Some possible sources of IceCube TeV-PeV neutrino events

The IceCube Collaboration has observed 37 neutrino events in the energy range $30\, TeV\leq E_{\nu} \leq 2$ PeV and the sources of these neutrinos are unknown. Here we have shown that positions of 12 high energy blazars and the position of the FR-I galaxy Centaurus A, coincide within the error circles of ten IceCube events, the later being in the error circle of the highest energy event so far observed by IceCube. Two of the above blazars are simultaneously within the error circles of the Telescope Array hotspot and one IceCube event. We found that the blazar H2356-309 is within the error circles of three IceCube events. We propose that photohadronic interaction of the Fermi accelerated high energy protons with the synchrotron/SSC background photons in the nuclear region of these high energy blazars and AGN are probably responsible for some of the observed IceCube events.Comment: 14 pages, 3 figure, references adde

Multi-TeV flaring from blazars: Markarian 421 a case study

The TeV blazar Markarian 421 underwent multi-TeV flaring during April 2004 and simultaneously observed in x-ray and TeV energies. It was observed that the TeV outbursts had no counterparts in the lower energies, which implies that this might be an orphan flare. In the context of hadronic model, we have shown that this multi-TeV flaring can be produced due to the interaction of Fermi-accelerated protons of energy $\lesssim 168$ TeV with the background photons in the low energy tail of the synchrotron self-Compton spectrum of the blazar jet. We fit very well the flaring spectrum with this model. Based on this study, we speculate that Mrk 501 and PG 1553+113 are possible candidates for orphan flaring in the future.Comment: 8 pages, two columns, 3 figure

Photohadronic scenario in interpreting the February-March 2014 flare of 1ES 1011+496

The extraordinary multi-TeV flare from 1ES 1011 +496 during February-March 2014 was observed by MAGIC telescopes for 17 nights and the average spectrum of the whole period has a non-trivial shape. We have used the photohadronic model and a template EBL model to explain the average spectrum which fits well to the flare data. The spectral index $\alpha$ is the only free parameter in our model. We have also shown that the non-trivial nature of the spectrum is due to the change in the behavior of the optical depth above $\sim 600$ GeV $\gamma$-ray energy accompanied with the high SSC flux.Comment: 11 pages, 3 figures, LaTe

Blazar origin of some IceCube events

Recently ANTARES collaboration presented a time dependent analysis to a selected number of flaring blazars to look for upward going muon events produced from the charge current interaction of the muon neutrinos. We use the same list of flaring blazars to look for possible positional correlation with the IceCube neutrino events. In the context of photohadronic model we propose that the neutrinos are produced within the nuclear region of the blazar where Fermi accelerated high energy protons interact with the background synchrotron/SSC photons. Although we found that some objects from the ANTARES list are within the error circles of few IceCube events, the statistical analysis shows that none of these sources have a significant correlation.Comment: Latex file, 6 pages, two columns, 1 Figur

Very high-energy gamma-ray signature of ultrahigh-energy cosmic-ray acceleration in Centaurus A

The association of at least a dozen ultrahigh-energy cosmic-ray (UHECR) events with energy $\gtrsim 55$ EeV detected by the Pierre Auger Observatory (PAO) from the direction of Centaurus-A, the nearest radio galaxy, supports the scenario of UHECR acceleration in the jets of radio galaxies. In this work, we model radio to very high energy (VHE,$\gtrsim 100$ \rm GeV) $\gamma$-ray emission from Cen A, including GeV hardness detected by Fermi-LAT and TeV emission detected by HESS. We consider two scenarios: (i) Two zone synchrotron self-Compton (SSC) and external-Compton (EC) models, (ii) Two zone SSC, EC and photo-hadronic emission from cosmic ray interactions. The GeV hardness observed by Fermi-LAT can be explained using these two scenarios, where zone 2 EC emission is very important. Hadronic emission in scenario (ii) can explain VHE data with the same spectral slope as obtained through fitting UHECRs from Cen A. The peak luminosity in cosmic ray proton at 1 TeV, to explain the VHE $\gamma$-ray data is $\approx 2.5 \times 10^{46}$ erg/s. The bolometric luminosity in cosmic ray protons is consistent with the luminosity required to explain the origin of 13 UHECR signal events that are correlated with Cen A.Comment: 6 pages, 3 figures, Accepted for publication in MNRASL, Comments welcom

