Sum rules for b→cτν transitions to orbitally excited charm hadrons show larger deviations from heavy quark symmetry than ground states, with tensor effects often sizable, but current form factor uncertainties prevent robust lepton-universality predictions.
Semileptonic Λ b decay to excited Λ c baryons at order ΛQCD/mQ
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abstract
Exclusive semileptonic Lambda_b decays to excited charmed Lambda_c baryons are investigated at order Lambda_{QCD}/m_Q in the heavy quark effective theory. The differential decay rates are analyzed for the J^\pi=1/2^- Lambda_c(2593) and the J^\pi=3/2^- \Lambda_c(2625). They receive 1/m_{c,b} corrections at zero recoil that are determined by mass splittings and the leading order Isgur-Wise function. With some assumptions, we find that the branching fraction for Lambda_b decays to these states is 2.5-3.3%. The decay rate to the helicity \pm 3/2 states, which vanishes for m_Q \to \infty, remains small at order Lambda_{QCD}/m_Q since 1/m_c corrections do not contribute. Matrix elements of weak currents between a Lambda_b and other excited Lambda_c states are analyzed at zero-recoil to order Lambda_{QCD}/m_Q. Applications to baryonic heavy quark sum-rules are explored.
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hep-ph 2years
2026 2verdicts
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Hammer v2 updates the helicity amplitude reweighting library with near-linear scaling for high-dimensional tensor operations in BSM and form-factor spaces plus improved Python bindings.
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$b \to c$ semileptonic sum rule: orbitally excited hadrons
Sum rules for b→cτν transitions to orbitally excited charm hadrons show larger deviations from heavy quark symmetry than ground states, with tensor effects often sizable, but current form factor uncertainties prevent robust lepton-universality predictions.
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An introduction to Hammer v2: Helicity Amplitude Module for Matrix Element Reweighting
Hammer v2 updates the helicity amplitude reweighting library with near-linear scaling for high-dimensional tensor operations in BSM and form-factor spaces plus improved Python bindings.