Miguel Angel Sanchis-Lozano

Weak decays of doubly heavy hadrons

We explore the application and usefulness of the heavy quark symmetry to describe the weak decays of hadrons (mesons and baryons) containing two heavy quarks. Firstly, we address the internal dynamics of a heavy-heavy bound system with the help of estimates based on potential models, showing an approximate spin symmetry in the preasymptotic quark mass region including charmonium, bottonium and Bc meson states. However, no asymptotic spin symmetry should hold in the infinite quark mass limit in contrast to singly heavy hadrons. Predictions on semileptonic and two-body nonleptonic decays of Bc mesons are shown. Furthermore, the stemming flavor and spin symmetries from the interaction between the heavy and light components in hadrons (combining in a “superflavor” symmetry) permit their classification in meson-type supermultiplets containing singly heavy mesons together with doubly heavy baryons, and baryon-type supermultiplets containing singly heavy baryons together with some exotic doubly heavy multiquark states (diquonia). Exploiting their well-defined transformation properties under the superflavor symmetry group, we get predictions on the widths for some semileptonic and two-body nonleptonic decays of baryons containing both b and c quarks.

Charmonia production in hadron colliders and the extraction of colour-octet matrix elements☆

Abstract We present the results of our analysis on charmonia ( J / ψ and ψ ′) hadroproduction taking into account higher-order QCD effects induced by initial-state radiation in a Monte Carlo framework, with the colour-octet mechanism implemented in the event generation. We find that those colour-octet matrix elements extracted so far from Fermilab Tevatron data for both J / ψ and ψ ′ production have to be lowered significantly. We finally make predictions for charmonia production at the LHC, presenting a simple code for a fast simulation with PYTHIA based on the colour-octet model.

On the search for weak decays of heavy quarkonium in dedicated heavy-quark factories

The possibility of detecting weak decays of charmonium and bottomonium in dedicated heavy-quark factories is examined. First, semi-leptonic and two-body non-leptonic decays of heavy quarkonium are analyzed theoretically on the basis of the spin symmetry of heavy hadrons. Finally, possible procedures for conducting the experimental search are proposed and the requested detector requirements are discussed.

Searching for new physics in bottomonium decays

Heavy quarkonium decays can be used to search for New Physics beyond the Standard Model. In particular, a light Higgs boson could induce a slight (but observable) lepton universality breaking in Upsilon decays. In fact, current experimental data from CLEO presented in this Conference seem to point out to this direction within experimental accuracy. Moreover, LEP constraints on a light Higgs mass can be evaded by different models (like MSSM with a CPV Higgs sector) as shown in this Conference. We also consider spectroscopic consequences stemming from a possible mixing between Higgs and bottomonium states leading to discrepancies with the SM expectations (e.g. hyperfine splittings).

Hints of new physics in bottomonium decays and spectroscopy

A non-standard light CP-odd Higgs boson could induce a slight (but observable) lepton universality breakdown in Upsilon leptonic decays. Moreover, the mixing between such a pseudoscalar Higgs boson and ηb states might shift the mass levels of the latter, thereby changing the values of the m ϒ ( n S ) − m η b ( n S ) splittings predicted in the standard model. Besides, also the η b width could be broader than expected, with potentially negative consequences for its discovery in both e+e− and hadron colliders.

Semileptonic decays of baryons containing two heavy quarks

Abstract Semileptonic weak decays of doubly heavy baryons are analyzed and compared to the analogous decays of heavy quarkonia, showing similar underlying dynamics at low recoil.

Extended HQEFT Lagrangian and currents

Abstract From the tree-level heavy quark effective Lagrangian keeping particle-antiparticle mixed sectors we derive the vector current coupling to a hard gluonic field allowing for heavy quark-antiquark pair annihilation and creation.

Results from Bottomonia Production at the Tevatron and Prospects for the LHC

We extend our previous analysis on inclusive heavy quarkonia hadroproduction to the whole �(nS) (n=1,2,3) resonance family. We use a Monte Carlo framework with the colour-octet mechanism implemented in the PYTHIA event generator. We include in our study higher order QCD effects such as initial-state emission of gluons and Altarelli-Parisi evolution of final-state gluons. We extract some NRQCD colour-octet matrix elements relevant for �(nS) (n=1,2,3) hadroproduction from CDF data at the Fermilab Tevatron. Then we extrapolate to LHC energies to predict prompt bottomonia production rates. Finally, we examine the prospect to probe the gluon density in protons from heavy quarkonia inclusive hadroproduction at high transverse momentum and its feasibility in LHC general-purpose experiments.

Charmonium Production at Tevatron, HERA and LHC*

Charmonia hadro- and photo-production are analyzed in the framework of the color-octet model taking into account higher-order effects induced by initial-state radiation of gluons. We argue that color-octet matrix elements obtained from Tevatron data might be reconciled with those extracted from HERA data on inelastic J/ψ photoproduction. Finally we estimate cross sections for events with muons from prompt J/ψs as a background for the B physics programme at LHC experiments.

Searching for Bc mesons in the ATLAS experiment at LHC

We discuss the feasibility of the observation of the signal from Bc mesons in the ATLAS experiment at the LHC. In particular, we address the decay mode Bc→J/ψπ followed by the leptonic decay J/ψ→μ+μ−, which should permit an accurate measurement of the Bc mass. We performed a Monte Carlo study of the signal and background concluding that a precision of ≈ 1 MeV for the Bc mass could be achieved after one year of running at “low” luminosity. The semileptonic decay Bc→J/ψ μ+vμ is also considered for a possible extraction of |Vcb|.