Revisiting constraints on 3+1 active-sterile neutrino mixing using IceCube data

Recent IceCube search results for sterile neutrino increased tension between the combined appearance and disappearance experiments. On the other hand, MiniBooNE latest data confirms at $4.9\sigma$ CL the short-baseline oscillation anomaly. We analyze published IceCube data based on two different active-sterile mixing schemes using one additional sterile neutrino flavor. We present exclusion regions in the parameter ranges $0.01 \le \sin^2 \theta_{24} \le 0.1$ and $0.1~{\rm eV}^2 \le \Delta m^2_{42} \le 10~{\rm eV}^2$ for the mass-mixing and flavor-mixing schemes. Under the more conservative mass-mixing scheme, $3\sigma$ CL allowed regions for the appearance experiment and MiniBooNE latest result are excluded at $\gtrsim 3\sigma$ CL. In case of less-restrictive flavor-mixing scheme, results from the appearance experiments are excluded at $\gtrsim 2\sigma$ CL. We also find that including prompt component of the atmospheric neutrino flux relaxes constraints on sterile mixing for $\Delta m^2_{42} \gtrsim 1~{\rm eV}^2$.Comment: 15 pages and 5 figures. Accepted for publication in JHE

Searching for non-unitary neutrino oscillations in the present T2K and NOν\nuA data

The mixing of three active neutrino flavors is parameterized by the unitary PMNS matrix. If there are more than three neutrino flavors and if the extra generations are heavy isosinglets, the effective $3\times 3$ mixing matrix for the three active neutrinos will be non-unitary. We have analyzed the latest T2K and \nova data with the hypothesis of non-unitary mixing of the active neutrinos. We found that the 2019 NO$\nu$A data slightly (at $\sim 1\, \sigma$ C.L.) prefer the non-unitary mixing over unitary mixing. In fact, allowing the non-unitary mixing brings the \nova best-fit point in the $\sin^2\theta_{23}-\delta_{CP}$ plane closer to the T2K best-fit point. The 2019 T2K data, on the other hand, cannot rule out any of the two mixing schemes. A combined analysis of the NO$\nu$A and T2K 2019 data prefers the non-unitary mixing at $1\, \sigma$ C.L.. We derive constraints on the non-unitary mixing parameters using the best-fit to the combined NO$\nu$A and T2K data. These constraints are weaker than previously found. The latest 2020 data from both the experiments prefer non-unitarity over unitary mixing at $1\, \sigma$ C.L. The combined analysis preferes non-unitarity at $2\, \sigma$ C.L. The stronger tension, which exists between the latest 2020 data of the two experiments, also gets reduced with non-unitary analysis.Comment: 30 pages, 19 figures, 3 tables. Results for 2020 data from NOvA and T2K have been include

Programa de prácticas de bacteriología y micología

Conocer e identificar la morfología bacteriana y fungal, así como sus principios metabólicos, genéticos y taxonómicos

Hepatocyte Growth Factor Reduces Free Cholesterol-Mediated Lipotoxicity in Primary Hepatocytes by Countering Oxidative Stress

Cholesterol overload in the liver has shown toxic effects by inducing the aggravation of nonalcoholic fatty liver disease to steatohepatitis and sensitizing to damage. Although the mechanism of damage is complex, it has been demonstrated that oxidative stress plays a prominent role in the process. In addition, we have proved that hepatocyte growth factor induces an antioxidant response in hepatic cells; in the present work we aimed to figure out the protective effect of this growth factor in hepatocytes overloaded with free cholesterol. Hepatocytes from mice fed with a high-cholesterol diet were treated or not with HGF, reactive oxygen species present in cholesterol overloaded hepatocytes significantly decreased, and this effect was particularly associated with the increase in glutathione and related enzymes, such as γ-gamma glutamyl cysteine synthetase, GSH peroxidase, and GSH-S-transferase. Our data clearly indicate that HGF displays an antioxidant response by inducing the glutathione-related protection system