Semi-leptonic B decays provide promising channels to test the Standard Model, search for signs of new physics, or determine fundamental parameters like CKM matrix elements. We present an update on our calculation of short distance contributions to GIM suppressed rare B decays focusing in particular on B s → φ + − decays. Furthermore we show first results for our calculation of B (s) → D ( * ) (s) ν semi-leptonic decays involving b → c transitions. Our calculations are based on RBC-UKQCD's 2+1 flavor domain-wall fermion and Iwasaki gauge field configurations featuring three lattice spacings in the range 1.73 GeV ≤ a −1 ≤ 2.77 GeV and pion masses down to the physical value. We calculate the form factors by simulating b-quarks using the relativistic heavy quark action, create light u/d and s quarks with standard domain-wall kernel, and use optimised Möbius domain-wall fermions for charm quarks.

We discuss first results for the computation of short distance contributions to semileptonic form factors for the rare B decays B → K * + − and B s → φ + − . Our simulations are based on RBC/UKQCD's N f = 2 + 1 ensembles with domain wall light quarks and the Iwasaki gauge action. For the valence b-quark we chose the relativistic heavy quark action.

Semi-leptonic B decays provide promising channels to test the Standard Model, search for signs of new physics, or determine fundamental parameters like CKM matrix elements. We present an update on our calculation of short distance contributions to GIM suppressed rare B decays focusing in particular on B s → φ + − decays. Furthermore we show first results for our calculation ofν semi-leptonic decays involving b → c transitions. Our calculations are based on RBC-UKQCD's 2+1 flavor domain-wall fermion and Iwasaki gauge field configurations featuring three lattice spacings in the range 1.73 GeV ≤ a −1 ≤ 2.77 GeV and pion masses down to the physical value. We calculate the form factors by simulating b-quarks using the relativistic heavy quark action, create light u/d and s quarks with standard domain-wall kernel, and use optimised Möbius domain-wall fermions for charm quarks.

B-physics is one of the most promising windows to find new physics in the flavor sector. One key ingredient to these searches are precise theoretical predictions derived from the Standard Model. Focusing at the nonperturbative QCD contributions, we carry out lattice QCD simulations in order to calculate B-meson decay constants and semi-leptonic form factors. Combined with experimental measurements our results enable us to determine CKM matrix elements.Here we present B and B s meson decay constants as well as semi-leptonic form factors including rare decays, CKM or GIM suppressed in the Standard Model. Our results are based on the set of 2+1 flavor domain-wall Iwasaki gauge field configurations generated by the RBC-UKQCD collaboration. Heavy b-quarks are simulated using the relativistic heavy quark action.

B-physics is one of the most promising windows to find new physics in the flavor sector. One key ingredient to these searches are precise theoretical predictions derived from the Standard Model. Focusing at the nonperturbative QCD contributions, we carry out lattice QCD simulations in order to calculate B-meson decay constants and semi-leptonic form factors. Combined with experimental measurements our results enable us to determine CKM matrix elements.Here we present B and B s meson decay constants as well as semi-leptonic form factors including rare decays, CKM or GIM suppressed in the Standard Model. Our results are based on the set of 2+1 flavor domain-wall Iwasaki gauge field configurations generated by the RBC-UKQCD collaboration. Heavy b-quarks are simulated using the relativistic heavy quark action.