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M. Cacciari

Publications and source records attributed to M. Cacciari.

At least 37 records · Page 2Linked to original sources
arXiv2004

Physics at the CLIC Multi-TeV Linear Collider

This report summarizes a study of the physics potential of the CLIC e+e- linear collider operating at centre-of-mass energies from 1 TeV to 5 TeV with luminosity of the order of 10^35 cm^-2 s^-1. First, the CLIC collider complex is surveyed, with emphasis on aspects related to its physics capabilities, particularly the luminosity and energy, and also possible polarization, γγand e-e- collisions. The next CLIC Test facility, CTF3, and its R&D programme are also reviewed. We then discuss aspects of experimentation at CLIC, including backgrounds and experimental conditions, and present a conceptual detector design used in the physics analyses, most of which use the nominal CLIC centre-of-mass energy of 3 TeV. CLIC contributions to Higgs physics could include completing the profile of a light Higgs boson by measuring rare decays and reconstructing the Higgs potential, or discovering one or more heavy Higgs bosons, or probing CP violation in the Higgs sector. Turning to physics beyond the Standard Model, CLIC might be able to complete the supersymmetric spectrum and make more precise measurements of sparticles detected previously at the LHC or a lower-energy linear e+e- collider: γγcollisions and polarization would be particularly useful for these tasks. CLIC would also have unique capabilities for probing other possible extensions of the Standard Model, such as theories with extra dimensions or new vector resonances, new contact interactions and models with strong WW scattering at high energies. In all the scenarios we have studied, CLIC would provide significant fundamental physics information beyond that available from the LHC and a lower-energy linear e+e- collider, as a result of its unique combination of high energy and experimental precision.

hep-ph↗
arXiv2004

QCD analysis of first b cross section data at 1.96 TeV

The first data on bottom quark production in p-pbar collisions at 1.96 TeV have recently been obtained by the CDF collaboration. These data probe the region of pt~0, providing a new invaluable input on the issue of the compatibility between next-to-leading-order (NLO) QCD and data. We reconsider the evaluation of the b cross section, in view of recent theoretical developments, and of the latest inputs on structure function fits. We show that the new CDF measurements are in good agreement with NLO QCD. If CDF preliminary data are confirmed, a long-standing discrepancy between NLO QCD predictions and hadron-collider data can be settled.

hep-ph↗
arXiv2002

The QCD/SM Working Group: Summary Report

This Report documents the results obtained by the Working Group on Quantum ChromoDynamics and the Standard Model for the Workshop ``Physics at TeV Colliders'', Les Houches, France, 21 May - 1 June 2001. The account of uncertainties in Parton Distribution Functions is reviewed. Progresses in the description of multiparton final states at Next-to-Leading Order and the extension of calculations for precision QCD observables beyond this order are summarized. Various issues concerning the relevance of resummation for observables at TeV colliders is examined. Improvements to algorithms of jet reconstruction are discussed and predictions for diphoton and photon pi-zero production at the LHC are made for kinematic variables of interest regarding searches for a Higgs boson decaying into two photons. Finally, several improvements implemented in Monte-Carlo event generators are documented.

hep-ph↗
arXiv2002

Is There a Significant Excess in Bottom Hadroproduction at the Tevatron?

We discuss the excess in the hadroproduction of B mesons at the Tevatron. We show that an accurate use of up-to-date information on the B fragmentation function reduces the observed excess to an acceptable level. Possible implications for experimental results reporting bottom quark cross sections, also showing an excess with respect to next-to-leading order theoretical predictions, are discussed.

hep-ph↗
arXiv2001

QCD radiative corrections to $γ^*γ^* \to$ hadrons at LEP2

In this talk we describe the order-$\as$ corrections to the total cross section and to jet rates in $γ^* γ^* \to$ hadrons for the process $\epem\to\epem +$ hadrons. We use a next-to-leading order general-purpose partonic Monte Carlo event generator that allows the computation of a rate differential in the produced leptons and hadrons. We compare our results with the experimental data for $\epem\to\epem +$ hadrons at LEP2.

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arXiv2001

Bottom Production

We review the prospects for bottom production physics at the LHC.

