Zoltan Ligeti

Lessons from CLEO and FOCUS measurements of D0–D0 mixing parameters

Abstract If the true values of the D 0 – D 0 mixing parameters lie within the one sigma ranges of recent measurements, then there is strong evidence for a large width difference, y≳0.01, and large SU(3) breaking effects in strong phases, δ≳π/4. These constraints are model independent, and would become stronger if |M12/Γ12|≪1 in the D 0 – D 0 system. The interesting fact that the FOCUS result cannot be explained by a large mass difference is not trivial and depends on the small D 0 / D 0 production asymmetry in FOCUS and the bounds on CP violating effects from CLEO. The large value of δ might help explain why y∼sin2θc.

A model independent determination of |Vub|

Abstract It is shown that measuring the lepton invariant mass spectrum in inclusive semileptonic B →X u l ν decay yields a model independent determination of |Vub|. Unlike the lepton energy and hadronic invariant mass spectra, nonperturbative effects are only important in the resonance region, and play a parametrically suppressed role when dΓ/dq2 is integrated over q2>(mB−mD)2, which is required to eliminate the charm background. Perturbative and nonperturbative corrections are presented to order αs2β0 and ΛQCD2/mb2, and the ΛQCD3/mb3 corrections are used to estimate the uncertainty in our results. The utility of the B →X s l + l − decay rate above the ψ(2S) resonance is discussed.

HAMMER: Reweighting tool for simulated data samples

Modern flavour physics experiments, such as Belle II or LHCb, require large samples of generated Monte Carlo events. Monte Carlo events often are processed in a sophisticated chain that includes a simulation of the detector response. The generation and reconstruction of large samples is resource-intensive and in principle would need to be repeated if e.g. parameters responsible for the underlying models change due to new measurements or new insights. To avoid having to regenerate large samples, we work on a tool, The Helicity Amplitude Module for Matrix Element Reweighting (HAMMER), which allows one to easily reweight existing events in the context of semileptonic

Determining |Vub| from the B̄→Xulν̄ dilepton invariant mass spectrum

b \to q \, \ell \, \bar \nu_\ell

More Flavor SU(3) Tests for New Physics in B Decays

analyses to new model parameters or new physics scenarios.

Testing the dynamics of B -> pi pi and constraints on alpha - eScholarship

The invariant mass spectrum of the lepton pair in inclusive semileptonic B→Xulν decay yields a model independent determination of |Vub| [1]. Unlike the lepton energy and hadronic invariant mass spectra, nonperturbative effects are only important in the resonance region, and play a parametrically suppressed role when dΓ/dq2 is integrated over q2>(mB−mD)2, which is required to eliminate the B→Xclν background. We discuss these backgrounds for q2 slightly below (mB−mD)2, and point out that instead of q2>(mB−mD)2=11.6 GeV2, the cut can be lowered to q2≳10.5 GeV2. This is important experimentally, particularly when effects of a finite neutrino reconstruction resolution are included.