We study the invisible decay of neutral hadrons in a representative model of the dark sector. The mesons KL and B0 decay into the dark sector with branching rates that can be at the current ...experimental limits. The neutron decays with a rate that could either explain the neutron lifetime puzzle (although only for an extreme choice of the parameters and a fine-tuned value of the masses) or be just above the current limit of its invisible decay (τNinv≳1029 years) if kinematically allowed. These invisible decays of ordinary matter provide a novel and promising window into new physics that should be vigorously pursued.
A
bstract
Quantum tomography provides the full reconstruction of the density matrix of a state. We use it to study the Higgs boson decay into weak gauge bosons. Anomalous couplings beyond the ...Standard Model can be constrained by means of observables easily defined in terms of the polarization density matrix. We describe a strategy based on three observables that together provide the most stringent limits. Two of these observables are linked to the entanglement between the polarizations of the two gauge bosons, the other is based on CP-odd combinations of one momentum and two polarizations. We find for the
Z
channel that this strategy offers, already with the available LHC data, limits competitive with the best available bounds. We argue that the inclusion of these observables in routine experimental analyses can lead to more stringent global fit limits.
The μ+ → e+ X decay, where X is a dark sector boson, provides one of the strongest available bounds on the scale of dark sector interactions. The X boson can be an axion or a dark photon. We show ...that the concurrent determination of the antimuon and positron polarizations makes it possible to distinguish with a confidence level of 99% between the two dark sector portals with as few as 6 observed events in the case of the massless dark photon. Instead, the massive spin-1, dimension 4 dark portal cannot be distinguished from the axionlike case. We also discuss the possibility that the X boson be a massive spin-2 particle.
If dark photons are massless, they couple to standard-model particles only via higher dimensional operators, while direct (renormalizable) interactions induced by kinetic mixing, which motivates most ...of the current experimental searches, are absent. We consider the effect of possible flavor-changing magnetic-dipole couplings of massless dark photons in kaon physics. In particular, we study the branching ratio for the process K^{+}→π^{+}π^{0}γover ¯ with a simplified-model approach, assuming the chiral quark model to evaluate the hadronic matrix element. Possible effects in the K^{0}-Kover ¯^{0} mixing are taken into account. We find that branching ratios up to O(10^{-7}) are allowed-depending on the dark-sector masses and couplings. Such large branching ratios for K^{+}→π^{+}π^{0}γover ¯ could be of interest for experiments dedicated to rare K^{+} decays like NA62 at CERN, where γover ¯ can be detected as a massless invisible system.
Z Boson Decay into Light and Darkness Fabbrichesi, M; Gabrielli, E; Mele, B
Physical review letters,
2018-Apr-27, Letnik:
120, Številka:
17
Journal Article
Recenzirano
Odprti dostop
We study the Z→γγover ¯ process in which the Z boson decays into a photon γ and a massless dark photon γover ¯, when the latter couples to standard-model fermions via dipole moments. This is a simple ...yet nontrivial example of how the Landau-Yang theorem-ruling out the decay of a massive spin-1 particle into two photons-is evaded if the final particles can be distinguished. The striking signature of this process is a resonant monochromatic single photon in the Z-boson center of mass together with missing momentum. LEP experimental bounds allow a branching ratio up to about 10^{-6} for such a decay. In a simplified model of the dark sector, the dark-photon dipole moments arise from one-loop exchange of heavy dark fermions and scalar messengers. The corresponding prediction for the rare Z→γγover ¯ decay width can be explored with the large samples of Z bosons foreseen at future colliders.
Incapacitating agents are chemical weapons that produce a temporary disabling condition that persists for hours or days after exposure. Their main site of action is the central nervous system and ...includes substances that are considered depressants or stimulants. While not intended to cause death, can produce significant morbidity in affected patients. The objective of this narrative review is to update the toxicokinetics, toxicodynamics, diagnosis, and treatment of these chemicals, considering that 20 years have passed since the Nord Ost Siege, where a fentanyl derivative was used by Russian forces to neutralize a group of Chechen dissidents. A bibliographic search was carried out in PubMed, SciELO, and Cochrane Library databases as well as nonindexed scientific literature.
The evidence for a new neutral scalar particle from the 750 GeV diphoton excess, and the absence of any other signal of new physics at the LHC so far, suggests the existence of new coloured scalars. ...To study this possibility, we propose a supersymmetry inspired simplified model, extending the Standard Model with a singlet scalar and with heavy scalar fields carrying both colour and electric charges – new scalar quarks. To allow the latter to decay, and to generate the dark matter of the Universe, we also add a neutral fermion to the particle content. We show that this model provides a two-parameter fit to the observed diphoton excess consistently with cosmology, while the allowed parameter space is bounded by the consistency of the model. In the context of our simplified model this implies the existence of other supersymmetric particles accessible at the LHC, rendering this scenario falsifiable.
We study the decay of the Z vector boson into a photon and a massless (invisible) dark photon in high-energy collisions. The photon can be used as a trigger for the event, while the dark photon is ...detected indirectly as missing momentum in the event final state. We investigate the possibility of searching for such a dark photon at the LHC, HL-LHC, and future lepton colliders, and compare the respective sensitivities. As expected, the best result is found for the lepton colliders running at the Z mass, FCC-ee and CEPC, with a final sensitivity to branching ratios of order O(10−11) . We also discuss how to use the photon angular distribution of the events in lepton collisions to discriminate between the dark photon and a pseudoscalar state like the axion.
Aspergillus osteomyelitis is a rare infection. We reviewed 310 individual cases reported in the literature from 1936 to 2013. The median age of patients was 43 years (range, 0–86 years), and 59% were ...males. Comorbidities associated with this infection included chronic granulomatous disease (19%), haematological malignancies (11%), transplantation (11%), diabetes (6%), pulmonary disease (4%), steroid therapy (4%), and human immunodeficiency virus infection (4%). Sites of infection included the spine (49%), base of the skull, paranasal sinuses and jaw (18%), ribs (9%), long bones (9%), sternum (5%), and chest wall (4%). The most common infecting species were Aspergillus fumigatus (55%), Aspergillus flavus (12%), and Aspergillus nidulans (7%). Sixty-two percent of the individual cases were treated with a combination of an antifungal regimen and surgery. Amphotericin B was the antifungal drug most commonly used, followed by itraconazole and voriconazole. Several combination or sequential therapies were also used experimentally. The overall crude mortality rate was 25%.