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arXiv2001

Soft-Gluon Resummation for the Fragmentation of Light and Heavy Quarks at Large x

We present a QCD study of fragmentation processes for light and heavy quarks in the semi-inclusive region of large x. Large logarithmic terms, due to soft-gluon radiation, are evaluated and resummed to all perturbative orders in the QCD coupling alpha_s. Complete analytical results to next-to-leading logarithmic accuracy are given for one-particle and two-particle inclusive distributions in e+e- annihilation and DIS. Factorization of parton radiation at low transverse momenta is exploited to identify the universal (process-independent) perturbative fragmentation function that controls heavy-quark processes, and to perform next-to-leading logarithmic resummation of its soft-gluon contributions. To gauge the quantitative impact of resummation, we perform numerical studies of light- and heavy-quark fragmentation in e+e- collisions.

hep-ph↗
arXiv2001

The $\pt$ spectrum of heavy quarks in photoproduction

We illustrate a formalism that allows to match the next-to-leading order cross section for the photoproduction of heavy quarks to the cross section obtained by resumming logarithms of $\pt/m$ to the next-to-leading accuracy, thus giving a sensible prediction for any value of $\pt$. We present a comparison between our predictions and H1 and ZEUS data.

hep-ph↗
arXiv2001

Physics at Large Rapidities in $γ^*γ^* \to$ Hadrons at LEP2

We compute the order-$\as$ corrections to the total cross section and to jet rates in $γ^* γ^* \to$ hadrons for the process $\epem\to\epem +$ hadrons. We use a NLO order general-purpose partonic Monte Carlo event generator that allows the computation of a rate differential in the produced leptons and hadrons. We compare our results with the experimental data for $\epem\to\epem +$ hadrons at LEP2.

hep-ph↗
arXiv2001

The p_T Spectrum in Heavy-Flavour Photoproduction

We consider the transverse-momentum distribution of heavy flavours in photon-hadron collisions. We present a formalism in which large transverse-momentum logarithms are resummed to the next-to-leading level, and mass effects are included exactly up to order alpha_em alpha_s^2, so as to retain predictivity at both small and large transverse momenta. Phenomenological applications relevant to charm photoproduction at HERA are given.

hep-ph↗
arXiv2000

QCD radiative corrections to $γ^*γ^* \to$ hadrons

We compute the order-$\as$ corrections to the total cross section and to jet rates for the process $\epem\to\epem +$ hadrons, where the hadrons are produced through crossed-channel quark exchange in the hard scattering of two off-shell photons originating from the incoming leptons. We use a next-to-leading order general-purpose partonic Monte Carlo event generator that allows the computation of a rate differential in the produced leptons and hadrons. We compare our results with the available experimental data for $\epem\to\epem +$ hadrons at LEP2.

hep-ph↗
arXiv2000

Report of the QCD Working Group

The activities of the QCD working group concentrated on improving the understanding and Monte Carlo simulation of multi-jet final states due to hard QCD processes at LEP, i.e. quark-antiquark plus multi-gluon and/or secondary quark production, with particular emphasis on four-jet final states and b-quark mass effects. Specific topics covered are: relevant developments in the main event generators PYTHIA, HERWIG and ARIADNE; the new multi-jet generator APACIC++; description and tuning of inclusive (all-flavour) jet rates; quark mass effects in the three- and four-jet rates; mass, higher-order and hadronization effects in four-jet angular and shape distributions; b-quark fragmentation and gluon splitting into b-quarks.

hep-ph↗
arXiv1998

The p_T Spectrum in Heavy-Flavour Hadroproduction

We consider the transverse-momentum distribution of heavy flavours in hadronic collisions. We present a formalism in which large transverse-momentum logarithms are resummed at the next-to-leading level, and mass effects are included exactly up to order α_strong^3, so as to retain predictivity at both small and large transverse momenta. As an example, we apply our formalism to b production at the Tevatron.

hep-ph↗
arXiv1997

NLO Production and Decay of Quarkonium

We present a calculation of next-to-leading-order (NLO) QCD corrections to total hadronic production cross sections and to light-hadron-decay rates of heavy quarkonium states. Both colour-singlet and colour-octet contributions are included. We discuss in detail the use of covariant projectors in dimensional regularization, the structure of soft-gluon emission and the overall finiteness of radiative corrections. We compare our approach with the NLO version of the threshold-expansion technique recently introduced by Braaten and Chen. Most of the results presented here are new. Others represent the first independent reevaluation of calculations already known in the literature. In this case a comparison with previous findings is reported.

hep-ph↗
arXiv1996

Charmed Mesons Fragmentation Functions

Fragmentation functions for heavy-light mesons, like the charmed D, D^* mesons, are proposed. They rest on next-to-leading QCD Perturbative Fragmentation Functions for heavy quarks, with the addition of a non-perturbative term describing phenomenologically the quark --> meson transition. The cross section for production of large p_T D, D^* mesons at the Tevatron is evaluated in this framework.

hep-ph↗
arXiv1996

Heavy Quarks Photoproduction

The state of the art of the theoretical calculations for heavy quarks photoproduction is reviewed. The full next-to-leading order calculation and two possible resummations, the high energy one for total cross sections and the large $p_T$ one for differential cross sections, are described.

hep-ph↗