The Majorana nature of neutrinos can be experimentally verified only via lepton-number violating processes involving charged leptons. We study 36 lepton-number violating (LV ) processes from the decays of tau leptons and pseudoscalar mesons. These decays are absent in the Standard Model but, in presence of Majorana neutrinos in the mass range ∼ 100 MeV to 5 GeV, the rates for these processes would be enhanced due to their resonant contribution. We calculate the transition rates and branching fractions and compare them to the current bounds from direct experimental searches for ∆L = 2 tau and rare meson decays. The experimental non-observation of such LV processes places stringent bounds on the Majorana neutrino mass and mixing and we summarize the existing limits. We also extend the search to hadron collider experiments. We find that, at the Tevatron with 8 fb −1 integrated luminosity, there could be 2σ (5σ) sensitivity for resonant production of a Majorana neutrino in the µ ± µ ± modes in the mass range of ∼ 10 − 180 GeV (10 − 120 GeV). This reach can be extended to ∼ 10 − 375 GeV (10 − 250 GeV) at the LHC of 14 TeV with 100 fb −1 . The production cross section at the LHC of 10 TeV is also presented for comparison. We study the µ ± e ± modes as well and find that the signal could be large enough even taking into account the current bound from neutrinoless double-beta decay. The signal from the gauge boson fusion channel W + W + → ℓ + 1 ℓ + 2 at the LHC is found to be very weak given the rather small mixing parameters. We comment on the search strategy when a τ lepton is involved in the final state.

Based on the challenges in single-mode phototherapy, this review summarizes the significant research progress in combinatorial strategies with phototherapy.

The Majorana nature of neutrinos may only be experimentally verified via lepton-number violating processes involving charged leptons. We explore the ∆L = 2 like-sign dilepton production at hadron colliders to search for signals of Majorana neutrinos. We find significant sensitivity for resonant production of a Majorana neutrino in the mass range of 10 − 80 GeV at the current run of the Tevatron with 2 fb −1 integrated luminosity, and in the range of 10 − 400 GeV at the LHC with 100 fb −1 .Neutrinos are arguably the most elusive particles in the standard model (SM) spectrum. The evidence is strong that neutrinos are massive and their flavors defined with respect to the charged leptons oscillate [1], indicating the need of extension beyond the SM. We do not know the nature of the mass generation and flavor mixing. In particular, we are clueless if neutrinos are of Dirac or Majorana type -the former preserves the lepton number (L), and the latter violates it by two units. Thus, the unambiguous proof of the existence of a Majorana neutrino is the observation of a lepton-number violation process, which would have profound implications in particle physics, nuclear physics, and cosmology. Since neutrinos are so weakly interacting and leave no trace in ordinary detectors, the only appropriate signatures must involve charged leptons via the charge-current interactions for a ∆L = 2 process.The simplest extension of the Standard Model to include Majorana neutrinos is to introduce n right-handed SM singlet neutrinos N aR (a = 1, 2, · · · , n), and n ≥ 2 in order to generate at least two massive neutrinos. Besides the Dirac masses m D from the Yukawa interactions, there is also a possible heavy Majorana mass term relations between the flavors defined with respect to the charged leptons ℓ and mass eigenstatesIn the simplest incarnation without further flavor structure or new states, the light neutrino masses m ν m are of the order of magnitude m 2 D /B, while the heavy neutrino masses are m N m ′ ≃ B. The corresponding mixing angles are of V V * ∼ m ν m /m N m ′ , and thus U U † ≈ I. However, we will take a phenomenological approach toward the mass and mixing parameters without assuming any relationship a priori.In terms of the mass eigenstates, the gauge interaction Lagrangian can be written aswhere P L is the left-handed chirality projection operator. There exist constraints on the heavy neutrino mass and the mixing elements V ℓm ′ . Since we are interested in the collider searches, we consider m N ≫ 1 GeV. By far, the strongest bound is from the non-observation of the neutrinoless double-β decay (0νββ) [2]. It translates

Photodynamic therapy (PDT) has been extensively investigated for decades for tumor treatment because of its non-invasiveness, spatiotemporal selectivity, lower side-effects, and immune activation ability.