arXiv subjects

Nicola Di Bartolomeo

Publications and source records attributed to Nicola Di Bartolomeo.

2 recordsLinked to original sources

arXiv1997

Four-Fermion Effective Interactions and Recent Data at HERA

We discuss the possibility of explaining the excess in the cross section at high-Q^2 recently found at HERA in terms of four-fermion effective interactions. To avoid the constraints from low-energy data, we select three special cases in which the contact interaction is a product of vector-vector, axial-axial and vector-axial currents. For these a satisfactory fit of HERA data is possible, while keeping agreement with LEPII and CDF data, for an interaction scale $Λ=3.5$ TeV. As the statistics of the experiments improves-and if the effect persists-it will be soon possible to discriminate between such contact terms and the alternative explanation in terms of leptoquark exchange.

hep-ph↗

arXiv1995

Heavy meson hyperfine splitting: a complete $1/m_Q$ calculation

We compute the chiral corrections to the hyperfine splittings $Δ_D=(m_{D^*_s}-m_{D_s})-(m_{D^{*+}}-m_{D^+})$ and $Δ_B=(m_{B^*_s}-m_{B_s})-(m_{B^{*0}}-m_{B^0})$ arising from one-loop chiral corrections, working in a framework of an effective chiral lagrangian incorporating chiral, heavy flavour and spin symmetric terms and first order breaking terms. Among these terms, those responsible for the spin-breaking difference between the couplings $g_{P^* P^* π}$ and $g_{P^* P π}$ are evaluated in the QCD sum rules approach. Their contribution to $Δ_D$ and to $Δ_B$ appears to cancel previously estimated large chiral effects, giving an estimate in agreement with the experimental data.

hep-ph↗