|
|
| LF21 EXPERIMENT, RESPONSIBLE: Gino Isidori |
|
PHENOMENOLOGY OF ELEMENTARY PARTICLE INTERACTIONS AT COLLIDERS.
We investigate particle interactions within and beyond the Standard Model (SM) with particular attention to the following two themes: I. Flavour Physics [CP violation and Rare decays of both quarks and leptons]; II. Hadronic cross-sections [radiative corrections to e+e- --> hadrons(+gamma), gamma gamma into pseudoscalars at DAPHNE and total cross sections].
I. FLAVOUR PHYSICS
We investigate the mechanism of flavour mixing, both within and beyond the SM: (I) we formulate models of flavour mixing beyond the SM; (II) we analyse possible signatures of these non-standard frameworks in low-energy observables; (III) we perform precise SM calculations aimed to reduce the theoretical uncertainties of these low-energy tests; (IV) we analyse the high-energy implications of the precise low-energy tests of flavour mixing. The main theoretical tool we use are effective-field theory approaches (both to describe physics beyond the SM and to describe the low-energy limit of the SM itself).
The PDG activities of the Naples group aim at having a complete compilation of all available data regarding kaon physics and related CP and CPT physics. Particular attention is being devoted to insertion of data for CPT and Quantum Mechanics tests.
Main recent results obtained within this line of research:
1) We have demonstrated the viability of leptogenesis in models where the neutrino Yukawa coupling is the only irreducible sources of lepton-flavour symmetry breaking (Minimal Lepton Flavour Violation hypothesis).
2) We have performed a new systematic analsysis of new-physics effects (especially within the so-called MSSM) in rare K decays (both K->pi nn and K->pi ll).
3) We have analysed the implications of the MSSM at large-tan(beta) in various B decays, establishing interesting links between low- and high-energy observables (in particular the Higgs boson mass).
Main future developments within this line of research:
1) Theoretical analsysis of the possible implementation of the MFV hypothesis in Grand-Unified Theories, and analysis of the phenomenological implications at low energies.
2) Improved phenomeological anlyses of large-tan(beta) scenarios.
II. HADRONIC CROSS-SECTIONS
Two main themes :
a) Precision physics in radiative processes at DAPHNE: two projects are under study, the+e- into pi+pi- gamma, using both a chiral model and scalar QED for calculating photon emission from the final pions and comparison with KLOE and Novosibirsk, two photon physics outside the phi-resonance and to energies up to the nucleon-nucleon threshold.
Main results:
Study of the cross-section for e+e- into pi+pi- gamma, using both a chiral model and scalar QED for calculating photon emission from the final pions and preparation of a MonteCarlo program which allows to study diffrent models of final state emission from scalar or pseudoscalar particles.
Present activities:
Study of e+e- into 3 pion final state
b) Quantum Chromodynamics and the rise of total cross-sections: this problem is investigated in various processes, both with protons and with photons,using different theoretical approaches, factorization, eikonalization of QCD minijet cross-sections, soft gluon resummation techniques.
Main results:
A sum rule for the elastic differential cross-section based on analiticity and unitarity and a description of the total proton-proton and proton-antiproton cross-section.
Planned activity:
Study of the elastic proton-proton and proton-antiproton cross-section and extension to cosmic rays p-air cross-sections.
Comparison between proton-proton, gamma-proton and gamma gamma cross-section highlighting how the future measurements at LHC can restrict the range of predictions at CLIC, through a cross-talk between LHC, HERA and CLIC.
Preparation of an impact parameter distribution function based on soft gluon summation, with different parameter sets.
Organization of Meetings:
LNF Spring School "Bruno Touschek", held yearly, since 1996. |
PHENOMENOLOGY OF ELEMENTARY PARTICLE INTERACTIONS AT COLLIDERS.
We investigate particle interactions within and beyond the Standard Model (SM) with particular attention to the following three main themes:
I. Precise tests of the Standard Model at low energies (CP violation and Rare decays of both quarks and leptons).
II. Higgs physics and phenomenology of Supersymmetric extensions of the SM.
III. Analytic and numerical developments in QCD
I. Flavor Physics
We investigate the mechanism of flavour mixing, both within and beyond the SM: (I) we formulate models of flavour mixing beyond the SM; (II) we analyse possible signatures of these non-standard frameworks in low-energy observables; (III) we perform precise SM calculations aimed to reduce the theoretical uncertainties of these low-energy tests; (IV) we analyse the high-energy implications of the precise low-energy tests of flavour mixing. The main theoretical tool we use are effective-field theory approaches (both to describe physics beyond the SM and to describe the low-energy limit of the SM itself).
