449 research outputs found
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
Large tan(beta) effects in flavour physics
After a short introduction to the SUSY flavour problem, we focus the
attention on the MSSM with MFV and large . The theoretical
motivations and the general features of this scenario are briefly reviewed. The
possible signatures in low-energy flavour-violating observables are discussed,
with particular attention to the role played by \BR(P\to\ell\nu),
\BR(B_{s,d}\to \ell^+\ell^-) and \BR(\mu\to e \gamma)Comment: Submitted for the SUSY07 proceedings, 8 pages, 6 figure
Exclusive Charmless 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 and form factor.
Employing the LCSR technique, the 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
The last two years have seen an impressive improvement in the determination
of , especially from inclusive decays. The error on
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 (DGE, etc.). The prospects of improving are
discussed, addressing issues of weak annihilation, implications of leptonic B
decays, and determination of 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
Testing QCD Sum Rules on the Light-Cone in D->(pi,K) l nu Decays
We compare the predictions for the form factors f_+^{D->pi,K}(0) from QCD sum
rules on the light-cone with recent experimental results. We find
f_+^{D->pi}(0) = 0.63\pm 0.11, f_+^{D->K}(0) = 0.75\pm 0.12 and
f_+^{D->pi}(0)/f_+^{D->K}(0)= 0.84\pm 0.04 in very good agreement with
experiment. Although the uncertainties of the form factors themselves are
larger than the current experimental errors and difficult to reduce, their
ratio is determined much more accurately and with an accuracy that matches that
of experiment.Comment: 12 page
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 () has the standard model like couplings to the
gauge bosons. We take into account the one-loop correction to the
coupling as well as additional one-loop diagrams due to charged Higgs bosons to
the 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 coupling measurement at
the photon collider.Comment: 16 pages, 8 figures; added Appendix with a figur
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