Precision lattice QCD calculations and predictions of fundamental physics in heavy quark systems

I describe the recent success in performing accurate calculations of the effects of the strong force on particles containing bottom and charm quarks. Since quarks are never seen in isolation, and so cannot be studied directly, numerical simulations are key to understanding the properties of these particles and extracting information about the quarks. The results have direct impact on the worldwide experimental programme that is aiming to determine the parameters of the Standard Model of particle physics precisely and thereby uncover or constrain the possibilities for physics beyond the Standard Model. The numerical simulation of the strong force is a huge computational task and the recent success is the result of international collaboration in developing techniques that are fast enough to do the calculations on powerful supercomputers.Comment: Invited talk at SCIDAC 2006, Denver, June 2006. 15 page

Exclusive Charmless BB Decays in QCD

The problem of hadronic input in charmless nonleptonic B decays is discussed. QCD sum rules and their light-cone versions (LCSR) provide an important part of this input, such as the decay constant $f_B$ and $B\to \pi$ form factor. Employing the LCSR technique, the $B\to \pi\pi$ hadronic matrix elements with emission, penguin and annihilation topologies are calculated, with no evidence for large nonfactorizable effects and/or strong phases.Comment: 6 pages, Invited talk at the First Workshop on Theory, Phenomenology and Experiments in Heavy Flavour Physics, Anacapri, Italy, May 29-31 200

Precision Determination of ∣Vub∣|V_{ub}|

The last two years have seen an impressive improvement in the determination of $|V_{ub}|$, especially from inclusive decays. The error on $|V_{ub}|$ measured with inclusive decays was reduced from 18% (PDG 2004) to 8% (PDG 2006). This progress is a result of combined experimental and theoretical efforts. In this talk, the theoretical framework (BLNP) that enabled such progress is reviewed, as well as other approaches to an inclusive determination of $|V_{ub}|$ (DGE, $M_X-q^2$ etc.). The prospects of improving $|V_{ub}|$ are discussed, addressing issues of weak annihilation, implications of leptonic B decays, and determination of $|V_{ub}|$ with exclusive decays.Comment: Invited talk at International Conference on B-Physics at Hadron Machines (Beauty 2006), Oxford, England, 25-29 Sep 200

Revisiting Signature of Minimal Gauge Mediation

We revisit phenomenology of the minimal gauge-mediated model. This model is motivated from the SUSY CP and flavor problems. A specific feature of this model is that \tan\beta is naturally large, since the B term in the Higgs potential is zero at the messenger scale. This leads to significant SUSY contributions to various low-energy observables. We evaluate the anomalous magnetic moment of the muon and the branching ratio of \bar{B}\to X_s\gamma taking account of recent theoretical and experimental developments. We find that the current experimental data prefer a low messenger scale (\sim 100 TeV) and gluino mass around 1 TeV. We also calculate the branching ratios of \bar{B}\to X_s l^+l^-, B_s\to \mu^+\mu^-, and B^-\to \tau^- \bar{\nu}, and show that these observables are strongly correlated with each other in this model.Comment: 20 pages, 16 figure

Demise of CKM & its aftermath

Using firmly established experimental inputs such as epsilon_K, Delta M_d, Delta M_s, BR(B -> tau nu), gamma, V_cb along with corresponding lattice matrix elements which have been well studied and are in full QCD such as B_K, SU3 breaking ratio xi, B_Bs and in particular without using V_ub or the pseudoscalar decay constants f_Bd or f_Bs from the latice, we show that the CKM-paradigm now appears to be in serious conflict with the data. Specifically the SM predicted value of sin(2 beta) seems too high compared to direct experimental measured value by over 3 sigma. Furthermore, our studiy shows that new physics predominantly effects B-mixings and B_d -> psi K_s, and not primarily in kaon-mixing or in B -> tau nu. Model independent operator analysis suggests the scale of underlying new physics, accompanied by a BSM CP-odd phase, responsible for breaking of the SM is less than a few TeV, possibly as low as a few hundred GeV. Two possible BSM scenarios, namely warped extra-dimensions and SM with a 4th generation, are briefly discussed. Generic predictions of warped flavor models are briefly discussed. While SM with 4th generation (SM4) is a very simple way to account for the observed anomalies, SM4 is also well motivated due to its potential role in dynamical electrweak symmetery breaking via condensation of heavy quarks and in barygenesis.Comment: 18 pages, 8 figures, talk given at Moriond EW 2011, corrected typos in Fig.6 label

Higgs boson pair production at a photon-photon collision in the two Higgs doublet model

