly as a resonance in $P$-wave $\pi \pi$ scattering. To this end, we use the Lellouch-Lüscher finite-volume formalism to compute the $B \to \pi \pi$ form factors as a function of both momentum transfer and $\pi \pi$ invariant mass, and then analytically continue to the $\rho$ resonance pole. This calculation is performed with 2 + 1 dynamical quark flavors at a pion mass of approximately 320 MeV, and demonstrates a clear path toward results at the physical point.

• Language: English
• Keywords: physics of elementary particles, particle interactions, lattice QCD, form factors
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FMF - Faculty of Mathematics and Physics
• Publication status: Published
• Publication version: Version of Record
• Year: 2025
• Number of pages: Str. 161901-1-161901-8
• Numbering: Vol. 134, iss. 16
• PID: 20.500.12556/RUL-168786
• UDC: 539.120.811
• ISSN on article: 0031-9007
• DOI: 10.1103/PhysRevLett.134.161901
• COBISS.SI-ID: 234136323
• Publication date in RUL: 24.04.2025

Record is a part of a journal

• Title: Physical review letters
• Shortened title: Phys. rev. lett.
• Publisher: American Physical Society
• ISSN: 0031-9007
• COBISS.SI-ID: 1282575

Licences

• License: CC BY 4.0, Creative Commons Attribution 4.0 International
• Link: http://creativecommons.org/licenses/by/4.0/
• Description: This is the standard Creative Commons license that gives others maximum freedom to do what they want with the work as long as they credit the author.

Secondary language

• Language: Slovenian
• Keywords: fizika osnovnih delcev, interakcije delcev, kvantna kromodinamika na mreži, oblikovni faktorji