arXiv subjects

Miguel A. Sanchis-Lozano

Publications and source records attributed to Miguel A. Sanchis-Lozano.

10 recordsLinked to original sources

arXiv2006

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).

hep-ph↗

arXiv2004

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 and $η_b$ states might shift the mass levels of the latter, thereby changing the values of the $m_{Υ(nS)}-m_{η_b(nS)}$ 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.

hep-ph↗

arXiv2002

Appell Functions and the Scalar One-Loop Three-point Integrals in Feynman Diagrams

The scalar three-point function appearing in one-loop Feynman diagrams is compactly expressed in terms of a generalized hypergeometric function of two variables. Use is made of the connection between such Appell function and dilogarithms coming from a previous investigation. Special cases are obtained for particular values of internal masses and external momenta.

hep-ph↗

arXiv1998

Generalized Hypergeometric Functions and the Evaluation of Scalar One-loop Integrals in Feynman Diagrams

Present and future high-precision tests of the Standard Model and beyond for the fundamental constituents and interactions in Nature are demanding complex perturbative calculations involving multi-leg and multi-loop Feynman diagrams. Currently, large effort is devoted to the search for closed expressions of loop integrals, written whenever possible in terms of known - often hypergeometric-type - functions. In this work, the scalar three-point function is re-evaluated by means of generalized hypergeometric functions of two variables. Finally, use is made of the connection between such Appell functions and dilogarithms coming from a previous investigation, to recover well-known results.

hep-ph↗

arXiv1998

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 $J/ψ$'s as a background for the B physics programme at LHC experiments.

hep-ph↗

arXiv1997

Heavy Quark Effective Fields as Operator-valued Distributions

We look at effective fields defined in the heavy-quark effective theory as operator-valued generalized functions on Minkowski space-time to be averaged with physically suitable smoothing functions (Gaussians of typical width the hadronic size) leading to operator-valued distributions in Hilbert space. One-heavy-quark states are thus represented by normalizable wave packets displaying a particle-like behaviour at the characteristic hadronic time $Λ_{QCD}^{-1}$. We examine some consequences relative to the average kinetic energy of heavy quarks in hadrons to avoid inconsistences within this formalism.

hep-ph↗

arXiv1997

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

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 code for a fast simulation with PYTHIA based on the colour-octet model.

hep-ph↗

arXiv1997

J/psi Production at the LHC

We firstly re-examine hadroproduction of prompt J/psi's at the Fermilab Tevatron finding that those colour-octet matrix elements presented in literature are systematically overestimated due to the overlooking of the effective primordial transverse momentum of partons (i.e. dynamically generated via initial-state radiation). We estimate the size of these effects using different parton distribution functions in a Monte Carlo framework. Finally, we extrapolate up to LHC energies making a prediction on the expected pt differential cross-section for charmonium.

hep-ph↗

arXiv1996

A Comment on Heavy Quark Effective Fields

Effective fields defined in the heavy-quark effective theory to describe heavy quarks in heavy-light hadrons are examined in some detail in the standard formulation of a quantum field theory.

hep-ph↗

arXiv1996

J/psi Production at the LHC

We firstly examine hadroproduction of prompt J/psi's at the Fermilab Tevatron in a Monte Carlo Framework by means of the event generator PYTHIA 5.7 in which those colour-octet matrix elements processes relevant for charmonium production have been implemented accordingly. We find that colour-octet matrix elements presented in literature from p-pbar collider data are systematically overestimated due to overlooking of the effective primordial transverse momentum of partons (i.e. including higher-order QCD effects). We estimate the size of these effects using different parton distribution functions. Finally, after normalization to Tevatron data, we extrapolate up to LHC energies making a prediction on the expected pt differential cross-section for charmonium.

hep-ph↗