We calculate the cross section of Higgs boson pair production at a photon collider in the two Higgs doublet model. We focus on the scenario in which the lightest CP even Higgs boson ($h$) has the standard model like couplings to the gauge bosons. We take into account the one-loop correction to the $hhh$ coupling as well as additional one-loop diagrams due to charged Higgs bosons to the $\gamma\gamma\to hh$ helicity amplitudes. It is found that the full cross section can be enhanced by both these effects to a considerable level. We discuss the impact of these corrections on the $hhh$ coupling measurement at the photon collider.Comment: 16 pages, 8 figures; added Appendix with a figur

Decay constants of charm and beauty pseudoscalar heavy-light mesons on fine lattices

We compute decay constants of heavy-light mesons in quenched lattice QCD with a lattice spacing of a ~ 0.04 fm using non-perturbatively O(a) improved Wilson fermions and O(a) improved currents. We obtain f_{D_s} = 220(6)(5)(11) MeV, f_D = 206(6)(3)(22) MeV, f_{B_s} = 205(7)(26)(17) MeV and f_B = 190(8)(23)(25) MeV, using the Sommer parameter r_0 = 0.5 fm to set the scale. The first error is statistical, the second systematic and the third from assuming a +-10% uncertainty in the experimental value of r_0. A detailed discussion is given in the text. We also present results for the meson decay constants f_K and f_\pi and the \rho meson mass.Comment: 13 pages, 7 figures. Replaced version contains analysis in terms of improved quark masses instead of bare quark masses, result for f_B changed by 1 MeV. Several typos corrected, in particular error bars in table 4. Version accepted in PL

Soft Photon Problem in Leptonic B-decays

We point out at the peculiarity of B --> mu nu decay, namely the enhancement of the soft photon events which originate from the structure dependent part of the B --> mu nu gamma amplitude. This may be a dominant source of systematic uncertainty and compromise the projected experimental uncertainty on Gamma(B --> mu nu). We show that the effect of these soft photons can be controlled if the experimental cut on identification of soft photons is lowered and especially if the better resolution in identifying the momentum of muon emerging from B --> mu nu, is made. A lattice QCD computation of the relevant form factors would be highly helpful for a better numerical control over the structure dependent soft photon emission.Comment: 16 pages, 3 figure

Light Heavy MSSM Higgs Bosons at Large tan_beta

The region of MSSM Higgs parameter space currently excluded by the CDF Collaboration, based on an analysis of ~1 fb^-1 of integrated luminosity, is less than the expected sensitivity. We analyze the potential implications of the persistence of this discrepancy within the MSSM, assuming that the soft supersymmetry-breaking contributions to scalar masses are universal, apart from those to the Higgs masses (the NUHM model). We find that a light heavy MSSM Higgs signal in the unexcluded part of the sensitive region could indeed be accommodated in this simple model, even after taking into account other constraints from cold dark matter, electroweak precision observables and B physics observables. In this case the NUHM suggests that supersymmetric signatures should also be detectable in the near future in some other measurements such as BR(B_s -> mu+ mu-), BR(b -> s gamma) and (g-2)_mu, and M_h would have to be very close to the LEP exclusion limit. In addition, the dark matter candidate associated with this model should be on the verge of detection in direct detection experiments.Comment: 14 pages, 2 figure

Possible evidence for the breakdown of the CKM-paradigm of CP-violation

Using primarily experimental inputs for S(B -> psi Ks), Delta M_Bs, Delta M_Bd, BR(B -> tau nu) and epsilon_K along with necessary inputs from the lattice, we find that the measured value of sin(2 beta) is smaller than expectations of the Standard Model by as much as 3.3 sigma, and also that the measured value of the BR(B -> tau nu) seems to be less than the predicted value by about 2.8 sigma. However, through a critical study we show that most likely the dominant source of these deviations is in B_d(s) mixings and in sin(2 beta) and less so in B -> tau nu, and also that the bulk of the problem persists even if input from epsilon_K is not used. The fact that kaon mixing and epsilon_K are not the dominant source of the deviation from the Standard Model has the very important consequence that model independent considerations imply that the scale of the relevant new CP-violating physics is below O(2 TeV), thus suggesting that direct signals of the new particle(s) may well be accessible in collider experiments at the LHC and perhaps even at the Tevatron.Comment: 6 pages, 8 figures. Added another fit and some more discussion showing that BR(B->tau nu) comes out in good agreement with predictions of the SM if the measured value of sin2beta is not used as an input. References adde