Generalized uncertainty relations are known to provide a minimal length √ β. The effect of such m... more Generalized uncertainty relations are known to provide a minimal length √ β. The effect of such minimal length in the Casimir-Polder interactions between neutral atoms is studied. The first order correction term in the minimal uncertainty parameter is derived and found to describe an attractive potential scaling as r −9 as opposed to the well known r −7 long range retarded potential.
The European Physical Journal C - Particles and Fields, 2003
The cross section for the reaction e − e − → ℓ − ℓ − (ℓ = µ, τ ) is calculated in models with hea... more The cross section for the reaction e − e − → ℓ − ℓ − (ℓ = µ, τ ) is calculated in models with heavy Majorana neutrinos mediating lepton number violating amplitudes at the loop level. The contributing four-point functions are evaluated exactly (numerically) taking into account the full propagator dependence on external momenta, thereby extending to the energy range of interest for the next linear colliders an earlier approximate low energy calculation. The amplitude shows a non-decoupling behaviour relative to the heavy Majorana neutrino masses, but due to the stringent bounds on heavy-light mixing the signal cross section attains observable values only for the less constrained τ signal. The cross section induced by lepton number violation in the SU (2) L doublet sneutrino sector of supersymmetric extensions of the standard model is constrained by the upper limits on neutrino masses and probably too tiny to be observable.
The potential energy of a static charge distribution on a lattice is rigorously computed in the s... more The potential energy of a static charge distribution on a lattice is rigorously computed in the standard compact quantum electrodynamic model. The method used follows closely that of Weyl for ordinary quantum electrodynamics in continuous space-time. The potential energy of the static charge distribution is independent of temperature and can be calculated from the lattice version of Poisson's equation. It is the usual Coulomb potential.
We analyze the potentiality of the CERN Large Hadron Collider to probe the Higgs boson couplings ... more We analyze the potentiality of the CERN Large Hadron Collider to probe the Higgs boson couplings to the electroweak gauge bosons. We parametrize the possible deviations of these couplings due to new physics in a model independent way, using the most general dimension-six effective lagrangian where the SU (2) L ⊗ U (1) Y is realized linearly. For intermediate Higgs masses, the decay channel into two photons is the most important one for Higgs searches at the LHC. We study the effects of these new interactions on the Higgs production mechanism and its subsequent decay into two photons. We show that the LHC will be sensitive to new physics scales beyond the present limits extracted from the LEP and Tevatron physics.
Left-right symmetric models provide a natural framework for neutrinoless double beta (0νββ) decay... more Left-right symmetric models provide a natural framework for neutrinoless double beta (0νββ) decay. In the analysis of 0νββ decay in left-right symmetric models, however, it is usually assumed that all neutrinos are light. On the other hand, heavy right-handed neutrinos appear quite naturally in left-right symmetric models and should therefore not be neglected. Assuming the existence of at least one right-handed heavy neutrino, absence of 0νββ decay of 76 Ge currently provides the following limits on the mass and mixing angle of right-handed W-bosons: m W R ≥ 1.1 TeV and tan(ζ) ≤ 4.7 × 10 −3 for a particular value of the effective right-handed neutrino mass, m (V ) N = 1 TeV, and in the limit of infinitly massive doubly charged Higgs (∆ −− ). The effects of the inclusion of the Higgs triplet on 0νββ decay are also discussed.
For a bound state internal wave function respecting parity symmetry, it can be rigorously argued ... more For a bound state internal wave function respecting parity symmetry, it can be rigorously argued that the mean electric dipole moment must be strictly zero. Thus, both the neutron, viewed as a bound state of three quarks, and the water molecule, viewed as a bound state of ten electrons two protons and an oxygen nucleus, both have zero mean electric dipole moments. Yet, the water molecule is said to have a nonzero dipole moment strength d = eΛ with ΛH 2 O ≈ 0.385Ȧ. The neutron may also be said to have an electric dipole moment strength with Λneutron ≈ 0.612 f m. The neutron analysis can be made experimentally consistent, if one employs a quark-diquark model of neutron structure.
Lepton number violation could be manifest in the sneutrino sector of supersymmetric extensions of... more Lepton number violation could be manifest in the sneutrino sector of supersymmetric extensions of the standard model with conserved R-parity. Then sneutrinos decay partly into the "wrong sign charged lepton" final state, if kinematically accessible. In sneutrino pair production or associated single sneutrino production, the signal then is a like sign dilepton final state. Under favourable circumstances, such a signal could be visible at the LHC or a next generation linear collider for a relative sneutrino mass-splitting of order O(0.001) and sneutrino width of order O(1 GeV). On the other hand, the like sign dilepton event rate at the TEVATRON is probably too small to be observable.
