B→πℓνat zero recoil from lattice QCD with physicalu/dquarks
| Autor: | G. P. Lepage, R. J. Dowdall, Jonna Koponen, Christine Davies, B. Colquhoun |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
Quark
Semileptonic decay Physics Particle physics Chiral perturbation theory 010308 nuclear & particles physics High Energy Physics::Lattice High Energy Physics::Phenomenology Lattice QCD 01 natural sciences Pion Recoil 0103 physical sciences Pi High Energy Physics::Experiment Matrix element 010306 general physics |
| Zdroj: | Physical Review D. 93 |
| ISSN: | 2470-0029 2470-0010 |
| DOI: | 10.1103/physrevd.93.034502 |
| Popis: | The exclusive semileptonic decay $B\ensuremath{\rightarrow}\ensuremath{\pi}\ensuremath{\ell}\ensuremath{\nu}$ is a key process for the determination of the Cabibbo-Kobayashi-Maskawa matrix element ${V}_{ub}$ from the comparison of experimental rates as a function of ${q}^{2}$ with theoretically determined form factors. The sensitivity of the form factors to the $u/d$ quark mass has meant significant systematic uncertainties in lattice QCD calculations at unphysically heavy pion masses. Here, we give the first lattice QCD calculations of this process for $u/d$ quark masses going down to their physical values, calculating the ${f}_{0}$ form factor at zero recoil to 3%. We are able to resolve a long-standing controversy by showing that the soft-pion theorem result ${f}_{0}({q}_{\mathrm{max}}^{2})={f}_{B}/{f}_{\ensuremath{\pi}}$ does hold as ${m}_{\ensuremath{\pi}}\ensuremath{\rightarrow}0$. We use the highly improved staggered quark formalism for the light quarks and show that staggered chiral perturbation theory for the ${m}_{\ensuremath{\pi}}$ dependence is almost identical to continuum chiral perturbation theory for ${f}_{0}$, ${f}_{B}$, and ${f}_{\ensuremath{\pi}}$. We also give results for other processes such as ${B}_{s}\ensuremath{\rightarrow}K\ensuremath{\ell}\ensuremath{\nu}$. |
| Databáze: | OpenAIRE |
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