Gustavo Burdman

Union of chiral and heavy quark symmetries

Abstract We describe the chiral symmetric couplings of pions to heavy mesons (B or D), valid in the portion of phase space where the pions have low momentum. In order to include consistently all low energy excitations, the vector mesons (B ∗ or D ∗ ) must appear explicitly in the effective lagrangian. The result is then invariant under both the chiral and heavy quark symmetries. We include matrix elements relevant for various weak decays.

Colorless top partners, a 125 GeV Higgs boson, and the limits on naturalness

Theories of physics beyond the Standard Model that address the hierarchy problem generally involve top partners, new particles that cancel the quadratic divergences associated with the Yukawa coupling of the Higgs to the top quark. With extensions of the Standard Model that involve new colored particles coming under strain from collider searches, scenarios in which the top partners carry no charge under the strong interactions have become increasingly compelling. Although elusive for direct searches, these theories predict modified couplings of the Higgs boson to the Standard Model particles. This results in corrections to the Higgs production and decay rates that can be detected at the Large Hadron Collider (LHC) provided the top partners are sufficiently light, and the theory correspondingly natural. In this paper we consider three theories that address the little hierarchy problem and involve colorless top partners, specifically the Mirror Twin Higgs, Folded Supersymmetry, and the Quirky Little Higgs. For each model we investigate the current and future bounds on the top partners, and the corresponding limits on naturalness, that can be obtained from the Higgs program at the LHC. We conclude that the LHC will not be able to strongly disfavor naturalness, with mild tuning at the level of about one part in ten remaining allowed even with 3000 fb

Reliable predictions in exclusive rare B decays

^{-1}

Is the LHC observing the pseudoscalar state of a two-Higgs-doublet model?

of data at 14 TeV.

Anomalous couplings of the third generation in rare B decays

The little Higgs model provides an alternative to traditional candidates for new physics at the TeV scale. The new heavy gauge bosons predicted by this model should be observable at the Large Hadron Collider (LHC). We discuss how the LHC experiments could test the little Higgs model by studying the production and decay of these particles.

Neutrino telescopes as a direct probe of supersymmetry breaking

Abstract We discuss the relations between form factors for B → K ∗ γ and B→ ϱ e ν which follow from static heavy quark symmetry methods plus SU(3). We discuss carefully the hard perturbative QCD corrections which could invalidate these results and find that the dominant perturbative corrections are ones which respect the static symmetry predictions, and in addition that the perturbative corrections are small compared to soft contributions. We show that there is a special kinematic point in B→ ϱ e ν that involves the same combination of form factors as in B → K ∗ γ , thus allowing a prediction of the ratio of rates which is largely free from hadronic uncertainties.

New Strongly Coupled Sector at the Tevatron and the LHC

We address standard model predictions for flavor-changing radiative transitions of the pseudoscalar charm mesons. Short-distance contributions in {ital D} radiative transitions are contrasted with those in {ital B} decays. A full analysis is presented of the {ital c}{r_arrow}{ital u}+{gamma} electromagnetic penguin amplitude with QCD radiative corrections included. Given the importance of long-range effects for the charm sector, special attention is paid to such contributions as the vector dominance and pole amplitudes. A number of two-body final states in exclusive charm radiative decays is considered and the corresponding branching ratio predictions are given.

Signal for an Extra-Dimensional Model of Flavor at the Large Hadron Collider

The ATLAS and CMS collaborations have recently shown data suggesting the presence of a Higgs boson in the vicinity of 125 GeV. We show that a two-Higgs-doublet model spectrum, with the pseudoscalar state being the lightest, could be responsible for the diphoton signal events. In this model, the other scalars are considerably heavier and are not excluded by the current LHC data. If this assumption is correct, future LHC data should show a strengthening of the �� signal, while the signals in the ZZ ð�Þ ! 4‘ and WW ð�Þ ! 2‘2� channels should diminish and eventually disappear, due to the absence of diboson tree-level couplings of the CP-odd state. The heavier CP-even neutral scalars can now decay into channels involving the CP-odd light scalar which, together with their larger masses, allow them to avoid the existing bounds on Higgs searches. We suggest additional signals to confirm this scenario at the LHC, in the decay channels of the heavier scalars into AA and AZ. Finally, this inverted two-Higgs-doublet spectrum is characteristic in models where fermion condensation leads to electroweak symmetry breaking. We show that in these theories it is possible to obtain the observed diphoton signal at or somewhat above the prediction for the standard model Higgs for the typical values of the parameters predicted.