The well-known Klein paradox for the relativistic Dirac wave equation consists in the computation... more The well-known Klein paradox for the relativistic Dirac wave equation consists in the computation of possible "negative probabilities" induced by certain potentials in some regimes of energy. The paradox may be resolved by employing the notion of electronpositron pair production in which the number of electrons present in a process can increase. The Klein paradox also exists in the Maxwell's equations viewed as the wave equation for photons. In a medium containing "inverted energy populations" of excited atoms, e.g. in a LASER medium, one may again compute possible "negative probabilities." The resolution of the electromagnetic Klein paradox is that when the atoms decay, the final state may contain more photons then were contained the initial state. The optical theorem total cross-section for scattering photons from excited state atoms may then be computed as negative within a frequency band with matter induced amplification.
It is shown that the difference in the distributions of positive (µ+) and negative charged lepton... more It is shown that the difference in the distributions of positive (µ+) and negative charged leptons (µ−) in reactions → µ+µ− +�¯ � and → W ±µ∓ +�(¯�) at √ s > 200 GeV leads to observable
It is shown that the difference in the momentum distributions of positively (mu +, e+) and negati... more It is shown that the difference in the momentum distributions of positively (mu +, e+) and negatively (mu -, e-) charged leptons in the reactions of type gamma gamma to mu +mu - + Nnu , gamma gamma to Wpm mu mp + Nnu at sqrt {s}> 200 GeV with polarized photons demonstrates a considerable {ITALIC charge asymmetry} of muon
We study the (2+1) dimensional Dirac oscillator in a homogeneous magnetic field in the noncommuta... more We study the (2+1) dimensional Dirac oscillator in a homogeneous magnetic field in the noncommutative plane. It is shown that the effect of non-commutativity is twofold: i) momentum non commuting coordinates simply shift the critical value (B cr ) of the magnetic field at which the well known left-right chiral quantum phase transition takes place (in the commuting phase); ii) non-commutativity in the space coordinates induces a new critical value of the magnetic field, B * cr , where there is a second quantum phase transition (right-left), -this critical point disappears in the commutative limit-. The change in chirality associated with the magnitude of the magnetic field is examined in detail for both critical points. The phase transitions are described in terms of the magnetisation of the system. Possible applications to the physics of silicene and graphene are briefly discussed.
Generalized uncertainty relations are known to provide a minimal length √ β. The effect of such m... more Generalized uncertainty relations are known to provide a minimal length √ β. The effect of such minimal length in the Casimir-Polder interactions between neutral atoms is studied. The first order correction term in the minimal uncertainty parameter is derived and found to describe an attractive potential scaling as r −9 as opposed to the well known r −7 long range retarded potential.
The European Physical Journal C - Particles and Fields, 2003
The cross section for the reaction e − e − → ℓ − ℓ − (ℓ = µ, τ ) is calculated in models with hea... more The cross section for the reaction e − e − → ℓ − ℓ − (ℓ = µ, τ ) is calculated in models with heavy Majorana neutrinos mediating lepton number violating amplitudes at the loop level. The contributing four-point functions are evaluated exactly (numerically) taking into account the full propagator dependence on external momenta, thereby extending to the energy range of interest for the next linear colliders an earlier approximate low energy calculation. The amplitude shows a non-decoupling behaviour relative to the heavy Majorana neutrino masses, but due to the stringent bounds on heavy-light mixing the signal cross section attains observable values only for the less constrained τ signal. The cross section induced by lepton number violation in the SU (2) L doublet sneutrino sector of supersymmetric extensions of the standard model is constrained by the upper limits on neutrino masses and probably too tiny to be observable.
The potential energy of a static charge distribution on a lattice is rigorously computed in the s... more The potential energy of a static charge distribution on a lattice is rigorously computed in the standard compact quantum electrodynamic model. The method used follows closely that of Weyl for ordinary quantum electrodynamics in continuous space-time. The potential energy of the static charge distribution is independent of temperature and can be calculated from the lattice version of Poisson's equation. It is the usual Coulomb potential.
We analyze the potentiality of the CERN Large Hadron Collider to probe the Higgs boson couplings ... more We analyze the potentiality of the CERN Large Hadron Collider to probe the Higgs boson couplings to the electroweak gauge bosons. We parametrize the possible deviations of these couplings due to new physics in a model independent way, using the most general dimension-six effective lagrangian where the SU (2) L ⊗ U (1) Y is realized linearly. For intermediate Higgs masses, the decay channel into two photons is the most important one for Higgs searches at the LHC. We study the effects of these new interactions on the Higgs production mechanism and its subsequent decay into two photons. We show that the LHC will be sensitive to new physics scales beyond the present limits extracted from the LEP and Tevatron physics.
