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Gennaro Corcella

Publications and source records attributed to Gennaro Corcella.

At least 55 records · Page 3Linked to original sources
arXiv2007

Charm-quark fragmentation with an effective coupling constant

We use a recently proposed non-perturbative model, based on an effective strong coupling constant and free from tunable parameters, to study c-flavoured hadron production in e+e- annihilation. Charm-quark production is described in the framework of perturbative fragmentation functions, with NLO coefficient functions, NLL non-singlet DGLAP evolution and NNLL large-x resummation. We model hadronization effects by means of the effective coupling constant in the NNLO approximation and compare our results with experimental data taken at the Z0 pole and at the Upsilon(4S) resonance. We find that, within the experimental and theoretical uncertainties, our model is able to give a reasonable description of D*+-meson spectra from ALEPH for x<1-Lambda/m_c. More serious discrepancies are instead present when comparing with D and D^* data from BELLE and CLEO in x-space. Within the errors, our model is nonetheless capable of reproducing the first ten Mellin moments of all considered data sets. However, the fairly large theoretical uncertainties call for a full NNLO/NNLL analysis.

hep-ph↗
arXiv2007

Modelling non-perturbative corrections to bottom-quark fragmentation

We describe B-hadron production in e+e- annihilation at the Z pole by means of a model including non-perturbative corrections to b-quark fragmentation as originating, via multiple soft emissions, from an effective QCD coupling constant, which does not exhibit the Landau pole any longer and includes absorbitive effects due to parton branching. We work in the framework of perturbative fragmentation functions at NLO, with NLL DGLAP evolution and NNLL large-x resummation in both coefficient function and initial condition of the perturbative fragmentation function. We include hadronization corrections via the effective coupling constant in the NNLO approximation and do not add any further non-perturbative fragmentation function. As part of our model, we perform the Mellin transforms of our resummed expressions exactly. We present results on the energy distribution of b-flavoured hadrons, which we compare with LEP and SLD data, in both x- and N-spaces. We find that, within the theoretical uncertainties on our calculation, our model is able to reasonably reproduce the data at x<0.92 and the first five moments of the B cross section.

hep-ph↗
arXiv2006

Angular ordering and parton showers for non-global QCD observables

We study the mismatch between a full calculation of non-global single-logarithms in the large-N_c limit and an approximation based on free azimuthal averaging, and the consequent angular-ordered pattern of soft gluon radiation in QCD. We compare the results obtained in either case to those obtained from the parton showers in the Monte Carlo event generators HERWIG and PYTHIA, with the aim of assessing the accuracy of the parton showers with regard to such observables where angular ordering is merely an approximation even at leading-logarithmic accuracy and which are commonly employed for the tuning of event generators to data.

hep-ph↗
arXiv2006

B-hadron production in top quark decay

We present the energy distribution of b-flavoured hadrons in top quark decay using the PYTHIA and HERWIG event generators, which we tune to LEP and SLD data. We find that fitting the string and cluster models is essential to reproduce the e+e- data and to reliably predict B-hadron production in top decay. We also compare the PYTHIA and HERWIG results with the ones yielded by resummed calculations based on the fragmentation function formalism.

hep-ph↗
arXiv2005

Bottom-quark fragmentation: comparing results from tuned event generators and resummed calculations

We study bottom-quark fragmentation in e+e- annihilation, top and Higgs decay H -> b bbar, using Monte Carlo event generators, as well as calculations, based on the formalism of perturbative fragmentation functions, which resum soft- and collinear-radiation effects in the next-to-leading logarithmic approximation. We consider the PYTHIA and HERWIG generators, and implement matrix-element corrections to the parton shower simulation of the H -> b bbar process in HERWIG. We tune the Kartvelishvili, string and cluster models to B-hadron data from LEP and SLD, and present results in both x_B and moment spaces. The B-hadron spectra yielded by HERWIG, PYTHIA and resummed calculations show small discrepancies, which are due to the different approaches and models employed and to the quality of the fits to the e+e- data.

hep-ph↗
arXiv2005

Soft-gluon resummation effects on parton distributions

We gauge the impact of soft-gluon resummation on quark distributions by performing a simple fit of Deep Inelastic Scattering structure function data using next-to-leading order (NLO) and next-to-leading-logarithmic (NLL)-resummed coefficient functions. We make use of NuTeV charged-current data, as well as New Muon Collaboration (NMC) and Bologna-CERN-Dubna-Munich-Saclay (BCDMS) neutral-current results, which probe large values of x. Our results suggest that the inclusion of resummation effects in global fits of parton distributions is both feasible and desirable, in order to achieve at large x the accuracy goals of the LHC physics program.

hep-ph↗
arXiv2005

Heavy flavours: theory summary

I summarize the theory talks given in the Heavy Flavours Working Group. In particular, I discuss heavy-flavour parton distribution functions, threshold resummation for heavy-quark production, progress in fragmentation functions, quarkonium production, heavy-meson hadroproduction.