The PDG activities of the Naples group aim at having a complete compilation of all available data regarding kaon physics and related CP and CPT physics. Particular attention is being devoted to insertion of data for CPT and Quantum Mechanics tests.
Main recent results obtained within this line of research:
1) We have performed a new systematic analysis of new-physics effects in B, D, and K physics observables.
2) We have analyzed the implications of the recent flavor-physics measurements in constraining supersymmetric extensions of the SM.
Main future developments within this line of research:
1) Formulation of general mechanisms of flavor symmetry breaking alternative to the MFV hypothesis.
2) Improved phenomenological analyses in view of future updated measurements.
3) Analysis of unified models of quark and lepton masses in the context of grand-unified theories.
II. Higgs physics and phenomenology of Supersymmetric extensions of the SM.
The discovery of the Higgs boson has opened a new era in particle physics. While it is clear that this particle is, to a first approximation, the scalar boson predicted by the Standard Model, there are still several properties of this particle that needs to be investigated with higher precision. A Higgs boson with mass around 125 GeV is compatible with supersymmetric extensions of the SM with new particles close to the TeV scale, but also with no new physics up to the Planck scale. These two extreme scenarios have profound implications for our understanding of fundamental interactions and need to be explored in more detail.
Recent results obtained within this line of research:
1) Analysis of the implications of the Higgs mass measurement of the stability and the meta-stability of the SM potential at high field values.
2) Analysis of the implications of the Higgs mass measurement, and the absence of direct signals of new physics, in supersymmetric extensions of the SM.
Main future developments within this line of research:
1) Deeper investigation of the viability of models with no new physics close to the TeV scale, and refined analysis of the implications of the Higgs mass measurement in this context.
2) Analysis of the experimental signatures of possible non-standard properties of the Higgs boson
3) Construction of "quasi-natural" supersymmetric models able to satisfy all the existing constraints of the LHC at 8TeV, and analysis of the implications for he 13-14 TeV run.
III. Analytic and numerical developments in QCD
To match the experimental precision of the LHC measurements one needs to compute signal processes
(such as the Higgs production rate) and corresponding background processes beyond the leading
order in the strong and/or the electroweak coupling constants. In
recent years, we have witnessed a fast progress in the evaluation of the
production rates mentioned above, in association with many jets, at
next-to-leading order (NLO) accuracy in the strong coupling constant,
which reduces the theoretical uncertainty to the 10\% level.
That has relied upon efficient methods to compute one-loop amplitudes
with many legs, and upon subtraction algorithms to evaluate QCD cross
sections at NLO. Such algorithms are based on the
universality -- i.e. on the independence from a specific scattering
process -- of the infrared emissions.
Evaluating production rates at next-to-next-to-leading order (NNLO) allows us
to reduce the theoretical uncertainty to the 3-5\% level.
Accordingly, various processes have been evaluated at NNLO accuracy.
However, no general algorithm exists yet for the evaluation of cross sections at this accuracy.
Main results obtained:
1) Design of a subtraction scheme for the evaluation of NNLO cross sections for jet production in electron-positron annihilation
2) Algebraic methods (symbols and coproducts) for the efficient computation of massless two-loop amplitudes
Recent results obtained within this line of research:
3) The computation of the fully differential NNLO cross section for the
associated production of a Higgs and a W boson;
Main future developments within this line of research:
1) Extension of the subtraction scheme above to the NNLO cross sections for Higgs and vector boson production
in association with many jets in hadron collisions
2) Extension of the algebraic methods above to the computation of two-loop amplitudes with massive quarks and/or
massive propagators
3) Extension of the NNLO computation for the HW associated production to the case of ZH associated production.
4) Completion of the calculation of the differential cross section for H plus 3 jets via gluon fusion at NLO in QCD.
|
Istituto Nazionale di Fisica Nucleare - Piazza dei Caprettari, 70 - 00186 Roma
tel. +39 066840031 - fax +39 0668307924 - email: presidenza@presid.infn.it
|
|
|
|
