108,891 research outputs found
Inverse Compton model of pulsar high energy emission
We reproduce the broadband spectrum of Crab pulsar, from UV to very high
energy gamma-rays - nearly ten decades in energy, within the framework of the
cyclotron-self-Compton model. Emission is produced by two counter-streaming
beams within the outer gaps, at distances above 20 NS radii. The outward
moving beam produces UV--ray photons via Doppler-booster cyclotron emission,
and GeV photons by Compton scattering the cyclotron photons produced by the
inward going beam. The scattering occurs in the deep Klein-Nishina regime,
whereby the IC component provides a direct measurement of particle distribution
within the magnetosphere. The required plasma multiplicity is high, , but is consistent with the average particle flux injected into the
pulsar wind nebula.
The importance of Compton scattering in the Klein-Nishina regime also implies
the importance of pair production in the outer gaps. We suggest that outer gaps
are important sources of pairs in pulsar magnetospheres.
Cyclotron motion of particles in the pulsar magnetosphere may be excited due
to coherent emission of radio waves by streaming particles at the anomalous
cyclotron resonance. Thus, a whole range of Crab non-thermal emission, from
coherent radio waves to very high energy -rays - nearly eighteen
decades in energy - may be a manifestation of inter-dependent radiation
processes.
The present model, together with the observational evidence in favor of the
IC scattering (Lyutikov et al. 2012; Lyutikov 2012), demonstrates that the
inverse Compton scattering can be the dominant high energy emission mechanism
in majority of pulsars.Comment: 20 pages, 4 figure
Overview on jet results from STAR
Full jet reconstruction allows access to the parton kinematics over a large
energy domain and can be used to constrain the mechanisms of energy loss in
heavy-ion collisions. Such measurements are challenging at RHIC, due to the
high-multiplicity environments created in heavy-ion collisions. In these
proceedings, we report an overview of the results on full jet reconstruction
obtained by the STAR experiment. Jet measurements in 200 GeV p+p show that jets
are calibrated pQCD probes and provide a baseline for jet measurements in Au+Au
collisions. Inclusive differential jet production cross sections and ratios are
reported for central 200 GeV Au+Au collisions and compared to p+p. We also
present measurements of fully reconstructed di-jets at mid-rapidity, and
compare spectra and fragmentation functions in p+p and central Au+Au
collisions.Comment: Proceedings for the 26th WWND conferenc
VERITAS Observations of M 87 in 2011/2012
The giant radio galaxy M 87 is located at a distance of 16.7 Mpc and harbors
a super-massive black hole (6 billion solar masses) in its center. M 87 is one
of just three radio galaxies known to emit TeV gamma-rays. The structure of its
relativistic plasma jet, which is not pointing towards our line of sight, is
spatially resolved in X-ray (Chandra), optical and radio (VLA/VLBA)
observations. The mechanism and location of the TeV emitting region is one of
the least understood aspects of AGN. In spring 2008 and 2010, the three TeV
observatories VERITAS, MAGIC and H.E.S.S. detected two major TeV flares in
coordinated observations. Simultaneous high-resolution observations at other
wavelengths - radio (2008) and X-rays (2008/2010) - gave evidence that one of
the TeV flares was related to an event in the core region; however, no
common/repeated patterns could be identified so far. VERITAS continued to
monitor M 87 in 2011/2012. The results of these observations are presented.Comment: 4 pages, 3 figures; conference proceedings of the 5th International
Symposium on High-Energy Gamma-Ray Astronomy (Gamma2012
Light hadrons in 2+1 flavor lattice QCD
This talk will focus on recent results by the MILC collaboration from
simulations of light hadrons in 2+1 flavor lattice QCD. We have achieved high
precision results in the pseudoscalar sector, including masses and decay
constants, plus quark masses and Gasser-Leutwyler parameters from well
controlled chiral perturbation theory fits to our data. We also show
spectroscopy results for vector mesons and baryons.Comment: To appear in the proceedings of the First Meeting of the APS Topical
Group on Hadronic Physics, Fermilab, Batavia, Illinois, Oct. 24-26, 200
Reforms: A Quest for Efficiency or an Opportunity for Vested Interests'? A Case Study of Pharmaceutical Policy Reforms in Tanzania.
Regulation of the pharmaceutical sector is a challenging task for most governments in the developing countries. In Tanzania, this task falls under the Food and Drugs Authority and the Pharmacy Council. In 2010, the Pharmacy Council spearheaded policy reforms in the pharmaceutical sector aimed at taking over the control of the regulation of the business of pharmacy from the Tanzania Food and Drugs Authority. This study provides a critical analysis of these reforms. The study employed a qualitative case-study design. Data was collected through in-depth interviews, focus group discussions and document reviews. Data was analyzed thematically using a policy triangle framework. The analysis was done manually. The reforms adopted an incremental model of public policy-making and the process was characterized by lobbying for political support, negotiations and bargaining between the interest groups. These negotiations were largely centred on vested interests and not on the impact of the reforms on the efficiency of pharmaceutical regulations in the country. Stakeholders from the micro and meso levels were minimally involved in the policy reforms. Recent pharmaceutical regulation reforms in Tanzania were overshadowed by vested interests, displacing a critical analysis of optimal policy options that have the potential to increase efficiency in the regulation of the business of pharmacy. Politics influenced decision-making at different levels of the reform process
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