hep-ph↗
arXiv2005

Impact of large-x resummation on parton distribution functions

We investigate the effect of large-x resummation on parton distributions by performing a fit of Deep Inelastic Scattering data from the NuTeV, BCDMS and NMC collaborations, using NLO and NLL soft-resummed coefficient functions. Our results show that soft resummation has a visible impact on quark densities at large x. Resummed parton fits would therefore be needed whenever high precision is required for cross sections evaluated near partonic threshold.

hep-ph↗
arXiv2005

Progress in bottom-quark fragmentation

I review recent progress on bottom-quark fragmentation in e+e- annihilation, top-quark decay and H -> b bbar processes. I discuss the implementation of collinear and soft resummation, and the inclusion of non-perturbative information taken from LEP and SLD data.

hep-ph↗
arXiv2005

Fragmentation in H->b bbar Processes

I study bottom quark fragmentation in the Standard Model Higgs decay H->b bbar, within the framework of perturbative fragmentation functions. I resum large collinear logarithms ln(m_H^2/m_b^2) in the next-to-leading logarithmic (NLL) approximation, using the DGLAP evolution equations. Soft contributions to the MSbar coefficient function and to the initial condition of the perturbative fragmentation function are resummed to NLL accuracy as well. The implementation of collinear and soft resummation has a relevant impact on the b energy spectrum, which exhibits a milder dependence on factorization and renormalization scales and on the Higgs mass. I present some predictions on the energy distribution of b-flavoured hadrons in Higgs decay, making use of data from LEP and SLD experiments to fit a few hadronization models. I also compare the phenomenological results yielded by a few processes recently provided with NLL collinear and soft resummations.

hep-ph↗
arXiv2004

Fragmentation of bottom quarks in top quark decay

We review the main aspects of the fragmentation of bottom quarks in top quark decay. The NLO b-quark energy spectrum presents large mass logarithms ln(m_t^2/m_b^2), which can be resummed by the use of the approach of perturbative fragmentation functions. Large soft contributions in both coefficient function and initial condition of the perturbative fragmentation function have been resummed as well. Results on the energy distribution of b quarks and b-flavoured hadrons are finally presented in both x and moment spaces.

hep-ph↗
arXiv2004

Matrix-Element Corrections to Parton Shower Simulations for Higgs Hadroproduction

We implement matrix-element corrections to HERWIG parton shower simulations for Standard Model Higgs boson production at hadron colliders. We study the Higgs transverse momentum distribution and compare different versions of HERWIG and resummed calculations. The HERWIG results exhibit a remarkable improvement as many more events are generated at large transverse momentum after the inclusion of matrix-element corrections.

hep-ph↗
arXiv2004

Matrix-element corrections to gg/qqbar -> Higgs in HERWIG

We describe the HERWIG implementation of real matrix-element corrections to direct Higgs hadroproduction at Tevatron and Large Hadron Collider (LHC) and compare it to other approaches existing in literature and describing the transverse momentum distribution of the Higgs boson.

hep-ph↗
arXiv2003

Soft-Gluon Resummation for Heavy Quark Production in Charged-Current Deep Inelastic Scattering

We study soft-gluon radiation for heavy quark production in charged-current Deep Inelastic Scattering processes. We resum large-x contributions to the MSbar coefficient function to next-to-leading logarithmic accuracy and present results for charm quark structure functions for several values of the ratio m_c/Q. The effect of the resummation turns out to be visible, especially at small Q^2, and the results exhibit very little dependence on factorization and renormalization scales. The impact of our calculation on structure function measurements at NuTeV and HERA experiments is discussed.

hep-ph↗
arXiv2003

Bottom Quark Mass Determination from low-n Sum Rules

We study the uncertainties in the MSbar bottom quark mass determination using relativistic sum rules to O(alpha_S^2). We include charm mass effects and secondary b bbar production and treat the experimental continuum region more conservatively than previous analyses. The PDG treatment of the region between the resonances Upsilon (4S) and Upsilon (5S) is reconsidered. Our final result reads: m_b(m_b)=(4.20 \pm 0.09) GeV.

hep-ph↗
arXiv2003

Soft-Gluon Resummation for Bottom Fragmentation in Top Quark Decay

We study soft-gluon radiation in top quark decay within the framework of perturbative fragmentation functions. We present results for the b-quark energy distribution, accounting for soft-gluon resummation in both the MSbar coefficient function and in the initial condition of the perturbative fragmentation function. The results show remarkable improvement and the b-quark energy spectrum in top quark decay exhibits very little dependence on factorization and renormalization scales. We present some hadron-level results in both x_B and moment space by including non-perturbative information determined from e+e- data.

hep-ph↗
arXiv2001

Bottom Quark Fragmentation in Top Quark Decay

We study the fragmentation of the b quark in top decay in NLO QCD, within the framework of perturbative fragmentation, which allows one to resum large logarithms $\sim\log (m_t^2/m_b^2)$. We show the b-energy distribution, which we compare with the exact ${\cal O} (α_S)$ result for a massive b quark. We use data from $e^+e^-$ machines in order to describe the b-quark hadronization and make predictions for the energy spectrum of b-flavoured hadrons in top decay. We also investigate the effect of NLL soft-gluon resummation in the initial condition of the perturbative fragmentation function on parton- and hadron-level energy distributions.

hep-ph↗