Left-right symmetric models provide a natural framework for neutrinoless double beta (0νββ) decay... more Left-right symmetric models provide a natural framework for neutrinoless double beta (0νββ) decay. In the analysis of 0νββ decay in left-right symmetric models, however, it is usually assumed that all neutrinos are light. On the other hand, heavy right-handed neutrinos appear quite naturally in left-right symmetric models and should therefore not be neglected. Assuming the existence of at least one right-handed heavy neutrino, absence of 0νββ decay of 76 Ge currently provides the following limits on the mass and mixing angle of right-handed W-bosons: m W R ≥ 1.1 TeV and tan(ζ) ≤ 4.7 × 10 −3 for a particular value of the effective right-handed neutrino mass, m (V ) N = 1 TeV, and in the limit of infinitly massive doubly charged Higgs (∆ −− ). The effects of the inclusion of the Higgs triplet on 0νββ decay are also discussed.
For a bound state internal wave function respecting parity symmetry, it can be rigorously argued ... more For a bound state internal wave function respecting parity symmetry, it can be rigorously argued that the mean electric dipole moment must be strictly zero. Thus, both the neutron, viewed as a bound state of three quarks, and the water molecule, viewed as a bound state of ten electrons two protons and an oxygen nucleus, both have zero mean electric dipole moments. Yet, the water molecule is said to have a nonzero dipole moment strength d = eΛ with ΛH 2 O ≈ 0.385Ȧ. The neutron may also be said to have an electric dipole moment strength with Λneutron ≈ 0.612 f m. The neutron analysis can be made experimentally consistent, if one employs a quark-diquark model of neutron structure.
Lepton number violation could be manifest in the sneutrino sector of supersymmetric extensions of... more Lepton number violation could be manifest in the sneutrino sector of supersymmetric extensions of the standard model with conserved R-parity. Then sneutrinos decay partly into the "wrong sign charged lepton" final state, if kinematically accessible. In sneutrino pair production or associated single sneutrino production, the signal then is a like sign dilepton final state. Under favourable circumstances, such a signal could be visible at the LHC or a next generation linear collider for a relative sneutrino mass-splitting of order O(0.001) and sneutrino width of order O(1 GeV). On the other hand, the like sign dilepton event rate at the TEVATRON is probably too small to be observable.
The well-known Klein paradox for the relativistic Dirac wave equation consists in the computation... more The well-known Klein paradox for the relativistic Dirac wave equation consists in the computation of possible "negative probabilities" induced by certain potentials in some regimes of energy. The paradox may be resolved by employing the notion of electronpositron pair production in which the number of electrons present in a process can increase. The Klein paradox also exists in the Maxwell's equations viewed as the wave equation for photons. In a medium containing "inverted energy populations" of excited atoms, e.g. in a LASER medium, one may again compute possible "negative probabilities." The resolution of the electromagnetic Klein paradox is that when the atoms decay, the final state may contain more photons then were contained the initial state. The optical theorem total cross-section for scattering photons from excited state atoms may then be computed as negative within a frequency band with matter induced amplification.
It is shown that the difference in the distributions of positive (µ+) and negative charged lepton... more It is shown that the difference in the distributions of positive (µ+) and negative charged leptons (µ−) in reactions → µ+µ− +�¯ � and → W ±µ∓ +�(¯�) at √ s > 200 GeV leads to observable
It is shown that the difference in the momentum distributions of positively (mu +, e+) and negati... more It is shown that the difference in the momentum distributions of positively (mu +, e+) and negatively (mu -, e-) charged leptons in the reactions of type gamma gamma to mu +mu - + Nnu , gamma gamma to Wpm mu mp + Nnu at sqrt {s}> 200 GeV with polarized photons demonstrates a considerable {ITALIC charge asymmetry} of muon
We study the (2+1) dimensional Dirac oscillator in a homogeneous magnetic field in the noncommuta... more We study the (2+1) dimensional Dirac oscillator in a homogeneous magnetic field in the noncommutative plane. It is shown that the effect of non-commutativity is twofold: i) momentum non commuting coordinates simply shift the critical value (B cr ) of the magnetic field at which the well known left-right chiral quantum phase transition takes place (in the commuting phase); ii) non-commutativity in the space coordinates induces a new critical value of the magnetic field, B * cr , where there is a second quantum phase transition (right-left), -this critical point disappears in the commutative limit-. The change in chirality associated with the magnitude of the magnetic field is examined in detail for both critical points. The phase transitions are described in terms of the magnetisation of the system. Possible applications to the physics of silicene and graphene are briefly discussed.
Uploads
Papers by O. Panella