Great opportunities exist for improving the power of the search for BSM effects in flavor physics by improving lattice QCD calculations.
Lattice QCD calculations will greatly improve the bounds on the CKM CP violating parameters ρ and η from
B and Bs mixing (green band), K mixing (blue band), and B leptonic decay (salmon band and light yellow band).
http://latticeaverages.org
Background.
Large new computing resources and vastly improved methods will make possible in the coming decade calculations that are dramatically more precise than have been achieved in the previous decade. This dramatic progress comes at a crucial time for particle physics, because much more is now demanded of lattice QCD than ever before. Lattice QCD calculations have made critical contributions to determinations of CKM matrix elements and to searches for beyondthestandardmodel effects in flavor physics. In Fig. 1), several of the constraints on the CKM parameters ρ and η dominated by lattice uncertainties. The experimental results for K mixing (light blue band in Fig. 1) and for the ratio
B mixing/Bs mixing (green band in Fig. 1) have achieved 0.5% precision, far beyond the precisions of current lattice calculations. Future experiments will demand even more from lattice calculations. New leptonic and semileptonic B decay results expected from Belle2 will demand improved lattice calculations. For example, better measurements of B meson leptonic decay will require better calculations of fB. The uncertainty in Vcb is the crucial bottleneck in present and future rare K decay experiments. This project aims to attack all of these.
The K semileptonic decay form factor f+(0) provides the CKM matrix element Vus.
Project Goals.
This project aims at a comprehensive analysis of the physics of B, D, and K mesons with particular
emphasis on physics relevant to determinations of CKM matrix elements and quark masses.
It uses the unquenched,highly improved staggered (HISQ) fermion 2+1+1 flavor gauge configurations of the MILC collaboration,
HISQ valence quarks for the u, d, s, and c quarks, and clover heavy quarks for the b quark.
Ultimately, we aim at determinations of B, D, and K meson decay constants, semileptonic form factors, and
B B bar mixing parameters on the full MILC data set.
2013/14 Goals.
Abstract of 2013 proposal: We propose to continue with the HISQ phase of our broad flavor physics program of determining CKM matrix elements and searching for the effects of new physics in flavor physics. We focus on the leptonic and semileptonic decays and meson mixings of mesons containing a heavy b, c or s quark using highly improved staggered quarks (“HISQ” quarks) for the light valence and sea quarks. Our calculations have influenced, and will continue to influence, flavorphysics studies in the experiments BaBar, Belle, CDF, CLEOc, D0, LHCb, BES, KLOE, NA62, and ORKA. We have brought our long standing program on the “asqtad” ensembles to a close, and are analyzing the last of asqtad data whose datataking finished last year. The HISQ ensembles now being generated have 2+1+1 flavors of sea quark, with the first 2+1 masses as before, and the fourth at the physical charm mass. This library of ensembles includes light quarks at the physical mass, and these ensembles are increasingly dominating our analysis. We propose to compute D and K meson leptonic and semileptonic decays using HISQ for all valence quarks and to begin a new set of calculations of B physics with Fermilab b quarks.
In 2013/14, we plan to focus on the physical light quark mass ensembles with lattice spacing a = 0.12 and 0.09 fm. For B meson leptonic decay constant, semileptonic decay, and B mixing, we plan to analyze 16,000 timesources on the a = 0.12 fm ensemble, and 12, 000 timesources on the a=0.09 fm ensemble. For D and K semileptonic decay, we plan to bring our analyzed data set to 19,000 timesources on the a=0.12 fm ensemble, and to 4,000 timesources on the 0.09 fm ensemble.
Selected References
 Neutral Bmeson mixing from threeflavor lattice QCD: Determination of the SU(3)breaking ratio ξ, Α. Bazavov et al., Phys.Rev. D86 (2012) 034503,
arXiv:1205.7013.
 Bs to Ds over B to D Semileptonic FormFactor Ratios and Their Application to BR(Bs to muons). Jon A. Bailey et al., Phys.Rev. D85 (2012) 114502, arXiv:1202.6346.
 B and D meson decay constants from threeflavor lattice QCD,
A. Bazavov et al., Phys.Rev. D85 (2012) 114506, arXiv:1112.3051.
 The B > πlν semileptonic form factor from threeflavor lattice QCD: A modelindependent determination of V(ub).
J. Bailey et al. FERMILABPUB08541T, Nov 2008, arXiv:0811.3640 [heplat], Phys.Rev. D79 (2009) 054507.
 The AntiB > D* l antiν form factor at zero recoil from threeflavor lattice QCD: A Model independent determination of V(cb),
C. Bernard et al. FERMILABPUB08316T,
Phys.Rev. D79 (2009) 014506, arXiv:0808.2519 [heplat].
 Charmed meson decay constants in threeflavor lattice QCD.
C. Aubin et al. FERMILABPUB05257T, Jun 2005. 4pp.
Published in Phys.Rev.Lett.95:122002,2005
 Mass of the B(c) meson in threeflavor lattice QCD.
By HPQCD Collaboration and Fermilab Lattice Collaboration and UKQCD Collaboration (Ian F. Allison et al.). FERMILABPUB04349T, Nov 2004. 4pp.
Published in Phys.Rev.Lett.94:172001,2005
 Semileptonic decays of D mesons in threeflavor lattice QCD.
By Fermilab Lattice Collaboration and MILC Collaboration and HPQCD Collaboration (C. Aubin et al.). FERMILABPUB04195T, Aug 2004. 4pp.
Published in Phys.Rev.Lett.94:011601,2005
 High precision lattice QCD confronts experiment.
C.T.H. Davies et al. FERMILABPUB03297T, Apr 2003. 4pp.
Published in Phys.Rev.Lett.92:022001,2004
ePrint Archive: heplat/0304004.
